Chevrolet - C Tahoe 2wd - Workshop Manual - 1996 - 1996

Factory Workshop Manual Make Chevrolet Model C Tahoe 2wd Engine and year V8-5.7L VIN R (1996) Please navigate through the PDF using the options provided by OnlyManuals.com on the sidebar. This manual was submitted by Anonymous Date 1st January 2018 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Accessories and Optional Equipment > Emergency Contact Module > Component Information > Technical Service Bulletins > OnStar(R) - Analog Only Systems Information Emergency Contact Module: Technical Service Bulletins OnStar(R) - Analog Only Systems Information INFORMATION Bulletin No.: 06-08-64-007A Date: September 22, 2008 Subject: Information on OnStar(R) Analog-Only Systems Models Supercede: This bulletin is being revised to update the models affected list above. Please discard Corporate Bulletin Number 06-08-46-007 (Section 08 - Body & Accessories). All vehicles equipped with OnStar(R) listed in this bulletin were built with Analog-Only OnStar(R) Hardware. OnStar(R) equipped vehicles with analog-only equipment were designed to operate only on the analog wireless network and cannot be upgraded for digital network compatibility. Vehicles with this equipment will no longer be able to receive OnStar(R) services beginning January 1, 2008. At that time, service will be available only through Dual-Mode (Analog / Digital) equipment. Analog-Only vehicles cannot be upgraded to digital equipment. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Accessories and Optional Equipment > Emergency Contact Module > Component Information > Technical Service Bulletins > OnStar(R) - Analog Only Systems Information > Page 8 Emergency Contact Module: Technical Service Bulletins OnStar(R) - Aftermarket Device Interference Information INFORMATION Bulletin No.: 08-08-46-004 Date: August 14, 2008 Subject: Information on Aftermarket Device Interference with OnStar(R) Diagnostic Services Models: 2009 and Prior GM Passenger Car and Truck (including Saturn) 2009 and Prior HUMMER H2, H3 Models 2009 and Prior Saab 9-7X with OnStar(R) (RPO UE1) This bulletin is being issued to provide dealer service personnel with information regarding aftermarket devices connected to the Diagnostic Link Connector (DLC) and the impact to OnStar(R) diagnostic probes and Vehicle Diagnostic e-mails. Certain aftermarket devices, when connected to the Diagnostic Link Connector, such as, but not limited to, Scan Tools, Trip Computers, Fuel Economy Analyzers and Insurance Tracking Devices, interfere with OnStar's ability to perform a diagnostic probe when requested (via a blue button call) by a subscriber. These devices also prohibit the ability to gather diagnostic and tire pressure data for a subscriber's scheduled OnStar(R) Vehicle Diagnostic (OVD) e-mail. These aftermarket devices utilize the Vehicles serial data bus to perform data requests and/or information gathering. When these devices are requesting data, OnStar(R) is designed not to interfere with any data request being made by these devices as required by OBD II regulations. The OnStar(R) advisor is unable to definitively detect the presence of these devices and will only be able to inform the caller or requester of the unsuccessful or incomplete probe and may in some cases refer the subscriber/requester to take the vehicle to a dealer for diagnosis of the concern. When performing a diagnostic check for an unsuccessful or incomplete OnStar(R) diagnostic probe, or for concerns regarding completeness of the OnStar(R) Vehicle Diagnostic (OVD) e-mail, verify that an aftermarket device was not present at the time of the requested probe. Regarding the OVD e-mail, if an aftermarket device is interfering (including a Scan Tool of any type), the e-mail will consistently display a "yellow" indication in diagnostics section for all vehicle systems except the OnStar(R) System and Tire Pressure data (not available on all vehicles) will not be displayed (i.e. section is collapsed). Successful diagnostic probes and complete OVD e-mails will resume following the removal or disconnecting of the off-board device. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Accessories and Optional Equipment > Emergency Contact Module > Component Information > Technical Service Bulletins > OnStar(R) - Analog Only Systems Information > Page 9 Emergency Contact Module: Technical Service Bulletins OnStar - Analog-Only Systems Information Bulletin No.: 06-08-46-007 Date: December 13, 2006 INFORMATION Subject: Information on OnStar(R) Analog-Only Systems Models: 1996-2001 GM Passenger Cars and Trucks Plus: 2002 Buick LeSabre, Rendezvous 2002-2003 Buick Century, Regal 2002-2005 Buick Park Avenue 2002 Cadillac Eldorado, Escalade Models 2002 Chevrolet Avalanche, Silverado, Suburban, Tahoe, Venture 2002 GMC Denali, Denali XL, Jimmy, Sierra, Yukon, Yukon XL 2002 Oldsmobile Intrigue, Silhouette 2002-2003 Oldsmobile Aurora 2002 Pontiac Aztek, Bonneville, Montana 2002-2003 Pontiac Grand Prix with OnStar(R) (RPO UE1) All vehicles equipped with OnStar(R) listed in this bulletin were built with Analog-Only OnStar(R) Hardware. OnStar(R) equipped vehicles with analog-only equipment were designed to operate only on the analog wireless network and cannot be upgraded for digital network compatibility. Vehicles with this equipment will no longer be able to receive OnStar(R) services beginning January 1, 2008. At that time, service will be available only through Dual-Mode (Analog/Digital) equipment. Analog-Only vehicles cannot be upgraded to digital equipment. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > Customer Interest for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules Relay Module: Customer Interest Electrical - MIL ON/DTC's Set By Various Control Modules TECHNICAL Bulletin No.: 09-06-03-004D Date: December 08, 2010 Subject: Intermittent No Crank/No Start, No Module Communication, MIL, Warning Lights, Vehicle Messages or DTCs Set by Various Control Modules - Diagnosing and Repairing Fretting Corrosion (Disconnect Affected Connector and Apply Dielectric Lubricant) Models: 2011 and Prior GM Passenger Cars and Trucks Attention: This repair can be applied to ANY electrical connection including, but not limited to: lighting, body electrical, in-line connections, powertrain control sensors, etc. DO NOT over apply lubricant to the point where it prevents the full engagement of sealed connectors. A light coating on the terminal surfaces is sufficient to correct the condition. Supercede: This bulletin is being revised to update the Attention statement and add the 2011 model year. Please discard Corporate Bulletin Number 09-06-03-004C (Section 06 Engine/Propulsion System). Condition Some customers may comment on any of the following conditions: - An intermittent no crank/no start - Intermittent malfunction indicator lamp (MIL) illumination - Intermittent service lamp illumination - Intermittent service message(s) being displayed The technician may determine that he is unable to duplicate the intermittent condition. Cause This condition may be caused by a buildup of nonconductive insulating oxidized debris known as fretting corrosion, occurring between two electrical contact surfaces of the connection or connector. This may be caused by any of the following conditions: - Vibration - Thermal cycling - Poor connection/terminal retention - Micro motion - A connector, component or wiring harness not properly secured resulting in movement On low current signal circuits this condition may cause high resistance, resulting in intermittent connections. On high current power circuits this condition may cause permanent increases in the resistance and may cause a device to become inoperative. Representative List of Control Modules and Components The following is only a representative list of control modules and components that may be affected by this connection or connector condition and DOES NOT include every possible module or component for every vehicle. - Blower Control Module - Body Control Module (BCM) - Communication Interface Module (CIM) - Cooling Fan Control Module - Electronic Brake Control Module (EBCM) - Electronic Brake and Traction Control Module (EBTCM) - Electronic Suspension Control (ESC) Module - Engine Control Module (ECM) - Heating, Ventilation and Air Conditioning (HVAC) Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > Customer Interest for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 18 - HVAC Actuator - Inflatable Restraint Sensing and Diagnostic Module (SDM) - Any AIR BAG module - Seatbelt Lap Anchor Pretensioner - Seatbelt Retractor Pretensioner - An SIR system connection or connector condition resulting in the following DTCs being set: B0015, B0016, B0019, B0020, B0022, or B0023 - Powertrain Control Module (PCM) - Remote Control Door Lock Receiver (RCDLR) - Transmission Control Module (TCM) Correction Important DO NOT replace the control module, wiring or component for the following conditions: - The condition is intermittent and cannot be duplicated. - The condition is present and by disconnecting and reconnecting the connector the condition can no longer be duplicated. Use the following procedure to correct the conditions listed above. 1. Install a scan tool and perform the Diagnostic System Check - Vehicle. Retrieve and record any existing history or current DTCs from all of the control modules (refer to SI). ‹› If any DTC(s) are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). ‹› If DTCs are not set, refer to Symptoms - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). 2. When identified, use the appropriate DTC Diagnostics, Symptoms, Schematics, Component Connector End Views and Component Locator documents to locate and disconnect the affected harness connector(s) which are causing the condition. Note Fretting corrosion looks like little dark smudges on electrical terminals and appear where the actual electrical contact is being made. In less severe cases it may be unable to be seen or identified without the use of a magnifying glass. Important DO NOT apply an excessive amount of dielectric lubricant to the connectors as shown, as hydrolock may result when attempting to mate the connectors. Use ONLY a clean nylon brush that is dedicated to the repair of the conditions in this bulletin. 3. With a one-inch nylon bristle brush, apply dielectric lubricant to both the module/component side and the harness side of the affected connector(s). 4. Reconnect the affected connector(s) and wipe away any excess lubricant that may be present. 5. Attempt to duplicate the condition by using the following information: - DTC Diagnostic Procedure - Circuit/System Description - Conditions for Running the DTC - Conditions for Setting the DTC - Diagnostic Aids - Circuit/System Verification ‹› If the condition cannot be duplicated, the repair is complete. ‹› If the condition can be duplicated, then follow the appropriate DTC, Symptom or Circuit/System Testing procedure (refer to SI). Repair Order Documentation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > Customer Interest for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 19 Important The following information MUST be documented on the repair order. Failure to do so may result in a chargeback. - Customer vehicle condition. - Was a Service Lamp or Service Message illuminated? If yes, specify which Service Lamp or Service Message. - Was a DTC(s) set? If yes, specify which DTC(s) were set. - After following the procedure contained within this bulletin, could the condition be duplicated? ‹› If the condition was not duplicated, then document the affected module/component connector name and number on the repair order. - If the condition was duplicated after the procedure contained within this bulletin was followed, and additional diagnosis led to the replacement of a module or component, the SI Document ID Number MUST be written on the repair order. Parts Information Alternate Distributor For All of North America Note NyoGel(R) 760G Lubricant* is equivalent to GMSPO P/N 12377900, and P/N 10953529 (Canada), specified for use to correct the condition in this bulletin. *We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for, or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > Customer Interest for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 20 For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to refer to the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules Relay Module: All Technical Service Bulletins Electrical - MIL ON/DTC's Set By Various Control Modules TECHNICAL Bulletin No.: 09-06-03-004D Date: December 08, 2010 Subject: Intermittent No Crank/No Start, No Module Communication, MIL, Warning Lights, Vehicle Messages or DTCs Set by Various Control Modules - Diagnosing and Repairing Fretting Corrosion (Disconnect Affected Connector and Apply Dielectric Lubricant) Models: 2011 and Prior GM Passenger Cars and Trucks Attention: This repair can be applied to ANY electrical connection including, but not limited to: lighting, body electrical, in-line connections, powertrain control sensors, etc. DO NOT over apply lubricant to the point where it prevents the full engagement of sealed connectors. A light coating on the terminal surfaces is sufficient to correct the condition. Supercede: This bulletin is being revised to update the Attention statement and add the 2011 model year. Please discard Corporate Bulletin Number 09-06-03-004C (Section 06 Engine/Propulsion System). Condition Some customers may comment on any of the following conditions: - An intermittent no crank/no start - Intermittent malfunction indicator lamp (MIL) illumination - Intermittent service lamp illumination - Intermittent service message(s) being displayed The technician may determine that he is unable to duplicate the intermittent condition. Cause This condition may be caused by a buildup of nonconductive insulating oxidized debris known as fretting corrosion, occurring between two electrical contact surfaces of the connection or connector. This may be caused by any of the following conditions: - Vibration - Thermal cycling - Poor connection/terminal retention - Micro motion - A connector, component or wiring harness not properly secured resulting in movement On low current signal circuits this condition may cause high resistance, resulting in intermittent connections. On high current power circuits this condition may cause permanent increases in the resistance and may cause a device to become inoperative. Representative List of Control Modules and Components The following is only a representative list of control modules and components that may be affected by this connection or connector condition and DOES NOT include every possible module or component for every vehicle. - Blower Control Module - Body Control Module (BCM) - Communication Interface Module (CIM) - Cooling Fan Control Module - Electronic Brake Control Module (EBCM) - Electronic Brake and Traction Control Module (EBTCM) - Electronic Suspension Control (ESC) Module - Engine Control Module (ECM) - Heating, Ventilation and Air Conditioning (HVAC) Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 26 - HVAC Actuator - Inflatable Restraint Sensing and Diagnostic Module (SDM) - Any AIR BAG module - Seatbelt Lap Anchor Pretensioner - Seatbelt Retractor Pretensioner - An SIR system connection or connector condition resulting in the following DTCs being set: B0015, B0016, B0019, B0020, B0022, or B0023 - Powertrain Control Module (PCM) - Remote Control Door Lock Receiver (RCDLR) - Transmission Control Module (TCM) Correction Important DO NOT replace the control module, wiring or component for the following conditions: - The condition is intermittent and cannot be duplicated. - The condition is present and by disconnecting and reconnecting the connector the condition can no longer be duplicated. Use the following procedure to correct the conditions listed above. 1. Install a scan tool and perform the Diagnostic System Check - Vehicle. Retrieve and record any existing history or current DTCs from all of the control modules (refer to SI). ‹› If any DTC(s) are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). ‹› If DTCs are not set, refer to Symptoms - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). 2. When identified, use the appropriate DTC Diagnostics, Symptoms, Schematics, Component Connector End Views and Component Locator documents to locate and disconnect the affected harness connector(s) which are causing the condition. Note Fretting corrosion looks like little dark smudges on electrical terminals and appear where the actual electrical contact is being made. In less severe cases it may be unable to be seen or identified without the use of a magnifying glass. Important DO NOT apply an excessive amount of dielectric lubricant to the connectors as shown, as hydrolock may result when attempting to mate the connectors. Use ONLY a clean nylon brush that is dedicated to the repair of the conditions in this bulletin. 3. With a one-inch nylon bristle brush, apply dielectric lubricant to both the module/component side and the harness side of the affected connector(s). 4. Reconnect the affected connector(s) and wipe away any excess lubricant that may be present. 5. Attempt to duplicate the condition by using the following information: - DTC Diagnostic Procedure - Circuit/System Description - Conditions for Running the DTC - Conditions for Setting the DTC - Diagnostic Aids - Circuit/System Verification ‹› If the condition cannot be duplicated, the repair is complete. ‹› If the condition can be duplicated, then follow the appropriate DTC, Symptom or Circuit/System Testing procedure (refer to SI). Repair Order Documentation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 27 Important The following information MUST be documented on the repair order. Failure to do so may result in a chargeback. - Customer vehicle condition. - Was a Service Lamp or Service Message illuminated? If yes, specify which Service Lamp or Service Message. - Was a DTC(s) set? If yes, specify which DTC(s) were set. - After following the procedure contained within this bulletin, could the condition be duplicated? ‹› If the condition was not duplicated, then document the affected module/component connector name and number on the repair order. - If the condition was duplicated after the procedure contained within this bulletin was followed, and additional diagnosis led to the replacement of a module or component, the SI Document ID Number MUST be written on the repair order. Parts Information Alternate Distributor For All of North America Note NyoGel(R) 760G Lubricant* is equivalent to GMSPO P/N 12377900, and P/N 10953529 (Canada), specified for use to correct the condition in this bulletin. *We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for, or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 28 For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to refer to the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Body and Frame > Power Door Lock Relay > Component Information > Locations Power Door Lock Relay: Locations POWER DOOR LOCK RELAY Power Door Lock Relay The Power Door Lock Relay is located under the center portion of Instrument panel (I/P), near Remote Control Door Lock Receiver (RCDLR). NOTE: This relay is used only on 4 Door and 2 Door Utility, Crew Cab/Suburban. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Body and Frame > Power Door Lock Relay > Component Information > Locations > Page 33 Door Lock Relay Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Brakes and Traction Control > ABS Main Relay > Component Information > Locations ABS Main Relay: Locations The relay is located inside the Brake Pressure Modulator Valve (BPMV) and cannot be serviced. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Brakes and Traction Control > Electronic Brake Control Module > Component Information > Locations Electronic Brake Control Module: Locations The Electronic Brake Control Unit (EBCM) is mounted to the top of the Brake Pressure Modulator Valve (BPMV) and is housed in aluminum with a black plastic top. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Brakes and Traction Control > Electronic Brake Control Module > Component Information > Locations > Page 41 Electronic Brake Control Module: Service and Repair Fig. 226 EBCM Replacement. 1. Disconnect battery ground cable, then raise and support vehicle. 2. Remove bolts securing shield (if equipped) and BPMV to EHCU mounting bracket, Fig. 226, then disconnect (EBCM) Electronic Brake Control Module electrical connectors. 3. Remove Torx bolts securing EBCM to BPMV, then separate EBCM from BPMV. Do not pry on components to separate. 4. Reverse procedure to install, noting the following: a. Install a new EBCM gasket and mounting bolts. Do not use any gasket sealant. b. Torque EBCM to BPMV bolts to 39 inch lbs. in a crisscross pattern. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cooling System > Radiator Cooling Fan Motor Relay > Component Information > Locations Underhood Fuse-Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Locations Cruise Control Module: Locations Cruise Control Module Vehicle Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions Cruise Control Module: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 52 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 53 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 54 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 55 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 56 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 57 Cruise Control Module: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 58 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 59 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 60 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 61 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 62 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 63 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 64 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 65 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 66 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 67 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 68 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 69 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 70 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 71 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 72 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 73 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 74 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 75 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 76 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 77 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 78 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 79 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 80 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 81 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 82 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 83 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 84 Cruise Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Description and Operation > Cruise Control Module Cruise Control Module: Description and Operation Cruise Control Module Fig. 1 Cruise Control Module. The cruise control module is mounted near the master cylinder on the engine side of the cowl. The module houses an electronic controller and an electric motor. Together, these components vary throttle position in response to cruise control mode selection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Description and Operation > Page 87 Cruise Control Module: Service and Repair Fig. 15 Cruise control module & cable replacement 1. Disconnect battery ground cable. 2. Disconnect cruise control cable from module, Fig. 15. 3. Remove module attaching screws, then disconnect electrical connector and remove module. The module cannot be serviced. 4. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - HVAC > Blower Motor Relay > Component Information > Locations > Blower Motor Relay High Front Blower Motor Relay: Locations Blower Motor Relay High Front Behind I/P Compartment Box on HVAC Plenum Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - HVAC > Blower Motor Relay > Component Information > Locations > Blower Motor Relay High Front > Page 93 Blower Motor Relay: Locations Blower Relay High Heater And Air Conditioning Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - HVAC > Blower Motor Relay > Component Information > Locations > Blower Motor Relay High Front > Page 94 Auxiliary Heater And Air Conditioning Wiring, Rear Under I/P, on top of HVAC Plenum Auxiliary Heater And Air Conditioning Wiring, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - HVAC > Blower Motor Relay > Component Information > Locations > Blower Motor Relay High Front > Page 95 Auxiliary Heater And Air Conditioning Wiring, Rear Medium Rear On Auxiliary Heater and A/C Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - HVAC > Blower Motor Relay > Component Information > Locations > Page 96 High Blower Relay Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - HVAC > Blower Motor Relay > Component Information > Locations > Page 97 Blower Motor Relay: Service and Repair 1 Screw, 2 Resistor, 3 Relay Bracket, 4 Relay Remove or Disconnect 1. Negative battery cable. 2. Instrument panel compartment. 3. Electrical connectors, as necessary. 4. Relay from relay bracket. Install or Connect 1. Relay to relay bracket. 2. Electrical connectors, as necessary. 3. Instrument panel compartment. 4. Negative battery cable. - Check circuit operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - HVAC > Compressor Clutch Relay > Component Information > Locations Underhood Fuse-Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - HVAC > Control Module HVAC > Component Information > Locations > Auxiliary System Control Module HVAC: Locations Auxiliary System Overhead Console Auxiliary Heater and A/C Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - HVAC > Control Module HVAC > Component Information > Locations > Auxiliary System > Page 105 Overhead Console Control Modules are attached to Control Assemblies. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - HVAC > Control Module HVAC > Component Information > Locations > Auxiliary System > Page 106 Control Module HVAC: Locations Blower Control Module HVAC Control Panel & Module Control Module is attached to Control Assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Instrument Panel > Audible Warning Device Control Module > Component Information > Locations Convenience Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Lighting and Horns > Brake Lamp Relay > Component Information > Locations Brake Lamp Relay: Locations Underhood Fuse-Relay Center In Underhood Fuse-Relay Center. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Lighting and Horns > Daytime Running Lamp Control Unit > Component Information > Locations Daytime Running Lamp Control Unit: Locations This article has been updated with Bulletin No.: 76-81-06. DAYTIME RUNNING LAMPS (DRL) MODULE The Daytime Running Lamps (DRL) Module is located under LH side of Instrument Panel (I/P), taped on I/P harness. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Lighting and Horns > Daytime Running Lamp Control Unit > Component Information > Locations > Page 118 DRL Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Lighting and Horns > Daytime Running Lamp Relay > Component Information > Locations Convenience Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Lighting and Horns > Daytime Running Lamp Relay > Component Information > Locations > Page 122 Daytime Running Lamp Relay: Diagrams Convenience Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Lighting and Horns > Daytime Running Lamp Relay > Component Information > Locations > Page 123 Convenience Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Lighting and Horns > Fog/Driving Lamp Relay > Component Information > Locations Convenience Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Lighting and Horns > Horn Relay > Component Information > Locations Underhood Fuse-Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Lighting and Horns > Interior Lighting Module > Component Information > Locations Interior Lighting Module: Locations View: Under Center Of Instrument Panel Interior Lamp Control Module, Remote Control Door Lock Receiver Manufacturer supplied 2 different possible locations. Look for 5 wire connector with wire colors: gray, white, orange, pink & black. #PIT3819: Location of Interior Lamp Control Module - keywords control dim dome electrical entry ground illumination inoperative keyless lens light remort resistor RKE short - (Dec 23, 2005) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Lighting and Horns > Interior Lighting Module > Component Information > Locations > Page 133 Subject: Location of Interior Lamp Control Module. Models: 1995-2000 Chevrolet C/K Trucks, Suburban and Tahoe 1995-2000 GMC Yukon and C/K Trucks Classic Body Style Only The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this P1. Condition/Concern When diagnosing a dome lamp concern on one of the vehicles listed above, you may be unable to locate the Interior Lamp Control Module that is called out in the Service Manual. Recommendation/lnstructions: Only vehicles without Remote Keyless Entry (RPO AUO) will be equipped with a Interior Lamp Control Module. If the vehicle is equipped with (RKE) Remote Keyless Entry, the illumination module is a internal part of RKE Module. Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Lighting and Horns > Interior Lighting Module > Component Information > Locations > Page 134 Interior Lamp Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Electrical - Revised Convenience Center Cavity ID Relay Box: Technical Service Bulletins Electrical - Revised Convenience Center Cavity ID File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-82-08 Date: August, 1997 SERVICE MANUAL UPDATE Subject: Section 8A-11 Fuse Block Details Revised Convenience Center Table Models: 1996-98 Chevrolet and GMC C/K models. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Electrical - Revised Convenience Center Cavity ID > Page 140 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Electrical - Revised Convenience Center Cavity ID > Page 141 This bulletin revises "Convenience Center" table on Page 8A-11-5, 6 in the 1996 C/K Service Manual, Page 8A-11-6, 7 in the 1997 C/K Service Manual, and Page 8A-11-5 in the 1998 C/K Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Page 142 Underhood Fuse-Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Page 143 Relay Box: Application and ID Underhood Fuse-Relay Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Page 144 Underhood Fuse-Relay Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > Customer Interest: > 77-71-53 > Apr > 97 > A/T - Chuggle/Surge on TCC Apply/No DTC's Engine Control Module: Customer Interest A/T - Chuggle/Surge on TCC Apply/No DTC's File In Section: 7 - Transmission Bulletin No.: 77-71-53 Date: April, 1997 Subject: Chuggle/Surge on TCC Apply/No DTC's (Reflash PCM) Models: 1996-97 Chevrolet and GMC C/K, G Models with 5.7L Engine (VIN R - RPO L31) and HYDRA-MATIC 4L60-E Transmission (RPO M30) Condition Some owners of the above models may experience a chuggle/surge when TCC is applied under light throttle acceleration. Cause Engine inputs (Combustion events) exciting the vehicle platform/driveline or tire balance may be a contributing factor. Correction First ensure the most recent engine, not transmission calibration has been installed (Corp. # 76-65-04) and check tire balance. A new transmission calibration to correct chuggle/surge is available for use on vehicles with persistent concerns only. Important: This calibration will raise TCC engagement approximately 7-10 mph depending on application. This calibration should not be installed until the engine calibration listed above has been installed. Installation of this calibration may lead to decreased fuel economy due to TCC engagement at higher speeds. Reflash the Powertrain Control Module with the appropriate part numbers below. Refer to your Service Manual for proper procedure. Parts Information This new calibration will be available starting with the 1997 Disc 4 update. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J6355 Reflash Control Module Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 04-06-04-054B > Nov > 10 > Engine Controls - Aftermarket Accessory Usage Engine Control Module: All Technical Service Bulletins Engine Controls - Aftermarket Accessory Usage INFORMATION Bulletin No.: 04-06-04-054B Date: November 18, 2010 Subject: Info - Non-GM Parts and Accessories (Aftermarket) Models: 2011 and Prior GM Passenger Cars and Trucks Supercede: This bulletin is being revised to add model years and update to the new U.S. Fixed Operation Manager (FOM) and Canada Warranty Manager (WM) names. Please discard Corporate Bulletin Number 04-06-04-054A (Section 06 - Engine/Propulsion System). The recent rise and expansion of companies selling non-GM parts and accessories has made it necessary to issue this reminder to dealers regarding GM's policy on the use and installation of these aftermarket components. When a dealer is performing a repair under the New Vehicle Limited Warranty, they are required to use only genuine GM or GM-approved parts and accessories. This applies to all warranty repairs, special policy repairs or any repairs paid for by GM. Parts and accessories advertised as being "the same" as parts manufactured by GM, but not sold through GM, do not qualify for use in warranty repairs, special policy repairs or any repairs paid for by GM. During a warranty repair, if a GM original equipment part is not available through GM Customer Care and Aftersales (GM CC&A;), ACDelco(R) distributors, other GM dealers or approved sources, the dealer is to obtain comparable, non-GM parts and clearly indicate, in detail, on the repair order the circumstances surrounding why non-GM parts were used. The dealer must give customers written notice, prior to the sale or service, that such parts or accessories are not marketed or warranted by General Motors. It should also be noted that dealers modifying new vehicles and installing equipment, parts and accessories obtained from sources not authorized by GM are responsible for complying with the National Traffic and Motor Vehicle Safety Act. Certain non-approved parts or assemblies, installed by the dealer or its agent not authorized by GM, may result in a change to the vehicle's design characteristics and may affect the vehicle's ability to conform to federal law. Dealers must fully understand that non-GM approved parts may not have been validated, tested or certified for use. This puts the dealer at risk for potential liability in the event of a part or vehicle failure. If a GM part failure occurs as the result of the installation or use of a non-GM approved part, the warranty will not be honored. A good example of non-authorized modification of vehicles is the result of an ever increasing supply of aftermarket devices available to the customer, which claim to increase the horsepower and torque of the Duramax(TM) Diesel Engines. These include the addition of, but are not limited to one or more of the following modifications: - Propane injection - Nitrous oxide injection - Additional modules (black boxes) that connect to the vehicle wiring systems - Revised engine calibrations downloaded for the engine control module - Calibration modules which connect to the vehicle diagnostic connector - Modification to the engine turbocharger waste gate Although the installation of these devices, or modification of vehicle components, can increase engine horsepower and torque, they may also negatively affect the engine emissions, reliability and/or durability. In addition, other powertrain components, such as transmissions, universal joints, drive shafts, and front/rear axle components, can be stressed beyond design safety limits by the installation of these devices. General Motors does not support or endorse the use of devices or modifications that, when installed, increase the engine horsepower and torque. It is because of these unknown stresses, and the potential to alter reliability, durability and emissions performance, that GM has adopted a policy that prevents any UNAUTHORIZED dealer warranty claim submissions to any remaining warranty coverage, to the powertrain and driveline components whenever the presence of a non-GM (aftermarket) calibration is confirmed - even if the non-GM control module calibration is subsequently removed. Refer to the latest version of Bulletin 09-06-04-026 (V8 Gas Engines) or 06-06-01-007 (Duramax(TM) Diesel Engines) for more information on dealer requirements for calibration verification. These same policies apply as they relate to the use of non-GM accessories. Damage or failure from the use or installation of a non-GM accessory will not be covered under warranty. Failure resulting from the alteration or modification of the vehicle, including the cutting, welding or disconnecting of the vehicle's original equipment parts and components will void the warranty. Additionally, dealers will NOT be reimbursed or compensated by GM in the event of any legal inquiry at either the local, state or federal level that Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 04-06-04-054B > Nov > 10 > Engine Controls - Aftermarket Accessory Usage > Page 160 results from the alteration or modification of a vehicle using non-GM approved parts or accessories. Dealers should be especially cautious of accessory companies that claim the installation of their product will not void the factory warranty. Many times these companies have even given direction on how to quickly disassemble the accessory in an attempt to preclude the manufacturer from finding out that is has been installed. Any suspect repairs should be reviewed by the Fixed Operations Manager (FOM), and in Canada by the Warranty Manager (WM) for appropriate repair direction. If it is decided that a goodwill repair is to be made on the vehicle, even with the installation of such non-GM approved components, the customer is to be made aware of General Motors position on this issue and is to sign the appropriate goodwill documentation required by General Motors. It is imperative for dealers to understand that by installing such devices, they are jeopardizing not only the warranty coverage, but also the performance and reliability of the customer's vehicle. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 83-81-32 > Sep > 98 > PCM Connector - Information on New Service Kits Engine Control Module: All Technical Service Bulletins PCM Connector - Information on New Service Kits File In Section: 8 - Chassis/Body Electrical Bulletin No.: 83-81-32 Date: September, 1998 INFORMATION Subject: New Powertrain Control Module (PCM) Connector Service Kits Models: 1996-99 All Passenger Cars except Geo and Catera Two new kits have been released to service the Powertrain Control Module (PCM) connector If the connector has been damaged during servicing. This PCM has an aluminum body and is usually mounted underhood. Kit (P/N 12167308) contains the 80 way connector body, the cover, two each of four different terminal retainers and 25 empty cavity plugs. No terminals are included. If terminals are needed, use P/N 12084913 for 0.35 mm and 0.50 mm wire and P/N 12084912 for 0.80 mm wire. These terminals are included in the terminal repair kit J 38125A or B, and replacements can be ordered from Kent-Moore. kit (P/N 12167313) contains one connector seal. Whenever the connector is unbolted from the aluminum body of the PCM, the seal can stick to the body, or may be twisted. This seal should be replaced whenever the connector is removed in service. Parts Information P/N Description 12167308 Kit, PCM Harness Repair 12167313 Seal Kit, PCM Connector 12084912 Terminal 12084913 Terminal Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 77-71-53 > Apr > 97 > A/T - Chuggle/Surge on TCC Apply/No DTC's Engine Control Module: All Technical Service Bulletins A/T - Chuggle/Surge on TCC Apply/No DTC's File In Section: 7 - Transmission Bulletin No.: 77-71-53 Date: April, 1997 Subject: Chuggle/Surge on TCC Apply/No DTC's (Reflash PCM) Models: 1996-97 Chevrolet and GMC C/K, G Models with 5.7L Engine (VIN R - RPO L31) and HYDRA-MATIC 4L60-E Transmission (RPO M30) Condition Some owners of the above models may experience a chuggle/surge when TCC is applied under light throttle acceleration. Cause Engine inputs (Combustion events) exciting the vehicle platform/driveline or tire balance may be a contributing factor. Correction First ensure the most recent engine, not transmission calibration has been installed (Corp. # 76-65-04) and check tire balance. A new transmission calibration to correct chuggle/surge is available for use on vehicles with persistent concerns only. Important: This calibration will raise TCC engagement approximately 7-10 mph depending on application. This calibration should not be installed until the engine calibration listed above has been installed. Installation of this calibration may lead to decreased fuel economy due to TCC engagement at higher speeds. Reflash the Powertrain Control Module with the appropriate part numbers below. Refer to your Service Manual for proper procedure. Parts Information This new calibration will be available starting with the 1997 Disc 4 update. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J6355 Reflash Control Module Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter Engine Control Module: All Technical Service Bulletins PROM - Reprogram Using Off Board Program Adapter File In Section: 6E - Engine Fuel & Emission Bulletin No.: 73-65-13 Date: March, 1997 INFORMATION Subject: Reprogramming Capability using the Off Board Programming Adapter Models: 1993-97 Passenger Cars and Trucks (Applicable Reprogrammable Vehicles) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 173 The General Motors vehicles contain Electronically Reprogrammable Devices (i.e. PCM, VCM, ECM). These vehicles cannot be programmed through PROM replacement, however service programming capability is available through the Tech 1/1A, Tech 2 and Techline terminals via direct or remote programming. The Environmental Protection Agency (EPA) has requested that all new vehicle manufacturers ensure their dealers/retailers are aware that they are responsible for providing customers access to reprogramming services at a reasonable cost and in a timely manner. Although programming of controllers has become a common service practice at GM dealers/retailers, the EPA has received reports from consumers and the aftermarket repair industry that they were unable to purchase a new (programmed) Electronically Reprogrammable Device (ERD) over-the-counter. As a result, on August 1, 1995, the Federal Government issued a regulation requiring all manufacturers to make available reprogramming to the independent aftermarket by December 1, 1997. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 174 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 175 Today, the Off Board Programming Adapter (OBPA) is used to reprogram ERD's sold over-the-counter. For all practical purposes, the OBPA takes the place of the vehicle when the vehicle is not available. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 176 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 177 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 178 The list of dealerships/retailers currently own the OBPA (see Attachments 1 - 3). These locations are equipped to provide over-the-counter preprogrammed ERD's. The hardware required to perform reprogramming in addition to the OBPA is a Techline terminal, Tech 1/1A and associated cables and adapters. THE TECH 2 SHOULD NOT BE USED WITH THE OBPA AT THIS TIME BECAUSE OF INADEQUATE OBPA GROUNDING. The current OBPA can support reprogramming on all late model General Motor's vehicles except: ^ Premium V-8's ^ 1996 Diesel Truck ^ Cadillac Catera Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 179 ^ All 1997 programmable vehicles (requires use of the Tech 2) A modification to the OBPA is being offered by Kent-Moore to support these additional vehicles and to allow reprogramming using the Tech 2. The revisions to the OBPA for the Tech 2 is very important as the Tech 2 is the only tool used for service programming for 1997 and future vehicles. To have the modifications performed, contact Kent-Moore at (800) 345-2233. The revisions (part number J 41207 REV-C) are free of charge for GM dealerships/retailers. A dealership/retailer can purchase the OBPA by contacting Kent-Moore (part number J 41207-C). Support on how to use the OBPA is provided by the Techline Customer Support Center (TCSC) at (800) 828-6860 (English) or (800) 503-3222 (French). If you need to purchase an OBPA and/or cable, contact Kent-Moore at (800) 345-2233. The OBPA retails for $695.00 (includes all revisions 1-4) under part number J 41207-C. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON Torque Converter Clutch Solenoid: All Technical Service Bulletins A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-023B Date: March, 2002 TECHNICAL Subject: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1999-2000 Cadillac Escalade 1996-2000 Chevrolet Camaro, Corvette 1996-2000 Pontiac Firebird 1996-2000 Chevrolet and GMC Light Duty Truck Models 1996-2000 Oldsmobile Bravada with 4L60-E Automatic Transmission (RPO M30) Built Prior to January 15, 2000 (Julian Date 0015) This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 Transmission/Transaxle). Condition Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated. Diagnosis Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs. The scan tool may show a DTC P1870 set as a history code. A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93° C (200°F). Cause The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply. Important: ^ DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code. ^ When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result. ^ This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle). ^ When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code. ^ When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL). Correction Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 185 regulator and isolator valves. Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body. ^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears). ^ The torque converter is not blue or overheated. ^ The transmission fluid is not burned or has no burned odor ^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 186 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 192 regulator and isolator valves. Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body. ^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears). ^ The torque converter is not blue or overheated. ^ The transmission fluid is not burned or has no burned odor ^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 193 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > Page 194 Engine Control Module: Locations Underhood Fuse-Relay Center Brake Pressure Modulator Valve Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > Page 195 Vehicle Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions Engine Control Module: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 198 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 199 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 200 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 201 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 202 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 203 Engine Control Module: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 204 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 205 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 206 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 207 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 208 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 209 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 210 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 211 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 212 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 213 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 214 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 215 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 216 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 217 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 218 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 219 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 220 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 221 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 222 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 223 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 224 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 225 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 226 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 227 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 228 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 229 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 230 Engine Control Module: Connector Views Connector End View Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 231 Connector End View Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 232 Connector Terminal ID ECM/PCM/VCM Pinout Voltage The OE manufacture does not provide an ECM/PCM/VCM connector voltage pinout chart for this vehicle, only a function description. Connector End View Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 233 Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 234 Connector Terminal ID Connector End View Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 235 Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 236 Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Page 237 Engine Control Module: Service Precautions Control Module Service Precautions The control module is designed to withstand normal current draws associated with vehicle operations. Avoid overloading any circuit. When testing for opens or shorts, do not ground any of the control module circuits unless instructed. When testing for opens or shorts, do not apply voltage to any of the control module circuits unless instructed. Only test these circuits with a digital voltmeter J 39200, while the control module connectors remain connected to the control module. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Page 238 Engine Control Module: Description and Operation GENERAL DESCRIPTION The VCM is located on the right hand side fenderwell. The VCM is the control center for the fuel, emissions, ignition, and automatic transmission control functions. The VCM constantly monitors the information from the various sensors. The VCM controls the component systems which affect the engine operation. The VCM alerts the driver through the Malfunction Indicator Lamp (MIL) or the antilock indicator lamp. The VCM stores the DTCs which identify the problem areas for the technician making repairs. Refer to Vehicle Control Module, for further information on using the diagnostic function of the VCM for engine operation. ^ Refer to Transmission for the diagnosis of the automatic transmission. ^ Refer to Anti-lock brakes for diagnosis of the brake system. The VCM in this vehicle is programmable. The only services allowed on the VCM is the control module replacement with the Knock Sensor (KS) calibrator Programmable Read Only Memory (PROM) transferred or the KS calibrator PROM only. The KS calibrator contains the up integrated knock sensor calibration. The VCM stores the 4 calibrations in the Electronically Erasable Programmable Read Only Memory (EEPROM). When replacing the VCM, programming the EEPROM and transferring the KS calibrator PROM to the new VCM is mandatory. Refer to the EEPROM Programming. Refer to VCM Replacement/Programming. See: Service and Repair The 4 calibrations required for the VCM are the Powertrain, the ABS, the VSS buffer, and the A/C. Each calibration has its own part number. Determine the correct calibrations for a particular vehicle based on the VIN number of the vehicle. MALFUNCTION INDICATOR LAMP (MIL) The MIL (Malfunction Indicator Lamp) is on the instrument panel. The MIL has the following functions: ^ The MIL informs the driver that a fault that affects the vehicle's emission levels has occurred. The owner should take the vehicle for service as soon as possible. ^ As a bulb and system check, the MIL (Malfunction Indicator Lamp) comes on with the key on and the engine not running. When the engine is started, the MIL turns off if no DTCs are set. When the MIL remains on while the engine is running, or when a malfunction is suspected due to a driveability or emissions problem, perform an On-Board Diagnostic (OBD) System Check. The procedures for these checks are given in engine controls. These checks expose faults which the technician may not detect if other diagnostics are performed first. DIAGNOSTIC INFORMATION The diagnostic Tables and functional checks are designed to locate a faulty circuit or component through a process of logical decisions. The Tables are prepared with the assumption that the vehicle functioned correctly at the time of assembly and that there are not multiple faults present. There is a continuous self-diagnosis on certain control functions. This diagnostic capability is complemented by the diagnostic procedures contained in this manual. The language of communicating the source of the malfunction is a system of diagnostic trouble codes. When a malfunction is detected by the control module, a diagnostic trouble code will set and the Malfunction Indicator Lamp (MIL) Malfunction Indicator Lamp will illuminate on some applications. VCM LEARNING ABILITY WARNING: Since the VCM is located under the hood, its connectors are sealed and cannot be backprobed as in the previous model years. Do not attempt to backprobe as a connector or seal damage could occur. The VCM's learning ability allows it to make corrections for minor variations in the fuel system in order to improve driveability. When the battery is disconnected for other repairs, the learning process resets. The driver my note a change in the vehicle's performance. In order to teach the vehicle ensure that the engine is at the operating temperature. Drive the vehicle at part throttle with a moderate acceleration and idle conditions until normal performance returns. INPUT INFORMATION The VCM processes the various input information. Then the VCM sends the necessary electrical responses to the control fuel delivery, the spark timing, and the other emission control systems. The input information interrelates to more than one output; therefore, if the one input fails, the failure can affect more than one system's operation. PROM (KS Module) This assembly contains an electronic Knock Sensor (KS) module. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Page 239 MEMORY There are two types of memory storage within the VCM, EEPROM and RAM. EEPROM Electrically Erasable Programmable Read Only Memory (EEPROM) is a permanent memory that is physically soldered to the circuit boards within the VCM. The EEPROM contains the overall control algorithms. The EEPROM can be reprogrammed by using the scan tool. RAM Random Access Memory (RAM) is the microprocessor scratch pad. The processor can write into or read from this memory as needed. This memory is volatile and needs a constant supply of voltage to be retained. If the voltage is lost, the memory is lost. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Testing and Inspection > Component Tests and General Diagnostics Engine Control Module: Component Tests and General Diagnostics The approved procedure for diagnosing all powertrain control system faults is included in the Strategy Based Diagnostics. The preliminary checks and the Powertrain On-board Diagnostic System Check must be performed to successfully diagnose and repair the powertrain systems. To read and clear diagnostic trouble codes, use a scan tool. See: Powertrain Management/Computers and Control Systems/Testing and Inspection Use a scan tool to clear diagnostic trouble codes from the VCM memory. Diagnostic trouble codes can also be cleared by turning OFF the ignition and disconnecting the battery power from the VCM for 30 seconds, but this method will also cause all diagnostic information in the VCM memory to be cleared and all the diagnostic tests will have to be re-run. Since the VCM can have a failure which may affect only one circuit, following the approved diagnostic procedures will determine which circuit has a problem and where it is. If a diagnostic table indicates that the VCM connections or VCM is the cause of a problem and the VCM is replaced. but does not correct the problem, one of the following conditions may exist: ^ There is a problem with the VCM terminal connections. The diagnostic table will indicate that the VCM connections or VCM is the problem. The terminals may have to be removed from the VCM connector in order to check them properly. ^ The EEPROM program is not correct for the application. Incorrect components may cause a malfunction and may or may not set a DTC. ^ The problem is intermittent. This means that the problem is not present at the time the system is being checked. In this case, refer to Symptoms and make a careful visual and physical inspection of all suspected components and wiring associated with the affected system. See: Powertrain Management/Computers and Control Systems/Testing and Inspection ^ There is a shorted solenoid, relay coil, or harness. Solenoids and relays are turned ON and OFF by the VCM using internal electronic switches called drivers. Each driver is part of a group of seven called output driver modules. A shorted solenoid, relay coil, or harness will not damage the VCM but will cause the solenoid or relay to be inoperative. The J 34636 tester, or equivalent, provides a fast, accurate means of checking for a shorted coil or a short to battery voltage. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Service and Repair > Control Module Replacement Engine Control Module: Service and Repair Control Module Replacement VCM Harness Connections VCM Access Cover Removing Knock Sensor Module From PCM Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Service and Repair > Control Module Replacement > Page 244 VCM REPLACEMENT/PROGRAMMING Service of the VCM consists of either replacement of VCM or reprogramming of the EEPROM. If the diagnostics call for replacement of the VCM, it will be necessary to transfer the PROM and program the EEPROM. NOTE: When replacing the production VCM with a service VCM (controller), it is important to transfer the broadcast code and production VCM number to the service VCM label. This will allow positive identification of VCM parts throughout the service life of the vehicle. Also transfer the PROM. CAUTION: To prevent internal VCM damage, the ignition must be OFF when disconnecting or reconnecting power to the VCM (for example, battery cable, VCM fuse, jumper cables, etc.). CAUTION: In order to prevent possible Electrostatic Discharge damage to the VCM, do not touch the connector pins or soldered components on the circuit board. VCM REPLACEMENT/PROGRAMMING (WITH KNOCK SENSOR (KS) CALIBRATION PROM) REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Remove the connectors from the VCM. 3. Remove the spring retainer off and over the rail of the VCM. Slide the VCM out of the bracket at an angle. 4. Remove the VCM access cover. 5. Remove the PROM/Knock Sensor (KS) module. 6. Inspect for the alignment notches of the KS Calibration PROM. 7. Carefully set it aside. 8. Do not open the KS Calibration PROM. 9. Remove the new VCM from the packaging. Check the service number in order to make sure it is the same as the defective VCM. 10. Remove the access cover. NOTE ^ The Knock Sensor (KS) module must be transferred to the replacement VCM. ^ The replacement VCM is supplied without a EEPROM program, the replacement VCM must be programmed before the vehicle will run. ^ Using the thumb and first finger, remove the KS Calibration PROM by gently squeezing each end of the blue KS Calibration PROM ^ Do not remove the cover of the KS Calibration PROM. Use of an unapproved KS Calibration PROM removal methods may cause damage to the KS Calibration PROM or the socket. INSTALLATION PROCEDURE NOTE: Press only on the ends of the KS Calibration PROM. Gently press on the KS Calibration PROM until it is firmly seated in the socket. Listen for the click. 1. Align the notches of the KS Calibration PROM with the notches in the KS Calibration PROM socket. 2. Install the KS Calibration PROM in the KS Calibration PROM socket. 3. Install the access cover on the VCM. 4. Install the VCM in the engine compartment. 5. Install the connectors to the VCM. 6. The MIL, antilock and brake lamps will continue to be enabled until the VCM is programmed. Once the programming is complete, the lamps will turn off and normal operation will occur. 7. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Service and Repair > Control Module Replacement > Page 245 CAUTION: In order to prevent possible Electrostatic Discharge damage to the VCM, do not touch the connector pins or soldered components on the circuit board. 8. Proceed to the EEPROM programming. See: EEPROM Programming Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Service and Repair > Control Module Replacement > Page 246 Engine Control Module: Service and Repair EEPROM Programming CAUTION: The ignition should always be "off" when installing or removing the Vehicle Control Module (VCM) connectors. 1. Set-up: ^ Battery is charged. ^ Ignition is "ON." ^ Battery/cig. lighter Connection secure. ^ Data Link Connector (DLC). 2. Refer to up-to-date Techline terminal/equipment user's instructions. 3. If Vehicle Control Module (VCM) fails to program, do the following: ^ Check all VCM connections. ^ check Techline terminal/equipment for latest software version. ^ Try again to program the VCM. If it fails again, replace the VCM. Refer to VCM replacement. See: Control Module Replacement 4. Perform the Idle Air Control (IAC) valve reset procedure with the scan tool. use misc. test. 5. For a functional check perform one of the steps: ^ Use the Techline terminal and equipment in order to perform the On-Board Diagnostic (OBD) System Check ^ Refer to Powertrain OBD System Check. See: Powertrain Management/Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Knock Sensor Module > Component Information > Diagrams Knock Sensor Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Emission Control Systems > Air Injection Pump Relay > Component Information > Locations Air Injection Pump Relay: Locations Underhood Fuse-Relay center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Locations Fuel Pump Balance Module: Locations FUEL PUMP BALANCE MODULE (Vehicles with Dual Tanks Only) On vehicles over 15,000 GVWR and equipped with dual fuel tanks, the Fuel Pump Balance Module is located inside the left frame rail, near Transmission Crossmember. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Locations > Page 258 Fuel Pump Balance Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Locations > Page 259 Fuel Pump Balance Module: Description and Operation FUEL BALANCE CONTROL SYSTEM The fuel balance control system consists of the following components: - Front (main) fuel tank sender. - Rear (auxiliary) fuel tank sender. - Balance fuel pump. - Balance fuel pump relay. - Fuel sender and balance module. On vehicles with dual tanks, the front tank is the main and the rear tank is the auxiliary. The main fuel pump supplies fuel to the fuel injection unit. The low pressure (about 32 kPa or 7 psi) fuel balance pump is used only to transfer fuel from the auxiliary tank to the main tank in order to balance the fuel levels in both tanks. As the main tank level drops to about 25 % below the level in the auxiliary tank, the fuel sender and balance module energizes the fuel pump relay. This pumps the fuel from the auxiliary tank to the main tank. When the level in the main tank reaches a level slightly higher than the level in the auxiliary tank, or the auxiliary tank is empty, the module de-energizes the balance pump relay and fuel pump. Any malfunction in either of the fuel gage circuits will disable the system and the fuel will not be transferred from the main fuel tank to the auxiliary fuel tank. FUEL PUMP BALANCE MODULE The Fuel Pump Balance Module relies on input from the primary and secondary fuel senders, and cannot operate if the fuel gauge is not working properly. For Fuel Pump Balance Module testing and inspection refer to Instrument Panel, Gauges and Warning Indicators / Symptom Releated Diagnostic Procedures / Fuel Gauge See: Instrument Panel, Gauges and Warning Indicators/Testing and Inspection/Symptom Related Diagnostic Procedures For Fuel Pump Balance Module electrical diagrams refer to Instrument Panel, Gauges and Warning Indicators / Diagrams / Electrical. See: Instrument Panel, Gauges and Warning Indicators/Diagrams Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times Fuel Gage Indicates Empty At All Times Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times > Page 262 Fuel Gage Indicates Full At All Times Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times > Page 263 Fuel Pump Balance Module: Testing and Inspection Fuel Gage Is Inaccurate Fuel Gage Is Inaccurate (Part 1 Of 2) Fuel Gage Is Inaccurate (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times > Page 264 Fuel Pump Balance Module: Testing and Inspection Vehicle Runs Out of Fuel (Rear Tank Not Empty) Vehicle Runs Out Of Fuel At Half-Full/rear Tank Is Full At All Times (Part 1 Of 2) Vehicle Runs Out Of Fuel At Half-Full/rear Tank Is Full At All Times (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times > Page 265 Fuel Gage Does Not Change Position On Scale Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Page 266 Fuel Pump Balance Module: Service and Repair REMOVAL PROCEDURE WARNING: To reduce the risk of fire and personal in jury that may result from a fuel leak, always replace O-ring seals exposed during component service. 1. Disconnect the negative battery cable. 2. Loosen the filler cap(s) to Relieve fuel tank pressure. See: Powertrain Management/Fuel Delivery and Air Induction/Service and Repair 3. Disconnect the electrical connector. 4. Clean both fuel pipe connections and surrounding areas at the fuel pump before disconnecting to avoid possible contamination of the fuel system. 5. Disconnect both fuel pipes from the pump. 6. Slide the pump out of the bracket. INSTALLATION PROCEDURE 1. Install the new fuel pipe O-rings. 2. Position the new pump in the pump bracket. 3. Connect the fuel feed pipe and suction pipe to the fuel pump. Tighten Use a backup wrench to prevent the pump from turning. Tighten the fittings to 3O Nm (22 lb. ft.). 4. Connect the electrical connector. 5. Connect the negative battery cable. 6. Check for fuel leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Page 267 6.1. Turn the ignition ON for 2 seconds. 6.2. Turn OFF the ignition for 10 seconds. 6.3. Again, turn the ignition switch to the ON position. 6.4. Check for fuel leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Locations > Fuel Pump Relay Fuel Pump Relay: Locations Fuel Pump Relay FUEL PUMP RELAY Auxiliary Battery Wiring Underhood Fuse-Relay Center The Fuel Pump Relay is located in Underhood Fuse Relay Center. The Underhood Fuse Relay Center is located on the LH rear of engine compartment, on fender. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Locations > Fuel Pump Relay > Page 272 Fuel Pump Relay: Locations Fuel Pump Relay (Balance Pump) FUEL PUMP RELAY (BALANCE PUMP) (Vehicles with Dual Tanks Only) On vehicles over 15,000 GVWR and equipped with dual fuel tanks, the Fuel Pump Balance Relay is located inside the left frame rail, near Transmission Crossmember. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions Fuel Pump Relay: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 275 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 276 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 277 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 278 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 279 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 280 Fuel Pump Relay: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 281 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 282 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 283 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 284 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 285 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 286 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 287 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 288 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 289 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 290 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 291 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 292 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 293 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 294 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 295 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 296 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 297 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 298 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 299 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 300 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 301 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 302 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 303 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 304 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 305 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 306 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 307 Fuel Pump Relay: Connector Views Fuel Pump Balance Relay Fuel Pump Relay FUEL PUMP RELAY CONNECTOR VIEW Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 308 Underhood Fuse-Relay Center (Part 1 Of 2) The Fuel Pump Relay is located in the Underhood Fuse-Relay Center. Refer to terminals, A1 - B1 B2 - A3 - B3. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Description and Operation > Fuel Pump Relay Operation Fuel Pump Relay: Description and Operation Fuel Pump Relay Operation OPERATION When the key is turned ON with out the engine running, the control module turns a fuel pump relay ON for two seconds. This builds up fuel pressure quickly. If the engine is not started within two seconds, the control module shuts the fuel pump OFF and waits until the engine starts. As soon as the engine is cranked, the control module turns the relay ON and runs the fuel pump. When the engine is cranking or running, the control module receives the Crankshaft Position (CKP) sensor reference pulses which in turn energize the fuel injectors. As a backup system to the fuel pump relay, the fuel pump can also be turned ON by a fuel pump oil pressure switch. When the engine reaches about 28 kPa (4 psi), and the fuel pump relay does not complete the circuit, the fuel pump oil pressure switch will close to complete the circuit to run the fuel pump. An inoperative fuel pump relay can result in long cranking times, particularly if the engine is cold. The fuel pump oil pressure switch will turn ON the fuel pump as soon as oil pressure reaches about 28 kPa (4 psi). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Description and Operation > Fuel Pump Relay Operation > Page 311 Fuel Pump Relay: Description and Operation Fuel Balance Module Control System (Dual Tanks) FUEL BALANCE CONTROL SYSTEM The fuel balance control system consists of the following components: - Front (main) fuel tank sender. - Rear (auxiliary) fuel tank sender. - Balance fuel pump. - Balance fuel pump relay. - Fuel sender and balance module. On vehicles with dual tanks, the front tank is the main and the rear tank is the auxiliary. The main fuel pump supplies fuel to the fuel injection unit. The low pressure (about 32 kPa or 7 psi) fuel balance pump is used only to transfer fuel from the auxiliary tank to the main tank in order to balance the fuel levels in both tanks. As the main tank level drops to about 25 % below the level in the auxiliary tank, the fuel sender and balance module energizes the fuel pump relay. This pumps the fuel from the auxiliary tank to the main tank. When the level in the main tank reaches a level slightly higher than the level in the auxiliary tank, or the auxiliary tank is empty, the module de-energizes the balance pump relay and fuel pump. Any malfunction in either of the fuel gage circuits will disable the system and the fuel will not be transferred from the main fuel tank to the auxiliary fuel tank. FUEL PUMP BALANCE MODULE The Fuel Pump Balance Module relies on input from the primary and secondary fuel senders, and cannot operate if the fuel gauge is not working properly. For Fuel Pump Balance Module testing and inspection refer to Instrument Panel, Gauges and Warning Indicators / Symptom Releated Diagnostic Procedures / Fuel Gauge See: Instrument Panel, Gauges and Warning Indicators/Testing and Inspection/Symptom Related Diagnostic Procedures For Fuel Pump Balance Module electrical diagrams refer to Instrument Panel, Gauges and Warning Indicators / Diagrams / Electrical. See: Instrument Panel, Gauges and Warning Indicators/Diagrams Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Description and Operation > Page 312 Fuel Pump Relay: Service and Repair Removal Procedure 1. Remove the underhood electrical center cover. 2. Remove the relay. Installation Procedure 1. Install the relay. 2. Install the underhood electrical center cover. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Ignition System > Ignition Control Module > Component Information > Description and Operation Ignition Control Module: Description and Operation Ignition Control Driver (ICD) Module And Ignition Coil The Ignition Coil Driver Module is mounted on a bracket next to the coil. The Vehicle Control Module (VCM) signals the Ignition Control Driver (ICD) to turn "ON" primary current to the ignition coil by pulling the Ignition Control (IC) line high (4 volts). The IC turns the primary current "ON" and "OFF" by applying and removing the ground to the primary winding at the appropriate time. This module is of 'minimum function" and does not contain backup calibrations that would allow the engine to continue to rim if the IC signal is lost. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Ignition System > Ignition Control Module > Component Information > Description and Operation > Page 317 Ignition Control Module: Testing and Inspection If the vehicle cranks for at least 5 seconds and the Engine Control Module doesn't see a referance signal, some Models will set a code, 42 (Hard) or 12 (Soft). If your vehicle has one of these codes, begin with the Diagnostic System Check in Computers and Controls, then proceed to the Trouble Code Chart (Yes, some vehicles have a DTC Chart for Code 12). If the vehicle does not set a code, begin with the Diagnostic System Check, and it will send you to a Diagnostic Chart that checks for your particular condition. These types of tests are found under Computers and Control Systems. See: Powertrain Management/Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Restraint Systems > Air Bag Control Module > Component Information > Locations > System Component Locations Air Bag Control Module: Locations System Component Locations Fig. 4 Air Bag System Component Locations Refer to Fig. 4 for air bag system component locations. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Restraint Systems > Air Bag Control Module > Component Information > Locations > System Component Locations > Page 323 Air Bag Control Module: Locations Diagnostic Energy Reserve Module (DERM) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Restraint Systems > Air Bag Control Module > Component Information > Locations > System Component Locations > Page 324 Cargo Lamp Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Restraint Systems > Air Bag Control Module > Component Information > Locations > Page 325 Description Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Restraint Systems > Air Bag Control Module > Component Information > Locations > Page 326 Air Bag Control Module: Description and Operation A function of the DERM is to supply the deployment loop with a 36 volt loop reserve to ensure sufficient energy to deploy the air bag if the ignition feed to the arming sensor is lost during a frontal collision. Another function of the DERM is electrical system diagnostics. The DERM can detect circuit and component malfunctions within the deployment loop. Voltage drops across components within the loop are measured during non-deployment conditions. If the monitored voltages fall outside of the expected limits, the DERM will indicate a malfunction through the storage of a diagnostic trouble code and the illumination of the air bag warning light. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Restraint Systems > Air Bag Control Module > Component Information > Locations > Page 327 Air Bag Control Module: Service and Repair Prior to performing replacement procedures, disarm air bag system. Refer to, Service and Repair/ Air Bag System Disarming & Air Bag System Arming. Refer to, / Specifications/ Mechanical for torque values when installing components. All sensors and mounting bracket bolts must be carefully torqued to assure proper operation. Never power up the air bag system when any sensor is not rigidly attached to the vehicle, since the sensor could be activated when not attached, causing air bag deployment. Do not open DERM case for any reason. Touching connector pins or soldered components may cause electrostatic discharge damage. Repair of a malfunctioning DERM is by replacement only. 1. Remove DERM from mounting bracket. 2. Remove Connector Position Assurance (CPA) lock, then disconnect DERM electrical connector from DERM. 3. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Starting and Charging > Starter Relay > Component Information > Locations Starter Relay: Locations In Underhood Fuse - Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > Customer Interest for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder Control Module: Customer Interest A/T - Upshift Flare/No 3rd or 4th/Launch Shudder File In Section: 07 - Transmission/Transaxle Bulletin No.: 00-07-30-026 Date: December 2000 TECHNICAL Subject: Automatic Transmission 1-2 and/or 2-3 Upshift Slip/Flare, No 3rd or 4th gear, Launch Shudder (Revise VCM Wiring) Models: 1996 Chevrolet and GMC C/K, S/T, M/L, G1, G2, P3 Models 1996 Oldsmobile Bravada with VCM and 4L60-E (M30) or 4L80-E (MT1) Automatic Transmission This bulletin is being reissued to ensure that correct procedures are followed for this condition. Please discard Corporate Bulletin Number 66-71-03A (Section 7 - Automatic Transmission). When performing a transmission replacement labor operation K7000 on these vehicles with a 4L60-E or 4L80-E, you must include front chassis wire repair labor operation N6112. Inspect the VCM to verify the latest part number revision (16244210). Condition Some owners may comment that the automatic transmission has either a slip or flare on the 1-2 and/or 2-3 upshift, or no 3rd or 4th gear, or launch shudder. Upon investigation, the technician may find a DTC P1870 stored in the VCM. Cause A poor internal ground between the two circuit boards of the VCM may cause the VCM to command erratic line pressure at the pressure control (PC) solenoid valve. Correction Using harness jumper wire and instruction kit, P/N 12167310, revise the wiring harness at the VCM connector. Corrections were made to the VCM beginning 2/14/96. The corrected VCMs are identified with service number 16244210 on the VCM identification label. Procedure The following is a summary of the instructions included with the service kit: 1. Remove the negative terminal from the battery. 2. Move the wire located at connector J3 (WHITE/GREY/CLEAR), pin 18 to connector J1 (BLUE), pin 23. 3. Install the jumper wire between connector J2 (RED), pin 26 and connector J3 (WHITE/GREY/CLEAR), pin 18. 4. Install the tag included in the kit around the. VCM wiring harness. This tag notes that the wiring harness has been modified. 5. Reconnect the negative battery terminal. Road test to verify that the condition has been corrected. If any of the following conditions are noted, the transmission should be repaired or replaced using the most cost effective method. Canadian dealers should repair the transmission. ^ Transmission fluid oxidation or excessive sediment. ^ Transmission slip or flare after this service fix is performed. ^ DTC P1870 is stored on a 4L60-E (M30). The following tools are available from Kent-Moore (1-800-345-2233) for use in removing and relocating the VCM wires: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > Customer Interest for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder > Page 342 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder Control Module: All Technical Service Bulletins A/T - Upshift Flare/No 3rd or 4th/Launch Shudder File In Section: 07 - Transmission/Transaxle Bulletin No.: 00-07-30-026 Date: December 2000 TECHNICAL Subject: Automatic Transmission 1-2 and/or 2-3 Upshift Slip/Flare, No 3rd or 4th gear, Launch Shudder (Revise VCM Wiring) Models: 1996 Chevrolet and GMC C/K, S/T, M/L, G1, G2, P3 Models 1996 Oldsmobile Bravada with VCM and 4L60-E (M30) or 4L80-E (MT1) Automatic Transmission This bulletin is being reissued to ensure that correct procedures are followed for this condition. Please discard Corporate Bulletin Number 66-71-03A (Section 7 - Automatic Transmission). When performing a transmission replacement labor operation K7000 on these vehicles with a 4L60-E or 4L80-E, you must include front chassis wire repair labor operation N6112. Inspect the VCM to verify the latest part number revision (16244210). Condition Some owners may comment that the automatic transmission has either a slip or flare on the 1-2 and/or 2-3 upshift, or no 3rd or 4th gear, or launch shudder. Upon investigation, the technician may find a DTC P1870 stored in the VCM. Cause A poor internal ground between the two circuit boards of the VCM may cause the VCM to command erratic line pressure at the pressure control (PC) solenoid valve. Correction Using harness jumper wire and instruction kit, P/N 12167310, revise the wiring harness at the VCM connector. Corrections were made to the VCM beginning 2/14/96. The corrected VCMs are identified with service number 16244210 on the VCM identification label. Procedure The following is a summary of the instructions included with the service kit: 1. Remove the negative terminal from the battery. 2. Move the wire located at connector J3 (WHITE/GREY/CLEAR), pin 18 to connector J1 (BLUE), pin 23. 3. Install the jumper wire between connector J2 (RED), pin 26 and connector J3 (WHITE/GREY/CLEAR), pin 18. 4. Install the tag included in the kit around the. VCM wiring harness. This tag notes that the wiring harness has been modified. 5. Reconnect the negative battery terminal. Road test to verify that the condition has been corrected. If any of the following conditions are noted, the transmission should be repaired or replaced using the most cost effective method. Canadian dealers should repair the transmission. ^ Transmission fluid oxidation or excessive sediment. ^ Transmission slip or flare after this service fix is performed. ^ DTC P1870 is stored on a 4L60-E (M30). The following tools are available from Kent-Moore (1-800-345-2233) for use in removing and relocating the VCM wires: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder > Page 348 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Wiper and Washer Systems > Wiper Control Module > Component Information > Technical Service Bulletins > Recalls: > NHTSA98V150001 > Jul > 98 > Recall 98V150001: Windshield Wiper Defect Wiper Control Module: Recalls Recall 98V150001: Windshield Wiper Defect Light duty pickup trucks and sport utility vehicles, 2 and 4-wheel drive. Solder joints near the wiring harness connector can crack causing the windshield wipers to work intermittently. This condition can result in inoperative wipers, reducing a driver's visibility, and increasing the risk of a vehicle crash. Dealers will replace the wiper motor circuit board and cover. Owner notification began December 15, 1998. Owners who take their vehicles to an authorized dealer on an agreed upon service date and do not receive the free remedy within a reasonable time should contact Chevrolet at 1-800-222-1020 or GMC at 1-800-462-8782. Also contact the National Highway Traffic Safety Administration's Auto Safety Hotline at 1-888-DASH-2-DOT (1-888-327-4236). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Wiper and Washer Systems > Wiper Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > NHTSA98V150001 > Jul > 98 > Recall 98V150001: Windshield Wiper Defect Wiper Control Module: All Technical Service Bulletins Recall 98V150001: Windshield Wiper Defect Light duty pickup trucks and sport utility vehicles, 2 and 4-wheel drive. Solder joints near the wiring harness connector can crack causing the windshield wipers to work intermittently. This condition can result in inoperative wipers, reducing a driver's visibility, and increasing the risk of a vehicle crash. Dealers will replace the wiper motor circuit board and cover. Owner notification began December 15, 1998. Owners who take their vehicles to an authorized dealer on an agreed upon service date and do not receive the free remedy within a reasonable time should contact Chevrolet at 1-800-222-1020 or GMC at 1-800-462-8782. Also contact the National Highway Traffic Safety Administration's Auto Safety Hotline at 1-888-DASH-2-DOT (1-888-327-4236). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Wiper and Washer Systems > Wiper Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wiper Control Module: > 83-90-12 > Aug > 98 > Tools - Keyless Entry Transmitter Tester Keyless Entry Transmitter: All Technical Service Bulletins Tools - Keyless Entry Transmitter Tester File In Section: 9 - Accessories Bulletin No.: 83-90-12 Date: August, 1998 INFORMATION Subject: Essential Tool J 43241 Remote Keyless Entry and Passive Keyless Entry Transmitter Tester Models: 1990-99 Passenger Cars and Trucks with Remote Keyless Entry or Passive Keyless Entry Systems A new essential tool, J 43241 Remote Keyless Entry Transmitter Tester, has been sent to all GM Dealers. This tester can be used on all RKE and PKE systems, on past as well as current models. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Wiper and Washer Systems > Wiper Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wiper Control Module: > 83-90-12 > Aug > 98 > Tools - Keyless Entry Transmitter Tester > Page 368 Important: Before using the tester and the diagnostic chart, the following two steps must be performed. 1. Verify that the keyless entry transmitter is the correct model for the vehicle remote system. An incorrect model transmitter may pass this test, but may not activate the vehicle remote system. The correct transmitter can usually be identified by part number. 2. Ensure that the transmitter is synchronized with the vehicle (if applicable). Refer to Transmitter Synchronization in the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Wiper and Washer Systems > Wiper Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wiper Control Module: > 66-90-03 > Jun > 97 > Keyless Entry - Unintended Release of Rear Hatch Keyless Entry Transmitter: All Technical Service Bulletins Keyless Entry - Unintended Release of Rear Hatch File In Section: 9 - Accessories Bulletin No.: 66-90-03 Date: June, 1997 Subject: Unintended Release of Rear Hatch (Replace Transmitter Cover) Models: 1994-96 Chevrolet and GMC C/K, S/T, M/L, G Models 1994 Oldsmobile Bravada 1996 Oldsmobile Bravada Condition An owner may report that the Rear Hatch Releases without their being aware of it. Cause The Keyless Entry Transmitter Button is unintentionally bumped activating the hatch release. Correction Replace the Keyless Entry Transmitter Cover. The revised cover has a deeper recess around the release button making it less prone to inadvertent bumping. Parts Information P/N Description Qty 15740707 Bezel, Transmitter Cover 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time R4490 Control Assembly 0.3 hr Cover - Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Relays and Modules > Relays and Modules - Wiper and Washer Systems > Wiper Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wiper Control Module: > 83-90-12 > Aug > 98 > Tools - Keyless Entry Transmitter Tester > Page 378 Important: Before using the tester and the diagnostic chart, the following two steps must be performed. 1. Verify that the keyless entry transmitter is the correct model for the vehicle remote system. An incorrect model transmitter may pass this test, but may not activate the vehicle remote system. The correct transmitter can usually be identified by part number. 2. Ensure that the transmitter is synchronized with the vehicle (if applicable). Refer to Transmitter Synchronization in the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Body and Frame > Power Door Lock Switch > Component Information > Locations > Door Lock Switch Front Door Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Body and Frame > Power Door Lock Switch > Component Information > Locations > Door Lock Switch > Page 389 Power Door Lock Switch: Locations Door Lock Switch, Right Front On LH Door Trim Panel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Body and Frame > Power Mirror Switch > Component Information > Locations Power Mirror Switch: Locations On LH Door Trim Panel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Body and Frame > Power Seat Switch > Component Information > Locations > Forward/Rearward Up and Down Switch Power Seat Switch: Locations Forward/Rearward Up and Down Switch LH rear top of Engine, above Valve Cover Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Body and Frame > Power Seat Switch > Component Information > Locations > Forward/Rearward Up and Down Switch > Page 397 Power Seat Switch: Locations Power Lumbar Seat Switch LH Front front Under Passenger's Seat RH Front front Under Passenger's Seat Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Body and Frame > Power Seat Switch > Component Information > Locations > Forward/Rearward Up and Down Switch > Page 398 Power Seat Switch: Locations Tilt Switch, Front On Seat Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Body and Frame > Trunk / Liftgate Switch > Component Information > Locations > Luggage Compartment Latch Switch Trunk / Liftgate Switch: Locations Luggage Compartment Latch Switch LH side of I/P Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Body and Frame > Trunk / Liftgate Switch > Component Information > Locations > Luggage Compartment Latch Switch > Page 403 Trunk / Liftgate Switch: Locations Rear Glass Release Switch LH side of I/P Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Brakes and Traction Control > Brake Fluid Pressure Sensor/Switch > Component Information > Locations Brake Fluid Pressure Sensor/Switch: Locations Behind I/P Compartment Box on HVAC Plenum Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Brakes and Traction Control > Braking Sensor/Switch > Component Information > Service and Repair Braking Sensor/Switch: Service and Repair Stop Lamp Switch Remove or Disconnect 1. Negative battery cable. 2. Disable SIR. 3. Retainer from brake pedal pin. Use snap ring pliers. 4. Switch by unsnapping from pushrod. 5. Electrical connector from switch. Install or Connect 1. Electrical connector into switch. 2. Switch by snapping it onto pushrod. 3. Retainer onto brake pedal pin. Use 11mm (7/16 inch) socket to push new clip on pin. 4. Negative battery cable. 5. Enable SIR. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Technical Service Bulletins > Customer Interest: > 02-05-25-006B > Jan > 06 > Brakes - Low Speed (Below 5 MPH) ABS Activation Wheel Speed Sensor: Customer Interest Brakes - Low Speed (Below 5 MPH) ABS Activation Bulletin No.: 02-05-25-006B Date: January 05, 2006 TECHNICAL Subject: Antilock Brake (ABS) Activation At Low Speeds (Clean Wheel Speed Sensor Mounting Surface) Models: 1999-2000 Cadillac Escalade 1995-1999 Chevrolet Silverado (Old Style) 1995-2000 Chevrolet Suburban, Tahoe (Old Style) 1995-2003 Chevrolet Astro Van, Blazer, S10 1995-1999 GMC Sierra (Old Style) 1995-2000 GMC Yukon, Yukon XL (Old Style) 1995-2001 GMC Envoy, Jimmy 1995-2003 GMC Safari Van, Sonoma 1995-2001 Oldsmobile Bravada Supercede: This bulletin is being revised to update the correction and warranty information. Please discard Corporate Bulletin Number 02-05-25-006A (Section 05 - Brakes). Condition Some customers may comment on ABS activation at low speeds, usually below 8 km/h (5 mph). Upon investigation, the technician will find no DTCs set. Cause The cause of this condition may be an increased air gap between the wheel speed sensor and the hub reluctor ring due to rust and debris built up on the sensor mounting surface. Correction Measure AC voltage and clean wheel speed sensor mounting surfaces. 1. Raise the vehicle on a hoist. 2. Disconnect both the front wheel speed sensor harness connectors. 3. Place a DVM across the terminals of each sensor connector. 4. Rotate the wheel with hand speed and measure the ACmV's. The reading should be at least 350 ACmV's. 5. If the reading is between 200 and 350 ACmV's, remove the wheel, caliper and rotor in order to gain access to the speed sensor. 6. Remove the wheel speed sensor and plug the hole to prevent debris from falling into the hub during service. 7. Clean the wheel speed sensor mounting surface using a wire brush, sand paper, emery cloth, ScotchBrite(TM) or other suitable material. Be sure to thoroughly clean the wheel speed sensor surface. There should be no rust or corrosion. 8. Check the sensor head to determine if it has been warped/distorted due to the corrosion build up or other causes. Check the mounting surface on the sensor head for flatness by placing it on the edge of a metal machinists scale or other suitable straight edge to measure the flatness. Check the sensor for flatness in multiple (minimum 3) positions/directions. If the sensor head is distorted, replace the sensor. 9. Apply (spray) two thin coats of the specified rust penetrating lubricant (corrosion inhibitor) to the complete sensor mounting surface on the bearing hub. Allow to dry for 3-5 minutes between coats. Use ONLY Rust Penetrating Lubricant, P/N 89022217 (Canadian P/N 89022218). 10. When the corrosion inhibitor is dry to the touch (about 10 minutes), apply a thin layer of bearing grease to the hub surface and sensor 0-ring prior to sensor installation. Use ONLY Wheel Bearing Lubricant, P/N 01051344 (Canadian P/N 993037). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Technical Service Bulletins > Customer Interest: > 02-05-25-006B > Jan > 06 > Brakes - Low Speed (Below 5 MPH) ABS Activation > Page 419 11. Install either the original sensor or a new one in the hub and secure the sensor. Ensure that the sensor is seated flush against the hub. 12. Install the rotor, the caliper and the wheel. 13. Place the DVM across the sensor terminals and recheck the voltage while rotating the wheel by hand. The voltage should now read at least 350 ACmV's. Parts Information Warranty Information For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 02-05-25-006B > Jan > 06 > Brakes - Low Speed (Below 5 MPH) ABS Activation Wheel Speed Sensor: All Technical Service Bulletins Brakes - Low Speed (Below 5 MPH) ABS Activation Bulletin No.: 02-05-25-006B Date: January 05, 2006 TECHNICAL Subject: Antilock Brake (ABS) Activation At Low Speeds (Clean Wheel Speed Sensor Mounting Surface) Models: 1999-2000 Cadillac Escalade 1995-1999 Chevrolet Silverado (Old Style) 1995-2000 Chevrolet Suburban, Tahoe (Old Style) 1995-2003 Chevrolet Astro Van, Blazer, S10 1995-1999 GMC Sierra (Old Style) 1995-2000 GMC Yukon, Yukon XL (Old Style) 1995-2001 GMC Envoy, Jimmy 1995-2003 GMC Safari Van, Sonoma 1995-2001 Oldsmobile Bravada Supercede: This bulletin is being revised to update the correction and warranty information. Please discard Corporate Bulletin Number 02-05-25-006A (Section 05 - Brakes). Condition Some customers may comment on ABS activation at low speeds, usually below 8 km/h (5 mph). Upon investigation, the technician will find no DTCs set. Cause The cause of this condition may be an increased air gap between the wheel speed sensor and the hub reluctor ring due to rust and debris built up on the sensor mounting surface. Correction Measure AC voltage and clean wheel speed sensor mounting surfaces. 1. Raise the vehicle on a hoist. 2. Disconnect both the front wheel speed sensor harness connectors. 3. Place a DVM across the terminals of each sensor connector. 4. Rotate the wheel with hand speed and measure the ACmV's. The reading should be at least 350 ACmV's. 5. If the reading is between 200 and 350 ACmV's, remove the wheel, caliper and rotor in order to gain access to the speed sensor. 6. Remove the wheel speed sensor and plug the hole to prevent debris from falling into the hub during service. 7. Clean the wheel speed sensor mounting surface using a wire brush, sand paper, emery cloth, ScotchBrite(TM) or other suitable material. Be sure to thoroughly clean the wheel speed sensor surface. There should be no rust or corrosion. 8. Check the sensor head to determine if it has been warped/distorted due to the corrosion build up or other causes. Check the mounting surface on the sensor head for flatness by placing it on the edge of a metal machinists scale or other suitable straight edge to measure the flatness. Check the sensor for flatness in multiple (minimum 3) positions/directions. If the sensor head is distorted, replace the sensor. 9. Apply (spray) two thin coats of the specified rust penetrating lubricant (corrosion inhibitor) to the complete sensor mounting surface on the bearing hub. Allow to dry for 3-5 minutes between coats. Use ONLY Rust Penetrating Lubricant, P/N 89022217 (Canadian P/N 89022218). 10. When the corrosion inhibitor is dry to the touch (about 10 minutes), apply a thin layer of bearing grease to the hub surface and sensor 0-ring prior to sensor installation. Use ONLY Wheel Bearing Lubricant, P/N 01051344 (Canadian P/N 993037). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 02-05-25-006B > Jan > 06 > Brakes - Low Speed (Below 5 MPH) ABS Activation > Page 425 11. Install either the original sensor or a new one in the hub and secure the sensor. Ensure that the sensor is seated flush against the hub. 12. Install the rotor, the caliper and the wheel. 13. Place the DVM across the sensor terminals and recheck the voltage while rotating the wheel by hand. The voltage should now read at least 350 ACmV's. Parts Information Warranty Information For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheel Speed Sensor: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not Fuel Gauge Sender: All Technical Service Bulletins Instruments - Fuel Gauge Indicates Empty When Not File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-03A Date: June, 1998 Subject: Fuel Gauge Indicates Empty with 7-8 Gallons (30 Liters) Left in Tank (Replace Fuel Level Sensor Float Arm Assembly) Models: 1995-97 Chevrolet and GMC C/K 4 Door Models Built Prior to VIN Breakpoints: Models VIN Breakpoints Chevrolet VJ355982 GMC VJ724930 This bulletin is being revised to change the labor operation number. Please discard Corporate Bulletin Number 76-83-03 (Section 8 - Chassis/Body Electrical). Condition Some owners may comment that the fuel gauge indicates empty after only going 200 to 250 miles, and they are only able to put approximately 23 gallons or less of fuel in the 30 gallon tank. Cause The Fuel Level Indication System was designed with excessive empty reserve. The Fuel Level Sender will be labeled with Broadcast code "TCB", (see Figure 1). Vehicles built after December 14, 1996, have the revised Float Arm Assembly. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheel Speed Sensor: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not > Page 431 Following the procedure described in Section 8A of the Service Manual, remove the Sender Assembly and replace the original Float and Arm with P/N 25312833 (see Figure 2). Reinstall the Sender Assembly and Tank. Parts Information P/N Description Qty 25312833 Float Kit, Fuel Level Sensor 1 The part is currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time L1225 Sender Use published Assembly, Fuel Labor Operation (Tank Unit) - Time Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheel Speed Sensor: > 76-83-05 > Sep > 97 > Instruments - Excessive Fuel Gauge Fluctuation Fuel Gauge Sender: All Technical Service Bulletins Instruments - Excessive Fuel Gauge Fluctuation File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-05 Date: September, 1997 Subject: Excessive Fuel Gauge Fluctuation (Install Fuel Level Damper Kit) Models: 1995-97 Chevrolet and GMC C/K 4 Door Utility Models Condition Some owners may comment about excessive fuel gauge needle fluctuation when making turns or braking with less than a half tank of fuel. Correction Install fuel level damper module kit P/N 12167652 following the procedure described on the instruction sheets included with the kit. Parts Information P/N Description Qty 12167652 Module Kit, Fuel Level Damper 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time N4844 Module, Anti-slosh - Install 0.8 hr Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheel Speed Sensor: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not > Page 441 Following the procedure described in Section 8A of the Service Manual, remove the Sender Assembly and replace the original Float and Arm with P/N 25312833 (see Figure 2). Reinstall the Sender Assembly and Tank. Parts Information P/N Description Qty 25312833 Float Kit, Fuel Level Sensor 1 The part is currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time L1225 Sender Use published Assembly, Fuel Labor Operation (Tank Unit) - Time Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Technical Service Bulletins > Page 446 Wheel Speed Sensor: Specifications 2WD Sensor Resistance 1575 to 2420 ohms at -40 to 40 deg F 1980 to 2800 ohms at 41 to 110 deg F 2250 to 3280 ohms at 111 to 200 deg F 2750 to 3850 ohms at 201 to 302 deg F 4WD Sensor Resistance 1900 to 2950 ohms at -40 to 40 deg F 2420 to 3450 ohms at 41 to 110 deg F 2610 to 4100 ohms at 111 to 200 deg F 3320 to 4760 ohms at 201 to 302 deg F Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Locations > LH Wheel Speed Sensor: Locations LH front At LH front Wheel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Locations > LH > Page 449 Wheel Speed Sensor: Locations RH front At RH front Wheel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Service and Repair > Front Wheel Speed Sensor Wheel Speed Sensor: Service and Repair Front Wheel Speed Sensor 1. Raise and support vehicle, then remove wheel and tire assembly. 2. Disconnect brake caliper assembly and position aside. 3. Remove hub and rotor assembly. 4. Disconnect wheel sensor electrical connector. 5. Remove sensor wire form upper control arm clip. 6. Remove sensor and splash shield assembly attaching bolts, then remove sensor. 7. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Service and Repair > Front Wheel Speed Sensor > Page 452 Wheel Speed Sensor: Service and Repair Rear Wheel Speed Sensor Fig. 58 Rear Wheel Speed Sensor 1. Raise and support vehicle, then remove wheel and tire assembly. 2. Remove brake drum. 3. Remove primary brake shoe. 4. Disconnect sensor electrical connector. 5. Remove sensor wire from rear axle clip. 6. Remove speed sensor attaching bolts, Fig. 58, then remove sensor by pulling wire through hole in backing plate. 7. Reverse procedure to install. Torque speed sensor attaching bolts to 26 ft. lbs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > A/C Pressure Sensor/Switch - Cooling Fan > Component Information > Locations A/C Pressure Sensor/Switch - Cooling Fan: Locations Front of Engine Compartment, on Condenser Manifold Tubing Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Specifications Coolant Temperature Sensor/Switch (For Computer): Specifications Engine Coolant Temperature (ECT) sensor .............................................................................................................................................. 13 Nm (10 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Specifications > Page 461 Engine Side, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions Coolant Temperature Sensor/Switch (For Computer): Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 464 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 465 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 466 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 467 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 468 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 469 Coolant Temperature Sensor/Switch (For Computer): Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 470 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 471 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 472 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 473 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 474 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 475 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 476 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 477 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 478 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 479 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 480 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 481 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 482 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 483 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 484 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 485 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 486 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 487 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 488 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 489 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 490 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 491 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 492 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 493 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 494 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 495 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 496 ECT Sensor Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 497 Coolant Temperature Sensor/Switch (For Computer): Description and Operation Engine Coolant Temperature (ECT) Sensor DESCRIPTION The engine coolant temperature sensor is a thermistor (a resistor which changes value based on temperature) mounted in the engine coolant passage. Low coolant temperature produces a high resistance 100,000 ohms at -40°C (-40°F) while high temperature causes low resistance 70 ohms at 130°C (266°F). OPERATION The VCM supplies a 5 volt signal to the engine coolant temperature sensor through a resistor in the VCM and measures the voltage. The voltage will be high when the engine is cold. The voltage will be low when the engine is hot. By measuring the voltage, the VCM calculates the engine coolant temperature. Engine coolant temperature affects most systems the VCM controls. The scan tool displays engine coolant temperature in degrees. After engine start-up, the temperature should rise steadily to about 9O°C (194°F) then stabilize when thermostat opens. If the engine has not been run for several hours (overnight), the engine coolant temperature and intake air temperature displays should be close to each other. When the VCM detects a malfunction in the Engine Coolant Temperature (ECT) sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0117 circuit low. ^ DTC P0118 circuit high. ^ DTC P0125 excessive time to Closed Loop. ^ DTC P1114 circuit intermittent low. ^ DTC P1115 circuit intermittent high. The above DTCs contain a table to check for sensor resistance values relative to temperature. Refer to Specifications. See: Powertrain Management/Computers and Control Systems/Specifications Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 498 Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection The scan tool displays engine coolant temperature in degrees. After engine start-up, the temperature should rise steadily to about 90°C (194°F) then stabilize when thermostat opens. If the engine has not been run for several hours (overnight), the engine coolant temperature and intake air temperature displays should be close to each other. When the VCM detects a malfunction in the Engine Coolant Temperature (ECT) sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0117 circuit low. ^ DTC P0118 circuit high. ^ DTC P0125 excessive time to Closed Loop. ^ DTC P1114 circuit intermittent low. ^ DTC P1115 circuit intermittent high. The above DTCs contain a table to check for sensor resistance values relative to temperature. Refer to Diagnostic Tables. See: Powertrain Management/Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 499 Coolant Temperature Sensor/Switch (For Computer): Service and Repair Engine Coolant Temperature (ECT) Sensor Electrical Connector Engine Coolant Temperature (ECT) Sensor CAUTION: Use care when handling the coolant sensor. Damage to the coolant sensor will affect the operation of the fuel control system. REMOVAL PROCEDURE 1. Relieve the coolant pressure. 2. Disconnect the negative battery cable. 3. Drain the cooling system below the level of the sensor. 4. Disconnect the electrical connector releasing locking tab. 5. Remove the coolant sensor from engine. INSTALLATION PROCEDURE 1. Coat the threads (only) with sealer P/N 9985253 or equivalent. Tighten ^ Tighten the sensor to 13 N.m (10 lb. ft.). 2. Install the coolant sensor in the engine. 3. Connect the electrical connector. 4. Refill the cooling system. 5. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Temperature Sensor (Gauge) > Component Information > Locations Temperature Sensor (Gauge): Locations Engine Side, LH LH cylinder head, near number one spark plug. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Locations Instrument Panel Wiring, LH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions Brake Switch (Cruise Control): Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 509 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 510 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 511 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 512 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 513 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 514 Brake Switch (Cruise Control): Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 515 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 516 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 517 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 518 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 519 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 520 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 521 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 522 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 523 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 524 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 525 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 526 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 527 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 528 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 529 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 530 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 531 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 532 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 533 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 534 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 535 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 536 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 537 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 538 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 539 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 540 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Description and Operation > Electric Brake Release Switch Brake Switch (Cruise Control): Description and Operation Electric Brake Release Switch The brake pedal is equipped with two switches: a combination stop light/cruise control/TCC switch and a plunger type release switch. Each switch disengages the cruise control system when the brake pedal is depressed. When the brake pedal is released, the system will remain disengaged. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Locations Clutch Switch: Locations At the top of the Clutch Pedal. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions Clutch Switch: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 548 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 549 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 550 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 551 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 552 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 553 Clutch Switch: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 554 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 555 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 556 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 557 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 558 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 559 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 560 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 561 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 562 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 563 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 564 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 565 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 566 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 567 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 568 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 569 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 570 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 571 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 572 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 573 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 574 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 575 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 576 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 577 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 578 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 579 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Description and Operation > Electric Clutch Release Switch Clutch Switch: Description and Operation Electric Clutch Release Switch Fig. 3 Electric clutch release switch On models equipped with manual transmission, a plunger type clutch switch, Fig. 3, is used in series with the two brake switches. The switch disengages the cruise control system when the clutch pedal is depressed. When the clutch pedal is released, the system will remain disengaged. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Locations Cruise Control Switch: Locations Steering Column Wiring At the turn signal lever. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions Cruise Control Switch: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 587 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 588 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 589 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 590 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 591 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 592 Cruise Control Switch: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 593 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 594 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 595 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 596 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 597 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 598 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 599 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 600 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 601 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 602 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 603 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 604 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 605 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 606 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 607 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 608 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 609 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 610 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 611 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 612 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 613 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 614 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 615 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 616 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 617 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 618 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Page 619 Cruise Control Switch: Service and Repair 1. Disconnect battery ground cable. Fig. 38 Cruise Control Switch Replacement. 2. Remove cruise control switch protector cover, Fig. 38. 3. Disconnect switch electrical connector, then remove the switch and cruise control wire. 4. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Locations Instrument Panel Wiring, RH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions Vehicle Speed Sensor/Transducer - Cruise Control: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 625 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 626 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 627 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 628 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 629 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 630 Vehicle Speed Sensor/Transducer - Cruise Control: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 631 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 632 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 633 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 634 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 635 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 636 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 637 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 638 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 639 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 640 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 641 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 642 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 643 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 644 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 645 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 646 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 647 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 648 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 649 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 650 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 651 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 652 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 653 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 654 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 655 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 656 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Engine > Oil Pressure Sender > Component Information > Locations Oil Pressure Sender: Locations LH side of Engine, rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Engine > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Fuel Pump Oil Pressure Switch and Sender Engine View, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Engine > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Fuel Pump Oil Pressure Switch and Sender > Page 665 Oil Pressure Switch (For Fuel Pump): Locations Oil Pressure Switch and Sender LH side of Engine, rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Engine > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Page 666 Fuel Pump Oil Pressure Switch And Sender Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Engine > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Page 667 Oil Pressure Switch (For Fuel Pump): Service and Repair Oil Pressure Switch Electrical Connector Oil Pressure Switch REMOVAL PROCEDURE 1. Remove the electrical connector. 2. Remove the fuel pump and oil pressure indicator switch, using wrench J 35748 it required. INSTALLATION PROCEDURE 1. Install the fuel pump and oil pressure indicator switch. 2. Install the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - HVAC > Air Conditioning Switch > Component Information > Locations > Auxiliary Heater Control Switch, Rear Air Conditioning Switch: Locations Auxiliary Heater Control Switch, Rear I/P, Right of Steering Column Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - HVAC > Air Conditioning Switch > Component Information > Locations > Auxiliary Heater Control Switch, Rear > Page 673 Air Conditioning Switch: Locations Rear Auxiliary Heater Control Switch in Headliner Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - HVAC > Air Conditioning Switch > Component Information > Locations > Auxiliary Heater Control Switch, Rear > Page 674 Air Conditioning Switch: Locations Rear Auxiliary Heater/A/C Fan Switch in Headliner Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - HVAC > Air Conditioning Switch > Component Information > Diagrams > Heater and A/C Control Switch Air Conditioning Switch: Diagrams Heater and A/C Control Switch C1: Heater And A/C Control Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - HVAC > Air Conditioning Switch > Component Information > Diagrams > Heater and A/C Control Switch > Page 677 C3: Heater And A/C Control Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - HVAC > Air Conditioning Switch > Component Information > Diagrams > Heater and A/C Control Switch > Page 678 C300: Rear Body HARN To AUX. A/C Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - HVAC > Air Conditioning Switch > Component Information > Diagrams > Heater and A/C Control Switch > Page 679 C401: Rear Body HARN To AUX A/C Switch HARN Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - HVAC > Blower Motor Switch > Component Information > Locations > Aux Fan Control Switch C227: TCC/Stop Lamp Switch Jumper, AUX Fan Control Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - HVAC > Blower Motor Switch > Component Information > Locations > Aux Fan Control Switch > Page 684 Blower Motor Switch: Locations Fan Switch, Front At heater control. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - HVAC > Blower Motor Switch > Component Information > Locations > Aux Fan Control Switch > Page 685 Cargo Lamp Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - HVAC > Blower Motor Switch > Component Information > Locations > Page 686 C2: Heater Blower Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - HVAC > Blower Motor Switch > Component Information > Service and Repair > With Air Conditioning Blower Motor Switch: Service and Repair With Air Conditioning Control Assembly Remove or Disconnect 1. Instrument cluster trim. 2. Control assembly. - Release the retainers using a small screwdriver, then pull the control assembly out from the instrument panel. 3. Electrical connectors, as necessary. Install or Connect 1. Electrical connectors, as necessary. 2. Control assembly. - The control assembly snap-fits to the instrument panel. 3. Instrument cluster trim. Check circuit operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - HVAC > Blower Motor Switch > Component Information > Service and Repair > With Air Conditioning > Page 689 Blower Motor Switch: Service and Repair W/O Air Conditioning Control Assembly Replacment Remove or Disconnect 1. Instrument cluster trim plate. 2. Control assembly by releasing the snap-fit retainers with a small screwdriver. 3. Electrical connection. 4. Cables from the control assembly by releasing retainers. 5. Blower switch. Remove the blower switch rotary knob and the retaining clip from the shaft of the blower switch. Install or Connect 1. Blower switch. A. Hold the blower switch in position and install the retaining clip. B. Install the blower switch rotary knob. 2. Cables to the control assembly. 3. Electrical connection. 4. Control assembly to the instrument panel by snapping in. 5. Instrument cluster trim plate. Check circuit operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - HVAC > Refrigerant Pressure Sensor / Switch, HVAC > A/C Pressure Sensor/Switch - Cooling Fan > Component Information > Locations A/C Pressure Sensor/Switch - Cooling Fan: Locations Front of Engine Compartment, on Condenser Manifold Tubing Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Instrument Panel > Dimmer Switch > Component Information > Technical Service Bulletins > IP Dimmer Control - Proper Setting Dimmer Switch: Technical Service Bulletins IP Dimmer Control - Proper Setting File In Section: 08 - Body and Accessories Bulletin No.: 99-08-42-009 Date: November, 1999 INFORMATION Subject: Proper Setting of I/P Dimmer Control to View PRNDL Display with Automatic Headlamp Control Models: 2000 and Prior All Passenger Cars and Trucks With Automatic Headlamp Control and Electronic PRNDL Display Under certain conditions, if the instrument panel dimmer control is turned relatively low, the PRNDL will not be visible until the automatic headlamp control turns the headlamps off and the daytime running lamps (DRL) are turned back on. Such a condition may be if the vehicle is first started in an environment where the headlamp control turns on the headlamps and then the vehicle is driven out into a brighter environment (for example, when a vehicle is backed out of a dark garage into the bright sunlight). This condition is normal and any repair attempt will not be successful. Demonstrate this condition to the customer using the service lane and then turn the instrument panel dimmer control to a higher setting. This will enable the driver to see the PRNDL display Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Instrument Panel > Door Switch > Component Information > Locations > Cargo Door Jamb Switch Door Switch: Locations Cargo Door Jamb Switch On RH rear Cargo Door Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Instrument Panel > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 703 Door Switch: Locations Door Jamb Switch, Cargo Upper RH Body Opening incorporated in Cargo Door Contractor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Instrument Panel > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 704 Door Switch: Locations Door Jamb Switch, LH Front At LH end of I/P Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Instrument Panel > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 705 Door Switch: Locations Door Jamb Switch, LH Rear Center of LH "B" Pillar Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Instrument Panel > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 706 Door Switch: Locations Cargo Door Jamb Switch On RH rear Cargo Door Door Jamb Switch, Cargo Upper RH Body Opening incorporated in Cargo Door Contractor Door Jamb Switch, LH Front At LH end of I/P Door Jamb Switch, LH Rear Center of LH "B" Pillar Rear Door Jamb Switch Wiring Door Jamb Switch, RH Front At RH end of I/P Door Jamb Switch, RH Rear Center of RH "B" Pillar Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Instrument Panel > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Customer Interest for Fuel Gauge Sender: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not Fuel Gauge Sender: Customer Interest Instruments - Fuel Gauge Indicates Empty When Not File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-03A Date: June, 1998 Subject: Fuel Gauge Indicates Empty with 7-8 Gallons (30 Liters) Left in Tank (Replace Fuel Level Sensor Float Arm Assembly) Models: 1995-97 Chevrolet and GMC C/K 4 Door Models Built Prior to VIN Breakpoints: Models VIN Breakpoints Chevrolet VJ355982 GMC VJ724930 This bulletin is being revised to change the labor operation number. Please discard Corporate Bulletin Number 76-83-03 (Section 8 - Chassis/Body Electrical). Condition Some owners may comment that the fuel gauge indicates empty after only going 200 to 250 miles, and they are only able to put approximately 23 gallons or less of fuel in the 30 gallon tank. Cause The Fuel Level Indication System was designed with excessive empty reserve. The Fuel Level Sender will be labeled with Broadcast code "TCB", (see Figure 1). Vehicles built after December 14, 1996, have the revised Float Arm Assembly. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Instrument Panel > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Customer Interest for Fuel Gauge Sender: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not > Page 715 Following the procedure described in Section 8A of the Service Manual, remove the Sender Assembly and replace the original Float and Arm with P/N 25312833 (see Figure 2). Reinstall the Sender Assembly and Tank. Parts Information P/N Description Qty 25312833 Float Kit, Fuel Level Sensor 1 The part is currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time L1225 Sender Use published Assembly, Fuel Labor Operation (Tank Unit) - Time Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Instrument Panel > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Customer Interest for Fuel Gauge Sender: > 76-83-05 > Sep > 97 > Instruments - Excessive Fuel Gauge Fluctuation Fuel Gauge Sender: Customer Interest Instruments - Excessive Fuel Gauge Fluctuation File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-05 Date: September, 1997 Subject: Excessive Fuel Gauge Fluctuation (Install Fuel Level Damper Kit) Models: 1995-97 Chevrolet and GMC C/K 4 Door Utility Models Condition Some owners may comment about excessive fuel gauge needle fluctuation when making turns or braking with less than a half tank of fuel. Correction Install fuel level damper module kit P/N 12167652 following the procedure described on the instruction sheets included with the kit. Parts Information P/N Description Qty 12167652 Module Kit, Fuel Level Damper 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time N4844 Module, Anti-slosh - Install 0.8 hr Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Instrument Panel > Fuel Gauge Sender > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Gauge Sender: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not Fuel Gauge Sender: All Technical Service Bulletins Instruments - Fuel Gauge Indicates Empty When Not File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-03A Date: June, 1998 Subject: Fuel Gauge Indicates Empty with 7-8 Gallons (30 Liters) Left in Tank (Replace Fuel Level Sensor Float Arm Assembly) Models: 1995-97 Chevrolet and GMC C/K 4 Door Models Built Prior to VIN Breakpoints: Models VIN Breakpoints Chevrolet VJ355982 GMC VJ724930 This bulletin is being revised to change the labor operation number. Please discard Corporate Bulletin Number 76-83-03 (Section 8 - Chassis/Body Electrical). Condition Some owners may comment that the fuel gauge indicates empty after only going 200 to 250 miles, and they are only able to put approximately 23 gallons or less of fuel in the 30 gallon tank. Cause The Fuel Level Indication System was designed with excessive empty reserve. The Fuel Level Sender will be labeled with Broadcast code "TCB", (see Figure 1). Vehicles built after December 14, 1996, have the revised Float Arm Assembly. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Instrument Panel > Fuel Gauge Sender > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Gauge Sender: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not > Page 725 Following the procedure described in Section 8A of the Service Manual, remove the Sender Assembly and replace the original Float and Arm with P/N 25312833 (see Figure 2). Reinstall the Sender Assembly and Tank. Parts Information P/N Description Qty 25312833 Float Kit, Fuel Level Sensor 1 The part is currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time L1225 Sender Use published Assembly, Fuel Labor Operation (Tank Unit) - Time Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Instrument Panel > Fuel Gauge Sender > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Gauge Sender: > 76-83-05 > Sep > 97 > Instruments - Excessive Fuel Gauge Fluctuation Fuel Gauge Sender: All Technical Service Bulletins Instruments - Excessive Fuel Gauge Fluctuation File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-05 Date: September, 1997 Subject: Excessive Fuel Gauge Fluctuation (Install Fuel Level Damper Kit) Models: 1995-97 Chevrolet and GMC C/K 4 Door Utility Models Condition Some owners may comment about excessive fuel gauge needle fluctuation when making turns or braking with less than a half tank of fuel. Correction Install fuel level damper module kit P/N 12167652 following the procedure described on the instruction sheets included with the kit. Parts Information P/N Description Qty 12167652 Module Kit, Fuel Level Damper 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time N4844 Module, Anti-slosh - Install 0.8 hr Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Instrument Panel > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Page 730 Fuel Gauge Sender: Locations In rear Fuel Tank Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Instrument Panel > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Page 731 Fuel Gage Sender (Auxiliary Fuel Tank) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Instrument Panel > Key Reminder Switch > Component Information > Locations Key Reminder Switch: Locations In Steering Column Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Backup Lamp Switch > Component Information > Locations Backup Lamp Switch: Locations 5-Speed Manual Transmission (MW3) 5-Speed Manual Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Locations Brake Light Switch: Locations This article has been updated with Bulletin No.: 76-81-06. TCC/STOPLAMP SWITCH The TCC/Stoplamp Switch at top of Brake Pedal. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions Brake Light Switch: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 744 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 745 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 746 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 747 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 748 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 749 Brake Light Switch: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 750 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 751 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 752 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 753 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 754 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 755 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 756 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 757 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 758 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 759 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 760 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 761 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 762 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 763 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 764 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 765 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 766 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 767 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 768 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 769 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 770 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 771 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 772 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 773 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 774 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 775 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 776 Brake Light Switch: Electrical Diagrams Antilock Brakes Four Wheel Antilock Brakes (4WAL) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 777 Fig. 25 Four Wheel Anti-Lock Brake Wiring Circuit. Four wheel anti-lock brake wiring circuit. Additional Wiring Diagrams For additional Lighting and Horns wiring diagrams, See: Lighting and Horns/Diagrams/Electrical Diagrams Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 778 Brake Switch And Solenoids Cruise Control Wiring Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 779 Fig. 9 Cruise Control System Wiring Circuit (Part 1 Of 2). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 780 Fig. 9 Cruise Control System Wiring Circuit (Part 2 Of 2). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 781 Turn And Hazard Lamps/Park And Marker Lamps (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 782 Antilock Brakes Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 783 Turn And Hazard Lamps/Park And Marker Lamps (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 784 Turn And Hazard Lamps/Park And Marker Lamps (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 785 Cruise Control (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Page 786 Brake Light Switch: Adjustments Stop Lamp Switch Remove or Disconnect 1. Negative battery cable. 2. Disable SIR. 3. Retainer from brake pedal pin. Use snap ring pliers. 4. Switch by unsnapping from pushrod. 5. Electrical connector from switch. Install or Connect 1. Electrical connector into switch. 2. Switch by snapping it onto pushrod. 3. Retainer onto brake pedal pin. Use 11mm (7/16 inch) socket to push new clip on pin. 4. Negative battery cable. 5. Enable SIR. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Page 787 Brake Light Switch: Service and Repair Stop Lamp Switch Remove or Disconnect 1. Negative battery cable. 2. Disable SIR. 3. Retainer from brake pedal pin. Use snap ring pliers. 4. Switch by unsnapping from pushrod. 5. Electrical connector from switch. Install or Connect 1. Electrical connector into switch. 2. Switch by snapping it onto pushrod. 3. Retainer onto brake pedal pin. Use 11mm (7/16 inch) socket to push new clip on pin. 4. Negative battery cable. 5. Enable SIR. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Cargo Lamp Switch > Component Information > Locations Cargo Lamp Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Cargo Lamp Switch > Component Information > Locations > Page 791 Cargo Lamp Switch: Diagrams C411: Cross Body HARN To Cargo Lamp HARN C212: PWR Seat To Cross Body HARN, Body HARN To Cross Body HARN, Cargo Lamp SW Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Dome Lamp Switch > Component Information > Locations Dome Lamp Switch: Locations On center of I/P Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Door Switch > Component Information > Locations > Cargo Door Jamb Switch Door Switch: Locations Cargo Door Jamb Switch On RH rear Cargo Door Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 799 Door Switch: Locations Door Jamb Switch, Cargo Upper RH Body Opening incorporated in Cargo Door Contractor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 800 Door Switch: Locations Door Jamb Switch, LH Front At LH end of I/P Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 801 Door Switch: Locations Door Jamb Switch, LH Rear Center of LH "B" Pillar Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 802 Door Switch: Locations Cargo Door Jamb Switch On RH rear Cargo Door Door Jamb Switch, Cargo Upper RH Body Opening incorporated in Cargo Door Contractor Door Jamb Switch, LH Front At LH end of I/P Door Jamb Switch, LH Rear Center of LH "B" Pillar Rear Door Jamb Switch Wiring Door Jamb Switch, RH Front At RH end of I/P Door Jamb Switch, RH Rear Center of RH "B" Pillar Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Fog/Driving Lamp Switch > Component Information > Locations Cargo Lamp Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Fog/Driving Lamp Switch > Component Information > Locations > Page 806 Fog Lamp Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Headlamp Dimmer Switch > Component Information > Locations > Component Locations Headlamp Dimmer Switch: Component Locations Part of the multifunction switch. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Headlamp Dimmer Switch > Component Information > Locations > Component Locations > Page 811 Instrument Panel Wiring, LH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Headlamp Dimmer Switch > Component Information > Locations > Page 812 Headlamp Dimmer Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Horn Switch > Component Information > Locations Horn Switch: Locations Top of Steering Column under Steering Wheel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Horn Switch > Component Information > Service and Repair > Horn Contact Replacement (Plunger Switch) Horn Switch: Service and Repair Horn Contact Replacement (Plunger Switch) REMOVAL Remove or disconnect the following: 1. Negative battery cable. 2. Disable the SIR system. See: Body and Frame/Interior Moulding / Trim/Dash Board / Instrument Panel/Air Bag(s) Arming and Disarming/Service and Repair 3. Inflator module. See: Restraint Systems/Air Bag Systems/Air Bag/Service and Repair 4. Horn contact from steering column. See: INSTALLATION CAUTION: Always use the correct fastener in the proper location. When you replace a fastener, use ONLY the exact part number for that application. The manufacturer will call out those fasteners that require a replacement after removal. The manufacturer will also call out the fasteners that require thread lockers or thread sealant. UNLESS OTHERWISE SPECIFIED, do not use supplemental coatings (paints, greases, or other corrosion Inhibitors) on threaded fasteners or fastener joint interfaces. Generally, such coatings adversely affect the fastener torque and joint clamping force, and may damage the fastener. When you install fasteners, use the correct tightening sequence and specifications. Following these instructions can help you avoid damage to parts and systems. Install or connect the following: 1. Horn contact into steering column. See: 2. Inflator module to the steering wheel. See: Restraint Systems/Air Bag Systems/Air Bag/Service and Repair 3. Negative battery cable. 4. Enable the SIR system. See: Body and Frame/Interior Moulding / Trim/Dash Board / Instrument Panel/Air Bag(s) Arming and Disarming/Service and Repair Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Horn Switch > Component Information > Service and Repair > Horn Contact Replacement (Plunger Switch) > Page 818 Horn Switch: Service and Repair Horn Pad Assembly Replacement REMOVAL Remove or disconnect the following: 1. Negative battery cable. 2. Pull four corners of horn pad from steering wheel. 3. Ground wire. 4. Horn wire assembly. INSTALLATION Install or connect the following: 1. Horn wire assembly. 2. Ground wire. 3. Push horn pad assembly on steering wheel. 4. Negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Turn Signal Switch > Component Information > Diagrams > C266 Harness Connector C266: I/P Harness To Steering Column Harness Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Turn Signal Switch > Component Information > Diagrams > C266 Harness Connector > Page 823 Turn Signal Switch: Diagrams C266 Pinout Description C266: I/P Harness To Steering Column Harness (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Lighting and Horns > Turn Signal Switch > Component Information > Diagrams > C266 Harness Connector > Page 824 C266: I/P Harness To Steering Column Harness (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions Mass Air Flow (MAF) Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 831 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 832 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 833 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 834 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 835 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 836 Mass Air Flow (MAF) Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 837 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 838 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 839 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 840 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 841 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 842 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 843 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 844 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 845 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 846 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 847 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 848 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 849 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 850 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 851 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 852 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 853 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 854 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 855 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 856 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 857 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 858 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 859 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 860 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 861 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 862 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 863 Mass Air Flow System Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Page 864 Mass Air Flow (MAF) Sensor: Description and Operation Mass Air Flow (MAF) Sensor The Mass Air Flow (MAF) sensor measures the amount of air which passes through it. The VCM uses this information to determine the operating condition of the engine, to control fuel delivery. A large quantity of air indicates acceleration. A small quantity of air indicates deceleration or idle. The scan tool reads the MAF value and displays it in grams per second (gm/Sec). At idle, it should read between 5-7 gm/Sec on a fully warmed up engine. Values should change rather quickly on acceleration, but values should remain fairly stable at any given RPM. When the VCM detects a malfunction in the MAF sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0101 system performance. ^ DTC P0102 frequency low. ^ DTC P0103 frequency high. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Page 865 Mass Air Flow (MAF) Sensor: Service and Repair MAF Sensor MAF Sensor Intake Duct REMOVAL PROCEDURE CAUTION: Take care when handling the Mass Air Flow (MAF). Do Not dent, puncture, or otherwise damage the honeywell located at the air inlet end of the MAF. Do Not touch the sensing elements or allow anything (including solvents and lubricants) to come in contact with them. A small amount of GM lubricant (P/N 99855406) may be used on the air duct only to aid in installation. Do Not drop or roughly handle the MAF. 1. Disconnect the 3 wire electrical connector. 2. Loosen the clamp on the intake duct. 3. Carefully remove the MAF sensor. INSTALLATION PROCEDURE 1. Install the MAF sensor. 2. Install the intake ducts. 3. Tighten the clamp. 4. Connect the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Camshaft Position Sensor: Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 870 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 871 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 872 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 873 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 874 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 875 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 876 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Page 877 Camshaft Position Sensor: Specifications Camshaft position sensor retaining screw ........................................................................................................................................... 4-6 Nm (35-53 lb. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Page 878 Engine View, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Camshaft Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 881 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 882 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 883 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 884 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 885 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 886 Camshaft Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 887 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 888 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 889 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 890 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 891 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 892 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 893 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 894 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 895 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 896 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 897 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 898 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 899 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 900 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 901 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 902 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 903 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 904 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 905 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 906 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 907 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 908 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 909 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 910 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 911 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 912 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Page 913 Camshaft Position Sensor: Description and Operation Camshaft Position Sensor The Camshaft Position (CMP) sensor is located within the distributor. It's operation is very similar to the Crankshaft Position (CKP) sensor however it will provide one pulse per camshaft revolution (1x signal). This signal is not detrimental to the driveability of the vehicle. The Vehicle Control Module (VCM) utilizes this signal in conjunction with the crankshaft position to determine which cylinder(s) are misfiring. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Testing and Inspection > Cam Signal Camshaft Position Sensor: Testing and Inspection Cam Signal The VCM uses this signal to determine the position of the #1 piston during its power stroke. This signal is used by the VCM to calculate fuel injection mode of operation. A loss of this signal will set DTC P0340. If the cam signal is lost while the engine is running, the fuel injection system will shift to a calculated fuel injection mode based on the last fuel injection pulse, and the engine will continue to run. The engine can be restarted and will run in the calculated mode as long as the fault is present Refer to Diagnostic Trouble Code (DTC) P0340 Camshaft Position Sensor (CKP) Sensor Circuit. See: Powertrain Management/Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Testing and Inspection > Page 916 Camshaft Position Sensor: Service and Repair REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Disconnect the electrical connector from the camshaft position sensor. 3. Remove the camshaft position sensor retaining screw. 4. Remove the camshaft position sensor. INSTALLATION PROCEDURE 1. Install the camshaft position sensor. 2. Install the camshaft position sensor retaining screw, torque to 4-6 Nm (35-53 lb. in.). 3. Connect the electrical connector. 4. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Specifications Coolant Temperature Sensor/Switch (For Computer): Specifications Engine Coolant Temperature (ECT) sensor .............................................................................................................................................. 13 Nm (10 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Specifications > Page 920 Engine Side, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions Coolant Temperature Sensor/Switch (For Computer): Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 923 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 924 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 925 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 926 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 927 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 928 Coolant Temperature Sensor/Switch (For Computer): Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 929 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 930 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 931 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 932 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 933 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 934 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 935 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 936 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 937 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 938 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 939 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 940 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 941 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 942 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 943 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 944 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 945 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 946 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 947 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 948 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 949 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 950 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 951 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 952 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 953 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 954 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 955 ECT Sensor Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 956 Coolant Temperature Sensor/Switch (For Computer): Description and Operation Engine Coolant Temperature (ECT) Sensor DESCRIPTION The engine coolant temperature sensor is a thermistor (a resistor which changes value based on temperature) mounted in the engine coolant passage. Low coolant temperature produces a high resistance 100,000 ohms at -40°C (-40°F) while high temperature causes low resistance 70 ohms at 130°C (266°F). OPERATION The VCM supplies a 5 volt signal to the engine coolant temperature sensor through a resistor in the VCM and measures the voltage. The voltage will be high when the engine is cold. The voltage will be low when the engine is hot. By measuring the voltage, the VCM calculates the engine coolant temperature. Engine coolant temperature affects most systems the VCM controls. The scan tool displays engine coolant temperature in degrees. After engine start-up, the temperature should rise steadily to about 9O°C (194°F) then stabilize when thermostat opens. If the engine has not been run for several hours (overnight), the engine coolant temperature and intake air temperature displays should be close to each other. When the VCM detects a malfunction in the Engine Coolant Temperature (ECT) sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0117 circuit low. ^ DTC P0118 circuit high. ^ DTC P0125 excessive time to Closed Loop. ^ DTC P1114 circuit intermittent low. ^ DTC P1115 circuit intermittent high. The above DTCs contain a table to check for sensor resistance values relative to temperature. Refer to Specifications. See: Powertrain Management/Computers and Control Systems/Specifications Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 957 Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection The scan tool displays engine coolant temperature in degrees. After engine start-up, the temperature should rise steadily to about 90°C (194°F) then stabilize when thermostat opens. If the engine has not been run for several hours (overnight), the engine coolant temperature and intake air temperature displays should be close to each other. When the VCM detects a malfunction in the Engine Coolant Temperature (ECT) sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0117 circuit low. ^ DTC P0118 circuit high. ^ DTC P0125 excessive time to Closed Loop. ^ DTC P1114 circuit intermittent low. ^ DTC P1115 circuit intermittent high. The above DTCs contain a table to check for sensor resistance values relative to temperature. Refer to Diagnostic Tables. See: Powertrain Management/Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 958 Coolant Temperature Sensor/Switch (For Computer): Service and Repair Engine Coolant Temperature (ECT) Sensor Electrical Connector Engine Coolant Temperature (ECT) Sensor CAUTION: Use care when handling the coolant sensor. Damage to the coolant sensor will affect the operation of the fuel control system. REMOVAL PROCEDURE 1. Relieve the coolant pressure. 2. Disconnect the negative battery cable. 3. Drain the cooling system below the level of the sensor. 4. Disconnect the electrical connector releasing locking tab. 5. Remove the coolant sensor from engine. INSTALLATION PROCEDURE 1. Coat the threads (only) with sealer P/N 9985253 or equivalent. Tighten ^ Tighten the sensor to 13 N.m (10 lb. ft.). 2. Install the coolant sensor in the engine. 3. Connect the electrical connector. 4. Refill the cooling system. 5. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-014 > Apr > 00 > Engine - No/Hard/Slow Start/Backfire/Kickback Crankshaft Position Sensor: Customer Interest Engine - No/Hard/Slow Start/Backfire/Kickback File In Section: 06 - Engine/Propulsion System Bulletin No.: 00-06-04-014 Date: April, 2000 TECHNICAL Subject: No, Hard, or Slow Start, Backfire or "Kickback" During Crank/Start, "Grinding" or Unusual Noises During Crank, DTC P0338 (Replace Crankshaft Position Sensor) Models: 1999-2000 Cadillac Escalade 1995-2000 Chevrolet and GMC SIT Models 1996-2000 Chevrolet and GMC C/K, M/L, G, P Models 1996-2000 Oldsmobile Bravada with 4.3 L, 5.0 L, 5.7 L or 7.4 L Engine (VINs W, X, M, R, J RPOs L35, LF6, L30, L31, L29) Condition: Some customers may comment on one or more of the following conditions: ^ Backfire during crank/start ^ "Kickback" during crank/start ^ "No" start ^ "Slow" or "hard" start/crank ^ "Grinding" or unusual noises during crank/start ^ Cracked or broken engine block at the starter boss ^ Broken starter drive housing ^ Broken starter ring gear on flywheel ^ Any combination of the above Cause: A condition may exist that allows the crankshaft position sensor to command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss. Correction: Inspect for a stored powertrain DTC code P0338. This DTC will NOT illuminate the "Service Engine Soon" light. If this code is stored, the Crankshaft Position Sensor, P/N 10456607, MUST be replaced and the remaining components inspected for damage (engine block at the starter boss, the starter drive housing, and the engine flywheel starter ring gear). Notice: When DTC code P0338 is set, failure to replace the Crankshaft Position Sensor could result in repeated inoperative conditions of the starter or flywheel. Important: Some flywheel wear is normal; broken or missing teeth and/or cracks, are not normal. Parts Information Parts are currently available from GMSPO. Warranty Information: For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 00-06-04-014 > Apr > 00 > Engine - No/Hard/Slow Start/Backfire/Kickback Crankshaft Position Sensor: All Technical Service Bulletins Engine - No/Hard/Slow Start/Backfire/Kickback File In Section: 06 - Engine/Propulsion System Bulletin No.: 00-06-04-014 Date: April, 2000 TECHNICAL Subject: No, Hard, or Slow Start, Backfire or "Kickback" During Crank/Start, "Grinding" or Unusual Noises During Crank, DTC P0338 (Replace Crankshaft Position Sensor) Models: 1999-2000 Cadillac Escalade 1995-2000 Chevrolet and GMC SIT Models 1996-2000 Chevrolet and GMC C/K, M/L, G, P Models 1996-2000 Oldsmobile Bravada with 4.3 L, 5.0 L, 5.7 L or 7.4 L Engine (VINs W, X, M, R, J RPOs L35, LF6, L30, L31, L29) Condition: Some customers may comment on one or more of the following conditions: ^ Backfire during crank/start ^ "Kickback" during crank/start ^ "No" start ^ "Slow" or "hard" start/crank ^ "Grinding" or unusual noises during crank/start ^ Cracked or broken engine block at the starter boss ^ Broken starter drive housing ^ Broken starter ring gear on flywheel ^ Any combination of the above Cause: A condition may exist that allows the crankshaft position sensor to command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss. Correction: Inspect for a stored powertrain DTC code P0338. This DTC will NOT illuminate the "Service Engine Soon" light. If this code is stored, the Crankshaft Position Sensor, P/N 10456607, MUST be replaced and the remaining components inspected for damage (engine block at the starter boss, the starter drive housing, and the engine flywheel starter ring gear). Notice: When DTC code P0338 is set, failure to replace the Crankshaft Position Sensor could result in repeated inoperative conditions of the starter or flywheel. Important: Some flywheel wear is normal; broken or missing teeth and/or cracks, are not normal. Parts Information Parts are currently available from GMSPO. Warranty Information: For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Crankshaft Position Sensor: All Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 976 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 977 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 978 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 979 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 980 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 981 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 982 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder Control Module: All Technical Service Bulletins A/T - Upshift Flare/No 3rd or 4th/Launch Shudder File In Section: 07 - Transmission/Transaxle Bulletin No.: 00-07-30-026 Date: December 2000 TECHNICAL Subject: Automatic Transmission 1-2 and/or 2-3 Upshift Slip/Flare, No 3rd or 4th gear, Launch Shudder (Revise VCM Wiring) Models: 1996 Chevrolet and GMC C/K, S/T, M/L, G1, G2, P3 Models 1996 Oldsmobile Bravada with VCM and 4L60-E (M30) or 4L80-E (MT1) Automatic Transmission This bulletin is being reissued to ensure that correct procedures are followed for this condition. Please discard Corporate Bulletin Number 66-71-03A (Section 7 - Automatic Transmission). When performing a transmission replacement labor operation K7000 on these vehicles with a 4L60-E or 4L80-E, you must include front chassis wire repair labor operation N6112. Inspect the VCM to verify the latest part number revision (16244210). Condition Some owners may comment that the automatic transmission has either a slip or flare on the 1-2 and/or 2-3 upshift, or no 3rd or 4th gear, or launch shudder. Upon investigation, the technician may find a DTC P1870 stored in the VCM. Cause A poor internal ground between the two circuit boards of the VCM may cause the VCM to command erratic line pressure at the pressure control (PC) solenoid valve. Correction Using harness jumper wire and instruction kit, P/N 12167310, revise the wiring harness at the VCM connector. Corrections were made to the VCM beginning 2/14/96. The corrected VCMs are identified with service number 16244210 on the VCM identification label. Procedure The following is a summary of the instructions included with the service kit: 1. Remove the negative terminal from the battery. 2. Move the wire located at connector J3 (WHITE/GREY/CLEAR), pin 18 to connector J1 (BLUE), pin 23. 3. Install the jumper wire between connector J2 (RED), pin 26 and connector J3 (WHITE/GREY/CLEAR), pin 18. 4. Install the tag included in the kit around the. VCM wiring harness. This tag notes that the wiring harness has been modified. 5. Reconnect the negative battery terminal. Road test to verify that the condition has been corrected. If any of the following conditions are noted, the transmission should be repaired or replaced using the most cost effective method. Canadian dealers should repair the transmission. ^ Transmission fluid oxidation or excessive sediment. ^ Transmission slip or flare after this service fix is performed. ^ DTC P1870 is stored on a 4L60-E (M30). The following tools are available from Kent-Moore (1-800-345-2233) for use in removing and relocating the VCM wires: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder > Page 988 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder > Page 994 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Page 995 Crankshaft Position Sensor: Specifications Crankshaft Position Sensor mounting bolts ................................................................................................................................................. 8 Nm (71 lb. In.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Page 996 Engine Side, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Crankshaft Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 999 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1000 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1001 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1002 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1003 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1004 Crankshaft Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1005 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1006 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1007 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1008 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1009 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1010 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1011 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1012 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1013 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1014 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1015 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1016 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1017 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1018 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1019 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1020 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1021 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1022 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1023 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1024 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1025 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1026 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1027 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1028 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1029 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1030 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Page 1031 Crankshaft Position Sensor: Description and Operation DESCRIPTION The Crankshaft Position (CKP) Sensor is located in the front engine cover and is perpendicular to the crankshaft target wheel. The air gap between the sensor and the wheel is preset and not adjustable. The target wheel has three slots 60° apart and is keyed to the crankshaft. As the target wheel rotates, the slots passing by the sensor create a change in the magnetic field of the sensor which results in an induced voltage pulse. One revolution of the crankshaft results in three pulses (3x signal). Based on these pulses, the VCM is able to determine crankshaft position and engine speed. The VCM then activates the fuel injector and provides a spark to the Distributor. The relation between the crankshaft position sensor and the target wheel is crucial. The sensor must be exactly perpendicular to the target wheel with the correct air gap. OPERATION The crankshaft position sensor provides the VCM with crankshaft speed and crankshaft position. The VCM utilizes this information to determine if an engine Misfire is present. The VCM monitors the Crankshaft Position Sensor (CKP) sensor for momentarily drop in crankshaft speed to determine if a misfire is occurring. When the VCM detects a misfire, a Diagnostic Trouble Code (DTC) P0300 will set. The VCM also monitors the CKP sensor signal circuit for malfunctions. The VCM monitors CKP signal and the High and Low resolution signals. The VCM calculates these signals to determine a ratio. When the VCM detects that the ratio is out of normal operating range, the VCM will set a Diagnostic Trouble Code (DTC) P0337 or a DTC P0338. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Page 1032 Crankshaft Position Sensor: Service and Repair REMOVAL PROCEDURE 1. Remove the electrical connector. 2. Remove the sensor hold down bolt. 3. Remove the sensor from the timing cover. NOTE: When installing or removing a crankshaft position (CKP) sensor make sure the sensor is fully seated and held stationary in the front cover before torquing the hold down bolt into the front cover. A sensor which is not seated may result in erratic operation and lead to the setting of false codes. 4. Inspect the sensor O-ring for wear, cracks or leakage. Replace if necessary. Lube the new O-ring with clean engine oil before installing. INSTALLATION PROCEDURE NOTE: Make certain that the Crankshaft Position (CKP) sensor mounting surfaces are clean and free of burrs before installing the CKP sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Page 1033 1. Install the sensor into the timing cover. 2. Install the sensor hold down bolt. Tighten ^ Tighten the hold down bolt to 8 Nm (71 lb. in.). 3. Install the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Specifications Intake Air Temperature (IAT) Sensor: Specifications Torque Valve Torque Valve Induction Air Sensor 44 in.lb Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions Intake Air Temperature (IAT) Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1039 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1040 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1041 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1042 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1043 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1044 Intake Air Temperature (IAT) Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1045 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1046 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1047 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1048 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1049 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1050 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1051 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1052 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1053 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1054 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1055 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1056 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1057 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1058 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1059 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1060 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1061 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1062 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1063 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1064 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1065 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1066 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1067 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1068 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1069 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1070 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1071 IAT Sensor Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Page 1072 Intake Air Temperature (IAT) Sensor: Description and Operation Intake Air Temperature (IAT) Sensor PURPOSE The Intake Air Temperature (IAT) sensor is a thermistor which changes value based on the temperature of air entering the engine. OPERATION Low temperature produces a high resistance 100,000 ohms at -40° (-40°F). A high temperature causes low resistance 70 ohms at 130°C (266°F). The VCM supplies a 5.0 volt signal to the sensor through a resistor in the VCM and measures the voltage. The voltage will be high when the incoming air is cold, and low when the air is hot. By measuring the voltage, the VCM calculates the incoming air temperature. The IAT sensor signal is used to adjust spark timing according to incoming air density. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Page 1073 Intake Air Temperature (IAT) Sensor: Testing and Inspection The scan tool displays temperature of the air entering the engine, which should read close to ambient air temperature when engine is cold, and rise as underhood temperature increases. If the engine has not been run for several hours (overnight) the Intake Air Temperature (IAT) sensor temperature and engine coolant temperature should read close to each other. If the VCM detects a malfunction in the AT sensor circuit, the following DTCs will set: ^ DTC P0112 circuit low. ^ DTC P0113 circuit high. ^ DTC P0111 circuit intermittent high. ^ DTC P0112 circuit intermittent low. Refer to Diagnostic Tables. See: Powertrain Management/Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Page 1074 Intake Air Temperature (IAT) Sensor: Service and Repair IAT Sensor And Electrical Connector REMOVAL PROCEDURE 1. Disconnect the electrical connector releasing locking tab. 2. Remove the Intake Air Temperature (IAT) sensor by grasping sensor, twist and pull out from air cleaner INSTALLATION PROCEDURE 1. Install the IAT sensor. 2. Connect the electrical connector Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Specifications Knock Sensor: Specifications Knock sensor ....................................................................................................................................... ....................................................... 19 Nm (14 lb. ft.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Specifications > Page 1078 Knock Sensor: Locations Engine View, Rear LH side of Engine Block, below Exhaust Manifold, forward of Starter Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions Knock Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1081 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1082 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1083 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1084 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1085 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1086 Knock Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1087 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1088 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1089 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1090 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1091 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1092 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1093 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1094 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1095 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1096 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1097 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1098 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1099 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1100 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1101 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1102 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1103 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1104 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1105 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1106 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1107 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1108 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1109 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1110 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1111 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1112 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1113 Knock Sensor Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Page 1114 Knock Sensor: Description and Operation Description The Knock Sensor (KS) system is used to detect engine detonation The VCM will retard the spark timing based on the signals from the KS module. The Knock Sensor(s) produce an AC voltage that is sent to the KS module. The amount of AC voltage produced is proportional to the amount of knock. Operation An operating engine produces a normal amount of engine mechanical vibration (Noise). The knock sensor(s) will produce an AC voltage signal from this Noise. When an engine is operating, the VCM will learn the minimum and maximum frequency of the noise the engine produces. When the VCM determines that this frequency is less than or greater than the expected amount, a knock sensor DTC will set. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Page 1115 Knock Sensor: Service and Repair Diagram Removal Procedure NOTE: The knock sensor is located in areas of the cylinder head. On most applications, the knock sensors are installed in a hole which is exposed to engine coolant. Care should be exercised when servicing these sensors. 1. Disconnect the negative battery cable. Important: On knock sensors which are mounted in the end of the cylinder head draining the cooling system will not be necessary. 2. Drain the cooling system. Refer to Draining and Filling Cooling System. 3. Remove the wiring harness connector from knock sensor. 4. Remove the knock sensor from cylinder head. Installation Procedure Important: Do not use silicon tape as this will insulate the sensor from the engine block. 2. After applying a water base caulk to the sensor threads, install the knock sensor into the cylinder head. Tighten ^ Tighten to 19 Nm (14 lb. ft.). 2. Connect the negative battery cable. 3. Refill cooling system if required. Refer to Draining and Filling Cooling System. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Locations Engine Side, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions Manifold Absolute Pressure (MAP) Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1121 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1122 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1123 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1124 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1125 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1126 Manifold Absolute Pressure (MAP) Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1127 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1128 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1129 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1130 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1131 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1132 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1133 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1134 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1135 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1136 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1137 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1138 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1139 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1140 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1141 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1142 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1143 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1144 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1145 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1146 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1147 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1148 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1149 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1150 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1151 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1152 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1153 MAP System Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Page 1154 Manifold Absolute Pressure (MAP) Sensor: Description and Operation Manifold Absolute Pressure (MAP) Sensor PURPOSE The Manifold Absolute Pressure (MAP) sensor responds to changes in the intake manifold pressure. The pressure changes as a result of engine load and speed. The map sensor converts this to a voltage output. OPERATION A closed throttle on engine coast down would produce a relatively low MAP output voltage. A wide open throttle would produce a high MAP output voltage. This high output voltage is produced because the pressure inside the manifold is the same as outside the manifold. The MAP is inversely proportional to what is measured on a vacuum gage. The MAP sensor is used for the following: ^ Altitude determination. ^ Ignition timing control. ^ Exhaust Gas Recirculation (EGR) diagnostic. ^ Speed density fuel management default. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Page 1155 Manifold Absolute Pressure (MAP) Sensor: Testing and Inspection When the VCM detects a malfunction in the MAP sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0106 circuit performance. ^ DTC P0107 circuit low. ^ DTC P0108 circuit high. ^ DTC P1106 intermittent circuit high. ^ DTC P1107 intermittent circuit low. Refer to System Diagnosis / Diagnostic Charts for testing information. See: Powertrain Management/Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Page 1156 Manifold Absolute Pressure (MAP) Sensor: Service and Repair MAP Sensor NOTE: Other than checking for loose hoses and electrical connections, the only service possible is unit replacement, if the diagnosis shows the sensor to be faulty. REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Disconnect the vacuum harness assembly. 3. Disconnect the electrical connector releasing locking tab. 4. Remove the bolts or release lock tabs and remove the sensor. INSTALLATION PROCEDURE 1. Install the bolts or snap sensor on bracket. 2. Connect the electrical connector. 3. Connect the vacuum harness. 4. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Oxygen Sensor - Locations in Various Exhaust Systems Oxygen Sensor: Technical Service Bulletins Oxygen Sensor - Locations in Various Exhaust Systems File In Section: 6E - Engine Fuel & Emission Bulletin No.: 67-65-40 Date: March, 1997 INFORMATION Subject: Pictorial of Oxygen Sensor Designations in Various Exhaust Systems Configurations Models: 1996-97 Passenger Cars, Geos and Trucks Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Oxygen Sensor - Locations in Various Exhaust Systems > Page 1161 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Oxygen Sensor - Locations in Various Exhaust Systems > Page 1162 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Oxygen Sensor - Locations in Various Exhaust Systems > Page 1163 Pictorials of the designation of oxygen sensors in General Motors vehicles. There has been some confusion relative to OBD II oxygen sensor designation. The intent of this bulletin is to eliminate misdiagnosis of those oxygen sensors due to misidentification. When using Section 6E of the Service Manual, this chart can help locate the appropriate bank and sensor for the diagnostic. For "V" engines; BANK 1 is always on the side of the engine with the number 1 cylinder (odd cylinders), and BANK 2 is always on the side of the engine where the number 2 cylinder (even cylinders) is located. Just a reminder, the OBD II P-codes, technician observations and customer comments are all to be recorded on the repair order in accordance with article 1.6.2G of the GM Service Policies and Procedures Manual. Use the approved labor operation for the sensors replaced. J 6372 is used for engine out sensors. Labor Operation J 6380 is for the pre-sensor (the sensor just in front of the catalytic converter) and the post sensor (the sensor behind the catalytic converter). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Page 1164 Oxygen Sensor: Specifications Heated Oxygen Sensor (HO2S) .......................................................................................................... ...................................................... 41 Nm (30 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations Oxygen Sensor: Component Locations Light Duty Vehicles Bulletin No.: 67-65-40 PICTORIALS OF THE DESIGNATION OF OXYGEN SENSORS There has been some confusion relative to OBD II oxygen sensor designation. The intent of this article is to eliminate misdiagnosis of those oxygen sensors due to mis-identification. This chart can help locate the appropriate bank and sensor for the diagnostic. NOTE: For "V" engines; BANK 1 is always on the side of the engine with the number 1 cylinder (odd cylinders), and BANK 2 is always on the side of the engine where the number 2 cylinder (even cylinders) is located. Heavy Duty Vehicles Bulletin No.: 67-65-40 PICTORIALS OF THE DESIGNATION OF OXYGEN SENSORS Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 1167 There has been some confusion relative to OBD II oxygen sensor designation. The intent of this article is to eliminate misdiagnosis of those oxygen sensors due to mis-identification. This chart can help locate the appropriate bank and sensor for the diagnostic. NOTE: For "V" engines; BANK 1 is always on the side of the engine with the number 1 cylinder (odd cylinders), and BANK 2 is always on the side of the engine where the number 2 cylinder (even cylinders) is located. 5-Speed Manual Transmission (MW3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 1168 Oxygen Sensor: Connector Locations Engine View, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 1169 Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 1170 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 1171 5-Speed Manual Transmission W/4WD 5-Speed Manual Transmission (MW3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 1172 5-Speed Manual Transmission (MW3) 5-Speed Manual Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 1173 Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions Oxygen Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1176 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1177 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1178 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1179 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1180 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1181 Oxygen Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1182 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1183 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1184 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1185 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1186 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1187 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1188 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1189 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1190 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1191 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1192 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1193 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1194 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1195 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1196 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1197 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1198 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1199 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1200 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1201 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1202 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1203 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1204 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1205 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1206 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1207 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1208 Oxygen Sensor: Connector Views C107: Engine HARN To Oxygen Sensor HARN Oxygen Sensor RH, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1209 HO2S Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Page 1210 Oxygen Sensor: Description and Operation Heated Oxygen Sensor (HO2S) Cutaway OPERATION To control emissions of Hydrocarbons (HO), Carbon Monoxide (CO), and Oxides of Nitrogen (NOx), a three-way catalytic converter is used. The catalyst within the converter promotes a chemical reaction which oxidizes the HO and CO present in the exhaust gas, converting them into harmless water vapor and carbon dioxide. The catalyst also reduces NOx, converting it to nitrogen. The VCM has the ability to monitor this process using the Bank 1 Sensor 2 and the Bank 2 Sensor 2 heated oxygen sensors. The Bank 1 Sensor 2 sensor produces an output signal which indicates the amount of oxygen present in the exhaust gas entering the three way catalytic converter. The Bank 2 Sensor 2 sensor produces an output signal which indicates the oxygen storage capacity of the catalyst; this in turn indicates the catalyst ability to convert exhaust gases efficiently. If the catalyst is operating efficiently, the Bank 1 Sensor 2 sensor will produce a far more active signal than that produced by the Bank 2 Sensor 2 sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Page 1211 The catalyst monitor sensors operate the same as the fuel control sensors. Although the Bank 1 Sensor 2 and Bank 2 Sensor 2 sensors main function is catalyst monitoring, they also play a limited role in fuel control. If a sensor output indicates a voltage either above or below the 450 millivolt bias voltage for an extended period of time, the VCM will make a slight adjustment to fuel trim to ensure that fuel delivery is correct for catalyst monitoring. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Testing and Inspection > Heated Oxygen Sensor (HO2S 1) Testing Oxygen Sensor: Testing and Inspection Heated Oxygen Sensor (HO2S 1) Testing The heated oxygen sensor circuit, if open, should set a Diagnostic Trouble Code (DTC) P0134 and the Scan tool will display a constant voltage between 350-550 mV. A constant voltage below 250 mV in the sensor circuit should set DTC P0131, while a constant voltage above 750 mV in the circuit should set DTC P0132. DTC P0131 and DTC P0132 could also be set as a result of fuel system problems. Refer to DTC P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1 or DTC P0132 HO2S Circuit High Voltage Bank 1 Sensor 1 or DTC P0134 HO2S Insufficient Activity Bank 1 Sensor 1. Refer to System Diagnosis / Diagnostic Charts for testing information. See: Powertrain Management/Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Testing and Inspection > Heated Oxygen Sensor (HO2S 1) Testing > Page 1214 Oxygen Sensor: Testing and Inspection Heated Oxygen Sensor (HO2S 2) Testing A problem with the HO2S 2 electrical circuits should set Diagnostic Trouble Code (DTC) P0137, P0138 or P0140, depending on the specific condition. If the catalyst is functioning correctly, the HO2S 2 signal will be far less active than that produced by HO2S 1. If a problem exists which causes the VCM to detect excessive HO2S 2 activity outside of an acceptable range for an extended period of time, the VCM will set DTC P0420, indicating that the three-way catalytic converter [prime ]s oxygen storage capacity is below a threshold considered acceptable. Refer to DTC P0137 HO2S Circuit Low Voltage Bank 1 Sensor 2 or DTC P0138 HO2S Circuit High Voltage Bank 1 Sensor 2 or DTC P0140 HO2S Insufficient Activity Bank 1 Sensor 2 or DTC P0420 TWC System Low Efficiency Bank 1. Refer to System Diagnosis / Diagnostic Charts for testing information. See: Powertrain Management/Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Testing and Inspection > Page 1215 Oxygen Sensor: Service and Repair Heated Oxygen Sensor (HO2S) Electrical Connector Heated Oxygen Sensor (HO2S) REMOVAL PROCEDURE CAUTION: The Heated Oxygen Sensor (HO2S) and the Oxygen Sensor use a permanently attached pigtail and connector. Do not remove this pigtail from the Heated Oxygen Sensor. Damage or the removal of the pigtail or the connector could affect the proper operation of the sensor. CAUTION: Take care when handling the HO2S. Keep the in-line electrical connector and the louvered end free of grease, dirt, or other contaminants. Also avoid using cleaning solvents of any type. Do not drop or roughly handle the HO2S. CAUTION: If the heated oxygen sensor pigtail wiring, connector or terminal is damaged, the entire oxygen sensor assembly must be replaced. Do Not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. CAUTION: This clean air reference is obtained by way of the oxygen sensor signal and heater wires. Any attempt to repair the wires, connectors, or terminals could result in the obstruction of the air reference and degraded sensor performance. The following guidelines should be used when servicing the heated oxygen sensor: ^ Do Not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. ^ The sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems, ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do Not remove or defeat the oxygen sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will cause poor engine performance. ^ To prevent damage due to water intrusion. be sure that the peripheral seal remains intact on the vehicle harness connector. The engine harness Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Testing and Inspection > Page 1216 may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. CAUTION: The Heated Oxygen Sensor (HO2S) may be difficult to remove when the engine temperature is below 48°C (120°F). Excessive force may damage the threads in the exhaust manifold or the exhaust pipe. 1. Disconnect the negative battery cable. 2. Remove the electrical connector by releasing the locking tab. 3. Carefully back out the heated oxygen sensor. INSTALLATION PROCEDURE NOTE: A special anti-seize compound is used on the Heated Oxygen Sensor (HO2S) threads. The compound consists of liquid graphite and glass beads. The graphite tends to burn away, but the glass beads remain, making the sensor easier to remove. New, or service replacement sensors already have the compound applied to the threads. If the sensor is removed from an engine and if for any reason it is to be reinstalled, the threads must have anti-seize compound applied before the reinstallation. 1. Coat the threads of the oxygen sensor with anti-seize compound GM P/N 5613695 or the equivalent if necessary. 2. Install the sensor. Tighten ^ Tighten the sensor to 41 Nm (30 lb. ft.). 3. Install the electrical connector. 4. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Specifications Throttle Position Sensor: Specifications Screw assemblies ................................................................................................................................ .................................................. 2.0 Nm (18.0 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Specifications > Page 1220 Engine Side, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Throttle Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1223 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1224 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1225 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1226 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1227 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1228 Throttle Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1229 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1230 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1231 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1232 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1233 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1234 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1235 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1236 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1237 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1238 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1239 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1240 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1241 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1242 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1243 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1244 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1245 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1246 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1247 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1248 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1249 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1250 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1251 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1252 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1253 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1254 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1255 TP Sensor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Page 1256 Throttle Position Sensor: Description and Operation Diagram The non-adjustable Throttle Position (TP) sensor is mounted on the throttle body assembly opposite the throttle lever. The TP sensor senses the throttle valve angle and relays that information to the VCM. Knowledge of throttle angle is one of the inputs needed by the VCM to generate the required injector control signals (pulses). For further information on replacement, refer to TP Sensor. See: Service and Repair Legend (1) Throttle Body Assembly. (2) IAC Valve Assembly 0-ring. (3) IAC Valve Assembly Attaching Screw. (4) Idle Air Control (IAC) Valve Assembly. (5) TP Sensor 0-ring (6) Throttle Position (TP) Sensor. (7) TP Sensor Attaching Screw. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Testing and Inspection > Throttle Position (TP) Sensor Throttle Position Sensor: Testing and Inspection Throttle Position (TP) Sensor When the VCM detects a malfunction with the Throttle Position (TP) sensor circuits, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0121 circuit performance ^ DTC P0122 circuit low. ^ DTC P0123 circuit high. ^ DTC P1121 intermittent circuit high. ^ DTC P1122 intermittent circuit low. Refer to Diagnostic Tables. See: Powertrain Management/Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Testing and Inspection > Throttle Position (TP) Sensor > Page 1259 Throttle Position Sensor: Testing and Inspection Throttle Position Sensor Output This check should be performed when Throttle Position (TP) sensor attaching parts have been replaced. A scan tool can be used to read the TP signal output voltage. 1. Connect digital voltmeter J 39200 from TP sensor connector terminal B (BLk wire) to terminal C (DK Blue wire). Jumpers for terminal access can be made using terminals 1214836 and 12014837. 2. With ignition ON, engine stopped, the TP signal voltage should be less than 1.25V if more than 1.25V verify free throttle movement. If still more than 1.25V, replace TP sensor. 3. Remove the voltmeter and jumpers, reconnect the TP sensor connector to the sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Testing and Inspection > Page 1260 Throttle Position Sensor: Service and Repair Throttle Position Sensor Electrical Connector REMOVAL PROCEDURE CAUTION: The Throttle Position (TP) sensor is an electrical component. Do not soak the TP sensor in any liquid cleaner or solvent, as damage may result. 1. Remove the air cleaner and adapter. 2. Disconnect the electrical connector releasing locking tab. 3. Remove the two TP sensor attaching screw assemblies. 4. Remove the TP sensor from throttle body assembly. 5. Remove the TP sensor seal. INSTALLATION PROCEDURE 1. Install the TP sensor seal over throttle shaft. 2. With throttle valve closed, install the TP sensor on the throttle shaft. Rotate counterclockwise to align mounting holes. 3. Install the two TP sensor attaching screw assemblies. Tighten ^ Tighten the screw assemblies to 2.0 Nm (18.0 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Testing and Inspection > Page 1261 4. Connect the electrical connector. 5. Install the air cleaner and adapter. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Technical Service Bulletins > A/T - Park/Neutral Switch Connector Cannot Be Removed Transmission Position Switch/Sensor: Technical Service Bulletins A/T - Park/Neutral Switch Connector Cannot Be Removed File In Section: 7 - Transmission Bulletin No.: 83-71-10 Date: May, 1998 Subject: Park (Neutral Position Switch Connector Cannot be Removed (Replace Switch and Connectors) Models: 1997-98 Chevrolet Corvette 1995-98 Chevrolet and GMC S/T Models 1996-98 Chevrolet and GMC M/L, P Models 1996-99 Chevrolet and GMC C/K, G Models 1996-98 Oldsmobile Bravada Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer conditions, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to insure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to insure water-tight connections. Parts Information P/N Description 12450016 Switch 15305925 4-Way Connector Assembly 15305887 7-Way Connector Assembly Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 1268 Transmission Position Switch/Sensor: Locations Park/Neutral Position Switch Electronic 4-Speed Automatic Overdrive Transmission Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 1269 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions Transmission Position Switch/Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1272 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1273 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1274 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1275 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1276 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1277 Transmission Position Switch/Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1278 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1279 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1280 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1281 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1282 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1283 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1284 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1285 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1286 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1287 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1288 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1289 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1290 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1291 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1292 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1293 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1294 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1295 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1296 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1297 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1298 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1299 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1300 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1301 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1302 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1303 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1304 Transmission Position Switch/Sensor: Connector Views C1: Transmission Range Switch C2: Transmission Range Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1305 Transmission Position Switch/Sensor: Electrical Diagrams Electronic PRNDL Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1306 Starter And Charging (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 1307 Transmission Position Switch/Sensor: Testing and Inspection Pressure Switch Assembly Resistance Check (1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 1308 Pressure Switch Assembly Resistance Check (2 Of 2) Tools Required - J 39775 4L60E Jumper Harness - J 39200 Digital Multimeter - J 35616 Connector Test Adapter Kit Important: Whenever the transmission 20-way connector is disconnected and the engine is running, multiple DTCs will set. Be sure to clear these codes when you are finished with this procedure Important: This procedure tests the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) circuits and the Automatic Transmission Fluid Temperature (TFT) Sensor circuit. Do not use this procedure to test other Automatic Transmission circuits, refer to 4L60-E Automatic Transmission Internal Wiring Harness check. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 1309 Transmission Position Switch/Sensor: Adjustments PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 1310 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 1311 Transmission Position Switch/Sensor: Service and Repair PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 1312 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations Vehicle Speed Sensor: Component Locations 5-Speed Manual Transmission 5-Speed Manual Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 1317 5-Speed Manual Transmission (MW3) 5-Speed Manual Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 1318 5-Speed Manual Transmission Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 1319 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 1320 Electronic 4-Speed Automatic Overdrive Transmission Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 1321 Vehicle Speed Sensor: Connector Locations 5-Speed Manual Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 1322 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions Vehicle Speed Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1325 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1326 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1327 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1328 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1329 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1330 Vehicle Speed Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1331 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1332 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1333 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1334 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1335 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1336 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1337 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1338 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1339 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1340 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1341 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1342 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1343 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1344 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1345 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1346 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1347 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1348 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1349 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1350 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1351 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1352 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1353 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1354 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1355 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1356 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Page 1357 Vehicle Speed Sensor: Description and Operation Vehicle Speed Sensor (2WD) DESCRIPTION The Vehicle Speed Sensor (VSS) is a pulse counter type input that informs the VCM how fast the vehicle is being driven. The VSS system uses an inductive sensor mounted in the tail housing of the transmission and a toothed reluctor wheel on the tail shaft. OPERATION As the reluctor rotates, the teeth alternately interfere with the magnetic field of the sensor creating an induced voltage pulse. The VSS produces an AC voltage signal that increases with vehicle speed. The VCM processes this signal and sends it to the following components: ^ Instrument Panel. ^ Cruise Control Module. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions Mass Air Flow (MAF) Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1363 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1364 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1365 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1366 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1367 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1368 Mass Air Flow (MAF) Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1369 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1370 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1371 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1372 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1373 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1374 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1375 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1376 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1377 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1378 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1379 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1380 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1381 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1382 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1383 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1384 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1385 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1386 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1387 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1388 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1389 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1390 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1391 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1392 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1393 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1394 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 1395 Mass Air Flow System Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Page 1396 Mass Air Flow (MAF) Sensor: Description and Operation Mass Air Flow (MAF) Sensor The Mass Air Flow (MAF) sensor measures the amount of air which passes through it. The VCM uses this information to determine the operating condition of the engine, to control fuel delivery. A large quantity of air indicates acceleration. A small quantity of air indicates deceleration or idle. The scan tool reads the MAF value and displays it in grams per second (gm/Sec). At idle, it should read between 5-7 gm/Sec on a fully warmed up engine. Values should change rather quickly on acceleration, but values should remain fairly stable at any given RPM. When the VCM detects a malfunction in the MAF sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0101 system performance. ^ DTC P0102 frequency low. ^ DTC P0103 frequency high. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Page 1397 Mass Air Flow (MAF) Sensor: Service and Repair MAF Sensor MAF Sensor Intake Duct REMOVAL PROCEDURE CAUTION: Take care when handling the Mass Air Flow (MAF). Do Not dent, puncture, or otherwise damage the honeywell located at the air inlet end of the MAF. Do Not touch the sensing elements or allow anything (including solvents and lubricants) to come in contact with them. A small amount of GM lubricant (P/N 99855406) may be used on the air duct only to aid in installation. Do Not drop or roughly handle the MAF. 1. Disconnect the 3 wire electrical connector. 2. Loosen the clamp on the intake duct. 3. Carefully remove the MAF sensor. INSTALLATION PROCEDURE 1. Install the MAF sensor. 2. Install the intake ducts. 3. Tighten the clamp. 4. Connect the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Fuel Pump Oil Pressure Switch and Sender Engine View, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Fuel Pump Oil Pressure Switch and Sender > Page 1402 Oil Pressure Switch (For Fuel Pump): Locations Oil Pressure Switch and Sender LH side of Engine, rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Page 1403 Fuel Pump Oil Pressure Switch And Sender Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Page 1404 Oil Pressure Switch (For Fuel Pump): Service and Repair Oil Pressure Switch Electrical Connector Oil Pressure Switch REMOVAL PROCEDURE 1. Remove the electrical connector. 2. Remove the fuel pump and oil pressure indicator switch, using wrench J 35748 it required. INSTALLATION PROCEDURE 1. Install the fuel pump and oil pressure indicator switch. 2. Install the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Specifications Throttle Position Sensor: Specifications Screw assemblies ................................................................................................................................ .................................................. 2.0 Nm (18.0 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Specifications > Page 1408 Engine Side, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Throttle Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1411 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1412 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1413 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1414 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1415 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1416 Throttle Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1417 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1418 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1419 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1420 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1421 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1422 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1423 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1424 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1425 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1426 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1427 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1428 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1429 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1430 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1431 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1432 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1433 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1434 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1435 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1436 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1437 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1438 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1439 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1440 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1441 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1442 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1443 TP Sensor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Page 1444 Throttle Position Sensor: Description and Operation Diagram The non-adjustable Throttle Position (TP) sensor is mounted on the throttle body assembly opposite the throttle lever. The TP sensor senses the throttle valve angle and relays that information to the VCM. Knowledge of throttle angle is one of the inputs needed by the VCM to generate the required injector control signals (pulses). For further information on replacement, refer to TP Sensor. See: Service and Repair Legend (1) Throttle Body Assembly. (2) IAC Valve Assembly 0-ring. (3) IAC Valve Assembly Attaching Screw. (4) Idle Air Control (IAC) Valve Assembly. (5) TP Sensor 0-ring (6) Throttle Position (TP) Sensor. (7) TP Sensor Attaching Screw. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Testing and Inspection > Throttle Position (TP) Sensor Throttle Position Sensor: Testing and Inspection Throttle Position (TP) Sensor When the VCM detects a malfunction with the Throttle Position (TP) sensor circuits, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0121 circuit performance ^ DTC P0122 circuit low. ^ DTC P0123 circuit high. ^ DTC P1121 intermittent circuit high. ^ DTC P1122 intermittent circuit low. Refer to Diagnostic Tables. See: Powertrain Management/Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Testing and Inspection > Throttle Position (TP) Sensor > Page 1447 Throttle Position Sensor: Testing and Inspection Throttle Position Sensor Output This check should be performed when Throttle Position (TP) sensor attaching parts have been replaced. A scan tool can be used to read the TP signal output voltage. 1. Connect digital voltmeter J 39200 from TP sensor connector terminal B (BLk wire) to terminal C (DK Blue wire). Jumpers for terminal access can be made using terminals 1214836 and 12014837. 2. With ignition ON, engine stopped, the TP signal voltage should be less than 1.25V if more than 1.25V verify free throttle movement. If still more than 1.25V, replace TP sensor. 3. Remove the voltmeter and jumpers, reconnect the TP sensor connector to the sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Testing and Inspection > Page 1448 Throttle Position Sensor: Service and Repair Throttle Position Sensor Electrical Connector REMOVAL PROCEDURE CAUTION: The Throttle Position (TP) sensor is an electrical component. Do not soak the TP sensor in any liquid cleaner or solvent, as damage may result. 1. Remove the air cleaner and adapter. 2. Disconnect the electrical connector releasing locking tab. 3. Remove the two TP sensor attaching screw assemblies. 4. Remove the TP sensor from throttle body assembly. 5. Remove the TP sensor seal. INSTALLATION PROCEDURE 1. Install the TP sensor seal over throttle shaft. 2. With throttle valve closed, install the TP sensor on the throttle shaft. Rotate counterclockwise to align mounting holes. 3. Install the two TP sensor attaching screw assemblies. Tighten ^ Tighten the screw assemblies to 2.0 Nm (18.0 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Testing and Inspection > Page 1449 4. Connect the electrical connector. 5. Install the air cleaner and adapter. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Camshaft Position Sensor: Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1455 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1456 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1457 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1458 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1459 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1460 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1461 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Page 1462 Camshaft Position Sensor: Specifications Camshaft position sensor retaining screw ........................................................................................................................................... 4-6 Nm (35-53 lb. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Page 1463 Engine View, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Camshaft Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1466 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1467 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1468 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1469 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1470 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1471 Camshaft Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1472 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1473 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1474 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1475 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1476 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1477 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1478 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1479 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1480 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1481 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1482 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1483 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1484 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1485 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1486 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1487 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1488 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1489 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1490 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1491 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1492 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1493 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1494 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1495 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1496 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1497 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Page 1498 Camshaft Position Sensor: Description and Operation Camshaft Position Sensor The Camshaft Position (CMP) sensor is located within the distributor. It's operation is very similar to the Crankshaft Position (CKP) sensor however it will provide one pulse per camshaft revolution (1x signal). This signal is not detrimental to the driveability of the vehicle. The Vehicle Control Module (VCM) utilizes this signal in conjunction with the crankshaft position to determine which cylinder(s) are misfiring. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Testing and Inspection > Cam Signal Camshaft Position Sensor: Testing and Inspection Cam Signal The VCM uses this signal to determine the position of the #1 piston during its power stroke. This signal is used by the VCM to calculate fuel injection mode of operation. A loss of this signal will set DTC P0340. If the cam signal is lost while the engine is running, the fuel injection system will shift to a calculated fuel injection mode based on the last fuel injection pulse, and the engine will continue to run. The engine can be restarted and will run in the calculated mode as long as the fault is present Refer to Diagnostic Trouble Code (DTC) P0340 Camshaft Position Sensor (CKP) Sensor Circuit. See: Powertrain Management/Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Testing and Inspection > Page 1501 Camshaft Position Sensor: Service and Repair REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Disconnect the electrical connector from the camshaft position sensor. 3. Remove the camshaft position sensor retaining screw. 4. Remove the camshaft position sensor. INSTALLATION PROCEDURE 1. Install the camshaft position sensor. 2. Install the camshaft position sensor retaining screw, torque to 4-6 Nm (35-53 lb. in.). 3. Connect the electrical connector. 4. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-014 > Apr > 00 > Engine - No/Hard/Slow Start/Backfire/Kickback Crankshaft Position Sensor: Customer Interest Engine - No/Hard/Slow Start/Backfire/Kickback File In Section: 06 - Engine/Propulsion System Bulletin No.: 00-06-04-014 Date: April, 2000 TECHNICAL Subject: No, Hard, or Slow Start, Backfire or "Kickback" During Crank/Start, "Grinding" or Unusual Noises During Crank, DTC P0338 (Replace Crankshaft Position Sensor) Models: 1999-2000 Cadillac Escalade 1995-2000 Chevrolet and GMC SIT Models 1996-2000 Chevrolet and GMC C/K, M/L, G, P Models 1996-2000 Oldsmobile Bravada with 4.3 L, 5.0 L, 5.7 L or 7.4 L Engine (VINs W, X, M, R, J RPOs L35, LF6, L30, L31, L29) Condition: Some customers may comment on one or more of the following conditions: ^ Backfire during crank/start ^ "Kickback" during crank/start ^ "No" start ^ "Slow" or "hard" start/crank ^ "Grinding" or unusual noises during crank/start ^ Cracked or broken engine block at the starter boss ^ Broken starter drive housing ^ Broken starter ring gear on flywheel ^ Any combination of the above Cause: A condition may exist that allows the crankshaft position sensor to command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss. Correction: Inspect for a stored powertrain DTC code P0338. This DTC will NOT illuminate the "Service Engine Soon" light. If this code is stored, the Crankshaft Position Sensor, P/N 10456607, MUST be replaced and the remaining components inspected for damage (engine block at the starter boss, the starter drive housing, and the engine flywheel starter ring gear). Notice: When DTC code P0338 is set, failure to replace the Crankshaft Position Sensor could result in repeated inoperative conditions of the starter or flywheel. Important: Some flywheel wear is normal; broken or missing teeth and/or cracks, are not normal. Parts Information Parts are currently available from GMSPO. Warranty Information: For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 00-06-04-014 > Apr > 00 > Engine - No/Hard/Slow Start/Backfire/Kickback Crankshaft Position Sensor: All Technical Service Bulletins Engine - No/Hard/Slow Start/Backfire/Kickback File In Section: 06 - Engine/Propulsion System Bulletin No.: 00-06-04-014 Date: April, 2000 TECHNICAL Subject: No, Hard, or Slow Start, Backfire or "Kickback" During Crank/Start, "Grinding" or Unusual Noises During Crank, DTC P0338 (Replace Crankshaft Position Sensor) Models: 1999-2000 Cadillac Escalade 1995-2000 Chevrolet and GMC SIT Models 1996-2000 Chevrolet and GMC C/K, M/L, G, P Models 1996-2000 Oldsmobile Bravada with 4.3 L, 5.0 L, 5.7 L or 7.4 L Engine (VINs W, X, M, R, J RPOs L35, LF6, L30, L31, L29) Condition: Some customers may comment on one or more of the following conditions: ^ Backfire during crank/start ^ "Kickback" during crank/start ^ "No" start ^ "Slow" or "hard" start/crank ^ "Grinding" or unusual noises during crank/start ^ Cracked or broken engine block at the starter boss ^ Broken starter drive housing ^ Broken starter ring gear on flywheel ^ Any combination of the above Cause: A condition may exist that allows the crankshaft position sensor to command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss. Correction: Inspect for a stored powertrain DTC code P0338. This DTC will NOT illuminate the "Service Engine Soon" light. If this code is stored, the Crankshaft Position Sensor, P/N 10456607, MUST be replaced and the remaining components inspected for damage (engine block at the starter boss, the starter drive housing, and the engine flywheel starter ring gear). Notice: When DTC code P0338 is set, failure to replace the Crankshaft Position Sensor could result in repeated inoperative conditions of the starter or flywheel. Important: Some flywheel wear is normal; broken or missing teeth and/or cracks, are not normal. Parts Information Parts are currently available from GMSPO. Warranty Information: For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Crankshaft Position Sensor: All Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1519 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1520 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1521 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1522 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1523 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1524 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1525 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Crankshaft Position Sensor: All Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1531 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1532 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1533 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1534 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1535 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1536 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 1537 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Page 1538 Crankshaft Position Sensor: Specifications Crankshaft Position Sensor mounting bolts ................................................................................................................................................. 8 Nm (71 lb. In.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Page 1539 Engine Side, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Crankshaft Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1542 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1543 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1544 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1545 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1546 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1547 Crankshaft Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1548 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1549 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1550 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1551 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1552 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1553 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1554 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1555 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1556 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1557 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1558 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1559 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1560 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1561 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1562 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1563 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1564 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1565 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1566 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1567 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1568 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1569 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1570 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1571 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1572 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1573 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Page 1574 Crankshaft Position Sensor: Description and Operation DESCRIPTION The Crankshaft Position (CKP) Sensor is located in the front engine cover and is perpendicular to the crankshaft target wheel. The air gap between the sensor and the wheel is preset and not adjustable. The target wheel has three slots 60° apart and is keyed to the crankshaft. As the target wheel rotates, the slots passing by the sensor create a change in the magnetic field of the sensor which results in an induced voltage pulse. One revolution of the crankshaft results in three pulses (3x signal). Based on these pulses, the VCM is able to determine crankshaft position and engine speed. The VCM then activates the fuel injector and provides a spark to the Distributor. The relation between the crankshaft position sensor and the target wheel is crucial. The sensor must be exactly perpendicular to the target wheel with the correct air gap. OPERATION The crankshaft position sensor provides the VCM with crankshaft speed and crankshaft position. The VCM utilizes this information to determine if an engine Misfire is present. The VCM monitors the Crankshaft Position Sensor (CKP) sensor for momentarily drop in crankshaft speed to determine if a misfire is occurring. When the VCM detects a misfire, a Diagnostic Trouble Code (DTC) P0300 will set. The VCM also monitors the CKP sensor signal circuit for malfunctions. The VCM monitors CKP signal and the High and Low resolution signals. The VCM calculates these signals to determine a ratio. When the VCM detects that the ratio is out of normal operating range, the VCM will set a Diagnostic Trouble Code (DTC) P0337 or a DTC P0338. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Page 1575 Crankshaft Position Sensor: Service and Repair REMOVAL PROCEDURE 1. Remove the electrical connector. 2. Remove the sensor hold down bolt. 3. Remove the sensor from the timing cover. NOTE: When installing or removing a crankshaft position (CKP) sensor make sure the sensor is fully seated and held stationary in the front cover before torquing the hold down bolt into the front cover. A sensor which is not seated may result in erratic operation and lead to the setting of false codes. 4. Inspect the sensor O-ring for wear, cracks or leakage. Replace if necessary. Lube the new O-ring with clean engine oil before installing. INSTALLATION PROCEDURE NOTE: Make certain that the Crankshaft Position (CKP) sensor mounting surfaces are clean and free of burrs before installing the CKP sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Page 1576 1. Install the sensor into the timing cover. 2. Install the sensor hold down bolt. Tighten ^ Tighten the hold down bolt to 8 Nm (71 lb. in.). 3. Install the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Hall Effect Sensor, Ignition > Component Information > Description and Operation Hall Effect Sensor: Description and Operation Description The hall effect switch connects to the VCM through the primary engine harness and provides cylinder identification information. The hall effect switch is located under the distributor cap. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder Technical Service Bulletin # 73-01-09 Date: 971001 Starting - Revised Procedures for Inop Ignition Cylinder File In Section: 0 - General Information Bulletin No.: 73-01-09 Date: October, 1997 INFORMATION Subject: New Tumblers for Cylinder Recoding, Revised Repair Procedures for Inoperative Ignition Cylinders (Seized/Won't Rotate), Labor Operation/Time Allowances Models: 1995-97 Buick Skylark, Riviera 1995-97 Chevrolet Cavalier 1997 Chevrolet Corvette, Malibu, Venture 1995-97 Oldsmobile Achieva 1997 Oldsmobile Aurora, Cutlass, Silhouette 1995-97 Pontiac Grand Am, Sunfire 1997 Pontiac Grand Prix, Trans Sport 1995-97 Chevrolet and GMC C/K, S/T Models 1996-97 Chevrolet and GMC G, M/L Vans 1996-97 Oldsmobile Bravada The information in this bulletin concerns new designed tumblers for recoding lock cylinders that use double sided reversible keys, revised procedures for servicing ignition lock cylinders that are seized or not able to rotate and revised labor time guide information and allowances. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1589 The existing labor operation (E7200) has been changed to include "Add" conditions for cylinders that will not rotate. New Tumblers New tumblers are available from GMSPO for recoding lock cylinders that use double-sided reversible keys. These new tumblers should be used immediately and information about the disposition of original tumblers will be provided by GMSPO. Figure 1 shows the new tumbler profile. The shaded area was part of the original tumbler profile, and is removed on the new tumblers. The new part numbers for the tumblers are as follows: Part No. 2852732 = Tumbler # 1 Part No. 2852733 = Tumbler # 2 Part No. 2852734 = Tumbler # 3 Part No. 2852735 = Tumbler # 4 Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. New Procedures For Seized/Won't Rotate Column Mounted Ign. CYL. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1590 A. On G, J and N Models: DO NOT REMOVE THE STEERING COLUMN as indicated in the Service Manual procedure. 1. Remove the tilt lever, upper and lower column covers. 2. Drill hole in module housing as indicated in the illustration using a short drill bit (1/8" followed by 9/32") and 90 degree drill motor or go degree drill attachment to break or access the retaining spring for the lock cylinder button, see Figure 2. 3. Using a pick or needle nose pliers, remove the retaining spring from the hole. 4. Using pliers, grasp and remove the retaining button for the cylinder. 5. Remove the cylinder from the housing. 6. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 7. Install the new cylinder and reinstall the steering column components. B. On U, W, and light duty trucks, follow the Service Manual procedure for keys missing, or cylinders won't rotate. Procedure: Instrument Panel Mounted Switches Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1591 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Other Service Bulletins for Ignition Switch Lock Cylinder: > 00-08-46-002A > Apr > 05 > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder Technical Service Bulletin # 73-01-09 Date: 971001 Starting - Revised Procedures for Inop Ignition Cylinder File In Section: 0 - General Information Bulletin No.: 73-01-09 Date: October, 1997 INFORMATION Subject: New Tumblers for Cylinder Recoding, Revised Repair Procedures for Inoperative Ignition Cylinders (Seized/Won't Rotate), Labor Operation/Time Allowances Models: 1995-97 Buick Skylark, Riviera 1995-97 Chevrolet Cavalier 1997 Chevrolet Corvette, Malibu, Venture 1995-97 Oldsmobile Achieva 1997 Oldsmobile Aurora, Cutlass, Silhouette 1995-97 Pontiac Grand Am, Sunfire 1997 Pontiac Grand Prix, Trans Sport 1995-97 Chevrolet and GMC C/K, S/T Models 1996-97 Chevrolet and GMC G, M/L Vans 1996-97 Oldsmobile Bravada The information in this bulletin concerns new designed tumblers for recoding lock cylinders that use double sided reversible keys, revised procedures for servicing ignition lock cylinders that are seized or not able to rotate and revised labor time guide information and allowances. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Other Service Bulletins for Ignition Switch Lock Cylinder: > 00-08-46-002A > Apr > 05 > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1601 The existing labor operation (E7200) has been changed to include "Add" conditions for cylinders that will not rotate. New Tumblers New tumblers are available from GMSPO for recoding lock cylinders that use double-sided reversible keys. These new tumblers should be used immediately and information about the disposition of original tumblers will be provided by GMSPO. Figure 1 shows the new tumbler profile. The shaded area was part of the original tumbler profile, and is removed on the new tumblers. The new part numbers for the tumblers are as follows: Part No. 2852732 = Tumbler # 1 Part No. 2852733 = Tumbler # 2 Part No. 2852734 = Tumbler # 3 Part No. 2852735 = Tumbler # 4 Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. New Procedures For Seized/Won't Rotate Column Mounted Ign. CYL. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Other Service Bulletins for Ignition Switch Lock Cylinder: > 00-08-46-002A > Apr > 05 > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1602 A. On G, J and N Models: DO NOT REMOVE THE STEERING COLUMN as indicated in the Service Manual procedure. 1. Remove the tilt lever, upper and lower column covers. 2. Drill hole in module housing as indicated in the illustration using a short drill bit (1/8" followed by 9/32") and 90 degree drill motor or go degree drill attachment to break or access the retaining spring for the lock cylinder button, see Figure 2. 3. Using a pick or needle nose pliers, remove the retaining spring from the hole. 4. Using pliers, grasp and remove the retaining button for the cylinder. 5. Remove the cylinder from the housing. 6. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 7. Install the new cylinder and reinstall the steering column components. B. On U, W, and light duty trucks, follow the Service Manual procedure for keys missing, or cylinders won't rotate. Procedure: Instrument Panel Mounted Switches Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Other Service Bulletins for Ignition Switch Lock Cylinder: > 00-08-46-002A > Apr > 05 > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1603 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Other Service Bulletins for Ignition Switch Lock Cylinder: > 00-08-46-003B > Feb > 05 > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder Technical Service Bulletin # 73-01-09 Date: 971001 Starting - Revised Procedures for Inop Ignition Cylinder File In Section: 0 - General Information Bulletin No.: 73-01-09 Date: October, 1997 INFORMATION Subject: New Tumblers for Cylinder Recoding, Revised Repair Procedures for Inoperative Ignition Cylinders (Seized/Won't Rotate), Labor Operation/Time Allowances Models: 1995-97 Buick Skylark, Riviera 1995-97 Chevrolet Cavalier 1997 Chevrolet Corvette, Malibu, Venture 1995-97 Oldsmobile Achieva 1997 Oldsmobile Aurora, Cutlass, Silhouette 1995-97 Pontiac Grand Am, Sunfire 1997 Pontiac Grand Prix, Trans Sport 1995-97 Chevrolet and GMC C/K, S/T Models 1996-97 Chevrolet and GMC G, M/L Vans 1996-97 Oldsmobile Bravada The information in this bulletin concerns new designed tumblers for recoding lock cylinders that use double sided reversible keys, revised procedures for servicing ignition lock cylinders that are seized or not able to rotate and revised labor time guide information and allowances. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Other Service Bulletins for Ignition Switch Lock Cylinder: > 00-08-46-003B > Feb > 05 > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1614 The existing labor operation (E7200) has been changed to include "Add" conditions for cylinders that will not rotate. New Tumblers New tumblers are available from GMSPO for recoding lock cylinders that use double-sided reversible keys. These new tumblers should be used immediately and information about the disposition of original tumblers will be provided by GMSPO. Figure 1 shows the new tumbler profile. The shaded area was part of the original tumbler profile, and is removed on the new tumblers. The new part numbers for the tumblers are as follows: Part No. 2852732 = Tumbler # 1 Part No. 2852733 = Tumbler # 2 Part No. 2852734 = Tumbler # 3 Part No. 2852735 = Tumbler # 4 Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. New Procedures For Seized/Won't Rotate Column Mounted Ign. CYL. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Other Service Bulletins for Ignition Switch Lock Cylinder: > 00-08-46-003B > Feb > 05 > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1615 A. On G, J and N Models: DO NOT REMOVE THE STEERING COLUMN as indicated in the Service Manual procedure. 1. Remove the tilt lever, upper and lower column covers. 2. Drill hole in module housing as indicated in the illustration using a short drill bit (1/8" followed by 9/32") and 90 degree drill motor or go degree drill attachment to break or access the retaining spring for the lock cylinder button, see Figure 2. 3. Using a pick or needle nose pliers, remove the retaining spring from the hole. 4. Using pliers, grasp and remove the retaining button for the cylinder. 5. Remove the cylinder from the housing. 6. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 7. Install the new cylinder and reinstall the steering column components. B. On U, W, and light duty trucks, follow the Service Manual procedure for keys missing, or cylinders won't rotate. Procedure: Instrument Panel Mounted Switches Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Other Service Bulletins for Ignition Switch Lock Cylinder: > 00-08-46-003B > Feb > 05 > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1616 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Other Service Bulletins for Ignition Switch Lock Cylinder: > 00-08-46-003B > Feb > 05 > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder Technical Service Bulletin # 73-01-09 Date: 971001 Starting - Revised Procedures for Inop Ignition Cylinder File In Section: 0 - General Information Bulletin No.: 73-01-09 Date: October, 1997 INFORMATION Subject: New Tumblers for Cylinder Recoding, Revised Repair Procedures for Inoperative Ignition Cylinders (Seized/Won't Rotate), Labor Operation/Time Allowances Models: 1995-97 Buick Skylark, Riviera 1995-97 Chevrolet Cavalier 1997 Chevrolet Corvette, Malibu, Venture 1995-97 Oldsmobile Achieva 1997 Oldsmobile Aurora, Cutlass, Silhouette 1995-97 Pontiac Grand Am, Sunfire 1997 Pontiac Grand Prix, Trans Sport 1995-97 Chevrolet and GMC C/K, S/T Models 1996-97 Chevrolet and GMC G, M/L Vans 1996-97 Oldsmobile Bravada The information in this bulletin concerns new designed tumblers for recoding lock cylinders that use double sided reversible keys, revised procedures for servicing ignition lock cylinders that are seized or not able to rotate and revised labor time guide information and allowances. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Other Service Bulletins for Ignition Switch Lock Cylinder: > 00-08-46-003B > Feb > 05 > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1622 The existing labor operation (E7200) has been changed to include "Add" conditions for cylinders that will not rotate. New Tumblers New tumblers are available from GMSPO for recoding lock cylinders that use double-sided reversible keys. These new tumblers should be used immediately and information about the disposition of original tumblers will be provided by GMSPO. Figure 1 shows the new tumbler profile. The shaded area was part of the original tumbler profile, and is removed on the new tumblers. The new part numbers for the tumblers are as follows: Part No. 2852732 = Tumbler # 1 Part No. 2852733 = Tumbler # 2 Part No. 2852734 = Tumbler # 3 Part No. 2852735 = Tumbler # 4 Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. New Procedures For Seized/Won't Rotate Column Mounted Ign. CYL. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Other Service Bulletins for Ignition Switch Lock Cylinder: > 00-08-46-003B > Feb > 05 > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1623 A. On G, J and N Models: DO NOT REMOVE THE STEERING COLUMN as indicated in the Service Manual procedure. 1. Remove the tilt lever, upper and lower column covers. 2. Drill hole in module housing as indicated in the illustration using a short drill bit (1/8" followed by 9/32") and 90 degree drill motor or go degree drill attachment to break or access the retaining spring for the lock cylinder button, see Figure 2. 3. Using a pick or needle nose pliers, remove the retaining spring from the hole. 4. Using pliers, grasp and remove the retaining button for the cylinder. 5. Remove the cylinder from the housing. 6. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 7. Install the new cylinder and reinstall the steering column components. B. On U, W, and light duty trucks, follow the Service Manual procedure for keys missing, or cylinders won't rotate. Procedure: Instrument Panel Mounted Switches Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Other Service Bulletins for Ignition Switch Lock Cylinder: > 00-08-46-003B > Feb > 05 > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1624 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Other Service Bulletins for Ignition Switch Lock Cylinder: > 00-08-46-003B > Feb > 05 > Component Information > Technical Service Bulletins > Page 1625 Ignition Switch Lock Cylinder: Service and Repair The procedure has been updated by TSB# 73-01-09 Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Other Service Bulletins for Ignition Switch Lock Cylinder: > Page 1626 Air Bag(s) Arming and Disarming: Service and Repair General Service Precautions CAUTION: When performing service on or around SIR components or SIR wiring, follow the procedures listed below to temporarily disable the SIR system. Failure to follow procedures could result in possible air bag deployment, personal injury or otherwise unneeded SIR system repairs. The DERM can maintain sufficient voltage to cause a deployment for up to 2 minutes after the ignition switch is turned "OFF," the battery is disconnected, or the fuse powering the DERM is removed. Many of the service procedures require removal of the "AIR BAG" fuse, and disconnection of the inflator module from the deployment loop to avoid an accidental deployment. If the inflator module is disconnected from the deployment loop as noted in the "Disabling the SIR System" procedure that follows, service can begin immediately without waiting for the 2 minute time period to expire. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > System Information > Service and Repair > Air Bag Disarming and Arming Air Bag(s) Arming and Disarming: Service and Repair Air Bag Disarming and Arming Disabling the SIR System Fig. 1 Air Bag Two-way Connector DRIVER SIDE Many service procedures require the air bag system to be disabled to prevent accidental deployment. The air bag system can maintain sufficient voltage to cause deployment for up to 2 minutes after the ignition switch is turned off, the battery ground cable is disconnected or the DERM fuse is removed. If the inflator module is disconnected from the deployment loop by the following procedure, service can begin immediately without waiting for the 2 minute time period to elapse. 1. Turn steering wheel so that vehicle wheels are pointed straight ahead. 2. Turn ignition switch to Lock position and remove key. 3. Remove air bag fuse from fuse block. 4. Remove steering column filler panel. 5. Remove Connector Position Assurance (CPA) and disconnect yellow two-way connector at base of steering column, Fig. 1. PASSENGER SIDE 1. Remove air bag fuse from fuse block. Enabling the SIR System Driver Side 1. Turn ignition switch to LOCK and remove key. 2. Connect yellow two-way connector and install connector position assurance (CPA). 3. Install steering column filler panel. 4. Insert air bag fuse into fuse block. 5. Turn ignition switch to RUN and verify that the air bag warning lamp flashes seven times then turns off. Passenger Side 1. Turn ignition switch to LOCK and remove key. 2. Insert air bag fuse into fuse block. 3. Turn ignition switch to RUN and verify that the air bag warning lamp flashes seven times then turns off. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > System Information > Service and Repair > Air Bag Disarming and Arming > Page 1630 Air Bag(s) Arming and Disarming: Service and Repair General Service Precautions CAUTION: When performing service on or around SIR components or SIR wiring, follow the procedures listed below to temporarily disable the SIR system. Failure to follow procedures could result in possible air bag deployment, personal injury or otherwise unneeded SIR system repairs. The DERM can maintain sufficient voltage to cause a deployment for up to 2 minutes after the ignition switch is turned "OFF," the battery is disconnected, or the fuse powering the DERM is removed. Many of the service procedures require removal of the "AIR BAG" fuse, and disconnection of the inflator module from the deployment loop to avoid an accidental deployment. If the inflator module is disconnected from the deployment loop as noted in the "Disabling the SIR System" procedure that follows, service can begin immediately without waiting for the 2 minute time period to expire. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Specifications Knock Sensor: Specifications Knock sensor ....................................................................................................................................... ....................................................... 19 Nm (14 lb. ft.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Specifications > Page 1634 Knock Sensor: Locations Engine View, Rear LH side of Engine Block, below Exhaust Manifold, forward of Starter Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions Knock Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1637 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1638 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1639 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1640 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1641 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1642 Knock Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1643 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1644 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1645 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1646 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1647 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1648 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1649 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1650 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1651 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1652 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1653 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1654 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1655 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1656 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1657 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1658 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1659 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1660 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1661 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1662 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1663 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1664 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1665 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1666 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1667 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1668 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 1669 Knock Sensor Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Page 1670 Knock Sensor: Description and Operation Description The Knock Sensor (KS) system is used to detect engine detonation The VCM will retard the spark timing based on the signals from the KS module. The Knock Sensor(s) produce an AC voltage that is sent to the KS module. The amount of AC voltage produced is proportional to the amount of knock. Operation An operating engine produces a normal amount of engine mechanical vibration (Noise). The knock sensor(s) will produce an AC voltage signal from this Noise. When an engine is operating, the VCM will learn the minimum and maximum frequency of the noise the engine produces. When the VCM determines that this frequency is less than or greater than the expected amount, a knock sensor DTC will set. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Page 1671 Knock Sensor: Service and Repair Diagram Removal Procedure NOTE: The knock sensor is located in areas of the cylinder head. On most applications, the knock sensors are installed in a hole which is exposed to engine coolant. Care should be exercised when servicing these sensors. 1. Disconnect the negative battery cable. Important: On knock sensors which are mounted in the end of the cylinder head draining the cooling system will not be necessary. 2. Drain the cooling system. Refer to Draining and Filling Cooling System. 3. Remove the wiring harness connector from knock sensor. 4. Remove the knock sensor from cylinder head. Installation Procedure Important: Do not use silicon tape as this will insulate the sensor from the engine block. 2. After applying a water base caulk to the sensor threads, install the knock sensor into the cylinder head. Tighten ^ Tighten to 19 Nm (14 lb. ft.). 2. Connect the negative battery cable. 3. Refill cooling system if required. Refer to Draining and Filling Cooling System. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Restraint Systems > Impact Sensor > Component Information > Locations > Arming Sensor Impact Sensor: Locations Arming Sensor Inside LH Frame Rail, below Driver's Door Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Restraint Systems > Impact Sensor > Component Information > Locations > Arming Sensor > Page 1677 Impact Sensor: Locations RH Front Discriminating Sensor RH Front outside of RH Frame Rail Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Restraint Systems > Impact Sensor > Component Information > Locations > Arming Sensor > Page 1678 Impact Sensor: Locations LH Front Discriminating Sensor Front outside of LH Frame Rail Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Restraint Systems > Impact Sensor > Component Information > Locations > Page 1679 I/P HARN To Arming Sensor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Restraint Systems > Impact Sensor > Component Information > Description and Operation > Arming Sensor Impact Sensor: Description and Operation Arming Sensor The arming sensor is a protective switch located in the power side of the deployment loop. It is calibrated to close at low level speed changes. This ensures that the inflator module is connected directly to the 36 Volt Loop Reserve (VLR) output of the DERM when either of the discriminating sensors close. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Restraint Systems > Impact Sensor > Component Information > Description and Operation > Arming Sensor > Page 1682 Impact Sensor: Description and Operation Discriminating Sensors There are two discriminating sensors in the air bag system. They are wired in parallel on the low (ground) side of the deployment loop. These sensors are calibrated to close with speed changes severe enough to warrant deployment. A diagnostic resistor is connected in parallel with the switch contacts within each of the discriminating sensors. These parallel resistors supply the ground path for the current passing through the deployment loop during normal operation. This current flow results in voltage drops across each component in the deployment loop. The DERM monitors these voltage drops to detect malfunctions. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Restraint Systems > Impact Sensor > Component Information > Service and Repair > Arming Sensor Impact Sensor: Service and Repair Arming Sensor Prior to performing replacement procedures, disarm air bag system. Refer to, Service and Repair/ Air Bag System Disarming & Air Bag System Arming. Refer to, / Specifications/ Mechanical for torque values when installing components. All sensors and mounting bracket bolts must be carefully torqued to assure proper operation. Never power up the air bag system when any sensor is not rigidly attached to the vehicle, since the sensor could be activated when not attached, causing air bag deployment. 1. disconnect sensor electrical connector from retainer, remove Connector Position Assurance (CPA) lock from connector, then disconnect connector. 2. Remove sensor mounting bolts and sensor from vehicle. 3. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Restraint Systems > Impact Sensor > Component Information > Service and Repair > Arming Sensor > Page 1685 Impact Sensor: Service and Repair Forward Discriminating Sensor Prior to performing replacement procedures, disarm air bag system. Refer to, Service and Repair/ Air Bag System Disarming & Air Bag System Arming. Refer to, / Specifications/ Mechanical for torque values when installing components. All sensors and mounting bracket bolts must be carefully torqued to assure proper operation. Never power up the air bag system when any sensor is not rigidly attached to the vehicle, since the sensor could be activated when not attached, causing air bag deployment. 1. Disconnect sensor electrical connector from retainer, then remove connector from Connector Position Assurance (CPA) lock and disconnect. 2. Remove sensor mounting bolts, then the sensor from vehicle. 3. Reverse procedure to install. Ensure arrow is pointed toward front of vehicle. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Restraint Systems > Seat Occupant Sensor > Component Information > Technical Service Bulletins > Restraints - Passenger Presence System Information Seat Occupant Sensor: Technical Service Bulletins Restraints - Passenger Presence System Information INFORMATION Bulletin No.: 06-08-50-009F Date: December 23, 2010 Subject: Information on Passenger Presence Sensing System (PPS or PSS) Concerns With Custom Upholstery, Accessory Seat Heaters or Other Comfort Enhancing Devices Models: 2011 and Prior GM Passenger Cars and Trucks Equipped with Passenger Presence Sensing System Supercede: This bulletin is being revised to update the model years. Please discard Corporate Bulletin Number 06-08-50-009E (Section 08 - Body and Accessories). Concerns About Safety and Alterations to the Front Passenger Seat Important ON A GM VEHICLE EQUIPPED WITH A PASSENGER SENSING SYSTEM, USE THE SEAT COVERS AND OTHER SEAT-RELATED EQUIPMENT AS RELEASED BY GM FOR THAT VEHICLE. DO NOT ALTER THE SEAT COVERS OR SEAT-RELATED EQUIPMENT. ANY ALTERATIONS TO SEAT COVERS OR GM ACCESSORIES DEFEATS THE INTENDED DESIGN OF THE SYSTEM. GM WILL NOT BE LIABLE FOR ANY PROBLEMS CAUSED BY USE OF SUCH IMPROPER SEAT ALTERATIONS, INCLUDING ANY WARRANTY REPAIRS INCURRED. The front passenger seat in many GM vehicles is equipped with a passenger sensing system that will turn off the right front passenger's frontal airbag under certain conditions, such as when an infant or child seat is present. In some vehicles, the passenger sensing system will also turn off the right front passenger's seat mounted side impact airbag. For the system to function properly, sensors are used in the seat to detect the presence of a properly-seated occupant. The passenger sensing system may not operate properly if the original seat trim is replaced (1) by non-GM covers, upholstery or trim, or (2) by GM covers, upholstery or trim designed for a different vehicle or (3) by GM covers, upholstery or trim that has been altered by a trim shop, or (4) if any object, such as an aftermarket seat heater or a comfort enhancing pad or device is installed under the seat fabric or between the occupant and the seat fabric. Aftermarket Seat Heaters, Custom Upholstery, and Comfort Enhancing Pads or Devices Important ON A GM VEHICLE EQUIPPED WITH A PASSENGER SENSING SYSTEM, USE ONLY SEAT COVERS AND OTHER SEAT-RELATED EQUIPMENT RELEASED AS GM ACCESSORIES FOR THAT VEHICLE. DO NOT USE ANY OTHER TYPE OF SEAT COVERS OR SEAT-RELATED EQUIPMENT, OR GM ACCESSORIES RELEASED FOR OTHER VEHICLE APPLICATIONS. GM WILL NOT BE LIABLE FOR ANY PROBLEMS CAUSED BY USE OF SUCH IMPROPER SEAT ACCESSORIES, INCLUDING ANY WARRANTY REPAIRS MADE NECESSARY BY SUCH USE. Many types of aftermarket accessories are available to customers, upfitting shops, and dealers. Some of these devices sit on top of, or are Velcro(R) strapped to the seat while others such as seat heaters are installed under the seat fabric. Additionally, seat covers made of leather or other materials may have different padding thickness installed that could prevent the Passenger Sensing System from functioning properly. Never alter the vehicle seats. Never add pads or other devices to the seat cushion, as this may interfere with the operation of the Passenger Sensing System and either prevent proper deployment of the passenger airbag or prevent proper suppression of the passenger air bag. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Restraint Systems > Seat Sensor/Switch > Component Information > Locations Seat Belt Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder Technical Service Bulletin # 73-01-09 Date: 971001 Starting - Revised Procedures for Inop Ignition Cylinder File In Section: 0 - General Information Bulletin No.: 73-01-09 Date: October, 1997 INFORMATION Subject: New Tumblers for Cylinder Recoding, Revised Repair Procedures for Inoperative Ignition Cylinders (Seized/Won't Rotate), Labor Operation/Time Allowances Models: 1995-97 Buick Skylark, Riviera 1995-97 Chevrolet Cavalier 1997 Chevrolet Corvette, Malibu, Venture 1995-97 Oldsmobile Achieva 1997 Oldsmobile Aurora, Cutlass, Silhouette 1995-97 Pontiac Grand Am, Sunfire 1997 Pontiac Grand Prix, Trans Sport 1995-97 Chevrolet and GMC C/K, S/T Models 1996-97 Chevrolet and GMC G, M/L Vans 1996-97 Oldsmobile Bravada The information in this bulletin concerns new designed tumblers for recoding lock cylinders that use double sided reversible keys, revised procedures for servicing ignition lock cylinders that are seized or not able to rotate and revised labor time guide information and allowances. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1703 The existing labor operation (E7200) has been changed to include "Add" conditions for cylinders that will not rotate. New Tumblers New tumblers are available from GMSPO for recoding lock cylinders that use double-sided reversible keys. These new tumblers should be used immediately and information about the disposition of original tumblers will be provided by GMSPO. Figure 1 shows the new tumbler profile. The shaded area was part of the original tumbler profile, and is removed on the new tumblers. The new part numbers for the tumblers are as follows: Part No. 2852732 = Tumbler # 1 Part No. 2852733 = Tumbler # 2 Part No. 2852734 = Tumbler # 3 Part No. 2852735 = Tumbler # 4 Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. New Procedures For Seized/Won't Rotate Column Mounted Ign. CYL. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1704 A. On G, J and N Models: DO NOT REMOVE THE STEERING COLUMN as indicated in the Service Manual procedure. 1. Remove the tilt lever, upper and lower column covers. 2. Drill hole in module housing as indicated in the illustration using a short drill bit (1/8" followed by 9/32") and 90 degree drill motor or go degree drill attachment to break or access the retaining spring for the lock cylinder button, see Figure 2. 3. Using a pick or needle nose pliers, remove the retaining spring from the hole. 4. Using pliers, grasp and remove the retaining button for the cylinder. 5. Remove the cylinder from the housing. 6. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 7. Install the new cylinder and reinstall the steering column components. B. On U, W, and light duty trucks, follow the Service Manual procedure for keys missing, or cylinders won't rotate. Procedure: Instrument Panel Mounted Switches Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1705 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Component Information > Locations Starter Relay: Locations In Underhood Fuse - Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Other Service Bulletins for Ignition Switch Lock Cylinder: > 01-07-30-023B > Mar > 02 > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder Technical Service Bulletin # 73-01-09 Date: 971001 Starting - Revised Procedures for Inop Ignition Cylinder File In Section: 0 - General Information Bulletin No.: 73-01-09 Date: October, 1997 INFORMATION Subject: New Tumblers for Cylinder Recoding, Revised Repair Procedures for Inoperative Ignition Cylinders (Seized/Won't Rotate), Labor Operation/Time Allowances Models: 1995-97 Buick Skylark, Riviera 1995-97 Chevrolet Cavalier 1997 Chevrolet Corvette, Malibu, Venture 1995-97 Oldsmobile Achieva 1997 Oldsmobile Aurora, Cutlass, Silhouette 1995-97 Pontiac Grand Am, Sunfire 1997 Pontiac Grand Prix, Trans Sport 1995-97 Chevrolet and GMC C/K, S/T Models 1996-97 Chevrolet and GMC G, M/L Vans 1996-97 Oldsmobile Bravada The information in this bulletin concerns new designed tumblers for recoding lock cylinders that use double sided reversible keys, revised procedures for servicing ignition lock cylinders that are seized or not able to rotate and revised labor time guide information and allowances. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Other Service Bulletins for Ignition Switch Lock Cylinder: > 01-07-30-023B > Mar > 02 > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1717 The existing labor operation (E7200) has been changed to include "Add" conditions for cylinders that will not rotate. New Tumblers New tumblers are available from GMSPO for recoding lock cylinders that use double-sided reversible keys. These new tumblers should be used immediately and information about the disposition of original tumblers will be provided by GMSPO. Figure 1 shows the new tumbler profile. The shaded area was part of the original tumbler profile, and is removed on the new tumblers. The new part numbers for the tumblers are as follows: Part No. 2852732 = Tumbler # 1 Part No. 2852733 = Tumbler # 2 Part No. 2852734 = Tumbler # 3 Part No. 2852735 = Tumbler # 4 Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. New Procedures For Seized/Won't Rotate Column Mounted Ign. CYL. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Other Service Bulletins for Ignition Switch Lock Cylinder: > 01-07-30-023B > Mar > 02 > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1718 A. On G, J and N Models: DO NOT REMOVE THE STEERING COLUMN as indicated in the Service Manual procedure. 1. Remove the tilt lever, upper and lower column covers. 2. Drill hole in module housing as indicated in the illustration using a short drill bit (1/8" followed by 9/32") and 90 degree drill motor or go degree drill attachment to break or access the retaining spring for the lock cylinder button, see Figure 2. 3. Using a pick or needle nose pliers, remove the retaining spring from the hole. 4. Using pliers, grasp and remove the retaining button for the cylinder. 5. Remove the cylinder from the housing. 6. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 7. Install the new cylinder and reinstall the steering column components. B. On U, W, and light duty trucks, follow the Service Manual procedure for keys missing, or cylinders won't rotate. Procedure: Instrument Panel Mounted Switches Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Other Service Bulletins for Ignition Switch Lock Cylinder: > 01-07-30-023B > Mar > 02 > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1719 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder Technical Service Bulletin # 73-01-09 Date: 971001 Starting - Revised Procedures for Inop Ignition Cylinder File In Section: 0 - General Information Bulletin No.: 73-01-09 Date: October, 1997 INFORMATION Subject: New Tumblers for Cylinder Recoding, Revised Repair Procedures for Inoperative Ignition Cylinders (Seized/Won't Rotate), Labor Operation/Time Allowances Models: 1995-97 Buick Skylark, Riviera 1995-97 Chevrolet Cavalier 1997 Chevrolet Corvette, Malibu, Venture 1995-97 Oldsmobile Achieva 1997 Oldsmobile Aurora, Cutlass, Silhouette 1995-97 Pontiac Grand Am, Sunfire 1997 Pontiac Grand Prix, Trans Sport 1995-97 Chevrolet and GMC C/K, S/T Models 1996-97 Chevrolet and GMC G, M/L Vans 1996-97 Oldsmobile Bravada The information in this bulletin concerns new designed tumblers for recoding lock cylinders that use double sided reversible keys, revised procedures for servicing ignition lock cylinders that are seized or not able to rotate and revised labor time guide information and allowances. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1727 The existing labor operation (E7200) has been changed to include "Add" conditions for cylinders that will not rotate. New Tumblers New tumblers are available from GMSPO for recoding lock cylinders that use double-sided reversible keys. These new tumblers should be used immediately and information about the disposition of original tumblers will be provided by GMSPO. Figure 1 shows the new tumbler profile. The shaded area was part of the original tumbler profile, and is removed on the new tumblers. The new part numbers for the tumblers are as follows: Part No. 2852732 = Tumbler # 1 Part No. 2852733 = Tumbler # 2 Part No. 2852734 = Tumbler # 3 Part No. 2852735 = Tumbler # 4 Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. New Procedures For Seized/Won't Rotate Column Mounted Ign. CYL. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1728 A. On G, J and N Models: DO NOT REMOVE THE STEERING COLUMN as indicated in the Service Manual procedure. 1. Remove the tilt lever, upper and lower column covers. 2. Drill hole in module housing as indicated in the illustration using a short drill bit (1/8" followed by 9/32") and 90 degree drill motor or go degree drill attachment to break or access the retaining spring for the lock cylinder button, see Figure 2. 3. Using a pick or needle nose pliers, remove the retaining spring from the hole. 4. Using pliers, grasp and remove the retaining button for the cylinder. 5. Remove the cylinder from the housing. 6. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 7. Install the new cylinder and reinstall the steering column components. B. On U, W, and light duty trucks, follow the Service Manual procedure for keys missing, or cylinders won't rotate. Procedure: Instrument Panel Mounted Switches Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 1729 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON Torque Converter Clutch Solenoid: All Technical Service Bulletins A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-023B Date: March, 2002 TECHNICAL Subject: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1999-2000 Cadillac Escalade 1996-2000 Chevrolet Camaro, Corvette 1996-2000 Pontiac Firebird 1996-2000 Chevrolet and GMC Light Duty Truck Models 1996-2000 Oldsmobile Bravada with 4L60-E Automatic Transmission (RPO M30) Built Prior to January 15, 2000 (Julian Date 0015) This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 Transmission/Transaxle). Condition Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated. Diagnosis Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs. The scan tool may show a DTC P1870 set as a history code. A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93° C (200°F). Cause The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply. Important: ^ DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code. ^ When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result. ^ This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle). ^ When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code. ^ When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL). Correction Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 1735 regulator and isolator valves. Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body. ^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears). ^ The torque converter is not blue or overheated. ^ The transmission fluid is not burned or has no burned odor ^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 1736 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > Customer Interest: > 01-07-30-021 > May > 01 > Park/Neutral Switch - Connector Hard to Remove Neutral Safety Switch: Customer Interest Park/Neutral Switch - Connector Hard to Remove File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-021 Date: May, 2001 TECHNICAL Subject: Park/Neutral Position Switch Connector Cannot Be Removed (Replace Switch and Connectors) Models: 1997-2001 Chevrolet Camaro, Corvette 1997-2001 Pontiac Firebird 1995-2001 Chevrolet and GMC S/T Models 1996-2001 Chevrolet and GMC C/K, M/L, G and P Models 1996-2001 Oldsmobile Bravada with 4L60E (M30), 4L65E (M32), 4LBOE (MT1) or Allison LCT (M74) Automatic Transmission This bulletin is being revised to change a labor operation number, add models, model years and transmission designations. Please discard Corporate Bulletin Number 83-71-10A (Section 7 Transmission). Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer concerns, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to ensure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to ensure water-tight connections. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > Customer Interest: > 01-07-30-021 > May > 01 > Park/Neutral Switch - Connector Hard to Remove > Page 1745 For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 01-07-30-021 > May > 01 > Park/Neutral Switch - Connector Hard to Remove Neutral Safety Switch: All Technical Service Bulletins Park/Neutral Switch - Connector Hard to Remove File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-021 Date: May, 2001 TECHNICAL Subject: Park/Neutral Position Switch Connector Cannot Be Removed (Replace Switch and Connectors) Models: 1997-2001 Chevrolet Camaro, Corvette 1997-2001 Pontiac Firebird 1995-2001 Chevrolet and GMC S/T Models 1996-2001 Chevrolet and GMC C/K, M/L, G and P Models 1996-2001 Oldsmobile Bravada with 4L60E (M30), 4L65E (M32), 4LBOE (MT1) or Allison LCT (M74) Automatic Transmission This bulletin is being revised to change a labor operation number, add models, model years and transmission designations. Please discard Corporate Bulletin Number 83-71-10A (Section 7 Transmission). Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer concerns, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to ensure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to ensure water-tight connections. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 01-07-30-021 > May > 01 > Park/Neutral Switch - Connector Hard to Remove > Page 1751 For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 83-71-10 > May > 98 > A/T - Park/Neutral Switch Connector Cannot Be Removed Neutral Safety Switch: All Technical Service Bulletins A/T - Park/Neutral Switch Connector Cannot Be Removed File In Section: 7 - Transmission Bulletin No.: 83-71-10 Date: May, 1998 Subject: Park (Neutral Position Switch Connector Cannot be Removed (Replace Switch and Connectors) Models: 1997-98 Chevrolet Corvette 1995-98 Chevrolet and GMC S/T Models 1996-98 Chevrolet and GMC M/L, P Models 1996-99 Chevrolet and GMC C/K, G Models 1996-98 Oldsmobile Bravada Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer conditions, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to insure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to insure water-tight connections. Parts Information P/N Description 12450016 Switch 15305925 4-Way Connector Assembly 15305887 7-Way Connector Assembly Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Other Service Bulletins for Neutral Safety Switch: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair Grounding Point: All Technical Service Bulletins Electrical - Information For Electrical Ground Repair INFORMATION Bulletin No.: 10-08-45-001B Date: October 25, 2010 Subject: Information for Electrical Ground Repair - Use New Replacement Fasteners with Conductive Finish Models: 2011 and Prior GM Passenger Cars and Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add the 2011 model year and update the Warranty Information. Please discard Corporate Bulletin Number 10-08-45-001A (Section 08 - Body and Accessories). Electrical Ground Repair Overview Proper electrical system function relies on secure, stable and corrosion-free electrical ground connections. Loose, stripped, or corroded connections increase the possibility of improper system function and loss of module communication. These conditions may also lead to unnecessary repairs and component replacement. In general, electrical ground connections are accomplished using one, or a combination of the following attachment methods: - Welded M6 stud and nut - Welded M6 nut and bolt - Welded M8 nut and bolt Determine which attachment method is used and perform the appropriate or alternative repair as described in this bulletin. M6 Weld Stud Replacement Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. Select a location adjacent the damaged or missing M6 ground stud having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the M6 conductive rivet stud flange. 2. Using GM approved residue-free solvent or equivalent, remove any grease from the repair site and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 3. Drill a 10 mm (0.40 in) diameter hole through the panel. 4. Remove paint and primer from the area surrounding the 10 mm (0.40 in) hole until bare metal is visible. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Other Service Bulletins for Neutral Safety Switch: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 1761 Important The M6 conductive rivet stud as shown, can accommodate a panel thickness range of 0.7-4.2 mm (0.03-0.17 in). If there are layers of sheet metal, they should be touching without any air gaps to ensure a good ground. 5. Select a M6 conductive rivet stud. Refer to the Parts Information section of this bulletin. Note Use the GE-50317 rivet stud tool kit. 6. Place the M6 conductive rivet stud (1) in the 10 mm (0.40 in) hole. Assemble the rivet stud tool (2) with the groove and flare side facing the rivet stud, then the washer and the M6 nut (3). 7. Using a wrench on the rivet stud tool, and a socket on the M6 nut, secure the M6 conductive rivet stud. 8. Ensure the rivet stud is securely fastened, WITHOUT ANY detectable movement. 9. Completely wrap the threads of the rivet stud with painters tape or equivalent. Note The rivet stud and surrounding panel area MUST BE properly refinished PRIOR to the installation of the ground wire terminal and conductive nut to maintain a secure, stable and corrosion-free electrical ground. 10. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 11. Allow the refinished repair area to cure sufficiently before removing the protective material applied to the rivet stud threads. 12. Remove the painters tape or equivalent from the rivet stud threads. 13. Using GM approved residue-free solvent or equivalent, thoroughly clean the rivet stud threads to remove any adhesive and allow to dry. 14. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive rivet stud. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Other Service Bulletins for Neutral Safety Switch: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 1762 15. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 16. Install the electrical ground wire terminal to the rivet stud. 17. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 18. Install the M6 conductive nut to the rivet stud and: Tighten Tighten to 8 Nm (71 lb in). 19. Verify proper system operation. M6 Weld Nut Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M6 weld nut at the electrical ground location is damaged or stripped, a M7 conductive self-threading bolt may be used to secure the ground wire terminal. 2. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the weld nut and allow to dry. 3. Remove any loose metal particles from the damaged or stripped weld nut with a stiff brush. 4. Select a M7 conductive self-threading bolt. Refer to the Parts Information section of this bulletin 5. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M7 conductive self-threading bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 6. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 7. Install the electrical ground wire terminal to the M7 conductive self-threading bolt. 8. Install the M7 conductive self-threading bolt and: Tighten Tighten to 9 Nm (80 lb in). 9. Verify proper system operation. M6 Weld Nut Alternative Repair Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the electrical ground location is accessible from both sides of the panel, a M6 conductive bolt and a M6 conductive nut may be used to secure the electrical ground wire terminal. Refer to the Parts Information section of this bulletin. 2. Select a location adjacent the damaged M6 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the new electrical ground site. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the ground location and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 8.5 mm (0.33 in) diameter hole through the panel. 5. Remove paint and primer from the area surrounding the 8.5 mm (0.33 in) hole until bare metal is visible. 6. Select a M6 conductive bolt. Refer to the Parts Information section of this bulletin. 7. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 8. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 9. Install the electrical ground wire terminal and the M6 conductive bolt to the ground location. 10. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 11. Install the M6 conductive nut to the bolt and: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Other Service Bulletins for Neutral Safety Switch: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 1763 Tighten Tighten to 8 Nm (71 lb in). Note The repair area MUST BE properly refinished to maintain a secure, stable and corrosion-free electrical ground. 12. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 13. Verify proper system operation. M8 Weld Nut Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M8 weld nut electrical ground location is accessible from both sides of the panel, a M8 conductive bolt and a M8 conductive nut may be used to secure the electrical ground wire terminal. Refer to the Parts Information section of this bulletin. 2. Select a location adjacent the M8 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the new electrical ground site. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the ground location and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 10 mm (0.40 in) diameter hole through the panel. 5. Remove paint and primer from the area surrounding the 10 mm (0.40 in) hole until bare metal is visible. 6. Select a M8 conductive bolt. Refer to the Parts Information section of this bulletin. 7. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M8 conductive bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 8. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 9. Install the electrical ground wire terminal and the M8 conductive bolt to the ground location. 10. Select a M8 conductive nut. Refer to the Parts Information section of this bulletin. 11. Install the M8 conductive nut to the bolt and: Tighten Tighten to 22 Nm (16 lb ft). Note The repair area MUST BE properly refinished to maintain a secure, stable and corrosion-free electrical ground. 12. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 13. Verify proper system operation. M8 Weld Nut Alternative Repair Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M8 weld nut electrical ground location is not accessible from both sides of the panel, a M6 conductive rivet stud and a M6 conductive nut may be used to secure the electrical ground wire terminal. 2. Select a location adjacent the damaged M8 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the M6 conductive rivet stud flange. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the repair site and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 10 mm (0.40 in) diameter hole through the panel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Other Service Bulletins for Neutral Safety Switch: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 1764 5. Remove paint and primer from the area surrounding the 10 mm (0.40 in) until bare metal is visible. Important The M6 conductive rivet stud as shown, can accommodate a panel thickness range of 0.7-4.2 mm (0.03-0.17 in). If there are layers of sheet metal, they should be touching without any air gaps to ensure a good ground. 6. Select a M6 conductive rivet stud. Refer to the Parts Information section of this bulletin. Note Use the GE-50317 rivet stud tool kit. 7. Place the M6 conductive rivet stud (1) in the 10 mm (0.40 in) hole. Assemble the rivet stud tool (2) with the groove and flare side facing the rivet stud, then the washer and the M6 nut (3). 8. Using a wrench on the rivet stud tool, and a socket on the M6 nut, secure the M6 conductive rivet stud. 9. Ensure the new rivet stud is securely fastened, WITHOUT ANY detectable movement. 10. Completely wrap the threads of the rivet stud with painters tape or equivalent. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Other Service Bulletins for Neutral Safety Switch: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 1765 Note The rivet stud and surrounding panel area MUST BE properly refinished PRIOR to the installation of the electrical ground wire terminal and conductive nut to maintain a secure, stable and corrosion-free electrical ground. 11. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 12. Allow the refinished repair area to cure sufficiently before removing the protective material applied to the rivet stud threads. 13. Remove the painters tape or equivalent from the rivet stud threads. 14. Using GM approved residue-free solvent or equivalent, thoroughly clean the rivet stud threads to remove any adhesive and allow to dry. 15. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive rivet stud. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 16. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 17. Install the electrical ground wire terminal to the M6 conductive rivet stud. 18. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 19. Install the M6 conductive nut to the rivet stud and: Tighten Tighten to 8 Nm (71 lb in) 20. Verify proper system operation. Parts Information Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Other Service Bulletins for Neutral Safety Switch: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 1766 For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Other Service Bulletins for Neutral Safety Switch: > 66-71-04 > May > 96 > A/T - 1-2 or 2-3 Slip/Flare, Launch Shudder & DTC P1870 Grounding Point: All Technical Service Bulletins A/T - 1-2 or 2-3 Slip/Flare, Launch Shudder & DTC P1870 66-71-04 CHEVROLET Issued: 05/10/96 SUBJECT: AUTOMATIC TRANSMISSION 1-2 AND/OR 2-3 UPSHIFT SLIP/FLARE, NO 3RD OR 4TH GEAR, LAUNCH SHUDDER, DTC P1870 (REVISE VCM WIRING) MODELS: 1996 CHEVROLET AND GMC C/K, S/T, M/L, G1, G2 AND P3 MODELS 1996 OLDSMOBILE BRAVADA WITH VCM AND 4L60-E (M30) OR 4L80-E (M11) AUTOMATIC TRANSMISSION CONDITION: SOME OWNERS MAY COMMENT THAT THE AUTOMATIC TRANSMISSION HAS EITHER A SLIP OR FLARE ON THE 1-2 AND/OR 2-3 UPSHIFT, OR NO 3RD OR 4TH GEAR, OR LAUNCH SHUDDER. DTC P1870 MAY ALSO BE STORED IN THE VCM. CAUSE: A POOR INTERNAL GROUND BETWEEN THE TWO CIRCUIT BOARDS OF THE VCM CAN CAUSE THE VCM TO COMMAND ERRATIC LINE PRESSURE AT THE PRESSURE CONTROL SOLENOIDS (PCS). CORRECTION: USING HARNESS JUMPER WIRE AND INSTRUCTION KIT, P/N 12167310, REVISE THE WIRING HARNESS AT THE VCM CONNECTOR. CORRECTIONS WERE MADE TO THE VCM BEGINNING 2/14/96. THE CORRECTED VCM'S ARE IDENTIFIED WITH SERVICE NUMBER 16244210 ON THE VCM IDENTIFICATION LABEL. SERVICE PROCEDURE THE FOLLOWING IS A SUMMARY OF THE INSTRUCTIONS INCLUDED WITH THE SERVICE KIT: 1. REMOVE THE NEGATIVE TERMINAL FROM THE BATTERY. 2. MOVE THE WIRE LOCATED AT CONNECTOR J3 (WHITE/GRAY/CLEAR), PIN 18 TO CONNECTOR J1 (BLUE), PIN 23. 3. INSTALL THE JUMPER WIRE BETWEEN CONNECTOR J2 (RED), PIN 26 AND CONNECTOR J3 (WHITE/GREY/CLEAR), PIN 18. 4. INSTALL THE TAG INCLUDED IN THE KIT AROUND THE VCM WIRING HARNESS. THIS TAG NOTES THAT THE WIRING HARNESS HAS BEEN MODIFIED. 5. RECONNECT THE NEGATIVE BATTERY TERMINAL. ROAD TEST TO VERIFY THAT THE CONDITION HAS BEEN CORRECTED. IF ANY OF THE FOLLOWING CONDITIONS ARE NOTED, THE TRANSMISSION SHOULD BE REPLACED, OR FOR CANADIAN DEALERS, REPAIRED. - TRANSMISSION FLUID OXIDATION OR EXCESSIVE SEDIMENT. - TRANSMISSION SLIP OR FLARE AFTER THIS SERVICE FIX IS PERFORMED. - DTC P1870 IS STORED ON A 4L60-E (M30). THE FOLLOWING TOOLS ARE AVAILABLE FROM KENT-MOORE (1-800-345-2233) FOR USE IN REMOVING AND RELATING THE VCM CONNECTOR. - J41759 PUNCH: USED TO PUNCH A NEW HOLE THROUGH THE CONNECTOR SEAL. PARTS INFORMATION P/N DESCRIPTION QTY 12167310 HARNESS JUMPER WIRE KIT 1 PARTS ARE EXPECTED TO BE AVAILABLE ON 5/13/96 FROM GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Other Service Bulletins for Neutral Safety Switch: > 66-71-04 > May > 96 > A/T - 1-2 or 2-3 Slip/Flare, Launch Shudder & DTC P1870 > Page 1771 WARRANTY INFORMATION FOR VEHICLES REPAIRED UNDER WARRANTY, USE: LABOR OP DESCRIPTION LABOR TIME N6112 WIRE REPAIR USE PUBLISHED FRONT CHASSIS LABOR OPERATION TIME Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Other Service Bulletins for Neutral Safety Switch: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 1777 Important The M6 conductive rivet stud as shown, can accommodate a panel thickness range of 0.7-4.2 mm (0.03-0.17 in). If there are layers of sheet metal, they should be touching without any air gaps to ensure a good ground. 5. Select a M6 conductive rivet stud. Refer to the Parts Information section of this bulletin. Note Use the GE-50317 rivet stud tool kit. 6. Place the M6 conductive rivet stud (1) in the 10 mm (0.40 in) hole. Assemble the rivet stud tool (2) with the groove and flare side facing the rivet stud, then the washer and the M6 nut (3). 7. Using a wrench on the rivet stud tool, and a socket on the M6 nut, secure the M6 conductive rivet stud. 8. Ensure the rivet stud is securely fastened, WITHOUT ANY detectable movement. 9. Completely wrap the threads of the rivet stud with painters tape or equivalent. Note The rivet stud and surrounding panel area MUST BE properly refinished PRIOR to the installation of the ground wire terminal and conductive nut to maintain a secure, stable and corrosion-free electrical ground. 10. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 11. Allow the refinished repair area to cure sufficiently before removing the protective material applied to the rivet stud threads. 12. Remove the painters tape or equivalent from the rivet stud threads. 13. Using GM approved residue-free solvent or equivalent, thoroughly clean the rivet stud threads to remove any adhesive and allow to dry. 14. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive rivet stud. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Other Service Bulletins for Neutral Safety Switch: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 1778 15. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 16. Install the electrical ground wire terminal to the rivet stud. 17. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 18. Install the M6 conductive nut to the rivet stud and: Tighten Tighten to 8 Nm (71 lb in). 19. Verify proper system operation. M6 Weld Nut Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M6 weld nut at the electrical ground location is damaged or stripped, a M7 conductive self-threading bolt may be used to secure the ground wire terminal. 2. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the weld nut and allow to dry. 3. Remove any loose metal particles from the damaged or stripped weld nut with a stiff brush. 4. Select a M7 conductive self-threading bolt. Refer to the Parts Information section of this bulletin 5. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M7 conductive self-threading bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 6. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 7. Install the electrical ground wire terminal to the M7 conductive self-threading bolt. 8. Install the M7 conductive self-threading bolt and: Tighten Tighten to 9 Nm (80 lb in). 9. Verify proper system operation. M6 Weld Nut Alternative Repair Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the electrical ground location is accessible from both sides of the panel, a M6 conductive bolt and a M6 conductive nut may be used to secure the electrical ground wire terminal. Refer to the Parts Information section of this bulletin. 2. Select a location adjacent the damaged M6 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the new electrical ground site. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the ground location and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 8.5 mm (0.33 in) diameter hole through the panel. 5. Remove paint and primer from the area surrounding the 8.5 mm (0.33 in) hole until bare metal is visible. 6. Select a M6 conductive bolt. Refer to the Parts Information section of this bulletin. 7. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 8. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 9. Install the electrical ground wire terminal and the M6 conductive bolt to the ground location. 10. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 11. Install the M6 conductive nut to the bolt and: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Other Service Bulletins for Neutral Safety Switch: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 1779 Tighten Tighten to 8 Nm (71 lb in). Note The repair area MUST BE properly refinished to maintain a secure, stable and corrosion-free electrical ground. 12. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 13. Verify proper system operation. M8 Weld Nut Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M8 weld nut electrical ground location is accessible from both sides of the panel, a M8 conductive bolt and a M8 conductive nut may be used to secure the electrical ground wire terminal. Refer to the Parts Information section of this bulletin. 2. Select a location adjacent the M8 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the new electrical ground site. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the ground location and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 10 mm (0.40 in) diameter hole through the panel. 5. Remove paint and primer from the area surrounding the 10 mm (0.40 in) hole until bare metal is visible. 6. Select a M8 conductive bolt. Refer to the Parts Information section of this bulletin. 7. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M8 conductive bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 8. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 9. Install the electrical ground wire terminal and the M8 conductive bolt to the ground location. 10. Select a M8 conductive nut. Refer to the Parts Information section of this bulletin. 11. Install the M8 conductive nut to the bolt and: Tighten Tighten to 22 Nm (16 lb ft). Note The repair area MUST BE properly refinished to maintain a secure, stable and corrosion-free electrical ground. 12. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 13. Verify proper system operation. M8 Weld Nut Alternative Repair Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M8 weld nut electrical ground location is not accessible from both sides of the panel, a M6 conductive rivet stud and a M6 conductive nut may be used to secure the electrical ground wire terminal. 2. Select a location adjacent the damaged M8 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the M6 conductive rivet stud flange. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the repair site and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 10 mm (0.40 in) diameter hole through the panel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Other Service Bulletins for Neutral Safety Switch: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 1780 5. Remove paint and primer from the area surrounding the 10 mm (0.40 in) until bare metal is visible. Important The M6 conductive rivet stud as shown, can accommodate a panel thickness range of 0.7-4.2 mm (0.03-0.17 in). If there are layers of sheet metal, they should be touching without any air gaps to ensure a good ground. 6. Select a M6 conductive rivet stud. Refer to the Parts Information section of this bulletin. Note Use the GE-50317 rivet stud tool kit. 7. Place the M6 conductive rivet stud (1) in the 10 mm (0.40 in) hole. Assemble the rivet stud tool (2) with the groove and flare side facing the rivet stud, then the washer and the M6 nut (3). 8. Using a wrench on the rivet stud tool, and a socket on the M6 nut, secure the M6 conductive rivet stud. 9. Ensure the new rivet stud is securely fastened, WITHOUT ANY detectable movement. 10. Completely wrap the threads of the rivet stud with painters tape or equivalent. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Other Service Bulletins for Neutral Safety Switch: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 1781 Note The rivet stud and surrounding panel area MUST BE properly refinished PRIOR to the installation of the electrical ground wire terminal and conductive nut to maintain a secure, stable and corrosion-free electrical ground. 11. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 12. Allow the refinished repair area to cure sufficiently before removing the protective material applied to the rivet stud threads. 13. Remove the painters tape or equivalent from the rivet stud threads. 14. Using GM approved residue-free solvent or equivalent, thoroughly clean the rivet stud threads to remove any adhesive and allow to dry. 15. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive rivet stud. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 16. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 17. Install the electrical ground wire terminal to the M6 conductive rivet stud. 18. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 19. Install the M6 conductive nut to the rivet stud and: Tighten Tighten to 8 Nm (71 lb in) 20. Verify proper system operation. Parts Information Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Other Service Bulletins for Neutral Safety Switch: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 1782 For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Other Service Bulletins for Neutral Safety Switch: > 66-71-04 > May > 96 > A/T - 1-2 or 2-3 Slip/Flare, Launch Shudder & DTC P1870 > Page 1787 WARRANTY INFORMATION FOR VEHICLES REPAIRED UNDER WARRANTY, USE: LABOR OP DESCRIPTION LABOR TIME N6112 WIRE REPAIR USE PUBLISHED FRONT CHASSIS LABOR OPERATION TIME Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Locations > With 4L60-E Transmission Electronic 4-speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Locations > With 4L60-E Transmission > Page 1790 Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions Neutral Safety Switch: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1793 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1794 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1795 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1796 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1797 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1798 Neutral Safety Switch: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1799 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1800 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1801 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1802 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1803 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1804 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1805 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1806 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1807 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1808 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1809 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1810 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1811 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1812 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1813 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1814 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1815 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1816 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1817 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1818 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1819 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1820 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1821 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1822 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1823 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 1824 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Technical Service Bulletins > A/T - Park/Neutral Switch Connector Cannot Be Removed Transmission Position Switch/Sensor: Technical Service Bulletins A/T - Park/Neutral Switch Connector Cannot Be Removed File In Section: 7 - Transmission Bulletin No.: 83-71-10 Date: May, 1998 Subject: Park (Neutral Position Switch Connector Cannot be Removed (Replace Switch and Connectors) Models: 1997-98 Chevrolet Corvette 1995-98 Chevrolet and GMC S/T Models 1996-98 Chevrolet and GMC M/L, P Models 1996-99 Chevrolet and GMC C/K, G Models 1996-98 Oldsmobile Bravada Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer conditions, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to insure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to insure water-tight connections. Parts Information P/N Description 12450016 Switch 15305925 4-Way Connector Assembly 15305887 7-Way Connector Assembly Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 1833 Transmission Position Switch/Sensor: Locations Park/Neutral Position Switch Electronic 4-Speed Automatic Overdrive Transmission Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 1834 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions Transmission Position Switch/Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1837 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1838 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1839 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1840 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1841 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1842 Transmission Position Switch/Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1843 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1844 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1845 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1846 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1847 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1848 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1849 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1850 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1851 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1852 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1853 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1854 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1855 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1856 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1857 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1858 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1859 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1860 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1861 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1862 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1863 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1864 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1865 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1866 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1867 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1868 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1869 Transmission Position Switch/Sensor: Connector Views C1: Transmission Range Switch C2: Transmission Range Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1870 Transmission Position Switch/Sensor: Electrical Diagrams Electronic PRNDL Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 1871 Starter And Charging (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 1872 Transmission Position Switch/Sensor: Testing and Inspection Pressure Switch Assembly Resistance Check (1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 1873 Pressure Switch Assembly Resistance Check (2 Of 2) Tools Required - J 39775 4L60E Jumper Harness - J 39200 Digital Multimeter - J 35616 Connector Test Adapter Kit Important: Whenever the transmission 20-way connector is disconnected and the engine is running, multiple DTCs will set. Be sure to clear these codes when you are finished with this procedure Important: This procedure tests the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) circuits and the Automatic Transmission Fluid Temperature (TFT) Sensor circuit. Do not use this procedure to test other Automatic Transmission circuits, refer to 4L60-E Automatic Transmission Internal Wiring Harness check. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 1874 Transmission Position Switch/Sensor: Adjustments PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 1875 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 1876 Transmission Position Switch/Sensor: Service and Repair PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 1877 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Speed Sensor, A/T > Component Information > Locations > Transmission Output Speed Sensor, 4L80E Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Speed Sensor, A/T > Component Information > Locations > Transmission Output Speed Sensor, 4L80E > Page 1882 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Windows and Glass > Heated Glass Element Switch > Component Information > Locations Heated Glass Element Switch: Locations LH side of I/P Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Windows and Glass > Power Window Lockout Switch > Component Information > Locations Front Door Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Windows and Glass > Power Window Switch > Component Information > Locations > Power Window Switch, RH Front Power Window Switch: Locations Power Window Switch, RH Front Power Window Switches Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Windows and Glass > Power Window Switch > Component Information > Locations > Power Window Switch, RH Front > Page 1894 Rear Door Wiring On Door Trim Panel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Windows and Glass > Power Window Switch > Component Information > Locations > Power Window Switch, RH Front > Page 1895 Power Window Switch: Locations Power Windows and Door Lock Switch, Passenger Side On LH Door Trim Panel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Windows and Glass > Power Window Switch > Component Information > Locations > Power Window Switch, RH Front > Page 1896 Power Window Switch: Locations RH/LH Power Window Switches Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Windows and Glass > Power Window Switch > Component Information > Locations > Power Window Switch, RH Front > Page 1897 Rear Door Wiring On Door Trim Panel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Windows and Glass > Power Window Switch > Component Information > Diagrams > LH Door Master Power Window Switch LH Door Master Power Window Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Windows and Glass > Power Window Switch > Component Information > Diagrams > LH Door Master Power Window Switch > Page 1900 Power Window Switch: Diagrams Power Window and Door Lock Switch Power Window And Door Lock Switch, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Windows and Glass > Power Window Switch > Component Information > Diagrams > LH Door Master Power Window Switch > Page 1901 Power Window And Door Lock Switch, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Wiper and Washer Systems > Windshield Washer Switch > Component Information > Locations Windshield Washer Switch: Locations At Steering Column, part of Turn Signal Lever Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Wiper and Washer Systems > Windshield Washer Switch > Component Information > Locations > Page 1906 Windshield Washer Switch: Diagrams C230: I/P HARN To HVAC HARN, Rear Window Wiper Washer SW Rear Window Wiper/Washer Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Wiper and Washer Systems > Wiper Switch > Component Information > Locations > Rear Window Wiper & Washer Switch Cargo Lamp Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Wiper and Washer Systems > Wiper Switch > Component Information > Locations > Rear Window Wiper & Washer Switch > Page 1911 Wiper Switch: Locations Windshield Wiper/Washer Switch At Steering Column, part of Turn Signal Lever Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Sensors and Switches > Sensors and Switches - Wiper and Washer Systems > Wiper Switch > Component Information > Locations > Page 1912 Wiper Switch: Diagrams C230: I/P HARN To HVAC HARN, Rear Window Wiper Washer SW Rear Window Wiper/Washer Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Alignment > System Information > Technical Service Bulletins > Steering/Suspension - Wheel Alignment Specifications Alignment: Technical Service Bulletins Steering/Suspension - Wheel Alignment Specifications WARRANTY ADMINISTRATION Bulletin No.: 05-03-07-009C Date: December 09, 2010 Subject: Wheel Alignment Specifications, Requirements and Recommendations for GM Vehicles Models: 2011 and Prior GM Passenger Cars and Light Duty Trucks Supercede: This bulletin is being extensively revised to provide technicians and warranty administrators with an all inclusive guide for wheel alignments. PLEASE FAMILIARIZE YOURSELF WITH THESE UPDATES BEFORE PERFORMING YOUR NEXT GM WHEEL ALIGNMENT SERVICE. Please discard Corporate Bulletin Number 05-03-07-009B (Section 03 - Suspension). Purpose The purpose of this bulletin is to provide retail, wholesale and fleet personnel with General Motors' warranty service requirements and recommendations for customer concerns related to wheel alignment. For your convenience, this bulletin updates and centralizes all of GM's Standard Wheel Alignment Service Procedures, Policy Guidelines and bulletins on wheel alignment warranty service. Important PLEASE FAMILIARIZE YOURSELF WITH THESE UPDATES BEFORE PERFORMING YOUR NEXT GM WHEEL ALIGNMENT SERVICE. The following five (5) key steps are a summary of this bulletin and are REQUIRED in completing a successful wheel alignment service. 1. Verify the vehicle is in an Original Equipment condition for curb weight, tires, wheels, suspension and steering configurations. Vehicles modified in any of these areas are not covered for wheel alignment warranty. 2. Review the customer concern relative to "Normal Operation" definitions. 3. Verify that vehicle is within the "Mileage Policy" range. 4. Document wheel alignment warranty claims appropriately for labor operations E2000 and E2020. The following information must be documented or attached to the repair order: - Customer concern in detail - What corrected the customer concern? - If a wheel alignment is performed: - Consult SI for proper specifications. - Document the "Before" AND "After" wheel alignment measurements/settings. - Completed "Wheel Alignment Repair Order Questionnaire" (form attached to this bulletin) 5. Use the proper wheel alignment equipment (preferred with print-out capability), process and the appropriate calibration maintenance schedules. Important If it is determined that a wheel alignment is necessary under warranty, use the proper labor code for the repair. E2000 for Steering Wheel Angle and/or Front Toe set or E2020 for Wheel Alignment Check/Adjust includes Caster, Camber and Toe set (Wheel alignment labor time for other component repairs is to be charged to the component that causes a wheel alignment operation.). The following flowchart is to help summarize the information detailed in this bulletin and should be used whenever a wheel alignment is performed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Alignment > System Information > Technical Service Bulletins > Steering/Suspension - Wheel Alignment Specifications > Page 1918 Verify Original Equipment Condition of the Vehicle - Verify that Original Equipment Tires and Wheels or Official GM Accessory Tires and Wheels are on the vehicle. - Verify that aftermarket suspension "Lift" or "Lowering" Kits or other suspension alterations have NOT been done to the vehicle. - Check for accidental damage to the vehicle; for example, severe pothole or curb impacts, collision damage that may have affected the wheel alignment of the vehicle; e.g., engine cradles, suspension control arms, axles, wheels, wheel covers, tires may show evidence of damage/impact. - Check to be sure vehicle has seen "Normal Use" rather than abuse; e.g., very aggressive driving may show up by looking at the tires and condition of the vehicle. - Check for other additional equipment items that may significantly affect vehicle mass such as large tool boxes, campers, snow plow packages (without the snowplow RPO), etc., especially in trucks and cutaway/incomplete vehicles. Significant additional mass can affect trim height and wheel alignment of the vehicle and may necessitate a customer pay wheel alignment when placed semi-permanently in the vehicle (Upfitter instructions are to realign the vehicle after placement of these types of items. (This typically applies to trucks and incomplete vehicles that can be upfit with equipment such as the above.) Customer Concerns, "Normal Operation" Conditions and "Mileage Policy" Possible Concerns The following are typical conditions that may require wheel alignment warranty service: 1. Lead/Pull: defined as "at a constant highway speed on a typical straight road, the amount of effort required at the steering wheel to maintain the vehicle's straight heading." Important Please evaluate for the condition with hands-on the steering wheel. Follow the "Vehicle Leads/Pulls" diagnostic tree located in SI to determine the cause of a lead/pull concern. Lead/Pull concerns can be due to road crown or road slope, tires, wheel alignment or even in rare circumstances a steering gear issue. Lead/pull concerns due to road crown are considered "Normal Operation" and are NOT a warrantable condition -- the customer should be advised that this is "Normal Operation." Important Some customers may comment on a "Lead/Pull" when they hold the steering wheel in a level condition. If so, this is more likely a "steering wheel angle" concern because the customer is "steering" the vehicle to obtain a "level" steering wheel. 2. Steering wheel angle to the left or right (counter-clockwise or clockwise, respectively): Defined as the steering wheel angle (clocking) deviation from "level" while maintaining a straight heading on a typical straight road. 3. Irregular or Premature tire wear: Slight to very slight "feathering" or "edge" wear on the shoulders of tires is NOT considered unusual and should even out with a tire rotation; if the customer is concerned about a "feathering" condition of the tires, the customer could be advised to rotate the tires earlier than the next scheduled mileage/maintenance interval (but no later than the next interval). Be sure to understand the customer's driving habits as this will also heavily influence the tire wear performance; tire wear from aggressive or abusive driving habits is NOT a warrantable condition. Important Slight or mild feathering, cupping, edge or heel/toe wear of tire tread shoulders is "normal" and can show up very early in a tire/vehicle service mileage; in fact, some new tires can show evidence of feathering from the factory. These issues do NOT affect the overall performance and tread life of the tire. Dealer personnel should always check the customer's maintenance records to ensure that tire inflation pressure is being maintained to placard and that the tires are being rotated (modified-X pattern) at the proper mileage intervals. Wheel alignments are NOT to be performed for the types of "Normal" Tire Feathering shown in Figures 1-4 below. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Alignment > System Information > Technical Service Bulletins > Steering/Suspension - Wheel Alignment Specifications > Page 1919 Figure 1: Full Tread View - "NORMAL" Tire "Feathering" Wear on the Shoulder/Adjacent/Center Ribs Figure 2: Tire Shoulder View Example 1 - "NORMAL" Tire "Feathering" Wear on the Shoulder Figure 3: Tire Shoulder View Example 2 - "NORMAL" Tire "Feathering" Wear Figure 4: Detail Side View of Tire Shoulder Area - "NORMAL" Tire "Feathering" Wear Important When a wheel alignment is deemed necessary for tire wear, be sure to document on the repair order, in as much detail as possible, the severity and type of tire wear (e.g., severe center wear or severe inside or outside shoulder wear) and the position of the tire on the vehicle (RF, LF, LR, RR). Please note the customer's concern with the wear such as, noise, appearance, wear life, etc. A field product report with pictures of the tire wear condition is recommended. Refer to Corporate Bulletin Number 02-00-89-002J and #07-00-89-036C. 4. Other repairs that affect wheel alignment; e.g., certain component replacement such as suspension control arm replacement, engine cradle adjustment/replace, steering gear replacement, steering tie rod replace, suspension strut/shock, steering knuckle, etc. may require a wheel alignment. Important If other components or repairs are identified as affecting the wheel alignment, policy calls for the wheel alignment labor time to be charged to the replaced/repaired component's labor operation time rather than the wheel alignment labor operations. Important Vibration type customer concerns are generally NOT due to wheel alignment except in the rare cases; e.g., extreme diagonal wear across the tread. In general, wheel alignments are NOT to be performed as an investigation/correction for vibration concerns. "Normal Operation" Conditions Vehicle Lead/Pull Due to Road Crown or Slope: As part of "Normal Operation," vehicles will follow side-to-side or left to right road crown or slope. Be sure to verify from the customer the types of roads they are driving as they may not recognize the influence of road crown on vehicle lead/pull and steering wheel angle. If a vehicle requires significant steering effort to prevent it from "climbing" the road crown there may be an issue to be looked into further. Important Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Alignment > System Information > Technical Service Bulletins > Steering/Suspension - Wheel Alignment Specifications > Page 1920 A wheel alignment will generally NOT correct vehicles that follow the road crown since this is within "Normal Operation." Mileage Policy The following mileage policy applies for E2020 and E2000 labor operations: Note Wheel Alignment is NOT covered under the New Vehicle Limited Warranty for Express and Savana Cutaway vehicles as these vehicles require Upfitters to set the wheel alignment after completing the vehicles. - 0-800 km (0-500 mi): E2000/E2020 claims ONLY allowed with Call Center Authorization. Due to the tie down during shipping, the vehicle's suspension requires some time to reach normal operating position. For this reason, new vehicles are generally NOT to be aligned until they have accumulated at least 800 km (500 mi). A field product report should accompany any claim within this mileage range. - 801-12,000 km (501-7,500 mi): - If a vehicle came from the factory with incorrect alignment settings, any resulting off-angle steering wheel, lead/pull characteristics or the rare occurrence of excessive tire wear would be apparent early in the life of the vehicle. The following policy applies: - Vehicles 100% Factory Set/Measured for Caster/Camber/Toe - Escalade/ESV/EXT, Tahoe/Suburban, Yukon/XL/Denali, Silverado/Sierra, Express/Savana, Corvette and Colorado/Canyon: E2000/E2020 Claims: Call Center Authorization Required - All Vehicles NOT 100% Factory Set/Measured for Caster/Camber/Toe as noted above: E2000/E2020 Claims: Dealer Service Manager Authorization Required - 12,001 km and beyond (7,501 miles and beyond): During this period, customers are responsible for the wheel alignment expense or dealers may provide on a case-by case basis a one-time customer enthusiasm claim up to 16,000 km (10,000 mi). In the event that a defective component required the use of the subject labor operations, the identified defective component labor operation will include the appropriate labor time for a wheel alignment as an add condition to the component repair. Important Only one wheel alignment labor operation claim (E2000 or E2020) may be used per VIN. Warranty Documentation Requirements When a wheel alignment service has been deemed necessary, the following items will need to be clearly documented on/with the repair order: - Customer concern in detail - What corrected the customer concern? - If a wheel alignment is performed: - Consult SI for proper specifications. - Document the "Before" AND "After" wheel alignment measurements/settings. - Completed "Wheel Alignment Repair Order Questionnaire" (form attached to this bulletin) 1. Document the customer concern in as much detail as possible on the repair order and in the warranty administration system. Preferred examples: - Steering wheel is off angle in the counterclockwise direction by approximately x degrees or clocking position. - Vehicle lead/pulls to the right at approximately x-y mph. Vehicle will climb the road crown. Severe, Moderate or Slight. - RF and LF tires are wearing on the outside shoulders with severe feathering. Important In the event of a lead/pull or steering wheel angle concern, please note the direction of lead/pull (left or right) or direction of steering wheel angle (clockwise or counterclockwise) on the repair order and within the warranty claim verbatim. Important In the event of a tire wear concern, please note the position on the vehicle and where the wear is occurring on the tire; i.e., the RF tire is wearing on the inside shoulder. 2. Document the technician's findings on cause and correction of the issue. Examples: - Reset LF toe from 0.45 degrees to 0.10 degrees and RF toe from -0.25 degrees to 0.10 degrees to correct the steering wheel angle from 5 degrees counterclockwise to 0 degrees. - Reset LF camber from 0.25 degrees to -0.05 degrees to correct the cross-camber condition of +0.30 degrees to 0.00 degrees on the vehicle. - Front Sum toe was found to be 0.50 degrees, reset to 0.20 degrees. 3. Print-out the "Before" and "After" wheel alignment measurements/settings and attach them to the Repair Order or if print-out capability is not Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Alignment > System Information > Technical Service Bulletins > Steering/Suspension - Wheel Alignment Specifications > Page 1921 available, measurements may also be clearly and legibly handwritten into the Wheel Alignment Repair Order Questionnaire attached to this bulletin. 4. Attach the Wheel Alignment Repair Order Questionnaire below along with the print-out of "Before" and "After" wheel alignment measurements to the Repair Order and retain for use by GM. Wheel Alignment Equipment and Process Wheel alignments must be performed with a quality machine that will give accurate results when performing checks. "External Reference" (image-based camera technology) is preferred. Please refer to Corporate Bulletin Number 05-00-89-029B: General Motors Dealership Critical Equipment Requirements and Recommendations. Requirements: - Computerized four wheel alignment system. - Computer capable of printing before and after alignment reports. - Computer capable of time and date stamp printout. - Racking system must have jacking capability - Racking system must be capable of level to 1.6 mm (1/16 in) - Appropriate wheel stops and safety certification - Built-in turn plates and slip plates - Wheel clamps capable of attaching to 20" or larger wheels - Racking capable of accepting any GM passenger car or light duty truck - Operator properly trained and ASE-certified (U.S. only) in wheel alignment Recommendations: Racking should have front and rear jacking capability. Equipment Maintenance and Calibration: Alignment machines must be regularly calibrated in order to give correct information. Most manufacturers recommend the following: - Alignment machines with "internal reference" sensors should be checked (and calibrated, if necessary) every six months. - Alignment machines with "external reference" (image-based camera technology) should be checked (and calibrated, if necessary) once a year. - Racks must be kept level to within 1.6 mm (1/16 in). - If any instrument that is part of the alignment machine is dropped or damaged in some way, check the calibration immediately. Check with the manufacturer of your specific equipment for their recommended service/calibration schedule. Wheel Alignment Process When performing wheel alignment measurement and/or adjustment, the following steps should be taken: Preliminary Steps: 1. Verify that the vehicle has a full tank of fuel (compensate as necessary). 2. Inspect the wheels and the tires for damage. 3. Inspect the tires for the proper inflation and irregular tire wear. 4. Inspect the wheel bearings for excessive play. 5. Inspect all suspension and steering parts for looseness, wear, or damage. 6. Inspect the steering wheel for excessive drag or poor return due to stiff or rusted linkage or suspension components. 7. Inspect the vehicle trim height. 8. Compensate for frame angle on targeted vehicles (refer to Wheel Alignment Specifications in SI). Satisfactory vehicle operation may occur over a wide range of alignment angles. However, if the wheel alignment angles are not within the range of specifications, adjust the wheel alignment to the specifications. Refer to Wheel Alignment Specifications in SI. Give consideration to excess loads, such as tool boxes, sample cases, etc. Follow the wheel alignment equipment manufacturer's instructions. Measure/Adjust: Important Prior to making any adjustments to wheel alignment on a vehicle, technicians must verify that the wheel alignment specifications loaded into their wheel alignment machine are up-to-date by comparing these to the wheel alignment specifications for the appropriate model and model year in SI. Using incorrect and/or outdated specifications may result in unnecessary adjustments, irregular and/or premature tire wear and repeat customer concerns Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Alignment > System Information > Technical Service Bulletins > Steering/Suspension - Wheel Alignment Specifications > Page 1922 Important When performing adjustments to vehicles requiring a 4-wheel alignment, set the rear wheel alignment angles first in order to obtain proper front wheel alignment angles. Perform the following steps in order to measure the front and rear alignment angles: 1. Install the alignment equipment according to the manufacturer's instructions. 2. Jounce the front and the rear bumpers 3 times prior to checking the wheel alignment. 3. Measure the alignment angles and record the readings. If necessary, adjust the wheel alignment to vehicle specification and record the before and after measurements. Refer to Wheel Alignment Specifications in SI. Important Technicians must refer to SI for the correct wheel alignment specifications. SI is the only source of GM wheel alignment specifications that is kept up-to-date throughout the year. Test drive vehicle to ensure proper repair. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Alignment > System Information > Technical Service Bulletins > Steering/Suspension - Wheel Alignment Specifications > Page 1923 Frame Angle Measurement (Express / Savana Only) ........ Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Alignment > System Information > Technical Service Bulletins > Steering/Suspension - Wheel Alignment Specifications > Page 1924 What corrected the customer concern and was the repair verified? Please Explain: ............. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Alignment > System Information > Specifications > Vehicle Ride (Trim) Height Specifications Alignment: Specifications Vehicle Ride (Trim) Height Specifications Vehicle Ride Height Location & Specifications "Z" HEIGHT 1. Lift front bumper of vehicle up approximately 1.5 inches. 2. Gently remove hands and allow vehicle to settle on its own. 3. Repeat this operation twice more for a total of three times. 4. Measure "Z" height, Fig. 1. 5. Push front bumper on vehicle down approximately 1.5 inches. 6. Gently remove hands and allow vehicle to rise on its own. 7. Repeat this operation twice more for a total of three times. 8. Measure "Z" height. 9. Find the average of the high and low measurements. This is the "Z" height. "Z" height should be 3.74 inches. "D" HEIGHT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Alignment > System Information > Specifications > Vehicle Ride (Trim) Height Specifications > Page 1927 Use the same procedure used in determining the "Z" height. "D" height should be 7.17 inches. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Alignment > System Information > Specifications > Vehicle Ride (Trim) Height Specifications > Page 1928 Alignment: Specifications Alignment Specifications Caster, Degrees Checking [01] ....................................................................................................................................... ......................................................... 3.75 +/- 2.0 Setting [02] ............................................................. ....................................................................................................................................... 3.75 +/- 1.0 Camber, Degrees Checking [01] ....................................................................................................................................... ........................................................... 0.5 +/- 1.0 Setting [02] ............................................................. ......................................................................................................................................... 0.5 +/- 0.5 Toe-In, Degrees Checking [03] ....................................................................................................................................... ......................................................... 0.24 +/- 0.2 Setting [03] ............................................................. ..................................................................................................................................................... 0.24 Ball Joint Wear, inches [04] ................................................................................................................. ........................................................................... 0.08 Note: Caster angle must be corrected to level frame angle. [01] Left and right side should be equal within +1.0 deg. [02] Left and right side should equal within +0.5 deg. [03] Toe-in left and right side to be set equally per wheel and steering wheel must be held in straight ahead position within +/-5.0 deg. [04] Refer to /Steering & Suspension/ Ball Joint Inspection for inspection procedure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Alignment > System Information > Service and Repair > Front Wheel Alignment Alignment: Service and Repair Front Wheel Alignment Front Caster and Camber Adjustment Vehicle Ride Height Location & Specifications Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Alignment > System Information > Service and Repair > Front Wheel Alignment > Page 1931 Caster Measures CAMBER 1. Determine the camber from the alignment equipment. 2. Install adjustment kit No. 15538596, or equivalent. 3. Reset camber to specifications. CASTER All caster specifications are given with the vehicle frame level (zero angle). 1. Position vehicle on a smooth level surface. 2. If necessary, correct "Z" height. 3. Using a bubble protractor or inclinometer, measure frame angle, Figs. 1 and 2. 4. Note frame angle as being up in the rear or down in the rear. 5. Determine caster angle from alignment equipment. 6. Determine actual (corrected) caster reading, Fig. 2. 7. When measuring caster, note the following: a. A decrease in rear frame angle must be subtracted from a positive caster reading. b. An increase in rear frame angle must be added to a positive caster reading. c. A decrease in rear frame angle must be added to a negative caster reading. d. An increase in rear frame angle must be subtracted from a negative caster reading. 8. If the caster angle is incorrect, correct the caster angle by turning the adjustment cam bolts. Front Toe Adjustment 1. Determine toe-in from the alignment equipment. 2. Change length of both tie rod sleeves to effect a toe change. 3. Toe-in can be increased or decreased by changing the length of the tie rod ends. A threaded sleeve is provided for this purpose. When the tie rod ends are mounted ahead of the steering knuckle they must be decreased in length in order to increase toe-in. When the tie rod ends are mounted behind the steering knuckle they must be lengthened in order to increase toe-in. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Alignment > System Information > Service and Repair > Front Wheel Alignment > Page 1932 Alignment: Service and Repair Camber & Caster Adjustment Kit Installation Fig. 3 Upper Control Arm Removal Fig. 4 Alignment Service Kit 15538596 Installation As originally installed, the upper control arm cannot be adjusted for camber or caster. However, if the camber or caster is measured and found to be out of specification, the camber and caster can be set to proper specifications using adjustment kit 15538596, or equivalent. To install, proceed as follows: 1. Raise and support vehicle and lower control arms, then remove nut (60), washer (61) and bolt (62) from upper control arm bracket (44). Discard nut, washer and bolt. 2. Remove large washers (40), Figs. 3 and 4, which are welded to the upper control arm frame brackets. 3. Remove weld beads from the upper control arm bracket. Grind area smooth. 4. Install adjusting cams (49) to bracket (44). 5. Install bolt (48) and nut (50). 6. Adjust camber and caster to specifications by rotating bolt head. Tighten nuts to specification. See Steering and Suspension/Tires, Wheels and Alignment/Specifications/Mechanical. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Fuel Pressure > Diagnostic Connector - Fuel Pump > Component Information > Locations Diagnostic Connector - Fuel Pump: Locations For Fuel Pump Prime and Run Connector, See Computer and Control Systems, Data Link Connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Idle Speed > System Information > Specifications > Controlled Idle Speed Idle Speed: Specifications Controlled Idle Speed Under 8500 GVW Transmission Gear Idle Speed IAC Counts [1] OPEN/CLOSED Loop [2] Manual N 675 +/- 25 Varies CL Automatic D 550 +/- 25 Varies CL [1] On manual transmission vehicles the SCAN tool will display RDL in Neutral. Add 2 counts for engines with less than 500 miles. Add 2 counts for every 1000 ft. above sea level. [2] Let engine idle until proper fuel control status is reached (OPEN/CLOSED loop). Note: Engine should be at operating temperature 92°C to 104° (196°F to 222°F). Over 8500 GVW Transmission Gear Idle Speed IAC Counts [1] OPEN/CLOSED Loop [2] Manual N 675 +/- 25 Varies CL Automatic D 550 +/- 25 Varies CL [1] On manual transmission vehicles the SCAN tool will display RDL in Neutral. Add 2 counts for engines with less than 500 miles. Add 2 counts for every 1000 ft. above sea level. [2] Let engine idle until proper fuel control status is reached (OPEN/CLOSED loop). Note: Engine should be at operating temperature 92°C to 104° (196°F to 222°F). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Idle Speed > System Information > Adjustments > Controlled Idle Speed Idle Speed: Adjustments Controlled Idle Speed NOTE: There should be no Diagnostic Trouble Code (DTC)s displayed. The idle air control system has been checked. 1. Set the parking brake. 2. Block the drive wheels. 3. Connect a scan tool to the Data Link Connector (DLC) connector with the tool in the open mode. 4. Start the engine. 5. Bring the engine to the normal operating temperature. 6. Check for the correct state of the Transmission Range (TR) switch position on the scan tool. 7. Check the specifications for controlled idle speed and Idle Air Control (IAC) valve pintle position (counts). Refer to Idle Air Control Valve / Service and Repair. See: Powertrain Management/Computers and Control Systems/Idle Air Control (IAC) Valve/Service and Repair 8. If within specifications, the idle speed is being correctly controlled by the control module. 9. If not within specifications, refer to Driveability Symptoms. Refer to System Diagnosis for testing information. See: Powertrain Management/Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Cleaner Fresh Air Duct/Hose > Component Information > Specifications Air Cleaner Fresh Air Duct/Hose: Specifications Air intake duct screw ........................................................................................................................... ........................................................ 2 Nm (18 lb. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Cleaner Fresh Air Duct/Hose > Component Information > Specifications > Page 1948 Air Cleaner Fresh Air Duct/Hose: Service and Repair Air Intake Duct Retainer Bolt Air Intake Duct Removal Procedure 1. Remove the retainer. 2. Remove the screw. 3. Remove the air intake duct Installation Procedure 1. Install the air intake duct. 2. Install the screw. Tighten Tighten the screw 2 Nm (18 lb. in.). 3. Install the retainer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Customer Interest for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T - Shift/Driveability Concerns/MIL ON Air Filter Element: Customer Interest Engine, A/T - Shift/Driveability Concerns/MIL ON Bulletin No.: 04-07-30-013B Date: February 01, 2007 INFORMATION Subject: Automatic Transmission Shift, Engine Driveability Concerns or Service Engine Soon (SES) Light On as a Result of the Use of an Excessively/Over-Oiled Aftermarket, Reusable Air Filter Models: 2007 and Prior GM Cars and Light Duty Trucks 2007 and Prior Saturn Models 2003-2007 HUMMER H2 2006-2007 HUMMER H3 2005-2007 Saab 9-7X Supercede: This bulletin is being revised to add models and model years. Please discard Corporate Bulletin Number 04-07-30-013A (Section 07 - Transmission/Transaxle). The use of an excessively/over-oiled aftermarket, reusable air filter may result in: Service Engine Soon (SES) light on Transmission shift concerns, slipping and damaged clutch(es) or band(s) Engine driveability concerns, poor acceleration from a stop, limited engine RPM range The oil that is used on these air filter elements may be transferred onto the Mass Air Flow (MAF) sensor causing contamination of the sensor. As a result, the Grams per Second (GPS) signal from the MAF may be low and any or all of the concerns listed above may occur. When servicing a vehicle with any of these concerns, be sure to check for the presence of an aftermarket reusable, excessively/over-oiled air filter. The MAF, GPS reading should be compared to a like vehicle with an OEM air box and filter under the same driving conditions to verify the concern. The use of an aftermarket reusable air filter DOES NOT void the vehicle's warranty. If an aftermarket reusable air filter is used, technicians should inspect the MAF sensor element and the air induction hose for contamination of oil prior to making warranty repairs. Transmission or engine driveability concerns (related to the MAF sensor being contaminated with oil) that are the result of the use of an aftermarket reusable, excessively/over-oiled air filter are not considered to be warrantable repair items. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Customer Interest for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T - Shift/Driveability Concerns/MIL ON > Page 1957 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T - Shift/Driveability Concerns/MIL ON Air Filter Element: All Technical Service Bulletins Engine, A/T - Shift/Driveability Concerns/MIL ON Bulletin No.: 04-07-30-013B Date: February 01, 2007 INFORMATION Subject: Automatic Transmission Shift, Engine Driveability Concerns or Service Engine Soon (SES) Light On as a Result of the Use of an Excessively/Over-Oiled Aftermarket, Reusable Air Filter Models: 2007 and Prior GM Cars and Light Duty Trucks 2007 and Prior Saturn Models 2003-2007 HUMMER H2 2006-2007 HUMMER H3 2005-2007 Saab 9-7X Supercede: This bulletin is being revised to add models and model years. Please discard Corporate Bulletin Number 04-07-30-013A (Section 07 - Transmission/Transaxle). The use of an excessively/over-oiled aftermarket, reusable air filter may result in: Service Engine Soon (SES) light on Transmission shift concerns, slipping and damaged clutch(es) or band(s) Engine driveability concerns, poor acceleration from a stop, limited engine RPM range The oil that is used on these air filter elements may be transferred onto the Mass Air Flow (MAF) sensor causing contamination of the sensor. As a result, the Grams per Second (GPS) signal from the MAF may be low and any or all of the concerns listed above may occur. When servicing a vehicle with any of these concerns, be sure to check for the presence of an aftermarket reusable, excessively/over-oiled air filter. The MAF, GPS reading should be compared to a like vehicle with an OEM air box and filter under the same driving conditions to verify the concern. The use of an aftermarket reusable air filter DOES NOT void the vehicle's warranty. If an aftermarket reusable air filter is used, technicians should inspect the MAF sensor element and the air induction hose for contamination of oil prior to making warranty repairs. Transmission or engine driveability concerns (related to the MAF sensor being contaminated with oil) that are the result of the use of an aftermarket reusable, excessively/over-oiled air filter are not considered to be warrantable repair items. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T - Shift/Driveability Concerns/MIL ON > Page 1963 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Page 1964 Air Filter Element: Testing and Inspection The air cleaner restriction indicator is located on the intake duct between the air cleaner assembly and the Mass Air Flow (MAF) sensor. If the area inside of the clear section is green, no air filter service is required. If the area inside the clear section is orange and Change Air Filter appears, replace the air filter. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Page 1965 Air Filter Element: Service and Repair Air Cleaner Element Holddown REMOVAL PROCEDURE 1. Disconnect the hold down clips. 2. Remove the air cleaner cover. 3. Remove the filter. Hold the duct and remove the filter by pulling and twisting the filter away from the duct. 4. Clean the air cleaner housing. INSTALLATION PROCEDURE 1. Install the filter. - Install the new filter by pushing it all the way to the stops of the duct. - Install the duct and filter in the air cleaner housing. Make sure that the duct fits properly into the housing. 2. Install the air cleaner cover. 3. Connect the hold down clips. 4. Push the button on the top of the indicator to reset it to the green (Clean) filter zone. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Fuel Filter > Fuel Pressure Release > System Information > Service and Repair Fuel Pressure Release: Service and Repair TOOLS REQUIRED - J 34730 Fuel Pressure Gauge WARNING: Relieve the fuel system pressure before servicing fuel system components In order to reduce the risk of fire and personal Injury. After relieving the system pressure, a small amount of fuel may be released when servicing the fuel lines or connections. In order to reduce the chance of personal Injury, cover the regulator and the fuel line fittings with a shop towel before disconnecting. This will catch any fuel that may leak out. Place the towel In an approved container when the disconnection Is complete. 1. Disconnect the negative battery cable in order to avoid possible fuel discharge if an accidental attempt is made to start the engine. 2. Loosen the fuel filler cap in order to relieve the tank vapor pressure. 3. Connect the gauge J 34730-1A or the equivalent to the fuel pressure connection. 4. Wrap a shop towel around the fitting while connecting the gauge in order to avoid spillage. 5. Install the bleed hose into an approved container and open valve in order to bleed the system pressure. The fuel connections are now safe for servicing. 6. Drain any fuel remaining in gauge into an approved container. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Firing Order > Component Information > Specifications > Ignition Firing Order Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Ignition Timing > Number One Cylinder > Component Information > Locations > Number 1 Cylinder Location Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Ignition Timing > Timing Marks and Indicators > System Information > Locations > Crankshaft Rotation Timing Marks and Indicators: Locations Crankshaft Rotation Crankshaft Rotation (Typical Crankshaft Pulley) Crankshaft rotation is clockwise when viewed from in front of the crankshaft pulley as shown in the generic image. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Ignition Timing > Timing Marks and Indicators > System Information > Locations > Crankshaft Rotation > Page 1983 Timing Marks and Indicators: Locations Timing Marks The ignition timing is completely controlled by the Vehicle Control Module (VCM). No timing reference marks are provided. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications Spark Plug Wire: Specifications 0-15 inch cable .................................................................................................................................... .................................................. 3,000 - 10,000 ohms. 15-25 inch cable .................................................................................................................................. .................................................. 4,000 - 15,000 ohms. 25-35 inch cable .................................................................................................................................. .................................................. 6,000 - 20,000 ohms. Longer wires should measure about 5,000 to 10,000 ohms per foot. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 1987 Spark Plug Wire: Locations Spark Plug Wire Routing Right Side Spark Plug Wire Routing Left Side Wire routings must be kept intact during service and followed exactly when wires have been disconnected or when replacement of the wires is necessary. Failure to route the wires properly can lead to radio ignition noise and crossfiring of the plugs or shorting of the leads to ground Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 1988 Spark Plug Wire: Service Precautions Service Precautions 1. Twist boots one-half turn before removing. 2. When removing the boot, do not use pliers or other tools that could tear the boot. 3. Do not force anything between the wire and the boot, or through the silicone jacket of the wiring. 4. Do not pull on the wires to remove the boot. Pull on the boot or use a tool designed for this purpose. 5. Special care should be used when installing spark plug boots to ensure the metal terminal within the boot is fully seated on the spark plug terminal and the boot has not moved on the wire. NOTE: If boot to wire movement has occurred, the boot will give a false visual impression of being fully seated. Make sure that boots have been properly assembled by pushing sideways on the in stalled boots. Failure to properly seat the terminal onto the spark plug will lead to wire core erosion and result in an engine misfire or crossfire condition, and possible internal damage to the engine. ^ If they have been correctly installed, a stiff boot with only slight looseness will be noted. If the terminal has not been properly seated on the spark plug, only the resistance of the boot will be felt when pushing sideways. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 1989 Spark Plug Wire: Testing and Inspection VISUAL INSPECTION 1. Inspect the routing of the wires. Improper routing can cause crossfiring. 2. Inspect each wire for any signs of cracks or splits in the wire. 3. Inspect each boot for signs of tears, piercing, arc through, or carbon tracking. If the boot needs to be replaced, twist it a half-turn in either direction to break the seal before pulling on the boot to remove the wire. SPARK PLUG WIRE RESISTANCE TEST 1. Disconnect both ends of each wire. Make sure the wire terminals are clean. 2. Set ohmmeter on the high scale and connect it to each end of the wire being tested. Twist the wire gently while watching ohmmeter. 3. If ohmmeter reads above 30,000 ohms (no matter how long the wire is), or fluctuates from infinity any value, replace the wire. 4. If the resistance of any wire is not within the following ranges, replace the wire being tested. - 0 to 381 mm (0 to 15 in.) wire - 3,000 to 10,000 ohms. - 381 mm to 635 mm (15 in. to 25 in.) wire - 4,000 to 15,000 ohms. - 635 mm to 889 mm (25 in. to 35 in.) wire - 6,000 to 20,000 ohms. - Longer wire - should measure about 5,000 to 10,000 ohms per foot. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 1990 Spark Plug Wire: Service and Repair Spark Plug Wire Routing Right Side Spark Plug Wire Routing Left Side SERVICE CAUTIONS 1. Twist boots one-half turn before removing. 2. When removing the boot, do not use pliers or other tools that could tear the boot. 3. Do not force anything between the wire and the boot, or through the silicone jacket of the wiring. 4. Do not pull on the wires to remove the boot. Pull on the boot or use a tool designed for this purpose. 5. Special care should be used when installing spark plug boots to ensure the metal terminal within the boot is fully seated on the spark plug terminal and the boot has not moved on the wire. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 1991 WARNING: If boot to wire movement has occurred, the boot will give a false visual impression of being seated. Make sure that boots have been properly assembled by pushing sideways on the installed boots. Failure to properly seat the terminal onto the spark plug will lead to wire core erosion and result in an engine misfire or crossfire condition, and possible internal damage to the engine. ^ If they have been correctly installed, a stiff boot with only slight looseness will be noted. If the terminal has not been properly seated on the spark plug, only the resistance of the boot will be felt when pushing sideways. SPARK PLUG WIRE REPLACEMENT Spark plug wire routings must be kept intact during service and followed exactly when spark plug wires have been disconnected or when replacement of the spark plug wires is necessary. Failure to route the spark plug wires properly can lead to radio noise and crossfiring of the spark plugs, or shorting of the leads to ground. The correct routing is shown in the images. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Ignition System - Distributor Is Now Repairable Distributor: Technical Service Bulletins Ignition System - Distributor Is Now Repairable CHEVROLET 71-65-40 Issued: 05/01/97 SMU - SECTION 6E - REVISED ENHANCED IGNITION SYSTEM DESCRIPTION AND OPERATION SUBJECT: SERVICE MANUAL UPDATE - SECTION 6E - ENGINE CONTROLS REVISED ENHANCED IGNITION SYSTEM DESCRIPTION AND OPERATION MODELS: 1995-97 CHEVROLET AND GMC S/T, M/L, C/K, GMT600, P MODELS 1996-97 OLDSMOBILE BRAVADA WITH 4.3L, 5.0L, 5.7L, 7.4L ENGINE (VINS W, M, R, J - RPOS L35, L30, L31, L29) THIS BULLETIN IS BEING ISSUED TO INFORM TECHNICIANS OF A REVISION TO THE ENHANCED IGNITION SYSTEM DESCRIPTION AND OPERATION. THE DISTRIBUTOR IS NOW REPAIRABLE. TECHNICIANS WILL BE REFERRED TO DISTRIBUTOR OVERHAUL IN ENGINE ELECTRICAL FOR PROPER REPAIR AND REPLACEMENT OF ALL COMPONENTS. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Ignition System - Distributor Is Now Repairable > Page 1996 Distributor: Technical Service Bulletins Ignition - Distributor Service Kits Now Available File In Section: 6 - Engine Bulletin No.: 77-64-04 Date: April, 1997 SERVICE MANUAL UPDATE Subject: Distributor Service Kits Models: 1995 Chevrolet and GMC S/T Utility Models with 4.3L OBDII Engines ONLY (VIN W - RPO L35) 1996 Chevrolet and GMC C/K, M/L, S/T; P, G 1996 Oldsmobile Bravada 1997 Chevrolet and GMC C/K, M/L, S/T; P, G 1997 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L, 7.4L Engines (VINs W, X, M, R, J - RPOs L35, LF6, L3O, L31, L29) Service kits are now available to field service Distributor Assemblies. Important: Fastening screws have pre-applied thread locking adhesive and should be discarded after removal. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Ignition System - Distributor Is Now Repairable > Page 1997 1995 4.3L L35 OBDII Distributor Assemblies are now serviced with 1996 Distributor Assemblies (P/N 1104050). Installation instructions are included with each replacement assembly and must be followed. The following Service Kits are now available: Important: Removed fasteners are not to be re-used. Always use the new fasteners supplied in each kit. Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Ignition System - Distributor Is Now Repairable > Page 1998 Warranty Information For Vehicles repaired under warranty use the table shown. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Page 1999 Distributor: Specifications Distributor clamp and bolt .................................................................................................................... .................................................. 27 N.m (20 lbs. ft.) Distributor cap screws ........................................ ....................................................................................................................... 4.5-5.0 N.m (40-45 lbs. in.) Distributor rotor .................................................................................................................................... ................................................... 2 N.m (20 lbs. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Page 2000 Distributor: Locations Top of Engine, at rear, near Bulkhead Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Page 2001 Distributor: Application and ID The part number is pin stamped into the plastic base (directly below the high tension terminals and next to the three pin camshaft sensor connection.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Description and Operation > Distributor Operation Distributor: Description and Operation Distributor Operation DISTRIBUTORS Distributor This ignition system includes the distributor, hall effect switch, ignition coil, secondary wires, spark plugs, knock sensor and crankshaft position sensor. The ignition system is controlled by the vehicle control module (VCM). The VCM monitors information from various engine sensors, computes the desired spark timing and controls the dwell and firing of the ignition coil via an ignition control line to the coil driver. The distributor connects the ignition coil and spark plugs through secondary wires. The rotor directs the spark to the appropriate cylinder. The distributor has a hall effect switch that connects to the VCM through the primary engine harness and provides cylinder identification information. Identification The part number is pin stamped into the plastic base (directly below the high tension terminals and next to the three pin camshaft sensor connection.) Ignition Coil The coil driver controls the current flow in the primary winding of the ignition coil when signaled by the VCM. The interconnects are made by the primary engine harness. The ignition coil can generate up to 35,000 volts and connects to the distributor through a secondary wire. Secondary Wires The secondary wires carry voltage between the ignition coil, distributor, and spark plugs. The secondary wire connections form a tight seal that prevents voltage arching. Hall Effect Switch The hall effect switch connects to the VCM through the primary engine harness and provides cylinder identification information. The hall effect switch is located under the distributor cap. Crankshaft Position Sensor The crankshaft position sensor connects to the VCM through the primary engine harness and provides crank- shaft reference information to the VCM for spark and fuel delivery. The crankshaft position sensor is located in the front cover behind the crankshaft balancer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Description and Operation > Distributor Operation > Page 2004 Distributor: Description and Operation General Description Distributor The distributor is actually an assembly that contains the Camshaft Position (CMP) sensor, cap, rotor and shaft. The distributor is splined by a helical gear to the camshaft and provides spark to each spark plug wire. when servicing the distributor, it is critical to ensure proper cap sealing to the distributor body and correct installation to the camshaft. If the distributor is installed a tooth off in relation to the camshaft, a Diagnostic Trouble Code (DTC) will set. The distributor is not repairable and must be replaced as an assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Description and Operation > Page 2005 Distributor: Testing and Inspection NOTICE: Discoloration of the cap and some whitish build up around the cap terminals is normal. Yellowing of the rotor cap, darkening and some carbon build-up under the rotor segment is normal. Replacement of the cap and rotor is not necessary unless there is a driveablity concern. Inspect 1. Cap for cracks, tiny holes or carbon tracks between cap terminal traces. Carbon tracks can be diagnosed by using an ohmmeter. With the cap removed, place one base ohmmeter lead on a cap terminal. Use the other lead to probe all other terminals and the center carbon ball. Move the base lead to the next terminal and probe all other leads. Continue until all secondary terminals have been tested. If there are any non-infinite readings, replace the cap. 2. Cap for excessive build up of corrosion on the terminals. Scrape them clean or replace the cap. Some build up is normal. 3. Rotor segment. Replace the rotor if there is excessive wear on the rotor segment or the plastic under the segment or staked post is melted. Some looseness of the rotor segment is normal and does not cause performance problems. 4. Shaft for shaft-to-bushing looseness. Insert the shaft in the housing. If the shaft wobbles, replace the housing assembly. 5. Housing for cracks or damage. ^ Refer to Computers and Control Systems for ignition system diagnosis. See: Powertrain Management/Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment Distributor: Adjustments Camshaft Retard Offset Adjustment Description TEST PROCEDURE The ignition timing cannot be adjusted. The distributor may need adjusting to prevent crossfire. To insure proper alignment of the distributor, perform the following: 1. With the ignition OFF, install a scan tool to the DLC. 2. Start the engine and bring to normal operating temperature. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM. 3. Increase engine speed to 1000 RPM. 4. Monitor the Cam Retard Offset. 5. If the Cam Retard indicates a value of 0° +/-2°, the distributor is properly adjusted. 6. If the Cam Retard does not indicate 0° +/-2°, the distributor must be adjusted. ADJUSTING PROCEDURE 1. With the engine OFF, slightly loosen the distributor hold down bolt. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM. 2. Start the engine and raise engine speed to 1000 RPM. 3. Using a scan tool monitor Cam Retard Offset. 4. Rotate the distributor as follows: 4.1. To compensate for a negative reading, rotate the distributor in the counterclockwise direction. 4.2. To compensate for a positive reading, rotate the distributor in the clockwise direction. 5. Repeat step 4 until 0° +/-2°, is obtained. 6. Turn the ignition OFF. 7. Tighten the distributor hold-down bolt to 3 Nm (25 lb. ft.). 8. Start the engine, raise engine speed to 1000 RPM and recheck Camshaft Retard Offset. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 2008 Distributor: Adjustments Timing Adjustment NOTICE: The distributor is located in a fixed, non-adjustable position. No attempt should be made to adjust the engine base timing by rotating the distributor. Attempting to do so may result in engine cross-fire and mis-fire conditions. The distributor ignition system has no provision for timing adjustment. The base timing is preset when the engine is manufactured and no adjustment is possible. NOTICE: If the distributor is removed from the engine, It can be re-installed using "procedure A" as long as the crankshaft has not rotated from its Initial position. if the intake manifold, cylinder head, crankshaft, camshaft, timing gear or complete engine was removed or replaced, "procedure B" must be followed to correctly install the distributor. A Diagnostic Trouble Code (DTC) code may also indicate an Incorrectly installed distributor and engine or distributor damage may occur. Procedure B must then be used. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 2009 Distributor: Adjustments Procedure A Distributor Installation and Removal Procedure A Remove or Disconnect ^ Make sure the ignition switch is "OFF." 1. Spark plug and coil leads from the distributor cap. 2. Three wire hail effect switch plug from the base of the distributor. 3. Two screws holding the distributor cap to the housing. 4. Distributor cap. A. Use a grease pencil to note the position of the rotor segment in relation to the distributor housing. Identify the mark with a 1. B. The distributor housing and intake manifold should also be marked with a grease pencil for proper alignment when reinstalling. 5. Mounting clamp hold down bolt. 6. Distributor. ^ As the distributor is being removed from the engine, you will notice the rotor move in a counter-clockwise direction, 42°. This will appear as slightly more than one clock position. Noting the position of the rotor segment, by placing a second mark on the base of the distributor, will aid in achieving proper rotor alignment during distributor installation. Be sure to identify the second mark on the base with the number 2. Install or Connect Distributor Alignment Indicator A. If the original distributor is to be replaced, rather than repaired, remove the new distributor cap. Using a grease pencil, place two marks on the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 2010 new distributor housing in the same location as the two marks on the original housing. B. When installing the distributor, align the rotor segment with the number 2 mark on the base of the distributor. Guide the distributor into place, making sure the grease pencil marks on the distributor housing and the intake manifold are in line. As the the distributor is being installed, you will notice the rotor will move in a clockwise direction, 42°. ONCE THE DISTRIBUT0R IS COMPLETELY SEATED, the rotor segment should be aligned with the number 1 mark on the base. If the rotor segment is not aligned with the number 1 mark, the gear teeth of the distributor and camshaft have meshed one or more teeth out of time. To correct this condition, remove the distributor and re-install it following the procedure at step B. 1. Distributor cap and mounting screws. Do not overtighten the screws as the boss may strip. 2. Distributor mounting clamp and tighten to proper torque. Tighten ^ Distributor clamp and bolt to 27 Nm (20 lbs. ft.) ^ Distributor cap screws to 4.5-5.0 Nm (40-45 lbs. in.) 3. Three wire hall effect switch connector to base of the distributor. 4. Spark plug and coil leads to the distributor cap. ^ If a check engine light is illuminated after installing the distributor and a DTC P1345 is found, the distributor has been installed incorrectly. You now must refer to procedure; B or proper distributor installation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 2011 Distributor: Adjustments Procedure B Distributor Installation and Removal Procedure B Remove or Disconnect ^ Make sure the ignition switch is "OFF." ^ Bring the engine up to Top Dead Center (TDC) of cylinder number 1. Make sure it is on the compression stroke. A. Remove the distributor cap screws and cap to expose the rotor. Rotor Location B. Align the pre-drilled indent hole in the distributor driven gear with the white painted alignment line on the lower portion of the shaft housing. The rotor segment should point to the cap hold area as shown in the illustration. C. Using a long screw driver, align the oil pump drive shaft in the engine in the mating drive tab in the distributor. D. Guide the distributor into place, making sure the the spark plug towers are perpendicular to the center line of the engine. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 2012 Installed Rotor Position E. ONCE The DISTRIBUTOR IS FULLY SEATED, the rotor segment should be aligned with the pointer cast into the distributor base. This pointer will have a "8" cast into it, indicating the distributor is to be used in a 8 cylinder engine. if the rotor segment does not come within a few degrees of the pointer, the gear mesh between the distributor and camshaft may be off a tooth or more. If this is the case, repeat the procedure again to achieve proper alignment. Install or Connect 1. Cap and mounting screws. Do not overtighten as the boss may strip. 2. Distributor mounting clamp and tighten to proper torque. Tighten ^ Distributor clamp and bolt to 27 Nm (20 lbs. ft.) ^ Distributor cap screws to 4.5-5.0 Nm (40-45 lbs. in.) 3. Three wire hall effect switch plug to base of distributor. 4. Spark plug and coil leads to the distributor cap. ^ If a check engine light is illuminated after installing the distributor and a DTC P1345 is found, the distributor has been installed incorrectly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation Distributor: Service and Repair Distributor Removal & Installation Distributor Removal 1. Remove the ignition coil wire harness from the ignition coil and distributor cap. 2. Remove two screws holding the distributor cap to the housing. 3. Distributor cap. 4. Remove the distributor clamp bolt. 5. Remove the distributor and the distributor clamp. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2015 6. Remove the distributor gasket and discard. Distributor Installation 1. Bring cylinder number one piston to Top Dead Center (TDC) of compression stroke. 2. Install the distributor cap screws. 3. Install the distributor cap. 4. Install a NEW distributor gasket onto the distributor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2016 5. Align the indent hole on the driven gear with the paint mark on the distributor housing. 5. Ensure that the distributor rotor segment points to the cap hold area. 7. Align the slotted tang in the oil pump driveshaft with the distributor driveshaft. Rotate the oil pump driveshaft with a screwdriver if necessary. 8. Align the flat (1) in the distributor housing toward the front of the engine. 9. Install the distributor and distributor clamp. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2017 10. Once the distributor is fully seated, align the distributor rotor segment with the number 8 pointer that is cast into the distributor base. 11. If the distributor rotor segment does not come within a few degrees of the number 8 pointer, the gear mesh between the distributor and camshaft may be off a tooth or more. Repeat the procedure in order to achieve proper alignment. Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems. 12. Install the distributor clamp bolt. Tighten the distributor clamp bolt to 25 Nm (18 ft. lbs.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2018 13. Install the distributor cap onto the distributor. 14. Install the NEW distributor cap screws. Do not overtighten the NEW distributor cap screws. Tighten the distributor cap screws to 2.4 Nm (21 in. lbs.). 15. Install the ignition coil wire harness. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2019 Distributor: Service and Repair Distributor Disassembly and Assembly Distributor Components NOTICE: The distributor driven gear can be installed in two positions. Make sure when installing the gear that the dimple found below the roll pin hole in the gear is on the same side as the rotor segment. The dimple will not align directly with the rotor segment if not, the gear is Installed 180° off and a no start condition may occur. Premature wear and damage may result. Remove or Disconnect 1. Two screws holding the cap to the housing. 2. Cap from the housing. 3. Two screws from the rotor. Vane Wheel In Distributor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2020 4. Rotor. ^ Note which locating holes (B) the rotor was removed from. 5. Two screws holding the hall effect switch. 6. Hall effect switch. ^ The square cut hole (C) in the vane wheel must be aligned with the hall effect switch in order to remove the switch. 7. Roil pin from the shaft. A. Note the dimple located below the roil pin hole on the one side of the gear. The dimple will be used to properly orient the gear on the shaft during assembly. 8. Driven gear, washer, and tang washer. 9. Shaft. ^ If the shaft can't be removed from the distributor housing due to varnish buildup, use a cloth dampened with varnish remover to clean the shaft. NOTICE: Failure to keep cleaning agents away from the hall effect switch may result in premature failure. Install or Connect 1. Hall effect switch. 2. Two screws holding the hall effect switch. Do not overtighten as the base may strip. 3. Shaft. 4. Tang washer, washer, and driven gear. ^ When the driven gear is properly installed the dimple located below the roll pin hole, in the driven gear, will be on the same side as the rotor segment when the rotor is installed in the distributor. If the driven gear is installed incorrectly, the dimple will be on the opposite of the rotor segment. 5. Roll pin. 6. Rotor. ^ "A" shows the mounting holes. "B" shows the locating holes. 7. Two screws holding rotor. Tighten ^ Screws to 2.0 Nm (20 lbs. In.) Installation of the distributor into the engine will require the distributor cap off of the assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2021 Distributor: Service and Repair Distributor Alignment/Camshaft Retard Offset Adjustment Description TEST PROCEDURE The ignition timing cannot be adjusted. The distributor may need adjusting to prevent crossfire. To insure proper alignment of the distributor, perform the following: 1. With the ignition OFF, install a scan tool to the DLC. 2. Start the engine and bring to normal operating temperature. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM. 3. Increase engine speed to 1000 RPM. 4. Monitor the Cam Retard Offset. 5. If the Cam Retard indicates a value of 0° +/-2°, the distributor is properly adjusted. 6. If the Cam Retard does not indicate 0° +/-2°, the distributor must be adjusted. ADJUSTING PROCEDURE 1. With the engine OFF, slightly loosen the distributor hold down bolt. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM. 2. Start the engine and raise engine speed to 1000 RPM. 3. Using a scan tool monitor Cam Retard Offset. 4. Rotate the distributor as follows: 4.1. To compensate for a negative reading, rotate the distributor in the counterclockwise direction. 4.2. To compensate for a positive reading, rotate the distributor in the clockwise direction. 5. Repeat step 4 until 0° +/-2°, is obtained. 6. Turn the ignition OFF. 7. Tighten the distributor hold-down bolt to 3 Nm (25 lb. ft.). 8. Start the engine, raise engine speed to 1000 RPM and recheck Camshaft Retard Offset. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2022 Distributor: Service and Repair Distributor Assembly Replacement Removal Procedure NOTICE: If the distributor is removed from the engine, It can be re-installed using "procedure A" as long as the crankshaft has not rotated from the original position. If the intake manifold, cylinder head, crankshaft, camshaft, timing gear or complete engine was removed or replaced, "Procedure B" must be followed in order to correctly install the distributor. A DTC code may also indicate an incorrectly installed distributor and engine or distributor damage may occur. Procedure B must then be used. 1. Turn OFF the ignition switch. 2. Remove the spark plug and the ignition coil wires from distributor cap. 3. Remove the three-wire hall effect switch connector from the base of the distributor. 4. Remove the two screws holding the distributor cap to the housing. 5. Remove the distributor cap. A. Use a grease pencil in order to note the position of the rotor in relation to the distributor housing. Identify the mark with the number 1. B. Mark the distributor housing and the intake manifold with a grease pencil for proper alignment when reinstalling. 6. Remove the mounting clamp hold down bolt. 7. Remove the distributor. 8. As the distributor is being removed from the engine, you will notice the rotor move in a counter-clockwise direction about 42 degrees. This will appear as slightly more than one clock position. Noting the position of the rotor segment by placing a second mark on the base of the distributor will aid in achieving proper rotor alignment during the distributor installation. Identify the second mark on the distributor housing at number 2. Installation Procedure A 1. Remove the new distributor cap. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2023 2. If installing a new distributor assembly, place two marks on the new distributor housing in the same location as the two marks on the original housing. 3. When installing the distributor, align the rotor with mark made at location 2.. 4. Guide the distributor into place, making sure the mounting hole in the distributor hold down base is aligned over the mounting hole in the intake manifold. 5. As the distributor is being installed, you will notice the rotor will move in a clockwise direction about 42 degrees. 6. Once the distributor is completely seated, the rotor segment should be aligned with mark on the base in location number 1. If the rotor segment is not aligned with the number 1 mark, the gear teeth of the distributor and the camshaft have meshed one or more teeth out of time. In order to correct the condition, remove the distributor and reinstall it. 7. Install the cap and the mounting screws. Do not overtighten as they may strip. Tighten Tighten the distributor cap screws to 5 Nm (45 lb in). NOTICE: Use the correct fasteners in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces inless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems. 8. Install the distributor clamp bolt. Tighten Tighten the distributor clamp bolt to to 27 Nm (20 lb ft). NOTICE: Use the correct fasteners in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2024 paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces inless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems. 9. Install the three wire hall effect switch connector to the base of the distributor. 10. Install the spark plug and the ignition coil wires to the distributor cap. Important: If a check engine light is illuminated after installing the distributor and a DTC P1345 is found, the distributor has been installed incorrectly. Refer to procedure B for proper distributor installation. Installation Procedure B 1. Rotate the number 1 cylinder up to Top Dead Center (TDC) of the compression stroke. 2. Remove the distributor cap screws and the distributor cap to expose the rotor. 3. Align the pre-drilled indent hole in the distributor driven gear with the white alignment line on the lower portion of the shaft housing. 4. The rotor should point to the cap hold down mount nearest the flat side of the housing. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2025 5. Using a long screw driver, align the oil pump drive shaft to the drive tab of the distributor. 6. Guide the distributor in place, ensuring that the spark plug towers are perpendicular to the centerline of engine. 7. Once the distributor is fully seated, the rotor segment should be aligned with the pointer cast into the distributor base. This pointer will have a 6 or 8 cast into it, indicating that the distributor is to be used on a 6 or 8 cylinder engine. If the rotor segment does not come within a few degrees of the pointer, the gear mesh between the distributor and the camshaft may be off a tooth or more. If this is the case, repeat the procedure again in order to achieve proper alignment. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Spark Plug > Component Information > Specifications Spark Plug: Specifications Spark plug type .................................................................................................................................... ....................................................................... 41-932 Spark plug gap ................................................ ....................................................................................................................................................... 0.060 inch Spark plugs (new cylinder head) ........................................................................................ ........................................................................ 30 Nm (22 lb. ft.) Spark plugs (used cylinder head) ... ............................................................................................................................................................ 20 Nm (14 lb. ft.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Spark Plug > Component Information > Specifications > Page 2029 Spark Plug: Description and Operation DESCRIPTION Resistor-type. tapered-seat spark plugs are used. No gasket is used on these plugs. These spark plugs are a High Efficiency (HE) spark plug that has a fine wire electrode, nickel plated shell and a platinum pad across from the electrode. These features give the HE spark plug long life durability. Refer to Specifications or to the Vehicle Emissions Control Information label on the fan shroud for correct gap information. See: Specifications CONSTRUCTION If the spark plug shell hex is not fully engaged in the spark plug socket wrench, the socket may cock at an angle and cause insulator cracking and/or breakage during plug installation or removal. OPERATION Normal or average service is assumed to be a mixture of idling, low speed, and high speed operation with some of each making up the daily total driving. Occasional or intermittent high-speed driving is essential to good spark plug performance. It provides increased and sustained combustion heat that burns away any excess deposits of carbon or oxide that may have accumulated from frequent idling or continual stop-and-go or slow-speed driving. Spark plugs are protected by an insulating boot made of special heat-resistant material that covers the spark plug terminal and extends downward over a portion of the plug insulation These boots prevent flash-over with resultant missing of the engine, even though a film is allowed to accumulate on the exposed portion of plug porcelains. Do not mistake corona discharge for flash-over or a shorted insulator. Corona discharge is a steady blue light appearing around the insulator. just above the shell crimp It is the visible evidence of a high-tension field, and has no effect on ignition performance. Usually it can be detected only in darkness. This discharge may repel dust particles, leaving a clear ring on the insulator just above the shell. This ring is sometimes mistakenly regarded as evidence that combustion gases have blown out between the shell and insulator. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Spark Plug > Component Information > Specifications > Page 2030 Spark Plug Diagnosis Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Spark Plug > Component Information > Specifications > Page 2031 Spark Plug: Service and Repair CAUTION ^ Allow the engine to cool before removing the spark plugs. Attempting to remove the plugs from a hot engine may cause the plug to seize, causing damage to the cylinder head threads. ^ Clean the spark plug recess area before removing the plug. Failure to do so can result in engine damage due to dirt or foreign material entering the cylinder head or contamination of the cylinder head threads. Contaminated threads may prevent proper seating of a new plug. ^ Do not install plugs that are either hotter or colder than the heat range specified. Using plugs of the wrong heat range can severely damage the engine. REMOVE OR DISCONNECT ^ Make sure the ignition switch is OFF. CAUTION: Twist the spark plug boot one-half turn to release it. Pull on the spark plug boot only. Do not pull on the wire or the spark plug lead may be damaged. 1. Spark plug wires and boots. ^ Label the plug wires. CAUTION: Be sure to use J 39358 or equivalent spark plug socket Failure to do so could cause cracking of the insulator and arcing inside the plug, resulting in engine misfire. 2. Spark plugs using J 39358 or equivalent. Inspect ^ Each spark plug for wear and gap. ^ Spark plugs should be gapped to 0.060 inch. INSTALL OR CONNECT CAUTION: Make sure each sparkplug threads smoothly into the cylinder head and is fully seated. Cross-threading or falling to fully seat spark plugs can cause overheating of the plugs, exhaust blow-by, or thread damage. 1. Spark plugs. Tighten ^ Spark plugs to 30 Nm (22 lb. ft.) in a new cylinder head and 20 Nm (14 lb. ft.) in a used head. 2. Wire and boot assemblies. Refer to Spark Plug Wiring and Boots for precautions. See: Spark Plug Wire/Service Precautions Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Compression Check > System Information > Specifications Compression Check: Specifications Minimum, 698 kPa (100 psi) @ 200 rpm. The lowest cylinder reading should not be less than 80% of the highest. Perform compression test with engine at normal operating temperature, spark plugs removed and throttle wide open. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Valve Clearance > System Information > Specifications > Valve Clearance Specifications Valve Clearance: Specifications Valve Clearance Specifications One turn down from zero lash. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Valve Clearance > System Information > Specifications > Valve Clearance Specifications > Page 2039 Valve Clearance: Specifications Valve Arrangement FRONT TO REAR 5.7L/V8-350 ......................................................................................................................................... ........................................................... E-I-I-E-E-I-I-E Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Valve Clearance > System Information > Specifications > Page 2040 Valve Clearance: Adjustments 1. Remove rocker arm cover. 2. Crank engine until the mark on the vibration damper aligns with the "0 mark on the timing tab and the engine is in the number one firing position. This may be determined by placing fingers on valves of number one cylinder as the mark on the damper comes near the " 0 mark on the timing tab. If the rocker arms are not moving, the engine is in the number one firing position. If the rocker arms move as the marks comes up to the timing tab, the engine is in the number six firing position and should be turned over one more time to reach the number one firing position. 3. With the engine in this position, exhaust valves 1, 3, 4 and 8 and intake valves 1, 2, 5 and 7 can be adjusted. Even numbered cylinders are in the right bank, odd numbered cylinders are in the left bank when viewed from the rear of the engine. 4. Back off the adjusting nut until lash is felt at the pushrod, then turn in the adjusting nut until all lash is removed. This can be determined by rotating the pushrod while turning the adjusting nut. When play has been removed, turn the adjusting nut in one full additional turn. 5. Crank engine one complete revolution until the timing tab " 0 mark and vibration damper mark are aligned. This is the number six firing position. 6. With the engine in this position, exhaust valves 2, 5, 6 and 7 and intake valves 3, 4, 6 and 8 can be adjusted. 7. With valves properly adjusted, install rocker arm cover. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Drive Belt > Component Information > Technical Service Bulletins > Customer Interest: > 77-60-02 > Jun > 98 > Engine - Drive Belt Noise, P/S Pump Pulley Misaligned Drive Belt: Customer Interest Engine - Drive Belt Noise, P/S Pump Pulley Misaligned File In Section: 6 - Engine Bulletin No.: 77-60-02 Date: June, 1998 Subject: Accessory Drive Belt Noise Due to Power Steering Pump Pulley Misalignment (Properly Align Pulley) Models: 1996-98 Chevrolet and GMC C/K, M/L, S/T; G, P Models 1996-98 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, X, M, R, J, N - RPOs L35, LF6, L3O, L31, L29, L19) Condition Some owners may comment on accessory drive noise. Cause The power steering pump pulley may be misaligned with the end of the pump shaft. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Drive Belt > Component Information > Technical Service Bulletins > Customer Interest: > 77-60-02 > Jun > 98 > Engine - Drive Belt Noise, P/S Pump Pulley Misaligned > Page 2049 In addition to the normal service for the above condition, it is critical that the pulley is flush with the end of the power steering pump shaft. If it is not, reference the appropriate service manual for proper service instructions. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time E836O Use published labor operation time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Drive Belt > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Drive Belt: > 08-06-01-008A > Jul > 09 > Engine - Drive Belt Misalignment Diagnostics Drive Belt: All Technical Service Bulletins Engine - Drive Belt Misalignment Diagnostics INFORMATION Bulletin No.: 08-06-01-008A Date: July 27, 2009 Subject: Diagnosing Accessory Drive Belt / Serpentine Belt Noise and Availability and Use of Kent-Moore EN-49228 Laser Alignment Tool - Drive Belt Models: 2010 and Prior GM Passenger Cars and Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 Vehicles 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add a model year and update the Tool Information. Please discard Corporate Bulletin Number 08-06-01-008 (Section 06 - Engine). Background Several aftermarket companies offer laser alignment tools for accessory drive systems that can be very helpful in eliminating drive belt noise as a result of misaligned pulleys. Typically pricing ranges from $160 - $200. EN-49228 Laser Alignment Tool - Drive Belt The GM Tool program has now made available a competitive, simple to use and time-saving laser tool to assist in achieving precise alignment of the drive belt pulleys. This optional tool removes the guesswork from proper pulley alignment and may serve to reduce comebacks from: - Drive Belt Noise - Accelerated Drive Belt Wear - Drive Belt Slippage Instructions The instructions below are specific only to the truck Gen IV V-8 family of engines. These instructions are only for illustrative purposes to show how the tool may be used. Universal instructions are included in the box with the Laser Alignment Tool - Drive Belt. Caution - Do not look directly into the beam projected from the laser. - Use caution when shining the laser on highly polished or reflective surfaces. Laser safety glasses help reduce laser beam glare in many circumstances. - Always use laser safety glasses when using the laser. Laser safety glasses are not designed to protect eyes from direct laser exposure. 1. Observe and mark the serpentine belt orientation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Drive Belt > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Drive Belt: > 08-06-01-008A > Jul > 09 > Engine - Drive Belt Misalignment Diagnostics > Page 2055 2. Remove the serpentine belt from the accessory drive system. 3. Install the tool onto the power steering pulley. Position the legs of the tool into the outer grooves of the pulley, farthest from the front of the engine. 4. Install the retaining cord around the pulley and to the legs of the tool. 5. Put on the laser safety glasses provided with the tool. 6. Depress the switch on the rear of the tool to activate the light beam. 7. Rotate the power steering pulley as required to project the light beam onto the crankshaft balancer pulley grooves. 8. Inspect for proper power steering pulley alignment. - If the laser beam projects onto the second rib or raised area (1), the pulleys are aligned properly. - If the laser beam projects more than one-quarter rib 0.9 mm (0.035 in) mis-alignment, adjust the position of the power steering pulley as required. - Refer to SI for Power Steering Pulley Removal and Installation procedures. 9. Install the serpentine belt to the accessory drive system in the original orientation. 10. Operate the vehicle and verify that the belt noise concern is no longer present. Tool Information Please visit the GM service tool website for pricing information or to place your order for this tool. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Drive Belt > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Drive Belt: > 08-06-01-008A > Jul > 09 > Engine - Drive Belt Misalignment Diagnostics > Page 2056 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Drive Belt > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Drive Belt: > 04-06-01-013 > Apr > 04 > Engine - Serpentine Drive Belt Wear Information Drive Belt: All Technical Service Bulletins Engine - Serpentine Drive Belt Wear Information Bulletin No.: 04-06-01-013 Date: April 29, 2004 INFORMATION Subject: Information on Serpentine Belt Wear Models: 2004 and Prior Passenger Cars and Trucks 2003-2004 and Prior HUMMER H2 All current GM vehicles designed and manufactured in North America were assembled with serpentine belts that are made with an EPDM material and should last the life of the vehicle. It is extremely rare to observe any cracks in EPDM belts and it is not expected that they will require maintenance before 10 years or 240,000 km (150,000 mi) of use. Older style belts, which were manufactured with a chloroprene compound, may exhibit cracks depending on age. However, the onset of cracking typically signals that the belt is only about halfway through its usable life. A good rule of thumb for chloroprene-based belts is that if cracks are observed 3 mm (1/8 in) apart, ALL AROUND THE BELT, the belt may be reaching the end of its serviceable life and should be considered a candidate for changing. Small cracks spaced at greater intervals should not be considered as indicative that the belt needs changing. Any belt that exhibits chunking should be replaced. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Drive Belt > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Drive Belt: > 77-60-02 > Jun > 98 > Engine - Drive Belt Noise, P/S Pump Pulley Misaligned Drive Belt: All Technical Service Bulletins Engine - Drive Belt Noise, P/S Pump Pulley Misaligned File In Section: 6 - Engine Bulletin No.: 77-60-02 Date: June, 1998 Subject: Accessory Drive Belt Noise Due to Power Steering Pump Pulley Misalignment (Properly Align Pulley) Models: 1996-98 Chevrolet and GMC C/K, M/L, S/T; G, P Models 1996-98 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, X, M, R, J, N - RPOs L35, LF6, L3O, L31, L29, L19) Condition Some owners may comment on accessory drive noise. Cause The power steering pump pulley may be misaligned with the end of the pump shaft. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Drive Belt > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Drive Belt: > 77-60-02 > Jun > 98 > Engine - Drive Belt Noise, P/S Pump Pulley Misaligned > Page 2065 In addition to the normal service for the above condition, it is critical that the pulley is flush with the end of the power steering pump shaft. If it is not, reference the appropriate service manual for proper service instructions. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time E836O Use published labor operation time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Drive Belt > Component Information > Technical Service Bulletins > All Other Service Bulletins for Drive Belt: > 08-06-01-008A > Jul > 09 > Engine - Drive Belt Misalignment Diagnostics Drive Belt: All Technical Service Bulletins Engine - Drive Belt Misalignment Diagnostics INFORMATION Bulletin No.: 08-06-01-008A Date: July 27, 2009 Subject: Diagnosing Accessory Drive Belt / Serpentine Belt Noise and Availability and Use of Kent-Moore EN-49228 Laser Alignment Tool - Drive Belt Models: 2010 and Prior GM Passenger Cars and Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 Vehicles 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add a model year and update the Tool Information. Please discard Corporate Bulletin Number 08-06-01-008 (Section 06 - Engine). Background Several aftermarket companies offer laser alignment tools for accessory drive systems that can be very helpful in eliminating drive belt noise as a result of misaligned pulleys. Typically pricing ranges from $160 - $200. EN-49228 Laser Alignment Tool - Drive Belt The GM Tool program has now made available a competitive, simple to use and time-saving laser tool to assist in achieving precise alignment of the drive belt pulleys. This optional tool removes the guesswork from proper pulley alignment and may serve to reduce comebacks from: - Drive Belt Noise - Accelerated Drive Belt Wear - Drive Belt Slippage Instructions The instructions below are specific only to the truck Gen IV V-8 family of engines. These instructions are only for illustrative purposes to show how the tool may be used. Universal instructions are included in the box with the Laser Alignment Tool - Drive Belt. Caution - Do not look directly into the beam projected from the laser. - Use caution when shining the laser on highly polished or reflective surfaces. Laser safety glasses help reduce laser beam glare in many circumstances. - Always use laser safety glasses when using the laser. Laser safety glasses are not designed to protect eyes from direct laser exposure. 1. Observe and mark the serpentine belt orientation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Drive Belt > Component Information > Technical Service Bulletins > All Other Service Bulletins for Drive Belt: > 08-06-01-008A > Jul > 09 > Engine - Drive Belt Misalignment Diagnostics > Page 2071 2. Remove the serpentine belt from the accessory drive system. 3. Install the tool onto the power steering pulley. Position the legs of the tool into the outer grooves of the pulley, farthest from the front of the engine. 4. Install the retaining cord around the pulley and to the legs of the tool. 5. Put on the laser safety glasses provided with the tool. 6. Depress the switch on the rear of the tool to activate the light beam. 7. Rotate the power steering pulley as required to project the light beam onto the crankshaft balancer pulley grooves. 8. Inspect for proper power steering pulley alignment. - If the laser beam projects onto the second rib or raised area (1), the pulleys are aligned properly. - If the laser beam projects more than one-quarter rib 0.9 mm (0.035 in) mis-alignment, adjust the position of the power steering pulley as required. - Refer to SI for Power Steering Pulley Removal and Installation procedures. 9. Install the serpentine belt to the accessory drive system in the original orientation. 10. Operate the vehicle and verify that the belt noise concern is no longer present. Tool Information Please visit the GM service tool website for pricing information or to place your order for this tool. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Drive Belt > Component Information > Technical Service Bulletins > All Other Service Bulletins for Drive Belt: > 08-06-01-008A > Jul > 09 > Engine - Drive Belt Misalignment Diagnostics > Page 2072 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Drive Belt > Component Information > Technical Service Bulletins > All Other Service Bulletins for Drive Belt: > 04-06-01-013 > Apr > 04 > Engine - Serpentine Drive Belt Wear Information Drive Belt: All Technical Service Bulletins Engine - Serpentine Drive Belt Wear Information Bulletin No.: 04-06-01-013 Date: April 29, 2004 INFORMATION Subject: Information on Serpentine Belt Wear Models: 2004 and Prior Passenger Cars and Trucks 2003-2004 and Prior HUMMER H2 All current GM vehicles designed and manufactured in North America were assembled with serpentine belts that are made with an EPDM material and should last the life of the vehicle. It is extremely rare to observe any cracks in EPDM belts and it is not expected that they will require maintenance before 10 years or 240,000 km (150,000 mi) of use. Older style belts, which were manufactured with a chloroprene compound, may exhibit cracks depending on age. However, the onset of cracking typically signals that the belt is only about halfway through its usable life. A good rule of thumb for chloroprene-based belts is that if cracks are observed 3 mm (1/8 in) apart, ALL AROUND THE BELT, the belt may be reaching the end of its serviceable life and should be considered a candidate for changing. Small cracks spaced at greater intervals should not be considered as indicative that the belt needs changing. Any belt that exhibits chunking should be replaced. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Drive Belt > Component Information > Technical Service Bulletins > Page 2077 Drive Belt: Service and Repair REMOVE OR DISCONNECT 1. Release belt tension. ^ Use a suitable breaker bar in the square hole provided in the belt tensioner to rotate tensioner counterclockwise and release tension on all models. CAUTION: Do not rotate the tensioner except as noted above. Also, do not allow the tensioner to snap into the "free" position. Either of these conditions could damage the belt and/or tensioner. 2. Belt. INSTALL OR CONNECT NOTE: Install a multiple ribbed belt following the belt routings shown. The grooves in the belt must match the grooves in the pulleys. The tensioner is spring loaded. After removing the belt, the tensioner will return to the tension position. 1. Route belt over all of the pulleys except the belt tensioner. 2. Release belt tensioner. ^ Use a 1/2 inch breaker bar in the square hole provided in the belt tensioner to rotate tensioner counterclockwise and release tension on all models. 3. Belt over tensioner pulley. Slowly allow tensioner to move back into installed position. 4. Check the belt for correct "V" groove tracking into each pulley. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Filters > Air Cleaner Housing > Air Cleaner Fresh Air Duct/Hose > Component Information > Specifications Air Cleaner Fresh Air Duct/Hose: Specifications Air intake duct screw ........................................................................................................................... ........................................................ 2 Nm (18 lb. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Filters > Air Cleaner Housing > Air Cleaner Fresh Air Duct/Hose > Component Information > Specifications > Page 2083 Air Cleaner Fresh Air Duct/Hose: Service and Repair Air Intake Duct Retainer Bolt Air Intake Duct Removal Procedure 1. Remove the retainer. 2. Remove the screw. 3. Remove the air intake duct Installation Procedure 1. Install the air intake duct. 2. Install the screw. Tighten Tighten the screw 2 Nm (18 lb. in.). 3. Install the retainer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Filters > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Customer Interest for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T Shift/Driveability Concerns/MIL ON Air Filter Element: Customer Interest Engine, A/T - Shift/Driveability Concerns/MIL ON Bulletin No.: 04-07-30-013B Date: February 01, 2007 INFORMATION Subject: Automatic Transmission Shift, Engine Driveability Concerns or Service Engine Soon (SES) Light On as a Result of the Use of an Excessively/Over-Oiled Aftermarket, Reusable Air Filter Models: 2007 and Prior GM Cars and Light Duty Trucks 2007 and Prior Saturn Models 2003-2007 HUMMER H2 2006-2007 HUMMER H3 2005-2007 Saab 9-7X Supercede: This bulletin is being revised to add models and model years. Please discard Corporate Bulletin Number 04-07-30-013A (Section 07 - Transmission/Transaxle). The use of an excessively/over-oiled aftermarket, reusable air filter may result in: Service Engine Soon (SES) light on Transmission shift concerns, slipping and damaged clutch(es) or band(s) Engine driveability concerns, poor acceleration from a stop, limited engine RPM range The oil that is used on these air filter elements may be transferred onto the Mass Air Flow (MAF) sensor causing contamination of the sensor. As a result, the Grams per Second (GPS) signal from the MAF may be low and any or all of the concerns listed above may occur. When servicing a vehicle with any of these concerns, be sure to check for the presence of an aftermarket reusable, excessively/over-oiled air filter. The MAF, GPS reading should be compared to a like vehicle with an OEM air box and filter under the same driving conditions to verify the concern. The use of an aftermarket reusable air filter DOES NOT void the vehicle's warranty. If an aftermarket reusable air filter is used, technicians should inspect the MAF sensor element and the air induction hose for contamination of oil prior to making warranty repairs. Transmission or engine driveability concerns (related to the MAF sensor being contaminated with oil) that are the result of the use of an aftermarket reusable, excessively/over-oiled air filter are not considered to be warrantable repair items. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Filters > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Customer Interest for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T Shift/Driveability Concerns/MIL ON > Page 2092 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Filters > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T - Shift/Driveability Concerns/MIL ON Air Filter Element: All Technical Service Bulletins Engine, A/T - Shift/Driveability Concerns/MIL ON Bulletin No.: 04-07-30-013B Date: February 01, 2007 INFORMATION Subject: Automatic Transmission Shift, Engine Driveability Concerns or Service Engine Soon (SES) Light On as a Result of the Use of an Excessively/Over-Oiled Aftermarket, Reusable Air Filter Models: 2007 and Prior GM Cars and Light Duty Trucks 2007 and Prior Saturn Models 2003-2007 HUMMER H2 2006-2007 HUMMER H3 2005-2007 Saab 9-7X Supercede: This bulletin is being revised to add models and model years. Please discard Corporate Bulletin Number 04-07-30-013A (Section 07 - Transmission/Transaxle). The use of an excessively/over-oiled aftermarket, reusable air filter may result in: Service Engine Soon (SES) light on Transmission shift concerns, slipping and damaged clutch(es) or band(s) Engine driveability concerns, poor acceleration from a stop, limited engine RPM range The oil that is used on these air filter elements may be transferred onto the Mass Air Flow (MAF) sensor causing contamination of the sensor. As a result, the Grams per Second (GPS) signal from the MAF may be low and any or all of the concerns listed above may occur. When servicing a vehicle with any of these concerns, be sure to check for the presence of an aftermarket reusable, excessively/over-oiled air filter. The MAF, GPS reading should be compared to a like vehicle with an OEM air box and filter under the same driving conditions to verify the concern. The use of an aftermarket reusable air filter DOES NOT void the vehicle's warranty. If an aftermarket reusable air filter is used, technicians should inspect the MAF sensor element and the air induction hose for contamination of oil prior to making warranty repairs. Transmission or engine driveability concerns (related to the MAF sensor being contaminated with oil) that are the result of the use of an aftermarket reusable, excessively/over-oiled air filter are not considered to be warrantable repair items. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Filters > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T - Shift/Driveability Concerns/MIL ON > Page 2098 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Filters > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Page 2099 Air Filter Element: Testing and Inspection The air cleaner restriction indicator is located on the intake duct between the air cleaner assembly and the Mass Air Flow (MAF) sensor. If the area inside of the clear section is green, no air filter service is required. If the area inside the clear section is orange and Change Air Filter appears, replace the air filter. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Filters > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Page 2100 Air Filter Element: Service and Repair Air Cleaner Element Holddown REMOVAL PROCEDURE 1. Disconnect the hold down clips. 2. Remove the air cleaner cover. 3. Remove the filter. Hold the duct and remove the filter by pulling and twisting the filter away from the duct. 4. Clean the air cleaner housing. INSTALLATION PROCEDURE 1. Install the filter. - Install the new filter by pushing it all the way to the stops of the duct. - Install the duct and filter in the air cleaner housing. Make sure that the duct fits properly into the housing. 2. Install the air cleaner cover. 3. Connect the hold down clips. 4. Push the button on the top of the indicator to reset it to the green (Clean) filter zone. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Filters > Fuel Filter > Fuel Pressure Release > System Information > Service and Repair Fuel Pressure Release: Service and Repair TOOLS REQUIRED - J 34730 Fuel Pressure Gauge WARNING: Relieve the fuel system pressure before servicing fuel system components In order to reduce the risk of fire and personal Injury. After relieving the system pressure, a small amount of fuel may be released when servicing the fuel lines or connections. In order to reduce the chance of personal Injury, cover the regulator and the fuel line fittings with a shop towel before disconnecting. This will catch any fuel that may leak out. Place the towel In an approved container when the disconnection Is complete. 1. Disconnect the negative battery cable in order to avoid possible fuel discharge if an accidental attempt is made to start the engine. 2. Loosen the fuel filler cap in order to relieve the tank vapor pressure. 3. Connect the gauge J 34730-1A or the equivalent to the fuel pressure connection. 4. Wrap a shop towel around the fitting while connecting the gauge in order to avoid spillage. 5. Install the bleed hose into an approved container and open valve in order to bleed the system pressure. The fuel connections are now safe for servicing. 6. Drain any fuel remaining in gauge into an approved container. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Filters > Fuel Pump Pickup Filter > Component Information > Description and Operation Fuel Pump Pickup Filter: Description and Operation A woven plastic filter attaches to the lower end of the fuel pump in the fuel tank. The functions of the strainer are to filter contaminants and to wick fuel. The life of the fuel pump strainer is generally considered to be that of the fuel pump. The fuel pump strainer is self-cleaning and normally requires no maintenance. Fuel stoppage at this point indicates that the fuel tank contains an abnormal amount of sediment or water. In which case the fuel tank should have a thorough cleaning. Refer to Fuel System Cleaning. If the fuel strainer is plugged, replace the strainer with a new fuel pump strainer. See: Powertrain Management/Fuel Delivery and Air Induction/Service and Repair Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Filters > Oil Filter, Engine > Component Information > Technical Service Bulletins > Engine - Noise/Damage Oil Filter Application Importance Oil Filter: Technical Service Bulletins Engine - Noise/Damage Oil Filter Application Importance INFORMATION Bulletin No.: 07-06-01-016B Date: July 27, 2009 Subject: Information on Internal Engine Noise or Damage After Oil Filter Replacement Models: 2010 and Prior Passenger Cars and Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being updated to add model years. Please discard Corporate Bulletin Number 07-06-01-016A (Section 06 - Engine/Propulsion System). Important Engine damage that is the result of an incorrect or improperly installed engine oil filter is not a warrantable claim. The best way to avoid oil filter quality concerns is to purchase ACDelco(R) oil filters directly from GMSPO. Oil filter misapplication may cause abnormal engine noise or internal damage. Always utilize the most recent parts information to ensure the correct part number filter is installed when replacing oil filters. Do not rely on physical dimensions alone. Counterfeit copies of name brand parts have been discovered in some aftermarket parts systems. Always ensure the parts you install are from a trusted source. Improper oil filter installation may result in catastrophic engine damage. Refer to the appropriate Service Information (SI) installation instructions when replacing any oil filter and pay particular attention to procedures for proper cartridge filter element alignment. If the diagnostics in SI (Engine Mechanical) lead to the oil filter as the cause of the internal engine noise or damage, dealers should submit a field product report. Refer to Corporate Bulletin Number 02-00-89-002I (Information for Dealers on How to Submit a Field Product Report). Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Hoses > Heater Hose > Component Information > Service and Repair > Heater Inlet Hose Heater Hose: Service and Repair Heater Inlet Hose Heater Hose Routing Quick Connect Heater Inlet Connector Tool Required: J 38723 Heater Line Quick Connect Separator Remove or Disconnect 1. Engine coolant. 2. Inlet hose from generator bracket. 3. Inlet hose at fender clip. 4. Inlet hose clamp at heater core. water shut off valve or tee fining. - Loosen the clamp enough to slide the clamp away from the fining on the inlet hose. 5. Inlet hose from heater core. 6. Push inlet hose into connector and insert J 38723 or equivalent into connector to release locking tabs. 7. Pull retainer and hose from heater inlet connector. Inspect - O-ring sealing surface on hose/pipe. Adjust - If replacing heater inlet connector, remove retainer from hose and discard, as new connector is equipped with retainer. - If replacing hose, remove retainer from hose and reinsert in connector. - If reusing hose and connector, retainer can remain in place on hose. Install or Connect 1. Push hose into connector until retainer tabs lock. - Pull back on hose to check for proper engagement. 2. Inlet hose to heater core, water shut off valve or tee fitting. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Hoses > Heater Hose > Component Information > Service and Repair > Heater Inlet Hose > Page 2117 3. Inlet hose clamp. 4. Inlet hose mounting screw. Tighten Screw to 30 Nm (22 lb ft). 5. Inlet hose to fender clip. 6. Engine coolant. - Check the system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Hoses > Heater Hose > Component Information > Service and Repair > Heater Inlet Hose > Page 2118 Heater Hose: Service and Repair Heater Outlet Hose Heater Hose Routing Quick Connect Heater Inlet Connector Remove or Disconnect 1. Engine coolant. 2. Outlet hose from fender clip. 3. Outlet hose clamp from heater core, water shut off valve or tee fitting. 4. Outlet hose from heater core. 5. Outlet hose mounting screw. 6. Outlet hose from generator bracket. 7. Outlet hose clamp from water pump. 8. Outlet hose from water pump. Install or Connect 1. Outlet hose to water pump. 2. Outlet hose clamp to water pump. 3. Outlet hose to generator bracket. 4. Generator bracket mounting screw. Tighten screw to 30 Nm (22 lb ft). 5. Outlet hose to heater core. 6. Outlet hose clamp to heater core. 7. Outlet hose to fender clip. 8. Engine coolant. - Check the system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Hoses > Hose/Line HVAC > Component Information > Service Precautions Hose/Line HVAC: Service Precautions Proper O-Ring Installation Improper O-Ring Installation IMPORTANT - Before opening the refrigeration system to the atmosphere, make sure the work area is well ventilated. Welding or steam-cleaning operations should not be done on or near refrigeration system lines or other air conditioning parts on the vehicle. - All metal tubing lines should be free of dents or kinks to prevent loss of system capacity due to line restriction. - The flexible hose lines should never be bent to a radius of less than four times the diameter of the hose. - The flexible hose lines should never be allowed to come within a distance of 6.5 mm (2.5 inches) of the exhaust manifold. - Flexible hose lines should be inspected regularly for leaks or brittleness and replaced with new lines if deterioration or leaking is found. - When disconnecting any fitting in the refrigerant system, the system must be discharged of all Refrigerant-134a. However, proceed very cautiously, regardless of the gage readings. Open very slowly, keeping your face and hands away so that no injury can occur, If pressure is noticed when a fitting is loosened, allow it to bleed off very slowly. NOTICE: Alcohol should never be used In the refrigeration system In an attempt to remove moisture. Damage to system components could occur. - If any refrigerant line is opened to the atmosphere, it should be immediately capped to prevent the entrance of moisture and dirt. These contaminants can cause internal compressor wear or plugged lines in the condenser and evaporator core and expansion (orifice) tubes or compressor inlet screens. - Remove sealing caps from subassemblies just before making connections for final assembly. Use a small amount of clean 525 viscosity refrigerant oil on all tube and hose joints. Use new O-ring seals dipped in 525 viscosity refrigerant oil when assembling joints. The oil will aid in assembly and help to provide a leakproof joint. O-ring seals and seats must be in perfect condition because a burr or a piece of dirt can cause a refrigerant Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Hoses > Hose/Line HVAC > Component Information > Service Precautions > Page 2122 leak. - It is important to use the proper wrenches when making connections on O-ring seal fittings. The use of improper wrenches may damage the connection. The opposing fitting should always be backed up with a wrench to prevent distortion of connecting lines or components. When connecting the flexible hose connections, it is important that the swaged fitting and the flare nut, as well as the coupling to which it is attached, be held at the same time using three different wrenches to prevent turning the fitting and damaging the seat. - Tighten tubing connections to the specified torque. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Hoses > Hose/Line HVAC > Component Information > Service and Repair > Main Unit Hose/Line HVAC: Service and Repair Main Unit Evaporator Tube Remove or Disconnect 1. Negative battery cable. 2. Recover refrigerant. 3. Auxiliary heater pipe, if equipped. 4. Coolant recovery reservoir. 5. Evaporator tube from evaporator. 6. O-ring seal. 7. Evaporator tube from condenser. 8. O-ring seal. Install or Connect 1. Evaporator tube into clip. 2. New O-ring seal. - Coat O-ring seal with 525 viscosity refrigerant oil. 3. Evaporator tube to condenser. Tighten Evaporator tube to 24 Nm (18 lb ft). 4. New O-ring seal. - Coat O-ring seal with 525 viscosity refrigerant oil. 5. Evaporator tube to evaporator. Tighten Evaporator tube to 24 Nm (18 lb ft). 6. Coolant recovery reservoir. 7. Auxiliary heater pipe, if equipped. 8. Negative battery cable. 9. Charge system. - Check system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Hoses > Hose/Line HVAC > Component Information > Service and Repair > Main Unit > Page 2125 Hose/Line HVAC: Service and Repair Auxiliary Unit Auxiliary Evaporator Tube Location Remove or Disconnect 1. Discharge and recover refrigerant from the system. 2. Evaporator tube from evaporator. 3. O-ring seal. 4. Evaporator tube from condenser. 5. O-ring seal. 6. Evaporator tube from auxiliary evaporator hose. 7. O-ring seal. 8. Evaporator tube. Install or Connect 1. Evaporator tube. 2. New O-ring seal. - Coat O-ring seal with 525 viscosity refrigerant oil. 3. Evaporator tube to auxiliary evaporator hose. Tighten evaporator tube to 24 Nm (18 lbs. ft.). 4. New O-ring seal. - Coat O-ring seal with 525 viscosity refrigerant oil. 5. Evaporator tube to condenser. Tighten evaporator tube to 24 Nm (18 lbs. ft.). 6. New O-ring seal. - Coat O-ring seal with 525 viscosity refrigerant oil. 7. Evaporator tube to evaporator. Tighten evaporator tube to 24 Nm (18 lbs. ft.). 8. Refrigerant to the system. - Check the system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Brake Fluid > Component Information > Technical Service Bulletins > Brake Fluid - Level & Filling Recommendations Brake Fluid: Technical Service Bulletins Brake Fluid - Level & Filling Recommendations File In Section: 05 - Brakes Bulletin No.: 00-05-22-004 Date: May, 2000 INFORMATION Subject: Brake Fluid Level and Filling Recommendations Models: 2001 and Prior Passenger Cars and Trucks Many dealers and after-market repair shops advertise multi-point fluid "top-ups" in conjunction with oil changes or regular maintenance packages. These offers often include adding brake fluid to the master cylinder reservoir. There are only two reasons why the brake fluid level in the brake reservoir might go down. The first is that the brake fluid level goes down an acceptable level during normal brake lining wear. When the linings are replaced, the fluid will return to it's original level. The second possible reason for a low fluid level is that fluid is leaking out of the brake system. If fluid is leaking, the brake system requires repair and adding additional fluid will not correct the leak. If the system was properly filled during delivery of the vehicle, no additional fluid should be required under most circumstances between brake pad and/or shoe replacements. This information can be reinforced with the customer by referring them to the Brake Fluid section of their vehicle's Owner's Manual. Guidelines GM vehicles have incorporated a variety of brake fluid reservoir styles. The following guidelines are restricted to the plastic bodied fluid reservoirs and do not affect the original service recommendations for the older style metal bodied units. You may encounter both black plastic and translucent style reservoirs. You may have reservoirs with: ^ A MAX fill mark only ^ A MIN fill mark only ^ Both MAX and MIN marks The translucent style reservoirs do not have to have the covers removed in order to view the fluid level. It is a good practice not to remove the reservoir cover unless necessary to reduce the possibility of contaminating the system. Use the following guidelines to assist in determining the proper fluid level. Important: When adding brake fluid, use Delco Supreme II(R) Brake Fluid, GM P/N 12377967 or equivalent brand bearing the DOT-3 rating only. Important: At no time should the fluid level be allowed to remain in an overfilled condition. Overfilling the brake reservoir may put unnecessary stress on the seals and cover of the reservoir. Use the following guidelines to properly maintain the fluid level. If the reservoir is overfilled, siphon out the additional fluid to comply with the guidelines below. Important: If under any circumstance the brake fluid level is extremely low in the reservoir or the BRAKE warning indicator is illuminated, the brake system should be checked for leaks and the system repaired in addition to bringing the fluid level up to the recommended guidelines outlined below. A leaking brake system will have reduced braking performance and will eventually not work at all. Important: Some vehicles have reservoirs that are very sensitive to brake fluid levels and may cause the BRAKE indicator to flicker on turns as the fluid approaches the minimum required level. If you encounter a vehicle with this concern, increase the fluid level staying within the guidelines outlined below. ^ If the reservoir has a MAX level indicator, the reservoir should be returned to the MAX marking only at the time new brake pads and/or shoes are installed. If the reservoir fluid level is at the half-way point or above do not attempt to add additional brake fluid during routine fluid checks. ^ If the reservoir has both MAX and MIN indicators, the fluid level should be maintained above the MIN indicator during routine fluid checks and returned to the MAX indication only after new brake pads and/or shoes are installed. ^ For reservoirs with only a MIN indication, the fluid level should be maintained above the MIN indicator during routine fluid checks. Return the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Brake Fluid > Component Information > Technical Service Bulletins > Brake Fluid - Level & Filling Recommendations > Page 2131 reservoir fluid level to full only after installing new brake pads and/or shoes. A full reservoir is indicated on translucent, snap cover reservoirs by a fluid level even with the top level of the view window imprinted into the side of the reservoir. On screw top models in black or translucent plastic, the full level is just below the bottom of the filler neck. Parts Information Part Number Description 12377967 Brake Fluid Parts are currently available from GMSPO. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Brake Fluid > Component Information > Technical Service Bulletins > Page 2132 Brake Fluid: Specifications Brake System DOT 3 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Coolant > Component Information > Technical Service Bulletins > Cooling System - DEX-COOL(R) Coolant Leak Detection Dye Coolant: Technical Service Bulletins Cooling System - DEX-COOL(R) Coolant Leak Detection Dye Bulletin No.: 05-06-02-002B Date: January 18, 2008 INFORMATION Subject: DEX-COOL(R) Coolant - New Leak Detection Dye J 46366 - Replaces J 29545-6 Models: 1996-2008 GM Passenger Cars and Light/Medium Duty Trucks* (including Saturn) 1997-2008 Isuzu T-Series Medium Duty Tilt Cab Models Built in Janesville and Flint 1999-2008 Isuzu N-Series Medium Duty Commercial Models with 5.7L or 6.0L Gas Engine 2003-2008 HUMMER H2 2006-2008 HUMMER H3 2005-2008 Saab 9-7X *EXCLUDING 2006 and Prior Chevrolet Aveo, Epica, Optra, Vivant and Pontiac Matiz, Wave Supercede: This bulletin is being revised to include additional model years. Please discard Corporate Bulletin Number 05-06-02-002A (Section 06 - Engine/Propulsion System). Leak detection dye P/N 12378563 (J 29545-6) (in Canada P/N 88900915) may cause DEX-COOL(R) coolant to appear green in a black vessel making it appear to be conventional (green) coolant. This may cause a technician to add conventional coolant to a low DEX-COOL(R) system thus contaminating it. The green DEX-COOL(R) appearance is caused by the color of the leak detection dye which alters the color of the DEX-COOL(R) coolant. A new leak detection dye P/N 89022219 (J 46366) (in Canada P/N 89022220) has been released that does not alter the appearance of the DEX-COOL(R) coolant. When adding the new leak detection dye the color of the DEX-COOL(R) coolant will not change. For detecting leaks on any system that uses DEX-COOL(R) leak detection dye P/N 89022219 (in Canada P/N 89022220) should be used. The new leak detection dye can be used with both conventional and DEX-COOL(R) coolant. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Coolant > Component Information > Technical Service Bulletins > Cooling System - DEX-COOL(R) Coolant Leak Detection Dye > Page 2137 Coolant: Technical Service Bulletins Cooling System - Coolant Recycling Information Bulletin No.: 00-06-02-006D Date: August 15, 2006 INFORMATION Subject: Engine Coolant Recycling and Warranty Information Models: 2007 and Prior GM Passenger Cars and Trucks (Including Saturn) 2007 and Prior HUMMER Vehicles 2005-2007 Saab 9-7X Attention: Please address this bulletin to the Warranty Claims Administrator and the Service Manager. Supercede: This bulletin is being revised to adjust the title and Include Warranty Information. Please discard Corporate Bulletin Number 00-06-02-006C (Section 06 - Engine/Propulsion System). Coolant Reimbursement Policy General Motors supports the use of recycled engine coolant for warranty repairs/service, providing a GM approved engine coolant recycling system is used. Recycled coolant will be reimbursed at the GMSPO dealer price for new coolant plus the appropriate mark-up. When coolant replacement is required during a warranty repair, it is crucial that only the relative amount of engine coolant concentrate be charged, not the total diluted volume. In other words: if you are using two gallons of pre-diluted (50:50) recycled engine coolant to service a vehicle, you may request reimbursement for one gallon of GM Goodwrench engine coolant concentrate at the dealer price plus the appropriate warranty parts handling allowance. Licensed Approved DEX-COOL(R) Providers Important: USE OF NON-APPROVED VIRGIN OR RECYCLED DEX-COOL(R) OR DEVIATIONS IN THE FORM OF ALTERNATE CHEMICALS OR ALTERATION OF EQUIPMENT, WILL VOID THE GM ENDORSEMENT, MAY DEGRADE COOLANT SYSTEM INTEGRITY AND PLACE THE COOLING SYSTEM WARRANTY UNDER JEOPARDY. Shown in Table 1 are the only current licensed and approved providers of DEX-COOL(R). Products that are advertised as "COMPATIBLE" or "RECOMMENDED" for use with DEX-COOL(R) have not been tested or approved by General Motors. Non-approved coolants may degrade the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Coolant > Component Information > Technical Service Bulletins > Cooling System - DEX-COOL(R) Coolant Leak Detection Dye > Page 2138 coolant system integrity and will no longer be considered a 5 yr/150,000 mile (240,000 km) coolant. Coolant Removal Services/Recycling The tables include all coolant recycling processes currently approved by GM. Also included is a primary phone number and demographic information. Used DEX-COOL(R) can be combined with used conventional coolant (green) for recycling. Depending on the recycling service and/or equipment, it is then designated as a conventional 2 yr/30,000 mile (50,000 km) coolant or DEX-COOL(R) 5 yr/150,000 mile (240,000 km) coolant. Recycled coolants as designated in this bulletin may be used during the vehicle(s) warranty period. DEX-COOL(R) Recycling The DEX-COOL(R) recycling service listed in Table 2 has been approved for recycling waste engine coolants (DEX-COOL) or conventional) to DEX-COOL(R) with 5 yr/150,000 mile (240,000 km) usability. Recycling Fluid Technologies is the only licensed provider of Recycled DEX-COOL(R) meeting GM6277M specifications and utilizes GM approved inhibitor packages. This is currently a limited program being monitored by GM Service Operations which will be expanded as demand increases. Conventional (Green) Recycling Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Coolant > Component Information > Technical Service Bulletins > Cooling System - DEX-COOL(R) Coolant Leak Detection Dye > Page 2139 Processes shown in the Table 3 are capable of recycling waste engine coolants (DEX-COOL(R) or conventional) to a conventional (green) coolant. Recycling conventional coolant can be accomplished at your facility by a technician using approved EQUIPMENT (listed by model number in Table 3), or by an approved coolant recycling SERVICE which may recycle the coolant at your facility or at an offsite operation. Refer to the table for GM approved coolant recyclers in either of these two categories. Should you decide to recycle the coolant yourself, strict adherence to the operating procedures is imperative. Use ONLY the inhibitor chemicals supplied by the respective (GM approved) recycling equipment manufacturer. Sealing Tablets Cooling System Sealing Tablets (Seal Tabs) should not be used as a regular maintenance item after servicing an engine cooling system. Discoloration of coolant can occur if too many seal tabs have been inserted into the cooling system. This can occur if seal tabs are repeatedly used over the service life of a vehicle. Where appropriate, seal tabs may be used if diagnostics fail to repair a small leak in the cooling system. When a condition appears in which seal tabs may be recommended, a specific bulletin will be released describing their proper usage. Water Quality The integrity of the coolant is dependent upon the quality of DEX-COOL(R) and water. DEX-COOL(R) is a product that has enhanced protection capability as well as an extended service interval. These enhanced properties may be jeopardized by combining DEX-COOL(R) with poor quality water. If you suspect the water in your area of being poor quality, it is recommended you use distilled or de-ionized water with DEX-COOL(R). "Pink" DEX-COOL(R) DEX-COOL(R) is orange in color to distinguish it from other coolants. Due to inconsistencies in the mixing of the dyes used with DEX-COOL(R), some batches may appear pink after time. The color shift from orange to pink does not affect the integrity of the coolant, and still maintains the 5 yr/150,000 mile (240,000 km) service interval. Back Service Only use DEX-COOL(R) if the vehicle was originally equipped with DEX-COOL(R). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Coolant > Component Information > Technical Service Bulletins > Cooling System - DEX-COOL(R) Coolant Leak Detection Dye > Page 2140 Contamination Mixing conventional green coolant with DEX-COOL(R) will degrade the service interval from 5 yrs./150,000 miles (240,000 km) to 2 yrs./30,000 miles (50,000 km) if left in the contaminated condition. If contamination occurs, the cooling system must be flushed twice immediately and re-filled with a 50/50 mixture of DEX-COOL(R) and clean water in order to preserve the enhanced properties and extended service interval of DEX-COOL(R). After 5 years/150,000 miles (240,000 km) After 5 yrs/150,000 miles (240,000 km), the coolant should be changed, preferably using a coolant exchanger. If the vehicle was originally equipped with DEX-COOL(R) and has not had problems with contamination from non-DEX-COOL(R) coolants, then the service interval remains the same, and the coolant does not need to be changed for another 5 yrs/150,000 miles (240,000 km) Equipment (Coolant Exchangers) The preferred method of performing coolant replacement is to use a coolant exchanger. A coolant exchanger can replace virtually all of the old coolant with new coolant. Coolant exchangers can be used to perform coolant replacement without spillage, and facilitate easy waste collection. They can also be used to lower the coolant level in a vehicle to allow for less messy servicing of cooling system components. It is recommended that you use a coolant exchanger with a vacuum feature facilitates removing trapped air from the cooling system. This is a substantial time savings over repeatedly thermo cycling the vehicle and topping-off the radiator. The vacuum feature also allows venting of a hot system to relieve system pressure. Approved coolant exchangers are available through the GMDE (General Motors Dealer Equipment) program. For refilling a cooling system that has been partially or fully drained for repairs other than coolant replacement, the Vac-N-Fill Coolant Refill Tool (GE-47716) is recommended to facilitate removal of trapped air from the cooling system during refill. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Coolant > Component Information > Specifications > Capacity Specifications Coolant: Capacity Specifications Coolant Capacity, Qts. Less A/C .............................................................................................................................................. ........................................................................ 17.5 With A/C ............................................................. ........................................................................................................................................................... 20 Radiator Cap Relief Pressure, Lbs. ..................................................................................................... ............................................................................... 15 Thermo. Opening Temp., deg.F ..................... .............................................................................................................................................................. .... 195 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Coolant > Component Information > Specifications > Capacity Specifications > Page 2143 Coolant: Fluid Type Specifications ENGINE COOLANT A 50/50 mixture of clean water (preferably distilled) and use only GM Goodwrench DEX-COOL or Havoline DEX-COOL (orange-colored, silicate-free) coolant, or an approved recycled coolant conforming to GM Specification 6038-M (GM P/N 1052103). CAUTION: If silicate coolant is added to the cooling system, premature engine, heater core or radiator corrosion may result. In addition, the coolant will require change SOONER, at 50 000 km (30,000 miles) or 24 months. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Fluid - A/T > Component Information > Technical Service Bulletins > A/T - DEXRON(R)-VI Fluid Information Fluid - A/T: Technical Service Bulletins A/T - DEXRON(R)-VI Fluid Information INFORMATION Bulletin No.: 04-07-30-037E Date: April 07, 2011 Subject: Release of DEXRON(R)-VI Automatic Transmission Fluid (ATF) Models: 2008 and Prior GM Passenger Cars and Light Duty Trucks 2003-2008 HUMMER H2 2006-2008 HUMMER H3 2005-2007 Saturn Relay 2005 and Prior Saturn L-Series 2005-2007 Saturn ION 2005-2008 Saturn VUE with 4T45-E 2005-2008 Saab 9-7X Except 2008 and Prior Chevrolet Aveo, Equinox Except 2006 and Prior Chevrolet Epica Except 2007 and Prior Chevrolet Optra Except 2008 and Prior Pontiac Torrent, Vibe, Wave Except 2003-2005 Saturn ION with CVT or AF23 Only Except 1991-2002 Saturn S-Series Except 2008 and Prior Saturn VUE with CVT, AF33 or 5AT (MJ7/MJ8) Transmission Only Except 2008 Saturn Astra Attention: DEXRON(R)-VI Automatic Transmission Fluid (ATF) is the only approved fluid for warranty repairs for General Motors transmissions/transaxles requiring DEXRON(R)-III and/or prior DEXRON(R) transmission fluids. Supercede: This bulletin is being revised to update information. Please discard Corporate Bulletin Number 04-07-30-037D (Section 07 - Transmission/Transaxle). MANUAL TRANSMISSIONS / TRANSFER CASES and POWER STEERING The content of this bulletin does not apply to manual transmissions or transfer cases. Any vehicle that previously required DEXRON(R)-III for a manual transmission or transfer case should now use P/N 88861800. This fluid is labeled Manual Transmission and Transfer Case Fluid. Some manual transmissions and transfer cases require a different fluid. Appropriate references should be checked when servicing any of these components. Power Steering Systems should now use P/N 9985010 labeled Power Steering Fluid. Consult the Parts Catalog, Owner's Manual, or Service Information (SI) for fluid recommendations. Some of our customers and/or General Motors dealerships/Saturn Retailers may have some concerns with DEXRON(R)-VI and DEXRON(R)-III Automatic Transmission Fluid (ATF) and transmission warranty claims. DEXRON(R)-VI is the only approved fluid for warranty repairs for General Motors transmissions/transaxles requiring DEXRON(R)-III and/or prior DEXRON(R) transmission fluids (except as noted above). Please remember that the clean oil reservoirs of the J-45096 - Flushing and Flow Tester machine should be purged of DEXRON(R)-III and filled with DEXRON(R)-VI for testing, flushing or filling General Motors transmissions/transaxles (except as noted above). DEXRON(R)-VI can be used in any proportion in past model vehicles equipped with an automatic transmission/transaxle in place of DEXRON(R)-III (i.e. topping off the fluid in the event of a repair or fluid change). DEXRON(R)-VI is also compatible with any former version of DEXRON(R) for use in automatic transmissions/transaxles. DEXRON(R)-VI ATF General Motors Powertrain has upgraded to DEXRON(R)-VI ATF with the start of 2006 vehicle production. Current and prior automatic transmission models that had used DEXRON(R)-III must now only use DEXRON(R)-VI. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Fluid - A/T > Component Information > Technical Service Bulletins > A/T - DEXRON(R)-VI Fluid Information > Page 2148 All 2006 and future model transmissions that use DEXRON(R)-VI are to be serviced ONLY with DEXRON(R)-VI fluid. DEXRON(R)-VI is an improvement over DEXRON(R)-III in the following areas: * These ATF change intervals remain the same as DEXRON(R)-III for the time being. 2006-2008 Transmission Fill and Cooler Flushing Some new applications of the 6L80 six speed transmission will require the use of the J 45096 Flushing and Flow Tester to accomplish transmission fluid fill. The clean oil reservoir of the machine should be purged of DEXRON(R)-III and filled with DEXRON(R)-VI. Parts Information Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Fluid - A/T > Component Information > Technical Service Bulletins > A/T - DEXRON(R)-VI Fluid Information > Page 2149 Fluid - A/T: Technical Service Bulletins A/T - Water Or Coolant Contamination Information INFORMATION Bulletin No.: 08-07-30-035B Date: November 01, 2010 Subject: Information on Water or Ethylene Glycol in Transmission Fluid Models: 2011 and Prior GM Passenger Cars and Light Duty Trucks with Automatic Transmission Supercede: This bulletin is being revised to update model years. Please discard Corporate Bulletin Number 08-07-30-035A (Section 07 - Transmission/Transaxle). Water or ethylene glycol in automatic transmission fluid (ATF) is harmful to internal transmission components and will have a negative effect on reliability and durability of these parts. Water or ethylene glycol in ATF will also change the friction of the clutches, frequently resulting in shudder during engagement or gear changes, especially during torque converter clutch engagement. Indications of water in the ATF may include: - ATF blowing out of the transmission vent tube. - ATF may appear cloudy or, in cases of extreme contamination, have the appearance of a strawberry milkshake. - Visible water in the oil pan. - A milky white substance inside the pan area. - Spacer plate gaskets that appear to be glued to the valve body face or case. - Spacer plate gaskets that appear to be swollen or wrinkled in areas where they are not compressed. - Rust on internal transmission iron/steel components. If water in the ATF has been found and the source of the water entry has not been identified, or if a leaking in-radiator transmission oil cooler is suspected (with no evidence of cross-contamination in the coolant recovery reservoir), a simple and quick test kit is available that detects the presence of ethylene glycol in ATF. The "Gly-Tek" test kit, available from the Nelco Company, should be obtained and the ATF tested to make an accurate decision on the need for radiator replacement. This can help to prevent customer comebacks if the in-radiator transmission oil cooler is leaking and reduce repair expenses by avoiding radiator replacement if the cooler is not leaking. These test kits can be obtained from: Nelco Company Test kits can be ordered by phone or through the website listed above. Orders are shipped standard delivery time but can be shipped on a next day delivery basis for an extra charge. One test kit will complete 10 individual fluid sample tests. For vehicles repaired under warranty, the cost of the complete test kit plus shipping charges should be divided by 10 and submitted on the warranty claim as a net item. The transmission should be repaired or replaced based on the normal cost comparison procedure. Important If water or coolant is found in the transmission, the following components MUST be replaced. - Replace all of the rubber-type seals. - Replace all of the composition-faced clutch plates and/or bands. - Replace all of the nylon parts. - Replace the torque converter. - Thoroughly clean and rebuild the transmission, using new gaskets and oil filter. Important The following steps must be completed when repairing or replacing. Flush and flow check the transmission oil cooler using J 45096. Refer to Corporate Bulletin Number 02-07-30-052F- Automatic Transmission Oil Cooler Flush and Flow Test Essential Tool J 45096 TransFlow. - Thoroughly inspect the engine cooling system and hoses and clean/repair as necessary. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Fluid - A/T > Component Information > Technical Service Bulletins > A/T - DEXRON(R)-VI Fluid Information > Page 2150 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Fluid - A/T > Component Information > Specifications > Capacity Specifications Fluid - A/T: Capacity Specifications 4L60-E TRANSMISSION Pan removal ............................................................................................... ................................................................................................................. 5.0 qts. Overhaul ............... .............................................................................................................................................................. ...................................... 11.0 qts. 4L80-E TRANSMISSION Pan removal ............................................................................................... ................................................................................................................. 7.7 qts. Overhaul ............... .............................................................................................................................................................. ...................................... 13.5 qts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Fluid - A/T > Component Information > Specifications > Capacity Specifications > Page 2153 Fluid - A/T: Fluid Type Specifications DEXRON-III Automatic Transmission Fluid (or equivalent). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Fluid - A/T > Component Information > Testing and Inspection > Turbo Hydra-Matic 4L60-E Fluid - A/T: Testing and Inspection Turbo Hydra-Matic 4L60-E Fluid level should be checked at every engine oil change. Frequency of change for transmission fluid is dependent on the type of driving conditions in which the vehicle is used. If the transmission is subjected to severe service such as: use in heavy city traffic when the outside temperature regularly reaches 90°F, use in very hilly or mountainous areas, commercial use such as taxi or delivery service, the fluid should be changed every 15,000 miles when using Dexron II and 50,000 miles when using Dexron III or equivalent. Otherwise, change the fluid every 100,000 miles, using Dexron II, III or equivalent automatic transmission fluid. When checking fluid, ensure vehicle is at operating temperature (190°-200°F), which can be obtained by 15 miles of highway-type driving. After transmission fluid is at operating temperature, use the following procedure to check fluid level: 1. Ensure vehicle is on a level surface, then move gear selector to the Park position. 2. Apply parking brake and block wheels, then allow engine to run at idle speed for three minutes with accessories off. 3. Check fluid level, color and condition. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Fluid - A/T > Component Information > Testing and Inspection > Turbo Hydra-Matic 4L60-E > Page 2156 Fluid - A/T: Testing and Inspection Turbo Hydra-Matic 4L80-E & 4L80-EHD Check fluid at regular intervals. Noticing a change in color, odor or fluid level can serve as a warning of possible transmission problems. To check fluid level, bring fluid to operating temperature of 200°F. With vehicle on a level surface, engine idling in park and parking brake applied, the level on the dipstick should be at the Full mark. To bring the fluid level from the Add mark to the Full mark requires one pint of fluid. If additional fluid is required, use only Dexron II automatic transmission fluid. When adding fluid, do not overfill, as foaming and loss of fluid through the vent may occur as the fluid heats up. Also, If fluid level is too low, complete loss of drive may occur especially when cold, which can cause transmission failure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Fluid - A/T > Component Information > Service and Repair > Turbo Hydra-Matic 4L80-E & 4L80-EHD Fluid - A/T: Service and Repair Turbo Hydra-Matic 4L80-E & 4L80-EHD The normal schedule is 30,000 miles for vehicles under 8600 lbs. GVWR OR 24,000 for vehicles over 8600 lbs. GVWR. If vehicle is driven in heavy city traffic where outside temperature regularly reaches 90°F or higher, in hilly or mountain terrain, is used for frequent trailer pulling or is used in taxi, police, delivery or other commercial service, maintenance schedule for drain and refill is 15,000 miles for all vehicles under 8600 lbs. GVWR or 12,000 miles for vehicles over 8600 lbs. GVWR. Change fluid and filter as follows: 1. Raise vehicle and position drain pan under transmission pan. 2. Remove front and side attaching bolts from the oil pan. 3. Loosen rear attaching bolts approximately four turns. 4. Carefully pry transmission pan loose and allow fluid to drain. 5. Remove rear attaching bolts, pan and pan gasket. 6. Drain remaining fluid from pan, then clean pan and gasket surfaces with solvent and dry with compressed air. 7. Remove transmission screen. Remove seal from intake pipe or case bore. 8. Replace screen if applicable, or thoroughly clean screen assembly with solvent and dry with compressed air. 9. Install seal on intake pipe, then install screen assembly. 10. Install gasket on pan, then install pan and tighten to specifications. 11. Lower vehicle and add approximately 9 pts. of Dexron II type transmission fluid through filler tube. 12. Start engine and let run at idle, then with brakes applied move selector lever through each gear range. 13. Place transmission in Park position and check fluid level. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Fluid - A/T > Component Information > Service and Repair > Turbo Hydra-Matic 4L80-E & 4L80-EHD > Page 2159 Fluid - A/T: Service and Repair Turbo Hydra-Matic 4L60-E Changing Fluid 1. Raise and support vehicle. 2. Loosen two bolts attaching right side of transmission support to frame rail. 3. Remove two bolts attaching left side transmission support to frame rail. 4. Using suitable transmission jack, support and slightly raise transmission. 5. Slide transmission support rearward enough to access rear oil pan attaching bolts. 6. Place drain pan under transmission oil pan, loosen pan bolts on front of pan, pry carefully with screwdriver to loosen oil pan, and allow fluid to drain. 7. Remove remaining oil pan bolts, oil pan, and gasket. 8. Drain fluid from pan, then clean pan and dry thoroughly with compressed air. 9. Remove oil filter to valve body bolt, then remove filter and gasket, replace with new filter and gasket. 10. Install new gasket on oil pan, then oil pan and attaching bolts. Tighten attaching bolts to specification. 11. Lower vehicle and add five quarts of automatic transmission fluid through filler tube. 12. With selector lever in Park and parking brake applied, start engine and let idle. Do not race engine. 13. Move selector lever through each gear range, then return lever to park. 14. Check fluid, then add additional fluid to bring level between dimples on dipstick. Adding Fluid to A Dry Transmission 1. Add transmission fluid through filler tube until oil level is between the "ADD" and "HOT" marks on dipstick. 2. Place selector lever in park, depress accelerator to place carburetor on fast idle cam, and move selector lever through each range. Do not race engine. 3. With selector lever in park, engine running at idle (1-3 minutes), and vehicle on level surface, check fluid level and add additional fluid to bring level between dimples on dipstick. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Fluid - M/T > Component Information > Specifications > Capacity Specifications Fluid - M/T: Capacity Specifications 5 SPEED TRANSMISSION OIL 85 mm & 109 mm ................................................................................................................................ ....................................................................... 3.6 pts. New Venture Gear 4500 ...................................................................................................................... ....................................................................... 8.0 pts. New Venture Gear 3500 ...................................................................................................................... ....................................................................... 4.4 pts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Fluid - M/T > Component Information > Specifications > Capacity Specifications > Page 2164 Fluid - M/T: Fluid Type Specifications New Venture Gear 3500 Synchromesh Transmission Fluid P/N 9985648 New Venture Gear 4500 Castrol Syntorq LT Transmission Fluid. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Fluid - Differential > Component Information > Technical Service Bulletins > Drivetrain - Rear Axle Lubricant Compatibility & Usage Fluid - Differential: Technical Service Bulletins Drivetrain - Rear Axle Lubricant Compatibility & Usage File in Section: 04 - Driveline Axle Bulletin No.: 99-04-20-001 Date: June, 1999 INFORMATION Subject: Rear Axle Lubricant Compatibility and Usage Models: 1999 Cadillac Escalade 1988-99 Chevrolet and GMC C/K, G Van and P1-3 Series Models Built after the VIN Breakpoints (C/K) listed. This bulletin is being revised to add the 1999 Model Year, VIN Breakpoint information, and additional text Please discard Corporate Bulletin Number 86-42-04 (Section 4 - Driveline/Axle). This bulletin is being issued to inform dealers about the compatibility and usage of the new Fuel Efficient SAE 75W-90 Synthetic Axle Lubricant, GM P/N 12378261 (In Canada use P/N 10953455), with current axles, and with the non-synthetic axle lubricant, GM P/N 1052271 (In Canada use P/N 10950849), for the rear axles on the above light-duty trucks. Testing has shown that the new synthetic lubricant will chemically attack the Room Temperature Vulcanizing (RTV) sealant. Use only the non-synthetic lubricant, P/N 1052271, in axles using RTV sealant (See 9.5 and 10.5 information below). American Axle and Manufacturing (A.A.M.) has approved the use of the new Fuel Efficient SAE 75W-90 synthetic axle lubricant for rear axles with the following restrictions: ^ All 8.6 inch axles are compatible as originally built. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Fluid - Differential > Component Information > Technical Service Bulletins > Drivetrain - Rear Axle Lubricant Compatibility & Usage > Page 2169 ^ 9.5 inch axles on vehicles built prior to mid-February 1998 are NOT compatible because RTV sealant is used on the cover pans. On vehicles built after mid-February 1998 and equipped with 9.5 inch rear axles, synthetic lubricant, P/N 12378261, can be used because the RTV was replaced with a gasket. Other mid-February changes to the 9.5 inch rear axles include a new cover pan and cover pan fasteners common to other axles. Important: The new cover pan is not retrofittable to the housing of 9.5 inch axles on vehicles built prior to mid-February 1998. A new retrofit kit is available that will enable the use of synthetic lubricant for vehicles built after mid-February, 1998. ^ All 10.5 inch axles prior to March 3, 1999 are compatible if the axle shaft hub seal (RTV) is replaced with P/N 327739 gasket when changing to synthetic lubricant. As a product improvement, this new lubricant has been released into 1999 current production C/K vehicles built after the above VIN breakpoints (Except HD3SOO models which use 75W-140 synthetic lubricant, P/N 12346140). It is recommended that synthetic lubricant be used when changing rear axle lubricant for the following reasons: ^ Potential fuel economy ^ Lower operating temperature under severe usage conditions Important: ^ You do not need to wash/rinse any non-synthetic lubricant from the axle cavity when changing over to a synthetic lubricant. However, you should remove debris from the magnet and the bottom of the axle cavity whenever the axle fluid is changed. ^ On light-duty trucks equipped with locking differentials, do NOT use a limited-slip additive. Parts Information Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Fluid - Differential > Component Information > Technical Service Bulletins > Drivetrain - Rear Axle Lubricant Compatibility & Usage > Page 2170 Fluid - Differential: Technical Service Bulletins Drivetrain - Recommended Axle Lubricant File In Section: 0 - General Information Bulletin No.: 76-02-02A Date: October, 1998 INFORMATION Subject: Recommended Axle Lubricant Models: 1999 and Prior Rear Wheel Drive Passenger Cars, Light and Medium Duty Trucks, and Four Wheel Drive Vehicles This bulletin is being revised to add the 1998 and 1999 Model Years and add Vehicle Line and Recommended Axle Lubricant Information. Please discard Corporate Bulletin Number 76-02-02 (Section 0 - General Information). The following tables provide the latest information on recommended axle lubricant. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Fluid - Differential > Component Information > Technical Service Bulletins > Drivetrain - Rear Axle Lubricant Compatibility & Usage > Page 2171 Parts Information Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Fluid - Differential > Component Information > Specifications > Capacity Specifications Fluid - Differential: Capacity Specifications Chevrolet 8 1/2 inch ............................................................................................................................. ..................................................................... 4.2 pts. Chevrolet 9 1/2 inch ............................................................................................................................. ..................................................................... 5.5 pts. Dana 9 3/4 & 10 1/2 inch ..................................................................................................................... ..................................................................... 5.5 pts. Chevrolet 10 1/2 inch ........................................................................................................................... ..................................................................... 7.2 pts. Dana 11 inch ....................................................................................................................................... ........................................................................ 8.2 pts. Rockwell 12 inch .................................................................................................................................. .................................................................... 14.0 pts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Fluid - Differential > Component Information > Specifications > Capacity Specifications > Page 2174 Fluid - Differential: Fluid Type Specifications Rear Axle - Locking Differential (G80) This Article has been updated by TSB # 76-02-02A. SAE 80W-90 GL5 Gear Lubricant, GM P/N 1052271. Do not use limited slip additive. Rear Axle - Non-Locking Differential Standard Differential (Non-Locking) SAE 80W-90 GL-5 Gear Lubricant GM P/N 1052271 HD-3500 Dana 11.0 inch Axle SAE 75W-140 Synthetic Gear lubricant GM P/N 12378261 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Engine Oil > Component Information > Technical Service Bulletins > Engine - GM dexos 1 and dexos 2(R) Oil Specifications Engine Oil: Technical Service Bulletins Engine - GM dexos 1 and dexos 2(R) Oil Specifications INFORMATION Bulletin No.: 11-00-90-001 Date: March 14, 2011 Subject: Global Information for GM dexos1(TM) and GM dexos2(TM) Engine Oil Specifications for Spark Ignited and Diesel Engines, Available Licensed Brands, and Service Fill for Adding or Complete Oil Change Models: 2012 and Prior GM Passenger Cars and Trucks Excluding All Vehicles Equipped with Duramax(TM) Diesel Engines GM dexos 1(TM) Information Center Website Refer to the following General Motors website for dexos 1(TM) information about the different licensed brands that are currently available: http://www.gmdexos.com GM dexos 1(TM) Engine Oil Trademark and Icons The dexos(TM) specification and trademarks are exclusive to General Motors, LLC. Only those oils displaying the dexos‹›(TM) trademark and icon on the front label meet the demanding performance requirements and stringent quality standards set forth in the dexos‹›(TM) specification. Look on the front label for any of the logos shown above to identify an authorized, licensed dexos 1(TM) engine oil. GM dexos 1(TM) Engine Oil Specification Important General Motors dexos 1(TM) engine oil specification replaces the previous General Motors specifications GM6094M, GM4718M and GM-LL-A-025 for most GM gasoline engines. The oil specified for use in GM passenger cars and trucks, PRIOR to the 2011 model year remains acceptable for those previous vehicles. However, dexos 1(TM) is backward compatible and can be used in those older vehicles. In North America, starting with the 2011 model year, GM introduced dexos 1(TM) certified engine oil as a factory fill and service fill for gasoline engines. The reasons for the new engine oil specification are as follows: - To meet environmental goals such as increasing fuel efficiency and reducing engine emissions. - To promote long engine life. - To minimize the number of engine oil changes in order to help meet the goal of lessening the industry's overall dependence on crude oil. dexos 1(TM) is a GM-developed engine oil specification that has been designed to provide the following benefits: - Further improve fuel economy, to meet future corporate average fuel economy (CAFE) requirements and fuel economy retention by allowing the oil to maintain its fuel economy benefits throughout the life of the oil. - More robust formulations for added engine protection and aeration performance. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Engine Oil > Component Information > Technical Service Bulletins > Engine - GM dexos 1 and dexos 2(R) Oil Specifications > Page 2179 - Support the GM Oil Life System, thereby minimizing the replacement of engine oil, before its life has been depleted. - Reduce the duplication of requirements for a large number of internal GM engine oil specifications. International Lubricants Standardization and Approval Committee (ILSAC) GF-5 Standard In addition to GM dexos 1(TM), a new International Lubricants Standardization and Approval Committee (ILSAC) standard called GF-5, was introduced in October 2010. - There will be a corresponding API category, called: SN Resource Conserving. The current GF-4 standard was put in place in 2004 and will become obsolete in October 2011. Similar to dexos 1(TM), the GF-5 standard will use a new fuel economy test, Sequence VID, which demands a statistically significant increase in fuel economy versus the Sequence VIB test that was used for GF-4. - It is expected that all dexos 1(TM) approved oils will be capable of meeting the GF-5 standard. However, not all GF-5 engine oils will be capable of meeting the dexos 1(TM) specification. - Like dexos(TM), the new ILSAC GF-5 standard will call for more sophisticated additives. The API will begin licensing marketers during October 2010, to produce and distribute GF-5 certified products, which are expected to include SAE 0W-20, 0W-30, 5W-20, 5W-30 and 10W-30 oils. Corporate Average Fuel Economy (CAFE) Requirements Effect on Fuel Economy Since CAFE standards were first introduced in 1974, the fuel economy of cars has more than doubled, while the fuel economy of light trucks has increased by more than 50 percent. Proposed CAFE standards call for a continuation of increased fuel economy in new cars and trucks. To meet these future requirements, all aspects of vehicle operation are being looked at more critically than ever before. New technology being introduced in GM vehicles designed to increase vehicle efficiency and fuel economy include direct injection, cam phasing, turbocharging and active fuel management (AFM). The demands of these new technologies on engine oil also are taken into consideration when determining new oil specifications. AFM for example can help to achieve improved fuel economy. However alternately deactivating and activating the cylinders by not allowing the intake and exhaust valves to open contributes to additional stress on the engine oil. Another industry trend for meeting tough fuel economy mandates has been a shift toward lower viscosity oils. dexos 1(TM) will eventually be offered in several viscosity grades in accordance with engine needs: SAE 0W-20, 5W-20, 0W-30 and 5W-30. Using the right viscosity grade oil is critical for proper engine performance. Always refer to the Maintenance section of a vehicle Owner Manual for the proper viscosity grade for the engine being serviced. GM Oil Life System in Conjunction With dexos (TM) Supports Extended Oil Change Intervals To help conserve oil while maintaining engine protection, many GM vehicles are equipped with the GM Oil Life System. This system can provide oil change intervals that exceed the traditional 3,000 mile (4,830 km) recommendation. The dexos (TM) specification, with its requirements for improved oil robustness, compliments the GM Oil Life System by supporting extended oil change intervals over the lifetime of a vehicle. If all GM customers with GM Oil Life System equipped vehicles would use the system as intended, GM estimates that more than 100 million gallons of oil could be saved annually. GM dexos 2(TM) Information Center Website Refer to the following General Motors website for dexos 2(TM) information about the different licensed brands that are currently available: http://www.gmdexos.com GM dexos 2(TM) Engine Oil Trademark and Icons Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Engine Oil > Component Information > Technical Service Bulletins > Engine - GM dexos 1 and dexos 2(R) Oil Specifications > Page 2180 The dexos (TM) specification and trademarks are exclusive to General Motors, LLC. Only those oils displaying the dexos (TM) trademark and icon on the front label meet the demanding performance requirements and stringent quality standards set forth in the dexos (TM)specification. Look on the front label for any of the logos shown above to identify an authorized, licensed dexos 2(TM) engine oil. GM dexos 2(TM) Engine Oil Specification - dexos 2(TM) is approved and recommended by GM for use in Europe starting in model year 2010 vehicles, regardless of where the vehicle was manufactured. - dexos 2(TM) is the recommended service fill oil for European gasoline engines. Important The Duramax(TM) diesel engine is the exception and requires lubricants meeting specification CJ-4. - dexos 2(TM) is the recommended service fill oil for European light-duty diesel engines and replaces GM-LL-B-025 and GM-LL-A-025. - dexos 2(TM) protects diesel engines from harmful soot deposits and is designed with limits on certain chemical components to prolong catalyst life and protect expensive emission reduction systems. It is a robust oil, resisting degradation between oil changes and maintaining optimum performance longer. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Engine Oil > Component Information > Specifications > Capacity Specifications Engine Oil: Capacity Specifications Engine Oil ............................................................................................................................................ .............................................. 4.73 Liters (5.0 Quarts) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Engine Oil > Component Information > Specifications > Capacity Specifications > Page 2183 Engine Oil: Fluid Type Specifications GM Goodwrench motor oil or equivalent for API Service with STARBURST SYMBOL of the recommended viscosity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Refrigerant > Component Information > Technical Service Bulletins > A/C - Refrigerant Recovery/Recycling/Equipment Refrigerant: Technical Service Bulletins A/C - Refrigerant Recovery/Recycling/Equipment Bulletin No.: 08-01-38-001 Date: January 25, 2008 INFORMATION Subject: Information On New GE-48800 CoolTech Refrigerant Recovery/Recharge Equipment Models: 2008 and Prior GM Passenger Cars and Light Duty Trucks (Including Saturn) 2008 and Prior HUMMER H2, H3 2005-2008 Saab 9-7X Attention: This bulletin is being issued to announce the release of GM approved Air Conditioning (A/C) Refrigerant Recovery and Recharging Equipment that meets the new Society of Automotive Engineers (SAE) J2788 Refrigerant Recovery Standards. The ACR2000 (J-43600) cannot be manufactured in its current state after December 2007 and will be superseded by GE-48800. The new J2788 standard does not require that GM Dealers replace their ACR2000 units. ACR2000's currently in use are very capable of servicing today's refrigerant systems when used correctly and can continue to be used. Details regarding the new SAE J2788 standard are outlined in GM Bulletin 07-01-38-004. Effective February 1 2008, new A/C Refrigerant Recovery/Recharging equipment (P/N GE-48800) will be released as a required replacement for the previously essential ACR2000 (J-43600). This equipment is SAE J2788 compliant and meets GM requirements for A/C Refrigerant System Repairs on all General Motors vehicles, including Hybrid systems with Polyolester (POE) refrigerant oil. This equipment will not be shipped as an essential tool to GM Dealerships. In addition, this equipment is Hybrid compliant and designed to prevent oil cross contamination when servicing Hybrid vehicles with Electric A/C Compressors that use POE refrigerant oil. The ACR2000 (J-43600) will need to be retrofitted with a J-43600-50 (Hose - ACR2000 Oil Flush Loop) to be able to perform Hybrid A/C service work. All Hybrid dealers will receive the J-43600-50, with installation instructions, as a component of the Hybrid essential tool package. Dealerships that do not sell Hybrids, but may need to service Hybrids, can obtain J-43600-50 from SPX Kent Moore. Refer to GM Bulletin 08-01-39-001 for the ACR2000 Hose Flush procedure. The High Voltage (HV) electric A/C compressor used on Two Mode Hybrid vehicles uses a Polyolester (POE) refrigerant oil instead of a Polyalkylene Glycol (PAG) synthetic refrigerant oil. This is due to the better electrical resistance of the POE oil and its ability to provide HV isolation. Failure to flush the hoses before adding refrigerant to a Hybrid vehicle with an electric A/C compressor may result in an unacceptable amount of PAG oil entering the refrigerant system. It may cause a Battery Energy Control Module Hybrid Battery Voltage System Isolation Lost Diagnostic Trouble Code (DTC P1AE7) to be set. Additionally, the A/C system warranty will be voided. Warranty Submission Requirements The Electronically Generated Repair Data (snapshot summary) and printer functions have been eliminated from the GE-48800. The VGA display and temperature probes were eliminated to reduce equipment costs. As a result, effective immediately the 18 digit "Snapshot/Charge Summary" code is no longer required for Air Conditioning (A/C) refrigerant system repairs that are submitted for warranty reimbursement. The charge summary data from before and after system repairs will continue to required, but documented on the repair order only. Both high and low pressures and the recovery and charge amounts should be noted during the repair and entered on the repair order. If using ACR2000 (J-43600), the "Snapshot/Charge Summary" printouts should continue to be attached to the shops copy of the repair order. The labor codes that are affected by this requirement are D3000 through D4500. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Refrigerant > Component Information > Technical Service Bulletins > A/C - Refrigerant Recovery/Recycling/Equipment > Page 2188 Refrigerant: Technical Service Bulletins A/C - Contaminated R134A Refrigerant Bulletin No.: 06-01-39-007 Date: July 25, 2006 INFORMATION Subject: Contaminated R134a Refrigerant Found on Market for Automotive Air-Conditioning Systems Models: 2007 and Prior GM Passenger Cars and Trucks (including Saturn) 2007 and Prior HUMMER H2, H3 2007 and Prior Saab 9-7X Attention: This bulletin should be directed to the Service Manager as well as the Parts Manager. Commercially Available Contaminated R134a Refrigerant Impurities have been found in new commercially available containers of R134a. High levels of contaminates may cause decreased performance, and be detrimental to some air-conditioning components. Accompanying these contaminates has been high levels of moisture. Tip: Excessive moisture may cause system concerns such as orifice tube freeze-up and reduced performance. Industry Reaction: New Industry Purity Standards Due to the potential availability of these lower quality refrigerants, the Society of Automotive Engineers (SAE), and the Air Conditioning and Refrigeration Industry (ARI) are in the process of instituting reliable standards that will be carried on the labels of future R134a refrigerant containers. This identifying symbol will be your assurance of a product that conforms to the minimum standard for OEM Automotive Air-Conditioning use. How Can You Protect Yourself Today? It is recommended to use GM or ACDelco(R) sourced refrigerants for all A/C repair work. These refrigerants meet General Motors own internal standards for quality and purity, insuring that your completed repairs are as good as the way it left the factory. Parts Information The part numbers shown are available through GMSPO or ACDelco(R). The nearest ACDelco(R) distributor in your area can be found by calling 1-800-223-3526 (U.S. Only). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Refrigerant > Component Information > Technical Service Bulletins > A/C - Refrigerant Recovery/Recycling/Equipment > Page 2189 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Refrigerant > Component Information > Technical Service Bulletins > A/C - Refrigerant Recovery/Recycling/Equipment > Page 2190 Refrigerant: Technical Service Bulletins A/C - Refrigerant Recovery/Recharge Equipment File In Section: 01 - HVAC Bulletin No.: 99-01-38-006A Date: May, 2000 WARRANTY ADMINISTRATION Subject: J-43600 ACR 2000 Essential Refrigerant Recovery/Recharge Equipment Models: 1993-2000 Passenger Cars and Light Duty Trucks with R-134a Refrigerant This bulletin is being revised to change the effective date and to update the text. Please discard Corporate Bulletin Number 99-01-38-006 (Section 01 - HVAC). Effective June 1, 2000, the use of J-43600 ACR 2000 will be required on all repairs that require A/C system recovery and are reimbursable by GM. Additionally, GM highly recommends that J-43600 ACR 2000 be used on all GM cars and trucks for customer paid A/C repairs. Important: Also effective June 1, 2000, the "Add" time for all air conditioning recovery is revised to 0.5 hours for front systems and 0.7 hours for front/rear dual systems (RPO C69 or C34). After June 1, 2000, all air conditioning claims submitted with the 0.9 hours "Add" time will be rejected for "labor hours excessive". After the completion of repairs (charging), the ACR 2000 will prompt the user to perform a snapshot of the air conditioning system operating data. The snapshot includes: ^ Maximum high side pressure. ^ Minimum low side pressure. ^ Duct outlet temperatures (2). ^ Refrigerant purity information. This information is captured on a paper printout and in a warranty code. For all GM paid repairs, the paper printout should be attached to the shop copy of the repair order. The warranty code must be submitted in the warranty claim information in the comments field. The code enables the reporting of valuable information about the repair to GM for product quality improvement. Claims submitted without this information may be subject to review and subsequent debit. The required use of J-43600 ACR 2000 raises the question of the acceptable uses for any existing recovery/recycle equipment that GM dealers are currently using. GM recognizes that many of the previously essential ACR4's are reaching the end of their useful life. There are several alternatives for existing equipment that may be considered: ^ Use the existing equipment as customer paid recovery only equipment. Example: Collision repair area. ^ Use the existing equipment as a scavenger unit for contaminated A/C systems. ^ Sell the existing units to repair facilities outside the GM dealer network. ^ Discontinue the use of the existing units if the repair/maintenance costs exceed the value of the equipment. ^ Donate the existing equipment to local technical schools. ^ Dedicate the ACR4 to A/C system flushing, using the J-42939 Flush Adapter. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Refrigerant > Component Information > Technical Service Bulletins > A/C - Refrigerant Recovery/Recycling/Equipment > Page 2191 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Refrigerant > Component Information > Technical Service Bulletins > A/C - Refrigerant Recovery/Recycling/Equipment > Page 2192 Technical Service Bulletin # 631209 Date: 960501 A/C - R12 or R134a Service Recommendations File In Section: 1 - HVAC Bulletin No.: 63-12-09 Date: May, 1996 INFORMATION Subject: Service Issues for Vehicles with R12 or R134a Air Conditioning Systems Models: 1988-96 Passenger Cars and Trucks R12 Service Recommendations As you know, production of R12 refrigerant ceased on December 31, 1995. Although R12 will no longer be manufactured, there is a reserve supply of R12 available. This reserve, along with strict A/C repair service adherence to proper refrigerant recycling procedures, should assure continued availability to meet consumers' needs. R12 can and should continue to be used to service vehicles built with R12 A/C systems as long as it is available. If R12 is no longer available or affordable, a system retrofit utilizing R134a is recommended. R134a IS THE ONLY SUBSTITUTE REFRIGERANT RECOMMENDED BY GM FOR USE IN GM VEHICLE A/C SYSTEMS, AND THEN ONLY AFTER FOLLOWING THE PROPER RETROFIT PROCEDURES FOR THE SPECIFIC MODEL. All new vehicle manufacturers have chosen R134a for retrofit. One of the key reasons is to protect both the service industry and consumers from the high costs that would result from purchasing equipment necessary to service multiple refrigerants. This position also reduces the threat of recycled refrigerant contamination. GM currently offers a simple, low cost R12 to R134a retrofit on many of its late model, front wheel drive passenger cars. Dealers should discuss this capability with owners of these specific models, listed in Retrofit Corporate Bulletin # 43-12-07D, whenever a repair to the A/C refrigerant system is required. Early retrofit of these specific models will aid in prolonging availability of the R12 supply and provide dealer service technicians the opportunity to become more familiar with the proper procedures for performing a retrofit. Remember - R12 and R134a refrigerant are not interchangeable! They cannot be mixed together. In fact, despite the claims of some refrigerant manufacturers, no proposed R12 refrigerant substitute can be added to, mixed with or used to "top off" an R12 system. Under provisions of law covering the service of refrigerants, mixing dissimilar refrigerant products during service is prohibited. To Summarize GM R12 Service Policy 1. Service R12 vehicles with good quality new or recycled R12 as long as it is available. 2. Purchase R12 from a reliable supplier. GMSPO has a supply of high quality R12 available. Dealers are requested to use only R12 supplied by GMSPO for warranty repairs. This high quality refrigerant will insure system performance and avoid the possibility of introducing contaminated material into the customer's A/C system. 3. Carefully test recovered R12 using the PureGuard monitor. On recovery equipment not protected by the PureGuard, always test the recovery cylinder prior to recharging a vehicle A/C system. 4. Discuss the R12 to R134a retrofit option with owners of GM vehicles listed in Retrofit Corporate Bulletin # 43-12-07D. Provide owner with a copy of the pamphlet "Converting Your Auto Air Conditioning System to Use the New Refrigerant". 5. Become familiar with retrofit procedures and exercise care in the handling of dissimilar refrigerants to prevent contamination. R134A Service Recommendations When servicing a previously retrofitted vehicle, there is concern that if all of the R12 is not completely removed prior to the retrofit procedure, it could contaminate your R134a equipment and recovery tank when a subsequent A/C repair is performed. Although the number of retrofits being performed today is minimal, the volume will increase as R12 prices rise. GM Service Technology Group is in the process of field testing a new R134a refrigerant purity tester similar to the PureGuard R12 refrigerant tester you now use. This new tool will mount to your ACR4 R134a Recovery Recycle and Recharge cart and sample all R134a refrigerant prior to recovery. It is expected that testing of this tool will be completed this year. This new tool, the Pureguard 2, will also test vehicles and your recycle tank for air contamination, which is threatening A/C system performance. High levels of air have been found in the recovery tanks on a number of R12 and R134a recovery carts. Air contamination is caused by improper recovery Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Refrigerant > Component Information > Technical Service Bulletins > A/C - Refrigerant Recovery/Recycling/Equipment > Page 2193 procedures and short-cutting refrigerant recycling times. Use the following procedure for testing and correcting air contamination in your A/C service equipment. 1. Make certain that the ACR4 equipment has not been used for at least 12 hours. It is recommended that the equipment be left in an area where the temperature will remain constant overnight to allow the temperature of the refrigerant in the tank to stabilize. 2. Record the surrounding air temperature next to the ACR4 refrigerant tank. Important: A major assumption is that the ambient air temperature next to the tank represents the refrigerant temperature in the tank. Failure to take care in measuring the temperature could result in unnecessary work. 3. Close both liquid (blue) and vapor (red) valves on the ACR4 tank. 4. Disconnect low side (blue) service hose from the back of the ACR4. 5. Slowly disconnect the tank vapor hose (red) from the back of the ACR4 and connect it to the low side service port. 6. Open the vapor (red) valve on the tank and record the tank pressure on the low side gage. 7. Restore hoses to the original position. 8. Referring to the Table, find the ambient temperature measured in Step 2. Compare the pressure reading from Step 6 to the "maximum allowable pressure". If the pressure reading from Step 6 is less than the "maximum allowable pressure", no further action is necessary. Important: The closer the tank pressure is to the desired tank pressure, the better the A/C system will perform. 9. If the pressure reading from Step 6 exceeds the maximum allowable pressure from the Table, open both tank valves and operate the ACR4 through 4 or 5 evacuation cycles. This will activate the automatic air purge to lower the tank pressure. Important: Station should not be connected to vehicle. 10. Repeat the tank pressure checking procedure the next day to determine if the pressure has been reduced to acceptable levels. If the tank pressure has been reduced but is not acceptable, cycle with ACR4 through more evacuation cycles and recheck the next day. Continue process until acceptable pressure is obtained. If the tank pressure is not reduced through the evacuation cycling, then Kent-Moore should be contacted at 1-800-345-2233. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Refrigerant > Component Information > Specifications > Capacity Specifications Refrigerant: Capacity Specifications A/C Refrigerant Capacity 2.25 lb (US) Refrigerant Type Refrigerant-134a Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Refrigerant > Component Information > Specifications > Capacity Specifications > Page 2196 Refrigerant: Fluid Type Specifications A/C Refrigerant Type Refrigerant-134a Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Refrigerant > Component Information > Specifications > Page 2197 Refrigerant: Description and Operation PURPOSE Like the coolant in the engine cooling system, the refrigerant is the substance in the air conditioning system that absorbs, carries, and then releases heat. Although various substances are used as refrigerants in other types of refrigeration systems, some automotive air conditioning systems use a type called Refrigerant-12 (R-12). This vehicle uses Refrigerant-134a (R-134a). It is a non-toxic1 non-flammable, clear, colorless liquefied gas. While the R-134a A/C system is very similar to an, R-12 A/C system, the differences in the refrigerant, lubricants, and service equipment are important. NOTICE:R-134a refrigerant is not compatible with R-12 refrigerant in an air conditioning system. R-12 in a R-134a system will cause compressor failure, refrigerant oil sludge or poor air conditioning system performance. Refrigerant-134a carries a charge of a special lubricant called polyalkaline glycol (PAG) refrigerant oil. GM (PAG) refrigerant oil has a slight blue tint. The oil is hydroscopic (absorbs water from the atmosphere). Store it in closed containers. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Refrigerant Oil > Component Information > Technical Service Bulletins > A/C - New PAG Oil Refrigerant Oil: Technical Service Bulletins A/C - New PAG Oil Bulletin No.: 02-01-39-004B Date: November 16, 2005 INFORMATION Subject: New PAG Oil Released Models: 2006 and Prior GM Passenger Cars and Trucks (Including Saturn) 2003-2006 HUMMER H2 2006 HUMMER H3 2005-2006 Saab 9-7X Built With R-134a Refrigeration System All Air Conditioning Compressor Types (Excluding R4 and A6 Type Compressors) Supercede: This bulletin is being revised to change the PAG oil part number used for R4 and A6 compressors with R-134a refrigerant systems. Please discard Corporate Bulletin Number 02-01-39-004A (Section 01 - HVAC). All General Motors vehicles built with R-134a refrigerant systems shall now be serviced with GM Universal PAG Oil (excluding vehicles equipped with an R4 or A6 compressor). R4 and A6 compressors with R-134a refrigerant systems shall use PAG OIL, GM P/N 12356151 (A/C Delco part number 15-118) (in Canada, use P/N 10953486). Important: The PAG oil referenced in this bulletin is formulated with specific additive packages that meet General Motors specifications and use of another oil may void the A/C systems warranty. Use this new PAG oil when servicing the A/C system on the vehicles listed above. Oil packaged in an 8 oz tube should be installed using A/C Oil Injector, J 45037. Refer to the HVAC Section of Service Information for detailed information on Oil Balancing and Capacities. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Refrigerant Oil > Component Information > Specifications > Capacity Specifications Refrigerant Oil: Capacity Specifications REFRIGERANT OIL DISTRIBUTION The Harrison HT-6 compressor system used on all models requires polyalkaline glycol (PAG) refrigerant oil in the quantities listed below: - Without Aux. A/C - 240 ml (8 fl oz) - With Aux. A/C - 330 ml (11 fl oz) New oil quantities must be added to the system during component replacement and conditions stated as follows: - With no signs of excessive oil leakage, add: A. All Compressors (drain and measure the oil) - If less than 30 ml (1 fl oz) is drained-add 60 ml (2 fl oz) to the new compressor. - If more than 30 ml (1 fl oz) is drained-add same amount that was drained to the new compressor. B. Accumulator-Add 105 ml (3.5 fl oz) of new oil to the replacement accumulator to compensate for oil retained by original accumulator desiccant and bag assemblies. The accumulator should only be replaced if leaking due to a perforation, damaged O-ring seal seat, or damaged threads. C. Evaporator-Add 90 ml (3 fl oz) of new refrigerant oil. D. Condenser-Add 30 ml (1 fl oz) of new refrigerant oil. REFRIGERANT OIL LOSS DUE TO A LARGE LEAK If the refrigerant charge is abruptly lost due to a large refrigerant leak, approximately 90 ml (3 fl oz) of refrigerant oil will be carried out of the system suspended in the refrigerant. Any failure that caused a abrupt refrigerant discharge will experience this oil loss. Failures that allow the refrigerant to seep or bleed off over time do not experience this oil loss. Upon replacement of a component that caused a large refrigerant leak, add 90 ml (3 fl oz) of new polyalkaline glycol (PAG) refrigerant oil plus the desired amount of oil for the particular component. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fluids > Refrigerant Oil > Component Information > Specifications > Capacity Specifications > Page 2204 Refrigerant Oil: Fluid Type Specifications REFRIGERANT OIL TYPE - R-134a PAG (Polyalkaline Glycol) synthetic refrigerant oil (GM Part No. 12345923) or equivalent. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Brake Bleeding > System Information > Service and Repair > Four Wheel Anitlock Brake System Brake Bleeding: Service and Repair Four Wheel Anitlock Brake System Two Person Procedure (Preferred) BLEEDING PROCEDURES Important: Never pump the brake pedal. Fluid cavitation may occur. NOTICE: Gravity and vacuum bleeding are not recommended for this ABS system. Two Person Procedure (Preferred) 1. Raise the vehicle to gain access to the system bleed screws. Install clear tubing on the bleed screws so that air bubbles in the fluid can be seen. 2. Begin by bleeding the system at the right rear wheel, then the left rear, right front and left front. 3. Open one bleed screw at a time 1/2 to 1 full turn. 4. Slowly depress the brake pedal until it reaches its full travel and hold until the bleed screw has been tightened. Release the brake pedal and wait 10-15 seconds for the master cylinder to return to the home position. Important: Repeat steps 1 through 4 until approximately 1 pint of brake fluid has been bled from each wheel. Clean brake fluid should be present at each of the wheel bleed screws. Check the master cylinder fluid level every 4 to 6 strokes of the brake pedal to avoid running the system dry. 5. If any component is replaced which may have caused air to enter the BPMV, use a Scan Tool to run "Function Test" four times while applying the brake pedal firmly. Important: Set the park brake when running the "Function Test." 6. Rebleed all four wheels using steps 1 through 4 to remove the remaining air from the brake system. 7. Evaluate the brake pedal feel before attempting to drive the vehicle and rebleed as many times as necessary to obtain appropriate pedal feel. Pressure Bleeding (Low Pressure) Pressure Bleeding (Low Pressure) 1. Install pressure bleeder per instructions. 2. Install combination valve depressing tool J391 77 if the vehicle is equipped with the metering portion of the combination valve. Remove both dust caps on the combination valve. Install the tool on the end of the combination valve with a brass center pin. 3. Bleed all four wheels beginning at the right rear wheel, then the left rear, right front and left front. Leave the bleed screws open until 1 pint of fluid has been bled out of each wheel. 4. After bleeding all four wheels1 remove the combination valve clip. Use a Scan Tool to run 4 functional tests while applying the brake pedal firmly. 5. Repeat steps 1 through 3 then evaluate the pedal feel. 6. Rebleed the wheels as many times as necessary to obtain good pedal feel before attempting to drive the vehicle. A good bleed will use approximately 2 to 3 quarts of brake fluid. Important: Never reuse brake fluid after it has been bled through a brake system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Brake Bleeding > System Information > Service and Repair > Four Wheel Anitlock Brake System > Page 2209 Brake Bleeding: Service and Repair Master Cylinder Bleeding This procedure can be performed with master cylinder on or off vehicle. 1. Disconnect brake lines at master cylinder, if necessary. 2. Connect suitable lengths of brake lines to master cylinder and immerse other ends of lines in master cylinder reservoirs. 3. Apply master cylinder pushrod or brake pedal with full strokes until air bubbles have disappeared in reservoirs. It may require 20-30 applications to fully eliminate air bubbles. 4. Remove bleeding lines from master cylinder, then install master cylinder on vehicle, if necessary, and connect brake lines. It is not necessary to bleed entire hydraulic system after replacing master cylinder, providing master cylinder has been bled and filled during installation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Brake Bleeding > System Information > Service and Repair > Four Wheel Anitlock Brake System > Page 2210 Brake Bleeding: Service and Repair Bleeding Brake Hydraulic System Pressure Bleeding Pressure Bleeding A diaphragm type pressure bleeder must be used. It must have a rubber diaphragm between the air supply and brake fluid to prevent air, moisture, oil, and other contaminants from entering the hydraulic system. NOTICE: Brake fluid can damage electrical connections and painted surfaces. Use shop cloths, suitable containers, and fender covers to prevent brake fluid from contacting these areas. Always re-seal and wipe off brake fluid containers to prevent spills. Tools Required: Brake Bleeder Adapter J 28434 Wheel Cylinder Bleeder Wrench 1. Fill the pressure tank at least 2,3 full of brake fluid. The bleeder must be bled each time fluid is added. 2. Charge the bleeder to 140 - 170 kPa ( 20-25 psi ). 3. Install the bleeder adapter. 4. If the BPMV of the 4WAL system is replaced or suspected to have air trapped inside, it must be bled next. 5. Bleed each wheel in the following sequence: A. Right rear. B. Left rear. C. Right front. D. Left front. 6. Connect the hose from the bleeder to the adapter at the master cylinder. 7. Open the tank valve. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Brake Bleeding > System Information > Service and Repair > Four Wheel Anitlock Brake System > Page 2211 8. Attach a hose to the bleeder valve. ^ Immerse the opposite end of the hose into a container partially filled with clean brake fluid. 9. Open the bleeder valve at least 3/4 of a turn and allow the fluid to flow until no air is seen in the fluid. 10. Tighten the bleeder valve to 13 Nm ( 110 lb. in. ). 11. Repeat Steps 9 through 11 at all wheels. 12. Check the brake pedal for "sponginess." ^ Repeat the entire bleeding procedure if this condition is found. 13. Disconnect the hose from the bleeder adapter. 14. Remove the bleeder adapter. 15. Fill the master cylinder to the proper level. Manual Bleeding BLEEDING BRAKE HYDRAULIC SYSTEM Bleeding is necessary if air has entered the hydraulic brake system. It may be necessary to bleed the system at all four wheels if a low fluid level allowed the air to enter the system or the brake pipes have been disconnected at the master cylinder or combination valve. If a pipe is disconnected at one wheel, then bleed only that wheel. The time required to bleed the hydraulic system when the master cylinder is removed can be reduced by bench bleeding the master cylinder before installing it on the vehicle. Manual Bleeding If the vehicle is equipped with a vacuum booster, relieve the vacuum reserve by applying the brakes several times with the engine off. NOTICE: Brake fluid will damage electrical connections and painted surfaces. Use shop cloths, suitable containers, and fender covers to prevent the brake fluid from contacting these areas. Always re-seal and wipe off brake fluid containers to prevent spills. Tools Required: J 28434 Wheel Cylinder Bleeder Wrench 1. Fill the master cylinder reservoir with Delco Supreme 11® Hydraulic Brake Fluid GM P/N 1052535 or an equivalent DOT 3 motor vehicle brake fluid. ^ Maintain the fluid level during bleeding. 2. If the master cylinder is suspected to have air in the bore, bleed it before any wheel cylinder or caliper. A. Disconnect the forward brake pipe connection at the master cylinder. B. Allow the brake fluid to flow from the connector port. C. Connect the brake pipe but do not tighten. D. Slowly apply the brake pedal and allow the air to bleed from the loose fitting. E. Tighten the fitting before releasing the pedal. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Brake Bleeding > System Information > Service and Repair > Four Wheel Anitlock Brake System > Page 2212 F. Wait 15 seconds. G. Repeat this sequence, including the 1 5-second wait, until all air is purged from the bore. H. After all air has been removed from the forward connection, repeat this procedure for the rear pipe. 3. If the BPMV of the 4WAL system is replaced or suspected to have air trapped inside, it must be bled next. 4. Bleed each wheel in the following sequence: A. Right rear. B. Left rear. C. Right front D. Left front 5. Attach a hose to the wheel cylinder/caliper bleeder valve. ^ Immerse the opposite end of the hose into a container partially filled with clean brake fluid. 6. Slowly apply the brake pedal one time and hold. 7. Loosen the bleeder valve to purge the air from the wheel cylinder/caliper. 8. Tighten the bleeder valve to 13 Nm ( 110 lb. in. ) and slowly release the pedal. 9. Wait 15 seconds. 10. Repeat this sequence, including the 15-second wait until all air is purged from the wheel cylinder/caliper. 11. Repeat steps 5 through 10 at each wheel until the system is bled. 12. Check the brake pedal for "sponginess" and the brake warning lamp for an indication of unbalanced pressure. Repeat the bleeding procedure to correct either of these conditions. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Air Bag(s) Arming and Disarming > System Information > Service and Repair > Air Bag Disarming and Arming Air Bag(s) Arming and Disarming: Service and Repair Air Bag Disarming and Arming Disabling the SIR System Fig. 1 Air Bag Two-way Connector DRIVER SIDE Many service procedures require the air bag system to be disabled to prevent accidental deployment. The air bag system can maintain sufficient voltage to cause deployment for up to 2 minutes after the ignition switch is turned off, the battery ground cable is disconnected or the DERM fuse is removed. If the inflator module is disconnected from the deployment loop by the following procedure, service can begin immediately without waiting for the 2 minute time period to elapse. 1. Turn steering wheel so that vehicle wheels are pointed straight ahead. 2. Turn ignition switch to Lock position and remove key. 3. Remove air bag fuse from fuse block. 4. Remove steering column filler panel. 5. Remove Connector Position Assurance (CPA) and disconnect yellow two-way connector at base of steering column, Fig. 1. PASSENGER SIDE 1. Remove air bag fuse from fuse block. Enabling the SIR System Driver Side 1. Turn ignition switch to LOCK and remove key. 2. Connect yellow two-way connector and install connector position assurance (CPA). 3. Install steering column filler panel. 4. Insert air bag fuse into fuse block. 5. Turn ignition switch to RUN and verify that the air bag warning lamp flashes seven times then turns off. Passenger Side 1. Turn ignition switch to LOCK and remove key. 2. Insert air bag fuse into fuse block. 3. Turn ignition switch to RUN and verify that the air bag warning lamp flashes seven times then turns off. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Air Bag(s) Arming and Disarming > System Information > Service and Repair > Air Bag Disarming and Arming > Page 2217 Air Bag(s) Arming and Disarming: Service and Repair General Service Precautions CAUTION: When performing service on or around SIR components or SIR wiring, follow the procedures listed below to temporarily disable the SIR system. Failure to follow procedures could result in possible air bag deployment, personal injury or otherwise unneeded SIR system repairs. The DERM can maintain sufficient voltage to cause a deployment for up to 2 minutes after the ignition switch is turned "OFF," the battery is disconnected, or the fuse powering the DERM is removed. Many of the service procedures require removal of the "AIR BAG" fuse, and disconnection of the inflator module from the deployment loop to avoid an accidental deployment. If the inflator module is disconnected from the deployment loop as noted in the "Disabling the SIR System" procedure that follows, service can begin immediately without waiting for the 2 minute time period to expire. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Fuse > Component Information > Technical Service Bulletins > Electrical - Aftermarket Fuse Warning Fuse: Technical Service Bulletins Electrical - Aftermarket Fuse Warning Bulletin No.: 07-08-45-002 Date: September 05, 2007 ADVANCED SERVICE INFORMATION Subject: Service Alert: Concerns With Aftermarket Fuses in GM Vehicles Models: 2008 and Prior GM Passenger Cars and Light Duty Trucks (including Saturn) 2008 and Prior HUMMER H2, H3 2008 and Prior Saab 9-7X Concerns with Harbor Freight Tools "Storehouse" Branded Blade Type Fuses General Motors has become aware of a fuse recall by Harbor Freight Tools/Storehouse for a variety of aftermarket fuses. In two cases, these fuses have not provided protection for the wiring system of the vehicles they were customer installed in. Upon testing the 15 amp version, it was found that the fuse still would not "open" when shorted directly across the battery terminals. How to Identify These Fuses Packed in a 120 piece set, the fuse has a translucent, hard plastic, blue body with the amperage stamped into the top. There are no white painted numbers on the fuse to indicate amperage. There are no identifying marks on the fuse to tell who is making it. The fuses are known to be distributed by Harbor Freight Tools but there may be other marketers, and packaging of this style of fuse. It would be prudent to replace these fuses if found in a customers vehicle. Likewise, if wiring overheating is found you should check the fuse panel for the presence of this style of fuse. All GM dealers should use genuine GM fuses on the vehicles they service. You should also encourage the use of GM fuses to your customers to assure they are getting the required electrical system protection. GM has no knowledge of any concerns with other aftermarket fuses. If additional information becomes available, this bulletin will be updated. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Fuse > Component Information > Technical Service Bulletins > Page 2223 Instrument Panel Wiring, LH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Fuse > Component Information > Application and ID > I/P Fuse Block Fuse: Application and ID I/P Fuse Block I/P Fuse Block (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Fuse > Component Information > Application and ID > I/P Fuse Block > Page 2226 I/P Fuse Block (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Fuse > Component Information > Application and ID > I/P Fuse Block > Page 2227 Fuse: Application and ID Convenience Center Convenience Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Fuse > Component Information > Application and ID > I/P Fuse Block > Page 2228 Convenience Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Fuse > Component Information > Application and ID > I/P Fuse Block > Page 2229 Fuse: Application and ID Underhood Fuse/Relay Center Underhood Fuse-Relay Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Fuse > Component Information > Application and ID > I/P Fuse Block > Page 2230 Underhood Fuse-Relay Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Fuse Block > Component Information > Locations > Convenience Center Fuse Block: Locations Convenience Center Convenience Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Fuse Block > Component Information > Locations > Convenience Center > Page 2235 Instrument Panel Wiring, LH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Fuse Block > Component Information > Locations > Convenience Center > Page 2236 Underhood Fuse-Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Fuse Block > Component Information > Locations > Page 2237 C210: Cross Body HARN To Convenience Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Fuse Block > Component Information > Application and ID > I/P Fuse Block Fuse Block: Application and ID I/P Fuse Block I/P Fuse Block (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Fuse Block > Component Information > Application and ID > I/P Fuse Block > Page 2240 I/P Fuse Block (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Fuse Block > Component Information > Application and ID > I/P Fuse Block > Page 2241 Fuse Block: Application and ID Underhood Fuse/Relay Center Underhood Fuse-Relay Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Fuse Block > Component Information > Application and ID > I/P Fuse Block > Page 2242 Underhood Fuse-Relay Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Fuse Block > Component Information > Application and ID > I/P Fuse Block > Page 2243 Fuse Block: Application and ID Convenience Center Convenience Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Fuse Block > Component Information > Application and ID > I/P Fuse Block > Page 2244 Convenience Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Relay Box > Component Information > Technical Service Bulletins > Electrical - Revised Convenience Center Cavity ID Relay Box: Technical Service Bulletins Electrical - Revised Convenience Center Cavity ID File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-82-08 Date: August, 1997 SERVICE MANUAL UPDATE Subject: Section 8A-11 Fuse Block Details Revised Convenience Center Table Models: 1996-98 Chevrolet and GMC C/K models. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Relay Box > Component Information > Technical Service Bulletins > Electrical - Revised Convenience Center Cavity ID > Page 2249 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Relay Box > Component Information > Technical Service Bulletins > Electrical - Revised Convenience Center Cavity ID > Page 2250 This bulletin revises "Convenience Center" table on Page 8A-11-5, 6 in the 1996 C/K Service Manual, Page 8A-11-6, 7 in the 1997 C/K Service Manual, and Page 8A-11-5 in the 1998 C/K Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Relay Box > Component Information > Technical Service Bulletins > Page 2251 Underhood Fuse-Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Relay Box > Component Information > Technical Service Bulletins > Page 2252 Relay Box: Application and ID Underhood Fuse-Relay Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Fuses and Circuit Breakers > Relay Box > Component Information > Technical Service Bulletins > Page 2253 Underhood Fuse-Relay Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Service Reminder Indicators > Coolant Level Indicator Lamp > Component Information > Diagrams Low Coolant Level Indicator Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Service Reminder Indicators > Coolant Level Indicator Lamp > Component Information > Diagrams > Page 2258 Coolant Level Indicator Lamp: Description and Operation This system uses a sensor mounted on the radiator and an indicator light mounted in the instrument panel to warn the driver if coolant level is too low. This light is wired in series with the ignition switch, ECM and the sensor. When the ignition switch is turned to the crank position, the circuit is energized and the indicator light will illuminate. When the ignition switch is turned to the ON position and coolant level is sufficient, the sensor will indicate this to the ECM and the light will turn off. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Service Reminder Indicators > Coolant Level Indicator Lamp > Component Information > Testing and Inspection > Indicator Lamp Remains Illuminated Coolant Level Indicator Lamp: Testing and Inspection Indicator Lamp Remains Illuminated 1. Turn ignition switch to the On position, then check coolant level and add coolant as necessary. If lamp remains illuminated, proceed to step 2. 2. Disconnect electrical connector at the sensor. If lamp does not illuminate replace the sensor. If lamp remains illuminated, proceed to step 3. 3. Connect electrical lead to the sensor and check for an open circuit between the sensor and the module. Repair or replace as necessary. If circuit is satisfactory, replace the ECM. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Service Reminder Indicators > Coolant Level Indicator Lamp > Component Information > Testing and Inspection > Indicator Lamp Remains Illuminated > Page 2261 Coolant Level Indicator Lamp: Testing and Inspection Indicator Lamp Will Not Illuminate 1. Turn ignition switch to the crank position, and proceed as follows: a. If lamp illuminates, lamp is satisfactory and connector is properly installed. Proceed to step 2. b. If lamp does not illuminate, check bulb, socket and wiring between socket and module connector. Replace or repair as necessary. 2. Turn ignition switch to the On position and disconnect electrical lead at coolant level sensor mounted on the radiator. If lamp fails to illuminate, check wiring between coolant level sensor connector and ECM for a short circuit to ground. If circuit is satisfactory, replace the ECM. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Service Reminder Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition Malfunction Indicator Lamp: Customer Interest PROM - MIL ON, Poor Driveability Condition File In Section: 6E - Engine Fuel & Emission Bulletin No.: 76-65-04 Date: March, 1997 Subject: Malfunction Indicator Light (MIL) On, Poor Driveability Conditions (Perform Flash Calibration) Models: 1996-97 Chevrolet and GMC Light Duty Trucks 1996-97 Chevrolet Tiltmaster and GMC Forward W4 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L Engines (VINs X, W, M, R RPOs LF6, L35, L3O, L31) Condition An owner of the above mentioned vehicles may report that the Malfunction Indicator Light (MIL) is on and/or the vehicle has one or more of the following driveability conditions. 1. 5.7L (L31) only: Surge or chuggle at speeds of 42 to 65 MPH while at steady speed or under light to moderate acceleration with the TCC applied. 2. MIL on with DTC P0172 or P0175 stored but no reported driveability symptoms. 3. MIL on with TDC P1406 stored and rough engine or poor driveability symptoms. 4. When operating at altitudes above 5,000 feet, an audible spark knock noise is heard. 5. Hesitation and/or misfire during light cruise conditions due to ignition cross-fire with no DTC stored. This will only occur on V-6 engines with cam retard offset in excess of 26° and V-8's with cam retard offset in excess of 15°. 6. The MIL may be on and a DTC stored for an engine misfire but no misfire occurred. 7. Engine exhibits an idle speed surge or roll. 1996 Models Only 8. MIL on with DTC P0102 stored but no reported driveability symptoms. 9. 5.0L (L30) & 5.7L (L31) only: Difficult starting in extreme cold (below 0° F) conditions. 10. 5.7L (L31) only: Poorer than expected fuel economy when heavily loaded. 1997 Models Only 11. MIL on with DTC P0121 stored but no reported driveability symptoms. 12. C/K & S/T Models with either V-6 engine and manual transmission: An engine flare between shifts may be noted when the engine is cold. 13. Either V-6 engine and manual transmission: An engine flare between shifts may be noted when the engine is cold. 14. C/K, S/T and M/L Models equipped with L35 V-6 engine, an improvement to the vapor canister purge diagnostics is incorporated into the new calibrations so that the Tech II can turn on canister purge at idle speed. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Service Reminder Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 2270 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Service Reminder Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 2271 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Service Reminder Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 2272 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Service Reminder Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 2273 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Service Reminder Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 2274 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Service Reminder Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 2275 Follow the Strategy Based Diagnostic Steps for the customer's reported symptoms. If diagnosis does not reveal a cause, refer to the tables below for the applicable calibration change. Perform programming per the latest Techline information for programming procedures. Important The calibrations listed are FLASH calibrations and are not available from GMSPO. They are available on 1997 Techline CD Disc 5 and later. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J-6355 Use Published Labor Operation Time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Service Reminder Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition Malfunction Indicator Lamp: All Technical Service Bulletins PROM - MIL ON, Poor Driveability Condition File In Section: 6E - Engine Fuel & Emission Bulletin No.: 76-65-04 Date: March, 1997 Subject: Malfunction Indicator Light (MIL) On, Poor Driveability Conditions (Perform Flash Calibration) Models: 1996-97 Chevrolet and GMC Light Duty Trucks 1996-97 Chevrolet Tiltmaster and GMC Forward W4 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L Engines (VINs X, W, M, R RPOs LF6, L35, L3O, L31) Condition An owner of the above mentioned vehicles may report that the Malfunction Indicator Light (MIL) is on and/or the vehicle has one or more of the following driveability conditions. 1. 5.7L (L31) only: Surge or chuggle at speeds of 42 to 65 MPH while at steady speed or under light to moderate acceleration with the TCC applied. 2. MIL on with DTC P0172 or P0175 stored but no reported driveability symptoms. 3. MIL on with TDC P1406 stored and rough engine or poor driveability symptoms. 4. When operating at altitudes above 5,000 feet, an audible spark knock noise is heard. 5. Hesitation and/or misfire during light cruise conditions due to ignition cross-fire with no DTC stored. This will only occur on V-6 engines with cam retard offset in excess of 26° and V-8's with cam retard offset in excess of 15°. 6. The MIL may be on and a DTC stored for an engine misfire but no misfire occurred. 7. Engine exhibits an idle speed surge or roll. 1996 Models Only 8. MIL on with DTC P0102 stored but no reported driveability symptoms. 9. 5.0L (L30) & 5.7L (L31) only: Difficult starting in extreme cold (below 0° F) conditions. 10. 5.7L (L31) only: Poorer than expected fuel economy when heavily loaded. 1997 Models Only 11. MIL on with DTC P0121 stored but no reported driveability symptoms. 12. C/K & S/T Models with either V-6 engine and manual transmission: An engine flare between shifts may be noted when the engine is cold. 13. Either V-6 engine and manual transmission: An engine flare between shifts may be noted when the engine is cold. 14. C/K, S/T and M/L Models equipped with L35 V-6 engine, an improvement to the vapor canister purge diagnostics is incorporated into the new calibrations so that the Tech II can turn on canister purge at idle speed. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Service Reminder Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 2281 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Service Reminder Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 2282 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Service Reminder Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 2283 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Service Reminder Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 2284 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Service Reminder Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 2285 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Service Reminder Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 2286 Follow the Strategy Based Diagnostic Steps for the customer's reported symptoms. If diagnosis does not reveal a cause, refer to the tables below for the applicable calibration change. Perform programming per the latest Techline information for programming procedures. Important The calibrations listed are FLASH calibrations and are not available from GMSPO. They are available on 1997 Techline CD Disc 5 and later. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J-6355 Use Published Labor Operation Time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Service Reminder Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Page 2287 Malfunction Indicator Lamp: Service and Repair The CHECK ENGINE LAMP will be illuminated when the ignition switch is placed in the "ON" position. When the engine is started, the lamp should turn "OFF". If the lamp remains "ON" for 10 seconds or constantly after the engine is started, the self diagnosis system has detected a problem and has stored a code in the system Control Module. After diagnosis and repair, the ECM memory can be cleared of codes by removing the Control Module fuse or disconnecting the battery ground cable for approximately 30 seconds, with ignition switch in the "OFF" position. NOTE If battery ground cable is disconnected to clear codes, components such as clocks, electronically tuned radios etc., will have to be reset. - It is a good idea to record preset radio stations before disconnecting the negative battery cable. This will allow the stations to be reset as to not inconvenience the customer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Vehicle Lifting > Component Information > Service and Repair Vehicle Lifting: Service and Repair Fig. 12 Vehicle Lift Points. Fig. 12 Vehicle Lift Points. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Wheels/Tires - Use of Nitrogen Gas in Tires Tires: Technical Service Bulletins Wheels/Tires - Use of Nitrogen Gas in Tires INFORMATION Bulletin No.: 05-03-10-020C Date: April 27, 2010 Subject: Use of Nitrogen Gas in Tires Models: 2011 and Prior GM Passenger Cars and Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 05-03-10-020B (Section 03 - Suspension). GM's Position on the Use of Nitrogen Gas in Tires General Motors does not oppose the use of purified nitrogen as an inflation gas for tires. We expect the theoretical benefits to be reduced in practical use due to the lack of an existing infrastructure to continuously facilitate inflating tires with nearly pure nitrogen. Even occasional inflation with compressed atmospheric air will negate many of the theoretical benefits. Given those theoretical benefits, practical limitations, and the robust design of GM original equipment TPC tires, the realized benefits to our customer of inflating their tires with purified nitrogen are expected to be minimal. The Promise of Nitrogen: Under Controlled Conditions Recently, nitrogen gas (for use in inflating tires) has become available to the general consumer through some retailers. The use of nitrogen gas to inflate tires is a technology used in automobile racing. The following benefits under controlled conditions are attributed to nitrogen gas and its unique properties: - A reduction in the expected loss of Tire Pressure over time. - A reduction in the variance of Tire Pressures with temperature changes due to reduction of water vapor concentration. - A reduction of long term rubber degradation due to a decrease in oxygen concentrations. Important These are obtainable performance improvements when relatively pure nitrogen gas is used to inflate tires under controlled conditions. The Promise of Nitrogen: Real World Use Nitrogen inflation can provide some benefit by reducing gas migration (pressure loss) at the molecular level through the tire structure. NHTSA (National Highway Traffic Safety Administration) has stated that the inflation pressure loss of tires can be up to 5% a month. Nitrogen molecules are larger than oxygen molecules and, therefore, are less prone to "seeping" through the tire casing. The actual obtainable benefits of nitrogen vary, based on the physical construction and the materials used in the manufacturing of the tire being inflated. Another potential benefit of nitrogen is the reduced oxidation of tire components. Research has demonstrated that oxygen consumed in the oxidation process of the tire primarily comes from the inflation media. Therefore, it is reasonable to assume that oxidation of tire components can be reduced if the tire is inflated with pure nitrogen. However, only very small amounts of oxygen are required to begin the normal oxidation process. Even slight contamination of the tire inflation gas with compressed atmospheric air during normal inflation pressure maintenance, may negate the benefits of using nitrogen. GM Tire Quality, Technology and Focus of Importance Since 1972, General Motors has designed tires under the TPC (Tire Performance Criteria) specification system, which includes specific requirements that ensure robust tire performance under normal usage. General Motors works with tire suppliers to design and manufacture original equipment tires for GM vehicles. The GM TPC addresses required performance with respect to both inflation pressure retention, and endurance properties for original equipment tires. The inflation pressure retention requirements address availability of oxygen and oxidation concerns, while endurance requirements ensure the mechanical structure of the tire has sufficient strength. This combination has provided our customers with tires that maintain their structural integrity throughout their useful treadlife under normal operating conditions. Regardless of the inflation media for tires (atmospheric air or nitrogen), inflation pressure maintenance of tires is critical for overall tire, and ultimately, vehicle performance. Maintaining the correct inflation pressure allows the tire to perform as intended by the vehicle manufacturer in many areas, including comfort, fuel economy, stopping distance, cornering, traction, treadwear, and noise. Since the load carrying capability of a tire is related to inflation pressure, proper inflation pressure maintenance is necessary for the tire to support the load imposed by the vehicle without excessive structural Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Wheels/Tires - Use of Nitrogen Gas in Tires > Page 2296 degradation. Important Regardless of the inflation media for tires (atmospheric air or nitrogen), inflation pressure maintenance of tires is critical for overall tire, and ultimately, vehicle performance. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 04-03-10-001F > Apr > 10 > Tires/Wheels - Tire Puncture Repair Procedures Tires: Technical Service Bulletins Tires/Wheels - Tire Puncture Repair Procedures INFORMATION Bulletin No.: 04-03-10-001F Date: April 27, 2010 Subject: Tire Puncture Repair Procedures For All Cars and Light Duty Trucks Models: 2011 and Prior GM Passenger Cars and Light Duty Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 04-03-10-001E (Section 03 - Suspension). This bulletin covers puncture repair procedures for passenger car and light duty truck radial tires in the tread area only. The tire manufacturer must be contacted for its individual repair policy and whether or not the speed rating is retained after repair. Caution - Tire changing can be dangerous and should be done by trained professionals using proper tools and procedures. Always read and understand any manufacturer's warnings contained in their customers literature or molded into the tire sidewall. - Serious eye and ear injury may result from not wearing adequate eye and ear protection while repairing tires. - NEVER inflate beyond 275 kPa (40 pounds) pressure to seat beads. Some run flat tires, such as the Goodyear Extended Mobility Tire (EMT) used on the Corvette, may require more than 275 kPa (40 psi) to seat the bead. In such a case, a tire safety cage must be used. Consult the tire manufacturer for its individual repair policy. - NEVER stand, lean or reach over the assembly during inflation. Repairable area on a radial tire. Important - NEVER repair tires worn to the tread indicators 1.59 mm (2/32") remaining depth). - NEVER repair tires with a tread puncture larger than 6.35 mm (1/4"). - NEVER substitute an inner tube for a permissible or non-permissible repair. - NEVER perform an outside-in tire repair (plug only, on the wheel). - Every tire must be removed from the wheel for proper inspection and repair. - Regardless of the type of repair used, the repair must seal the inner liner and fill the injury. - Consult with repair material supplier/manufacturer for repair unit application procedures and repair tools/repair material recommendations. Three basic steps for tire puncture repair: 1. Remove the tire from the wheel for inspection and repair. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 04-03-10-001F > Apr > 10 > Tires/Wheels - Tire Puncture Repair Procedures > Page 2302 2. Fill the injury (puncture) to keep moisture out. 3. Seal the inner liner with a repair unit to prevent air loss. External Inspection 1. Prior to demounting, inspect the tire surface, the valve and the wheel for the source of the leak by using a water and soap solution. Mark the injured area and totally deflate the tire by removing the valve core. 2. Demount the tire from the wheel and place the tire on a well-lighted spreader. Internal Inspection 1. Spread the beads and mark the puncture with a tire crayon. 2. Inspect the inner tire for any signs of internal damage. 3. Remove the puncturing object, noting the direction of the penetration. 4. Probe the injury with a blunt awl in order to determine the extent and direction of the injury. 5. Remove any loose foreign material from the injury. 6. Punctures exceeding 6.35 mm (1/4") should not be repaired. Cleaning 1. Clean the area around the puncture thoroughly with a proper liner cleaner, clean cloth and a scraper. This step serves to remove dirt and mold lubricants to insure proper adhesion and non-contamination of the buffing tool. 2. Refer to information on the product or manufacturer's Material Safety Data Sheet and follow guidelines for handling and disposal. Clean the Injury Channel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 04-03-10-001F > Apr > 10 > Tires/Wheels - Tire Puncture Repair Procedures > Page 2303 1. Use a proper hand reamer, carbide cutter or drill bit to ream the puncture channel from the inside of the tire in order to clean the injury. 2. Remove steel wires protruding above the liner surface to prevent damage to the repair unit. 3. Consult your repair material supplier for recommended reaming tool(s). Fill the Injury 1. It is necessary to fill the injury channel to provide back up for the repair unit and to prevent moisture from entering the tire fabric and steel wires. 2. (For combination repair/plug units skip this step.) Cement the injured channel and fill the injury from the inside of the tire with the repair plug per repair material manufacturer's recommendations. Without stretching the plug, cut the plug off just above the inside tire surface. 3. Consult your repair material supplier for proper repair material selection. Repair Unit Selection Important Do not install the repair unit in this step. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 04-03-10-001F > Apr > 10 > Tires/Wheels - Tire Puncture Repair Procedures > Page 2304 1. Center the repair unit over the injury as a reference and outline an area larger than the unit so that buffing will not remove the crayon marks. 2. Remove the repair unit. 3. DO NOT overlap previous or multiple repair units. 4. Consult your repair material supplier for proper repair unit selection. Buffing 1. To prevent contamination and preserve the outline, buff within the marked area thoroughly and evenly with a low speed buffing tool using a fine wire brush or gritted rasp. 2. Buff to a smooth velvet surface (RMA #1 or #2 buffed texture). 3. Use caution not to gouge the inner liner or expose casing fabric. 4. Remove any buffing dust with a vacuum cleaner. 5. Consult your repair material supplier for a proper buffing tool. Cementing Apply chemical cement according to the repair material manufacturer's procedures. Repair Unit Application Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 04-03-10-001F > Apr > 10 > Tires/Wheels - Tire Puncture Repair Procedures > Page 2305 1. The tire must be in the relaxed position when the repair unit is installed (Do not spread the beads excessively). Two-Piece Plug and Repair Units 1. If applicable, install the repair unit so that the alignment is correct. 2. Center the repair unit over the injury and stitch down thoroughly with the stitching tool, working from the center out. 3. Being careful not to stretch the plug material, cut the plug flush with the outer tread. Combination Repair/Plug Units 1. Pull the plug through the injury until the repair just reaches the liner. Stitch down thoroughly. 2. Follow the repair material manufacturer's recommendations for further installation instructions. 2. Consult your repair material supplier for the proper stitching tool. Safety Cage Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 04-03-10-001F > Apr > 10 > Tires/Wheels - Tire Puncture Repair Procedures > Page 2306 Some run flat tires, such as the Goodyear Extended Mobility Tire (EMT) used on the Corvette, may require more than 275 kPa (40 psi) to seat the bead. In such a case, a tire safety cage must be used. Consult the tire manufacturer for its individual repair policy. Final Inspection 1. After remounting and inflating the tire, check both beads, the repair and the valve with a water and soap solution in order to detect leaks. 2. If the tire continues to lose air, the tire must be demounted and reinspected. 3. Balance the tire and wheel assembly. Refer to Tire and Wheel Assembly Balancing - OFF Vehicle. For additional tire puncture repair information, contact: Rubber Manufacturers Association (RMA) Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 05-03-10-020C > Apr > 10 > Wheels/Tires - Use of Nitrogen Gas in Tires Tires: Technical Service Bulletins Wheels/Tires - Use of Nitrogen Gas in Tires INFORMATION Bulletin No.: 05-03-10-020C Date: April 27, 2010 Subject: Use of Nitrogen Gas in Tires Models: 2011 and Prior GM Passenger Cars and Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 05-03-10-020B (Section 03 - Suspension). GM's Position on the Use of Nitrogen Gas in Tires General Motors does not oppose the use of purified nitrogen as an inflation gas for tires. We expect the theoretical benefits to be reduced in practical use due to the lack of an existing infrastructure to continuously facilitate inflating tires with nearly pure nitrogen. Even occasional inflation with compressed atmospheric air will negate many of the theoretical benefits. Given those theoretical benefits, practical limitations, and the robust design of GM original equipment TPC tires, the realized benefits to our customer of inflating their tires with purified nitrogen are expected to be minimal. The Promise of Nitrogen: Under Controlled Conditions Recently, nitrogen gas (for use in inflating tires) has become available to the general consumer through some retailers. The use of nitrogen gas to inflate tires is a technology used in automobile racing. The following benefits under controlled conditions are attributed to nitrogen gas and its unique properties: - A reduction in the expected loss of Tire Pressure over time. - A reduction in the variance of Tire Pressures with temperature changes due to reduction of water vapor concentration. - A reduction of long term rubber degradation due to a decrease in oxygen concentrations. Important These are obtainable performance improvements when relatively pure nitrogen gas is used to inflate tires under controlled conditions. The Promise of Nitrogen: Real World Use Nitrogen inflation can provide some benefit by reducing gas migration (pressure loss) at the molecular level through the tire structure. NHTSA (National Highway Traffic Safety Administration) has stated that the inflation pressure loss of tires can be up to 5% a month. Nitrogen molecules are larger than oxygen molecules and, therefore, are less prone to "seeping" through the tire casing. The actual obtainable benefits of nitrogen vary, based on the physical construction and the materials used in the manufacturing of the tire being inflated. Another potential benefit of nitrogen is the reduced oxidation of tire components. Research has demonstrated that oxygen consumed in the oxidation process of the tire primarily comes from the inflation media. Therefore, it is reasonable to assume that oxidation of tire components can be reduced if the tire is inflated with pure nitrogen. However, only very small amounts of oxygen are required to begin the normal oxidation process. Even slight contamination of the tire inflation gas with compressed atmospheric air during normal inflation pressure maintenance, may negate the benefits of using nitrogen. GM Tire Quality, Technology and Focus of Importance Since 1972, General Motors has designed tires under the TPC (Tire Performance Criteria) specification system, which includes specific requirements that ensure robust tire performance under normal usage. General Motors works with tire suppliers to design and manufacture original equipment tires for GM vehicles. The GM TPC addresses required performance with respect to both inflation pressure retention, and endurance properties for original equipment tires. The inflation pressure retention requirements address availability of oxygen and oxidation concerns, while endurance requirements ensure the mechanical structure of the tire has sufficient strength. This combination has provided our customers with tires that maintain their structural integrity throughout their useful treadlife under normal operating conditions. Regardless of the inflation media for tires (atmospheric air or nitrogen), inflation pressure maintenance of tires is critical for overall tire, and ultimately, vehicle performance. Maintaining the correct inflation pressure allows the tire to perform as intended by the vehicle manufacturer in many areas, including comfort, fuel economy, stopping distance, cornering, traction, treadwear, and noise. Since the load carrying capability of a tire is related to inflation pressure, proper inflation pressure maintenance is necessary for the tire to support the load imposed by the vehicle without excessive structural Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 05-03-10-020C > Apr > 10 > Wheels/Tires - Use of Nitrogen Gas in Tires > Page 2311 degradation. Important Regardless of the inflation media for tires (atmospheric air or nitrogen), inflation pressure maintenance of tires is critical for overall tire, and ultimately, vehicle performance. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 00-00-90-002J > Jan > 09 > Tires - Correct Inflation Pressure Information Tires: Technical Service Bulletins Tires - Correct Inflation Pressure Information INFORMATION Bulletin No.: 00-00-90-002J Date: January 28, 2009 Subject: Information on Proper Tire Pressure Models: 2010 and Prior GM Passenger Cars and Light Duty Trucks (including Saturn) 2009 and Prior HUMMER H2, H3, H3T 2005-2009 Saab 9-7X Supercede: This bulletin is being revised to add model years and clarify additional information. Please discard Corporate Bulletin Number 00-00-90-002I (Section 00 - General Information). Important: ^ Adjustment of tire pressure for a customer with a Low Tire Pressure Monitor (TPM) light on and no codes in the TPM system is NOT a warrantable repair. Claims to simply adjust the tire pressure will be rejected. ^ ALL tires (including the spare tire) MUST be set to the recommended inflation pressure stated on the vehicle's tire placard (on driver's door) during the PRE-DELIVERY INSPECTION (PDI). Recommended inflation pressure is not the pressure printed on tire sidewall. ^ Tires may be over-inflated from the assembly plant due to the mounting process. ^ Generally a 5.6°C (10°F) temperature change will result in (is equivalent to) a 6.9 kPa (1 psi) tire pressure change. ^ 2008-2009 HUMMER H2 Only - The H2 comes standard with Light Truck "D" Load Range tires with a recommended cold inflation pressure of 289 kPa (42 psi). These tires will alert the driver to a low pressure situation at roughly 262 kPa (38 psi) due to a requirement in FMVSS 138 which specifies a Minimum Activation Pressure for each tire type. This creates a relatively narrow window of "usable" pressure values and the warning will be more sensitive to outside temperature changes during the colder months. As with other cold temperature/tire pressure issues, there is nothing wrong with the system itself. If a vehicle is brought in with this concern, check for tire damage and set all tires to the Recommended Cold Inflation Pressure shown on the vehicle placard. Accurate tire pressures ensure the safe handling and appropriate ride characteristics of GM cars and trucks. It is critical that the tire pressure be adjusted to the specifications on the vehicle¡C■s tire placard during PDI. Ride, handling and road noise concerns may be caused by improperly adjusted tire pressure. The first step in the diagnosis of these concerns is to verify that the tires are inflated to the correct pressures. The recommended tire inflation pressure is listed on the vehicle¡C■s tire placard. The tire placard is located on the driver¡C■s side front or rear door edge, center pillar, or the rear compartment lid. Tip ^ Generally a 5.6°C (10°F) temperature increase will result in (is equivalent to) a 6.9 kPa (1 psi) tire pressure increase. ^ The definition of a "cold" tire is one that has been sitting for at least 3 hours, or driven no more than 1.6 km (1 mi). ^ On extremely cold days, if the vehicle has been indoors, it may be necessary to compensate for the low external temperature by adding additional air to the tire during PDI. ^ During cold weather, the Tire Pressure Monitor (TPM) indicator light (a yellow horseshoe with an exclamation point) may illuminate. If this indicator turns off after the tires warm up (reach operating temperature), the tire pressure should be reset to placard pressure at the cold temperature. ^ The TPM system will work correctly with nitrogen in tires. ^ The TPM system is compatible with the GM Vehicle Care Tire Sealant but may not be with other commercially available sealants. Important: ^ Do not use the tire pressure indicated on the tire itself as a guide. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 00-00-90-002J > Jan > 09 > Tires - Correct Inflation Pressure Information > Page 2316 ^ Always inspect and adjust the pressure when the tires are cold. ^ Vehicles that have different pressures for the front and the rear need to be adjusted after tire rotation. Improper tire inflation may result in any or all of the following conditions: ^ Premature tire wear ^ Harsh ride ^ Excessive road noise ^ Poor handling ^ Reduced fuel economy ^ Low Tire Pressure Monitor (TPM) Light ON ^ Low Tire Pressure Message on the Drivers Information Center (DIC) Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 01-03-10-011 > Dec > 01 > Tires - Sidewall Damage Tires: Technical Service Bulletins Tires - Sidewall Damage File In Section: 03 Suspension Bulletin No.: 01-03-10-011 Date: December, 2001 INFORMATION Subject: Tire Sidewall Damage Models: 2002 and Prior Passenger Cars and Light Duty Trucks Inspection of a number of tires returned to the Warranty Parts Center and the various tire manufacturers has revealed gouges and/or abrasions that are located on the tire's outboard sidewall. Typically, these gouges and/or abrasions appear to be located near where the tire was marked for wheel balance weight installation at the vehicle assembly plant. It has been determined that this type of surface damage to the tire may be the result of dealers or owners using a high pressure power washer to remove wax/paint/ink marks from the tire sidewall. Do not use a high pressure power washer on tires. To remove any markings from the tire's sidewall, only use soap water and a scrub brush. This type of tire sidewall damage should not be considered as a warrantable condition. DISCLAIMER Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 00-03-10-003B > May > 01 > Tires - Bumper To Bumper Warranty Coverage Tires: Technical Service Bulletins Tires - Bumper To Bumper Warranty Coverage File In Section: 03 - Suspension Bulletin No.: 00-03-10-003B Date: May, 2001 WARRANTY ADMINISTRATION Subject: GM Tire Warranty for Bumper-to-Bumper Program Models: 1996-2001 Passenger Cars and Light Duty Trucks Attention: "GM of Canada" and "IPC" dealers are not authorized to utilize this service bulletin. This bulletin is being revised to include information on the new GM Global Tire Warranty & Claims (GTWC) website for preparing the GM Tire Requisition & Return Document for tires being replaced under the Bumper-to-Bumper New Vehicle Limited Warranty Program. Please discard Corporate Bulletin Number 00-03-10-003A (Section 03 - Suspension) Since the 1996 model year, original equipment manufactured (OEM) tires on all GM passenger cars and light duty trucks are covered under the Bumper-to-Bumper time and mileage provisions of the GM New Vehicle Limited Warranty. Saturn began such coverage with the 2001 model year. Tire warranty coverage allows the customer to have all warranty needs, including tires, addressed at one location - a GM dealership. Although GM dealers are not required to inventory tires to administer this warranty coverage, some dealers may choose to do so. What Is Covered Only OEM tires are covered against defects in material and workmanship. OEM tires will always have a Tire Performance Criteria (TPC) number molded on the sidewall near the tire size. (Exceptions: Prizm and some Tracker models do not use TPC tires, but are still covered.) Any replaced tire will continue to be covered for the remaining portion of the New Vehicle Warranty. Tires will be warranted without prorated charges for tread mileage. Following expiration of GM's coverage, tires may continue to be warranted, on a pro-rated basis, by the tire manufacturer. Review the tire manufacturer's booklet (included as part of the glove box material). What Is Not Covered ^ Non-original equipment tires (those without a TPC number molded on the sidewall except Prizm and Tracker) are not covered. ^ Normal tire wear and wear out is not covered. ^ Road hazard is not covered. This includes punctures, cuts, impact breaks, etc. Road hazard is covered by the tire manufacturer on sealant and EMT (run flat) tires. ^ Damage due to misuse, negligence, lack of maintenance, alteration, racing and vandalism is not covered. Global Tire Warranty & Claims Website Effective May 14, 2001, GM dealers will be required to use the Global Tire Warranty & Claims (GTWC) website to electronically initiate the Tire Requisition & Return Document needed to obtain replacement tires. All previous paper copy versions of this document should be discarded. The GTWC website is a secured, encrypted, password-protected tool designed to allow GM to collect and monitor data on tires being replaced on all GM vehicles, providing an early warning for any concerns. The website will provide a more efficient, faster and error-free procedure for preparing the GM Tire Requisition & Return Document. The electronic Tire Requisition & Return Document requires one form per tire, not one form per vehicle, as in the past. This web form is designed to automatically fill data fields and provides many drop-down menu selections to minimize user effort. It also has additional data requirements on types of adjustments and has a monitoring system for the return of tires to the tire manufacturer for inspection. GM dealers will need to print copies of the completed web form to get replacement tires from the local tire dealer and to return the removed tire(s) to the tire manufacturer for inspection. Once the removed tire has been returned and inspected, the tire manufacturer will also use the GTWC web system to complete the form initiated by the GM dealer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 00-03-10-003B > May > 01 > Tires - Bumper To Bumper Warranty Coverage > Page 2325 Initiating a Tire Requisition & Return Document Online Users may access the system using any PC with an Internet connection through the GM ACCESS hyperlink or preferably using a local Internet Service Provider (ISP). The minimum browser version required is Netscape 4.5 or Internet Explorer 4.0 or higher. The GM ACCESS server has an outdated web browser and cannot be used to access this website. Please use a client PC with the appropriate level of browser. 1. From a Microsoft Internet Explorer or Netscape, type in the web address: http://gtwc.gm.com. 2. IN the pop-up logon window, type your User ID (which is your Business Association Code) and your password (your initial password is the same as your User ID) and then click the OK button. 3. For security, each dealer is encouraged to change their password after they logon the first time. Click on "Change Password" from the upper right-hand menu bar and follow the instructions provided. Please note that User IDs and passwords are case sensitive. 4. From the "Create New Adjustment" screen, select your GM Dealer Code from the drop-down menu. 5. Proceed through the form, using the drop-down menus and "populate" buttons to auto-fill related data. 6. Help buttons are located at individual data fields and overall forms help and definitions are available at the top right of the screen. 7. From the bottom of the screen, you can "Save as Draft" to complete the form later or "Submit" the form if it is complete. 8. A confirmation screen will appear allowing you to print the form. Three copies of the form should be printed. One copy will be provided to the tire store to obtain a replacement tire. The second copy will be sent with the returned tire and the third copy should be retained. in the vehicle history file. In addition, an option to quickly create another form called "Next Tire Same Vehicle" is shown. 9. On the navigation menu bar across the top of the screen, "Edit" and "View" choices provide a way to get back to incomplete forms or view forms that have been submitted. A search mechanism is available to sort through forms by fields (date of form, repair order number, etc.). U.S. help Line for GTWC Website Users: 1-888-337-1010 Follow prompt 3: For GM ACCESS, DealerWorld and Other Internet Applications Obtaining New Tires 1. Determine the vehicle and tire eligibility based on the What Is Covered/What Is Not Covered portion of this bulletin. 2. A GM Tire Requisition and Return Document must be completed electronically on the website to obtain tires. Pressing the web form Submit" button does NOT order a new tire. GM dealers will need to print a copy of the completed web form to get the replacement tire from the local tire dealer. 3. New tires are to be obtained through the local tire dealer using a printed copy of the GM Tire Requisition and Return web form. A warranty replacement tire will be provided at no charge. Dealers are NOT to purchase warranty replacement tires. If a tire dealer is not convenient, call the tire manufacturer's toll-free phone number (listed later in this bulletin). Some tire companies will ship direct to the GM dealership. 4. New tires should be properly mounted, dynamically balanced and installed in the customer's vehicle. Proper balance weights and wheel nut torque procedures must be used. Returning Old Tires MOST tires replaced under the New Vehicle Limited Bumper-to-Bumper Warranty will be returned to the tire manufacturer. This is done using pre-addressed, prepaid UPS shipping labels. These labels can be obtained from Helm by calling 1-888-549-6152. Do NOT call UPS or the tire companies for these labels. There will be instances when the GM Warranty Parts Center (WPC) will request tires. Therefore, all replaced tires must be retained until receipt of claim payment. The WPC will request a tire(s) on the same day the credit memo is received at the GM dealership. If no WPC request is received, the dealer should return tires to the proper tire manufacturer. GM dealers are encouraged to submit warranty claims as soon as possible in order to alleviate storage of tires. Whether returned to the tire manufacturer or the WPC, a printed copy of the Tire Requisition and Return Document web form and the repair order must be placed in an envelope and securely taped to EACH tire being returned. A shipping label to the WPC or tire company must be attached to EACH tire being returned. Using a tire crayon, mark the tire to indicate the reason for replacement or location of the defect. Submitting a Warranty Claim Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 00-03-10-003B > May > 01 > Tires - Bumper To Bumper Warranty Coverage > Page 2326 1. The correct tire warranty labor code must be used for the brand of tire replaced. Choose the correct labor code from the list as shown. 2. The generic number 09592318 MUST be inserted on all tire claims in the "part number" field regardless of manufacturer to ensure correct processing. 3. A $25 administrative allowance per repair order MUST be inserted in the "parts amount" field. 4. Labor for mounting and balancing should be submitted. 5. Freight charges for tire returns are NOT to be submitted. Labor time to replace one tire, including mounting and balancing, is 0.6 hr. Each additional tire replaced is 0.4 hr. Important: For tire replacement because of transportation damage or incorrect parts, use labor code E0421 and submit as a transportation claim. Tire Company Assistance DISCLAIMER Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 70-05-01 > Sep > 97 > Tires - Replacement During Bumper to Bumper Warranty Technical Service Bulletin # 70-05-01 Date: 970901 Tires - Replacement During Bumper to Bumper Warranty File In Section: Warranty Administration Bulletin No.: 70-05-01 Date: September, 1997 WARRANTY ADMINISTRATION Subject: Tire Replacement During Bumper to Bumper Vehicle Warranty Models: All 1996 and Newer Passenger Cars and Light Duty Trucks and All 1995 Cadillac Models Recent reviews of Tire Warranty Claims, including the physical inspection of tires returned by dealers to the tire manufacturers inspection centers, has identified areas of warranty administration needing improvement. The purpose of this bulletin is to point out those problem areas, recommend corrective solutions and to list the sources of information which could be of assistance to dealers in the administration of the tire portion of the GM Bumper to Bumper Vehicle Warranty. There are a number of reasons that tires may require replacement. The following information identities those reasons and what actions, if any, should be taken. When tire(s) replacement is required during the GM Bumper to Bumper Vehicle Warranty, they are to be obtained from the appropriate local tire dealer. - Provide the local tire dealer with a properly completed photocopy of the GM Tire Requisition and Return Document, and the repair order. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 70-05-01 > Sep > 97 > Tires - Replacement During Bumper to Bumper Warranty > Page 2331 - If assistance in obtaining replacement tire(s) is needed, contact the Tire Manufacturer using their toll-free Assistance Numbers: Tire Manufacturer Assistance Numbers BRIDGESTONE and 1-800-356-4644 FIRESTONE GENERAL 1-800-847-3349 GOODYEAR 1-800-782-7949 MICHELIN 1-800-887-0662 UNIROYAL and B.F. GOODRICH 1-800-231-5893 Return of tire(s) adjusted under the GM Bumper to Bumper Vehicle Warranty to the appropriate tire manufacturer return centers. - UPS will pickup adjusted tire(s) for return to the tire manufacturers return center during their routine weekly dealer delivery schedule. Dealer will not be charged tire return freight charges by UPS. - Quantities of preprinted, prepaid UPS shipping labels to the tire manufacturer's return center are available at no-charge through GM Fulfillment 1-800-269-5100. - Dealer should have adjusted tire(s) ready for pickup by UPS for shipment to the appropriate tire manufacturers return center within two business days after tire replacement(s). Tires scheduled for return are to be received at the tire manufacturers return location within 30 days after acquisition of the new tire(s). Dealer failure to return the failed tire(s) within this prescribed time limit will result in automatic debit of warranty claim. Important: Only tires replaced under the GM Bumper to Bumper Vehicle Warranty are to be returned to the tire manufacturers return center. Tires adjusted under the GM Bumper to Bumper Vehicle Warranty, received at tire manufacturers return center, must include the following required paper work: Tire Requisition and Return Document - Complete the owner information, tire warranty data, replaced tire information, and reason for tire removal sections of the GM Tire Requisition and Return Document. Photocopy forms as needed from the GM Service Policies and Procedures Manual, Article 1.5, or Service Bulletins. Repair Order - Staple the completed GM Tire Requisition and Return Document to a photocopy of the R.O. and place in an envelope. Also include copies of any other paperwork received from the tire dealer. Attach the envelope to the adjusted tire using clear package tape wrapped completely around the body of the tire. Tire returns received with improper or no paperwork will be subject to debit. Cause of failure determined to be other than detects in materials and/or workmanship. - Normal tire wear is not covered by warranty. - Road hazard damage such as punctures, cuts, snags and breaks resulting from pothole impact, curb impact, or from other objects, is not covered (sealant tires do have road hazard coverage and are to be handled directly with the tire dealer or tire manufacturer). - Damage from improper inflation, spinning (as when stuck in mud or snow), tire chains, racing, improper mounting or dismounting, misuse, negligence, alteration, vandalism, or misapplication is not covered. - Dealer Claims for tires returned with no identifiable defects in material and workmanship will be subject to debit. The following sources of information are available to assist dealers with proper tire problem diagnosis, repair, Warranty Administration and Service Information. - Information contained in the Warranty and Owner Assistance Information Booklet under "What is" and "What is Not Covered". - GM Techline Tire Warranty Training Video and GM Techline Tire Warranty Procedures Booklet available through GM Training 1-800-393-4831. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 70-05-01 > Sep > 97 > Tires - Replacement During Bumper to Bumper Warranty > Page 2332 - Warranty Administration Bulletin Number 52-05-09, 60-05-01, and 60-05-02 dated October 1995, May 1996 and November 1996 respectively. - GM Service Policies and Procedures Manual, Articles 1.5.2E, and 1.5.12. - GM Service Manuals, Section 3E. - Vibration Diagnosis Training through GM Training Centers. - In-Dealership training programs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 600501 > Apr > 96 > Warranty - Tire Replacement Tires: Technical Service Bulletins Warranty - Tire Replacement File In Section: Warranty Administration Bulletin No.: 60-05-01 Date: April, 1996 WARRANTY ADMINISTRATION Subject: Tire Replacements Models: All Passenger Cars and Light Duty Trucks With bulletin number 52-05-09 dated October, 1995, GM announced the 1996 Tire Warranty Administration Program for all divisions. The purpose of this bulletin is to clarify the use and application of warranty labor operation numbers in conjunction with tire replacements. ALL 1996 GM PASSENGER CARS AND LIGHT DUTY TRUCKS AND 1995 CADILLAC TIRE REPLACEMENTS UNDER THE BUMPER-TO-BUMPER COVERAGE When replacing a defective OEM tire under the bumper-to-bumper warranty, dealer may submit a warranty claim for labor utilizing the appropriate GM labor operation as shown. These labor operations and times will be published in the April, 1996 edition of the GM Labor Time Guides. Important: In the event one or more tires are replaced under the bumper-to-bumper warranty, dealer is to submit $25 administrative allowance as a net item per repair order. Also, any sublet charges for mounting and balancing by the tire dealer are to be submitted as a net item. ALL MODEL YEAR GM PASSENGER CAR AND LIGHT DUTY TRUCK TIRE REPLACEMENT FOR REASONS OTHER THAN A DEFECTIVE TIRE The following claims submission practices continue to apply to all model year vehicles. When replacing a tire that failed because of a defect in material or workmanship of another warranted component, include associated costs (parts and labor) with the claim for replacement of that failed part/component. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 600501 > Apr > 96 > Warranty - Tire Replacement > Page 2337 Dealer reimbursement for tires adjusted under vehicle warranty will be at dealer net cost of tires, and any mounting, balancing and freight charges not covered by the tire manufacturer, plus a 0.2 hour handling allowance on each tire replacement R.O. No warranty parts handling allowance applies. Important: This type of claim will require appropriate authorization. Tire failure due to road hazard damage should not be submitted to GM for reimbursement and is not included in the replacement guidelines contained in this bulletin. ALL TRANSMISSION CLAIMS FOR TIRE REPLACEMENT For tire replacement because of transportation damage or missing/incorrect parts, use labor operation number E0421 and submit as a transportation claim. Refer to your GM claims processing manual for complete claims submission details. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > Page 2338 Tires: Technical Service Bulletins Tires/Wheels - Tire Puncture Repair Procedures INFORMATION Bulletin No.: 04-03-10-001F Date: April 27, 2010 Subject: Tire Puncture Repair Procedures For All Cars and Light Duty Trucks Models: 2011 and Prior GM Passenger Cars and Light Duty Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 04-03-10-001E (Section 03 - Suspension). This bulletin covers puncture repair procedures for passenger car and light duty truck radial tires in the tread area only. The tire manufacturer must be contacted for its individual repair policy and whether or not the speed rating is retained after repair. Caution - Tire changing can be dangerous and should be done by trained professionals using proper tools and procedures. Always read and understand any manufacturer's warnings contained in their customers literature or molded into the tire sidewall. - Serious eye and ear injury may result from not wearing adequate eye and ear protection while repairing tires. - NEVER inflate beyond 275 kPa (40 pounds) pressure to seat beads. Some run flat tires, such as the Goodyear Extended Mobility Tire (EMT) used on the Corvette, may require more than 275 kPa (40 psi) to seat the bead. In such a case, a tire safety cage must be used. Consult the tire manufacturer for its individual repair policy. - NEVER stand, lean or reach over the assembly during inflation. Repairable area on a radial tire. Important - NEVER repair tires worn to the tread indicators 1.59 mm (2/32") remaining depth). - NEVER repair tires with a tread puncture larger than 6.35 mm (1/4"). - NEVER substitute an inner tube for a permissible or non-permissible repair. - NEVER perform an outside-in tire repair (plug only, on the wheel). - Every tire must be removed from the wheel for proper inspection and repair. - Regardless of the type of repair used, the repair must seal the inner liner and fill the injury. - Consult with repair material supplier/manufacturer for repair unit application procedures and repair tools/repair material recommendations. Three basic steps for tire puncture repair: 1. Remove the tire from the wheel for inspection and repair. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > Page 2339 2. Fill the injury (puncture) to keep moisture out. 3. Seal the inner liner with a repair unit to prevent air loss. External Inspection 1. Prior to demounting, inspect the tire surface, the valve and the wheel for the source of the leak by using a water and soap solution. Mark the injured area and totally deflate the tire by removing the valve core. 2. Demount the tire from the wheel and place the tire on a well-lighted spreader. Internal Inspection 1. Spread the beads and mark the puncture with a tire crayon. 2. Inspect the inner tire for any signs of internal damage. 3. Remove the puncturing object, noting the direction of the penetration. 4. Probe the injury with a blunt awl in order to determine the extent and direction of the injury. 5. Remove any loose foreign material from the injury. 6. Punctures exceeding 6.35 mm (1/4") should not be repaired. Cleaning 1. Clean the area around the puncture thoroughly with a proper liner cleaner, clean cloth and a scraper. This step serves to remove dirt and mold lubricants to insure proper adhesion and non-contamination of the buffing tool. 2. Refer to information on the product or manufacturer's Material Safety Data Sheet and follow guidelines for handling and disposal. Clean the Injury Channel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > Page 2340 1. Use a proper hand reamer, carbide cutter or drill bit to ream the puncture channel from the inside of the tire in order to clean the injury. 2. Remove steel wires protruding above the liner surface to prevent damage to the repair unit. 3. Consult your repair material supplier for recommended reaming tool(s). Fill the Injury 1. It is necessary to fill the injury channel to provide back up for the repair unit and to prevent moisture from entering the tire fabric and steel wires. 2. (For combination repair/plug units skip this step.) Cement the injured channel and fill the injury from the inside of the tire with the repair plug per repair material manufacturer's recommendations. Without stretching the plug, cut the plug off just above the inside tire surface. 3. Consult your repair material supplier for proper repair material selection. Repair Unit Selection Important Do not install the repair unit in this step. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > Page 2341 1. Center the repair unit over the injury as a reference and outline an area larger than the unit so that buffing will not remove the crayon marks. 2. Remove the repair unit. 3. DO NOT overlap previous or multiple repair units. 4. Consult your repair material supplier for proper repair unit selection. Buffing 1. To prevent contamination and preserve the outline, buff within the marked area thoroughly and evenly with a low speed buffing tool using a fine wire brush or gritted rasp. 2. Buff to a smooth velvet surface (RMA #1 or #2 buffed texture). 3. Use caution not to gouge the inner liner or expose casing fabric. 4. Remove any buffing dust with a vacuum cleaner. 5. Consult your repair material supplier for a proper buffing tool. Cementing Apply chemical cement according to the repair material manufacturer's procedures. Repair Unit Application Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > Page 2342 1. The tire must be in the relaxed position when the repair unit is installed (Do not spread the beads excessively). Two-Piece Plug and Repair Units 1. If applicable, install the repair unit so that the alignment is correct. 2. Center the repair unit over the injury and stitch down thoroughly with the stitching tool, working from the center out. 3. Being careful not to stretch the plug material, cut the plug flush with the outer tread. Combination Repair/Plug Units 1. Pull the plug through the injury until the repair just reaches the liner. Stitch down thoroughly. 2. Follow the repair material manufacturer's recommendations for further installation instructions. 2. Consult your repair material supplier for the proper stitching tool. Safety Cage Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > Page 2343 Some run flat tires, such as the Goodyear Extended Mobility Tire (EMT) used on the Corvette, may require more than 275 kPa (40 psi) to seat the bead. In such a case, a tire safety cage must be used. Consult the tire manufacturer for its individual repair policy. Final Inspection 1. After remounting and inflating the tire, check both beads, the repair and the valve with a water and soap solution in order to detect leaks. 2. If the tire continues to lose air, the tire must be demounted and reinspected. 3. Balance the tire and wheel assembly. Refer to Tire and Wheel Assembly Balancing - OFF Vehicle. For additional tire puncture repair information, contact: Rubber Manufacturers Association (RMA) Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > Page 2344 Tires: Technical Service Bulletins Tires - Correct Inflation Pressure Information INFORMATION Bulletin No.: 00-00-90-002J Date: January 28, 2009 Subject: Information on Proper Tire Pressure Models: 2010 and Prior GM Passenger Cars and Light Duty Trucks (including Saturn) 2009 and Prior HUMMER H2, H3, H3T 2005-2009 Saab 9-7X Supercede: This bulletin is being revised to add model years and clarify additional information. Please discard Corporate Bulletin Number 00-00-90-002I (Section 00 - General Information). Important: ^ Adjustment of tire pressure for a customer with a Low Tire Pressure Monitor (TPM) light on and no codes in the TPM system is NOT a warrantable repair. Claims to simply adjust the tire pressure will be rejected. ^ ALL tires (including the spare tire) MUST be set to the recommended inflation pressure stated on the vehicle's tire placard (on driver's door) during the PRE-DELIVERY INSPECTION (PDI). Recommended inflation pressure is not the pressure printed on tire sidewall. ^ Tires may be over-inflated from the assembly plant due to the mounting process. ^ Generally a 5.6°C (10°F) temperature change will result in (is equivalent to) a 6.9 kPa (1 psi) tire pressure change. ^ 2008-2009 HUMMER H2 Only - The H2 comes standard with Light Truck "D" Load Range tires with a recommended cold inflation pressure of 289 kPa (42 psi). These tires will alert the driver to a low pressure situation at roughly 262 kPa (38 psi) due to a requirement in FMVSS 138 which specifies a Minimum Activation Pressure for each tire type. This creates a relatively narrow window of "usable" pressure values and the warning will be more sensitive to outside temperature changes during the colder months. As with other cold temperature/tire pressure issues, there is nothing wrong with the system itself. If a vehicle is brought in with this concern, check for tire damage and set all tires to the Recommended Cold Inflation Pressure shown on the vehicle placard. Accurate tire pressures ensure the safe handling and appropriate ride characteristics of GM cars and trucks. It is critical that the tire pressure be adjusted to the specifications on the vehicle¡C■s tire placard during PDI. Ride, handling and road noise concerns may be caused by improperly adjusted tire pressure. The first step in the diagnosis of these concerns is to verify that the tires are inflated to the correct pressures. The recommended tire inflation pressure is listed on the vehicle¡C■s tire placard. The tire placard is located on the driver¡C■s side front or rear door edge, center pillar, or the rear compartment lid. Tip ^ Generally a 5.6°C (10°F) temperature increase will result in (is equivalent to) a 6.9 kPa (1 psi) tire pressure increase. ^ The definition of a "cold" tire is one that has been sitting for at least 3 hours, or driven no more than 1.6 km (1 mi). ^ On extremely cold days, if the vehicle has been indoors, it may be necessary to compensate for the low external temperature by adding additional air to the tire during PDI. ^ During cold weather, the Tire Pressure Monitor (TPM) indicator light (a yellow horseshoe with an exclamation point) may illuminate. If this indicator turns off after the tires warm up (reach operating temperature), the tire pressure should be reset to placard pressure at the cold temperature. ^ The TPM system will work correctly with nitrogen in tires. ^ The TPM system is compatible with the GM Vehicle Care Tire Sealant but may not be with other commercially available sealants. Important: ^ Do not use the tire pressure indicated on the tire itself as a guide. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > Page 2345 ^ Always inspect and adjust the pressure when the tires are cold. ^ Vehicles that have different pressures for the front and the rear need to be adjusted after tire rotation. Improper tire inflation may result in any or all of the following conditions: ^ Premature tire wear ^ Harsh ride ^ Excessive road noise ^ Poor handling ^ Reduced fuel economy ^ Low Tire Pressure Monitor (TPM) Light ON ^ Low Tire Pressure Message on the Drivers Information Center (DIC) Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > Page 2346 Tires: Technical Service Bulletins Tires - Sidewall Damage File In Section: 03 Suspension Bulletin No.: 01-03-10-011 Date: December, 2001 INFORMATION Subject: Tire Sidewall Damage Models: 2002 and Prior Passenger Cars and Light Duty Trucks Inspection of a number of tires returned to the Warranty Parts Center and the various tire manufacturers has revealed gouges and/or abrasions that are located on the tire's outboard sidewall. Typically, these gouges and/or abrasions appear to be located near where the tire was marked for wheel balance weight installation at the vehicle assembly plant. It has been determined that this type of surface damage to the tire may be the result of dealers or owners using a high pressure power washer to remove wax/paint/ink marks from the tire sidewall. Do not use a high pressure power washer on tires. To remove any markings from the tire's sidewall, only use soap water and a scrub brush. This type of tire sidewall damage should not be considered as a warrantable condition. DISCLAIMER Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > Customer Interest: > 00-03-10-006F > May > 10 > Wheels/Tires - Tire Radial Force Variation (RFV) Wheels: Customer Interest Wheels/Tires - Tire Radial Force Variation (RFV) INFORMATION Bulletin No.: 00-03-10-006F Date: May 04, 2010 Subject: Information on Tire Radial Force Variation (RFV) Models: 2011 and Prior GM Passenger Cars and Light Duty Trucks 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X 2000-2005 Saturn L Series 2003-2007 Saturn ION Supercede: This bulletin is being revised to considerably expand the available information on Radial Force Variation (RFV) and should be reviewed in whole. Please discard Corporate Bulletin Number 00-03-10-006E (Section 03 - Suspension). Important - Before measuring tires on equipment such as the Hunter GSP9700, the vehicle MUST be driven a minimum of 16 km (10 mi) to ensure removal of any flat-spotting. Refer to Corporate Bulletin Number 03-03-10-007E - Tire/Wheel Characteristics of GM Original Equipment Tires. - Equipment such as the Hunter GSP9700 MUST be calibrated prior to measuring tire/wheel assemblies for each vehicle. The purpose of this bulletin is to provide guidance to GM dealers when using tire force variation measurement equipment, such as the Hunter GSP9700. This type of equipment can be a valuable tool in diagnosing vehicle ride concerns. The most common ride concern involving tire radial force variation is highway speed shake on smooth roads. Tire related smooth road highway speed shake can be caused by three conditions: imbalance, out of round and tire force variation. These three conditions are not necessarily related. All three conditions must be addressed. Imbalance is normally addressed first, because it is the simpler of the three to correct. Off-vehicle, two plane dynamic wheel balancers are readily available and can accurately correct any imbalance. Balancer calibration and maintenance, proper attachment of the wheel to the balancer, and proper balance weights, are all factors required for a quality balance. However, a perfectly balanced tire/wheel assembly can still be "oval shaped" and cause a vibration. Before balancing, perform the following procedures. Tire and Wheel Diagnosis 1. Set the tire pressure to the placard values. 2. With the vehicle raised, ensure the wheels are centered on the hub by loosening all wheel nuts and hand-tightening all nuts first by hand while shaking the wheel, then torque to specifications using a torque wrench, NOT a torque stick. 3. Visually inspect the tires and the wheels. Inspect for evidence of the following conditions and correct as necessary: - Missing balance weights - Bent rim flange - Irregular tire wear - Incomplete bead seating - Tire irregularities (including pressure settings) - Mud/ice build-up in wheel - Stones in the tire tread - Remove any aftermarket wheels and/or tires and restore vehicle to original condition prior to diagnosing a smooth road shake condition. 4. Road test the vehicle using the Electronic Vibration Analyzer (EVA) essential tool. Drive for a sufficient distance on a known, smooth road surface to duplicate the condition. Determine if the vehicle is sensitive to brake apply. If the brakes are applied lightly and the pulsation felt in the steering wheel increases, refer to the Brakes section of the service manual that deals with brake-induced pulsation. If you can start to hear the vibration as a low boom noise (in addition to feeling it), but cannot see it, the vehicle likely has a first order (one pulse per propshaft revolution) driveline vibration. Driveline first order vibrations are high enough in frequency that most humans can start to hear them at highway speeds, but are too high to be able to be easily seen. These issues can be caused by driveline imbalance or misalignment. If the vehicle exhibits this low boom and the booming pulses in-and-out on a regular basis (like a throbbing), chances are good that the vehicle could have driveline vibration. This type Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > Customer Interest: > 00-03-10-006F > May > 10 > Wheels/Tires - Tire Radial Force Variation (RFV) > Page 2355 of vibration is normally felt more in the "seat of the pants" than the steering wheel. 5. Next, record the Hertz (Hz) reading as displayed by the EVA onto the tire data worksheet found at the end of this bulletin. This should be done after a tire break-in period of at least 16 km (10 mi) at 72 km/h (45 mph) or greater, in order to eliminate any possible tire flat-spotting. This reading confirms what the vehicle vibration frequency is prior to vehicle service and documents the amount of improvement occurring as the result of the various steps taken to repair. Completing the Steering Wheel Shake Worksheet below is required. A copy of the completed worksheet must be saved with the R.O. and a copy included with any parts returned to the Warranty Parts Center for analysis. A reading of 35 to 50 Hz typically indicates a first order propshaft vibration. If this is the situation, refer to Corporate Bulletin Number 08-07-30-044D. Generally, a reading between 10 and 20 Hz indicates a tire/wheel vibration and if this is the reading obtained, continue using this bulletin. If the tire 1st order vibration goes away and stays away during this evaluation, the cause is likely tire flat-spotting. Tire flat-spotting vibration may come and go at any speed over 72 km/h (45 mph) during the first 10 minutes of operation, if vibration continues after 10 minutes of driving at speeds greater than 72 km/h (45 mph), tire flat-spotting can be ruled out as the cause for vibration. 6. If flat-spotting is the cause, provide the explanation that this has occurred due to the vehicle being parked for long periods of time and that the nature of the tire is to take a set. Refer to Corporate Bulletin Number 03-03-10-007E: Information on Tire/Wheel Characteristics (Vibration, Balance, Shake, Flat Spotting) of GM Original Equipment Tires. 7. If the road test indicates a shake/vibration exists, check the imbalance of each tire/wheel assembly on a known, calibrated, off-car dynamic balancer.Make sure the mounting surface of the wheel and the surface of the balancer are absolutely clean and free of debris. Be sure to chose the proper cone/collet for the wheel, and always use the pilot bore for centering. Never center the wheel using the hub-cap bore since it is not a precision machined surface. If any assembly calls for more than 1/4 ounce on either rim flange, remove all balance weights and rebalance to as close to zero as possible. If you can see the vibration (along with feeling it) in the steering wheel (driving straight without your hands on the wheel), it is very likely to be a tire/wheel first order (one pulse per revolution) disturbance. First order disturbances can be caused by imbalance as well as non-uniformities in tires, wheels or hubs. This first order frequency is too low for a human to hear, but if the amplitude is high enough, it can be seen. If a vibration or shake still exists after balancing, any out of round conditions, of the wheel, and force variation conditions of the tire, must be addressed. Equipment such as the Hunter GSP9700 can address both (it is also a wheel balancer). Tire radial force vibration (RFV) can be defined as the amount of stiffness variation the tire will produce in one revolution under a constant load. Radial force variation is what the vehicle feels because the load (weight) of the vehicle is always on the tires. Although free runout of tires (not under load) is not always a good indicator of a smooth ride, it is critical that total tire/wheel assembly runout be within specification. Equipment such as the Hunter GSP9700 loads the tire, similar to on the vehicle, and measures radial force variation of the tire/wheel assembly. Note that the wheel is affecting the tire's RFV measurement at this point. To isolate the wheel, its runout must be measured. This can be easily done on the Hunter, without the need to set up dial indicators. If the wheel meets the runout specification, the tire's RFV can then be addressed. After measuring the tire/wheel assembly under load, and the wheel alone, the machine then calculates (predicts) the radial force variation of the tire. However, because this is a prediction that can include mounting inaccuracies, and the load wheel is much smaller in diameter than used in tire production, this type of service equipment should NOT be used to audit new tires. Rather, it should be used as a service diagnostic tool to minimize radial force variation of the tire/wheel assembly. Equipment such as the Hunter GSP9700 does an excellent job of measuring wheel runout, and of finding the low point of the wheel (for runout) and the high point of the tire (for radial force variation). This allows the tire to be matched mounted to the wheel for lowest tire/wheel assembly force variation. The machine will simplify this process into easy steps. The following assembly radial force variation numbers should be used as a guide: When measuring RFV and match mounting tires perform the following steps. Measuring Wheel Runout and Assembly Radial Force Variation Important The completed worksheet at the end of this bulletin must be attached to the hard copy of the repair order. - Measure radial force variation and radial runout. - If a road force/balancing machine is used, record the radial force variation (RFV) on the worksheet at the end of this bulletin. It may be of benefit to have the lowest RFV assembly to the front left corner. If the machine is not available and the EVA data suggests there is an issue, swap the tire and wheel assemblies from the front to the back. Re-check on the EVA and if the problem still exists, test another vehicle to find tires that do not exhibit the same frequency and swap those tires onto the subject vehicle. - If a runout/balancing machine is used, record the radial runout of the tire/wheel assemblies on the worksheet at the end of this bulletin. If one or more of the tire/wheel assemblies are more than.040 in (1.02 mm), match mount the tire to the wheel to get below.040 in (1.02 mm). For sensitive customers, readings of 0.030 inch (0.76 mm) or less are preferable, it may also be of benefit to have the lowest runout assembly to the front left corner. If the machine is not available and the EVA data suggests there is an issue, swap the tire and wheel assemblies from the front to the back. Re-check on the EVA and if the problem still exists, test another vehicle to find tires that do not exhibit the same frequency and swap those tires Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > Customer Interest: > 00-03-10-006F > May > 10 > Wheels/Tires - Tire Radial Force Variation (RFV) > Page 2356 onto the subject vehicle. - After match mounting, the tire/wheel assembly must be rebalanced. If match mounting tires to in-spec wheels produces assembly values higher than these, tire replacement may be necessary. Replacing tires at lower values will probably mean good tires are being condemned. Because tires can sometimes become temporarily flat-spotted, which will affect force variation, it is important that the vehicle be driven at least 16 km (10 mi) prior to measuring. Tire pressure must also be adjusted to the usage pressure on the vehicle's tire placard prior to measuring. Most GM vehicles will tolerate radial force variation up to these levels. However, some vehicles are more sensitive, and may require lower levels. Also, there are other tire parameters that equipment such as the Hunter GSP9700 cannot measure that may be a factor. In such cases, TAC should be contacted for further instructions. Important - When mounting a GM wheel to a wheel balancer/force variation machine, always use the wheel's center pilot hole. This is the primary centering mechanism on all GM wheels; the bolt holes are secondary. Usually a back cone method to the machine should be used. For added accuracy and repeatability, a flange plate should be used to clamp the wheel onto the cone and machine. This system is offered by all balancer manufacturers in GM's dealer program. - Any type of service equipment that removes tread rubber by grinding, buffing or truing is NOT recommended, and may void the tire warranty. However, tires may have been ground by the tire company as part of their tire manufacturing process. This is a legitimate procedure. Steering Wheel Shake Worksheet When diagnosing vibration concerns, use the following worksheet in conjunction with the appropriate Vibration Analysis-Road testing procedure in the Vibration Correction sub-section in SI. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > Customer Interest: > 00-03-10-006F > May > 10 > Wheels/Tires - Tire Radial Force Variation (RFV) > Page 2357 Refer to the appropriate section of SI for specifications and repair procedures that are related to the vibration concern. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > Customer Interest: > 05-03-10-003F > Apr > 10 > Tires/Wheels - Low Tire/Leaking Cast Aluminum Wheels Wheels: Customer Interest Tires/Wheels - Low Tire/Leaking Cast Aluminum Wheels TECHNICAL Bulletin No.: 05-03-10-003F Date: April 27, 2010 Subject: Low Tire Pressure, Leaking Cast Aluminum Wheels (Repair with Adhesive Sealant) Models: 2011 and Prior GM Passenger Cars and Light Duty Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X with Cast Aluminum Wheels Supercede: This bulletin is being revised to update the model years and the bulletin reference information. Please discard Corporate Bulletin Number 05-03-10-003E (Section 03 - Suspension). Condition Some customers may comment on a low tire pressure condition. Diagnosis of the low tire pressure condition indicates an air leak through the cast aluminum wheel. Cause Porosity in the cast aluminum wheel may be the cause. Notice This bulletin specifically addresses issues related to the wheel casting that may result in an air leak. For issues related to corrosion of the wheel in service, please refer to Corporate Bulletin Number 08-03-10-006C - Tire Slowly Goes Flat, Tire Air Loss, Low Tire Pressure Warning Light Illuminated, Aluminum Wheel Bead Seat Corrosion (Clean and Resurface Wheel Bead Seat). Correction 1. Remove the tire and wheel assembly from the vehicle. Refer to the appropriate service procedure in SI. 2. Locate the leaking area by inflating the tire to 276 kPa (40 psi) and dipping the tire/wheel assembly in a water bath, or use a spray bottle with soap and water to locate the specific leak location. Important - If the porosity leak is located in the bead area of the aluminum rim (where the tire meets the rim), the wheel should be replaced. - If two or more leaks are located on one wheel, the wheel should be replaced. 3. If air bubbles are observed, mark the location. - If the leak location is on the tire/rubber area, refer to Corporate Bulletin Number 04-03-10-001F Tire Puncture Repair Procedures for All Cars and Light Duty Trucks. - If the leak is located on the aluminum wheel area, continue with the next step. 4. Inscribe a mark on the tire at the valve stem in order to indicate the orientation of the tire to the wheel. 5. Dismount the tire from the wheel. Refer to Tire Mounting and Dismounting. 6. Remove the tire pressure sensor. Refer to Tire Pressure Sensor removal procedure in SI. 7. Scuff the INSIDE rim surface at the leak area with #80 grit paper and clean the area with general purpose cleaner, such as 3M(R) General Purpose Adhesive Cleaner, P/N 08984, or equivalent. 8. Apply a 3 mm (0.12 in) thick layer of Silicone - Adhesive/Sealant, P/N 12378478 (in Canada, use 88900041), or equivalent, to the leak area. 9. Allow for the adhesive/sealant to dry. Notice Caution must be used when mounting the tire so as not to damage the sealer. Damaging the repair area may result in an air leak. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > Customer Interest: > 05-03-10-003F > Apr > 10 > Tires/Wheels - Low Tire/Leaking Cast Aluminum Wheels > Page 2362 10. Align the inscribed mark on the tire with the valve stem on the wheel. 11. Reinstall the Tire Pressure Sensor. Refer to Tire Pressure Sensor installation procedure in SI. 12. Mount the tire on the wheel. Refer to Tire Mounting and Dismounting. 13. Pressurize the tire to 276 kPa (40 psi) and inspect for leaks. 14. Adjust tire pressure to meet the placard specification. 15. Balance the tire/wheel assembly. Refer to Tire and Wheel Assembly Balancing - Off-Vehicle. 16. Install the tire and wheel assembly onto the vehicle. Refer to the appropriate service procedure in SI. Parts Information Warranty Information (excluding Saab U.S. Models) Important The Silicone - Adhesive/Sealant comes in a case quantity of six. ONLY charge warranty one tube of adhesive/sealant per wheel repair. For vehicles repaired under warranty, use: One leak repair per wheel. Warranty Information (Saab U.S. Models) For vehicles repaired under warranty, use the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 00-03-10-002F > Apr > 11 > Wheels - Chrome Wheel Staining/Pitting/Corrosion Wheels: All Technical Service Bulletins Wheels - Chrome Wheel Staining/Pitting/Corrosion INFORMATION Bulletin No.: 00-03-10-002F Date: April 21, 2011 Subject: Chemical Staining, Pitting, Corrosion and/or Spotted Appearance of Chromed Aluminum Wheels Models: 2012 and Prior GM Cars and Trucks Supercede: This bulletin is being revised to update model years, suggest additional restorative products and add additional corrosion information. Please discard Corporate Bulletin Number 00-03-10-002E (Section 03 - Suspension). Important You may give a copy of this bulletin to the customer. What is Chemical Staining of Chrome Wheels? Figure 1 Chemical staining in most cases results from acid based cleaners (refer to Figure 1 for an example). These stains are frequently milky, black, or greenish in appearance. They result from using cleaning solutions that contain acids on chrome wheels. Soap and water is usually sufficient to clean wheels. If the customer insists on using a wheel cleaner they should only use one that specifically states that it is safe for chromed wheels and does not contain anything in the following list. (Dealers should also survey any products they use during prep or normal cleaning of stock units for these chemicals.) - Ammonium Bifluoride (fluoride source for dissolution of chrome) - Hydrofluoric Acid (directly dissolves chrome) - Hydrochloric Acid (directly dissolves chrome) - Sodium Dodecylbenzenesulfonic Acid - Sulfamic Acid - Phosphoric Acid - Hydroxyacetic Acid Notice Many wheel cleaner instructions advise to take care to avoid contact with painted surfaces. Most customers think of painted surfaces as the fenders, quarter panels and other exterior sheet metal. Many vehicles have painted brake calipers. Acidic wheel cleaners may craze, crack, or discolor the paint on the brake calipers. Damage from wheel cleaners is not covered under the vehicle new car warranty. Soap and water applied with a soft brush is usually all that is required to clean the calipers. Whenever any wheel cleaner is used, it must be THOROUGHLY rinsed off of the wheel with clean, clear water. Special care must be taken to rinse under the hub cap, balance weights, wheel nuts, lug nut caps, between the wheel cladding and off the back side of the wheel. Wheels returned to the Warranty Parts Center (WPC) that exhibit damage from wheel cleaners most often have the damage around and under the wheel weight where the cleaner was incompletely flushed away. Notice Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 00-03-10-002F > Apr > 11 > Wheels - Chrome Wheel Staining/Pitting/Corrosion > Page 2368 Do not use cleaning solutions that contain hydrofluoric, oxalic and most other acids on chrome wheels (or any wheels). If the customer is unsure of the chemical make-up of a particular wheel cleaner, it should be avoided. For wheels showing signs of milky staining from acidic cleaners, refer to Customer Assistance and Instructions below. Warranty of Stained Chrome Wheels Stained wheels are not warrantable. Most acid based cleaners will permanently stain chrome wheels. Follow-up with dealers has confirmed that such cleaners were used on wheels that were returned to the Warranty Parts Center (WPC). Any stained wheels received by the WPC will be charged back to the dealership. To assist the customer, refer to Customer Assistance and Instructions below. Pitting or Spotted Appearance of Chrome Wheels Figure 2 A second type or staining or finish disturbance may result from road chemicals, such as calcium chloride used for dust control of unpaved roads. The staining will look like small pitting (refer to Figure 2). This staining will usually be on the leading edges of each wheel spoke, but may be uniformly distributed. If a vehicle must be operated under such conditions, the chrome wheels should be washed with mild soap and water and thoroughly rinsed as soon as conveniently possible. Important Road chemicals, such as calcium chloride used for dust control of unpaved roads, can also stain chrome wheels. The staining will look like small pitting. This staining will usually be on the leading edges of each wheel spoke. This is explained by the vehicle traveling in the forward direction while being splashed by the road chemical. If a vehicle must be operated under such conditions, the chrome wheels should be washed with mild soap and water and thoroughly rinsed as soon as conveniently possible. Warranty of Pitted or Spotted Chrome Wheels Wheels returned with pitting or spotting as a result of road chemicals may be replaced one time. Damage resulting from contact with these applied road chemicals is corrosive to the wheels finish and may cause damage if the wheels are not kept clean. Important Notify the customer that this is a one time replacement. Please stress to the customer the vital importance of keeping the wheels clean if they are operating the vehicle in an area that applies calcium chloride or other dust controlling chemicals! "GM of Canada" dealers require prior approval by the District Manager - Customer Care and Service Process (DM-CCSP). "Stardust" Corrosion of Chrome Wheels Figure 3 A third type of finish disturbance results from prolonged exposure to brake dust and resultant penetration of brake dust through the chrome. As brakes are applied hot particles of brake material are thrown off and tend to be forced through the leading edge of the wheel spoke windows by airflow. These Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 00-03-10-002F > Apr > 11 > Wheels - Chrome Wheel Staining/Pitting/Corrosion > Page 2369 hot particles embed themselves in the chrome layer and create a small pit. If the material is allowed to sit on the wheel while it is exposed to moisture or salt, it will corrode the wheel beneath the chrome leaving a pit or small blister in the chrome. Heavy brake dust build-up should be removed from wheels by using GM Chrome Cleaner and Polish, P/N 1050173 (in Canada use 10953013). For moderate cleaning, light brake dust build-up or water spots use GM Swirl Remover Polish, P/N 12377965 (in Canada, use Meguiars Plast-X(TM) Clear Plastic Cleaner and Polish #G12310C**). After cleaning, the wheel should be waxed using GM Cleaner Wax, P/N 12377966 (in Canada, use Meguiars Cleaner Wax #M0616C**), which will help protect the wheel from brake dust and reduce adhesion of any brake dust that gets on the wheel surface. For general maintenance cleaning, PEEK Metal Polish† may be used. It will clean and shine the chrome and leave behind a wax coating that may help protect the finish. Warranty of Stardust Corroded Chrome Wheels Wheels returned with pitting or spotting as a result of neglect and brake dust build-up may be replaced one time. Important Notify the customer that this is a one time replacement. Please stress to the customer the vital importance of keeping the wheels clean and free of prolonged exposure to brake dust build-up. "GM of Canada" dealers require prior approval by the District Manager - Customer Care and Service Process (DM-CCSP). Customer Assistance and Instructions GM has looked for ways customers may improve the appearance of wheels damaged by acidic cleaners. The following product and procedure has been found to dramatically improve the appearance of stained wheels. For wheels that have milky stains caused by acidic cleaners try the following: Notice THE 3M CHROME AND METAL POLISH REQUIRED FOR THIS PROCEDURE IS AN EXTREMELY AGGRESSIVE POLISH/CLEANER. THE WHEELS MUST BE CLEANED BEFORE APPLICATION TO AVOID SCRATCHING THE WHEEL SURFACE. THIS PRODUCT WILL REDUCE THE THICKNESS OF THE CHROME PLATING ON THE WHEEL AND IF USED INCORRECTLY OR EXCESSIVELY MAY REMOVE THE CHROME PLATING ALL TOGETHER, EXPOSING A LESS BRIGHT AND BRASSY COLORED SUB-LAYER. FOLLOW INSTRUCTIONS EXACTLY. 1. Wash the wheels with vigorously with soap and water. This step will clean and may reduce wheel staining. Flood all areas of the wheel with water to rinse. 2. Dry the wheels completely. Notice Begin with a small section of the wheel and with light pressure buff off polish and examine results. ONLY apply and rub with sufficient force and time to remove enough staining that you are satisfied with the results. Some wheels may be stained to the extent that you may only achieve a 50% improvement while others may be able to be restored to the original lustre. IN ALL CASES, only apply until the results are satisfactory. 3. Apply 3M Chrome and Metal Polish #39527* with a clean terry cloth towel. As you apply the polish, the staining will be diminished. 4. When dry, buff off the polish with a clean portion of the towel. 5. Repeat application of the 3M Chrome and Metal Polish until satisfied with the results. If continued applications fail to improve the appearance further discontinue use. This procedure will improve the appearance of the wheels and may, with repeated applications, restore the finish dramatically. For wheels that exhibit spotting from road chemicals the above procedure may marginally improve the condition but will not restore the finish or remove the pitting. In this type of staining the wheel finish has actually been removed in spots and no manner of cleaning will restore the finish. †*We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Parts Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 00-03-10-002F > Apr > 11 > Wheels - Chrome Wheel Staining/Pitting/Corrosion > Page 2370 *This product is currently available from 3M. To obtain information for your local retail location please call 3M at 1-888-364-3577. **This product is currently available from Meguiars (Canada). To obtain information for your local retail location please call Meguiars at 1-800-347-5700 or at www.meguiarscanada.com. ^ This product is currently available from Tri-Peek International. To obtain information for your local retail location please call Tri-Peek at 1-877-615-4272 or at www.tripeek.com. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 99-08-51-007E > Mar > 11 > Wheels/Tires - Refinishing Aluminum Wheels Wheels: All Technical Service Bulletins Wheels/Tires - Refinishing Aluminum Wheels INFORMATION Bulletin No.: 99-08-51-007E Date: March 17, 2011 Subject: Refinishing Aluminum Wheels Models: 2012 and Prior GM Passenger Cars and Trucks Supercede: This bulletin is being revised to add additional model years. Please discard Corporate Bulletin Number 99-08-51-007D (Section 08 - Body and Accessories). This bulletin updates General Motor's position on refinishing aluminum wheels. GM does not endorse any repairs that involve welding, bending, straightening or re-machining. Only cosmetic refinishing of the wheel's coatings, using recommended procedures, is allowed. Evaluating Damage In evaluating damage, it is the GM Dealer's responsibility to inspect the wheel for corrosion, scrapes, gouges, etc. The Dealer must insure that such damage is not deeper than what can be sanded or polished off. The wheel must be inspected for cracks. If cracks are found, discard the wheel. Any wheels with bent rim flanges must not be repaired or refinished. Wheels that have been refinished by an outside company must be returned to the same vehicle. The Dealer must record the wheel ID stamp or the cast date on the wheel in order to assure this requirement. Refer to Refinisher's Responsibility - Outside Company later in this bulletin. Aluminum Wheel Refinishing Recommendations - Chrome-plated aluminum wheels Re-plating these wheels is not recommended. - Polished aluminum wheels These wheels have a polyester or acrylic clearcoat on them. If the clearcoat is damaged, refinishing is possible. However, the required refinishing process cannot be performed in the dealer environment. Refer to Refinisher's Responsibility - Outside Company later in this bulletin. - Painted aluminum wheels These wheels are painted using a primer, color coat, and clearcoat procedure. If the paint is damaged, refinishing is possible. As with polished wheels, all original coatings must be removed first. Media blasting is recommended. Refer to GM Aluminum Refinishing Bulletin #53-17-03A for the re-painting of this type of wheel. - Bright, machined aluminum wheels These wheels have a polyester or acrylic clearcoat on them. In some cases, the recessed "pocket" areas of the wheel may be painted. Surface refinishing is possible. The wheel must be totally stripped by media blasting or other suitable means. The wheel should be resurfaced by using a sanding process rather than a machining process. This allows the least amount of material to be removed. Important Do not use any re-machining process that removes aluminum. This could affect the dimensions and function of the wheel. Painting is an option to re-clearcoating polished and bright machined aluminum wheels. Paint will better mask any surface imperfections and is somewhat more durable than clearcoat alone. GM recommends using Corsican SILVER WAEQ9283 for a fine "aluminum-like" look or Sparkle SILVER WA9967 for a very bright look. As an option, the body color may also be used. When using any of the painting options, it is recommended that all four wheels be refinished in order to maintain color uniformity. Refer to GM Aluminum Refinishing Bulletin #53-17-03A for specific procedures and product recommendations. Refinisher's Responsibility - Outside Company Important Some outside companies are offering wheel refinishing services. Such refinished wheels will be permanently marked by the refinisher and are warranted by the refinisher. Any process that re-machines or otherwise re-manufactures the wheel should not be used. A refinisher's responsibility includes inspecting for cracks using the Zyglo system or the equivalent. Any cracked wheels must not be refinished. No welding, hammering or reforming of any kind is allowed. The wheel ID must be recorded and follow the wheel throughout the process in order to assure that the same wheel is returned. A plastic media blast may be used for clean up of the wheel. Hand and/or lathe sanding of the machined surface and the wheel window is allowed. Material removal, though, must be kept to a minimum. Re-machining of the wheel is not allowed. Paint and/or clear coat must not be present on the following surfaces: the nut chamfers, the wheel mounting surfaces and the wheel pilot hole. The refinisher must permanently ID stamp the wheel and warrant the painted/clearcoated surfaces for a minimum of one year or the remainder of the new vehicle warranty, whichever is Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 99-08-51-007E > Mar > 11 > Wheels/Tires - Refinishing Aluminum Wheels > Page 2375 longer. Important Whenever a wheel is refinished, the mounting surface and the wheel nut contact surfaces must not be painted or clearcoated. Coating these surfaces could affect the wheel nut torque. When re-mounting a tire on an aluminum wheel, coated balance weights must be used in order to reduce the chance of future cosmetic damage. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 06-03-10-010A > Jun > 10 > Wheels - Changing Procedures/Precautions Wheels: All Technical Service Bulletins Wheels - Changing Procedures/Precautions INFORMATION Bulletin No.: 06-03-10-010A Date: June 09, 2010 Subject: Information on Proper Wheel Changing Procedures and Cautions Models: 2011 and Prior GM Passenger Cars and Trucks 2010 and Prior HUMMER Models 2005-2009 Saab 9-7X 2005-2009 Saturn Vehicles Attention: Complete wheel changing instructions for each vehicle line can be found under Tire and Wheel Removal and Installation in Service Information (SI). This bulletin is intended to quickly review and reinforce simple but vital procedures to reduce the possibility of achieving low torque during wheel installation. Always refer to SI for wheel lug nut torque specifications and complete jacking instructions for safe wheel changing. Supercede: This bulletin is being revised to include the 2011 model year and update the available special tool list. Please discard Corporate Bulletin Number 06-03-10-010 (Section 03 Suspension). Frequency of Wheel Changes - Marketplace Driven Just a few years ago, the increasing longevity of tires along with greater resistance to punctures had greatly reduced the number of times wheels were removed to basically required tire rotation intervals. Today with the booming business in accessory wheels/special application tires (such as winter tires), consumers are having tire/wheel assemblies removed - replaced - or installed more than ever. With this increased activity, it opens up more of a chance for error on the part of the technician. This bulletin will review a few of the common concerns and mistakes to make yourself aware of. Proper Servicing Starts With the Right Tools The following tools have been made available to assist in proper wheel and tire removal and installation. - J 41013 Rotor Resurfacing Kit (or equivalent) - J 42450-A Wheel Hub Resurfacing Kit (or equivalent) Corroded Surfaces One area of concern is corrosion on the mating surfaces of the wheel to the hub on the vehicle. Excessive corrosion, dirt, rust or debris built up on these surfaces can mimic a properly tightened wheel in the service stall. Once the vehicle is driven, the debris may loosen, grind up or be washed away from water splash. This action may result in clearance at the mating surface of the wheel and an under-torqued condition. Caution Before installing a wheel, remove any buildup on the wheel mounting surface and brake drum or brake disc mounting surface. Installing wheels with poor metal-to-metal contact at the mounting surfaces can cause wheel nuts to loosen. This may cause a wheel to come off when the vehicle is moving, possibly resulting in a loss of control or personal injury. Whenever you remove the tire/wheel assemblies, you must inspect the mating surfaces. If corrosion is found, you should remove the debris with a die grinder equipped with a fine sanding pad, wire brush or cleaning disc. Just remove enough material to assure a clean, smooth mating surface. The J 41013 (or equivalent) can be used to clean the following surfaces: - The hub mounting surface - The brake rotor mounting surface - The wheel mounting surface Use the J 42450-A (or equivalent) to clean around the base of the studs and the hub. Lubricants, Grease and Fluids Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 06-03-10-010A > Jun > 10 > Wheels - Changing Procedures/Precautions > Page 2380 Some customers may use penetrating oils, grease or other lubricants on wheel studs to aid in removal or installation. Always use a suitable cleaner/solvent to remove these lubricants prior to installing the wheel and tire assemblies. Lubricants left on the wheel studs may cause improper readings of wheel nut torque. Always install wheels to clean, dry wheel studs ONLY. Notice Lubricants left on the wheel studs or vertical mounting surfaces between the wheel and the rotor or drum may cause the wheel to work itself loose after the vehicle is driven. Always install wheels to clean, dry wheel studs and surfaces ONLY. Beginning with 2011 model year vehicles, put a light coating of grease, GM P/N 1051344 (in Canada, P/N 9930370), on the inner surface of the wheel pilot hole to prevent wheel seizure to the axle or bearing hub. Wheel Stud and Lug Nut Damage Always inspect the wheel studs and lug nuts for signs of damage from crossthreading or abuse. You should never have to force wheel nuts down the stud. Lug nuts that are damaged may not retain properly, yet give the impression of fully tightening. Always inspect and replace any component suspected of damage. Tip Always start wheel nuts by hand! Be certain that all wheel nut threads have been engaged BEFORE tightening the nut. Important If the vehicle has directional tread tires, verify the directional arrow on the outboard side of the tire is pointing in the direction of forward rotation. Wheel Nut Tightening and Torque Improper wheel nut tightening can lead to brake pulsation and rotor damage. In order to avoid additional brake repairs, evenly tighten the wheel nuts to the proper torque specification as shown for each vehicle in SI. Always observe the proper wheel nut tightening sequence as shown below in order to avoid trapping the wheel on the wheel stud threads or clamping the wheel slightly off center resulting in vibration. The Most Important Service You Provide While the above information is well known, and wheel removal so common, technicians run the risk of becoming complacent on this very important Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 06-03-10-010A > Jun > 10 > Wheels - Changing Procedures/Precautions > Page 2381 service operation. A simple distraction or time constraint that rushes the job may result in personal injury if the greatest of care is not exercised. Make it a habit to double check your work and to always side with caution when installing wheels. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 00-03-10-006F > May > 10 > Wheels/Tires - Tire Radial Force Variation (RFV) Wheels: All Technical Service Bulletins Wheels/Tires - Tire Radial Force Variation (RFV) INFORMATION Bulletin No.: 00-03-10-006F Date: May 04, 2010 Subject: Information on Tire Radial Force Variation (RFV) Models: 2011 and Prior GM Passenger Cars and Light Duty Trucks 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X 2000-2005 Saturn L Series 2003-2007 Saturn ION Supercede: This bulletin is being revised to considerably expand the available information on Radial Force Variation (RFV) and should be reviewed in whole. Please discard Corporate Bulletin Number 00-03-10-006E (Section 03 - Suspension). Important - Before measuring tires on equipment such as the Hunter GSP9700, the vehicle MUST be driven a minimum of 16 km (10 mi) to ensure removal of any flat-spotting. Refer to Corporate Bulletin Number 03-03-10-007E - Tire/Wheel Characteristics of GM Original Equipment Tires. - Equipment such as the Hunter GSP9700 MUST be calibrated prior to measuring tire/wheel assemblies for each vehicle. The purpose of this bulletin is to provide guidance to GM dealers when using tire force variation measurement equipment, such as the Hunter GSP9700. This type of equipment can be a valuable tool in diagnosing vehicle ride concerns. The most common ride concern involving tire radial force variation is highway speed shake on smooth roads. Tire related smooth road highway speed shake can be caused by three conditions: imbalance, out of round and tire force variation. These three conditions are not necessarily related. All three conditions must be addressed. Imbalance is normally addressed first, because it is the simpler of the three to correct. Off-vehicle, two plane dynamic wheel balancers are readily available and can accurately correct any imbalance. Balancer calibration and maintenance, proper attachment of the wheel to the balancer, and proper balance weights, are all factors required for a quality balance. However, a perfectly balanced tire/wheel assembly can still be "oval shaped" and cause a vibration. Before balancing, perform the following procedures. Tire and Wheel Diagnosis 1. Set the tire pressure to the placard values. 2. With the vehicle raised, ensure the wheels are centered on the hub by loosening all wheel nuts and hand-tightening all nuts first by hand while shaking the wheel, then torque to specifications using a torque wrench, NOT a torque stick. 3. Visually inspect the tires and the wheels. Inspect for evidence of the following conditions and correct as necessary: - Missing balance weights - Bent rim flange - Irregular tire wear - Incomplete bead seating - Tire irregularities (including pressure settings) - Mud/ice build-up in wheel - Stones in the tire tread - Remove any aftermarket wheels and/or tires and restore vehicle to original condition prior to diagnosing a smooth road shake condition. 4. Road test the vehicle using the Electronic Vibration Analyzer (EVA) essential tool. Drive for a sufficient distance on a known, smooth road surface to duplicate the condition. Determine if the vehicle is sensitive to brake apply. If the brakes are applied lightly and the pulsation felt in the steering wheel increases, refer to the Brakes section of the service manual that deals with brake-induced pulsation. If you can start to hear the vibration as a low boom noise (in addition to feeling it), but cannot see it, the vehicle likely has a first order (one pulse per propshaft revolution) driveline vibration. Driveline first order vibrations are high enough in frequency that most humans can start to hear them at highway speeds, but are too high to be able to be easily seen. These issues can be caused by driveline imbalance or misalignment. If the vehicle exhibits this low boom and the booming pulses in-and-out on a regular basis (like a throbbing), chances are good that the vehicle could have driveline vibration. This type Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 00-03-10-006F > May > 10 > Wheels/Tires - Tire Radial Force Variation (RFV) > Page 2386 of vibration is normally felt more in the "seat of the pants" than the steering wheel. 5. Next, record the Hertz (Hz) reading as displayed by the EVA onto the tire data worksheet found at the end of this bulletin. This should be done after a tire break-in period of at least 16 km (10 mi) at 72 km/h (45 mph) or greater, in order to eliminate any possible tire flat-spotting. This reading confirms what the vehicle vibration frequency is prior to vehicle service and documents the amount of improvement occurring as the result of the various steps taken to repair. Completing the Steering Wheel Shake Worksheet below is required. A copy of the completed worksheet must be saved with the R.O. and a copy included with any parts returned to the Warranty Parts Center for analysis. A reading of 35 to 50 Hz typically indicates a first order propshaft vibration. If this is the situation, refer to Corporate Bulletin Number 08-07-30-044D. Generally, a reading between 10 and 20 Hz indicates a tire/wheel vibration and if this is the reading obtained, continue using this bulletin. If the tire 1st order vibration goes away and stays away during this evaluation, the cause is likely tire flat-spotting. Tire flat-spotting vibration may come and go at any speed over 72 km/h (45 mph) during the first 10 minutes of operation, if vibration continues after 10 minutes of driving at speeds greater than 72 km/h (45 mph), tire flat-spotting can be ruled out as the cause for vibration. 6. If flat-spotting is the cause, provide the explanation that this has occurred due to the vehicle being parked for long periods of time and that the nature of the tire is to take a set. Refer to Corporate Bulletin Number 03-03-10-007E: Information on Tire/Wheel Characteristics (Vibration, Balance, Shake, Flat Spotting) of GM Original Equipment Tires. 7. If the road test indicates a shake/vibration exists, check the imbalance of each tire/wheel assembly on a known, calibrated, off-car dynamic balancer.Make sure the mounting surface of the wheel and the surface of the balancer are absolutely clean and free of debris. Be sure to chose the proper cone/collet for the wheel, and always use the pilot bore for centering. Never center the wheel using the hub-cap bore since it is not a precision machined surface. If any assembly calls for more than 1/4 ounce on either rim flange, remove all balance weights and rebalance to as close to zero as possible. If you can see the vibration (along with feeling it) in the steering wheel (driving straight without your hands on the wheel), it is very likely to be a tire/wheel first order (one pulse per revolution) disturbance. First order disturbances can be caused by imbalance as well as non-uniformities in tires, wheels or hubs. This first order frequency is too low for a human to hear, but if the amplitude is high enough, it can be seen. If a vibration or shake still exists after balancing, any out of round conditions, of the wheel, and force variation conditions of the tire, must be addressed. Equipment such as the Hunter GSP9700 can address both (it is also a wheel balancer). Tire radial force vibration (RFV) can be defined as the amount of stiffness variation the tire will produce in one revolution under a constant load. Radial force variation is what the vehicle feels because the load (weight) of the vehicle is always on the tires. Although free runout of tires (not under load) is not always a good indicator of a smooth ride, it is critical that total tire/wheel assembly runout be within specification. Equipment such as the Hunter GSP9700 loads the tire, similar to on the vehicle, and measures radial force variation of the tire/wheel assembly. Note that the wheel is affecting the tire's RFV measurement at this point. To isolate the wheel, its runout must be measured. This can be easily done on the Hunter, without the need to set up dial indicators. If the wheel meets the runout specification, the tire's RFV can then be addressed. After measuring the tire/wheel assembly under load, and the wheel alone, the machine then calculates (predicts) the radial force variation of the tire. However, because this is a prediction that can include mounting inaccuracies, and the load wheel is much smaller in diameter than used in tire production, this type of service equipment should NOT be used to audit new tires. Rather, it should be used as a service diagnostic tool to minimize radial force variation of the tire/wheel assembly. Equipment such as the Hunter GSP9700 does an excellent job of measuring wheel runout, and of finding the low point of the wheel (for runout) and the high point of the tire (for radial force variation). This allows the tire to be matched mounted to the wheel for lowest tire/wheel assembly force variation. The machine will simplify this process into easy steps. The following assembly radial force variation numbers should be used as a guide: When measuring RFV and match mounting tires perform the following steps. Measuring Wheel Runout and Assembly Radial Force Variation Important The completed worksheet at the end of this bulletin must be attached to the hard copy of the repair order. - Measure radial force variation and radial runout. - If a road force/balancing machine is used, record the radial force variation (RFV) on the worksheet at the end of this bulletin. It may be of benefit to have the lowest RFV assembly to the front left corner. If the machine is not available and the EVA data suggests there is an issue, swap the tire and wheel assemblies from the front to the back. Re-check on the EVA and if the problem still exists, test another vehicle to find tires that do not exhibit the same frequency and swap those tires onto the subject vehicle. - If a runout/balancing machine is used, record the radial runout of the tire/wheel assemblies on the worksheet at the end of this bulletin. If one or more of the tire/wheel assemblies are more than.040 in (1.02 mm), match mount the tire to the wheel to get below.040 in (1.02 mm). For sensitive customers, readings of 0.030 inch (0.76 mm) or less are preferable, it may also be of benefit to have the lowest runout assembly to the front left corner. If the machine is not available and the EVA data suggests there is an issue, swap the tire and wheel assemblies from the front to the back. Re-check on the EVA and if the problem still exists, test another vehicle to find tires that do not exhibit the same frequency and swap those tires Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 00-03-10-006F > May > 10 > Wheels/Tires - Tire Radial Force Variation (RFV) > Page 2387 onto the subject vehicle. - After match mounting, the tire/wheel assembly must be rebalanced. If match mounting tires to in-spec wheels produces assembly values higher than these, tire replacement may be necessary. Replacing tires at lower values will probably mean good tires are being condemned. Because tires can sometimes become temporarily flat-spotted, which will affect force variation, it is important that the vehicle be driven at least 16 km (10 mi) prior to measuring. Tire pressure must also be adjusted to the usage pressure on the vehicle's tire placard prior to measuring. Most GM vehicles will tolerate radial force variation up to these levels. However, some vehicles are more sensitive, and may require lower levels. Also, there are other tire parameters that equipment such as the Hunter GSP9700 cannot measure that may be a factor. In such cases, TAC should be contacted for further instructions. Important - When mounting a GM wheel to a wheel balancer/force variation machine, always use the wheel's center pilot hole. This is the primary centering mechanism on all GM wheels; the bolt holes are secondary. Usually a back cone method to the machine should be used. For added accuracy and repeatability, a flange plate should be used to clamp the wheel onto the cone and machine. This system is offered by all balancer manufacturers in GM's dealer program. - Any type of service equipment that removes tread rubber by grinding, buffing or truing is NOT recommended, and may void the tire warranty. However, tires may have been ground by the tire company as part of their tire manufacturing process. This is a legitimate procedure. Steering Wheel Shake Worksheet When diagnosing vibration concerns, use the following worksheet in conjunction with the appropriate Vibration Analysis-Road testing procedure in the Vibration Correction sub-section in SI. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 00-03-10-006F > May > 10 > Wheels/Tires - Tire Radial Force Variation (RFV) > Page 2388 Refer to the appropriate section of SI for specifications and repair procedures that are related to the vibration concern. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 05-03-10-003F > Apr > 10 > Tires/Wheels - Low Tire/Leaking Cast Aluminum Wheels Wheels: All Technical Service Bulletins Tires/Wheels - Low Tire/Leaking Cast Aluminum Wheels TECHNICAL Bulletin No.: 05-03-10-003F Date: April 27, 2010 Subject: Low Tire Pressure, Leaking Cast Aluminum Wheels (Repair with Adhesive Sealant) Models: 2011 and Prior GM Passenger Cars and Light Duty Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X with Cast Aluminum Wheels Supercede: This bulletin is being revised to update the model years and the bulletin reference information. Please discard Corporate Bulletin Number 05-03-10-003E (Section 03 - Suspension). Condition Some customers may comment on a low tire pressure condition. Diagnosis of the low tire pressure condition indicates an air leak through the cast aluminum wheel. Cause Porosity in the cast aluminum wheel may be the cause. Notice This bulletin specifically addresses issues related to the wheel casting that may result in an air leak. For issues related to corrosion of the wheel in service, please refer to Corporate Bulletin Number 08-03-10-006C - Tire Slowly Goes Flat, Tire Air Loss, Low Tire Pressure Warning Light Illuminated, Aluminum Wheel Bead Seat Corrosion (Clean and Resurface Wheel Bead Seat). Correction 1. Remove the tire and wheel assembly from the vehicle. Refer to the appropriate service procedure in SI. 2. Locate the leaking area by inflating the tire to 276 kPa (40 psi) and dipping the tire/wheel assembly in a water bath, or use a spray bottle with soap and water to locate the specific leak location. Important - If the porosity leak is located in the bead area of the aluminum rim (where the tire meets the rim), the wheel should be replaced. - If two or more leaks are located on one wheel, the wheel should be replaced. 3. If air bubbles are observed, mark the location. - If the leak location is on the tire/rubber area, refer to Corporate Bulletin Number 04-03-10-001F Tire Puncture Repair Procedures for All Cars and Light Duty Trucks. - If the leak is located on the aluminum wheel area, continue with the next step. 4. Inscribe a mark on the tire at the valve stem in order to indicate the orientation of the tire to the wheel. 5. Dismount the tire from the wheel. Refer to Tire Mounting and Dismounting. 6. Remove the tire pressure sensor. Refer to Tire Pressure Sensor removal procedure in SI. 7. Scuff the INSIDE rim surface at the leak area with #80 grit paper and clean the area with general purpose cleaner, such as 3M(R) General Purpose Adhesive Cleaner, P/N 08984, or equivalent. 8. Apply a 3 mm (0.12 in) thick layer of Silicone - Adhesive/Sealant, P/N 12378478 (in Canada, use 88900041), or equivalent, to the leak area. 9. Allow for the adhesive/sealant to dry. Notice Caution must be used when mounting the tire so as not to damage the sealer. Damaging the repair area may result in an air leak. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 05-03-10-003F > Apr > 10 > Tires/Wheels - Low Tire/Leaking Cast Aluminum Wheels > Page 2393 10. Align the inscribed mark on the tire with the valve stem on the wheel. 11. Reinstall the Tire Pressure Sensor. Refer to Tire Pressure Sensor installation procedure in SI. 12. Mount the tire on the wheel. Refer to Tire Mounting and Dismounting. 13. Pressurize the tire to 276 kPa (40 psi) and inspect for leaks. 14. Adjust tire pressure to meet the placard specification. 15. Balance the tire/wheel assembly. Refer to Tire and Wheel Assembly Balancing - Off-Vehicle. 16. Install the tire and wheel assembly onto the vehicle. Refer to the appropriate service procedure in SI. Parts Information Warranty Information (excluding Saab U.S. Models) Important The Silicone - Adhesive/Sealant comes in a case quantity of six. ONLY charge warranty one tube of adhesive/sealant per wheel repair. For vehicles repaired under warranty, use: One leak repair per wheel. Warranty Information (Saab U.S. Models) For vehicles repaired under warranty, use the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 04-03-10-012B > Feb > 08 > Wheels - Chrome Wheel Brake Dust Accumulation/Pitting Wheels: All Technical Service Bulletins Wheels - Chrome Wheel Brake Dust Accumulation/Pitting Bulletin No.: 04-03-10-012B Date: February 01, 2008 INFORMATION Subject: Pitting and Brake Dust on Chrome wheels Models: 2008 and Prior GM Passenger Cars and Trucks (including Saturn) 2008 and Prior HUMMER H2, H3 2005-2008 Saab 9-7X Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 04-03-10-012A (Section 03 - Suspension). Analysis of Returned Wheels Chrome wheels returned under the New Vehicle Limited Warranty for pitting concerns have recently been evaluated. This condition is usually most severe in the vent (or window) area of the front wheels. This "pitting" may actually be brake dust that has been allowed to accumulate on the wheel. The longer this accumulation builds up, the more difficult it is to remove. Cleaning the Wheels In all cases, the returned wheels could be cleaned to their original condition using GM Vehicle Care Cleaner Wax, P/N 12377966 (in Canada, P/N 10952905). When using this product, you should confine your treatment to the areas of the wheel that show evidence of the brake dust build-up. This product is only for use on chromed steel or chromed aluminum wheels. Parts Information Warranty Information Wheel replacement for this condition is NOT applicable under the terms of the New Vehicle Limited Warranty. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 99-03-10-102 > Jun > 99 > Warranty - OE Chrome Plated Aluminum Wheel ID Wheels: All Technical Service Bulletins Warranty - OE Chrome Plated Aluminum Wheel ID File In Section: 03 - Suspension Bulletin No.: 99-03-10-102 Date: June, 1999 INFORMATION Subject: Original Equipment Chrome Plated Aluminum Wheel Identification Models: 1999 and Prior Passenger Cars and Light Duty Trucks Chrome plated aluminum wheels have been returned to the Warranty Parts Center that are not the original equipment (OE) components. Original equipment chrome plated aluminum wheels can be identified by either a balance weight clip retention groove (1) or a step (2) that is machined around both of the wheel's rim flanges. The rim flanges (3) of painted original equipment aluminum wheels do not have a groove or a step. Chrome plated aluminum wheels that do not have the wheel rim flange groove or step are aftermarket chrome plated components and are NOT warrantable. Any aftermarket chrome wheels received by the Warranty Parts Center will be charged back to the dealership. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 72-05-05 > Aug > 97 > Warranty - Guidelines for Using E0420 Wheel Replace Wheels: All Technical Service Bulletins Warranty - Guidelines for Using E0420 Wheel Replace File In Section: Warranty Administration Bulletin No.: 72-05-05 Date: August, 1997 WARRANTY ADMINISTRATION Subject: Guidelines for Using EO42O Wheel Replace Models: 1989-98 Passenger Cars and Light Duty Trucks The purpose of this bulletin is to provide service personnel with guidelines for using the above subject labor operation. Effective with repair orders dated on or after September 1, 1997, dealers are to be guided by the following: ^ Aluminum Wheels (including chrome plated) with Porosity - Wheels that exhibit porosity should be repaired as described in the vehicle service manual. Wheels should not be replaced without wholesale approval. ^ Aluminum Wheels (except chrome plated) with a "Finish Defect" - Wheels that exhibit a defect in the finish, (i.e., discoloration or surface degradation) should be refinished as described in the Corporate Service Bulletin Number 53-17-03A released in May, 1996. ^ Chrome Wheels - Wheels that are chromed and found to have a finish defect can only be replaced. ^ Aluminum and chrome wheels replaced under warranty will be subject to random part review and inspection. Those wheels inspected and found not to be defective and/or should have been repaired, will be subject to charge back. Wheels damaged by normal wear, road hazards, car wash brushes, or other physical or chemical damage are not eligible for warranty coverage. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 531703A > May > 96 > Aluminum Wheels - Refinishing Technical Service Bulletin # 531703A Date: 960501 Aluminum Wheels - Refinishing File In Section: 10 - Body Bulletin No.: 53-17-03A Date: May, 1996 INFORMATION Subject: Aluminum Wheel Refinishing Models: 1991-96 Passenger Cars and Trucks This bulletin is being revised to delete the 1990 model year and add the 1996 model year. Please discard Corporate Bulletin Number 53-17-03 (Section 10 - Body). This bulletin supersedes and cancels all previous service bulletins concerning the refinishing of aluminum wheels. The purpose of this service bulletin is to assist dealerships in repairing the discoloration or surface degradation that has occurred on styled aluminum wheels. This bulletin provides NEW PROCEDURES AND SPECIFIC MATERIALS for the refinishing of painted aluminum wheels or aluminum wheels with discoloration or surface degradation. Important: THE RE-MACHINING OF ALUMINUM WHEELS IS NOT RECOMMENDED. THE RE-CLEAR COATING OF ALUMINUM WHEELS IS NO LONGER RECOMMENDED DUE TO CONCERNS OF REPAIR DURABILITY The new procedure requires the wheel surface be plastic media blasted to remove old paint or clear coat. CHEMICAL STRIPPERS ARE NOT RECOMMENDED. Material Required System 1: DuPont Products 3939-S Cleaning Solvent 615/616 Etching Primer URO 5000 Primer Surfacer IMRON 6000 Basecoat 3440-S IMRON Clear System 2: PPG Products DX533 Aluminum Cleaner DX503 Aluminum Conditioner DP Epoxy Primer Deltron Basecoat (DBC) Concept 2001 Clear Acrylic Urethane System 3: Spies Hecker Permahyd Silicone Remover 7090 Permahyd 1:1 Primer 4070 Permahyd 2:1 Surfacer 5080 Permahyd Base Coat Series 280/285 Permahyd H.S. Clearcoat 8060 Color Selection If the wheels being painted were previously clearcoated aluminum, we would recommend using Corsican SILVER WAEQ9283 for a fine "aluminum-like" look or Sparkle SILVER WA9967 for a very bright look. As an option to the customer, you may also use body color. For color Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 531703A > May > 96 > Aluminum Wheels - Refinishing > Page 2410 selection and verification, refer to your paint manufacturer's color book. On wheels that were previous clearcoated aluminum it is recommended that all four wheels and their center caps be refinished to maintain color uniformity. Important: THE PRODUCTS LISTED MUST BE USED AS A SYSTEM. DO NOT MIX OTHER MANUFACTURERS' PRODUCT LINES WITH THE REQUIRED MATERIALS. PRODUCTS LISTED IN THIS BULLETIN HAVE SHOWN THE REQUIRED REPAIR DURABILITY, AND CURRENTLY ARE THE ONLY PAINT SYSTEMS THAT MEET GM SPECIFICATION 4350M-A336. Procedures 1. Remove wheels from vehicle. Tires may remain mounted on wheels. 2. Remove balance weights and mark their location on tire. 3. Wipe excess grease, etc. from wheels with wax and grease remover. 4. Have wheels plastic media blasted to remove clearcoat. FOR FURTHER INFORMATION ON MEDIA BLASTING IN YOUR AREA, CALL US TECHNOLOGIES INC., CONTACT DAVE ROSENBURG AT 1-800-634-9185. Caution: IT IS MANDATORY THAT ADEQUATE RESPIRATORY PROTECTION BE WORN. EXAMPLES OF SUCH PROTECTION ARE: AIR LINE RESPIRATORS WITH FULL HOOD OR HALF MASK. IF NOT AVAILABLE, USE A VAPOR/PARTICULATE RESPIRATOR THAT RESPIRATOR MANUFACTURER RECOMMENDS AS EFFECTIVE FOR ISOCYANATE VAPOR AND MISTS (UNLESS LOCAL REGULATIONS PREVAIL). 5. Painting Process a. Refer to Attachments 1-3 for each System's individual formula and process. b. After following the specific System's individual formula and process, follow these steps: 6. Unmask wheels. 7. Clean all wheel mounting surface of any corrosion, overspray, or dirt. 8. Install new coated balance weights, at marked locations. 9. Replace wheels on vehicle. 10. USE A TORQUE STICK ON AN IMPACT WRENCH, OR A TORQUE WRENCH TO CONSISTENTLY AND UNIFORMLY FASTEN THE WHEEL TO THE SPECIFIED TORQUE FOR THE VEHICLE. THE STAR PATTERN MUST BE FOLLOWED. Important: TORQUE STICKS MUST BE USED ANY TIME AN IMPACT WRENCH IS USED TO TIGHTEN WHEEL NUTS. Warranty Information For vehicles repaired under warranty, use as shown. Attachment 1 - DuPont Products Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 531703A > May > 96 > Aluminum Wheels - Refinishing > Page 2411 Painting Process System: Dupont Products Paint Color Information: Corsican Silver WA EQ9283 Dupont # C9143, Sparkle Silver WA9967 Dupont # C9339 1. Wipe wheel with cleaning solvent: 3939-S, 3949-S or 3900-S. 2. Mask off tires. Important: 3. Mask off all wheel mounting surfaces and wheel mount surfaces. 4. Apply two coats of 615/616-S etching primer to wheel allowing 10 minutes flash between coats. Allow to dry for 30 minutes before applying primer coat. 5. Apply URO 5000 primer 1220/193-S + accelerator 389-S using two coats at 65-70 PSI at the gun. Allow 12-15 minutes between coats. Force bake 30 minutes at 140°F (60°C). 6. Scuff sand using green Scotch-Brite pad. 7. Solvent wipe before top coating. 8. Apply IMRON 6000 base coat to wheel. 2-3 coats to hiding at 60-70 PSI allowing to flash between coats. Base coat needs to dry 20-30 minutes before clearcoat is applied. 9. Apply 3440-S clearcoat to wheel using two coats at 60-70 PSI. Flash 10-15 minutes between coats. 389-S can be used in basecoat and clearcoat to give faster set up times. 10. Allow overnight dry before reassemble. Can be baked for 30 minutes at 140°F (60°C). Attachment 2 - PPG Products Painting Process: PPG System Paint Color Information: Corsican Silver WAEQ9283; PPG # DBC-3531, Sparkle Silver WA9967; PPG # 35367 1. Wash entire wheel with aluminum cleaner DX533, mix 1:3 with water. Allow to react 2-3 minutes and rinse thoroughly. 2. Wash entire wheel with aluminum conditioner DX5O3 straight from the container. Allow to react 2-3 minutes until pale gold or tan color develops. Rinse thoroughly and dry. 3. Mask off tires. Important: 4. Mask off all wheel nut mounting surfaces and wheel mounting surfaces. 5. Apply 1-2 coats of DP Primer and allow to flash for 15-20 minutes. 6. Apply 2-3 coats of Deltron Basecoat (DBC) and allow to flash 20 minutes after the final coat. 7. Apply two (2) wet coats of Concept 2001 Acrylic urethane. 8. Flash 20 minutes and bake 140°F (60°C) for 30 minutes. For more information contact your PPG Jobber. Attachment 3 - Spies Hecker Painting Process: Spies Hecker System Paint Color Information: Corsican Silver AWEQ9283; SH-72913, Sparkle Silver WA9967; SH-71912 1. Clean with Permahyd Silicone Remover 7090. 2. Mask off tires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 531703A > May > 96 > Aluminum Wheels - Refinishing > Page 2412 Important: 3. Mask off all wheel nut mounting surfaces and wheel mounting surfaces. 4. Apply 1-1/2 coats of Permahyd 1:1 Primer 4070. Mix 1:1 with Permahyd Hardener 3070 as per TDS. 5. Allow to flash for 30 minutes. 6. Apply two (2) coats of Permahyd 2:1 Surfacer 5080. Mix 2:1 with Permahyd Hardener 3071 as per TDS. 7. Bake for 60 minutes at 140°F (60°C) or allow to flash for 3 hours at 68°F (20°C). 8. Apply Permahyd Base Coat Series 280/285 as per TDS. 9. Allow to flash 10 to 15 minutes. 10. Apply 1 to 2 coats of Permacron High Solid Clear Coat 8060 as per TDS. 11. Allow to flash 10 minutes. Then bake at 140°F (60°C) for 40 minutes. For more information, contact your SPIES HECKER Jobber. We believe these sources and their products to be reliable. There may be additional manufacturers of such products. General Motors does not endorse, indicate any preference for or assume any responsibility for the products or equipment from these firms or for any such items which may be available from other sources. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 00-03-10-002F > Apr > 11 > Wheels - Chrome Wheel Staining/Pitting/Corrosion Wheels: All Technical Service Bulletins Wheels - Chrome Wheel Staining/Pitting/Corrosion INFORMATION Bulletin No.: 00-03-10-002F Date: April 21, 2011 Subject: Chemical Staining, Pitting, Corrosion and/or Spotted Appearance of Chromed Aluminum Wheels Models: 2012 and Prior GM Cars and Trucks Supercede: This bulletin is being revised to update model years, suggest additional restorative products and add additional corrosion information. Please discard Corporate Bulletin Number 00-03-10-002E (Section 03 - Suspension). Important You may give a copy of this bulletin to the customer. What is Chemical Staining of Chrome Wheels? Figure 1 Chemical staining in most cases results from acid based cleaners (refer to Figure 1 for an example). These stains are frequently milky, black, or greenish in appearance. They result from using cleaning solutions that contain acids on chrome wheels. Soap and water is usually sufficient to clean wheels. If the customer insists on using a wheel cleaner they should only use one that specifically states that it is safe for chromed wheels and does not contain anything in the following list. (Dealers should also survey any products they use during prep or normal cleaning of stock units for these chemicals.) - Ammonium Bifluoride (fluoride source for dissolution of chrome) - Hydrofluoric Acid (directly dissolves chrome) - Hydrochloric Acid (directly dissolves chrome) - Sodium Dodecylbenzenesulfonic Acid - Sulfamic Acid - Phosphoric Acid - Hydroxyacetic Acid Notice Many wheel cleaner instructions advise to take care to avoid contact with painted surfaces. Most customers think of painted surfaces as the fenders, quarter panels and other exterior sheet metal. Many vehicles have painted brake calipers. Acidic wheel cleaners may craze, crack, or discolor the paint on the brake calipers. Damage from wheel cleaners is not covered under the vehicle new car warranty. Soap and water applied with a soft brush is usually all that is required to clean the calipers. Whenever any wheel cleaner is used, it must be THOROUGHLY rinsed off of the wheel with clean, clear water. Special care must be taken to rinse under the hub cap, balance weights, wheel nuts, lug nut caps, between the wheel cladding and off the back side of the wheel. Wheels returned to the Warranty Parts Center (WPC) that exhibit damage from wheel cleaners most often have the damage around and under the wheel weight where the cleaner was incompletely flushed away. Notice Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 00-03-10-002F > Apr > 11 > Wheels - Chrome Wheel Staining/Pitting/Corrosion > Page 2418 Do not use cleaning solutions that contain hydrofluoric, oxalic and most other acids on chrome wheels (or any wheels). If the customer is unsure of the chemical make-up of a particular wheel cleaner, it should be avoided. For wheels showing signs of milky staining from acidic cleaners, refer to Customer Assistance and Instructions below. Warranty of Stained Chrome Wheels Stained wheels are not warrantable. Most acid based cleaners will permanently stain chrome wheels. Follow-up with dealers has confirmed that such cleaners were used on wheels that were returned to the Warranty Parts Center (WPC). Any stained wheels received by the WPC will be charged back to the dealership. To assist the customer, refer to Customer Assistance and Instructions below. Pitting or Spotted Appearance of Chrome Wheels Figure 2 A second type or staining or finish disturbance may result from road chemicals, such as calcium chloride used for dust control of unpaved roads. The staining will look like small pitting (refer to Figure 2). This staining will usually be on the leading edges of each wheel spoke, but may be uniformly distributed. If a vehicle must be operated under such conditions, the chrome wheels should be washed with mild soap and water and thoroughly rinsed as soon as conveniently possible. Important Road chemicals, such as calcium chloride used for dust control of unpaved roads, can also stain chrome wheels. The staining will look like small pitting. This staining will usually be on the leading edges of each wheel spoke. This is explained by the vehicle traveling in the forward direction while being splashed by the road chemical. If a vehicle must be operated under such conditions, the chrome wheels should be washed with mild soap and water and thoroughly rinsed as soon as conveniently possible. Warranty of Pitted or Spotted Chrome Wheels Wheels returned with pitting or spotting as a result of road chemicals may be replaced one time. Damage resulting from contact with these applied road chemicals is corrosive to the wheels finish and may cause damage if the wheels are not kept clean. Important Notify the customer that this is a one time replacement. Please stress to the customer the vital importance of keeping the wheels clean if they are operating the vehicle in an area that applies calcium chloride or other dust controlling chemicals! "GM of Canada" dealers require prior approval by the District Manager - Customer Care and Service Process (DM-CCSP). "Stardust" Corrosion of Chrome Wheels Figure 3 A third type of finish disturbance results from prolonged exposure to brake dust and resultant penetration of brake dust through the chrome. As brakes are applied hot particles of brake material are thrown off and tend to be forced through the leading edge of the wheel spoke windows by airflow. These Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 00-03-10-002F > Apr > 11 > Wheels - Chrome Wheel Staining/Pitting/Corrosion > Page 2419 hot particles embed themselves in the chrome layer and create a small pit. If the material is allowed to sit on the wheel while it is exposed to moisture or salt, it will corrode the wheel beneath the chrome leaving a pit or small blister in the chrome. Heavy brake dust build-up should be removed from wheels by using GM Chrome Cleaner and Polish, P/N 1050173 (in Canada use 10953013). For moderate cleaning, light brake dust build-up or water spots use GM Swirl Remover Polish, P/N 12377965 (in Canada, use Meguiars Plast-X(TM) Clear Plastic Cleaner and Polish #G12310C**). After cleaning, the wheel should be waxed using GM Cleaner Wax, P/N 12377966 (in Canada, use Meguiars Cleaner Wax #M0616C**), which will help protect the wheel from brake dust and reduce adhesion of any brake dust that gets on the wheel surface. For general maintenance cleaning, PEEK Metal Polish† may be used. It will clean and shine the chrome and leave behind a wax coating that may help protect the finish. Warranty of Stardust Corroded Chrome Wheels Wheels returned with pitting or spotting as a result of neglect and brake dust build-up may be replaced one time. Important Notify the customer that this is a one time replacement. Please stress to the customer the vital importance of keeping the wheels clean and free of prolonged exposure to brake dust build-up. "GM of Canada" dealers require prior approval by the District Manager - Customer Care and Service Process (DM-CCSP). Customer Assistance and Instructions GM has looked for ways customers may improve the appearance of wheels damaged by acidic cleaners. The following product and procedure has been found to dramatically improve the appearance of stained wheels. For wheels that have milky stains caused by acidic cleaners try the following: Notice THE 3M CHROME AND METAL POLISH REQUIRED FOR THIS PROCEDURE IS AN EXTREMELY AGGRESSIVE POLISH/CLEANER. THE WHEELS MUST BE CLEANED BEFORE APPLICATION TO AVOID SCRATCHING THE WHEEL SURFACE. THIS PRODUCT WILL REDUCE THE THICKNESS OF THE CHROME PLATING ON THE WHEEL AND IF USED INCORRECTLY OR EXCESSIVELY MAY REMOVE THE CHROME PLATING ALL TOGETHER, EXPOSING A LESS BRIGHT AND BRASSY COLORED SUB-LAYER. FOLLOW INSTRUCTIONS EXACTLY. 1. Wash the wheels with vigorously with soap and water. This step will clean and may reduce wheel staining. Flood all areas of the wheel with water to rinse. 2. Dry the wheels completely. Notice Begin with a small section of the wheel and with light pressure buff off polish and examine results. ONLY apply and rub with sufficient force and time to remove enough staining that you are satisfied with the results. Some wheels may be stained to the extent that you may only achieve a 50% improvement while others may be able to be restored to the original lustre. IN ALL CASES, only apply until the results are satisfactory. 3. Apply 3M Chrome and Metal Polish #39527* with a clean terry cloth towel. As you apply the polish, the staining will be diminished. 4. When dry, buff off the polish with a clean portion of the towel. 5. Repeat application of the 3M Chrome and Metal Polish until satisfied with the results. If continued applications fail to improve the appearance further discontinue use. This procedure will improve the appearance of the wheels and may, with repeated applications, restore the finish dramatically. For wheels that exhibit spotting from road chemicals the above procedure may marginally improve the condition but will not restore the finish or remove the pitting. In this type of staining the wheel finish has actually been removed in spots and no manner of cleaning will restore the finish. †*We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Parts Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 00-03-10-002F > Apr > 11 > Wheels - Chrome Wheel Staining/Pitting/Corrosion > Page 2420 *This product is currently available from 3M. To obtain information for your local retail location please call 3M at 1-888-364-3577. **This product is currently available from Meguiars (Canada). To obtain information for your local retail location please call Meguiars at 1-800-347-5700 or at www.meguiarscanada.com. ^ This product is currently available from Tri-Peek International. To obtain information for your local retail location please call Tri-Peek at 1-877-615-4272 or at www.tripeek.com. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 99-08-51-007E > Mar > 11 > Wheels/Tires - Refinishing Aluminum Wheels Wheels: All Technical Service Bulletins Wheels/Tires - Refinishing Aluminum Wheels INFORMATION Bulletin No.: 99-08-51-007E Date: March 17, 2011 Subject: Refinishing Aluminum Wheels Models: 2012 and Prior GM Passenger Cars and Trucks Supercede: This bulletin is being revised to add additional model years. Please discard Corporate Bulletin Number 99-08-51-007D (Section 08 - Body and Accessories). This bulletin updates General Motor's position on refinishing aluminum wheels. GM does not endorse any repairs that involve welding, bending, straightening or re-machining. Only cosmetic refinishing of the wheel's coatings, using recommended procedures, is allowed. Evaluating Damage In evaluating damage, it is the GM Dealer's responsibility to inspect the wheel for corrosion, scrapes, gouges, etc. The Dealer must insure that such damage is not deeper than what can be sanded or polished off. The wheel must be inspected for cracks. If cracks are found, discard the wheel. Any wheels with bent rim flanges must not be repaired or refinished. Wheels that have been refinished by an outside company must be returned to the same vehicle. The Dealer must record the wheel ID stamp or the cast date on the wheel in order to assure this requirement. Refer to Refinisher's Responsibility - Outside Company later in this bulletin. Aluminum Wheel Refinishing Recommendations - Chrome-plated aluminum wheels Re-plating these wheels is not recommended. - Polished aluminum wheels These wheels have a polyester or acrylic clearcoat on them. If the clearcoat is damaged, refinishing is possible. However, the required refinishing process cannot be performed in the dealer environment. Refer to Refinisher's Responsibility - Outside Company later in this bulletin. - Painted aluminum wheels These wheels are painted using a primer, color coat, and clearcoat procedure. If the paint is damaged, refinishing is possible. As with polished wheels, all original coatings must be removed first. Media blasting is recommended. Refer to GM Aluminum Refinishing Bulletin #53-17-03A for the re-painting of this type of wheel. - Bright, machined aluminum wheels These wheels have a polyester or acrylic clearcoat on them. In some cases, the recessed "pocket" areas of the wheel may be painted. Surface refinishing is possible. The wheel must be totally stripped by media blasting or other suitable means. The wheel should be resurfaced by using a sanding process rather than a machining process. This allows the least amount of material to be removed. Important Do not use any re-machining process that removes aluminum. This could affect the dimensions and function of the wheel. Painting is an option to re-clearcoating polished and bright machined aluminum wheels. Paint will better mask any surface imperfections and is somewhat more durable than clearcoat alone. GM recommends using Corsican SILVER WAEQ9283 for a fine "aluminum-like" look or Sparkle SILVER WA9967 for a very bright look. As an option, the body color may also be used. When using any of the painting options, it is recommended that all four wheels be refinished in order to maintain color uniformity. Refer to GM Aluminum Refinishing Bulletin #53-17-03A for specific procedures and product recommendations. Refinisher's Responsibility - Outside Company Important Some outside companies are offering wheel refinishing services. Such refinished wheels will be permanently marked by the refinisher and are warranted by the refinisher. Any process that re-machines or otherwise re-manufactures the wheel should not be used. A refinisher's responsibility includes inspecting for cracks using the Zyglo system or the equivalent. Any cracked wheels must not be refinished. No welding, hammering or reforming of any kind is allowed. The wheel ID must be recorded and follow the wheel throughout the process in order to assure that the same wheel is returned. A plastic media blast may be used for clean up of the wheel. Hand and/or lathe sanding of the machined surface and the wheel window is allowed. Material removal, though, must be kept to a minimum. Re-machining of the wheel is not allowed. Paint and/or clear coat must not be present on the following surfaces: the nut chamfers, the wheel mounting surfaces and the wheel pilot hole. The refinisher must permanently ID stamp the wheel and warrant the painted/clearcoated surfaces for a minimum of one year or the remainder of the new vehicle warranty, whichever is Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 99-08-51-007E > Mar > 11 > Wheels/Tires - Refinishing Aluminum Wheels > Page 2425 longer. Important Whenever a wheel is refinished, the mounting surface and the wheel nut contact surfaces must not be painted or clearcoated. Coating these surfaces could affect the wheel nut torque. When re-mounting a tire on an aluminum wheel, coated balance weights must be used in order to reduce the chance of future cosmetic damage. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 06-03-10-010A > Jun > 10 > Wheels - Changing Procedures/Precautions Wheels: All Technical Service Bulletins Wheels - Changing Procedures/Precautions INFORMATION Bulletin No.: 06-03-10-010A Date: June 09, 2010 Subject: Information on Proper Wheel Changing Procedures and Cautions Models: 2011 and Prior GM Passenger Cars and Trucks 2010 and Prior HUMMER Models 2005-2009 Saab 9-7X 2005-2009 Saturn Vehicles Attention: Complete wheel changing instructions for each vehicle line can be found under Tire and Wheel Removal and Installation in Service Information (SI). This bulletin is intended to quickly review and reinforce simple but vital procedures to reduce the possibility of achieving low torque during wheel installation. Always refer to SI for wheel lug nut torque specifications and complete jacking instructions for safe wheel changing. Supercede: This bulletin is being revised to include the 2011 model year and update the available special tool list. Please discard Corporate Bulletin Number 06-03-10-010 (Section 03 Suspension). Frequency of Wheel Changes - Marketplace Driven Just a few years ago, the increasing longevity of tires along with greater resistance to punctures had greatly reduced the number of times wheels were removed to basically required tire rotation intervals. Today with the booming business in accessory wheels/special application tires (such as winter tires), consumers are having tire/wheel assemblies removed - replaced - or installed more than ever. With this increased activity, it opens up more of a chance for error on the part of the technician. This bulletin will review a few of the common concerns and mistakes to make yourself aware of. Proper Servicing Starts With the Right Tools The following tools have been made available to assist in proper wheel and tire removal and installation. - J 41013 Rotor Resurfacing Kit (or equivalent) - J 42450-A Wheel Hub Resurfacing Kit (or equivalent) Corroded Surfaces One area of concern is corrosion on the mating surfaces of the wheel to the hub on the vehicle. Excessive corrosion, dirt, rust or debris built up on these surfaces can mimic a properly tightened wheel in the service stall. Once the vehicle is driven, the debris may loosen, grind up or be washed away from water splash. This action may result in clearance at the mating surface of the wheel and an under-torqued condition. Caution Before installing a wheel, remove any buildup on the wheel mounting surface and brake drum or brake disc mounting surface. Installing wheels with poor metal-to-metal contact at the mounting surfaces can cause wheel nuts to loosen. This may cause a wheel to come off when the vehicle is moving, possibly resulting in a loss of control or personal injury. Whenever you remove the tire/wheel assemblies, you must inspect the mating surfaces. If corrosion is found, you should remove the debris with a die grinder equipped with a fine sanding pad, wire brush or cleaning disc. Just remove enough material to assure a clean, smooth mating surface. The J 41013 (or equivalent) can be used to clean the following surfaces: - The hub mounting surface - The brake rotor mounting surface - The wheel mounting surface Use the J 42450-A (or equivalent) to clean around the base of the studs and the hub. Lubricants, Grease and Fluids Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 06-03-10-010A > Jun > 10 > Wheels - Changing Procedures/Precautions > Page 2430 Some customers may use penetrating oils, grease or other lubricants on wheel studs to aid in removal or installation. Always use a suitable cleaner/solvent to remove these lubricants prior to installing the wheel and tire assemblies. Lubricants left on the wheel studs may cause improper readings of wheel nut torque. Always install wheels to clean, dry wheel studs ONLY. Notice Lubricants left on the wheel studs or vertical mounting surfaces between the wheel and the rotor or drum may cause the wheel to work itself loose after the vehicle is driven. Always install wheels to clean, dry wheel studs and surfaces ONLY. Beginning with 2011 model year vehicles, put a light coating of grease, GM P/N 1051344 (in Canada, P/N 9930370), on the inner surface of the wheel pilot hole to prevent wheel seizure to the axle or bearing hub. Wheel Stud and Lug Nut Damage Always inspect the wheel studs and lug nuts for signs of damage from crossthreading or abuse. You should never have to force wheel nuts down the stud. Lug nuts that are damaged may not retain properly, yet give the impression of fully tightening. Always inspect and replace any component suspected of damage. Tip Always start wheel nuts by hand! Be certain that all wheel nut threads have been engaged BEFORE tightening the nut. Important If the vehicle has directional tread tires, verify the directional arrow on the outboard side of the tire is pointing in the direction of forward rotation. Wheel Nut Tightening and Torque Improper wheel nut tightening can lead to brake pulsation and rotor damage. In order to avoid additional brake repairs, evenly tighten the wheel nuts to the proper torque specification as shown for each vehicle in SI. Always observe the proper wheel nut tightening sequence as shown below in order to avoid trapping the wheel on the wheel stud threads or clamping the wheel slightly off center resulting in vibration. The Most Important Service You Provide While the above information is well known, and wheel removal so common, technicians run the risk of becoming complacent on this very important Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 06-03-10-010A > Jun > 10 > Wheels - Changing Procedures/Precautions > Page 2431 service operation. A simple distraction or time constraint that rushes the job may result in personal injury if the greatest of care is not exercised. Make it a habit to double check your work and to always side with caution when installing wheels. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 04-03-10-012B > Feb > 08 > Wheels - Chrome Wheel Brake Dust Accumulation/Pitting Wheels: All Technical Service Bulletins Wheels - Chrome Wheel Brake Dust Accumulation/Pitting Bulletin No.: 04-03-10-012B Date: February 01, 2008 INFORMATION Subject: Pitting and Brake Dust on Chrome wheels Models: 2008 and Prior GM Passenger Cars and Trucks (including Saturn) 2008 and Prior HUMMER H2, H3 2005-2008 Saab 9-7X Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 04-03-10-012A (Section 03 - Suspension). Analysis of Returned Wheels Chrome wheels returned under the New Vehicle Limited Warranty for pitting concerns have recently been evaluated. This condition is usually most severe in the vent (or window) area of the front wheels. This "pitting" may actually be brake dust that has been allowed to accumulate on the wheel. The longer this accumulation builds up, the more difficult it is to remove. Cleaning the Wheels In all cases, the returned wheels could be cleaned to their original condition using GM Vehicle Care Cleaner Wax, P/N 12377966 (in Canada, P/N 10952905). When using this product, you should confine your treatment to the areas of the wheel that show evidence of the brake dust build-up. This product is only for use on chromed steel or chromed aluminum wheels. Parts Information Warranty Information Wheel replacement for this condition is NOT applicable under the terms of the New Vehicle Limited Warranty. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 99-03-10-102 > Jun > 99 > Warranty - OE Chrome Plated Aluminum Wheel ID Wheels: All Technical Service Bulletins Warranty - OE Chrome Plated Aluminum Wheel ID File In Section: 03 - Suspension Bulletin No.: 99-03-10-102 Date: June, 1999 INFORMATION Subject: Original Equipment Chrome Plated Aluminum Wheel Identification Models: 1999 and Prior Passenger Cars and Light Duty Trucks Chrome plated aluminum wheels have been returned to the Warranty Parts Center that are not the original equipment (OE) components. Original equipment chrome plated aluminum wheels can be identified by either a balance weight clip retention groove (1) or a step (2) that is machined around both of the wheel's rim flanges. The rim flanges (3) of painted original equipment aluminum wheels do not have a groove or a step. Chrome plated aluminum wheels that do not have the wheel rim flange groove or step are aftermarket chrome plated components and are NOT warrantable. Any aftermarket chrome wheels received by the Warranty Parts Center will be charged back to the dealership. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 72-05-05 > Aug > 97 > Warranty - Guidelines for Using E0420 Wheel Replace Wheels: All Technical Service Bulletins Warranty - Guidelines for Using E0420 Wheel Replace File In Section: Warranty Administration Bulletin No.: 72-05-05 Date: August, 1997 WARRANTY ADMINISTRATION Subject: Guidelines for Using EO42O Wheel Replace Models: 1989-98 Passenger Cars and Light Duty Trucks The purpose of this bulletin is to provide service personnel with guidelines for using the above subject labor operation. Effective with repair orders dated on or after September 1, 1997, dealers are to be guided by the following: ^ Aluminum Wheels (including chrome plated) with Porosity - Wheels that exhibit porosity should be repaired as described in the vehicle service manual. Wheels should not be replaced without wholesale approval. ^ Aluminum Wheels (except chrome plated) with a "Finish Defect" - Wheels that exhibit a defect in the finish, (i.e., discoloration or surface degradation) should be refinished as described in the Corporate Service Bulletin Number 53-17-03A released in May, 1996. ^ Chrome Wheels - Wheels that are chromed and found to have a finish defect can only be replaced. ^ Aluminum and chrome wheels replaced under warranty will be subject to random part review and inspection. Those wheels inspected and found not to be defective and/or should have been repaired, will be subject to charge back. Wheels damaged by normal wear, road hazards, car wash brushes, or other physical or chemical damage are not eligible for warranty coverage. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 531703A > May > 96 > Aluminum Wheels - Refinishing Technical Service Bulletin # 531703A Date: 960501 Aluminum Wheels - Refinishing File In Section: 10 - Body Bulletin No.: 53-17-03A Date: May, 1996 INFORMATION Subject: Aluminum Wheel Refinishing Models: 1991-96 Passenger Cars and Trucks This bulletin is being revised to delete the 1990 model year and add the 1996 model year. Please discard Corporate Bulletin Number 53-17-03 (Section 10 - Body). This bulletin supersedes and cancels all previous service bulletins concerning the refinishing of aluminum wheels. The purpose of this service bulletin is to assist dealerships in repairing the discoloration or surface degradation that has occurred on styled aluminum wheels. This bulletin provides NEW PROCEDURES AND SPECIFIC MATERIALS for the refinishing of painted aluminum wheels or aluminum wheels with discoloration or surface degradation. Important: THE RE-MACHINING OF ALUMINUM WHEELS IS NOT RECOMMENDED. THE RE-CLEAR COATING OF ALUMINUM WHEELS IS NO LONGER RECOMMENDED DUE TO CONCERNS OF REPAIR DURABILITY The new procedure requires the wheel surface be plastic media blasted to remove old paint or clear coat. CHEMICAL STRIPPERS ARE NOT RECOMMENDED. Material Required System 1: DuPont Products 3939-S Cleaning Solvent 615/616 Etching Primer URO 5000 Primer Surfacer IMRON 6000 Basecoat 3440-S IMRON Clear System 2: PPG Products DX533 Aluminum Cleaner DX503 Aluminum Conditioner DP Epoxy Primer Deltron Basecoat (DBC) Concept 2001 Clear Acrylic Urethane System 3: Spies Hecker Permahyd Silicone Remover 7090 Permahyd 1:1 Primer 4070 Permahyd 2:1 Surfacer 5080 Permahyd Base Coat Series 280/285 Permahyd H.S. Clearcoat 8060 Color Selection If the wheels being painted were previously clearcoated aluminum, we would recommend using Corsican SILVER WAEQ9283 for a fine "aluminum-like" look or Sparkle SILVER WA9967 for a very bright look. As an option to the customer, you may also use body color. For color Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 531703A > May > 96 > Aluminum Wheels - Refinishing > Page 2448 selection and verification, refer to your paint manufacturer's color book. On wheels that were previous clearcoated aluminum it is recommended that all four wheels and their center caps be refinished to maintain color uniformity. Important: THE PRODUCTS LISTED MUST BE USED AS A SYSTEM. DO NOT MIX OTHER MANUFACTURERS' PRODUCT LINES WITH THE REQUIRED MATERIALS. PRODUCTS LISTED IN THIS BULLETIN HAVE SHOWN THE REQUIRED REPAIR DURABILITY, AND CURRENTLY ARE THE ONLY PAINT SYSTEMS THAT MEET GM SPECIFICATION 4350M-A336. Procedures 1. Remove wheels from vehicle. Tires may remain mounted on wheels. 2. Remove balance weights and mark their location on tire. 3. Wipe excess grease, etc. from wheels with wax and grease remover. 4. Have wheels plastic media blasted to remove clearcoat. FOR FURTHER INFORMATION ON MEDIA BLASTING IN YOUR AREA, CALL US TECHNOLOGIES INC., CONTACT DAVE ROSENBURG AT 1-800-634-9185. Caution: IT IS MANDATORY THAT ADEQUATE RESPIRATORY PROTECTION BE WORN. EXAMPLES OF SUCH PROTECTION ARE: AIR LINE RESPIRATORS WITH FULL HOOD OR HALF MASK. IF NOT AVAILABLE, USE A VAPOR/PARTICULATE RESPIRATOR THAT RESPIRATOR MANUFACTURER RECOMMENDS AS EFFECTIVE FOR ISOCYANATE VAPOR AND MISTS (UNLESS LOCAL REGULATIONS PREVAIL). 5. Painting Process a. Refer to Attachments 1-3 for each System's individual formula and process. b. After following the specific System's individual formula and process, follow these steps: 6. Unmask wheels. 7. Clean all wheel mounting surface of any corrosion, overspray, or dirt. 8. Install new coated balance weights, at marked locations. 9. Replace wheels on vehicle. 10. USE A TORQUE STICK ON AN IMPACT WRENCH, OR A TORQUE WRENCH TO CONSISTENTLY AND UNIFORMLY FASTEN THE WHEEL TO THE SPECIFIED TORQUE FOR THE VEHICLE. THE STAR PATTERN MUST BE FOLLOWED. Important: TORQUE STICKS MUST BE USED ANY TIME AN IMPACT WRENCH IS USED TO TIGHTEN WHEEL NUTS. Warranty Information For vehicles repaired under warranty, use as shown. Attachment 1 - DuPont Products Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 531703A > May > 96 > Aluminum Wheels - Refinishing > Page 2449 Painting Process System: Dupont Products Paint Color Information: Corsican Silver WA EQ9283 Dupont # C9143, Sparkle Silver WA9967 Dupont # C9339 1. Wipe wheel with cleaning solvent: 3939-S, 3949-S or 3900-S. 2. Mask off tires. Important: 3. Mask off all wheel mounting surfaces and wheel mount surfaces. 4. Apply two coats of 615/616-S etching primer to wheel allowing 10 minutes flash between coats. Allow to dry for 30 minutes before applying primer coat. 5. Apply URO 5000 primer 1220/193-S + accelerator 389-S using two coats at 65-70 PSI at the gun. Allow 12-15 minutes between coats. Force bake 30 minutes at 140°F (60°C). 6. Scuff sand using green Scotch-Brite pad. 7. Solvent wipe before top coating. 8. Apply IMRON 6000 base coat to wheel. 2-3 coats to hiding at 60-70 PSI allowing to flash between coats. Base coat needs to dry 20-30 minutes before clearcoat is applied. 9. Apply 3440-S clearcoat to wheel using two coats at 60-70 PSI. Flash 10-15 minutes between coats. 389-S can be used in basecoat and clearcoat to give faster set up times. 10. Allow overnight dry before reassemble. Can be baked for 30 minutes at 140°F (60°C). Attachment 2 - PPG Products Painting Process: PPG System Paint Color Information: Corsican Silver WAEQ9283; PPG # DBC-3531, Sparkle Silver WA9967; PPG # 35367 1. Wash entire wheel with aluminum cleaner DX533, mix 1:3 with water. Allow to react 2-3 minutes and rinse thoroughly. 2. Wash entire wheel with aluminum conditioner DX5O3 straight from the container. Allow to react 2-3 minutes until pale gold or tan color develops. Rinse thoroughly and dry. 3. Mask off tires. Important: 4. Mask off all wheel nut mounting surfaces and wheel mounting surfaces. 5. Apply 1-2 coats of DP Primer and allow to flash for 15-20 minutes. 6. Apply 2-3 coats of Deltron Basecoat (DBC) and allow to flash 20 minutes after the final coat. 7. Apply two (2) wet coats of Concept 2001 Acrylic urethane. 8. Flash 20 minutes and bake 140°F (60°C) for 30 minutes. For more information contact your PPG Jobber. Attachment 3 - Spies Hecker Painting Process: Spies Hecker System Paint Color Information: Corsican Silver AWEQ9283; SH-72913, Sparkle Silver WA9967; SH-71912 1. Clean with Permahyd Silicone Remover 7090. 2. Mask off tires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 531703A > May > 96 > Aluminum Wheels - Refinishing > Page 2450 Important: 3. Mask off all wheel nut mounting surfaces and wheel mounting surfaces. 4. Apply 1-1/2 coats of Permahyd 1:1 Primer 4070. Mix 1:1 with Permahyd Hardener 3070 as per TDS. 5. Allow to flash for 30 minutes. 6. Apply two (2) coats of Permahyd 2:1 Surfacer 5080. Mix 2:1 with Permahyd Hardener 3071 as per TDS. 7. Bake for 60 minutes at 140°F (60°C) or allow to flash for 3 hours at 68°F (20°C). 8. Apply Permahyd Base Coat Series 280/285 as per TDS. 9. Allow to flash 10 to 15 minutes. 10. Apply 1 to 2 coats of Permacron High Solid Clear Coat 8060 as per TDS. 11. Allow to flash 10 minutes. Then bake at 140°F (60°C) for 40 minutes. For more information, contact your SPIES HECKER Jobber. We believe these sources and their products to be reliable. There may be additional manufacturers of such products. General Motors does not endorse, indicate any preference for or assume any responsibility for the products or equipment from these firms or for any such items which may be available from other sources. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheel Bearing > Component Information > Adjustments > Front Wheel Bearing: Adjustments Front FRONT WHEEL BEARINGS ADJUSTMENT Fig. 5 Hub, knuckle & bearing components. REMOVE 1. Raise and support vehicle. 2. Remove wheel cover, if equipped. 3. Remove cap from hub/disc assembly. 4. Remove cotter pin. 5. Tighten nut (12), Fig. 5, to 12 ft lbs, while turning wheel forward by hand. This will seat the bearing. 6. Loosen nut (12) to a just loose position, then back nut off until hole in the spindle aligns with a slot in the nut. Do not back the nut off more than 1/2 flat. INSTALL 1. New cotter pin. With wheel bearing properly adjusted, there will be .001---.005 inch endplay. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheel Bearing > Component Information > Adjustments > Front > Page 2455 Wheel Bearing: Adjustments Rear Dana/Spicer Full Floating Axle REAR WHEEL BEARINGS ADJUSTMENT Ensure the brakes are completely released and do not drag. Check wheel bearing play by grasping the tire at the top and pulling and pushing back and forth, or by using a pry bar under the tire. If the wheel bearings are properly adjusted, movement of the brake drum in relation to the brake flange plate will be barely noticeable and the wheel will turn freely. If the movement is excessive, adjust the bearings as follows: 1. Back off attaching nut until just loose, but not more than one slot of the lock or the axle spindle using wheel bearing nut wrench tool No. J-2222-C or equivalent. 2. Align adjusting nut slot with keyway in the axle spindle. Rockwell Full Floating Axle REAR WHEEL BEARINGS ADJUSTMENT Ensure the brakes are completely released and do not drag. Check wheel bearing play by grasping the tire at the top and pulling and pushing back and forth, or by using a pry bar under the tire. If the wheel bearings are properly adjusted, movement of hub or disc will be barely noticeable. If the movement is excessive, adjust the bearings as follows: 1. Raise and support vehicle. 2. Remove axle shaft. 3. Remove retaining nut and lock washer. 4. Using nut wrench tool No. J-25510, or equivalent, torque adjusting nut, with hub rotating, to 50.0 ft. lbs. Ensure bearing surfaces are in contact, then back adjusting nut off 1/8 turn. 5. Install lock washer, the bend tang over flat of adjusting nut. 6. Install retaining nut and torque to 250 ft. lbs. 7. Install axle shaft. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheel Bearing > Component Information > Service and Repair > Front Wheel Bearing: Service and Repair Front FRONT WHEEL BEARINGS AND/OR HUB Fig. 5 Hub, knuckle & bearing components. REMOVE 1. Disconnect battery ground cable. 2. Raise and support vehicle, then remove brake caliper. 3. Remove cap from hub/disc assembly, Fig. 5. 4. Remove cotter pin, nut and washer. 5. Remove hub/disc from spindle. 6. Remove outer bearing, seal, inner bearing and cup. INSTALL 1. Reverse procedure to install. Note the following: a. Clean all components before installing. b. Apply an approved high temperature front wheel bearing grease to the spindle at the inner and outer bearing seat, shoulder and seal seat. Also finger apply a small amount of grease inboard of each bearing cup in the hub/disc assembly. Pressure pack the bearings with a grease machine or hand pack them. Ensure grease is worked thoroughly into the rollers, cone and cage. c. When installing inner bearing, apply an additional quantity of grease outboard of the inner bearing. d. Torque nut (12) 10-12 ft lbs while turning the wheel assembly forward by hand. Apply grease to the outboard side of the outer bearing. Adjust wheel bearings. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheel Bearing > Component Information > Service and Repair > Front > Page 2458 Wheel Bearing: Service and Repair Rear REAR WHEEL BEARINGS 1. Raise and support vehicle. 2. Remove axle shaft. 3. Remove hub and drum. 4. Remove oil seal, inner bearing and retaining ring. 5. Remove outer bearing. 6. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheel Hub > Component Information > Service and Repair Wheel Hub: Service and Repair FRONT HUB/BEARING Fig. 5 Hub, knuckle & bearing components. REMOVE 1. Disconnect battery ground cable. 2. Raise and support vehicle, then remove brake caliper. 3. Remove cap from hub/disc assembly, Fig. 5. 4. Remove cotter pin, nut and washer. 5. Remove hub/disc from spindle. 6. Remove outer bearing, seal, inner bearing and cup. INSTALL 1. Reverse procedure to install. Note the following: a. Clean all components before installing. b. Apply an approved high temperature front wheel bearing grease to the spindle at the inner and outer bearing seat, shoulder and seal seat. Also finger apply a small amount of grease inboard of each bearing cup in the hub/disc assembly. Pressure pack the bearings with a grease machine or hand pack them. Ensure grease is worked thoroughly into the rollers, cone and cage. c. When installing inner bearing, apply an additional quantity of grease outboard of the inner bearing. d. Torque nut (12) 10-12 ft lbs while turning the wheel assembly forward by hand. Apply grease to the outboard side of the outer bearing. Adjust wheel bearings. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheel Fastener > Component Information > Technical Service Bulletins > Customer Interest for Wheel Fastener: > 01-03-10-009A > Jul > 04 > Wheels - Plastic Wheel Nut Covers Loose/Missing Wheel Fastener: Customer Interest Wheels - Plastic Wheel Nut Covers Loose/Missing Bulletin No.: 01-03-10-009A Date: July 27, 2004 TECHNICAL Subject: Plastic Wheel Nut Covers Missing and/or Loose (Replace Missing Covers and Add Sealant to All Covers) Models: 2005 and All Prior Passenger Cars (Except All Cadillac Models and Pontiac GTO) with Plastic Wheel Nut Covers Supercede: This bulletin is being revised to add additional models years. Please discard Corporate Bulletin Number 01-03-10-009. Condition Some customers may comment that the plastic wheel nut covers are missing and/or loose. Correction Important: ^ DO NOT USE a silicone-based adhesive. ^ Do not apply the *permatex(R) around the threads in a circular pattern. ^ Apply a single bead across the threads approximately 10 mm (0.4 in) in length, 5 mm (0.2 in) in height and 5 mm (0.2 in) in width. Replace any missing plastic wheel nut covers with the appropriate covers and apply Permatex(R) # 2 Form A Gasket Sealant(R) to the threads of all the plastic wheel nut covers. Tighten finger tight plus a 1/4 turn with a hand wrench. *We believe this source and their products to be reliable. There may be additional manufacturers of such material. General Motors does not endorse, indicate any preference for or assume any responsibility for the products from this firm or for any other such items which may be available from other sources. Permatex(R) # 2 Form A Gasket Sealant(R) part numbers (available at your local parts supplier) ^ P/N 80009 (2A/2AR) - 44 ml (1.5 oz) tube boxed ^ P/N 80015 (2AR) - 44 ml (1.5 oz) tube carded ^ P/N 80010 (2B/2BR) - 89 ml (3 oz) tube boxed ^ P/N 80016 (2BR) - 89 ml (3 oz) tube carded ^ P/N 80011 (2C) - 325 ml (11 oz) tube boxed Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheel Fastener > Component Information > Technical Service Bulletins > Customer Interest for Wheel Fastener: > 01-03-10-009A > Jul > 04 > Wheels - Plastic Wheel Nut Covers Loose/Missing > Page 2470 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheel Fastener > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheel Fastener: > 01-03-10-009A > Jul > 04 > Wheels - Plastic Wheel Nut Covers Loose/Missing Wheel Fastener: All Technical Service Bulletins Wheels - Plastic Wheel Nut Covers Loose/Missing Bulletin No.: 01-03-10-009A Date: July 27, 2004 TECHNICAL Subject: Plastic Wheel Nut Covers Missing and/or Loose (Replace Missing Covers and Add Sealant to All Covers) Models: 2005 and All Prior Passenger Cars (Except All Cadillac Models and Pontiac GTO) with Plastic Wheel Nut Covers Supercede: This bulletin is being revised to add additional models years. Please discard Corporate Bulletin Number 01-03-10-009. Condition Some customers may comment that the plastic wheel nut covers are missing and/or loose. Correction Important: ^ DO NOT USE a silicone-based adhesive. ^ Do not apply the *permatex(R) around the threads in a circular pattern. ^ Apply a single bead across the threads approximately 10 mm (0.4 in) in length, 5 mm (0.2 in) in height and 5 mm (0.2 in) in width. Replace any missing plastic wheel nut covers with the appropriate covers and apply Permatex(R) # 2 Form A Gasket Sealant(R) to the threads of all the plastic wheel nut covers. Tighten finger tight plus a 1/4 turn with a hand wrench. *We believe this source and their products to be reliable. There may be additional manufacturers of such material. General Motors does not endorse, indicate any preference for or assume any responsibility for the products from this firm or for any other such items which may be available from other sources. Permatex(R) # 2 Form A Gasket Sealant(R) part numbers (available at your local parts supplier) ^ P/N 80009 (2A/2AR) - 44 ml (1.5 oz) tube boxed ^ P/N 80015 (2AR) - 44 ml (1.5 oz) tube carded ^ P/N 80010 (2B/2BR) - 89 ml (3 oz) tube boxed ^ P/N 80016 (2BR) - 89 ml (3 oz) tube carded ^ P/N 80011 (2C) - 325 ml (11 oz) tube boxed Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheel Fastener > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheel Fastener: > 01-03-10-009A > Jul > 04 > Wheels - Plastic Wheel Nut Covers Loose/Missing > Page 2476 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheel Fastener > Component Information > Technical Service Bulletins > Page 2477 Wheel Fastener: Specifications Wheel Stud Nut Wheel Stud Nut Vehicles with 5 Lugs 140 ft.lb Vehicles with 6 Lugs 140 ft.lb Vehicles with 8 Lugs 140 ft.lb Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Wheels and Tires > Wheel Seal > Component Information > Service and Repair Wheel Seal: Service and Repair Fig. 5 Hub, knuckle & bearing components. REMOVE 1. Disconnect battery ground cable. 2. Raise and support vehicle, then remove brake caliper. 3. Remove cap from hub/disc assembly, Fig. 5. 4. Remove cotter pin, nut and washer. 5. Remove hub/disc from spindle. 6. Remove outer bearing, seal, inner bearing and cup. INSTALL 1. Reverse procedure to install. Note the following: a. Clean all components before installing. b. Apply an approved high temperature front wheel bearing grease to the spindle at the inner and outer bearing seat, shoulder and seal seat. Also finger apply a small amount of grease inboard of each bearing cup in the hub/disc assembly. Pressure pack the bearings with a grease machine or hand pack them. Ensure grease is worked thoroughly into the rollers, cone and cage. c. When installing inner bearing, apply an additional quantity of grease outboard of the inner bearing. d. Torque nut (12) 10-12 ft lbs while turning the wheel assembly forward by hand. Apply grease to the outboard side of the outer bearing. Adjust wheel bearings. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Maintenance > Vehicle Lifting > Component Information > Service and Repair Vehicle Lifting: Service and Repair Fig. 12 Vehicle Lift Points. Fig. 12 Vehicle Lift Points. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Compression Check > System Information > Specifications Compression Check: Specifications Minimum, 698 kPa (100 psi) @ 200 rpm. The lowest cylinder reading should not be less than 80% of the highest. Perform compression test with engine at normal operating temperature, spark plugs removed and throttle wide open. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Camshaft, Lifters and Push Rods > Camshaft, Engine > Component Information > Specifications Camshaft: Specifications Engine Liter/CID .................................................................................................................................. ............................................................. 5.7L/V8-350 All specifications given in inches. Camshaft Journal Diameter ................................................................................................................. ............................................................ 1.8677-1.8697 Camshaft Endplay .......................................... ................................................................................................................................................. 0.0040-0.0120 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Camshaft, Lifters and Push Rods > Camshaft, Engine > Component Information > Specifications > Page 2493 Camshaft: Service and Repair Depending on vehicle and engine application, the grille, radiator and condenser, may need to be removed before removing the camshaft. 1. Remove intake manifold. 2. Remove pushrods and valve lifters. 3. Remove Front Cover. Then the distributor. 4. Remove camshaft sprocket bolts and timing chain. 5. Remove camshaft sprocket. 6. Install two 5/16 18 x 4-5 inch bolts into camshaft bolt holes, then pull camshaft out of cylinder block. 7. Reverse procedure to install. 8. Tighten camshaft sprocket bolts to specifications. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Camshaft, Lifters and Push Rods > Push Rod > Component Information > Service and Repair Push Rod: Service and Repair When a replacement pushrod has a paint stripe at one end, this painted end must be installed in contact with the rocker arm. To provide durability a hardened insert is incorporated in the rocker arm end of these pushrods. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Camshaft, Lifters and Push Rods > Rocker Arm Assembly > Component Information > Service and Repair Rocker Arm Assembly: Service and Repair Rocker arm stud removal Rocker arm stud installation Remove the old stud by placing a suitable spacer over the stud, Fig. 13. Install a nut and flat washer on the stud and pull out the stud by turning the nut. After reaming the hole for an oversize stud, coat the press-fit area of the new stud with rear axle lubricant. Install the stud using stud driver tool No. 6880, or equivalent, by driving it in until tool bottoms on the head, Fig.14. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Block Assembly > Connecting Rod Bearing > Component Information > Technical Service Bulletins > Connecting Rod Bearing - Clearance Checking Tool Connecting Rod Bearing: Technical Service Bulletins Connecting Rod Bearing - Clearance Checking Tool BULLETIN NUMBER: 00-06-01-007 SECTION: 06 - Engine/Propulsion System DATE: March 2000 INFORMATION SUBJECT: Essential Tool J 43690 - Rod Bearing Clearance Checking Tool MODELS: 1999-2000 Cadillac Escalade 1996-2000 Chevrolet and GMC C/K, M/L, S/T, G and P Models 1996-2000 Oldsmobile Bravada with 4.3L, 5.0L or 5.7L Engine (VINs W, M, R - RPOs L35, L30, L31) A new service tool J 43690 and the supporting service procedure have been developed to more accurately measure connecting rod bearing clearances. Engines with excessive connecting rod bearing clearances may exhibit a cold knock/bearing rattle type noise (refer to Corporate Bulletin Number 99-06-01-003). Typically, this noise occurs at initial start-up and may be audible up to 1,500 - 1,800 RPM. The rod bearing knock typically diminishes or goes away at normal operating temperature. Tool J 43690 permits measurement of connecting rod bearing clearances without removing the connecting rod bolts, bearing cap, and bearings. The selective fitting of the connecting rod bearings is necessary in order to obtain close tolerances. For this reason, standard and undersized bearings are available. While the micrometer method of measuring for bearing clearances is acceptable, the use of J 43690 is the preferred method. The use of plastic gauging material will result in unreliable measurements and is not to be used. Follow the tool instructions included with the tool or the revised electronic service information. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Block Assembly > Connecting Rod Bearing > Component Information > Technical Service Bulletins > Page 2505 Connecting Rod Bearing: Specifications Connecting rod bearing inserts are available in standard size and undersizes of .001 inch, .002 inch, .010 inch and .020 inch. The bearings can be replaced without removing the rod assembly by removing the cap and replacing the upper and lower halves of the bearing. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Block Assembly > Connecting Rod, Engine > Component Information > Specifications Connecting Rod: Specifications Torque Specifications 45 ft.lb Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Block Assembly > Crankshaft Main Bearing > Component Information > Technical Service Bulletins > Engine - Bearing Knock Noise Technical Service Bulletin # 99-06-01-003 Date: 990401 Engine - Bearing Knock Noise File In Section: 06 - Engine/Propulsion System Bulletin No.: 99-06-01-003 Date: April, 1999 TECHNICAL Subject: Engine Bearing Knock Noise, (Re-support Crankshaft, Select-fit Undersize Connecting Rod Bearings) Models: 1999 Cadillac Escalade 1996-99 Chevrolet and GMC C/K, G, P Models with 5.0L or 5.7L Engine (VINs M, R - RPOs L30, L31) Important: GM Canada Dealers require prior DSM authorization to apply this bulletin. Condition Some customers may comment about an engine "knocking" noise. Cause A condition may exist in some engines where, the crankshaft is NOT being evenly supported by all five crankshaft bearing inserts. In these engines, the number 1, 2, 3, and 4 crankshaft bearing inserts are supporting the crankshaft, and the number 5 crankshaft journal (rear) has excessive clearance relative to the number 5 crankshaft (main) bearing cap insert. In this condition, the crankshaft flexes under load, and pounds on the lower number 5 crankshaft (main) bearing insert creating the knocking sound. The engines were originally built with 0.0006 in. undersize crankshaft (main) bearing inserts in the number 2, 3, and 4 crankshaft (main) bearing locations and 0.001 in. undersize insert in the number 5 crankshaft (main) bearing location. The service procedure listed below addresses the above condition by lowering the crankshaft at the number 2, 3, and 4 crankshaft (main) bearing positions (increased crankshaft (main) bearing size of the lower crankshaft (main) bearing inserts) and raising the number 5 lower crankshaft (main) bearing insert (undersized insert) in order to properly contact the number 5 crankshaft journal surface. These engines may also exhibit a connecting rod knocking sound. In these engines, the connecting rod knocking sound is caused by excessive connecting rod bearing clearance. A customer concern vehicle may exhibit one or both of the above stated conditions. Correction Follow strategy-based diagnostics for engine noise listed in the front of Section 6 of the Service Manual. Some additional key points: Rod Bearing Knock - Occurs on initial engine start-up, and can also be heard as high as 1,500-1,800 RPM. Rod bearing knock typically diminishes or completely goes away when the engine reaches normal operating temperature. Crankshaft Bearing Knock - Crankshaft (main) bearing knock sounds deeper in the engine and also sounds more muffled. There are two different types of crankshaft bearing knock. ^ Short duration cold knock typically occurs for 1-5 seconds on engine cold start-up only, and almost always occurs on vehicles equipped with an engine oil cooler. ^ Hot knock occurs less frequently, typically occurring in very hot ambient temperatures, and can be heard up to 2,000 RPM. Technicians can increase the likelihood of reproducing bearing induced knock sounds by slightly depressing the accelerator pedal while starting the engine. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Block Assembly > Crankshaft Main Bearing > Component Information > Technical Service Bulletins > Engine - Bearing Knock Noise > Page 2513 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J1150 Use published labor time Crankshaft Bearing Service Procedure Important: The repair procedure must be performed using all steps (addressing both the crankshaft bearings and connecting rod bearings) in order to ensure the effectiveness of the repair procedure. 1. Remove the oil pump. Refer to Oil Pump Replacement in Engine Mechanical section of the Vehicle Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Block Assembly > Crankshaft Main Bearing > Component Information > Technical Service Bulletins > Engine - Bearing Knock Noise > Page 2514 Important: Do not loosen or attempt to service the number 1 (front) crankshaft (main) bearing cap or the number 1 crankshaft (main) bearings. 2. Mark the number 2, 3, 4, and 5 crankshaft (main) bearing caps with position and direction. The crankshaft (main) bearing caps MUST be reinstalled in the original position and direction. 3. Support the crankshaft using a screw type jack and a block of wood. 3.1. Position the screw type jack and the block of wood at the center of the crankshaft in order to properly support the crankshaft. 3.2. Turn the screw of the screw type jack until the crankshaft is firmly seated against the crankshaft (main) upper bearings. 4. Remove the number 5 crankshaft (main) bearing cap bolts, and the number 5 crankshaft (main) bearing cap with the crankshaft (main) lower bearing. 5. Using green plastigauge (designed for measuring 0.001-0.003 in. of clearance), lay two pieces, 2 inches in length, laterally along the number 5 lower crankshaft (main) bearing, 1/4 inch inboard from the insert outer edges. Re-install the bearing cap. Tighten 5.1. Tighten the bearing cap bolts on the first pass to 20 N.m (15 lb ft). 5.2. Tighten the bearing cap bolts on the final pass to 73 degrees using the J 36660-A. 6. Remove the number 5 cap and measure the plastigauge using the inch scale. All 1996-99 5.0L (L30) and 5.7L (L31) engines were built with 0.001 in. undersized number 5 crankshaft bearing inserts. 7. If the measurement is: ^ Less than 0.0020 in. - Go To Step 8 ^ 0.0020 in. or greater but less than 0.0025 in. - Go To Step 9 ^ 0.0025 in. or greater but less than 0.0030 in. - Go To Step 10 ^ .0.0030 in. or greater - Go To Step 11 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Block Assembly > Crankshaft Main Bearing > Component Information > Technical Service Bulletins > Engine - Bearing Knock Noise > Page 2515 8. Less than 0.0020 in. 8.1. Retain production 0.001 in. undersize upper and lower bearing inserts at the number 5 crankshaft bearing position. 8.2. Clean any and all plastigauge material and residue from the bearing inserts. 8.3. Liberally coat bearing inserts with clean engine oil and reinstall crankshaft bearing caps and bolts. 8.4. Reinstall crankshaft bearing cap, bolts and studs to the engine block, making sure that the cap, bolts, and studs retain their original position and orientation. Tighten 8.4.1. Tighten the crankshaft bearing cap bolts and studs on the first pass to 20 N.m (15 lb ft). 8.4.2. Tighten the crankshaft bearing cap bolts on the final pass to 73 degrees using the J 36660-A. 8.5. Remove Screwjack used for crankshaft support. 8.6. Go to Step 12 Crankshaft (main) Bearing Service for Locations Number 2, 3, and 4. 9. 0.0020 in. or greater but less than 0.0025 in. 9.1. Retain upper bearing shell (numbers main bearing - production 0.001 in. undersized). 9.2. Remove number 5 lower main bearing shell from the cap and discard. 9.3. Install 0.002 in. undersize bearing insert (P/N 12329792) in the number 5 cap, LOWER HALF ONLY. 9.4. Apply a liberal coating of clean engine oil to the bearing surface. 9.5. Reinstall crankshaft bearing cap, bolts and studs to the engine block, making sure that the caps, bolts, and studs retain their original position and orientation. Tighten 9.5.1. Tighten the crankshaft bearing cap bolts and studs on the first pass to 20 Nm (15 lb ft). 9.5.2. Tighten the crankshaft bearing cap bolts on the final pass to 73 degrees using the J 36660-A. 9.6. Remove the screw jack used for crankshaft support. 9.7. Go to Step 12 Crankshaft (main) Bearing Service for Locations Number 2, 3, and 4. 10. 0.0025 in. or greater but less than 0.0030 in. 10.1. Lower jack stand from crankshaft, allowing the crankshaft to be supported by the numbers 1, 2, 3, and 4 crankshaft main bearings. 10.2. Insert J 8080 into the crankshaft number 5 main bearing oil hole and rotate the crankshaft to turn the upper bearing insert out of the engine block. Discard the removed upper bearing insert. 10.3. Insert J 8080 into the crankshaft number 5 main bearing oil hole. 10.4. Procure the crankshaft number 5 main bearing 0.0020 in. undersize bearing upper insert (from kit P/N 12329792), apply clean engine oil to the bearing insert, and insert the plain end (without the bearing tang) of the bearing shell between the crankshaft and the notched side of the engine block web. 10.5. Rotate the crankshaft to roll the upper bearing insert into the engine block. 10.6. Remove the J8080 from the crankshaft. 10.7. Remove the number 5 lower main bearing shell from the cap and discard. 10.8. Install 0.002 in. undersize bearing lower insert (from kit P/N 12329792) in the number 5 cap. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Block Assembly > Crankshaft Main Bearing > Component Information > Technical Service Bulletins > Engine - Bearing Knock Noise > Page 2516 10.9. Apply a liberal coating of clean engine oil to the bearing surface. 10.10. Reinstall crankshaft bearing cap, bolts and studs to the engine block, making sure that the caps, bolts, and studs retain their original position and orientation. Tighten Tighten the crankshaft bearing cap bolts and studs on the first pass to 20 N.m (15 lb ft). 10.11. Thrust the crankshaft rearward in order to set and align the crankshaft thrust bearings and the crankshaft bearing caps. 10.12. Thrust the crankshaft forward in order to align the rear faces of the crankshaft thrust bearings. Tighten Tighten the crankshaft bearing cap bolts on the final pass to 73 degrees using the J 36660-A. 10.13. Go to Step 12 Crankshaft (main) Bearing Service for Locations Number 2, 3, and 4. 11. 0.0030 in. or greater 11.1. Retain upper bearing shell (number 5 main bearing - production 0.001 in. undersized). 11.2. Remove number 5 lower main bearing shell from the cap and discard. 11.3. Install 0.004 in. undersize bearing insert (P/N 12561191) in the number 5 cap, LOWER HALF ONLY. 11.4. Apply a liberal coating of clean engine oil to the bearing surface, reinstall crankshaft bearing cap, bolts and studs to the engine block, making sure that the caps, bolts, and studs retain their original position and orientation. Tighten 11.4.1. Tighten the crankshaft bearing cap bolts and studs on the first pass to 20 N.m (15 lb ft). 11.4.2. Tighten the crankshaft bearing cap bolts on the final pass to 73 degrees using the J 36660-A. 11.5. Remove the screw jack used for crankshaft support. 11.6. Go to Step 12 Crankshaft (main) Bearing Service for Locations Number 2, 3, and 4. 12. Crankshaft (main) Bearing Service for Locations Number 2, 3, and 4 Important: Do not remove the number 1 (front) main bearing cap. 12.1. Mark and remove the bearing caps from crankshaft bearings number 2, 3, and 4. 12.2. Install new bearing inserts PIN 10120990 (standard size - lower inserts only) to the numbers 2, 3, and 4 crankshaft bearing caps. Important: Bearing caps must be installed in the proper location and orientation or engine damage could result. 12.3. Apply a liberal coating of clean engine oil to the bearing surface, and reinstall the bearing cap and bolts. Tighten 12.3.1. Tighten the bearing cap bolts on the first pass to 20 N.m (15 lb ft). 12.3.2. Final Pass (two bolt main bearing caps) - Tighten the bearing cap bolts on the final pass to 73 degrees using the J 36660-A. 12.3.3. Final Pass (four bolt main bearing caps) - Tighten the crankshaft bearing cap OUTBOARD bolts and studs to 43 degrees using the J 36660-A. 12.3.4. Final Pass (four bolt main bearing caps) - Tighten the crankshaft bearing cap INNER bolts and studs to 73 degrees using the J 36660-A. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Block Assembly > Crankshaft Main Bearing > Component Information > Technical Service Bulletins > Engine - Bearing Knock Noise > Page 2517 12.4. Go to Step 13 Connecting Rod Bearing Service. 13. Connecting Rod Bearing Service Important: Do not disassemble connecting rod bearing caps for bearing clearance measurement. The design of the connecting rods in these engines does not permit accurate bearing clearance measurements when the connecting rod caps are disassembled from the connecting rods. Conventional methods of measuring bearing clearance, such as Plastigauge, cannot accurately be performed on these engines. GM Powertrain has developed a new, accurate and time-efficient means for measuring connecting rod bearing clearance without disassembly of the connecting rods. In early 1999, SPX/Kent-Moore Tool will be releasing a new essential tool to dealers in the United States to facilitate this new procedure. Until this new, essential tool is released Contact: SPX/Kent-Moore Tool at 1(810) 345-2233 who will then arrange for dealers to borrow a special connecting rod bearing clearance measuring tool and associated instruction sheet and video. Using this methodology, measure and refit connecting rod bearing inserts in each of the connecting rods. Use undersize connecting rod bearing inserts (listed in the table below) to selectively fit each connecting rod bearing for a clearance of 0.001-0.002 in. 13.1. Center the connecting rod journal to be worked on in the 6 o'clock position. Using screw jacks, lock the crankshaft in position as close to the bearing being worked on as possible. Tighten the screw jack sufficiently to displace the oil film from the upper main bearings. To avoid damage to the crankshaft, use a cushioning material, such as a block of wood, between the crankshaft and jack. 13.2. Check rod bearing clearance using a bearing loading and unloading tool and test indicator capable of measuring 0.0001 inch increments. Important: A test indicator is required for this procedure, do not substitute a dial indicator. A dial indicator uses a plunger and will not provide repeatable results. Likewise, Plastigauge is not effective in this repair and should not be used for this procedure. To ensure this analysis technique will be accurate, do not disassemble the rod assembly. 13.3. With the rod bearing to be worked on in the 6 o'clock position, install the test indicator. Tighten the thumb screw until snug. Install the base bracket to the oil pan rail and center it so that the handle can move freely in the slot provided. The link pin on the connecting rod bearing clearance measuring tool should line up with the centerline of the connecting rod, and have a push/pull action in line with the connecting rod. This alignment is crucial for accurate and repeatable measurements. 13.4. Screw the attaching stud of the flexible dial indicator support into a convenient oil pan rail bolt hole. Position the dial indicator so that the stylus is centered on the connecting rod cap and lock the flexible dial indicator support into position. 13.5. Using the fine adjustment feature on the flexible dial indicator support (knob near dial indicator), adjust so that the dial indicator needle has sufficient travel in both directions to take an accurate measurement. 13.6. Load the connecting rod in the upward direction of piston travel and zero the test indicator. Load the connecting rod in the reverse direction, and record the reading off the indicator. Repeat this process 2-3 times, applying consistent pressure in each direction to ensure the oil film is pushed out of the journal. Record these readings. 13.7. In order to accurately determine which rod or rods is causing the knock, perform this procedure on all eight rod assemblies. 13.8. Analyze the measurements from all eight rods. Select bearings that will put the total clearance for each rod at 0.001-.002 inch clearance. Install new upper and lower bearing inserts as required, being sure to lubricate liberally with clean engine oil. Tighten 13.8.1. Tighten the rod bearing caps on the first pass to 27 N.m (20 lb ft). 13.8.2. Tighten the rod bearing caps on the final pass to 55 degrees. 13.9. Reinstall the oil pump to the crankshaft rear bearing cap. Tighten Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Block Assembly > Crankshaft Main Bearing > Component Information > Technical Service Bulletins > Engine - Bearing Knock Noise > Page 2518 13.9.1. Tighten the oil pump bolt on the first pass to 20 N.m (15 lb ft). 13.9.2. Tighten the oil pump bolt on the final pass to 65 degrees using the J 36660-A. 14. Reassemble as required. Use Service Manual procedure - Re-install Oil Pan. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Block Assembly > Crankshaft Main Bearing > Component Information > Specifications > Bearing Undersize Availability Crankshaft Main Bearing: Specifications Bearing Undersize Availability Shell type bearings are used, and if worn excessively, should be replaced. No attempt should be made to shim, file or otherwise take up worn bearings. Main bearings are available in standard and undersizes of .001, .002, .009, .010 and .020 inch. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Block Assembly > Crankshaft, Engine > Component Information > Specifications > Main Bearing Torque Specifications Crankshaft: Specifications Main Bearing Cap Main Bearing Cap Torque Specification Outer Bolts on Cap 2, 3,& 4 70 ft.lb All Others 80 ft.lb Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Block Assembly > Crankshaft, Engine > Component Information > Specifications > Main Bearing Torque Specifications > Page 2525 Crankshaft: Specifications Crankshaft Dimensions Engine Liter/CID .................................................................................................................................. ........................................................... 5.7L/V8-350 All specifications given in inches. Crankshaft Journals Main Bearing Journal Diameter ........................................................................................................... ................................................................... [06] Connecting Rod Journal Diameter .......................................................................................................................................................... 2.0978-2.0998 Maximum Out Of Round All ......................................................................................... ...................................................................................... 0.0003 Runout Service Limit ........................ .............................................................................................................................................................. ............. 10 Bearing Clearance Main Bearings ...................................................................................................................................... ...................................................................... [17] Connecting Rod Bearings ...................................... ................................................................................................................................... 0.0013-0.0035 Connecting Rods Pin Clearance ...................................................................................................................................... ...................................................... 0.0004-0.0008 Side Clearance ..................................................... ...................................................................................................................................... 0.0060-0.0140 [06] Front No. 1 journal, 2.4484-2.4493 inches; Nos. 2, 3, & 4 journals, 2.4481-2.4490 inches; No. 5 journal, 2.4479-2.4488 inches. [17] Production: Front No. 1, 0.0007-0.0021 inch; Nos. 2, 3 & 4, 0.0009-.0024 inch; rear No. 5, 0.0010-0.0027 inch. Service: Front, 0.0010-0.0025 inch; rear, 0.0015-0.0030 inch. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Block Assembly > Harmonic Balancer Crankshaft Pulley > Component Information > Technical Service Bulletins > Crankshaft Balancer - Removal/Installation Tool Harmonic Balancer - Crankshaft Pulley: Technical Service Bulletins Crankshaft Balancer Removal/Installation Tool File In Section: 6 - Engine Bulletin No.: 57-61-38 Date: January, 1996 SERVICE MANUAL UPDATE Subject: Section 6A - Engine Mechanical - Crankshaft Balancer Remover/Installer Tool Incorrectly Referenced Models: 1990-96 Chevrolet and GMC Truck S/T; M/L, C/K, P, G Models 1991-94 Oldsmobile Bravada 1996 Oldsmobile Bravada The crankshaft balancer remover/installer tool J 39046 listed in some 1990-96 service information sections 6A2, 6A3, 6A4, 6A5, 6A6, 6A7, 6A2B, 6A3B, 6A4B, 6A5B, and 6A6B is incorrectly referenced. The correct tool number for the truck models listed above is J 23523-F or equivalent. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Block Assembly > Harmonic Balancer Crankshaft Pulley > Component Information > Technical Service Bulletins > Page 2530 Harmonic Balancer - Crankshaft Pulley: Service and Repair REMOVAL ^ Tools Required J23523-F Crankshaft Balancer Puller and Installer, or equivalent 1. Remove the engine cooling fan. Refer to cooling system. 2. Remove the accessory drive pulley. 3. Remove the crankshaft balancer bolt. 4. Remove the crankshaft balancer. Use the J 23523-E. INSTALLATION ^ Tools Required . J 35468 Oil Seal Installer - . J 23523-F Crankshaft Balance Puller and Installer - Or equivalents CAUTION: The inertial weight section of the crankshaft balancer is assembled to the hub with a rubber type material. The correct Installation procedures (with the proper tool) must be followed or movement of the inertial weight section of the hub will destroy the tuning of the crankshaft balancer. 1. Install the crankshaft balancer using the, following procedure: a. Install the stud to the crankshaft. b. Thread the stud fully into the tapped hole in the crankshaft. c. Install the crankshaft balancer (external) over the end of the stud. Align the keyway in the crankshaft balancer (external) shaft with the crankshaft key. Use a small amount of RTV sealant in order to seal the crankshaft balancer (external) key to the crankshaft joint. d. Install the bearing, washer and nut on the J23523-F e. Turn the nut to pull the crankshaft balancer onto the crankshaft. f. Remove the J23523-F. 2. Install the crankshaft balancer (external) bolt and washer. ^ Tighten the bolt to 100 Nm (74 ft. lbs.). 3. Install the accessory drive pulley. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Block Assembly > Harmonic Balancer Crankshaft Pulley > Component Information > Technical Service Bulletins > Page 2531 4. Install the engine cooling fan. Refer to Cooling System. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Block Assembly > Piston, Engine > Component Information > Specifications Piston: Specifications Engine Liter/CID .................................................................................................................................. ........................................................... 5.7L/V8-350 All specifications given in inches. Piston Clearance [20] .......................................................................................................................... .......................................................... 0.0007-0.0021 Piston Pin Diameter (Std.) ................................ ............................................................................................................................................ 0.9270-0.9271 Pin To Piston Bore Clearance ..................................................................................... ................................................................................. 0.0004-0.0008 Piston Rings End Gap [02] Comp. .................................................................................................................................................. ................................................. 0.0100-0.0200 Oil .............................................................................. ........................................................................................................................... 0.0100-0.0300 Side Clearance Comp. .................................................................................................................................................. ................................................. 0.0012-0.0032 Oil .............................................................................. ........................................................................................................................... 0.0020-0.0070 [02] Minimum. [20] Production standard, piston No. 1-6: 4.051-4.0578 inches; piston No. 7 & 8: 4.0576-4.0583 inches. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Block Assembly > Piston, Engine > Component Information > Service and Repair > Oversize Availability Piston: Service and Repair Oversize Availability A 0.001 inch oversize piston is available for service use so that proper clearances can be obtained for slightly worn cylinder bores requiring only light honing. In addition, oversizes of 0.020 inch, 0.030 inch and 0.040 inch are available. If the cylinders have less than 0.005 inch taper or wear, they can be reconditioned with a hone and fitted with the 0.001 inch oversize piston. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Block Assembly > Piston, Engine > Component Information > Service and Repair > Oversize Availability > Page 2537 Piston: Service and Repair Pistons & Rods Assemble Fig. 9 Piston & Ring End Gap Orientation Assemble pistons to connecting rods, locating piston ring end gaps as shown in Fig. 9. Lubricate piston rings with clean engine oil. Without disturbing the piston ring end gap location, install piston. Piston must be installed with notch in piston facing front of engine. A 0.001 inch oversize piston is available for service use to obtain proper clearances for slightly worn cylinder bores that require only light honing. In addition, oversizes of 0.020 inch, 0.030 inch and 0.040 inch are available. If the cylinders have less than 0.005 inch taper or wear, they can be reconditioned with a hone and fitted with the 0.001 inch oversize piston. Connecting rod bearing inserts are available in standard size and undersizes of 0.001 inch, 0.002 inch, 0.010 inch and 0.020 inch. The bearings can be replaced without removing the rod assembly by removing the cap and replacing the upper and lower halves of the bearing. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Head Assembly > Valve Clearance > System Information > Specifications > Valve Clearance Specifications Valve Clearance: Specifications Valve Clearance Specifications One turn down from zero lash. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Head Assembly > Valve Clearance > System Information > Specifications > Valve Clearance Specifications > Page 2543 Valve Clearance: Specifications Valve Arrangement FRONT TO REAR 5.7L/V8-350 ......................................................................................................................................... ........................................................... E-I-I-E-E-I-I-E Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Head Assembly > Valve Clearance > System Information > Specifications > Page 2544 Valve Clearance: Adjustments 1. Remove rocker arm cover. 2. Crank engine until the mark on the vibration damper aligns with the "0 mark on the timing tab and the engine is in the number one firing position. This may be determined by placing fingers on valves of number one cylinder as the mark on the damper comes near the " 0 mark on the timing tab. If the rocker arms are not moving, the engine is in the number one firing position. If the rocker arms move as the marks comes up to the timing tab, the engine is in the number six firing position and should be turned over one more time to reach the number one firing position. 3. With the engine in this position, exhaust valves 1, 3, 4 and 8 and intake valves 1, 2, 5 and 7 can be adjusted. Even numbered cylinders are in the right bank, odd numbered cylinders are in the left bank when viewed from the rear of the engine. 4. Back off the adjusting nut until lash is felt at the pushrod, then turn in the adjusting nut until all lash is removed. This can be determined by rotating the pushrod while turning the adjusting nut. When play has been removed, turn the adjusting nut in one full additional turn. 5. Crank engine one complete revolution until the timing tab " 0 mark and vibration damper mark are aligned. This is the number six firing position. 6. With the engine in this position, exhaust valves 2, 5, 6 and 7 and intake valves 3, 4, 6 and 8 can be adjusted. 7. With valves properly adjusted, install rocker arm cover. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Head Assembly > Fuel Pressure Release > System Information > Service and Repair Fuel Pressure Release: Service and Repair TOOLS REQUIRED - J 34730 Fuel Pressure Gauge WARNING: Relieve the fuel system pressure before servicing fuel system components In order to reduce the risk of fire and personal Injury. After relieving the system pressure, a small amount of fuel may be released when servicing the fuel lines or connections. In order to reduce the chance of personal Injury, cover the regulator and the fuel line fittings with a shop towel before disconnecting. This will catch any fuel that may leak out. Place the towel In an approved container when the disconnection Is complete. 1. Disconnect the negative battery cable in order to avoid possible fuel discharge if an accidental attempt is made to start the engine. 2. Loosen the fuel filler cap in order to relieve the tank vapor pressure. 3. Connect the gauge J 34730-1A or the equivalent to the fuel pressure connection. 4. Wrap a shop towel around the fitting while connecting the gauge in order to avoid spillage. 5. Install the bleed hose into an approved container and open valve in order to bleed the system pressure. The fuel connections are now safe for servicing. 6. Drain any fuel remaining in gauge into an approved container. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Head Assembly > Rocker Arm Assembly > Component Information > Service and Repair Rocker Arm Assembly: Service and Repair Rocker arm stud removal Rocker arm stud installation Remove the old stud by placing a suitable spacer over the stud, Fig. 13. Install a nut and flat washer on the stud and pull out the stud by turning the nut. After reaming the hole for an oversize stud, coat the press-fit area of the new stud with rear axle lubricant. Install the stud using stud driver tool No. 6880, or equivalent, by driving it in until tool bottoms on the head, Fig.14. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Head Assembly > Valve Cover > Component Information > Service and Repair > Installation Valve Cover: Service and Repair Installation 1. Install a new valve rocker arm cover gasket. 2. Install the valve rocker arm cover. 3. Install the valve rocker arm cover bolts. ^ Tighten the cover bolts to 12 Nm (106 inch lbs.). 4. Install the components as follows for the left valve rocker arm cover: a. The air conditioning compressor and the bracket. Refer to Heating and Air Conditioning. b. The EGR valve inlet pipe. c. The PCV and the hose. d. The power brake vacuum pipe. 5. Install the components as follows for the right valve rocker arm cover: a. The crankcase ventilation hose. b. The oil level indicator tube bracket. c. The air cleaner intake duct. Refer to Powertrain Management. 6. Install the wiring harnesses to the valve rocker arm cover clips. 7. Install the spark plug wires. 8. Connect the battery negative cable assembly to the battery negative terminal. ^ Tighten the bolt to 15 Nm (11 ft. lbs.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Head Assembly > Valve Cover > Component Information > Service and Repair > Installation > Page 2555 Valve Cover: Service and Repair Removal 1. Disconnect the battery negative cable assembly from the battery negative terminal. 2. Remove the spark plug wires. 3. Disconnect the wiring harness from the clips, and move aside. 4. Remove the following components for access to the right valve rocker arm cover: ^ The crankcase vent hose. ^ The oil level indicator tube bracket. ^ The air cleaner intake duct. Refer to Powertrain Management. 5. Remove the following components for access to the left valve rocker arm cover: a. The air conditioning compressor and lay aside. Refer to Heating and Air Conditioning. b. The EGR valve inlet pipe. c. The PCV and the hose. d. The power brake vacuum pipe and move aside. 6. Remove the valve rocker arm cover bolts. 7. Remove the valve rocker arm cover and the gasket. 8. Clean all traces of old gasket from the valve rocker arm cover and the cylinder head. 9. Inspect the valve rocker arm cover sealing surface for distortion. Replace the valve rocker arm cover if necessary. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Head Assembly > Valve Guide > Component Information > Technical Service Bulletins > Customer Interest for Valve Guide: > 1539013 > Jul > 04 > Engine SES Lamp ON/Misfire DTC' Set Towing Uphill Valve Guide: Customer Interest Engine - SES Lamp ON/Misfire DTC' Set Towing Uphill Subject: SES Light and P0300 When Towing, Cruising Uphill or on hard Acceleration - kw 4.3, 5.0, 5.7 accelerate cruise cylinderhead DTC L30, L31, L35, LF6, LU3, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 P0308 # PIP3081 - (07/23/2004) Models: The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI. Condition/Concern: The vehicle may exhibit a SES Light due to a P0300 and misfire. If the misfire is related to the information below, it will typically happen while cruising uphill, pulling a trailer or on hard acceleration and then stop misfiring shortly after returning to an idle. Typically, cylinders 3, 4, 5 or 6 will be the ones to experience this. Recommendation/Instructions: If the P0300 SI diagnostics did not isolate a concern, the following may help: Remove the valve cover, valve springs and valve seals on the effected cylinder or cylinders. A small wire tie or rubber bands can be placed in the valve stem keeper groove to prevent the valve from falling into the cylinder. Rotate the valve while moving it up and down in the guide to see if it binds. If a binding valve is found, remove both cylinder heads and use either of the following methods to increase the stem to guide clearance: ^ Send the head out to a machine shop and advise them to increase the valve stem to guide clearance to 0.002 inch per guide. ^ Hone the guide with a 9 mm hone, such as Snap On BCG249, until a clearance of 0.002 inch is obtained. This will usually take about 4 strokes of the hone. Reassemble the cylinder heads using new valve seals. Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. Models Affected Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Head Assembly > Valve Guide > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Valve Guide: > 1539013 > Jul > 04 > Engine - SES Lamp ON/Misfire DTC' Set Towing Uphill Valve Guide: All Technical Service Bulletins Engine - SES Lamp ON/Misfire DTC' Set Towing Uphill Subject: SES Light and P0300 When Towing, Cruising Uphill or on hard Acceleration - kw 4.3, 5.0, 5.7 accelerate cruise cylinderhead DTC L30, L31, L35, LF6, LU3, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 P0308 # PIP3081 - (07/23/2004) Models: The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI. Condition/Concern: The vehicle may exhibit a SES Light due to a P0300 and misfire. If the misfire is related to the information below, it will typically happen while cruising uphill, pulling a trailer or on hard acceleration and then stop misfiring shortly after returning to an idle. Typically, cylinders 3, 4, 5 or 6 will be the ones to experience this. Recommendation/Instructions: If the P0300 SI diagnostics did not isolate a concern, the following may help: Remove the valve cover, valve springs and valve seals on the effected cylinder or cylinders. A small wire tie or rubber bands can be placed in the valve stem keeper groove to prevent the valve from falling into the cylinder. Rotate the valve while moving it up and down in the guide to see if it binds. If a binding valve is found, remove both cylinder heads and use either of the following methods to increase the stem to guide clearance: ^ Send the head out to a machine shop and advise them to increase the valve stem to guide clearance to 0.002 inch per guide. ^ Hone the guide with a 9 mm hone, such as Snap On BCG249, until a clearance of 0.002 inch is obtained. This will usually take about 4 strokes of the hone. Reassemble the cylinder heads using new valve seals. Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. Models Affected Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Head Assembly > Valve Guide > Component Information > Technical Service Bulletins > Page 2569 Valve Guide: Specifications Valve guides in these engines are an integral part of the head and, therefore, cannot be removed. For service, guide holes can be reamed oversize to accommodate one of several service valves with oversize stems. Check the valve stem clearance of each valve (after cleaning) in its respective valve guide. If the clearance exceeds the service limits of .004 inch on the intake or .005 inch on the exhaust, ream the valve guide to accommodate the next oversize diameter valve stem. Select the reamer for the smallest oversize which will provide a clean straight bore through the valve guide. After reaming, a new seat should be cut into the head to assure perfect seating of the new valve. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Head Assembly > Valve Guide > Component Information > Technical Service Bulletins > Page 2570 Valve Guide: Service and Repair Valve guides in these engines are an integral part of the head and, therefore, cannot be removed. For service, guide holes can be reamed oversize to accommodate one of several service valves with oversize stems. Check the valve stem clearance of each valve (after cleaning) in its respective valve guide. If the clearance exceeds the service limits of .004 inch on the intake or .005 inch on the exhaust, ream the valve guide to accommodate the next oversize diameter valve stem. Select the reamer for the smallest oversize which will provide a clean straight bore through the valve guide. After reaming, a new seat should be cut into the head to assure perfect seating of the new valve. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Head Assembly > Valve Spring > Component Information > Specifications Valve Spring: Specifications Engine Liter/CID .................................................................................................................................. ........................................................... 5.7L/V8-350 All specifications given in inches. Free Length ......................................................................................................................................... ........................................................................... 2.02 Installed Height ................................................ ................................................................................................................................................. 1.690-1.710 Pressure, Lbs. @ Inches Closed Intake ................................................................................................................................................... ........................................... 71.0-79.0 @ 1.830 Exhaust ................................................................................................................................................ ........................................... 76.0-84.0 @ 1.700 Open Intake ................................................................................................................................................... ............................................... 187-203 @ 1.27 Exhaust ................................................................................................................................................ ............................................... 187-203 @ 1.27 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Head Assembly > Valve, Intake/Exhaust > Component Information > Technical Service Bulletins > Customer Interest for Valve: > 1539013 > Jul > 04 > Engine - SES Lamp ON/Misfire DTC' Set Towing Uphill Valve: Customer Interest Engine - SES Lamp ON/Misfire DTC' Set Towing Uphill Subject: SES Light and P0300 When Towing, Cruising Uphill or on hard Acceleration - kw 4.3, 5.0, 5.7 accelerate cruise cylinderhead DTC L30, L31, L35, LF6, LU3, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 P0308 # PIP3081 - (07/23/2004) Models: The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI. Condition/Concern: The vehicle may exhibit a SES Light due to a P0300 and misfire. If the misfire is related to the information below, it will typically happen while cruising uphill, pulling a trailer or on hard acceleration and then stop misfiring shortly after returning to an idle. Typically, cylinders 3, 4, 5 or 6 will be the ones to experience this. Recommendation/Instructions: If the P0300 SI diagnostics did not isolate a concern, the following may help: Remove the valve cover, valve springs and valve seals on the effected cylinder or cylinders. A small wire tie or rubber bands can be placed in the valve stem keeper groove to prevent the valve from falling into the cylinder. Rotate the valve while moving it up and down in the guide to see if it binds. If a binding valve is found, remove both cylinder heads and use either of the following methods to increase the stem to guide clearance: ^ Send the head out to a machine shop and advise them to increase the valve stem to guide clearance to 0.002 inch per guide. ^ Hone the guide with a 9 mm hone, such as Snap On BCG249, until a clearance of 0.002 inch is obtained. This will usually take about 4 strokes of the hone. Reassemble the cylinder heads using new valve seals. Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. Models Affected Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Head Assembly > Valve, Intake/Exhaust > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Valve: > 1539013 > Jul > 04 > Engine - SES Lamp ON/Misfire DTC' Set Towing Uphill Valve: All Technical Service Bulletins Engine - SES Lamp ON/Misfire DTC' Set Towing Uphill Subject: SES Light and P0300 When Towing, Cruising Uphill or on hard Acceleration - kw 4.3, 5.0, 5.7 accelerate cruise cylinderhead DTC L30, L31, L35, LF6, LU3, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 P0308 # PIP3081 - (07/23/2004) Models: The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI. Condition/Concern: The vehicle may exhibit a SES Light due to a P0300 and misfire. If the misfire is related to the information below, it will typically happen while cruising uphill, pulling a trailer or on hard acceleration and then stop misfiring shortly after returning to an idle. Typically, cylinders 3, 4, 5 or 6 will be the ones to experience this. Recommendation/Instructions: If the P0300 SI diagnostics did not isolate a concern, the following may help: Remove the valve cover, valve springs and valve seals on the effected cylinder or cylinders. A small wire tie or rubber bands can be placed in the valve stem keeper groove to prevent the valve from falling into the cylinder. Rotate the valve while moving it up and down in the guide to see if it binds. If a binding valve is found, remove both cylinder heads and use either of the following methods to increase the stem to guide clearance: ^ Send the head out to a machine shop and advise them to increase the valve stem to guide clearance to 0.002 inch per guide. ^ Hone the guide with a 9 mm hone, such as Snap On BCG249, until a clearance of 0.002 inch is obtained. This will usually take about 4 strokes of the hone. Reassemble the cylinder heads using new valve seals. Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. Models Affected Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Head Assembly > Valve, Intake/Exhaust > Component Information > Specifications > Valve Specifications Valve: Specifications Valve Specifications Engine Liter/CID .................................................................................................................................. ........................................................... 5.7L/V8-350 All specifications given in inches. Stem Diameter Std. Intake ................................................................................................................................................... ...................................................... 0.3410-0.3417 Exhaust ................................................................ ...................................................................................................................................... 0.3410-0.3417 Maximum Tip Refinish ......................................................................................................................... ........................................................................ [03] Face Angle .......................................................... ....................................................................................................................................................... 45 deg. Margin [01] Intake ................................................................................................................................................... .................................................................. 0.0315 Exhaust ................................................................. .................................................................................................................................................. 0.0315 Valve Lash ........................................................................................................................................... ........................................................................... [08] [01] Minimum. [03] Grind only enough to provide true surface. After grinding valve stems, ensure sufficient clearance remains between rocker arm & valve spring cap or rotator. [08] One turn after lash is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Cylinder Head Assembly > Valve, Intake/Exhaust > Component Information > Specifications > Valve Specifications > Page 2589 Valve: Specifications Valve Arrangement FRONT TO REAR 5.7L/V8-350 ......................................................................................................................................... ........................................................... E-I-I-E-E-I-I-E Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Drive Belts, Mounts, Brackets and Accessories > Drive Belt > Component Information > Technical Service Bulletins > Customer Interest: > 77-60-02 > Jun > 98 > Engine Drive Belt Noise, P/S Pump Pulley Misaligned Drive Belt: Customer Interest Engine - Drive Belt Noise, P/S Pump Pulley Misaligned File In Section: 6 - Engine Bulletin No.: 77-60-02 Date: June, 1998 Subject: Accessory Drive Belt Noise Due to Power Steering Pump Pulley Misalignment (Properly Align Pulley) Models: 1996-98 Chevrolet and GMC C/K, M/L, S/T; G, P Models 1996-98 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, X, M, R, J, N - RPOs L35, LF6, L3O, L31, L29, L19) Condition Some owners may comment on accessory drive noise. Cause The power steering pump pulley may be misaligned with the end of the pump shaft. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Drive Belts, Mounts, Brackets and Accessories > Drive Belt > Component Information > Technical Service Bulletins > Customer Interest: > 77-60-02 > Jun > 98 > Engine Drive Belt Noise, P/S Pump Pulley Misaligned > Page 2599 In addition to the normal service for the above condition, it is critical that the pulley is flush with the end of the power steering pump shaft. If it is not, reference the appropriate service manual for proper service instructions. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time E836O Use published labor operation time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Drive Belts, Mounts, Brackets and Accessories > Drive Belt > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Drive Belt: > 08-06-01-008A > Jul > 09 > Engine - Drive Belt Misalignment Diagnostics Drive Belt: All Technical Service Bulletins Engine - Drive Belt Misalignment Diagnostics INFORMATION Bulletin No.: 08-06-01-008A Date: July 27, 2009 Subject: Diagnosing Accessory Drive Belt / Serpentine Belt Noise and Availability and Use of Kent-Moore EN-49228 Laser Alignment Tool - Drive Belt Models: 2010 and Prior GM Passenger Cars and Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 Vehicles 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add a model year and update the Tool Information. Please discard Corporate Bulletin Number 08-06-01-008 (Section 06 - Engine). Background Several aftermarket companies offer laser alignment tools for accessory drive systems that can be very helpful in eliminating drive belt noise as a result of misaligned pulleys. Typically pricing ranges from $160 - $200. EN-49228 Laser Alignment Tool - Drive Belt The GM Tool program has now made available a competitive, simple to use and time-saving laser tool to assist in achieving precise alignment of the drive belt pulleys. This optional tool removes the guesswork from proper pulley alignment and may serve to reduce comebacks from: - Drive Belt Noise - Accelerated Drive Belt Wear - Drive Belt Slippage Instructions The instructions below are specific only to the truck Gen IV V-8 family of engines. These instructions are only for illustrative purposes to show how the tool may be used. Universal instructions are included in the box with the Laser Alignment Tool - Drive Belt. Caution - Do not look directly into the beam projected from the laser. - Use caution when shining the laser on highly polished or reflective surfaces. Laser safety glasses help reduce laser beam glare in many circumstances. - Always use laser safety glasses when using the laser. Laser safety glasses are not designed to protect eyes from direct laser exposure. 1. Observe and mark the serpentine belt orientation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Drive Belts, Mounts, Brackets and Accessories > Drive Belt > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Drive Belt: > 08-06-01-008A > Jul > 09 > Engine - Drive Belt Misalignment Diagnostics > Page 2605 2. Remove the serpentine belt from the accessory drive system. 3. Install the tool onto the power steering pulley. Position the legs of the tool into the outer grooves of the pulley, farthest from the front of the engine. 4. Install the retaining cord around the pulley and to the legs of the tool. 5. Put on the laser safety glasses provided with the tool. 6. Depress the switch on the rear of the tool to activate the light beam. 7. Rotate the power steering pulley as required to project the light beam onto the crankshaft balancer pulley grooves. 8. Inspect for proper power steering pulley alignment. - If the laser beam projects onto the second rib or raised area (1), the pulleys are aligned properly. - If the laser beam projects more than one-quarter rib 0.9 mm (0.035 in) mis-alignment, adjust the position of the power steering pulley as required. - Refer to SI for Power Steering Pulley Removal and Installation procedures. 9. Install the serpentine belt to the accessory drive system in the original orientation. 10. Operate the vehicle and verify that the belt noise concern is no longer present. Tool Information Please visit the GM service tool website for pricing information or to place your order for this tool. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Drive Belts, Mounts, Brackets and Accessories > Drive Belt > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Drive Belt: > 08-06-01-008A > Jul > 09 > Engine - Drive Belt Misalignment Diagnostics > Page 2606 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Drive Belts, Mounts, Brackets and Accessories > Drive Belt > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Drive Belt: > 04-06-01-013 > Apr > 04 > Engine - Serpentine Drive Belt Wear Information Drive Belt: All Technical Service Bulletins Engine - Serpentine Drive Belt Wear Information Bulletin No.: 04-06-01-013 Date: April 29, 2004 INFORMATION Subject: Information on Serpentine Belt Wear Models: 2004 and Prior Passenger Cars and Trucks 2003-2004 and Prior HUMMER H2 All current GM vehicles designed and manufactured in North America were assembled with serpentine belts that are made with an EPDM material and should last the life of the vehicle. It is extremely rare to observe any cracks in EPDM belts and it is not expected that they will require maintenance before 10 years or 240,000 km (150,000 mi) of use. Older style belts, which were manufactured with a chloroprene compound, may exhibit cracks depending on age. However, the onset of cracking typically signals that the belt is only about halfway through its usable life. A good rule of thumb for chloroprene-based belts is that if cracks are observed 3 mm (1/8 in) apart, ALL AROUND THE BELT, the belt may be reaching the end of its serviceable life and should be considered a candidate for changing. Small cracks spaced at greater intervals should not be considered as indicative that the belt needs changing. Any belt that exhibits chunking should be replaced. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Drive Belts, Mounts, Brackets and Accessories > Drive Belt > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Drive Belt: > 77-60-02 > Jun > 98 > Engine - Drive Belt Noise, P/S Pump Pulley Misaligned Drive Belt: All Technical Service Bulletins Engine - Drive Belt Noise, P/S Pump Pulley Misaligned File In Section: 6 - Engine Bulletin No.: 77-60-02 Date: June, 1998 Subject: Accessory Drive Belt Noise Due to Power Steering Pump Pulley Misalignment (Properly Align Pulley) Models: 1996-98 Chevrolet and GMC C/K, M/L, S/T; G, P Models 1996-98 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, X, M, R, J, N - RPOs L35, LF6, L3O, L31, L29, L19) Condition Some owners may comment on accessory drive noise. Cause The power steering pump pulley may be misaligned with the end of the pump shaft. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Drive Belts, Mounts, Brackets and Accessories > Drive Belt > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Drive Belt: > 77-60-02 > Jun > 98 > Engine - Drive Belt Noise, P/S Pump Pulley Misaligned > Page 2615 In addition to the normal service for the above condition, it is critical that the pulley is flush with the end of the power steering pump shaft. If it is not, reference the appropriate service manual for proper service instructions. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time E836O Use published labor operation time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Drive Belts, Mounts, Brackets and Accessories > Drive Belt > Component Information > Technical Service Bulletins > All Other Service Bulletins for Drive Belt: > 08-06-01-008A > Jul > 09 > Engine - Drive Belt Misalignment Diagnostics Drive Belt: All Technical Service Bulletins Engine - Drive Belt Misalignment Diagnostics INFORMATION Bulletin No.: 08-06-01-008A Date: July 27, 2009 Subject: Diagnosing Accessory Drive Belt / Serpentine Belt Noise and Availability and Use of Kent-Moore EN-49228 Laser Alignment Tool - Drive Belt Models: 2010 and Prior GM Passenger Cars and Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 Vehicles 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add a model year and update the Tool Information. Please discard Corporate Bulletin Number 08-06-01-008 (Section 06 - Engine). Background Several aftermarket companies offer laser alignment tools for accessory drive systems that can be very helpful in eliminating drive belt noise as a result of misaligned pulleys. Typically pricing ranges from $160 - $200. EN-49228 Laser Alignment Tool - Drive Belt The GM Tool program has now made available a competitive, simple to use and time-saving laser tool to assist in achieving precise alignment of the drive belt pulleys. This optional tool removes the guesswork from proper pulley alignment and may serve to reduce comebacks from: - Drive Belt Noise - Accelerated Drive Belt Wear - Drive Belt Slippage Instructions The instructions below are specific only to the truck Gen IV V-8 family of engines. These instructions are only for illustrative purposes to show how the tool may be used. Universal instructions are included in the box with the Laser Alignment Tool - Drive Belt. Caution - Do not look directly into the beam projected from the laser. - Use caution when shining the laser on highly polished or reflective surfaces. Laser safety glasses help reduce laser beam glare in many circumstances. - Always use laser safety glasses when using the laser. Laser safety glasses are not designed to protect eyes from direct laser exposure. 1. Observe and mark the serpentine belt orientation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Drive Belts, Mounts, Brackets and Accessories > Drive Belt > Component Information > Technical Service Bulletins > All Other Service Bulletins for Drive Belt: > 08-06-01-008A > Jul > 09 > Engine - Drive Belt Misalignment Diagnostics > Page 2621 2. Remove the serpentine belt from the accessory drive system. 3. Install the tool onto the power steering pulley. Position the legs of the tool into the outer grooves of the pulley, farthest from the front of the engine. 4. Install the retaining cord around the pulley and to the legs of the tool. 5. Put on the laser safety glasses provided with the tool. 6. Depress the switch on the rear of the tool to activate the light beam. 7. Rotate the power steering pulley as required to project the light beam onto the crankshaft balancer pulley grooves. 8. Inspect for proper power steering pulley alignment. - If the laser beam projects onto the second rib or raised area (1), the pulleys are aligned properly. - If the laser beam projects more than one-quarter rib 0.9 mm (0.035 in) mis-alignment, adjust the position of the power steering pulley as required. - Refer to SI for Power Steering Pulley Removal and Installation procedures. 9. Install the serpentine belt to the accessory drive system in the original orientation. 10. Operate the vehicle and verify that the belt noise concern is no longer present. Tool Information Please visit the GM service tool website for pricing information or to place your order for this tool. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Drive Belts, Mounts, Brackets and Accessories > Drive Belt > Component Information > Technical Service Bulletins > All Other Service Bulletins for Drive Belt: > 08-06-01-008A > Jul > 09 > Engine - Drive Belt Misalignment Diagnostics > Page 2622 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Drive Belts, Mounts, Brackets and Accessories > Drive Belt > Component Information > Technical Service Bulletins > All Other Service Bulletins for Drive Belt: > 04-06-01-013 > Apr > 04 > Engine - Serpentine Drive Belt Wear Information Drive Belt: All Technical Service Bulletins Engine - Serpentine Drive Belt Wear Information Bulletin No.: 04-06-01-013 Date: April 29, 2004 INFORMATION Subject: Information on Serpentine Belt Wear Models: 2004 and Prior Passenger Cars and Trucks 2003-2004 and Prior HUMMER H2 All current GM vehicles designed and manufactured in North America were assembled with serpentine belts that are made with an EPDM material and should last the life of the vehicle. It is extremely rare to observe any cracks in EPDM belts and it is not expected that they will require maintenance before 10 years or 240,000 km (150,000 mi) of use. Older style belts, which were manufactured with a chloroprene compound, may exhibit cracks depending on age. However, the onset of cracking typically signals that the belt is only about halfway through its usable life. A good rule of thumb for chloroprene-based belts is that if cracks are observed 3 mm (1/8 in) apart, ALL AROUND THE BELT, the belt may be reaching the end of its serviceable life and should be considered a candidate for changing. Small cracks spaced at greater intervals should not be considered as indicative that the belt needs changing. Any belt that exhibits chunking should be replaced. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Drive Belts, Mounts, Brackets and Accessories > Drive Belt > Component Information > Technical Service Bulletins > Page 2627 Drive Belt: Service and Repair REMOVE OR DISCONNECT 1. Release belt tension. ^ Use a suitable breaker bar in the square hole provided in the belt tensioner to rotate tensioner counterclockwise and release tension on all models. CAUTION: Do not rotate the tensioner except as noted above. Also, do not allow the tensioner to snap into the "free" position. Either of these conditions could damage the belt and/or tensioner. 2. Belt. INSTALL OR CONNECT NOTE: Install a multiple ribbed belt following the belt routings shown. The grooves in the belt must match the grooves in the pulleys. The tensioner is spring loaded. After removing the belt, the tensioner will return to the tension position. 1. Route belt over all of the pulleys except the belt tensioner. 2. Release belt tensioner. ^ Use a 1/2 inch breaker bar in the square hole provided in the belt tensioner to rotate tensioner counterclockwise and release tension on all models. 3. Belt over tensioner pulley. Slowly allow tensioner to move back into installed position. 4. Check the belt for correct "V" groove tracking into each pulley. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Drive Belts, Mounts, Brackets and Accessories > Drive Belt Tensioner > Component Information > Specifications Drive Belt Tensioner: Specifications Drive Belt Tensioner Bolt ..................................................................................................................... ................................................... 50 N.m (37 lb. ft.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Drive Belts, Mounts, Brackets and Accessories > Drive Belt Tensioner > Component Information > Specifications > Page 2631 Drive Belt Tensioner: Testing and Inspection Remove or Disconnect 1. Negative battery cable. 2. Multiple ribbed drive belt. ^ Position a hex head socket on the belt tensioner pulley bolt head. ^ Move the drive belt tensioner through its full travel. NOTICE: Do not allow the drive belt tensioner to snap into the "free" position. This may result in damage to the tensioner. ^ Movement should feel smooth and return freely without any binding. If any binding is observed, replace the tensioner. Install or Connect 1. Multiple ribbed drive belt. 2. Negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Drive Belts, Mounts, Brackets and Accessories > Drive Belt Tensioner > Component Information > Specifications > Page 2632 Drive Belt Tensioner: Service and Repair Belt Tensioner Assembly Remove or Disconnect 1. Negative battery cable. 2. Multiple ribbed drive belt. 3. Bolt. 4. Tensioner. Install or Connect 1. Tensioner to mounting bracket. 2. Bolt. Tighten ^ Bolt to 50 N.m (37 lb. ft.). 3. Multiple ribbed drive belt. 4. Negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Drive Belts, Mounts, Brackets and Accessories > Engine Mount > Component Information > Service and Repair Engine Mount: Service and Repair Fig. 1 Front Engine Mount FRONT MOUNTS When raising or supporting the engine for any reason, do not use a jack under the oil pan, any sheet metal or crankshaft pulley. Due to the small clearance between the oil pan and oil pump screen, jacking against the oil pan may cause it to be bent against the pump screen, resulting in a damaged oil pickup unit. 1. Using a jack, support engine. 2. Remove engine mount through bolt and nut, Fig. 1. Raise engine only enough for sufficient clearance. Check for interference between rear of engine and the dash panel which could cause distributor damage. 3. Remove engine mount assembly bolts, nuts and washers. 4. Remove mount assembly. 5. Reverse procedure to install. REAR MOUNTS When raising or supporting the engine for any reason, do not use a jack under the oil pan, any sheet metal or crankshaft pulley. Due to the small clearance between the oil pan and oil pump screen, jacking against the oil pan may cause it to be bent against the pump screen, resulting in a damaged oil pickup unit. 1. Support rear of engine to relieve the weight on the rear mounting. 2. Remove mount to crossmember nuts and washers. 3. Remove mount to transmission attaching bolts and washers. Raise rear of engine only enough to permit removal of the mount. 4. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Engine Oil Pressure > Component Information > Specifications Engine Oil Pressure: Specifications OIL PRESSURE Minimum Hot: 1000 rpm ............................................................................................................................................. ............................................ 41.4 kPa (6.0 psi) 2000 rpm ................................................................... ................................................................................................................... 124.1 kPa (18.0 psi) 4000 rpm ...................................................................................................................................................... ............................... 165.4 kPa (24.0 psi) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Engine Oil > Component Information > Technical Service Bulletins > Engine - GM dexos 1 and dexos 2(R) Oil Specifications Engine Oil: Technical Service Bulletins Engine - GM dexos 1 and dexos 2(R) Oil Specifications INFORMATION Bulletin No.: 11-00-90-001 Date: March 14, 2011 Subject: Global Information for GM dexos1(TM) and GM dexos2(TM) Engine Oil Specifications for Spark Ignited and Diesel Engines, Available Licensed Brands, and Service Fill for Adding or Complete Oil Change Models: 2012 and Prior GM Passenger Cars and Trucks Excluding All Vehicles Equipped with Duramax(TM) Diesel Engines GM dexos 1(TM) Information Center Website Refer to the following General Motors website for dexos 1(TM) information about the different licensed brands that are currently available: http://www.gmdexos.com GM dexos 1(TM) Engine Oil Trademark and Icons The dexos(TM) specification and trademarks are exclusive to General Motors, LLC. Only those oils displaying the dexos‹›(TM) trademark and icon on the front label meet the demanding performance requirements and stringent quality standards set forth in the dexos‹›(TM) specification. Look on the front label for any of the logos shown above to identify an authorized, licensed dexos 1(TM) engine oil. GM dexos 1(TM) Engine Oil Specification Important General Motors dexos 1(TM) engine oil specification replaces the previous General Motors specifications GM6094M, GM4718M and GM-LL-A-025 for most GM gasoline engines. The oil specified for use in GM passenger cars and trucks, PRIOR to the 2011 model year remains acceptable for those previous vehicles. However, dexos 1(TM) is backward compatible and can be used in those older vehicles. In North America, starting with the 2011 model year, GM introduced dexos 1(TM) certified engine oil as a factory fill and service fill for gasoline engines. The reasons for the new engine oil specification are as follows: - To meet environmental goals such as increasing fuel efficiency and reducing engine emissions. - To promote long engine life. - To minimize the number of engine oil changes in order to help meet the goal of lessening the industry's overall dependence on crude oil. dexos 1(TM) is a GM-developed engine oil specification that has been designed to provide the following benefits: - Further improve fuel economy, to meet future corporate average fuel economy (CAFE) requirements and fuel economy retention by allowing the oil to maintain its fuel economy benefits throughout the life of the oil. - More robust formulations for added engine protection and aeration performance. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Engine Oil > Component Information > Technical Service Bulletins > Engine - GM dexos 1 and dexos 2(R) Oil Specifications > Page 2644 - Support the GM Oil Life System, thereby minimizing the replacement of engine oil, before its life has been depleted. - Reduce the duplication of requirements for a large number of internal GM engine oil specifications. International Lubricants Standardization and Approval Committee (ILSAC) GF-5 Standard In addition to GM dexos 1(TM), a new International Lubricants Standardization and Approval Committee (ILSAC) standard called GF-5, was introduced in October 2010. - There will be a corresponding API category, called: SN Resource Conserving. The current GF-4 standard was put in place in 2004 and will become obsolete in October 2011. Similar to dexos 1(TM), the GF-5 standard will use a new fuel economy test, Sequence VID, which demands a statistically significant increase in fuel economy versus the Sequence VIB test that was used for GF-4. - It is expected that all dexos 1(TM) approved oils will be capable of meeting the GF-5 standard. However, not all GF-5 engine oils will be capable of meeting the dexos 1(TM) specification. - Like dexos(TM), the new ILSAC GF-5 standard will call for more sophisticated additives. The API will begin licensing marketers during October 2010, to produce and distribute GF-5 certified products, which are expected to include SAE 0W-20, 0W-30, 5W-20, 5W-30 and 10W-30 oils. Corporate Average Fuel Economy (CAFE) Requirements Effect on Fuel Economy Since CAFE standards were first introduced in 1974, the fuel economy of cars has more than doubled, while the fuel economy of light trucks has increased by more than 50 percent. Proposed CAFE standards call for a continuation of increased fuel economy in new cars and trucks. To meet these future requirements, all aspects of vehicle operation are being looked at more critically than ever before. New technology being introduced in GM vehicles designed to increase vehicle efficiency and fuel economy include direct injection, cam phasing, turbocharging and active fuel management (AFM). The demands of these new technologies on engine oil also are taken into consideration when determining new oil specifications. AFM for example can help to achieve improved fuel economy. However alternately deactivating and activating the cylinders by not allowing the intake and exhaust valves to open contributes to additional stress on the engine oil. Another industry trend for meeting tough fuel economy mandates has been a shift toward lower viscosity oils. dexos 1(TM) will eventually be offered in several viscosity grades in accordance with engine needs: SAE 0W-20, 5W-20, 0W-30 and 5W-30. Using the right viscosity grade oil is critical for proper engine performance. Always refer to the Maintenance section of a vehicle Owner Manual for the proper viscosity grade for the engine being serviced. GM Oil Life System in Conjunction With dexos (TM) Supports Extended Oil Change Intervals To help conserve oil while maintaining engine protection, many GM vehicles are equipped with the GM Oil Life System. This system can provide oil change intervals that exceed the traditional 3,000 mile (4,830 km) recommendation. The dexos (TM) specification, with its requirements for improved oil robustness, compliments the GM Oil Life System by supporting extended oil change intervals over the lifetime of a vehicle. If all GM customers with GM Oil Life System equipped vehicles would use the system as intended, GM estimates that more than 100 million gallons of oil could be saved annually. GM dexos 2(TM) Information Center Website Refer to the following General Motors website for dexos 2(TM) information about the different licensed brands that are currently available: http://www.gmdexos.com GM dexos 2(TM) Engine Oil Trademark and Icons Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Engine Oil > Component Information > Technical Service Bulletins > Engine - GM dexos 1 and dexos 2(R) Oil Specifications > Page 2645 The dexos (TM) specification and trademarks are exclusive to General Motors, LLC. Only those oils displaying the dexos (TM) trademark and icon on the front label meet the demanding performance requirements and stringent quality standards set forth in the dexos (TM)specification. Look on the front label for any of the logos shown above to identify an authorized, licensed dexos 2(TM) engine oil. GM dexos 2(TM) Engine Oil Specification - dexos 2(TM) is approved and recommended by GM for use in Europe starting in model year 2010 vehicles, regardless of where the vehicle was manufactured. - dexos 2(TM) is the recommended service fill oil for European gasoline engines. Important The Duramax(TM) diesel engine is the exception and requires lubricants meeting specification CJ-4. - dexos 2(TM) is the recommended service fill oil for European light-duty diesel engines and replaces GM-LL-B-025 and GM-LL-A-025. - dexos 2(TM) protects diesel engines from harmful soot deposits and is designed with limits on certain chemical components to prolong catalyst life and protect expensive emission reduction systems. It is a robust oil, resisting degradation between oil changes and maintaining optimum performance longer. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Engine Oil > Component Information > Specifications > Capacity Specifications Engine Oil: Capacity Specifications Engine Oil ............................................................................................................................................ .............................................. 4.73 Liters (5.0 Quarts) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Engine Oil > Component Information > Specifications > Capacity Specifications > Page 2648 Engine Oil: Fluid Type Specifications GM Goodwrench motor oil or equivalent for API Service with STARBURST SYMBOL of the recommended viscosity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Cooler, Engine > Component Information > Technical Service Bulletins > Engine & Transmission - Oil Cooler Quick Connect Fitting Oil Cooler: Technical Service Bulletins Engine & Transmission - Oil Cooler Quick Connect Fitting File In Section: 7 - Transmission Bulletin No.: 65-71-02 Date: March, 1996 SERVICE MANUAL UPDATE Subject: Sections 7A14D and 7A17D, Automatic Transmission On-Vehicle Service - Enhanced Engine and Transmission Oil Cooler Line Quick Connect Fitting Procedures Models: 1996 Chevrolet and GMC C/K, S/T, M/L, G Models 1996 Oldsmobile Bravada with 4L60-E, 4L80-E Transmissions This bulletin has been created to enhance the support of the removal and installation of oil cooler lines from and to quick connect fittings on engines and transmissions. The content of this bulletin replaces any existing cooler line quick connect fitting procedures found in the 1996 S/T and C/K Truck and M/L and G Van Service Manuals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Cooler, Engine > Component Information > Technical Service Bulletins > Engine & Transmission - Oil Cooler Quick Connect Fitting > Page 2653 OIL COOLER LINE QUICK CONNECT FITTINGS 1 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Cooler, Engine > Component Information > Technical Service Bulletins > Engine & Transmission - Oil Cooler Quick Connect Fitting > Page 2654 OIL COOLER LINE QUICK CONNECT FITTINGS 2 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Cooler, Engine > Component Information > Technical Service Bulletins > Engine & Transmission - Oil Cooler Quick Connect Fitting > Page 2655 OIL COOLER LINE QUICK CONNECT FITTINGS 3 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Cooler, Engine > Component Information > Technical Service Bulletins > Engine & Transmission - Oil Cooler Quick Connect Fitting > Page 2656 OIL COOLER LINE QUICK CONNECT FITTINGS 4 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Filter, Engine > Component Information > Technical Service Bulletins > Engine - Noise/Damage Oil Filter Application Importance Oil Filter: Technical Service Bulletins Engine - Noise/Damage Oil Filter Application Importance INFORMATION Bulletin No.: 07-06-01-016B Date: July 27, 2009 Subject: Information on Internal Engine Noise or Damage After Oil Filter Replacement Models: 2010 and Prior Passenger Cars and Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being updated to add model years. Please discard Corporate Bulletin Number 07-06-01-016A (Section 06 - Engine/Propulsion System). Important Engine damage that is the result of an incorrect or improperly installed engine oil filter is not a warrantable claim. The best way to avoid oil filter quality concerns is to purchase ACDelco(R) oil filters directly from GMSPO. Oil filter misapplication may cause abnormal engine noise or internal damage. Always utilize the most recent parts information to ensure the correct part number filter is installed when replacing oil filters. Do not rely on physical dimensions alone. Counterfeit copies of name brand parts have been discovered in some aftermarket parts systems. Always ensure the parts you install are from a trusted source. Improper oil filter installation may result in catastrophic engine damage. Refer to the appropriate Service Information (SI) installation instructions when replacing any oil filter and pay particular attention to procedures for proper cartridge filter element alignment. If the diagnostics in SI (Engine Mechanical) lead to the oil filter as the cause of the internal engine noise or damage, dealers should submit a field product report. Refer to Corporate Bulletin Number 02-00-89-002I (Information for Dealers on How to Submit a Field Product Report). Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Filter Adapter > Component Information > Service and Repair Oil Filter Adapter: Service and Repair OIL FILTER ADAPTER REMOVAL 1. Remove the oil filter. 2. Remove the oil cooler lines. 3. Remove the bolts. 4. Remove the oil filter adapter. 5. Remove the gasket and seal. INSTALLATION 1. Install the oil filter adapter gasket. 2. Install the oil filter adapter. 3. Install the bolts. ^ Tighten the bolts to 20 Nm (18 ft. lbs.). 4. Install the oil cooler lines. 5. Install the oil filter. 6. Install the engine oil, as needed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Line, Engine > Component Information > Service and Repair > Oil Cooler Lines Oil Line: Service and Repair Oil Cooler Lines ENGINE OIL COOLER LINE REPLACEMENT The optional oil cooler is either an integral pan of the radiator or a separate unit placed in front of the radiator. Cooler lines and hoses are serviceable. OIL COOLER SYSTEM SERVICE If foreign material has entered the oil cooler or if the engine has been damaged internally, flush the oil cooler, connecting lines, and filter adapter assembly in the following manner. Engine Oil Cooler (5.0/5.7L Engines Without Heavy Duty Cooling) Engine Oil Cooler (5.7L Engine With Heavy Duty Cooling) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Line, Engine > Component Information > Service and Repair > Oil Cooler Lines > Page 2668 Auxiliary Engine Oil Cooler Assembly REMOVE OR DISCONNECT - Set the parking brake. 1. Oil cooler lines from the connector. Removing Oil Cooler Line From Connector - Using a small pick-type tool and your thumb (A in image), grasp the connector end and pull the clip from the connector (B in image). This releases the cooler line from the connector. NOTICE: Do not use more than 690 kPa (100 psi) air to clean the cooler and lines. Exceeding 690 kPa (100 psi) could damage the cooler or lines. A. Using clean solvent and compressed air, back-flush the oil cooler and lines. B. Using compressed air, remove the cleaning solvent. C. Flush the system using the same type of oil normally circulated through the cooler. 2. Bolt or nut from bracket or clamp. 3. Oil filter and discard. 4. Oil cooler lines from the clip or strap. 5. Oil cooler lines from the oil cooler at fitting. CLEAN - All components in a suitable solvent and dry with compressed air. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Line, Engine > Component Information > Service and Repair > Oil Cooler Lines > Page 2669 INSPECT - All fittings, connectors, and cooler lines for damage or distortion. INSTALL OR CONNECT NOTICE: Do not use more than 690 kPa (100 psi) air to clean the cooler and lines. Exceeding 690 kPa (100 psi) could damage the cooler or lines. Installing Oil Cooler Line Clip Into Connector - Using your thumb and forefinger, insert the connector clip into one of the three recesses in the connector (C in image). With one end of the clip engaged in the connector slot, use your thumb and rotate the clip around the connector until it snaps into place (D and E in image). NOTICE: Make sure the connector clip engages all three slots in the connector. Failure to properly install the connector clip could cause the oil cooler line to come loose and cause damage to the engine. 1. Oil cooler lines to the oil cooler. TIGHTEN - Oil cooler line fittings to 23 Nm (17 lbs. ft.). 2. Oil cooler lines to the clip or strap. TIGHTEN - Bolt to 6 Nm (53 lbs. in.). 3. Bolt or nut to bracket or clamp. TIGHTEN - Bolt to 9 Nm (80 lbs. in.). - Nut to 13 Nm (115 lbs. in.). 4. New oil filter. - Test the flow of oil through the cooler before connecting the lines. - If the flow is not restricted, connect the oil lines to the connector. - A distinct "snap" should be heard when assembling the oil cooler line to the quick connector. The oil cooler line must be fully inserted into the quick connector. Check this by applying a forceful pull to the fitting. - If the flow is restricted, replace the radiator. 5. Run the engine and check for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Line, Engine > Component Information > Service and Repair > Oil Cooler Lines > Page 2670 Oil Line: Service and Repair Oil Cooler Quick Connect Fitting This article has been updated with bulletin No.: 65-71-02 OIL COOLER QUICK CONNECT FITTING This bulletin has been created to enhance the support of the removal and installation of oil cooler lines from and to quick connect fittings on engines and transmissions. The content of this bulletin replaces any existing cooler line quick connect fitting procedures. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Line, Engine > Component Information > Service and Repair > Oil Cooler Lines > Page 2671 OIL COOLER LINE QUICK CONNECT FITTINGS 1 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Line, Engine > Component Information > Service and Repair > Oil Cooler Lines > Page 2672 OIL COOLER LINE QUICK CONNECT FITTINGS 2 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Line, Engine > Component Information > Service and Repair > Oil Cooler Lines > Page 2673 OIL COOLER LINE QUICK CONNECT FITTINGS 3 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Line, Engine > Component Information > Service and Repair > Oil Cooler Lines > Page 2674 OIL COOLER LINE QUICK CONNECT FITTINGS 4 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Pan, Engine > Component Information > Service and Repair Oil Pan: Service and Repair OIL PAN REPLACEMENT Note: A one-piece type oil pan gasket is used Remove or Disconnect 1. Negative battery cable. 2. Oil level indictor. - Raise the vehicle. Support with safety stands. - Drain the crankcase. 3. Exhaust crossover pipe. 4. Flywheel torque converter inspection cover. 5. Transmission oil cooler line retainer from the bracket, (automatic transmission only). 6. Oil filter. 7. Oil filter adapter from the lines. - Tie oil cooler lines out of the way. 8. Oil pan bolts, nuts, and strut rods, (if equipped). 9. Oil pan and gasket. - Clean gasket surfaces on the engine and oil pan. - Inspect oil pan gasket for damage. Replace if necessary. Install or Connect Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Pan, Engine > Component Information > Service and Repair > Page 2678 Apply sealant GM P/N 1052080 or equivalent to the front cover to block joint and to the rear crankshaft seal to block joint. Apply the sealant for about 25 mm (1 inch) in both directions from each of the four corners. 1. Oil pan gasket to the oil pan. 2. Oil pan to the engine. 3. Oil pan bolts, nuts, and strut rods, (If equipped). - Tighten oil pan bolts and nuts to 25 Nm (18 lb. ft.). 4. Oil filter adapter to the oil cooler lines. 5. Oil filter. 6. Transmission oil cooler line retainer to the bracket, (automatic transmission only). 7. Flywheel/torque convector inspection cover. 8. Exhaust crossover pipe. 9. Lower the vehicle. 10. Oil level indicator. 11. Negative battery cable. - Fill with the proper quantity and grade of engine oil. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Pressure Gauge > Component Information > Testing and Inspection > Gauge Readings Are Inaccurate Oil Pressure Gauge: Testing and Inspection Gauge Readings Are Inaccurate 1. Remove lead from sensor, then connect tester J 33431-A or equivalent to sensor lead and ground. 2. If gauge responds accurately to tester, replace sensor. 3. If gauge does not respond accurately to tester, replace cluster. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Pressure Gauge > Component Information > Testing and Inspection > Gauge Readings Are Inaccurate > Page 2683 Oil Pressure Gauge: Testing and Inspection Gauge Reads High 1. Disconnect lead from sensor, then turn ignition switch to the ON position and ground lead. 2. If gauge reads low, replace sensor. 3. If gauge reads high, locate and repair open circuit between sensor and gauge. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Pressure Gauge > Component Information > Testing and Inspection > Gauge Readings Are Inaccurate > Page 2684 Oil Pressure Gauge: Testing and Inspection Gauge Reads Low 1. Check oil level, add if necessary. 2. Turn ignition switch to the On position. 3. Remove oil pressure sensor lead at sensor, gauge should read high. 4. If gauge stays low, remove sensor lead at gauge. Gauge should read high. If gauge reads high, locate and repair short to ground between gauge and sensor. 5. If gauge still reads low, replace cluster. 6. With lead removed at sensor, connect an ohmmeter to sensor. With engine stopped resistance should be one ohm, and approximately 44 ohms with engine running. 7. If sensor reads significantly lower than 44 ohms with engine running, replace sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Pressure Sender > Component Information > Locations Oil Pressure Sender: Locations LH side of Engine, rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Fuel Pump Oil Pressure Switch and Sender Engine View, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Fuel Pump Oil Pressure Switch and Sender > Page 2692 Oil Pressure Switch (For Fuel Pump): Locations Oil Pressure Switch and Sender LH side of Engine, rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Page 2693 Fuel Pump Oil Pressure Switch And Sender Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Page 2694 Oil Pressure Switch (For Fuel Pump): Service and Repair Oil Pressure Switch Electrical Connector Oil Pressure Switch REMOVAL PROCEDURE 1. Remove the electrical connector. 2. Remove the fuel pump and oil pressure indicator switch, using wrench J 35748 it required. INSTALLATION PROCEDURE 1. Install the fuel pump and oil pressure indicator switch. 2. Install the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Pressure Warning Lamp/Indicator > Component Information > Description and Operation Oil Pressure Warning Lamp/Indicator: Description and Operation Many trucks use a warning light on the instrument panel in place of the conventional dash indicating gauge to warn the driver when the oil pressure is dangerously low. The warning light is wired in series with the ignition switch and the engine unit--which is an oil pressure switch. The oil pressure switch contains a diaphragm and a set of contacts. When the ignition switch is turned on, the warning light circuit is energized and the circuit is completed through the closed contacts in the pressure switch. When the engine is started, build-up of oil pressure compresses the diaphragm, opening the contacts, thereby breaking the circuit causing the light to go out. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Engine Lubrication > Oil Pump, Engine > Engine Oil Pressure > Component Information > Specifications Engine Oil Pressure: Specifications OIL PRESSURE Minimum Hot: 1000 rpm ............................................................................................................................................. ............................................ 41.4 kPa (6.0 psi) 2000 rpm ................................................................... ................................................................................................................... 124.1 kPa (18.0 psi) 4000 rpm ...................................................................................................................................................... ............................... 165.4 kPa (24.0 psi) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Intake Manifold > Component Information > Technical Service Bulletins > Engine - Intake Manifold Inspection/Replacement Intake Manifold: Technical Service Bulletins Engine - Intake Manifold Inspection/Replacement INFORMATION Bulletin No.: 00-06-01-026C Date: February 03, 2010 Subject: Intake Manifold Inspection/Replacement After Severe Internal Engine Damage Models: 2010 and Prior Passenger Cars and Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to include additional model years. Please discard Corporate Bulletin Number 00-06-01-026B (Section 06 - Engine). When replacing an engine due to internal damage, extreme care should be taken when transferring the intake manifold to the new Goodwrench service engine long block. Internal damage may result in the potential discharge of internal engine component debris in the intake manifold via broken pistons and/or bent, broken, or missing intake valves. After removing the intake manifold from the engine, the technician should carefully inspect all of the cylinder head intake ports to see if the valve heads are still present and not bent. Usually when the valve heads are missing or sufficiently bent, internal engine component debris will be present to varying degrees in the intake port of the cylinder head. If this debris is present in any of the cylinder head intake ports, the intake manifold should be replaced. This replacement is required due to the complex inlet runner and plenum configuration of most of the intake manifolds, making thorough and complete component cleaning difficult and nearly impossible to verify complete removal of debris. Re-installation of an intake manifold removed from an engine with deposits of internal engine component debris may result in the ingestion of any remaining debris into the new Goodwrench service engine. This may cause damage or potential failure of the new service engine. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Intake Manifold > Component Information > Technical Service Bulletins > Engine - Intake Manifold Inspection/Replacement > Page 2706 Intake Manifold: Technical Service Bulletins Engine - Use of Wacker RTV Sealant for Intake Manifold File In Section: 6 - Engine Bulletin No.: 67-61-17A Date: August, 1996 Subject: Use of Wacker T-330 RTV Sealant (Pronounced Vaucker T) Models: 1990-96 Buick Road master, Estate Wagon 1990-96 Cadillac Fleetwood 1990-96 Chevrolet Camaro, Caprice, Corvette, Impala SS 1990-92 Oldsmobile Custom Cruiser 1990-96 Pontiac Firebird with 4.3L, 5.7L Engine (VINs W, P, 5, 8 - RPOs L99, L98, LT1, LT4) 1990-96 Chevrolet and GMC Light and Medium Duty Trucks with 4.3L, 5.0L, 5.7L, 6.0L, 7.0L, 7.4L Engines (VINs W, Z, E H, K, M, N, P, R - RPOs L35, LB4, L03, L05, LS0, LR0, L19, L30, L31) This bulletin is being revised to add further Chevrolet models. Please discard Corporate Bulletin Number 67-61-17 (Section 6 - Engine). When installing the intake manifold, use a 5 mm (1/4 in.) thick bead of Wacker T-330 RTV, P/N 12346192, on the front and rear sealing areas between Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Intake Manifold > Component Information > Technical Service Bulletins > Engine - Intake Manifold Inspection/Replacement > Page 2707 the engine block and intake manifold. See Figures 1 and 2. Wacker T-330 RTV has improved adhesive abilities, is oxygen sensor safe, and is noncorrosive to ferrous metals. Wacker T-330 RW cannot be used in coolant sealing surface areas. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Intake Manifold > Component Information > Specifications > Lower Intake Manifold Torque and Sequence Intake Manifold: Specifications Upper Manifold Bolts First Step 44 in.lb Final Step 88 in.lb Lower Manifold bolts First Step 27 in.lb Second Step 106 in.lb Final Step 11 ft.lb Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Intake Manifold > Component Information > Service and Repair > Replacement (Upper) Intake Manifold: Service and Repair Replacement (Upper) Removal Upper Intake Removal 1. Negative battery cable. 2. Air cleaner intake duct. 3. Wiring harness connectors and brackets and move aside. 4. Throttle linkage and bracket from upper intake manifold. 5. Cruise control cable, (if equipped). 6. Fuel lines from intake to the rear of the block. 7. PCV hose at upper intake manifold. 8. Ignition coil and bracket. Refer to: See: Powertrain Management/Ignition System/Ignition Coil/Service and Repair 9. Purge solenoid and bracket. 10. Upper intake manifold bolts and studs. - Mark the location of all studs for proper reassembly. 11. Upper intake manifold. Installation Upper Intake Installation Install or Connect Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Intake Manifold > Component Information > Service and Repair > Replacement (Upper) > Page 2712 1. Upper intake manifold gasket. 2. Upper intake manifold. - Use care not to pinch the injector lines between the upper and lower intake manifolds. 3. Upper intake manifold bolts. Note the marks made at disassembly for proper stud location. Tighten Bolts in two steps. The first pass to 5 Nm (45 lb. in.). - The final pass to 10 Nm (83 lb. in.) Install the two corner studs first to help align the two halves. 4. Purge solenoid and bracket. 5. Ignition coil and bracket. 6. PCV hose at upper intake manifold. 7. Fuel lines from intake to the rear of the block. 8. Cruise control cable. 9. Throttle linkage and bracket from upper intake manifold. 10. Wiring harness connectors and brackets. 11. Air cleaner intake duct. 12. Negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Intake Manifold > Component Information > Service and Repair > Replacement (Upper) > Page 2713 Intake Manifold: Service and Repair Replacement (Lower) Removal Lower Intake Removal Remove or Disconnect 1. Distributor. Refer to: See: Tune-up and Engine Performance Checks/Distributor/Service and Repair - Mark the relationship of the distributor housing and rotor for proper reassembly. 2. Upper radiator hose at the thermostat housing. 3. Heater hose at lower intake manifold. Refer to: See: Cooling System/Heater Hose/Service and Repair 4. EGR valve. Refer to: See: Powertrain Management/Emission Control Systems/Exhaust Gas Recirculation/EGR Valve/Service and Repair 5. Coolant bypass hose. 6. EGR valve. 7. Fuel Supply and return lines at rear of lower intake manifold. 8. Wiring harness and brackets. 9. Throttle cable and bracket. 10. Cruise control cable (if equipped). 11. Left valve rocker cover. Refer to: See: Cylinder Head Assembly/Valve Cover/Service and Repair 12. Transmission oil level indicator tube, (if equipped). 13. EGR inlet tube, clamp, and bolt. 14. PCV valve and vacuum hoses. 15. Air conditioning compressor and bracket. Refer to: See: Heating and Air Conditioning/Compressor HVAC/Service and Repair - Lay the A/C compressor out of the way. Do not kink the air conditioning lines. - Loosen the A/C compressor mounting bracket and slide forward, do not remove. 16. Power brake vacuum tube. 17. Generator rear bracket bolt, (if needed). 18. Lower intake manifold bolts. 19. Lower intake manifold. Installation Lower Intake Installation Install or Connect Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Intake Manifold > Component Information > Service and Repair > Replacement (Upper) > Page 2714 1. Gaskets to the cylinder head with the port blocking plates facing the rear of the engine and "this side up" stamping facing up. 2. RTV to the front and rear sealing surfaces on the block. Apply a 5 mm (3/16 inch) bead of RTV GM P/N 1052366 or equivalent to the front and rear of the block. Extend the bear 13 mm (1/2 inch) up each cylinder head to seal and retain the gaskets. 3. Lower intake manifold to engine. - Apply sealer, GM P/N 1052080 or equivalent, to the lower intake manifold bolts. 4. Lower intake manifold bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Intake Manifold > Component Information > Service and Repair > Replacement (Upper) > Page 2715 Tighten Bolts in three steps using the sequence shown. The first sequence to 8 Nm (71 lb. in.) - The second sequence to 12 Nm (106 lb. in.) - The final sequence to 15 Nm (11 lb. ft.) 5. Wiring harness connectors and brackets. 6. Upper radiator hose at thermostat housing. 7. Heater hose at lower intake manifold. 8. Coolant by pass hose. 9. EGR valve. 10. Valve rocker arm cover. 11. Fuel supply and return lines at rear of lower intake manifold. 12. Wiring harness and brackets. 13. Cruise control cable. 14. Throttle cable and bracket. 15. Transmission oil level indicator tube. 16. EGR inlet tube, clamp and bolt. 17. PCV valve and vacuum tube. 18. Power brake vacuum tube. 19. Generator and bracket bolt, (if needed). 20. Air conditioning compressor and bracket. 21. Distributor. - Note the relationship of the distributor housing and rotor made at disassembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Lamps and Indicators - Engine > Oil Pressure Gauge > Component Information > Testing and Inspection > Gauge Readings Are Inaccurate Oil Pressure Gauge: Testing and Inspection Gauge Readings Are Inaccurate 1. Remove lead from sensor, then connect tester J 33431-A or equivalent to sensor lead and ground. 2. If gauge responds accurately to tester, replace sensor. 3. If gauge does not respond accurately to tester, replace cluster. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Lamps and Indicators - Engine > Oil Pressure Gauge > Component Information > Testing and Inspection > Gauge Readings Are Inaccurate > Page 2721 Oil Pressure Gauge: Testing and Inspection Gauge Reads High 1. Disconnect lead from sensor, then turn ignition switch to the ON position and ground lead. 2. If gauge reads low, replace sensor. 3. If gauge reads high, locate and repair open circuit between sensor and gauge. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Lamps and Indicators - Engine > Oil Pressure Gauge > Component Information > Testing and Inspection > Gauge Readings Are Inaccurate > Page 2722 Oil Pressure Gauge: Testing and Inspection Gauge Reads Low 1. Check oil level, add if necessary. 2. Turn ignition switch to the On position. 3. Remove oil pressure sensor lead at sensor, gauge should read high. 4. If gauge stays low, remove sensor lead at gauge. Gauge should read high. If gauge reads high, locate and repair short to ground between gauge and sensor. 5. If gauge still reads low, replace cluster. 6. With lead removed at sensor, connect an ohmmeter to sensor. With engine stopped resistance should be one ohm, and approximately 44 ohms with engine running. 7. If sensor reads significantly lower than 44 ohms with engine running, replace sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Lamps and Indicators - Engine > Oil Pressure Warning Lamp/Indicator > Component Information > Description and Operation Oil Pressure Warning Lamp/Indicator: Description and Operation Many trucks use a warning light on the instrument panel in place of the conventional dash indicating gauge to warn the driver when the oil pressure is dangerously low. The warning light is wired in series with the ignition switch and the engine unit--which is an oil pressure switch. The oil pressure switch contains a diaphragm and a set of contacts. When the ignition switch is turned on, the warning light circuit is energized and the circuit is completed through the closed contacts in the pressure switch. When the engine is started, build-up of oil pressure compresses the diaphragm, opening the contacts, thereby breaking the circuit causing the light to go out. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Seals and Gaskets, Engine > Crankshaft Main Bearing Seal > Component Information > Service and Repair Crankshaft Main Bearing Seal: Service and Repair Fig. 10 Seal Removal Notches Rear oil seal installation REMOVAL 1. Disconnect battery ground cable. 2. Remove transmission assembly. 3. Remove clutch, flywheel or flex plate. 4. Insert suitable screwdriver into notches provided in the seal retainer, Fig. 10, and remove rear oil seal. Carefully remove seal to avoid nicking the crankshaft sealing surface. INSTALLATION 1. Using rear crankshaft seal installer tool No. J-35621, or equivalent, install crankshaft rear oil seal as follows: a. Using clean engine oil, lubricate inner and outer diameters of seal. b. Install new seal onto tool, Fig. 11. c. Thread attaching screws into the tapped holes in the crankshaft. d. Using a screwdriver, tighten attaching screws. This will ensure the seal is installed properly over crankshaft assembly. e. Turn tool handle until it bottoms out. f. Remove tool. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Seals and Gaskets, Engine > Valve Guide Seal > Component Information > Technical Service Bulletins > Customer Interest: > 1539013 > Jul > 04 > Engine - SES Lamp ON/Misfire DTC' Set Towing Uphill Valve Guide Seal: Customer Interest Engine - SES Lamp ON/Misfire DTC' Set Towing Uphill Subject: SES Light and P0300 When Towing, Cruising Uphill or on hard Acceleration - kw 4.3, 5.0, 5.7 accelerate cruise cylinderhead DTC L30, L31, L35, LF6, LU3, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 P0308 # PIP3081 - (07/23/2004) Models: The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI. Condition/Concern: The vehicle may exhibit a SES Light due to a P0300 and misfire. If the misfire is related to the information below, it will typically happen while cruising uphill, pulling a trailer or on hard acceleration and then stop misfiring shortly after returning to an idle. Typically, cylinders 3, 4, 5 or 6 will be the ones to experience this. Recommendation/Instructions: If the P0300 SI diagnostics did not isolate a concern, the following may help: Remove the valve cover, valve springs and valve seals on the effected cylinder or cylinders. A small wire tie or rubber bands can be placed in the valve stem keeper groove to prevent the valve from falling into the cylinder. Rotate the valve while moving it up and down in the guide to see if it binds. If a binding valve is found, remove both cylinder heads and use either of the following methods to increase the stem to guide clearance: ^ Send the head out to a machine shop and advise them to increase the valve stem to guide clearance to 0.002 inch per guide. ^ Hone the guide with a 9 mm hone, such as Snap On BCG249, until a clearance of 0.002 inch is obtained. This will usually take about 4 strokes of the hone. Reassemble the cylinder heads using new valve seals. Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. Models Affected Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Seals and Gaskets, Engine > Valve Guide Seal > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Valve Guide Seal: > 1539013 > Jul > 04 > Engine - SES Lamp ON/Misfire DTC' Set Towing Uphill Valve Guide Seal: All Technical Service Bulletins Engine - SES Lamp ON/Misfire DTC' Set Towing Uphill Subject: SES Light and P0300 When Towing, Cruising Uphill or on hard Acceleration - kw 4.3, 5.0, 5.7 accelerate cruise cylinderhead DTC L30, L31, L35, LF6, LU3, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 P0308 # PIP3081 - (07/23/2004) Models: The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI. Condition/Concern: The vehicle may exhibit a SES Light due to a P0300 and misfire. If the misfire is related to the information below, it will typically happen while cruising uphill, pulling a trailer or on hard acceleration and then stop misfiring shortly after returning to an idle. Typically, cylinders 3, 4, 5 or 6 will be the ones to experience this. Recommendation/Instructions: If the P0300 SI diagnostics did not isolate a concern, the following may help: Remove the valve cover, valve springs and valve seals on the effected cylinder or cylinders. A small wire tie or rubber bands can be placed in the valve stem keeper groove to prevent the valve from falling into the cylinder. Rotate the valve while moving it up and down in the guide to see if it binds. If a binding valve is found, remove both cylinder heads and use either of the following methods to increase the stem to guide clearance: ^ Send the head out to a machine shop and advise them to increase the valve stem to guide clearance to 0.002 inch per guide. ^ Hone the guide with a 9 mm hone, such as Snap On BCG249, until a clearance of 0.002 inch is obtained. This will usually take about 4 strokes of the hone. Reassemble the cylinder heads using new valve seals. Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. Models Affected Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Seals and Gaskets, Engine > Valve Guide Seal > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Valve Guide Seal: > 676115 > May > 96 > Valve Stem Oil Seal - Correct Installation Valve Guide Seal: All Technical Service Bulletins Valve Stem Oil Seal - Correct Installation File In Section: 6 - Engine Bulletin No.: 67-61-15 Date: May, 1996 SERVICE MANUAL UPDATE Subject: Section 6A4B, 6A5B - Engine Mechanical - Valve Stem Oil Seal Installation Models: 1996 Chevrolet and GMC S/T, M/L, C/K, P, G Models 1996 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L Engine (VINs W, X, M, R - RPOs L35, LF6, L30, L31) Service Manual information for installing valve stem oil seals is incorrect in 1996 model year S/T, M/L, C/K, G, and P platform service information manuals. The procedure below details the correct installation for the engines and model years listed. Please update your service manuals with this information. The valve stem oil seals must be installed with Kent-Moore tool J 42073. 1. Install valve spring compressor J 8062 onto the valve spring and compress the valve spring. 2. Remove the valve keys. 3. Remove the valve spring and cap. 4. Remove the old valve stem oil seal. 5. Clean the valve spring seat area. It must be free of any foreign material. 6. Lubricate the valve stem oil seal and guide with clean engine oil. 7. Install the valve stem oil seal onto the valve stem. Push seal down until the seal contacts valve guide. Important: The valve must be installed into the cylinder head to properly align tool J 42073 over the valve guide. 8. Place J 42073 over the valve stem and oil seal. Tap on tool J 42073 until the tool bottoms out against the valve spring seat (Figure 1). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Seals and Gaskets, Engine > Valve Guide Seal > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Valve Guide Seal: > 676115 > May > 96 > Valve Stem Oil Seal - Correct Installation > Page 2747 Important: Valve stem oil seal alignment onto the valve guide is critical. Important: A correctly installed seal should not bottom against the valve guide. There should be a 1-2 mm (0.03937-0.07874") gap between the bottom edge of the seal and the valve guide (Figure 2). 9. Install the valve spring and cap. 10. Install valve spring compressor J 8062 onto the valve spring and compress spring. 11. Install the valve keys. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Seals and Gaskets, Engine > Valve Guide Seal > Component Information > Technical Service Bulletins > All Other Service Bulletins for Valve Guide Seal: > 676115 > May > 96 > Valve Stem Oil Seal - Correct Installation Valve Guide Seal: All Technical Service Bulletins Valve Stem Oil Seal - Correct Installation File In Section: 6 - Engine Bulletin No.: 67-61-15 Date: May, 1996 SERVICE MANUAL UPDATE Subject: Section 6A4B, 6A5B - Engine Mechanical - Valve Stem Oil Seal Installation Models: 1996 Chevrolet and GMC S/T, M/L, C/K, P, G Models 1996 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L Engine (VINs W, X, M, R - RPOs L35, LF6, L30, L31) Service Manual information for installing valve stem oil seals is incorrect in 1996 model year S/T, M/L, C/K, G, and P platform service information manuals. The procedure below details the correct installation for the engines and model years listed. Please update your service manuals with this information. The valve stem oil seals must be installed with Kent-Moore tool J 42073. 1. Install valve spring compressor J 8062 onto the valve spring and compress the valve spring. 2. Remove the valve keys. 3. Remove the valve spring and cap. 4. Remove the old valve stem oil seal. 5. Clean the valve spring seat area. It must be free of any foreign material. 6. Lubricate the valve stem oil seal and guide with clean engine oil. 7. Install the valve stem oil seal onto the valve stem. Push seal down until the seal contacts valve guide. Important: The valve must be installed into the cylinder head to properly align tool J 42073 over the valve guide. 8. Place J 42073 over the valve stem and oil seal. Tap on tool J 42073 until the tool bottoms out against the valve spring seat (Figure 1). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Seals and Gaskets, Engine > Valve Guide Seal > Component Information > Technical Service Bulletins > All Other Service Bulletins for Valve Guide Seal: > 676115 > May > 96 > Valve Stem Oil Seal - Correct Installation > Page 2753 Important: Valve stem oil seal alignment onto the valve guide is critical. Important: A correctly installed seal should not bottom against the valve guide. There should be a 1-2 mm (0.03937-0.07874") gap between the bottom edge of the seal and the valve guide (Figure 2). 9. Install the valve spring and cap. 10. Install valve spring compressor J 8062 onto the valve spring and compress spring. 11. Install the valve keys. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Sensors and Switches - Engine > Oil Pressure Sender > Component Information > Locations Oil Pressure Sender: Locations LH side of Engine, rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Sensors and Switches - Engine > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Fuel Pump Oil Pressure Switch and Sender Engine View, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Sensors and Switches - Engine > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Fuel Pump Oil Pressure Switch and Sender > Page 2762 Oil Pressure Switch (For Fuel Pump): Locations Oil Pressure Switch and Sender LH side of Engine, rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Sensors and Switches - Engine > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Page 2763 Fuel Pump Oil Pressure Switch And Sender Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Sensors and Switches - Engine > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Page 2764 Oil Pressure Switch (For Fuel Pump): Service and Repair Oil Pressure Switch Electrical Connector Oil Pressure Switch REMOVAL PROCEDURE 1. Remove the electrical connector. 2. Remove the fuel pump and oil pressure indicator switch, using wrench J 35748 it required. INSTALLATION PROCEDURE 1. Install the fuel pump and oil pressure indicator switch. 2. Install the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Timing Components > Timing Chain > Component Information > Service and Repair Timing Chain: Service and Repair Fig. 8 Timing Mark Alignment 1. Remove Front Cover. 2. Remove crankshaft oil slinger. 3. Crank engine until 0.0 marks on sprockets are in alignment, Fig. 8. 4. Remove three camshaft to sprocket bolts. 5. Remove camshaft sprocket and timing chain together. Sprocket is a light press fit on camshaft for approximately 1/8 inch. If sprocket does not come off easily, a light blow with a plastic hammer on the lower edge of the sprocket should dislodge it. 6. If crankshaft sprocket is to be replaced, remove it with a gear puller. Install new sprocket, aligning key and keyway. 7. Install chain onto camshaft sprocket. Hold sprocket with chain hanging vertically, then align marks on sprockets as shown, Fig. 8. The valve timing marks shown in Fig. 8 do not indicate TDC compression stroke for No. 1 cylinder, which is used during distributor installation. If distributor was removed, install timing chain and sprockets, aligning timing marks, Fig. 8, then rotate engine until No. 1 cylinder is on compression and camshaft timing mark is 180 degrees from valve timing position shown in Fig. 8. 8. Align dowel in camshaft with dowel hole in sprocket and install sprocket on camshaft. Do not attempt to drive sprocket on camshaft, as welch plug at rear of engine can be dislodged. 9. Draw sprocket onto camshaft, using the three mounting bolts. Tighten to specifications. 10. Lubricate timing chain and install cover. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Timing Components > Timing Cover > Component Information > Service and Repair Timing Cover: Service and Repair REMOVAL NOTE: Any time the composite front cover is removed, the cover needs to be replaced upon reassembly. If the cover that was removed is reinstalled, oil leaks may develop. 1. Remove the crankshaft balancer (external). 2. Remove the water pump. 3. Loosen the oil pan. 4. Remove the crankshaft position sensor. Refer to Powertrain Management. 5. Remove the front cover bolts. NOTE: Use care when removing the front cover from the front of the oil pan seal. 6. Remove the front cover. 7. Clean the varnish and sludge build up from the front cover area. INSTALLATION 1. Install the front cover and bolts. Use care when engaging the front of the oil pan sealing surface and Gasket with the bottom of the front cover. Install RTV to the lower corners of the front cover to aid in sealing. ^ Tighten the front cover bolts to 12 Nm (106 inch lbs.). 2. Install the crankshaft position sensor. Refer to Powertrain Management. 3. Install the oil pan. Refer to Engine. 4. Install the water pump. 5. Install the crankshaft balancer (external). Refer to Engine Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Fuel Pressure > Diagnostic Connector - Fuel Pump > Component Information > Locations Diagnostic Connector - Fuel Pump: Locations For Fuel Pump Prime and Run Connector, See Computer and Control Systems, Data Link Connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Idle Speed > System Information > Specifications > Controlled Idle Speed Idle Speed: Specifications Controlled Idle Speed Under 8500 GVW Transmission Gear Idle Speed IAC Counts [1] OPEN/CLOSED Loop [2] Manual N 675 +/- 25 Varies CL Automatic D 550 +/- 25 Varies CL [1] On manual transmission vehicles the SCAN tool will display RDL in Neutral. Add 2 counts for engines with less than 500 miles. Add 2 counts for every 1000 ft. above sea level. [2] Let engine idle until proper fuel control status is reached (OPEN/CLOSED loop). Note: Engine should be at operating temperature 92°C to 104° (196°F to 222°F). Over 8500 GVW Transmission Gear Idle Speed IAC Counts [1] OPEN/CLOSED Loop [2] Manual N 675 +/- 25 Varies CL Automatic D 550 +/- 25 Varies CL [1] On manual transmission vehicles the SCAN tool will display RDL in Neutral. Add 2 counts for engines with less than 500 miles. Add 2 counts for every 1000 ft. above sea level. [2] Let engine idle until proper fuel control status is reached (OPEN/CLOSED loop). Note: Engine should be at operating temperature 92°C to 104° (196°F to 222°F). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Idle Speed > System Information > Adjustments > Controlled Idle Speed Idle Speed: Adjustments Controlled Idle Speed NOTE: There should be no Diagnostic Trouble Code (DTC)s displayed. The idle air control system has been checked. 1. Set the parking brake. 2. Block the drive wheels. 3. Connect a scan tool to the Data Link Connector (DLC) connector with the tool in the open mode. 4. Start the engine. 5. Bring the engine to the normal operating temperature. 6. Check for the correct state of the Transmission Range (TR) switch position on the scan tool. 7. Check the specifications for controlled idle speed and Idle Air Control (IAC) valve pintle position (counts). Refer to Idle Air Control Valve / Service and Repair. See: Powertrain Management/Computers and Control Systems/Idle Air Control (IAC) Valve/Service and Repair 8. If within specifications, the idle speed is being correctly controlled by the control module. 9. If not within specifications, refer to Driveability Symptoms. Refer to System Diagnosis for testing information. See: Powertrain Management/Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Cleaner Fresh Air Duct/Hose > Component Information > Specifications Air Cleaner Fresh Air Duct/Hose: Specifications Air intake duct screw ........................................................................................................................... ........................................................ 2 Nm (18 lb. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Cleaner Fresh Air Duct/Hose > Component Information > Specifications > Page 2787 Air Cleaner Fresh Air Duct/Hose: Service and Repair Air Intake Duct Retainer Bolt Air Intake Duct Removal Procedure 1. Remove the retainer. 2. Remove the screw. 3. Remove the air intake duct Installation Procedure 1. Install the air intake duct. 2. Install the screw. Tighten Tighten the screw 2 Nm (18 lb. in.). 3. Install the retainer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Customer Interest for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T - Shift/Driveability Concerns/MIL ON Air Filter Element: Customer Interest Engine, A/T - Shift/Driveability Concerns/MIL ON Bulletin No.: 04-07-30-013B Date: February 01, 2007 INFORMATION Subject: Automatic Transmission Shift, Engine Driveability Concerns or Service Engine Soon (SES) Light On as a Result of the Use of an Excessively/Over-Oiled Aftermarket, Reusable Air Filter Models: 2007 and Prior GM Cars and Light Duty Trucks 2007 and Prior Saturn Models 2003-2007 HUMMER H2 2006-2007 HUMMER H3 2005-2007 Saab 9-7X Supercede: This bulletin is being revised to add models and model years. Please discard Corporate Bulletin Number 04-07-30-013A (Section 07 - Transmission/Transaxle). The use of an excessively/over-oiled aftermarket, reusable air filter may result in: Service Engine Soon (SES) light on Transmission shift concerns, slipping and damaged clutch(es) or band(s) Engine driveability concerns, poor acceleration from a stop, limited engine RPM range The oil that is used on these air filter elements may be transferred onto the Mass Air Flow (MAF) sensor causing contamination of the sensor. As a result, the Grams per Second (GPS) signal from the MAF may be low and any or all of the concerns listed above may occur. When servicing a vehicle with any of these concerns, be sure to check for the presence of an aftermarket reusable, excessively/over-oiled air filter. The MAF, GPS reading should be compared to a like vehicle with an OEM air box and filter under the same driving conditions to verify the concern. The use of an aftermarket reusable air filter DOES NOT void the vehicle's warranty. If an aftermarket reusable air filter is used, technicians should inspect the MAF sensor element and the air induction hose for contamination of oil prior to making warranty repairs. Transmission or engine driveability concerns (related to the MAF sensor being contaminated with oil) that are the result of the use of an aftermarket reusable, excessively/over-oiled air filter are not considered to be warrantable repair items. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Customer Interest for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T - Shift/Driveability Concerns/MIL ON > Page 2796 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T - Shift/Driveability Concerns/MIL ON Air Filter Element: All Technical Service Bulletins Engine, A/T - Shift/Driveability Concerns/MIL ON Bulletin No.: 04-07-30-013B Date: February 01, 2007 INFORMATION Subject: Automatic Transmission Shift, Engine Driveability Concerns or Service Engine Soon (SES) Light On as a Result of the Use of an Excessively/Over-Oiled Aftermarket, Reusable Air Filter Models: 2007 and Prior GM Cars and Light Duty Trucks 2007 and Prior Saturn Models 2003-2007 HUMMER H2 2006-2007 HUMMER H3 2005-2007 Saab 9-7X Supercede: This bulletin is being revised to add models and model years. Please discard Corporate Bulletin Number 04-07-30-013A (Section 07 - Transmission/Transaxle). The use of an excessively/over-oiled aftermarket, reusable air filter may result in: Service Engine Soon (SES) light on Transmission shift concerns, slipping and damaged clutch(es) or band(s) Engine driveability concerns, poor acceleration from a stop, limited engine RPM range The oil that is used on these air filter elements may be transferred onto the Mass Air Flow (MAF) sensor causing contamination of the sensor. As a result, the Grams per Second (GPS) signal from the MAF may be low and any or all of the concerns listed above may occur. When servicing a vehicle with any of these concerns, be sure to check for the presence of an aftermarket reusable, excessively/over-oiled air filter. The MAF, GPS reading should be compared to a like vehicle with an OEM air box and filter under the same driving conditions to verify the concern. The use of an aftermarket reusable air filter DOES NOT void the vehicle's warranty. If an aftermarket reusable air filter is used, technicians should inspect the MAF sensor element and the air induction hose for contamination of oil prior to making warranty repairs. Transmission or engine driveability concerns (related to the MAF sensor being contaminated with oil) that are the result of the use of an aftermarket reusable, excessively/over-oiled air filter are not considered to be warrantable repair items. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T - Shift/Driveability Concerns/MIL ON > Page 2802 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Page 2803 Air Filter Element: Testing and Inspection The air cleaner restriction indicator is located on the intake duct between the air cleaner assembly and the Mass Air Flow (MAF) sensor. If the area inside of the clear section is green, no air filter service is required. If the area inside the clear section is orange and Change Air Filter appears, replace the air filter. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Page 2804 Air Filter Element: Service and Repair Air Cleaner Element Holddown REMOVAL PROCEDURE 1. Disconnect the hold down clips. 2. Remove the air cleaner cover. 3. Remove the filter. Hold the duct and remove the filter by pulling and twisting the filter away from the duct. 4. Clean the air cleaner housing. INSTALLATION PROCEDURE 1. Install the filter. - Install the new filter by pushing it all the way to the stops of the duct. - Install the duct and filter in the air cleaner housing. Make sure that the duct fits properly into the housing. 2. Install the air cleaner cover. 3. Connect the hold down clips. 4. Push the button on the top of the indicator to reset it to the green (Clean) filter zone. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Fuel Filter > Fuel Pressure Release > System Information > Service and Repair Fuel Pressure Release: Service and Repair TOOLS REQUIRED - J 34730 Fuel Pressure Gauge WARNING: Relieve the fuel system pressure before servicing fuel system components In order to reduce the risk of fire and personal Injury. After relieving the system pressure, a small amount of fuel may be released when servicing the fuel lines or connections. In order to reduce the chance of personal Injury, cover the regulator and the fuel line fittings with a shop towel before disconnecting. This will catch any fuel that may leak out. Place the towel In an approved container when the disconnection Is complete. 1. Disconnect the negative battery cable in order to avoid possible fuel discharge if an accidental attempt is made to start the engine. 2. Loosen the fuel filler cap in order to relieve the tank vapor pressure. 3. Connect the gauge J 34730-1A or the equivalent to the fuel pressure connection. 4. Wrap a shop towel around the fitting while connecting the gauge in order to avoid spillage. 5. Install the bleed hose into an approved container and open valve in order to bleed the system pressure. The fuel connections are now safe for servicing. 6. Drain any fuel remaining in gauge into an approved container. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Firing Order > Component Information > Specifications > Ignition Firing Order Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Ignition Timing > Number One Cylinder > Component Information > Locations > Number 1 Cylinder Location Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Ignition Timing > Timing Marks and Indicators > System Information > Locations > Crankshaft Rotation Timing Marks and Indicators: Locations Crankshaft Rotation Crankshaft Rotation (Typical Crankshaft Pulley) Crankshaft rotation is clockwise when viewed from in front of the crankshaft pulley as shown in the generic image. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Ignition Timing > Timing Marks and Indicators > System Information > Locations > Crankshaft Rotation > Page 2822 Timing Marks and Indicators: Locations Timing Marks The ignition timing is completely controlled by the Vehicle Control Module (VCM). No timing reference marks are provided. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications Spark Plug Wire: Specifications 0-15 inch cable .................................................................................................................................... .................................................. 3,000 - 10,000 ohms. 15-25 inch cable .................................................................................................................................. .................................................. 4,000 - 15,000 ohms. 25-35 inch cable .................................................................................................................................. .................................................. 6,000 - 20,000 ohms. Longer wires should measure about 5,000 to 10,000 ohms per foot. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 2826 Spark Plug Wire: Locations Spark Plug Wire Routing Right Side Spark Plug Wire Routing Left Side Wire routings must be kept intact during service and followed exactly when wires have been disconnected or when replacement of the wires is necessary. Failure to route the wires properly can lead to radio ignition noise and crossfiring of the plugs or shorting of the leads to ground Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 2827 Spark Plug Wire: Service Precautions Service Precautions 1. Twist boots one-half turn before removing. 2. When removing the boot, do not use pliers or other tools that could tear the boot. 3. Do not force anything between the wire and the boot, or through the silicone jacket of the wiring. 4. Do not pull on the wires to remove the boot. Pull on the boot or use a tool designed for this purpose. 5. Special care should be used when installing spark plug boots to ensure the metal terminal within the boot is fully seated on the spark plug terminal and the boot has not moved on the wire. NOTE: If boot to wire movement has occurred, the boot will give a false visual impression of being fully seated. Make sure that boots have been properly assembled by pushing sideways on the in stalled boots. Failure to properly seat the terminal onto the spark plug will lead to wire core erosion and result in an engine misfire or crossfire condition, and possible internal damage to the engine. ^ If they have been correctly installed, a stiff boot with only slight looseness will be noted. If the terminal has not been properly seated on the spark plug, only the resistance of the boot will be felt when pushing sideways. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 2828 Spark Plug Wire: Testing and Inspection VISUAL INSPECTION 1. Inspect the routing of the wires. Improper routing can cause crossfiring. 2. Inspect each wire for any signs of cracks or splits in the wire. 3. Inspect each boot for signs of tears, piercing, arc through, or carbon tracking. If the boot needs to be replaced, twist it a half-turn in either direction to break the seal before pulling on the boot to remove the wire. SPARK PLUG WIRE RESISTANCE TEST 1. Disconnect both ends of each wire. Make sure the wire terminals are clean. 2. Set ohmmeter on the high scale and connect it to each end of the wire being tested. Twist the wire gently while watching ohmmeter. 3. If ohmmeter reads above 30,000 ohms (no matter how long the wire is), or fluctuates from infinity any value, replace the wire. 4. If the resistance of any wire is not within the following ranges, replace the wire being tested. - 0 to 381 mm (0 to 15 in.) wire - 3,000 to 10,000 ohms. - 381 mm to 635 mm (15 in. to 25 in.) wire - 4,000 to 15,000 ohms. - 635 mm to 889 mm (25 in. to 35 in.) wire - 6,000 to 20,000 ohms. - Longer wire - should measure about 5,000 to 10,000 ohms per foot. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 2829 Spark Plug Wire: Service and Repair Spark Plug Wire Routing Right Side Spark Plug Wire Routing Left Side SERVICE CAUTIONS 1. Twist boots one-half turn before removing. 2. When removing the boot, do not use pliers or other tools that could tear the boot. 3. Do not force anything between the wire and the boot, or through the silicone jacket of the wiring. 4. Do not pull on the wires to remove the boot. Pull on the boot or use a tool designed for this purpose. 5. Special care should be used when installing spark plug boots to ensure the metal terminal within the boot is fully seated on the spark plug terminal and the boot has not moved on the wire. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 2830 WARNING: If boot to wire movement has occurred, the boot will give a false visual impression of being seated. Make sure that boots have been properly assembled by pushing sideways on the installed boots. Failure to properly seat the terminal onto the spark plug will lead to wire core erosion and result in an engine misfire or crossfire condition, and possible internal damage to the engine. ^ If they have been correctly installed, a stiff boot with only slight looseness will be noted. If the terminal has not been properly seated on the spark plug, only the resistance of the boot will be felt when pushing sideways. SPARK PLUG WIRE REPLACEMENT Spark plug wire routings must be kept intact during service and followed exactly when spark plug wires have been disconnected or when replacement of the spark plug wires is necessary. Failure to route the spark plug wires properly can lead to radio noise and crossfiring of the spark plugs, or shorting of the leads to ground. The correct routing is shown in the images. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Ignition System - Distributor Is Now Repairable Distributor: Technical Service Bulletins Ignition System - Distributor Is Now Repairable CHEVROLET 71-65-40 Issued: 05/01/97 SMU - SECTION 6E - REVISED ENHANCED IGNITION SYSTEM DESCRIPTION AND OPERATION SUBJECT: SERVICE MANUAL UPDATE - SECTION 6E - ENGINE CONTROLS REVISED ENHANCED IGNITION SYSTEM DESCRIPTION AND OPERATION MODELS: 1995-97 CHEVROLET AND GMC S/T, M/L, C/K, GMT600, P MODELS 1996-97 OLDSMOBILE BRAVADA WITH 4.3L, 5.0L, 5.7L, 7.4L ENGINE (VINS W, M, R, J - RPOS L35, L30, L31, L29) THIS BULLETIN IS BEING ISSUED TO INFORM TECHNICIANS OF A REVISION TO THE ENHANCED IGNITION SYSTEM DESCRIPTION AND OPERATION. THE DISTRIBUTOR IS NOW REPAIRABLE. TECHNICIANS WILL BE REFERRED TO DISTRIBUTOR OVERHAUL IN ENGINE ELECTRICAL FOR PROPER REPAIR AND REPLACEMENT OF ALL COMPONENTS. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Ignition System - Distributor Is Now Repairable > Page 2835 Distributor: Technical Service Bulletins Ignition - Distributor Service Kits Now Available File In Section: 6 - Engine Bulletin No.: 77-64-04 Date: April, 1997 SERVICE MANUAL UPDATE Subject: Distributor Service Kits Models: 1995 Chevrolet and GMC S/T Utility Models with 4.3L OBDII Engines ONLY (VIN W - RPO L35) 1996 Chevrolet and GMC C/K, M/L, S/T; P, G 1996 Oldsmobile Bravada 1997 Chevrolet and GMC C/K, M/L, S/T; P, G 1997 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L, 7.4L Engines (VINs W, X, M, R, J - RPOs L35, LF6, L3O, L31, L29) Service kits are now available to field service Distributor Assemblies. Important: Fastening screws have pre-applied thread locking adhesive and should be discarded after removal. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Ignition System - Distributor Is Now Repairable > Page 2836 1995 4.3L L35 OBDII Distributor Assemblies are now serviced with 1996 Distributor Assemblies (P/N 1104050). Installation instructions are included with each replacement assembly and must be followed. The following Service Kits are now available: Important: Removed fasteners are not to be re-used. Always use the new fasteners supplied in each kit. Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Ignition System - Distributor Is Now Repairable > Page 2837 Warranty Information For Vehicles repaired under warranty use the table shown. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Page 2838 Distributor: Specifications Distributor clamp and bolt .................................................................................................................... .................................................. 27 N.m (20 lbs. ft.) Distributor cap screws ........................................ ....................................................................................................................... 4.5-5.0 N.m (40-45 lbs. in.) Distributor rotor .................................................................................................................................... ................................................... 2 N.m (20 lbs. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Page 2839 Distributor: Locations Top of Engine, at rear, near Bulkhead Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Page 2840 Distributor: Application and ID The part number is pin stamped into the plastic base (directly below the high tension terminals and next to the three pin camshaft sensor connection.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Description and Operation > Distributor Operation Distributor: Description and Operation Distributor Operation DISTRIBUTORS Distributor This ignition system includes the distributor, hall effect switch, ignition coil, secondary wires, spark plugs, knock sensor and crankshaft position sensor. The ignition system is controlled by the vehicle control module (VCM). The VCM monitors information from various engine sensors, computes the desired spark timing and controls the dwell and firing of the ignition coil via an ignition control line to the coil driver. The distributor connects the ignition coil and spark plugs through secondary wires. The rotor directs the spark to the appropriate cylinder. The distributor has a hall effect switch that connects to the VCM through the primary engine harness and provides cylinder identification information. Identification The part number is pin stamped into the plastic base (directly below the high tension terminals and next to the three pin camshaft sensor connection.) Ignition Coil The coil driver controls the current flow in the primary winding of the ignition coil when signaled by the VCM. The interconnects are made by the primary engine harness. The ignition coil can generate up to 35,000 volts and connects to the distributor through a secondary wire. Secondary Wires The secondary wires carry voltage between the ignition coil, distributor, and spark plugs. The secondary wire connections form a tight seal that prevents voltage arching. Hall Effect Switch The hall effect switch connects to the VCM through the primary engine harness and provides cylinder identification information. The hall effect switch is located under the distributor cap. Crankshaft Position Sensor The crankshaft position sensor connects to the VCM through the primary engine harness and provides crank- shaft reference information to the VCM for spark and fuel delivery. The crankshaft position sensor is located in the front cover behind the crankshaft balancer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Description and Operation > Distributor Operation > Page 2843 Distributor: Description and Operation General Description Distributor The distributor is actually an assembly that contains the Camshaft Position (CMP) sensor, cap, rotor and shaft. The distributor is splined by a helical gear to the camshaft and provides spark to each spark plug wire. when servicing the distributor, it is critical to ensure proper cap sealing to the distributor body and correct installation to the camshaft. If the distributor is installed a tooth off in relation to the camshaft, a Diagnostic Trouble Code (DTC) will set. The distributor is not repairable and must be replaced as an assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Description and Operation > Page 2844 Distributor: Testing and Inspection NOTICE: Discoloration of the cap and some whitish build up around the cap terminals is normal. Yellowing of the rotor cap, darkening and some carbon build-up under the rotor segment is normal. Replacement of the cap and rotor is not necessary unless there is a driveablity concern. Inspect 1. Cap for cracks, tiny holes or carbon tracks between cap terminal traces. Carbon tracks can be diagnosed by using an ohmmeter. With the cap removed, place one base ohmmeter lead on a cap terminal. Use the other lead to probe all other terminals and the center carbon ball. Move the base lead to the next terminal and probe all other leads. Continue until all secondary terminals have been tested. If there are any non-infinite readings, replace the cap. 2. Cap for excessive build up of corrosion on the terminals. Scrape them clean or replace the cap. Some build up is normal. 3. Rotor segment. Replace the rotor if there is excessive wear on the rotor segment or the plastic under the segment or staked post is melted. Some looseness of the rotor segment is normal and does not cause performance problems. 4. Shaft for shaft-to-bushing looseness. Insert the shaft in the housing. If the shaft wobbles, replace the housing assembly. 5. Housing for cracks or damage. ^ Refer to Computers and Control Systems for ignition system diagnosis. See: Powertrain Management/Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment Distributor: Adjustments Camshaft Retard Offset Adjustment Description TEST PROCEDURE The ignition timing cannot be adjusted. The distributor may need adjusting to prevent crossfire. To insure proper alignment of the distributor, perform the following: 1. With the ignition OFF, install a scan tool to the DLC. 2. Start the engine and bring to normal operating temperature. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM. 3. Increase engine speed to 1000 RPM. 4. Monitor the Cam Retard Offset. 5. If the Cam Retard indicates a value of 0° +/-2°, the distributor is properly adjusted. 6. If the Cam Retard does not indicate 0° +/-2°, the distributor must be adjusted. ADJUSTING PROCEDURE 1. With the engine OFF, slightly loosen the distributor hold down bolt. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM. 2. Start the engine and raise engine speed to 1000 RPM. 3. Using a scan tool monitor Cam Retard Offset. 4. Rotate the distributor as follows: 4.1. To compensate for a negative reading, rotate the distributor in the counterclockwise direction. 4.2. To compensate for a positive reading, rotate the distributor in the clockwise direction. 5. Repeat step 4 until 0° +/-2°, is obtained. 6. Turn the ignition OFF. 7. Tighten the distributor hold-down bolt to 3 Nm (25 lb. ft.). 8. Start the engine, raise engine speed to 1000 RPM and recheck Camshaft Retard Offset. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 2847 Distributor: Adjustments Timing Adjustment NOTICE: The distributor is located in a fixed, non-adjustable position. No attempt should be made to adjust the engine base timing by rotating the distributor. Attempting to do so may result in engine cross-fire and mis-fire conditions. The distributor ignition system has no provision for timing adjustment. The base timing is preset when the engine is manufactured and no adjustment is possible. NOTICE: If the distributor is removed from the engine, It can be re-installed using "procedure A" as long as the crankshaft has not rotated from its Initial position. if the intake manifold, cylinder head, crankshaft, camshaft, timing gear or complete engine was removed or replaced, "procedure B" must be followed to correctly install the distributor. A Diagnostic Trouble Code (DTC) code may also indicate an Incorrectly installed distributor and engine or distributor damage may occur. Procedure B must then be used. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 2848 Distributor: Adjustments Procedure A Distributor Installation and Removal Procedure A Remove or Disconnect ^ Make sure the ignition switch is "OFF." 1. Spark plug and coil leads from the distributor cap. 2. Three wire hail effect switch plug from the base of the distributor. 3. Two screws holding the distributor cap to the housing. 4. Distributor cap. A. Use a grease pencil to note the position of the rotor segment in relation to the distributor housing. Identify the mark with a 1. B. The distributor housing and intake manifold should also be marked with a grease pencil for proper alignment when reinstalling. 5. Mounting clamp hold down bolt. 6. Distributor. ^ As the distributor is being removed from the engine, you will notice the rotor move in a counter-clockwise direction, 42°. This will appear as slightly more than one clock position. Noting the position of the rotor segment, by placing a second mark on the base of the distributor, will aid in achieving proper rotor alignment during distributor installation. Be sure to identify the second mark on the base with the number 2. Install or Connect Distributor Alignment Indicator A. If the original distributor is to be replaced, rather than repaired, remove the new distributor cap. Using a grease pencil, place two marks on the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 2849 new distributor housing in the same location as the two marks on the original housing. B. When installing the distributor, align the rotor segment with the number 2 mark on the base of the distributor. Guide the distributor into place, making sure the grease pencil marks on the distributor housing and the intake manifold are in line. As the the distributor is being installed, you will notice the rotor will move in a clockwise direction, 42°. ONCE THE DISTRIBUT0R IS COMPLETELY SEATED, the rotor segment should be aligned with the number 1 mark on the base. If the rotor segment is not aligned with the number 1 mark, the gear teeth of the distributor and camshaft have meshed one or more teeth out of time. To correct this condition, remove the distributor and re-install it following the procedure at step B. 1. Distributor cap and mounting screws. Do not overtighten the screws as the boss may strip. 2. Distributor mounting clamp and tighten to proper torque. Tighten ^ Distributor clamp and bolt to 27 Nm (20 lbs. ft.) ^ Distributor cap screws to 4.5-5.0 Nm (40-45 lbs. in.) 3. Three wire hall effect switch connector to base of the distributor. 4. Spark plug and coil leads to the distributor cap. ^ If a check engine light is illuminated after installing the distributor and a DTC P1345 is found, the distributor has been installed incorrectly. You now must refer to procedure; B or proper distributor installation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 2850 Distributor: Adjustments Procedure B Distributor Installation and Removal Procedure B Remove or Disconnect ^ Make sure the ignition switch is "OFF." ^ Bring the engine up to Top Dead Center (TDC) of cylinder number 1. Make sure it is on the compression stroke. A. Remove the distributor cap screws and cap to expose the rotor. Rotor Location B. Align the pre-drilled indent hole in the distributor driven gear with the white painted alignment line on the lower portion of the shaft housing. The rotor segment should point to the cap hold area as shown in the illustration. C. Using a long screw driver, align the oil pump drive shaft in the engine in the mating drive tab in the distributor. D. Guide the distributor into place, making sure the the spark plug towers are perpendicular to the center line of the engine. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 2851 Installed Rotor Position E. ONCE The DISTRIBUTOR IS FULLY SEATED, the rotor segment should be aligned with the pointer cast into the distributor base. This pointer will have a "8" cast into it, indicating the distributor is to be used in a 8 cylinder engine. if the rotor segment does not come within a few degrees of the pointer, the gear mesh between the distributor and camshaft may be off a tooth or more. If this is the case, repeat the procedure again to achieve proper alignment. Install or Connect 1. Cap and mounting screws. Do not overtighten as the boss may strip. 2. Distributor mounting clamp and tighten to proper torque. Tighten ^ Distributor clamp and bolt to 27 Nm (20 lbs. ft.) ^ Distributor cap screws to 4.5-5.0 Nm (40-45 lbs. in.) 3. Three wire hall effect switch plug to base of distributor. 4. Spark plug and coil leads to the distributor cap. ^ If a check engine light is illuminated after installing the distributor and a DTC P1345 is found, the distributor has been installed incorrectly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation Distributor: Service and Repair Distributor Removal & Installation Distributor Removal 1. Remove the ignition coil wire harness from the ignition coil and distributor cap. 2. Remove two screws holding the distributor cap to the housing. 3. Distributor cap. 4. Remove the distributor clamp bolt. 5. Remove the distributor and the distributor clamp. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2854 6. Remove the distributor gasket and discard. Distributor Installation 1. Bring cylinder number one piston to Top Dead Center (TDC) of compression stroke. 2. Install the distributor cap screws. 3. Install the distributor cap. 4. Install a NEW distributor gasket onto the distributor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2855 5. Align the indent hole on the driven gear with the paint mark on the distributor housing. 5. Ensure that the distributor rotor segment points to the cap hold area. 7. Align the slotted tang in the oil pump driveshaft with the distributor driveshaft. Rotate the oil pump driveshaft with a screwdriver if necessary. 8. Align the flat (1) in the distributor housing toward the front of the engine. 9. Install the distributor and distributor clamp. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2856 10. Once the distributor is fully seated, align the distributor rotor segment with the number 8 pointer that is cast into the distributor base. 11. If the distributor rotor segment does not come within a few degrees of the number 8 pointer, the gear mesh between the distributor and camshaft may be off a tooth or more. Repeat the procedure in order to achieve proper alignment. Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems. 12. Install the distributor clamp bolt. Tighten the distributor clamp bolt to 25 Nm (18 ft. lbs.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2857 13. Install the distributor cap onto the distributor. 14. Install the NEW distributor cap screws. Do not overtighten the NEW distributor cap screws. Tighten the distributor cap screws to 2.4 Nm (21 in. lbs.). 15. Install the ignition coil wire harness. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2858 Distributor: Service and Repair Distributor Disassembly and Assembly Distributor Components NOTICE: The distributor driven gear can be installed in two positions. Make sure when installing the gear that the dimple found below the roll pin hole in the gear is on the same side as the rotor segment. The dimple will not align directly with the rotor segment if not, the gear is Installed 180° off and a no start condition may occur. Premature wear and damage may result. Remove or Disconnect 1. Two screws holding the cap to the housing. 2. Cap from the housing. 3. Two screws from the rotor. Vane Wheel In Distributor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2859 4. Rotor. ^ Note which locating holes (B) the rotor was removed from. 5. Two screws holding the hall effect switch. 6. Hall effect switch. ^ The square cut hole (C) in the vane wheel must be aligned with the hall effect switch in order to remove the switch. 7. Roil pin from the shaft. A. Note the dimple located below the roil pin hole on the one side of the gear. The dimple will be used to properly orient the gear on the shaft during assembly. 8. Driven gear, washer, and tang washer. 9. Shaft. ^ If the shaft can't be removed from the distributor housing due to varnish buildup, use a cloth dampened with varnish remover to clean the shaft. NOTICE: Failure to keep cleaning agents away from the hall effect switch may result in premature failure. Install or Connect 1. Hall effect switch. 2. Two screws holding the hall effect switch. Do not overtighten as the base may strip. 3. Shaft. 4. Tang washer, washer, and driven gear. ^ When the driven gear is properly installed the dimple located below the roll pin hole, in the driven gear, will be on the same side as the rotor segment when the rotor is installed in the distributor. If the driven gear is installed incorrectly, the dimple will be on the opposite of the rotor segment. 5. Roll pin. 6. Rotor. ^ "A" shows the mounting holes. "B" shows the locating holes. 7. Two screws holding rotor. Tighten ^ Screws to 2.0 Nm (20 lbs. In.) Installation of the distributor into the engine will require the distributor cap off of the assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2860 Distributor: Service and Repair Distributor Alignment/Camshaft Retard Offset Adjustment Description TEST PROCEDURE The ignition timing cannot be adjusted. The distributor may need adjusting to prevent crossfire. To insure proper alignment of the distributor, perform the following: 1. With the ignition OFF, install a scan tool to the DLC. 2. Start the engine and bring to normal operating temperature. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM. 3. Increase engine speed to 1000 RPM. 4. Monitor the Cam Retard Offset. 5. If the Cam Retard indicates a value of 0° +/-2°, the distributor is properly adjusted. 6. If the Cam Retard does not indicate 0° +/-2°, the distributor must be adjusted. ADJUSTING PROCEDURE 1. With the engine OFF, slightly loosen the distributor hold down bolt. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM. 2. Start the engine and raise engine speed to 1000 RPM. 3. Using a scan tool monitor Cam Retard Offset. 4. Rotate the distributor as follows: 4.1. To compensate for a negative reading, rotate the distributor in the counterclockwise direction. 4.2. To compensate for a positive reading, rotate the distributor in the clockwise direction. 5. Repeat step 4 until 0° +/-2°, is obtained. 6. Turn the ignition OFF. 7. Tighten the distributor hold-down bolt to 3 Nm (25 lb. ft.). 8. Start the engine, raise engine speed to 1000 RPM and recheck Camshaft Retard Offset. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2861 Distributor: Service and Repair Distributor Assembly Replacement Removal Procedure NOTICE: If the distributor is removed from the engine, It can be re-installed using "procedure A" as long as the crankshaft has not rotated from the original position. If the intake manifold, cylinder head, crankshaft, camshaft, timing gear or complete engine was removed or replaced, "Procedure B" must be followed in order to correctly install the distributor. A DTC code may also indicate an incorrectly installed distributor and engine or distributor damage may occur. Procedure B must then be used. 1. Turn OFF the ignition switch. 2. Remove the spark plug and the ignition coil wires from distributor cap. 3. Remove the three-wire hall effect switch connector from the base of the distributor. 4. Remove the two screws holding the distributor cap to the housing. 5. Remove the distributor cap. A. Use a grease pencil in order to note the position of the rotor in relation to the distributor housing. Identify the mark with the number 1. B. Mark the distributor housing and the intake manifold with a grease pencil for proper alignment when reinstalling. 6. Remove the mounting clamp hold down bolt. 7. Remove the distributor. 8. As the distributor is being removed from the engine, you will notice the rotor move in a counter-clockwise direction about 42 degrees. This will appear as slightly more than one clock position. Noting the position of the rotor segment by placing a second mark on the base of the distributor will aid in achieving proper rotor alignment during the distributor installation. Identify the second mark on the distributor housing at number 2. Installation Procedure A 1. Remove the new distributor cap. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2862 2. If installing a new distributor assembly, place two marks on the new distributor housing in the same location as the two marks on the original housing. 3. When installing the distributor, align the rotor with mark made at location 2.. 4. Guide the distributor into place, making sure the mounting hole in the distributor hold down base is aligned over the mounting hole in the intake manifold. 5. As the distributor is being installed, you will notice the rotor will move in a clockwise direction about 42 degrees. 6. Once the distributor is completely seated, the rotor segment should be aligned with mark on the base in location number 1. If the rotor segment is not aligned with the number 1 mark, the gear teeth of the distributor and the camshaft have meshed one or more teeth out of time. In order to correct the condition, remove the distributor and reinstall it. 7. Install the cap and the mounting screws. Do not overtighten as they may strip. Tighten Tighten the distributor cap screws to 5 Nm (45 lb in). NOTICE: Use the correct fasteners in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces inless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems. 8. Install the distributor clamp bolt. Tighten Tighten the distributor clamp bolt to to 27 Nm (20 lb ft). NOTICE: Use the correct fasteners in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2863 paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces inless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems. 9. Install the three wire hall effect switch connector to the base of the distributor. 10. Install the spark plug and the ignition coil wires to the distributor cap. Important: If a check engine light is illuminated after installing the distributor and a DTC P1345 is found, the distributor has been installed incorrectly. Refer to procedure B for proper distributor installation. Installation Procedure B 1. Rotate the number 1 cylinder up to Top Dead Center (TDC) of the compression stroke. 2. Remove the distributor cap screws and the distributor cap to expose the rotor. 3. Align the pre-drilled indent hole in the distributor driven gear with the white alignment line on the lower portion of the shaft housing. 4. The rotor should point to the cap hold down mount nearest the flat side of the housing. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 2864 5. Using a long screw driver, align the oil pump drive shaft to the drive tab of the distributor. 6. Guide the distributor in place, ensuring that the spark plug towers are perpendicular to the centerline of engine. 7. Once the distributor is fully seated, the rotor segment should be aligned with the pointer cast into the distributor base. This pointer will have a 6 or 8 cast into it, indicating that the distributor is to be used on a 6 or 8 cylinder engine. If the rotor segment does not come within a few degrees of the pointer, the gear mesh between the distributor and the camshaft may be off a tooth or more. If this is the case, repeat the procedure again in order to achieve proper alignment. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Spark Plug > Component Information > Specifications Spark Plug: Specifications Spark plug type .................................................................................................................................... ....................................................................... 41-932 Spark plug gap ................................................ ....................................................................................................................................................... 0.060 inch Spark plugs (new cylinder head) ........................................................................................ ........................................................................ 30 Nm (22 lb. ft.) Spark plugs (used cylinder head) ... ............................................................................................................................................................ 20 Nm (14 lb. ft.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Spark Plug > Component Information > Specifications > Page 2868 Spark Plug: Description and Operation DESCRIPTION Resistor-type. tapered-seat spark plugs are used. No gasket is used on these plugs. These spark plugs are a High Efficiency (HE) spark plug that has a fine wire electrode, nickel plated shell and a platinum pad across from the electrode. These features give the HE spark plug long life durability. Refer to Specifications or to the Vehicle Emissions Control Information label on the fan shroud for correct gap information. See: Specifications CONSTRUCTION If the spark plug shell hex is not fully engaged in the spark plug socket wrench, the socket may cock at an angle and cause insulator cracking and/or breakage during plug installation or removal. OPERATION Normal or average service is assumed to be a mixture of idling, low speed, and high speed operation with some of each making up the daily total driving. Occasional or intermittent high-speed driving is essential to good spark plug performance. It provides increased and sustained combustion heat that burns away any excess deposits of carbon or oxide that may have accumulated from frequent idling or continual stop-and-go or slow-speed driving. Spark plugs are protected by an insulating boot made of special heat-resistant material that covers the spark plug terminal and extends downward over a portion of the plug insulation These boots prevent flash-over with resultant missing of the engine, even though a film is allowed to accumulate on the exposed portion of plug porcelains. Do not mistake corona discharge for flash-over or a shorted insulator. Corona discharge is a steady blue light appearing around the insulator. just above the shell crimp It is the visible evidence of a high-tension field, and has no effect on ignition performance. Usually it can be detected only in darkness. This discharge may repel dust particles, leaving a clear ring on the insulator just above the shell. This ring is sometimes mistakenly regarded as evidence that combustion gases have blown out between the shell and insulator. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Spark Plug > Component Information > Specifications > Page 2869 Spark Plug Diagnosis Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Spark Plug > Component Information > Specifications > Page 2870 Spark Plug: Service and Repair CAUTION ^ Allow the engine to cool before removing the spark plugs. Attempting to remove the plugs from a hot engine may cause the plug to seize, causing damage to the cylinder head threads. ^ Clean the spark plug recess area before removing the plug. Failure to do so can result in engine damage due to dirt or foreign material entering the cylinder head or contamination of the cylinder head threads. Contaminated threads may prevent proper seating of a new plug. ^ Do not install plugs that are either hotter or colder than the heat range specified. Using plugs of the wrong heat range can severely damage the engine. REMOVE OR DISCONNECT ^ Make sure the ignition switch is OFF. CAUTION: Twist the spark plug boot one-half turn to release it. Pull on the spark plug boot only. Do not pull on the wire or the spark plug lead may be damaged. 1. Spark plug wires and boots. ^ Label the plug wires. CAUTION: Be sure to use J 39358 or equivalent spark plug socket Failure to do so could cause cracking of the insulator and arcing inside the plug, resulting in engine misfire. 2. Spark plugs using J 39358 or equivalent. Inspect ^ Each spark plug for wear and gap. ^ Spark plugs should be gapped to 0.060 inch. INSTALL OR CONNECT CAUTION: Make sure each sparkplug threads smoothly into the cylinder head and is fully seated. Cross-threading or falling to fully seat spark plugs can cause overheating of the plugs, exhaust blow-by, or thread damage. 1. Spark plugs. Tighten ^ Spark plugs to 30 Nm (22 lb. ft.) in a new cylinder head and 20 Nm (14 lb. ft.) in a used head. 2. Wire and boot assemblies. Refer to Spark Plug Wiring and Boots for precautions. See: Spark Plug Wire/Service Precautions Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Compression Check > System Information > Specifications Compression Check: Specifications Minimum, 698 kPa (100 psi) @ 200 rpm. The lowest cylinder reading should not be less than 80% of the highest. Perform compression test with engine at normal operating temperature, spark plugs removed and throttle wide open. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Valve Clearance > System Information > Specifications > Valve Clearance Specifications Valve Clearance: Specifications Valve Clearance Specifications One turn down from zero lash. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Valve Clearance > System Information > Specifications > Valve Clearance Specifications > Page 2878 Valve Clearance: Specifications Valve Arrangement FRONT TO REAR 5.7L/V8-350 ......................................................................................................................................... ........................................................... E-I-I-E-E-I-I-E Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Tune-up and Engine Performance Checks > Valve Clearance > System Information > Specifications > Page 2879 Valve Clearance: Adjustments 1. Remove rocker arm cover. 2. Crank engine until the mark on the vibration damper aligns with the "0 mark on the timing tab and the engine is in the number one firing position. This may be determined by placing fingers on valves of number one cylinder as the mark on the damper comes near the " 0 mark on the timing tab. If the rocker arms are not moving, the engine is in the number one firing position. If the rocker arms move as the marks comes up to the timing tab, the engine is in the number six firing position and should be turned over one more time to reach the number one firing position. 3. With the engine in this position, exhaust valves 1, 3, 4 and 8 and intake valves 1, 2, 5 and 7 can be adjusted. Even numbered cylinders are in the right bank, odd numbered cylinders are in the left bank when viewed from the rear of the engine. 4. Back off the adjusting nut until lash is felt at the pushrod, then turn in the adjusting nut until all lash is removed. This can be determined by rotating the pushrod while turning the adjusting nut. When play has been removed, turn the adjusting nut in one full additional turn. 5. Crank engine one complete revolution until the timing tab " 0 mark and vibration damper mark are aligned. This is the number six firing position. 6. With the engine in this position, exhaust valves 2, 5, 6 and 7 and intake valves 3, 4, 6 and 8 can be adjusted. 7. With valves properly adjusted, install rocker arm cover. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Engine > Water Pump > Component Information > Service and Repair Water Pump: Service and Repair Water pump replacement. 305/350 1. Disconnect battery ground cable. 2. Drain coolant from radiator. 3. Remove upper fan shroud. 4. Remove drive belt. 5. Remove fan assembly from engine. 6. Lower radiator and heater hose from the water pump. 7. Remove water pump attaching bolts and water pump, Fig. 15. 8. Reverse procedure to install. Tighten water pump attaching bolts to specifications. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Coolant > Component Information > Technical Service Bulletins > Cooling System - DEX-COOL(R) Coolant Leak Detection Dye Coolant: Technical Service Bulletins Cooling System - DEX-COOL(R) Coolant Leak Detection Dye Bulletin No.: 05-06-02-002B Date: January 18, 2008 INFORMATION Subject: DEX-COOL(R) Coolant - New Leak Detection Dye J 46366 - Replaces J 29545-6 Models: 1996-2008 GM Passenger Cars and Light/Medium Duty Trucks* (including Saturn) 1997-2008 Isuzu T-Series Medium Duty Tilt Cab Models Built in Janesville and Flint 1999-2008 Isuzu N-Series Medium Duty Commercial Models with 5.7L or 6.0L Gas Engine 2003-2008 HUMMER H2 2006-2008 HUMMER H3 2005-2008 Saab 9-7X *EXCLUDING 2006 and Prior Chevrolet Aveo, Epica, Optra, Vivant and Pontiac Matiz, Wave Supercede: This bulletin is being revised to include additional model years. Please discard Corporate Bulletin Number 05-06-02-002A (Section 06 - Engine/Propulsion System). Leak detection dye P/N 12378563 (J 29545-6) (in Canada P/N 88900915) may cause DEX-COOL(R) coolant to appear green in a black vessel making it appear to be conventional (green) coolant. This may cause a technician to add conventional coolant to a low DEX-COOL(R) system thus contaminating it. The green DEX-COOL(R) appearance is caused by the color of the leak detection dye which alters the color of the DEX-COOL(R) coolant. A new leak detection dye P/N 89022219 (J 46366) (in Canada P/N 89022220) has been released that does not alter the appearance of the DEX-COOL(R) coolant. When adding the new leak detection dye the color of the DEX-COOL(R) coolant will not change. For detecting leaks on any system that uses DEX-COOL(R) leak detection dye P/N 89022219 (in Canada P/N 89022220) should be used. The new leak detection dye can be used with both conventional and DEX-COOL(R) coolant. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Coolant > Component Information > Technical Service Bulletins > Cooling System - DEX-COOL(R) Coolant Leak Detection Dye > Page 2888 Coolant: Technical Service Bulletins Cooling System - Coolant Recycling Information Bulletin No.: 00-06-02-006D Date: August 15, 2006 INFORMATION Subject: Engine Coolant Recycling and Warranty Information Models: 2007 and Prior GM Passenger Cars and Trucks (Including Saturn) 2007 and Prior HUMMER Vehicles 2005-2007 Saab 9-7X Attention: Please address this bulletin to the Warranty Claims Administrator and the Service Manager. Supercede: This bulletin is being revised to adjust the title and Include Warranty Information. Please discard Corporate Bulletin Number 00-06-02-006C (Section 06 - Engine/Propulsion System). Coolant Reimbursement Policy General Motors supports the use of recycled engine coolant for warranty repairs/service, providing a GM approved engine coolant recycling system is used. Recycled coolant will be reimbursed at the GMSPO dealer price for new coolant plus the appropriate mark-up. When coolant replacement is required during a warranty repair, it is crucial that only the relative amount of engine coolant concentrate be charged, not the total diluted volume. In other words: if you are using two gallons of pre-diluted (50:50) recycled engine coolant to service a vehicle, you may request reimbursement for one gallon of GM Goodwrench engine coolant concentrate at the dealer price plus the appropriate warranty parts handling allowance. Licensed Approved DEX-COOL(R) Providers Important: USE OF NON-APPROVED VIRGIN OR RECYCLED DEX-COOL(R) OR DEVIATIONS IN THE FORM OF ALTERNATE CHEMICALS OR ALTERATION OF EQUIPMENT, WILL VOID THE GM ENDORSEMENT, MAY DEGRADE COOLANT SYSTEM INTEGRITY AND PLACE THE COOLING SYSTEM WARRANTY UNDER JEOPARDY. Shown in Table 1 are the only current licensed and approved providers of DEX-COOL(R). Products that are advertised as "COMPATIBLE" or "RECOMMENDED" for use with DEX-COOL(R) have not been tested or approved by General Motors. Non-approved coolants may degrade the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Coolant > Component Information > Technical Service Bulletins > Cooling System - DEX-COOL(R) Coolant Leak Detection Dye > Page 2889 coolant system integrity and will no longer be considered a 5 yr/150,000 mile (240,000 km) coolant. Coolant Removal Services/Recycling The tables include all coolant recycling processes currently approved by GM. Also included is a primary phone number and demographic information. Used DEX-COOL(R) can be combined with used conventional coolant (green) for recycling. Depending on the recycling service and/or equipment, it is then designated as a conventional 2 yr/30,000 mile (50,000 km) coolant or DEX-COOL(R) 5 yr/150,000 mile (240,000 km) coolant. Recycled coolants as designated in this bulletin may be used during the vehicle(s) warranty period. DEX-COOL(R) Recycling The DEX-COOL(R) recycling service listed in Table 2 has been approved for recycling waste engine coolants (DEX-COOL) or conventional) to DEX-COOL(R) with 5 yr/150,000 mile (240,000 km) usability. Recycling Fluid Technologies is the only licensed provider of Recycled DEX-COOL(R) meeting GM6277M specifications and utilizes GM approved inhibitor packages. This is currently a limited program being monitored by GM Service Operations which will be expanded as demand increases. Conventional (Green) Recycling Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Coolant > Component Information > Technical Service Bulletins > Cooling System - DEX-COOL(R) Coolant Leak Detection Dye > Page 2890 Processes shown in the Table 3 are capable of recycling waste engine coolants (DEX-COOL(R) or conventional) to a conventional (green) coolant. Recycling conventional coolant can be accomplished at your facility by a technician using approved EQUIPMENT (listed by model number in Table 3), or by an approved coolant recycling SERVICE which may recycle the coolant at your facility or at an offsite operation. Refer to the table for GM approved coolant recyclers in either of these two categories. Should you decide to recycle the coolant yourself, strict adherence to the operating procedures is imperative. Use ONLY the inhibitor chemicals supplied by the respective (GM approved) recycling equipment manufacturer. Sealing Tablets Cooling System Sealing Tablets (Seal Tabs) should not be used as a regular maintenance item after servicing an engine cooling system. Discoloration of coolant can occur if too many seal tabs have been inserted into the cooling system. This can occur if seal tabs are repeatedly used over the service life of a vehicle. Where appropriate, seal tabs may be used if diagnostics fail to repair a small leak in the cooling system. When a condition appears in which seal tabs may be recommended, a specific bulletin will be released describing their proper usage. Water Quality The integrity of the coolant is dependent upon the quality of DEX-COOL(R) and water. DEX-COOL(R) is a product that has enhanced protection capability as well as an extended service interval. These enhanced properties may be jeopardized by combining DEX-COOL(R) with poor quality water. If you suspect the water in your area of being poor quality, it is recommended you use distilled or de-ionized water with DEX-COOL(R). "Pink" DEX-COOL(R) DEX-COOL(R) is orange in color to distinguish it from other coolants. Due to inconsistencies in the mixing of the dyes used with DEX-COOL(R), some batches may appear pink after time. The color shift from orange to pink does not affect the integrity of the coolant, and still maintains the 5 yr/150,000 mile (240,000 km) service interval. Back Service Only use DEX-COOL(R) if the vehicle was originally equipped with DEX-COOL(R). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Coolant > Component Information > Technical Service Bulletins > Cooling System - DEX-COOL(R) Coolant Leak Detection Dye > Page 2891 Contamination Mixing conventional green coolant with DEX-COOL(R) will degrade the service interval from 5 yrs./150,000 miles (240,000 km) to 2 yrs./30,000 miles (50,000 km) if left in the contaminated condition. If contamination occurs, the cooling system must be flushed twice immediately and re-filled with a 50/50 mixture of DEX-COOL(R) and clean water in order to preserve the enhanced properties and extended service interval of DEX-COOL(R). After 5 years/150,000 miles (240,000 km) After 5 yrs/150,000 miles (240,000 km), the coolant should be changed, preferably using a coolant exchanger. If the vehicle was originally equipped with DEX-COOL(R) and has not had problems with contamination from non-DEX-COOL(R) coolants, then the service interval remains the same, and the coolant does not need to be changed for another 5 yrs/150,000 miles (240,000 km) Equipment (Coolant Exchangers) The preferred method of performing coolant replacement is to use a coolant exchanger. A coolant exchanger can replace virtually all of the old coolant with new coolant. Coolant exchangers can be used to perform coolant replacement without spillage, and facilitate easy waste collection. They can also be used to lower the coolant level in a vehicle to allow for less messy servicing of cooling system components. It is recommended that you use a coolant exchanger with a vacuum feature facilitates removing trapped air from the cooling system. This is a substantial time savings over repeatedly thermo cycling the vehicle and topping-off the radiator. The vacuum feature also allows venting of a hot system to relieve system pressure. Approved coolant exchangers are available through the GMDE (General Motors Dealer Equipment) program. For refilling a cooling system that has been partially or fully drained for repairs other than coolant replacement, the Vac-N-Fill Coolant Refill Tool (GE-47716) is recommended to facilitate removal of trapped air from the cooling system during refill. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Coolant > Component Information > Specifications > Capacity Specifications Coolant: Capacity Specifications Coolant Capacity, Qts. Less A/C .............................................................................................................................................. ........................................................................ 17.5 With A/C ............................................................. ........................................................................................................................................................... 20 Radiator Cap Relief Pressure, Lbs. ..................................................................................................... ............................................................................... 15 Thermo. Opening Temp., deg.F ..................... .............................................................................................................................................................. .... 195 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Coolant > Component Information > Specifications > Capacity Specifications > Page 2894 Coolant: Fluid Type Specifications ENGINE COOLANT A 50/50 mixture of clean water (preferably distilled) and use only GM Goodwrench DEX-COOL or Havoline DEX-COOL (orange-colored, silicate-free) coolant, or an approved recycled coolant conforming to GM Specification 6038-M (GM P/N 1052103). CAUTION: If silicate coolant is added to the cooling system, premature engine, heater core or radiator corrosion may result. In addition, the coolant will require change SOONER, at 50 000 km (30,000 miles) or 24 months. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Coolant Level Indicator Lamp > Component Information > Diagrams Low Coolant Level Indicator Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Coolant Level Indicator Lamp > Component Information > Diagrams > Page 2898 Coolant Level Indicator Lamp: Description and Operation This system uses a sensor mounted on the radiator and an indicator light mounted in the instrument panel to warn the driver if coolant level is too low. This light is wired in series with the ignition switch, ECM and the sensor. When the ignition switch is turned to the crank position, the circuit is energized and the indicator light will illuminate. When the ignition switch is turned to the ON position and coolant level is sufficient, the sensor will indicate this to the ECM and the light will turn off. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Coolant Level Indicator Lamp > Component Information > Testing and Inspection > Indicator Lamp Remains Illuminated Coolant Level Indicator Lamp: Testing and Inspection Indicator Lamp Remains Illuminated 1. Turn ignition switch to the On position, then check coolant level and add coolant as necessary. If lamp remains illuminated, proceed to step 2. 2. Disconnect electrical connector at the sensor. If lamp does not illuminate replace the sensor. If lamp remains illuminated, proceed to step 3. 3. Connect electrical lead to the sensor and check for an open circuit between the sensor and the module. Repair or replace as necessary. If circuit is satisfactory, replace the ECM. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Coolant Level Indicator Lamp > Component Information > Testing and Inspection > Indicator Lamp Remains Illuminated > Page 2901 Coolant Level Indicator Lamp: Testing and Inspection Indicator Lamp Will Not Illuminate 1. Turn ignition switch to the crank position, and proceed as follows: a. If lamp illuminates, lamp is satisfactory and connector is properly installed. Proceed to step 2. b. If lamp does not illuminate, check bulb, socket and wiring between socket and module connector. Replace or repair as necessary. 2. Turn ignition switch to the On position and disconnect electrical lead at coolant level sensor mounted on the radiator. If lamp fails to illuminate, check wiring between coolant level sensor connector and ECM for a short circuit to ground. If circuit is satisfactory, replace the ECM. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > A/C Pressure Sensor/Switch - Cooling Fan > Component Information > Locations A/C Pressure Sensor/Switch - Cooling Fan: Locations Front of Engine Compartment, on Condenser Manifold Tubing Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Locations > Component Locations Radiator Cooling Fan Motor: Component Locations Auxiliary Cooling Fan Auxiliary Cooling Fan Temperature Switch RH Cylinder Head, above Starter Solenoid Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Locations > Component Locations > Page 2910 Forward Lamps Harness, RH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions Radiator Cooling Fan Motor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2913 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2914 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2915 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2916 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2917 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2918 Radiator Cooling Fan Motor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2919 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2920 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2921 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2922 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2923 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2924 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2925 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2926 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2927 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2928 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2929 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2930 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2931 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2932 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2933 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2934 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2935 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2936 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2937 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2938 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2939 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2940 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2941 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2942 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2943 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2944 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 2945 Cooling Fan Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Description and Operation > Cooling System Radiator Cooling Fan Motor: Description and Operation Cooling System This auxiliary cooling fan circuit consists of a coolant temperature sensor, a relay and the fan. When the coolant sensor reaches a predetermined temperature, it closes the circuit to the relay coil, which energizes the relay, passing 12 volts to the fan. When the coolant temperature decreases below the set point of the sensor, the circuit to the relay opens and 12 volt power to the fan stops. The fan only operates when the ignition is on and the coolant temperature sensor is above the set temperature. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Description and Operation > Cooling System > Page 2948 Radiator Cooling Fan Motor: Description and Operation Circuit Operation Auxiliary Cooling Fan operating Voltage is available at all times from the 30 Amp AUX FAN Mini-Fuse located in the Underhood Fuse-Relay Center. Voltage is provided from the Fuse through the ORN (1540) wire which terminates at Pin 30 of the Auxiliary Cooling Fan Relay. When the Relay's Coil is energized, Relay contacts close to apply operating Voltage to the Auxiliary Cooling Fan Motor. The RED (702) wire connects Relay Pin 87 to Motor Pin B. The Motor is grounded from Pin A by the BLK (250) wire to Ground G112. Voltage to the Auxiliary Cooling Fan Relay Coil is available when the Ignition Switch is in RUN, BULB TEST or START. Relay Coil Voltage is supplied at Pin 85 by the PNK (639) wire from the 10 Amp IGN E Mini-Fuse located in the Underhood Fuse-Relay Center. The Auxiliary Cooling Fan Relay Coil is energized whenever either of two potential ground paths is provided. The LT GRN (37) wire connects Pin 86 of the Relay to Pin A of the Auxiliary Cooling Fan Temperature Switch and to the mode of Diode D100. Diode D100 enables current flow through the Auxiliary Cooling Fan A/C Pressure Switch when the Switch operates to ground the Relay Coil. When the Engine coolant reaches a set point, the Auxiliary Cooling Fan Temperature Switch closes the contacts. This provides a ground path from the Auxiliary Cooling Fan Relay Coil through the LT GRN (37) wire and through the Switch contacts to ground at the Engine. The Temperature Switch provides the ground connection at the Engine. The Relay Coil is energized, the contacts close, and the Fan Motor starts. The Auxiliary Cooling Fan will also operate when the Auxiliary Cooling Fan A/C Pressure Switch operates in response to an increasing compressor high side pressure. when the high side pressure increases to a set point, the Pressure Switch contacts close. This provides a ground path for the Auxiliary Cooling Fan Relay Coil through the LT GRN (37) wire to Diode D100. Through Diode D100, through the LT ORN (1614) wire, trough the Pressure Switch contacts and through the BLK (150) wire to Ground G105. The Relay Coil is energized, contacts close, and the Fan Motor starts. Operation of the Auxiliary Cooling Fan A/C Pressure Switch can also affect the position of the Air Conditioning Recirculation Door. During normal operation of the Recirculation Door, the A/C Controller places the door in the Recirculation position by grounding the Recirculation Door Motor. The ground path is through the DK GRN (1614) wire from door Pin A to A/C controller connector C3, Pin 4. When the ground path is removed, the Recirculation Door moves from the Recirculation Position. When the Auxiliary Cooling Fan A/C Pressure Switch operates to start the Auxiliary Cooling Fan, it also provides another ground path for the Recirculation Door Motor. If the Door Motor is not already grounded, it is now grounded from Pin 6 through the DK GRN (1614) wire, through Splice S212, through Diode D101, through Splice S114, and through the Pressure Switch to Ground G105. The Door Motor operates to place the Recirculation Door in the Recirculation Position. Diode D100 prevents the Recirculation Door Motor from being grounded by the Auxiliary Cooling Fan Temperature Switch. Diode D101 prevents operation of the Auxiliary Cooling Fan when the A/C Controller grounds the Recirculation Door Motor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Testing and Inspection > Initial Inspection and Diagnostic Overview Radiator Cooling Fan Motor: Initial Inspection and Diagnostic Overview 1. CHECK condition of IGN E Fuse and AUX FAN Fuse. If either Fuse is open, then LOCATE and REPAIR source of overload. Replace Fuse(s). 2. CHECK that Grounds G105, G112, and G200 are clean and tight. 3. CHECK that the Auxiliary Cooling Fan Relay is securely mounted in its socket. 4. If the Recirculation Door Motor does not move to the Recirculation position when the Auxiliary Cooling Fan is operated by the Auxiliary Cooling Fan A/C Pressure Switch, then Diode D101 may have opened. 5. If the Auxiliary Cooling Fan operates when the A/C controller places the Recirculation Door in the Recirculation position, then Diode D101 may have shorted. 6. If the Recirculation Door moves to the Recirculation position in response to Auxiliary Cooling Fan operation by the Auxiliary Cooling Fan Temperature Switch, then Diode D100 may have shorted. 7. If the Auxiliary Cooling Fan operates in response to the Auxiliary Cooling Fan Temperature Switch but not in response to the Auxiliary Cooling Fan A/C Pressure Switch, then Diode D100 may have opened. CHECK for a broken (or partially broken) wire inside of the insulation which could cause system malfunction but prove "GOOD" in a Continuity/Voltage check with a system disconnected. These Circuits may be intermittent or resistive when loaded, and if possible, should be checked by monitoring for a Voltage drop with the system operational (under load). ^ CHECK for proper installation of aftermarket electronic equipment which may affect the integrity of other systems (Refer "Troubleshooting Procedures"). See: Diagrams/Diagnostic Aids Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Testing and Inspection > Initial Inspection and Diagnostic Overview > Page 2951 Radiator Cooling Fan Motor: Symptom Related Diagnostic Procedures Auxiliary Cooling Fan Does Not Operate Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Testing and Inspection > Initial Inspection and Diagnostic Overview > Page 2952 Auxiliary Cooling Fan Runs Continuously Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Testing and Inspection > Initial Inspection and Diagnostic Overview > Page 2953 Radiator Cooling Fan Motor: Component Tests and General Diagnostics Auxiliary Cooling Fan operating Voltage is available at all times from the 30 Amp AUX FAN Mini-Fuse located in the Underhood Fuse-Relay Center. Voltage is provided from the Fuse through the ORN (1540) wire which terminates at Pin 30 of the Auxiliary Cooling Fan Relay. When the Relay's Coil is energized, Relay contacts close to apply operating Voltage to the Auxiliary Cooling Fan Motor. The RED (702) wire connects Relay Pin 87 to Motor Pin B. The Motor is grounded from Pin A by the BLK (250) wire to Ground G112. Voltage to the Auxiliary Cooling Fan Relay Coil is available when the Ignition Switch is in RUN, BULB TEST or START. Relay Coil Voltage is supplied at Pin 85 by the PNK (639) wire from the 10 Amp IGN E Mini-Fuse located in the Underhood Fuse-Relay Center. The Auxiliary Cooling Fan Relay Coil is energized whenever either of two potential ground paths is provided. The LT GRN (37) wire connects Pin 86 of the Relay to Pin A of the Auxiliary Cooling Fan Temperature Switch and to the mode of Diode D100. Diode D100 enables current flow through the Auxiliary Cooling Fan A/C Pressure Switch when the Switch operates to ground the Relay Coil. When the Engine coolant reaches a set point, the Auxiliary Cooling Fan Temperature Switch closes the contacts. This provides a ground path from the Auxiliary Cooling Fan Relay Coil through the LT GRN (37) wire and through the Switch contacts to ground at the Engine. The Temperature Switch provides the ground connection at the Engine. The Relay Coil is energized, the contacts close, and the Fan Motor starts. The Auxiliary Cooling Fan will also operate when the Auxiliary Cooling Fan A/C Pressure Switch operates in response to an increasing compressor high side pressure. when the high side pressure increases to a set point, the Pressure Switch contacts close. This provides a ground path for the Auxiliary Cooling Fan Relay Coil through the LT GRN (37) wire to Diode D100. Through Diode D100, through the LT ORN (1614) wire, trough the Pressure Switch contacts and through the BLK (150) wire to Ground G105. The Relay Coil is energized, contacts close, and the Fan Motor starts. Operation of the Auxiliary Cooling Fan A/C Pressure Switch can also affect the position of the Air Conditioning Recirculation Door. During normal operation of the Recirculation Door, the A/C Controller places the door in the Recirculation position by grounding the Recirculation Door Motor. The ground path is through the DK GRN (1614) wire from door Pin A to A/C controller connector C3, Pin 4. When the ground path is removed, the Recirculation Door moves from the Recirculation Position. When the Auxiliary Cooling Fan A/C Pressure Switch operates to start the Auxiliary Cooling Fan, it also provides another ground path for the Recirculation Door Motor. If the Door Motor is not already grounded, it is now grounded from Pin 6 through the DK GRN (1614) wire, through Splice S212, through Diode D101, through Splice S114, and through the Pressure Switch to Ground G105. The Door Motor operates to place the Recirculation Door in the Recirculation Position. Diode D100 prevents the Recirculation Door Motor from being grounded by the Auxiliary Cooling Fan Temperature Switch. Diode D101 prevents operation of the Auxiliary Cooling Fan when the A/C Controller grounds the Recirculation Door Motor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor > Component Information > Testing and Inspection > Page 2954 Radiator Cooling Fan Motor: Service and Repair Fig. 33 Auxiliary Cooling Fan Replacement Refer to Fig. 33 for auxiliary cooling fan replacement. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor Relay > Component Information > Locations Underhood Fuse-Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Fan Blade > Component Information > Technical Service Bulletins > Radiator Fan/Fan Blade Clutch - Revised Replacement Fan Blade: Technical Service Bulletins Radiator Fan/Fan Blade Clutch - Revised Replacement File In Section: 6 - Engine Bulletin No.: 66-62-O8 Date: June, 1996 SERVICE MANUAL UPDATE Subject: Section 6B - Cooling and Radiator - Revised Radiator Fan and Blade Clutch Replacement Models: 1996 Chevrolet and GMC C/K Models with 4.3L, 5.0L, 5.7L Engines (VINs W, M, R RPOs L35, L30, L31) This bulletin revises the radiator fan and fan blade clutch replacement procedure. The revised procedure includes the torque to apply to the fan and clutch bolts when using the J tool to install the fan and clutch assembly onto the water pump stud. Tools Required: J 41240 Fan Clutch Wrench Remove or Disconnect (Figure 1) Caution: To help avoid personal injury or damage to the vehicle, a bent, cracked or damaged fan blade or housing should always be replaced. 1. Upper fan shroud. Refer to "Fan Shroud Replacement" in this section. 2. Drive belt. Refer to "Drive Belt Replacement" in this section. 3. Fan and clutch using J 41240. 4. Fan blade from clutch. Caution: Do not use or repair a damaged fan assembly. An unbalanced fan assembly could fly apart and cause personal injury and/or property damage. Replace damaged assemblies with new assemblies. Install or Connect (Figure 1) 1. Fan blade to clutch. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Fan Blade > Component Information > Technical Service Bulletins > Radiator Fan/Fan Blade Clutch - Revised Replacement > Page 2962 Tighten Tighten bolts to 23 N.m (17 lb ft) 2. Fan and clutch using J 41240. Tighten Tighten fan clutch nut to 56 N.m (41 lb ft) 3. Drive belt. 4. Upper fan shroud. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Fan Blade > Component Information > Service Precautions > Technician Safety Information Fan Blade: Technician Safety Information WARNING: Do not operate engine until fan has first been inspected for cracks and/or separations. If a fan blade is found to be bent or damaged in any way, do not attempt to repair or reuse damaged part. Proper balance is essential in fan assembly operation. Balance cannot be assured once a fan assembly has been found to be bent or damaged and failure may occur during operation, creating an extremely dangerous condition. Always replace damaged fan assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Fan Blade > Component Information > Service Precautions > Technician Safety Information > Page 2965 Fan Blade: Vehicle Damage Warnings WARNING: Do not operate engine until fan has first been inspected for cracks and/or separations. If a fan blade is found to be bent or damaged in any way, do not attempt to repair or reuse damaged part. Proper balance is essential in fan assembly operation. Balance cannot be assured once a fan assembly has been found to be bent or damaged and failure may occur during operation, creating an extremely dangerous condition. Always replace damaged fan assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Fan Clutch > Component Information > Technical Service Bulletins > A/T - Intermittent Downshift/Slip/Cycling Diagnosis Fan Clutch: Technical Service Bulletins A/T - Intermittent Downshift/Slip/Cycling Diagnosis File In Section: 07 Transmission/Transaxle Bulletin No.: 99-07-30-016B Date: October, 2002 INFORMATION Subject: Diagnostic Information For Intermittent Transmission Downshift, Slip, Busy/cycling TCC or Noisy Cooling Fan Models: 1999-2000 Cadillac Escalade 2002-2003 Cadillac Escalade, Escalade EXT 1988-2003 Chevrolet Astro, Blazer, S-10, Silverado, Suburban 1989-2003 Chevrolet/Geo Tracker 1995-2003 Chevrolet Tahoe 1996-2003 Chevrolet Express 1988-1994 GMC S-15 1988-1999 GMC Suburban 1988-2003 GMC Safari, Sierra 1995-2003 GMC Sonoma, Yukon, Yukon XL 1996-2003 GMC Savana 1999-2001 GMC Envoy 1991-2001 Oldsmobile Bravada 2003 HUMMER H2 with Air Conditioning This bulletin is being revised to change the Model information and text. Please discard Corporate Bulletin Number 99-07-30-016A (Section 07 - Transmission/Transaxle) Some customers may comment that at times the transmission seems to slip, or that there is a loud roar from the engine with slow acceleration. This condition is most noticeable after the vehicle has sat idle for 12 or more hours, or on hot days when the A/C is on and the vehicle moves slowly with traffic. Typical comments from customers may include the following conditions: ^ Intermittent slipping ^ Intermittent downshift followed by an upshift, both with no apparent reason ^ Busyness or cycling of the TCC (torque converter clutch) at steady throttle conditions and on a level roadway ^ Noisy cooling fan The type of concern described above requires further definition. The customer should be asked the following questions: ^ Is the situation more pronounced with higher vehicle loads such as when pulling a trailer? ^ Do warmer ambient temperatures make the situation more pronounced? ^ When the condition occurred, did you have the A/C on, and were you driving in stop and go city traffic? ^ Does the condition exhibit itself on the first start-up after sitting more than eight hours? If the customer indicates that these conditions apply, and your observation confirms that the vehicle is operating properly, provide the customer with the vehicle operating description included at the end of this bulletin. Further action may not be necessary. A service procedure follows if further definition is required. Diagnostic Aids Cooling fan operation or the resulting sound varies. The cooling fan clutch may be described as a continuously variable clutch. If the vehicle engine is running, the fan blade is always turning unless the fan clutch is non-functional. The speed of the fan in relation to engine speed is temperature dependent. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Fan Clutch > Component Information > Technical Service Bulletins > A/T - Intermittent Downshift/Slip/Cycling Diagnosis > Page 2970 Maximum fan speed (air flow and related fan noise) through the engine compartment is experienced under two conditions. 1. When the vehicle sits in an unused condition for several hours, the viscous fluid within the thermostatic fan clutch assembly migrates and fully engages the clutch of the fan. After a short drive, the viscous fluid will migrate to the storage area in the fan clutch and the fan clutch will slip, reducing the noise (roar of the fan). This is normal thermostatic fan clutch operation. 2. When the engine is running, and the air being drawn by the fan or pushed through the radiator from the vehicle movement reaches a high enough temperature, the fan clutch will fully engage the fan clutch, drawing additional air through the radiator to lower the engine coolant temperature and A/C refrigerant temperature. When the cooling fan clutch fully engages, fan noise increases (for example; this is the same as switching an electric household fan from low to high speed). Some customers have interpreted this sound increase to be an increase in the engine RPM due to transmission downshift, transmission slipping, or TCC cycling. As the engine coolant temperature decreases, the fan clutch will begin to slip, lowering the actual speed of the fan blade and the resultant sound. Service Procedure When diagnosing an intermittent transmission downshift, slip, or busy/cycling TCC, follow these steps: 1. Verify the transmission fluid level and the fluid condition. Refer to the Automatic Transmission sub-section of the appropriate Service Manual. 2. Test drive the vehicle under the conditions described by the customer (ambient temperature, engine coolant temperature, trailering, etc.). It may be necessary to partially restrict airflow to the radiator in order to raise the engine coolant temperature to match the customer's conditions. 3. Monitor the engine RPM and the engine coolant temperature using a scan tool. 4. Listen for an actual increase in the engine RPM. Use either the vehicle tachometer (if equipped), the Tech 2 RPM or transmission slip speed as an indicator, rather than just the sound. If the engine RPM display on the tachometer or the Tech 2 increases, verify the scan tool RPM and coolant temperature readings. If the noise increase is due to the engagement of the fan, the engine RPM will not increase and the engine coolant temperature will begin to decrease after the fan engages. As the fan runs, the engine coolant temperature will drop and the fan will disengage, reducing noise levels. The engine RPM will not decrease. This cycle will repeat as the engine coolant temperature rises again. If the above procedure shows the condition to be cooling fan-related, no further action is necessary. The vehicle should be returned to the customer and the condition explained. If the above procedure shows the condition to be other than cooling fan-related, refer to the Automatic Transmission sub-section of the appropriate Service Manual for transmission diagnosis information. The following information regarding the operation of the engine cooling fan should be photocopied and given to the customer. Intermittent Transmission Downshift All light duty trucks are equipped with a thermostatic engine cooling fan. This fan is designed to provide greater fuel efficiency and quieter operation than a standard fan. These benefits are possible through the addition of a thermostatic clutch to the fan drive. When the engine is cool (it the engine has been run in the last few hours), the clutch allows the fan to "slip" or turn at a speed slower than the engine. By turning at a slower speed, the fan uses less horsepower, which saves fuel, and is quieter. When the engine temperature reaches a preset temperature or if the engine has not been run for several hours, the fan "engages" and turns at the same speed as the engine. "Engagement" of the fan provides increased airflow through the radiator to cool the engine. As the airflow increases, fan operation becomes clearly audible. This increase in noise can easily be mistaken for an increase in engine RPM and may be incorrectly blamed on the automatic transmission. When operating an unloaded vehicle in cooler ambient temperatures, the thermostatic clutch usually won't fully engage. However, if the vehicle is pulling a trailer, is heavily loaded or is operated at high ambient temperatures, the thermostatic fan clutch may cycle on and off as the engine coolant temperature rises and falls. The sound of fan operation under the conditions described above is a sign that the cooling system on your vehicle is working correctly. Replacement or modification of the cooling system or the transmission parts will not change or reduce the noise level. Attempts to reduce this noise may cause you, the customer, to believe that your vehicle is not reliable and will inconvenience you by causing your vehicle to be out of service. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Fan Clutch > Component Information > Technical Service Bulletins > A/T - Intermittent Downshift/Slip/Cycling Diagnosis > Page 2971 DISCLAIMER Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Fan Clutch > Component Information > Technical Service Bulletins > A/T - Intermittent Downshift/Slip/Cycling Diagnosis > Page 2972 Fan Clutch: Technical Service Bulletins Radiator Fan/Fan Blade Clutch - Revised Replacement File In Section: 6 - Engine Bulletin No.: 66-62-O8 Date: June, 1996 SERVICE MANUAL UPDATE Subject: Section 6B - Cooling and Radiator - Revised Radiator Fan and Blade Clutch Replacement Models: 1996 Chevrolet and GMC C/K Models with 4.3L, 5.0L, 5.7L Engines (VINs W, M, R RPOs L35, L30, L31) This bulletin revises the radiator fan and fan blade clutch replacement procedure. The revised procedure includes the torque to apply to the fan and clutch bolts when using the J tool to install the fan and clutch assembly onto the water pump stud. Tools Required: J 41240 Fan Clutch Wrench Remove or Disconnect (Figure 1) Caution: To help avoid personal injury or damage to the vehicle, a bent, cracked or damaged fan blade or housing should always be replaced. 1. Upper fan shroud. Refer to "Fan Shroud Replacement" in this section. 2. Drive belt. Refer to "Drive Belt Replacement" in this section. 3. Fan and clutch using J 41240. 4. Fan blade from clutch. Caution: Do not use or repair a damaged fan assembly. An unbalanced fan assembly could fly apart and cause personal injury and/or property damage. Replace damaged assemblies with new assemblies. Install or Connect (Figure 1) 1. Fan blade to clutch. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Fan Clutch > Component Information > Technical Service Bulletins > A/T - Intermittent Downshift/Slip/Cycling Diagnosis > Page 2973 Tighten Tighten bolts to 23 N.m (17 lb ft) 2. Fan and clutch using J 41240. Tighten Tighten fan clutch nut to 56 N.m (41 lb ft) 3. Drive belt. 4. Upper fan shroud. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Fan Clutch > Component Information > Technical Service Bulletins > Page 2974 Fan Clutch: Description and Operation Fan Drive Clutch Assembly Variable Speed Fan W/Bi-Metallic Coiled Thermostatic Spring The fan drive clutch, Fig. 1, is a fluid coupling containing silicone oil. Fan speed is regulated by the torque-carrying capacity of the silicone oil. The more silicone oil in the coupling, the greater the fan speed, and the less silicone oil, the slower the fan speed. The type of fan drive clutch in use is a coiled bimetallic thermostatic spring, Fig. 2. The fan drive clutch uses a heat-sensitive, coiled bimetallic spring connected to an opening plate which regulates the flow of silicone oil into the coupling from a reserve chamber. The silicone oil is returned to the reserve chamber through a bleed hole when the valve is closed. This unit causes the fan speed to increase with a rise in temperature and to decrease as temperature decreases. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Fan Clutch > Component Information > Testing and Inspection > Clutch Fluid Leak Fan Clutch: Testing and Inspection Clutch Fluid Leak Small fluid leaks do not generally affect the operation of the unit. These leaks generally occur around the area of the bearing assembly, but if the leaks appear to be excessive, engine overheating may occur. Clutch and fan free-wheeling can cause overheating. To check for clutch and fan free-wheeling, turn the motor "OFF." Spin the fan and clutch assembly by hand. If the fan spins five or more times before it stops, replace the clutch. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Fan Clutch > Component Information > Testing and Inspection > Clutch Fluid Leak > Page 2977 Fan Clutch: Testing and Inspection Engine Overheating 1. Start with cool engine to ensure complete fan clutch disengagement. 2. If fan and clutch assembly free wheels with no drag (revolves more than five times when spun by hand), replace clutch. If clutch performs properly with slight drag, proceed to following step. 3. Position thermometer so it is located between fan blades and radiator, noting the following: a. Insert thermometer sensor through one of existing holes in fan shroud or place between radiator and shroud. It may be necessary to drill a 3/16 inch hole in fan shroud to insert thermometer. b. Check for adequate clearance between fan blades and thermometer sensor before starting engine, as damage could occur. 4. With thermometer in position, cover radiator grill sufficiently to induce high engine temperature. 5. Start engine, then turn on air conditioning and operate at 2000 RPM. 6. Observe thermometer reading when clutch disengages, noting the following: a. It will take approximately five to ten minutes for temperature to become high enough to allow engagement of fan clutch. This will be indicated by a 5-15 degrees F drop in thermometer reading. b. If clutch did not engage between 150-195 degrees F, unit should be replaced. Ensure fan clutch was disengaged at beginning of test. c. If no sharp increase in fan noise or temperature drop was observed and fan noise level was constantly high from start of test to 190 degrees F, unit should be replaced. Do not continue this test past thermometer reading of 190 degrees F to prevent engine overheating. 7. As soon as clutch engages, remove radiator grill cover and turn A/C off to assist in engine cooling. Run engine at approximately 1500 RPM. 8. After several minutes, fan clutch should disengage as indicated by reduction in fan speed and roar. If fan clutch fails to function as described, replace it. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Fan Clutch > Component Information > Testing and Inspection > Clutch Fluid Leak > Page 2978 Fan Clutch: Testing and Inspection Fan Clutch Noise Fan clutch noise can sometimes be noticed when clutch is engaged for maximum cooling. Clutch noise is also noticeable within the first few minutes after starting engine while clutch is redistributing the silicone fluid back to its normal, disengaged operating condition after settling for long periods of time (overnight). However, continuous fan noise or an excessive roar indicates the clutch assembly is locked-up due to internal failure. This condition can be checked by attempting to manually rotate fan. If fan cannot be rotated manually or there is a rough, abrasive feel as fan is rotated, the clutch should be replaced. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Fan Clutch > Component Information > Testing and Inspection > Clutch Fluid Leak > Page 2979 Fan Clutch: Testing and Inspection Fan Looseness Lateral movement can be observed at the fan blade tip under various temperature conditions because of the type bearing used. This movement should not exceed 1/4 inch (6.5 mm) as measured at the fan tip. If this lateral movement does not exceed specifications, there is no cause for replacement. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Fan Clutch > Component Information > Testing and Inspection > Page 2980 Fan Clutch: Service and Repair To prevent silicone fluid from draining into fan drive bearing, do not store or place drive unit on bench with rear of shaft pointing downward. The coil spring type fan clutch cannot be disassembled, serviced or repaired. If it does not function properly, it must be replaced with a new unit. To replace the fan clutch, use the following procedure: 1. Remove the radiator fan shroud. 2. Unfasten the unit from the water pump, then remove the assembly from vehicle. 3. Separate fan from fan clutch. 4. Reverse procedure to install, noting the following: a. Ensure mating surfaces of water pump hub and fan clutch hub are smooth and free of any burrs. b. Align yellow reference marks on water pump hub and fan clutch hub. c. Torque nuts to 18 ft. lbs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Specifications Coolant Temperature Sensor/Switch (For Computer): Specifications Engine Coolant Temperature (ECT) sensor .............................................................................................................................................. 13 Nm (10 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Specifications > Page 2985 Engine Side, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions Coolant Temperature Sensor/Switch (For Computer): Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 2988 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 2989 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 2990 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 2991 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 2992 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 2993 Coolant Temperature Sensor/Switch (For Computer): Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 2994 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 2995 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 2996 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 2997 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 2998 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 2999 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3000 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3001 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3002 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3003 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3004 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3005 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3006 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3007 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3008 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3009 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3010 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3011 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3012 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3013 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3014 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3015 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3016 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3017 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3018 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3019 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3020 ECT Sensor Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 3021 Coolant Temperature Sensor/Switch (For Computer): Description and Operation Engine Coolant Temperature (ECT) Sensor DESCRIPTION The engine coolant temperature sensor is a thermistor (a resistor which changes value based on temperature) mounted in the engine coolant passage. Low coolant temperature produces a high resistance 100,000 ohms at -40°C (-40°F) while high temperature causes low resistance 70 ohms at 130°C (266°F). OPERATION The VCM supplies a 5 volt signal to the engine coolant temperature sensor through a resistor in the VCM and measures the voltage. The voltage will be high when the engine is cold. The voltage will be low when the engine is hot. By measuring the voltage, the VCM calculates the engine coolant temperature. Engine coolant temperature affects most systems the VCM controls. The scan tool displays engine coolant temperature in degrees. After engine start-up, the temperature should rise steadily to about 9O°C (194°F) then stabilize when thermostat opens. If the engine has not been run for several hours (overnight), the engine coolant temperature and intake air temperature displays should be close to each other. When the VCM detects a malfunction in the Engine Coolant Temperature (ECT) sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0117 circuit low. ^ DTC P0118 circuit high. ^ DTC P0125 excessive time to Closed Loop. ^ DTC P1114 circuit intermittent low. ^ DTC P1115 circuit intermittent high. The above DTCs contain a table to check for sensor resistance values relative to temperature. Refer to Specifications. See: Powertrain Management/Computers and Control Systems/Specifications Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 3022 Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection The scan tool displays engine coolant temperature in degrees. After engine start-up, the temperature should rise steadily to about 90°C (194°F) then stabilize when thermostat opens. If the engine has not been run for several hours (overnight), the engine coolant temperature and intake air temperature displays should be close to each other. When the VCM detects a malfunction in the Engine Coolant Temperature (ECT) sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0117 circuit low. ^ DTC P0118 circuit high. ^ DTC P0125 excessive time to Closed Loop. ^ DTC P1114 circuit intermittent low. ^ DTC P1115 circuit intermittent high. The above DTCs contain a table to check for sensor resistance values relative to temperature. Refer to Diagnostic Tables. See: Powertrain Management/Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 3023 Coolant Temperature Sensor/Switch (For Computer): Service and Repair Engine Coolant Temperature (ECT) Sensor Electrical Connector Engine Coolant Temperature (ECT) Sensor CAUTION: Use care when handling the coolant sensor. Damage to the coolant sensor will affect the operation of the fuel control system. REMOVAL PROCEDURE 1. Relieve the coolant pressure. 2. Disconnect the negative battery cable. 3. Drain the cooling system below the level of the sensor. 4. Disconnect the electrical connector releasing locking tab. 5. Remove the coolant sensor from engine. INSTALLATION PROCEDURE 1. Coat the threads (only) with sealer P/N 9985253 or equivalent. Tighten ^ Tighten the sensor to 13 N.m (10 lb. ft.). 2. Install the coolant sensor in the engine. 3. Connect the electrical connector. 4. Refill the cooling system. 5. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Temperature Sensor (Gauge) > Component Information > Locations Temperature Sensor (Gauge): Locations Engine Side, LH LH cylinder head, near number one spark plug. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Heater Control Valve > Component Information > Locations Heater Control Valve: Locations Engine Compartment, RH rear side of Inner Fender Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Heater Control Valve > Component Information > Locations > Page 3030 Heater Control Valve: Service and Repair Heater Water Valve Remove or Disconnect 1. Engine coolant. 2. Hose clamps at heater water valve. - Loosen the clamps enough to slide the clamps away from the fittings on the valve. 3. Hoses from valve. 4. Vacuum line from valve. 5. Valve. Install or Connect 1. Vacuum line to valve. 2. Hoses to valve. 3. Clamps to hoses. - Slide clamps to previous location beyond retaining bead on water valve fitting. 4. Engine coolant. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Heater Core > Component Information > Technical Service Bulletins > Cooling System, A/C - Aluminum Heater Cores/Radiators Heater Core: Technical Service Bulletins Cooling System, A/C - Aluminum Heater Cores/Radiators INFORMATION Bulletin No.: 05-06-02-001A Date: July 16, 2008 Subject: Information On Aluminum Heater Core and/or Radiator Replacement Models: 2005 and Prior GM Passenger Cars and Light Duty Trucks (including Saturn) 2003-2005 HUMMER H2 Supercede: This bulletin is being revised to update the Warranty Information. Please discard Corporate Bulletin Number 05-06-02-001 (Section 06 - Engine/Propulsion System). Important: 2004-05 Chevrolet Aveo (Pontiac Wave, Canada Only) does not use DEX-COOL(R). Refer to the flushing procedure explained later in this bulletin. The following information should be utilized when servicing aluminum heater core and/or radiators on repeat visits. A replacement may be necessary because erosion, corrosion, or insufficient inhibitor levels may cause damage to the heater core, radiator or water pump. A coolant check should be performed whenever a heater core, radiator, or water pump is replaced. The following procedures/ inspections should be done to verify proper coolant effectiveness. Caution: To avoid being burned, do not remove the radiator cap or surge tank cap while the engine is hot. The cooling system will release scalding fluid and steam under pressure if the radiator cap or surge tank cap is removed while the engine and radiator are still hot. Important: If the vehicle's coolant is low, drained out, or the customer has repeatedly added coolant or water to the system, then the system should be completely flushed using the procedure explained later in this bulletin. Technician Diagnosis ^ Verify coolant concentration. A 50% coolant/water solution ensures proper freeze and corrosion protection. Inhibitor levels cannot be easily measured in the field, but can be indirectly done by the measurement of coolant concentration. This must be done by using a Refractometer J 23688 (Fahrenheit scale) or J 26568 (centigrade scale), or equivalent, coolant tester. The Refractometer uses a minimal amount of coolant that can be taken from the coolant recovery reservoir, radiator or the engine block. Inexpensive gravity float testers (floating balls) will not completely analyze the coolant concentration fully and should not be used. The concentration levels should be between 50% and 65% coolant concentrate. This mixture will have a freeze point protection of -34 degrees Fahrenheit (-37 degrees Celsius). If the concentration is below 50%, the cooling system must be flushed. ^ Inspect the coolant flow restrictor if the vehicle is equipped with one. Refer to Service Information (SI) and/or the appropriate Service Manual for component location and condition for operation. ^ Verify that no electrolysis is present in the cooling system. This electrolysis test can be performed before or after the system has been repaired. Use a digital voltmeter set to 12 volts. Attach one test lead to the negative battery post and insert the other test lead into the radiator coolant, making sure the lead does not touch the filler neck or core. Any voltage reading over 0.3 volts indicates that stray current is finding its way into the coolant. Electrolysis is often an intermittent condition that occurs when a device or accessory that is mounted to the radiator is energized. This type of current could be caused from a poorly grounded cooling fan or some other accessory and can be verified by watching the volt meter and turning on and off various accessories or engage the starter motor. Before using one of the following flush procedures, the coolant recovery reservoir must be removed, drained, cleaned and reinstalled before refilling the system. Notice: ^ Using coolant other than DEX‐COOL(R) may cause premature engine, heater core or radiator corrosion. In addition, the engine coolant may require changing sooner, at 30,000 miles (50,000 km) or 24 months, whichever occurs first. Any repairs would not be covered by your warranty. Always use DEX‐COOL(R) (silicate free) coolant in your vehicle. ^ If you use an improper coolant mixture, your engine could overheat and be badly damaged. The repair cost would not be covered by your warranty. Too much water in the mixture can freeze and crack the engine, radiator, heater core and other parts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Heater Core > Component Information > Technical Service Bulletins > Cooling System, A/C - Aluminum Heater Cores/Radiators > Page 3035 Flushing Procedures using DEX-COOL(R) Important: The following procedure recommends refilling the system with DEX-COOL(R), P/N 12346290 (in Canada, use P/N 10953464), GM specification 6277M. This coolant is orange in color and has a service interval of 5 years or 240,000 km (150,000 mi). However, when used on vehicles built prior to the introduction of DEX-COOL(R), maintenance intervals will remain the same as specified in the Owner's Manual. ^ If available, use the approved cooling system flush and fill machine (available through the GM Dealer Equipment Program) following the manufacturer's operating instructions. ^ If approved cooling system flush and fill machine is not available, drain the coolant and dispose of properly following the draining procedures in the appropriate Service Manual. Refill the system using clear, drinkable water and run the vehicle until the thermostat opens. Repeat and run the vehicle three (3) times to totally remove the old coolant or until the drained coolant is almost clear. Once the system is completely flushed, refill the cooling system to a 50%-60% concentration with DEX‐COOL(R), P/N 12346290 (in Canada, use P/N 10953464), GM specification 6277M, following the refill procedures in the appropriate Service Manual. If a Service Manual is not available, fill half the capacity of the system with 100% DEX-COOL(R), P/N 12346290 (in Canada, use P/N 10953464), GM specification 6277M. Then slowly add clear, drinkable water (preferably distilled) to the system until the level of the coolant mixture has reached the base of the radiator neck. Wait two (2) minutes and reverify the coolant level. If necessary, add clean water to restore the coolant to the appropriate level. Once the system is refilled, reverify the coolant concentration using a Refractometer J 23688 (Fahrenheit scale) or J 26568 (centigrade scale) coolant tester, or equivalent. The concentration levels should be between 50% and 65%. Flushing Procedures using Conventional Silicated (Green Colored) Coolant Important: 2004-2005 Chevrolet Aveo (Pontiac Wave, Canada Only) does not use DEX‐COOL(R). The Aveo and Wave are filled with conventional, silicated engine coolant that is blue in color. Silicated coolants are typically green in color and are required to be drained, flushed and refilled every 30,000 miles (48,000 km). The Aveo and Wave are to be serviced with conventional, silicated coolant. Use P/N 12378560 (1 gal) (in Canada, use P/N 88862159 (1 L). Refer to the Owner's Manual or Service Information (SI) for further information on OEM coolant. Important: Do not mix the OEM orange colored DEX-COOL(R) coolant with green colored coolant when adding coolant to the system or when servicing the vehicle's cooling system. Mixing the orange and green colored coolants will produce a brown coolant which may be a customer dissatisfier and will not extend the service interval to that of DEX-COOL(R). Conventional silicated coolants offered by GM Service and Parts Operations are green in color. ^ If available, use the approved cooling system flush and fill machine (available through the GM Dealer Equipment Program) following the manufacturer's operating instructions. ^ If approved cooling systems flush and fill machine is not available, drain coolant and dispose of properly following the draining procedures in appropriate Service Manual. Refill the system using clear, drinkable water and run vehicle until thermostat opens. Repeat and run vehicle three (3) times to totally remove old coolant or until drained coolant is almost clear. Once the system is completely flushed, refill the cooling system to a 50%-60% concentration with a good quality ethylene glycol base engine coolant, P/N 12378560, 1 gal (in Canada, use P/N 88862159 1 L), conforming to GM specification 1825M, or recycled coolant conforming to GM specification 1825M, following the refill procedures in the appropriate Service Manual. If a Service Manual is not available, fill half the capacity of the system with 100% good quality ethylene glycol base (green colored) engine coolant, P/N 12378560 1 gal., (in Canada, use P/N 88862159 1 L) conforming to GM specification 1825M. Then slowly add clear, drinkable water (preferably distilled) to system until the level of the coolant mixture has reached the base of the radiator neck. Wait two (2) minutes and recheck coolant level. If necessary, add clean water to restore coolant to the appropriate level. Once the system is refilled, recheck the coolant concentration using a Refractometer J 23688 (Fahrenheit scale) or J 26568 (centigrade scale) coolant tester, or equivalent. Concentration levels should be between 50% and 65%. Parts Information Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Heater Core > Component Information > Technical Service Bulletins > Cooling System, A/C - Aluminum Heater Cores/Radiators > Page 3036 For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Heater Core > Component Information > Technical Service Bulletins > Page 3037 Heater Core: Description and Operation PURPOSE In any air conditioning mode, the heater core heats the cool, dehumidified air to achieve the desired temperature. The position of the control assembly temperature rotary knob determines how much heat is added to the incoming air. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Heater Core > Component Information > Service and Repair > With Air Conditioning Heater Core: Service and Repair With Air Conditioning HEATER CORE Remove or Disconnect 1. Engine coolant. 2. Instrument panel storage compartment. 3. Electrical connectors, as necessary. 4. Center floor air distribution duct. 5. Hinge pillar trim panels. 6. Blower motor cover. 7. Blower motor. 8. Steering column. 9. Roll instrument panel back. 10. Coolant recovery reservoir. 11. Heater hoses. 12. Screw on interior side of cowl, near the evaporator pipe (if equipped) while holding heater case to the cowl. 13. Four screws on the engine side of the cowl holding the heater case to the cowl. 14. Two nuts on the engine side of the cowl holding the heater case to the cowl. 15. Heater case. - It may be necessary to have an assistant when removing heater case. 16. Heater cover. - Remove seven screws that hold cover to the heater case. 17. Heater core from retainer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Heater Core > Component Information > Service and Repair > With Air Conditioning > Page 3040 Install or Connect 1. Heater core into retainer. - Install seven screws that hold heater cover to heater case. 2. Heater cover. - Make sure heater cover is properly sealed. 3. Heater case. - May be necessary to have an assistant when installing heater case. 4. Nuts. 5. Screws. Tighten - Screws on engine side of the cowl to 1.9 Nm (17 lb in). - uts to 2.8 Nm (25 lb in). - Screw on interior side of the cowl to 11 Nm (97 lb in). 6. Heater hoses. 7. Coolant recovery reservoir. 8. Roll instrument panel forward. 9. Steering column. 10. Blower motor. 11. Blower motor cover. 12. Hinge pillar trim panels. 13. Center floor air distribution duct. 14. Electrical connectors, as necessary. 15. Instrument panel storage compartment. 16. Engine coolant. - Check the system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Heater Core > Component Information > Service and Repair > With Air Conditioning > Page 3041 Heater Core: Service and Repair Without Air Conditioning HEATER CORE Remove or Disconnect 1. Engine coolant. 2. Instrument panel storage compartment. 3. Electrical connectors, as necessary. 4. Center floor air distribution duct. 5. Hinge pillar trim panels. 6. Blower motor cover. 7. Blower motor. 8. Steering column. 9. Roll instrument panel back. 10. Coolant recovery reservoir. 11. Heater hoses. 12. Screw on interior side of cowl, near the evaporator pipe (if equipped) while holding heater case to the cowl. 13. Four screws on the engine side of the cowl holding the heater case to the cowl. 14. Two nuts on the engine side of the cowl holding the heater case to the cowl. 15. Heater case. - It may be necessary to have an assistant when removing heater case. 16. Heater cover. - Remove seven screws that hold cover to the heater case. 17. Heater core from retainer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Heater Core > Component Information > Service and Repair > With Air Conditioning > Page 3042 Install or Connect 1. Heater core into retainer. - Install seven screws that hold heater cover to heater case. 2. Heater cover. - Make sure heater cover is properly sealed. 3. Heater case. - May be necessary to have an assistant when installing heater case. 4. Nuts. 5. Screws. Tighten Screws on engine side of the cowl to 1.9 Nm (17 lb in). - Nuts to 2.8 Nm (25 lb in). - Screw on interior side of the cowl to 11 Nm (97 lb in). 6. Heater hoses. 7. Coolant recovery reservoir. 8. Roll instrument panel forward. 9. Steering column. 10. Blower motor. 11. Blower motor cover. 12. Hinge pillar trim panels. 13. Center floor air distribution duct. 14. Electrical connectors, as necessary. 15. Instrument panel storage compartment. 16. Engine coolant. - Check the system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Heater Hose > Component Information > Service and Repair > Heater Inlet Hose Heater Hose: Service and Repair Heater Inlet Hose Heater Hose Routing Quick Connect Heater Inlet Connector Tool Required: J 38723 Heater Line Quick Connect Separator Remove or Disconnect 1. Engine coolant. 2. Inlet hose from generator bracket. 3. Inlet hose at fender clip. 4. Inlet hose clamp at heater core. water shut off valve or tee fining. - Loosen the clamp enough to slide the clamp away from the fining on the inlet hose. 5. Inlet hose from heater core. 6. Push inlet hose into connector and insert J 38723 or equivalent into connector to release locking tabs. 7. Pull retainer and hose from heater inlet connector. Inspect - O-ring sealing surface on hose/pipe. Adjust - If replacing heater inlet connector, remove retainer from hose and discard, as new connector is equipped with retainer. - If replacing hose, remove retainer from hose and reinsert in connector. - If reusing hose and connector, retainer can remain in place on hose. Install or Connect 1. Push hose into connector until retainer tabs lock. - Pull back on hose to check for proper engagement. 2. Inlet hose to heater core, water shut off valve or tee fitting. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Heater Hose > Component Information > Service and Repair > Heater Inlet Hose > Page 3047 3. Inlet hose clamp. 4. Inlet hose mounting screw. Tighten Screw to 30 Nm (22 lb ft). 5. Inlet hose to fender clip. 6. Engine coolant. - Check the system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Heater Hose > Component Information > Service and Repair > Heater Inlet Hose > Page 3048 Heater Hose: Service and Repair Heater Outlet Hose Heater Hose Routing Quick Connect Heater Inlet Connector Remove or Disconnect 1. Engine coolant. 2. Outlet hose from fender clip. 3. Outlet hose clamp from heater core, water shut off valve or tee fitting. 4. Outlet hose from heater core. 5. Outlet hose mounting screw. 6. Outlet hose from generator bracket. 7. Outlet hose clamp from water pump. 8. Outlet hose from water pump. Install or Connect 1. Outlet hose to water pump. 2. Outlet hose clamp to water pump. 3. Outlet hose to generator bracket. 4. Generator bracket mounting screw. Tighten screw to 30 Nm (22 lb ft). 5. Outlet hose to heater core. 6. Outlet hose clamp to heater core. 7. Outlet hose to fender clip. 8. Engine coolant. - Check the system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Lamps and Indicators - Cooling System > Coolant Level Indicator Lamp > Component Information > Diagrams Low Coolant Level Indicator Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Lamps and Indicators - Cooling System > Coolant Level Indicator Lamp > Component Information > Diagrams > Page 3053 Coolant Level Indicator Lamp: Description and Operation This system uses a sensor mounted on the radiator and an indicator light mounted in the instrument panel to warn the driver if coolant level is too low. This light is wired in series with the ignition switch, ECM and the sensor. When the ignition switch is turned to the crank position, the circuit is energized and the indicator light will illuminate. When the ignition switch is turned to the ON position and coolant level is sufficient, the sensor will indicate this to the ECM and the light will turn off. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Lamps and Indicators - Cooling System > Coolant Level Indicator Lamp > Component Information > Testing and Inspection > Indicator Lamp Remains Illuminated Coolant Level Indicator Lamp: Testing and Inspection Indicator Lamp Remains Illuminated 1. Turn ignition switch to the On position, then check coolant level and add coolant as necessary. If lamp remains illuminated, proceed to step 2. 2. Disconnect electrical connector at the sensor. If lamp does not illuminate replace the sensor. If lamp remains illuminated, proceed to step 3. 3. Connect electrical lead to the sensor and check for an open circuit between the sensor and the module. Repair or replace as necessary. If circuit is satisfactory, replace the ECM. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Lamps and Indicators - Cooling System > Coolant Level Indicator Lamp > Component Information > Testing and Inspection > Indicator Lamp Remains Illuminated > Page 3056 Coolant Level Indicator Lamp: Testing and Inspection Indicator Lamp Will Not Illuminate 1. Turn ignition switch to the crank position, and proceed as follows: a. If lamp illuminates, lamp is satisfactory and connector is properly installed. Proceed to step 2. b. If lamp does not illuminate, check bulb, socket and wiring between socket and module connector. Replace or repair as necessary. 2. Turn ignition switch to the On position and disconnect electrical lead at coolant level sensor mounted on the radiator. If lamp fails to illuminate, check wiring between coolant level sensor connector and ECM for a short circuit to ground. If circuit is satisfactory, replace the ECM. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Lamps and Indicators - Cooling System > Temperature Gauge > Component Information > Technical Service Bulletins > Customer Interest: > 676201 > Apr > 96 > Engine - Extreme Temperature Gauge Fluctuation Temperature Gauge: Customer Interest Engine - Extreme Temperature Gauge Fluctuation File In Section: 6 - Engine Bulletin No.: 67-62-01 Date: April, 1996 Subject: Extreme Engine Temperature Gauge Fluctuation (Install a New Thermostat) Models: 1996 Chevrolet and GMC C/K, G Models with 4.3L, 5.0L, 5.7L Engines (VINs M, R, X, W RPOs L30, L31, LF6, L35) Condition Some owners may experience extreme engine temperature gauge fluctuation. Cause Thermostat was not optimally positioned to sense true engine coolant temperature. Correction Install a new thermostat which increases coolant flow past the thermostat temperature sensing element. Parts Information Refer to the following part number when replacing the thermostat: Part Number Description 12557859 Thermostat Parts are expected to be available on April 8, 1996 from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J3500 Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Lamps and Indicators - Cooling System > Temperature Gauge > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 676201 > Apr > 96 > Engine - Extreme Temperature Gauge Fluctuation Temperature Gauge: All Technical Service Bulletins Engine - Extreme Temperature Gauge Fluctuation File In Section: 6 - Engine Bulletin No.: 67-62-01 Date: April, 1996 Subject: Extreme Engine Temperature Gauge Fluctuation (Install a New Thermostat) Models: 1996 Chevrolet and GMC C/K, G Models with 4.3L, 5.0L, 5.7L Engines (VINs M, R, X, W RPOs L30, L31, LF6, L35) Condition Some owners may experience extreme engine temperature gauge fluctuation. Cause Thermostat was not optimally positioned to sense true engine coolant temperature. Correction Install a new thermostat which increases coolant flow past the thermostat temperature sensing element. Parts Information Refer to the following part number when replacing the thermostat: Part Number Description 12557859 Thermostat Parts are expected to be available on April 8, 1996 from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J3500 Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Lamps and Indicators - Cooling System > Temperature Gauge > Component Information > Technical Service Bulletins > All Other Service Bulletins for Temperature Gauge: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder Control Module: All Technical Service Bulletins A/T - Upshift Flare/No 3rd or 4th/Launch Shudder File In Section: 07 - Transmission/Transaxle Bulletin No.: 00-07-30-026 Date: December 2000 TECHNICAL Subject: Automatic Transmission 1-2 and/or 2-3 Upshift Slip/Flare, No 3rd or 4th gear, Launch Shudder (Revise VCM Wiring) Models: 1996 Chevrolet and GMC C/K, S/T, M/L, G1, G2, P3 Models 1996 Oldsmobile Bravada with VCM and 4L60-E (M30) or 4L80-E (MT1) Automatic Transmission This bulletin is being reissued to ensure that correct procedures are followed for this condition. Please discard Corporate Bulletin Number 66-71-03A (Section 7 - Automatic Transmission). When performing a transmission replacement labor operation K7000 on these vehicles with a 4L60-E or 4L80-E, you must include front chassis wire repair labor operation N6112. Inspect the VCM to verify the latest part number revision (16244210). Condition Some owners may comment that the automatic transmission has either a slip or flare on the 1-2 and/or 2-3 upshift, or no 3rd or 4th gear, or launch shudder. Upon investigation, the technician may find a DTC P1870 stored in the VCM. Cause A poor internal ground between the two circuit boards of the VCM may cause the VCM to command erratic line pressure at the pressure control (PC) solenoid valve. Correction Using harness jumper wire and instruction kit, P/N 12167310, revise the wiring harness at the VCM connector. Corrections were made to the VCM beginning 2/14/96. The corrected VCMs are identified with service number 16244210 on the VCM identification label. Procedure The following is a summary of the instructions included with the service kit: 1. Remove the negative terminal from the battery. 2. Move the wire located at connector J3 (WHITE/GREY/CLEAR), pin 18 to connector J1 (BLUE), pin 23. 3. Install the jumper wire between connector J2 (RED), pin 26 and connector J3 (WHITE/GREY/CLEAR), pin 18. 4. Install the tag included in the kit around the. VCM wiring harness. This tag notes that the wiring harness has been modified. 5. Reconnect the negative battery terminal. Road test to verify that the condition has been corrected. If any of the following conditions are noted, the transmission should be repaired or replaced using the most cost effective method. Canadian dealers should repair the transmission. ^ Transmission fluid oxidation or excessive sediment. ^ Transmission slip or flare after this service fix is performed. ^ DTC P1870 is stored on a 4L60-E (M30). The following tools are available from Kent-Moore (1-800-345-2233) for use in removing and relocating the VCM wires: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Lamps and Indicators - Cooling System > Temperature Gauge > Component Information > Technical Service Bulletins > All Other Service Bulletins for Temperature Gauge: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder > Page 3075 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Lamps and Indicators - Cooling System > Temperature Gauge > Component Information > Technical Service Bulletins > All Other Service Bulletins for Temperature Gauge: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder > Page 3081 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Lamps and Indicators - Cooling System > Temperature Gauge > Component Information > Testing and Inspection > Gauge Does Not Move From Cold When Engine Is Hot Temperature Gauge: Testing and Inspection Gauge Does Not Move From Cold When Engine Is Hot This condition is generally caused by a blown fuse, open circuit or faulty sensor. 1. Check fuse, replace if necessary. 2. Turn ignition switch to On position, then remove lead at sensor unit. 3. Connect test lamp from sensor lead to ground, lamp should glow. Short sensor lead to ground, gauge should indicate "Hot." 4. If gauge indicated HOT, check lead on sensor. If satisfactory, replace sensor. If gauge indicates COLD, replace cluster. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Lamps and Indicators - Cooling System > Temperature Gauge > Component Information > Testing and Inspection > Gauge Does Not Move From Cold When Engine Is Hot > Page 3084 Temperature Gauge: Testing and Inspection Gauge Indicates Hot When Engine Is Cold This condition is generally caused by a shorted or grounded circuit. 1. Remove sensor lead at sensor unit. Gauge should move to COLD position, if not check unit for a external short. If no external short is found, replace sensor. 2. If gauge stays HOT, check for a short circuit in gauge to sensor wiring. If circuit is satisfactory, replace cluster. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Lamps and Indicators - Cooling System > Temperature Gauge > Component Information > Testing and Inspection > Gauge Does Not Move From Cold When Engine Is Hot > Page 3085 Temperature Gauge: Testing and Inspection Gauge Reads High 1. Remove lead at sensor, measure resistance using an ohmmeter. 2. At 104 degrees F resistance should be approximately 1200-1350 ohms, and at 125 degrees F resistance should be approximately 53-55 ohms. 3. If resistance is not within specifications, replace sensor. 4. Disconnect lead at sensor and gauge, check for a high resistance using an ohmmeter. Repair wiring if necessary. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Lamps and Indicators - Cooling System > Temperature Gauge > Component Information > Testing and Inspection > Gauge Does Not Move From Cold When Engine Is Hot > Page 3086 Temperature Gauge: Testing and Inspection Gauge Reads Low 1. Ensure terminals are clean and connections are tight. 2. Remove lead at sensor, measure resistance using an ohmmeter. 3. At 104 degrees F resistance should be approximately 1200-1350 ohms, and at 125 degrees F resistance should be approximately 53-55 ohms. 4. If resistance is not within specifications, replace sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Lamps and Indicators - Cooling System > Temperature Warning Lamp/Indicator, Engine Cooling > Component Information > Description and Operation Temperature Warning Lamp/Indicator: Description and Operation A bi-metal temperature switch located in the cylinder head controls the operation of a temperature indicator light. If the engine cooling system is not functioning properly and/or coolant temperature exceeds a predetermined value, the warning light will illuminate. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Lamps and Indicators - Cooling System > Temperature Warning Lamp/Indicator, Engine Cooling > Component Information > Description and Operation > Page 3090 Temperature Warning Lamp/Indicator: Testing and Inspection If the light is not lit when the engine is being cranked, check for a burned out bulb, an open in the light circuit, or a defective ignition switch. If the light is lit when the engine is running, check the wiring between light and switch for a ground, defective temperature switch, or overheated cooling system. As a test circuit to check whether the bulb is functioning properly, connect a wire from the ground terminal of the ignition switch to the temperature indicator light circuit. When the ignition is in the START (engine cranking) position, the ground terminal is grounded inside the switch and the bulb will be lit. When the engine is started and the ignition switch is in the ON position, the test circuit is opened and the bulb is then controlled by the temperature switch. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator > Component Information > Technical Service Bulletins > Cooling System, A/C - Aluminum Heater Cores/Radiators Radiator: Technical Service Bulletins Cooling System, A/C - Aluminum Heater Cores/Radiators INFORMATION Bulletin No.: 05-06-02-001A Date: July 16, 2008 Subject: Information On Aluminum Heater Core and/or Radiator Replacement Models: 2005 and Prior GM Passenger Cars and Light Duty Trucks (including Saturn) 2003-2005 HUMMER H2 Supercede: This bulletin is being revised to update the Warranty Information. Please discard Corporate Bulletin Number 05-06-02-001 (Section 06 - Engine/Propulsion System). Important: 2004-05 Chevrolet Aveo (Pontiac Wave, Canada Only) does not use DEX-COOL(R). Refer to the flushing procedure explained later in this bulletin. The following information should be utilized when servicing aluminum heater core and/or radiators on repeat visits. A replacement may be necessary because erosion, corrosion, or insufficient inhibitor levels may cause damage to the heater core, radiator or water pump. A coolant check should be performed whenever a heater core, radiator, or water pump is replaced. The following procedures/ inspections should be done to verify proper coolant effectiveness. Caution: To avoid being burned, do not remove the radiator cap or surge tank cap while the engine is hot. The cooling system will release scalding fluid and steam under pressure if the radiator cap or surge tank cap is removed while the engine and radiator are still hot. Important: If the vehicle's coolant is low, drained out, or the customer has repeatedly added coolant or water to the system, then the system should be completely flushed using the procedure explained later in this bulletin. Technician Diagnosis ^ Verify coolant concentration. A 50% coolant/water solution ensures proper freeze and corrosion protection. Inhibitor levels cannot be easily measured in the field, but can be indirectly done by the measurement of coolant concentration. This must be done by using a Refractometer J 23688 (Fahrenheit scale) or J 26568 (centigrade scale), or equivalent, coolant tester. The Refractometer uses a minimal amount of coolant that can be taken from the coolant recovery reservoir, radiator or the engine block. Inexpensive gravity float testers (floating balls) will not completely analyze the coolant concentration fully and should not be used. The concentration levels should be between 50% and 65% coolant concentrate. This mixture will have a freeze point protection of -34 degrees Fahrenheit (-37 degrees Celsius). If the concentration is below 50%, the cooling system must be flushed. ^ Inspect the coolant flow restrictor if the vehicle is equipped with one. Refer to Service Information (SI) and/or the appropriate Service Manual for component location and condition for operation. ^ Verify that no electrolysis is present in the cooling system. This electrolysis test can be performed before or after the system has been repaired. Use a digital voltmeter set to 12 volts. Attach one test lead to the negative battery post and insert the other test lead into the radiator coolant, making sure the lead does not touch the filler neck or core. Any voltage reading over 0.3 volts indicates that stray current is finding its way into the coolant. Electrolysis is often an intermittent condition that occurs when a device or accessory that is mounted to the radiator is energized. This type of current could be caused from a poorly grounded cooling fan or some other accessory and can be verified by watching the volt meter and turning on and off various accessories or engage the starter motor. Before using one of the following flush procedures, the coolant recovery reservoir must be removed, drained, cleaned and reinstalled before refilling the system. Notice: ^ Using coolant other than DEX‐COOL(R) may cause premature engine, heater core or radiator corrosion. In addition, the engine coolant may require changing sooner, at 30,000 miles (50,000 km) or 24 months, whichever occurs first. Any repairs would not be covered by your warranty. Always use DEX‐COOL(R) (silicate free) coolant in your vehicle. ^ If you use an improper coolant mixture, your engine could overheat and be badly damaged. The repair cost would not be covered by your warranty. Too much water in the mixture can freeze and crack the engine, radiator, heater core and other parts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator > Component Information > Technical Service Bulletins > Cooling System, A/C - Aluminum Heater Cores/Radiators > Page 3095 Flushing Procedures using DEX-COOL(R) Important: The following procedure recommends refilling the system with DEX-COOL(R), P/N 12346290 (in Canada, use P/N 10953464), GM specification 6277M. This coolant is orange in color and has a service interval of 5 years or 240,000 km (150,000 mi). However, when used on vehicles built prior to the introduction of DEX-COOL(R), maintenance intervals will remain the same as specified in the Owner's Manual. ^ If available, use the approved cooling system flush and fill machine (available through the GM Dealer Equipment Program) following the manufacturer's operating instructions. ^ If approved cooling system flush and fill machine is not available, drain the coolant and dispose of properly following the draining procedures in the appropriate Service Manual. Refill the system using clear, drinkable water and run the vehicle until the thermostat opens. Repeat and run the vehicle three (3) times to totally remove the old coolant or until the drained coolant is almost clear. Once the system is completely flushed, refill the cooling system to a 50%-60% concentration with DEX‐COOL(R), P/N 12346290 (in Canada, use P/N 10953464), GM specification 6277M, following the refill procedures in the appropriate Service Manual. If a Service Manual is not available, fill half the capacity of the system with 100% DEX-COOL(R), P/N 12346290 (in Canada, use P/N 10953464), GM specification 6277M. Then slowly add clear, drinkable water (preferably distilled) to the system until the level of the coolant mixture has reached the base of the radiator neck. Wait two (2) minutes and reverify the coolant level. If necessary, add clean water to restore the coolant to the appropriate level. Once the system is refilled, reverify the coolant concentration using a Refractometer J 23688 (Fahrenheit scale) or J 26568 (centigrade scale) coolant tester, or equivalent. The concentration levels should be between 50% and 65%. Flushing Procedures using Conventional Silicated (Green Colored) Coolant Important: 2004-2005 Chevrolet Aveo (Pontiac Wave, Canada Only) does not use DEX‐COOL(R). The Aveo and Wave are filled with conventional, silicated engine coolant that is blue in color. Silicated coolants are typically green in color and are required to be drained, flushed and refilled every 30,000 miles (48,000 km). The Aveo and Wave are to be serviced with conventional, silicated coolant. Use P/N 12378560 (1 gal) (in Canada, use P/N 88862159 (1 L). Refer to the Owner's Manual or Service Information (SI) for further information on OEM coolant. Important: Do not mix the OEM orange colored DEX-COOL(R) coolant with green colored coolant when adding coolant to the system or when servicing the vehicle's cooling system. Mixing the orange and green colored coolants will produce a brown coolant which may be a customer dissatisfier and will not extend the service interval to that of DEX-COOL(R). Conventional silicated coolants offered by GM Service and Parts Operations are green in color. ^ If available, use the approved cooling system flush and fill machine (available through the GM Dealer Equipment Program) following the manufacturer's operating instructions. ^ If approved cooling systems flush and fill machine is not available, drain coolant and dispose of properly following the draining procedures in appropriate Service Manual. Refill the system using clear, drinkable water and run vehicle until thermostat opens. Repeat and run vehicle three (3) times to totally remove old coolant or until drained coolant is almost clear. Once the system is completely flushed, refill the cooling system to a 50%-60% concentration with a good quality ethylene glycol base engine coolant, P/N 12378560, 1 gal (in Canada, use P/N 88862159 1 L), conforming to GM specification 1825M, or recycled coolant conforming to GM specification 1825M, following the refill procedures in the appropriate Service Manual. If a Service Manual is not available, fill half the capacity of the system with 100% good quality ethylene glycol base (green colored) engine coolant, P/N 12378560 1 gal., (in Canada, use P/N 88862159 1 L) conforming to GM specification 1825M. Then slowly add clear, drinkable water (preferably distilled) to system until the level of the coolant mixture has reached the base of the radiator neck. Wait two (2) minutes and recheck coolant level. If necessary, add clean water to restore coolant to the appropriate level. Once the system is refilled, recheck the coolant concentration using a Refractometer J 23688 (Fahrenheit scale) or J 26568 (centigrade scale) coolant tester, or equivalent. Concentration levels should be between 50% and 65%. Parts Information Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator > Component Information > Technical Service Bulletins > Cooling System, A/C - Aluminum Heater Cores/Radiators > Page 3096 For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator > Component Information > Technical Service Bulletins > Cooling System, A/C - Aluminum Heater Cores/Radiators > Page 3097 Radiator: Technical Service Bulletins Cooling - Radiator Repair/Replacement Guidelines File In Section: 06 - Engine/Propulsion System Bulletin No.: 99-06-02-017 Date: October, 1999 INFORMATION Subject: Radiator Repair/Replacement Guidelines Models: 2000 and Prior Passenger Cars and Trucks If repair of an aluminum/plastic radiator is required, it is recommended that the following guidelines be followed: For Vehicles Under Warranty For aluminum/plastic radiators that have damage to the face of the core including bent fins, punctures, cuts, leaking tubes or header tubes, the aluminum radiator core section should be replaced with a new one. In these cases, if both of the plastic tanks are not damaged, they can be reused with the new core. If one or both of the plastic tanks are damaged along with the core, it is recommended that a complete new radiator assembly be installed. Warranty repairs for leaks at the tank to header (gasket leaks), broken/cracked plastic tanks, cross threaded or leaking oil coolers should be repaired without replacing the complete radiator. This type of repair should be handled by the radiator repair facility in your area. Many of these radiator repair facilities are members of the National Automotive Radiator Service Association (NARSA) who follow industry and General Motors guidelines when repairing radiators. These facilities have the special tools, tanks and pressurizing equipment needed to properly test the repaired radiator prior to returning it to the dealership. Many of these facilities receive the repair components directly from General Motors. The sublet expense for a new radiator or the repair of the radiator under warranty should be handled following normal procedures. For Vehicles No Longer Under Warranty The GM released epoxy repair kit referenced in previous publications is no longer available. Repairs to the radiator, rather than replacement, is strictly at the owner's discretion. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator > Component Information > Technical Service Bulletins > Page 3098 Radiator: Service and Repair 1. Drain coolant from radiator. 2. Remove upper fan shroud bolts and upper fan shroud. 3. Remove upper insulators and brackets. 4. Remove upper and lower radiator hoses. 5. Disconnect transmission fluid cooler lines. 6. Disconnect engine oil cooler lines. 7. Remove lower fan shroud retaining bolts and lower fan shroud. 8. Disconnect overflow hose. 9. Remove radiator from lower insulators and brackets. 10. Reverse procedure to install, noting the following: a. Torque fan shroud attaching bolts to 6 ft. lbs. b. Torque engine oil cooler line fittings to 18 ft. lbs. c. Torque transmission fluid cooler lines to 19 ft. lbs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Radiator Cap > Component Information > Specifications Radiator Cap: Specifications Radiator Cap Relief Pressure, Lbs. ..................................................................................................... ............................................................................... 15 Thermo. Opening Temp., deg.F ..................... .............................................................................................................................................................. .... 195 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Relays and Modules - Cooling System > Radiator Cooling Fan Motor Relay > Component Information > Locations Underhood Fuse-Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > A/C Pressure Sensor/Switch - Cooling Fan > Component Information > Locations A/C Pressure Sensor/Switch - Cooling Fan: Locations Front of Engine Compartment, on Condenser Manifold Tubing Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Specifications Coolant Temperature Sensor/Switch (For Computer): Specifications Engine Coolant Temperature (ECT) sensor .............................................................................................................................................. 13 Nm (10 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Specifications > Page 3114 Engine Side, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions Coolant Temperature Sensor/Switch (For Computer): Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3117 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3118 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3119 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3120 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3121 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3122 Coolant Temperature Sensor/Switch (For Computer): Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3123 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3124 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3125 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3126 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3127 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3128 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3129 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3130 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3131 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3132 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3133 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3134 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3135 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3136 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3137 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3138 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3139 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3140 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3141 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3142 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3143 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3144 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3145 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3146 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3147 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3148 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3149 ECT Sensor Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 3150 Coolant Temperature Sensor/Switch (For Computer): Description and Operation Engine Coolant Temperature (ECT) Sensor DESCRIPTION The engine coolant temperature sensor is a thermistor (a resistor which changes value based on temperature) mounted in the engine coolant passage. Low coolant temperature produces a high resistance 100,000 ohms at -40°C (-40°F) while high temperature causes low resistance 70 ohms at 130°C (266°F). OPERATION The VCM supplies a 5 volt signal to the engine coolant temperature sensor through a resistor in the VCM and measures the voltage. The voltage will be high when the engine is cold. The voltage will be low when the engine is hot. By measuring the voltage, the VCM calculates the engine coolant temperature. Engine coolant temperature affects most systems the VCM controls. The scan tool displays engine coolant temperature in degrees. After engine start-up, the temperature should rise steadily to about 9O°C (194°F) then stabilize when thermostat opens. If the engine has not been run for several hours (overnight), the engine coolant temperature and intake air temperature displays should be close to each other. When the VCM detects a malfunction in the Engine Coolant Temperature (ECT) sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0117 circuit low. ^ DTC P0118 circuit high. ^ DTC P0125 excessive time to Closed Loop. ^ DTC P1114 circuit intermittent low. ^ DTC P1115 circuit intermittent high. The above DTCs contain a table to check for sensor resistance values relative to temperature. Refer to Specifications. See: Powertrain Management/Computers and Control Systems/Specifications Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 3151 Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection The scan tool displays engine coolant temperature in degrees. After engine start-up, the temperature should rise steadily to about 90°C (194°F) then stabilize when thermostat opens. If the engine has not been run for several hours (overnight), the engine coolant temperature and intake air temperature displays should be close to each other. When the VCM detects a malfunction in the Engine Coolant Temperature (ECT) sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0117 circuit low. ^ DTC P0118 circuit high. ^ DTC P0125 excessive time to Closed Loop. ^ DTC P1114 circuit intermittent low. ^ DTC P1115 circuit intermittent high. The above DTCs contain a table to check for sensor resistance values relative to temperature. Refer to Diagnostic Tables. See: Powertrain Management/Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 3152 Coolant Temperature Sensor/Switch (For Computer): Service and Repair Engine Coolant Temperature (ECT) Sensor Electrical Connector Engine Coolant Temperature (ECT) Sensor CAUTION: Use care when handling the coolant sensor. Damage to the coolant sensor will affect the operation of the fuel control system. REMOVAL PROCEDURE 1. Relieve the coolant pressure. 2. Disconnect the negative battery cable. 3. Drain the cooling system below the level of the sensor. 4. Disconnect the electrical connector releasing locking tab. 5. Remove the coolant sensor from engine. INSTALLATION PROCEDURE 1. Coat the threads (only) with sealer P/N 9985253 or equivalent. Tighten ^ Tighten the sensor to 13 N.m (10 lb. ft.). 2. Install the coolant sensor in the engine. 3. Connect the electrical connector. 4. Refill the cooling system. 5. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Temperature Sensor (Gauge) > Component Information > Locations Temperature Sensor (Gauge): Locations Engine Side, LH LH cylinder head, near number one spark plug. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Temperature Gauge > Component Information > Technical Service Bulletins > Customer Interest: > 676201 > Apr > 96 > Engine - Extreme Temperature Gauge Fluctuation Temperature Gauge: Customer Interest Engine - Extreme Temperature Gauge Fluctuation File In Section: 6 - Engine Bulletin No.: 67-62-01 Date: April, 1996 Subject: Extreme Engine Temperature Gauge Fluctuation (Install a New Thermostat) Models: 1996 Chevrolet and GMC C/K, G Models with 4.3L, 5.0L, 5.7L Engines (VINs M, R, X, W RPOs L30, L31, LF6, L35) Condition Some owners may experience extreme engine temperature gauge fluctuation. Cause Thermostat was not optimally positioned to sense true engine coolant temperature. Correction Install a new thermostat which increases coolant flow past the thermostat temperature sensing element. Parts Information Refer to the following part number when replacing the thermostat: Part Number Description 12557859 Thermostat Parts are expected to be available on April 8, 1996 from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J3500 Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Temperature Gauge > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 676201 > Apr > 96 > Engine - Extreme Temperature Gauge Fluctuation Temperature Gauge: All Technical Service Bulletins Engine - Extreme Temperature Gauge Fluctuation File In Section: 6 - Engine Bulletin No.: 67-62-01 Date: April, 1996 Subject: Extreme Engine Temperature Gauge Fluctuation (Install a New Thermostat) Models: 1996 Chevrolet and GMC C/K, G Models with 4.3L, 5.0L, 5.7L Engines (VINs M, R, X, W RPOs L30, L31, LF6, L35) Condition Some owners may experience extreme engine temperature gauge fluctuation. Cause Thermostat was not optimally positioned to sense true engine coolant temperature. Correction Install a new thermostat which increases coolant flow past the thermostat temperature sensing element. Parts Information Refer to the following part number when replacing the thermostat: Part Number Description 12557859 Thermostat Parts are expected to be available on April 8, 1996 from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J3500 Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Temperature Gauge > Component Information > Technical Service Bulletins > All Other Service Bulletins for Temperature Gauge: > 01-03-10-009A > Jul > 04 > Wheels - Plastic Wheel Nut Covers Loose/Missing Wheel Fastener: All Technical Service Bulletins Wheels - Plastic Wheel Nut Covers Loose/Missing Bulletin No.: 01-03-10-009A Date: July 27, 2004 TECHNICAL Subject: Plastic Wheel Nut Covers Missing and/or Loose (Replace Missing Covers and Add Sealant to All Covers) Models: 2005 and All Prior Passenger Cars (Except All Cadillac Models and Pontiac GTO) with Plastic Wheel Nut Covers Supercede: This bulletin is being revised to add additional models years. Please discard Corporate Bulletin Number 01-03-10-009. Condition Some customers may comment that the plastic wheel nut covers are missing and/or loose. Correction Important: ^ DO NOT USE a silicone-based adhesive. ^ Do not apply the *permatex(R) around the threads in a circular pattern. ^ Apply a single bead across the threads approximately 10 mm (0.4 in) in length, 5 mm (0.2 in) in height and 5 mm (0.2 in) in width. Replace any missing plastic wheel nut covers with the appropriate covers and apply Permatex(R) # 2 Form A Gasket Sealant(R) to the threads of all the plastic wheel nut covers. Tighten finger tight plus a 1/4 turn with a hand wrench. *We believe this source and their products to be reliable. There may be additional manufacturers of such material. General Motors does not endorse, indicate any preference for or assume any responsibility for the products from this firm or for any other such items which may be available from other sources. Permatex(R) # 2 Form A Gasket Sealant(R) part numbers (available at your local parts supplier) ^ P/N 80009 (2A/2AR) - 44 ml (1.5 oz) tube boxed ^ P/N 80015 (2AR) - 44 ml (1.5 oz) tube carded ^ P/N 80010 (2B/2BR) - 89 ml (3 oz) tube boxed ^ P/N 80016 (2BR) - 89 ml (3 oz) tube carded ^ P/N 80011 (2C) - 325 ml (11 oz) tube boxed Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Temperature Gauge > Component Information > Technical Service Bulletins > All Other Service Bulletins for Temperature Gauge: > 01-03-10-009A > Jul > 04 > Wheels - Plastic Wheel Nut Covers Loose/Missing > Page 3174 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Temperature Gauge > Component Information > Technical Service Bulletins > All Other Service Bulletins for Temperature Gauge: > 01-03-10-009A > Jul > 04 > Wheels - Plastic Wheel Nut Covers Loose/Missing > Page 3180 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Temperature Gauge > Component Information > Testing and Inspection > Gauge Does Not Move From Cold When Engine Is Hot Temperature Gauge: Testing and Inspection Gauge Does Not Move From Cold When Engine Is Hot This condition is generally caused by a blown fuse, open circuit or faulty sensor. 1. Check fuse, replace if necessary. 2. Turn ignition switch to On position, then remove lead at sensor unit. 3. Connect test lamp from sensor lead to ground, lamp should glow. Short sensor lead to ground, gauge should indicate "Hot." 4. If gauge indicated HOT, check lead on sensor. If satisfactory, replace sensor. If gauge indicates COLD, replace cluster. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Temperature Gauge > Component Information > Testing and Inspection > Gauge Does Not Move From Cold When Engine Is Hot > Page 3183 Temperature Gauge: Testing and Inspection Gauge Indicates Hot When Engine Is Cold This condition is generally caused by a shorted or grounded circuit. 1. Remove sensor lead at sensor unit. Gauge should move to COLD position, if not check unit for a external short. If no external short is found, replace sensor. 2. If gauge stays HOT, check for a short circuit in gauge to sensor wiring. If circuit is satisfactory, replace cluster. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Temperature Gauge > Component Information > Testing and Inspection > Gauge Does Not Move From Cold When Engine Is Hot > Page 3184 Temperature Gauge: Testing and Inspection Gauge Reads High 1. Remove lead at sensor, measure resistance using an ohmmeter. 2. At 104 degrees F resistance should be approximately 1200-1350 ohms, and at 125 degrees F resistance should be approximately 53-55 ohms. 3. If resistance is not within specifications, replace sensor. 4. Disconnect lead at sensor and gauge, check for a high resistance using an ohmmeter. Repair wiring if necessary. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Temperature Gauge > Component Information > Testing and Inspection > Gauge Does Not Move From Cold When Engine Is Hot > Page 3185 Temperature Gauge: Testing and Inspection Gauge Reads Low 1. Ensure terminals are clean and connections are tight. 2. Remove lead at sensor, measure resistance using an ohmmeter. 3. At 104 degrees F resistance should be approximately 1200-1350 ohms, and at 125 degrees F resistance should be approximately 53-55 ohms. 4. If resistance is not within specifications, replace sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Temperature Warning Lamp/Indicator, Engine Cooling > Component Information > Description and Operation Temperature Warning Lamp/Indicator: Description and Operation A bi-metal temperature switch located in the cylinder head controls the operation of a temperature indicator light. If the engine cooling system is not functioning properly and/or coolant temperature exceeds a predetermined value, the warning light will illuminate. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Temperature Warning Lamp/Indicator, Engine Cooling > Component Information > Description and Operation > Page 3189 Temperature Warning Lamp/Indicator: Testing and Inspection If the light is not lit when the engine is being cranked, check for a burned out bulb, an open in the light circuit, or a defective ignition switch. If the light is lit when the engine is running, check the wiring between light and switch for a ground, defective temperature switch, or overheated cooling system. As a test circuit to check whether the bulb is functioning properly, connect a wire from the ground terminal of the ignition switch to the temperature indicator light circuit. When the ignition is in the START (engine cranking) position, the ground terminal is grounded inside the switch and the bulb will be lit. When the engine is started and the ignition switch is in the ON position, the test circuit is opened and the bulb is then controlled by the temperature switch. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Thermostat, Engine Cooling > Component Information > Technical Service Bulletins > Customer Interest for Thermostat: > 676201 > Apr > 96 > Engine Extreme Temperature Gauge Fluctuation Thermostat: Customer Interest Engine - Extreme Temperature Gauge Fluctuation File In Section: 6 - Engine Bulletin No.: 67-62-01 Date: April, 1996 Subject: Extreme Engine Temperature Gauge Fluctuation (Install a New Thermostat) Models: 1996 Chevrolet and GMC C/K, G Models with 4.3L, 5.0L, 5.7L Engines (VINs M, R, X, W RPOs L30, L31, LF6, L35) Condition Some owners may experience extreme engine temperature gauge fluctuation. Cause Thermostat was not optimally positioned to sense true engine coolant temperature. Correction Install a new thermostat which increases coolant flow past the thermostat temperature sensing element. Parts Information Refer to the following part number when replacing the thermostat: Part Number Description 12557859 Thermostat Parts are expected to be available on April 8, 1996 from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J3500 Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Thermostat, Engine Cooling > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Thermostat: > 676201 > Apr > 96 > Engine - Extreme Temperature Gauge Fluctuation Thermostat: All Technical Service Bulletins Engine - Extreme Temperature Gauge Fluctuation File In Section: 6 - Engine Bulletin No.: 67-62-01 Date: April, 1996 Subject: Extreme Engine Temperature Gauge Fluctuation (Install a New Thermostat) Models: 1996 Chevrolet and GMC C/K, G Models with 4.3L, 5.0L, 5.7L Engines (VINs M, R, X, W RPOs L30, L31, LF6, L35) Condition Some owners may experience extreme engine temperature gauge fluctuation. Cause Thermostat was not optimally positioned to sense true engine coolant temperature. Correction Install a new thermostat which increases coolant flow past the thermostat temperature sensing element. Parts Information Refer to the following part number when replacing the thermostat: Part Number Description 12557859 Thermostat Parts are expected to be available on April 8, 1996 from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J3500 Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Thermostat, Engine Cooling > Component Information > Technical Service Bulletins > Page 3203 Thermostat: Specifications Radiator Cap Relief Pressure, Lbs. ..................................................................................................... ............................................................................... 15 Thermo. Opening Temp., deg.F ..................... .............................................................................................................................................................. .... 195 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Thermostat, Engine Cooling > Component Information > Technical Service Bulletins > Page 3204 Thermostat: Service and Repair 1. Drain cooling system until radiator coolant level is below thermostat. 2. Remove thermostat housing bolts and/or studs, then the thermostat housing and thermostat. 3. Thoroughly clean gasket surfaces of thermostat housing and intake manifold. 4. Reverse procedure to install, noting the following: a. Torque thermostat housing bolts and/or studs to 21 ft. lbs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Cooling System > Water Pump > Component Information > Service and Repair Water Pump: Service and Repair Water pump replacement. 305/350 1. Disconnect battery ground cable. 2. Drain coolant from radiator. 3. Remove upper fan shroud. 4. Remove drive belt. 5. Remove fan assembly from engine. 6. Lower radiator and heater hose from the water pump. 7. Remove water pump attaching bolts and water pump, Fig. 15. 8. Reverse procedure to install. Tighten water pump attaching bolts to specifications. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Exhaust System > Catalytic Converter > Component Information > Locations > Utility 2 Door Catalytic Converter Location Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Exhaust System > Catalytic Converter > Component Information > Locations > Utility 2 Door > Page 3213 Catalytic Converter Location Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Engine, Cooling and Exhaust > Exhaust System > Exhaust Manifold > Component Information > Service and Repair Exhaust Manifold: Service and Repair 1. Disconnect battery ground cable, then raise and support vehicle. 2. Disconnect exhaust pipe from manifold. 3. Lower vehicle. 4. Disconnect oxygen sensor electrical connector from left side manifold. Do not remove oxygen sensor from the manifold unless it is to be replaced. Remove dipstick tube bracket from right side manifold. 5. Remove power steering pump bracket from left side manifold. 6. Remove heat stove pipe from right side manifold. 7. Disconnect AIR hose from check valve. 8. Remove manifold attaching bolts, washers, heat shield and tab washers. 9. Remove exhaust manifold. 10. Reverse procedure to install, using a new gasket. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > Customer Interest: > 77-71-53 > Apr > 97 > A/T - Chuggle/Surge on TCC Apply/No DTC's Engine Control Module: Customer Interest A/T - Chuggle/Surge on TCC Apply/No DTC's File In Section: 7 - Transmission Bulletin No.: 77-71-53 Date: April, 1997 Subject: Chuggle/Surge on TCC Apply/No DTC's (Reflash PCM) Models: 1996-97 Chevrolet and GMC C/K, G Models with 5.7L Engine (VIN R - RPO L31) and HYDRA-MATIC 4L60-E Transmission (RPO M30) Condition Some owners of the above models may experience a chuggle/surge when TCC is applied under light throttle acceleration. Cause Engine inputs (Combustion events) exciting the vehicle platform/driveline or tire balance may be a contributing factor. Correction First ensure the most recent engine, not transmission calibration has been installed (Corp. # 76-65-04) and check tire balance. A new transmission calibration to correct chuggle/surge is available for use on vehicles with persistent concerns only. Important: This calibration will raise TCC engagement approximately 7-10 mph depending on application. This calibration should not be installed until the engine calibration listed above has been installed. Installation of this calibration may lead to decreased fuel economy due to TCC engagement at higher speeds. Reflash the Powertrain Control Module with the appropriate part numbers below. Refer to your Service Manual for proper procedure. Parts Information This new calibration will be available starting with the 1997 Disc 4 update. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J6355 Reflash Control Module Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 04-06-04-054B > Nov > 10 > Engine Controls - Aftermarket Accessory Usage Engine Control Module: All Technical Service Bulletins Engine Controls - Aftermarket Accessory Usage INFORMATION Bulletin No.: 04-06-04-054B Date: November 18, 2010 Subject: Info - Non-GM Parts and Accessories (Aftermarket) Models: 2011 and Prior GM Passenger Cars and Trucks Supercede: This bulletin is being revised to add model years and update to the new U.S. Fixed Operation Manager (FOM) and Canada Warranty Manager (WM) names. Please discard Corporate Bulletin Number 04-06-04-054A (Section 06 - Engine/Propulsion System). The recent rise and expansion of companies selling non-GM parts and accessories has made it necessary to issue this reminder to dealers regarding GM's policy on the use and installation of these aftermarket components. When a dealer is performing a repair under the New Vehicle Limited Warranty, they are required to use only genuine GM or GM-approved parts and accessories. This applies to all warranty repairs, special policy repairs or any repairs paid for by GM. Parts and accessories advertised as being "the same" as parts manufactured by GM, but not sold through GM, do not qualify for use in warranty repairs, special policy repairs or any repairs paid for by GM. During a warranty repair, if a GM original equipment part is not available through GM Customer Care and Aftersales (GM CC&A;), ACDelco(R) distributors, other GM dealers or approved sources, the dealer is to obtain comparable, non-GM parts and clearly indicate, in detail, on the repair order the circumstances surrounding why non-GM parts were used. The dealer must give customers written notice, prior to the sale or service, that such parts or accessories are not marketed or warranted by General Motors. It should also be noted that dealers modifying new vehicles and installing equipment, parts and accessories obtained from sources not authorized by GM are responsible for complying with the National Traffic and Motor Vehicle Safety Act. Certain non-approved parts or assemblies, installed by the dealer or its agent not authorized by GM, may result in a change to the vehicle's design characteristics and may affect the vehicle's ability to conform to federal law. Dealers must fully understand that non-GM approved parts may not have been validated, tested or certified for use. This puts the dealer at risk for potential liability in the event of a part or vehicle failure. If a GM part failure occurs as the result of the installation or use of a non-GM approved part, the warranty will not be honored. A good example of non-authorized modification of vehicles is the result of an ever increasing supply of aftermarket devices available to the customer, which claim to increase the horsepower and torque of the Duramax(TM) Diesel Engines. These include the addition of, but are not limited to one or more of the following modifications: - Propane injection - Nitrous oxide injection - Additional modules (black boxes) that connect to the vehicle wiring systems - Revised engine calibrations downloaded for the engine control module - Calibration modules which connect to the vehicle diagnostic connector - Modification to the engine turbocharger waste gate Although the installation of these devices, or modification of vehicle components, can increase engine horsepower and torque, they may also negatively affect the engine emissions, reliability and/or durability. In addition, other powertrain components, such as transmissions, universal joints, drive shafts, and front/rear axle components, can be stressed beyond design safety limits by the installation of these devices. General Motors does not support or endorse the use of devices or modifications that, when installed, increase the engine horsepower and torque. It is because of these unknown stresses, and the potential to alter reliability, durability and emissions performance, that GM has adopted a policy that prevents any UNAUTHORIZED dealer warranty claim submissions to any remaining warranty coverage, to the powertrain and driveline components whenever the presence of a non-GM (aftermarket) calibration is confirmed - even if the non-GM control module calibration is subsequently removed. Refer to the latest version of Bulletin 09-06-04-026 (V8 Gas Engines) or 06-06-01-007 (Duramax(TM) Diesel Engines) for more information on dealer requirements for calibration verification. These same policies apply as they relate to the use of non-GM accessories. Damage or failure from the use or installation of a non-GM accessory will not be covered under warranty. Failure resulting from the alteration or modification of the vehicle, including the cutting, welding or disconnecting of the vehicle's original equipment parts and components will void the warranty. Additionally, dealers will NOT be reimbursed or compensated by GM in the event of any legal inquiry at either the local, state or federal level that Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 04-06-04-054B > Nov > 10 > Engine Controls - Aftermarket Accessory Usage > Page 3233 results from the alteration or modification of a vehicle using non-GM approved parts or accessories. Dealers should be especially cautious of accessory companies that claim the installation of their product will not void the factory warranty. Many times these companies have even given direction on how to quickly disassemble the accessory in an attempt to preclude the manufacturer from finding out that is has been installed. Any suspect repairs should be reviewed by the Fixed Operations Manager (FOM), and in Canada by the Warranty Manager (WM) for appropriate repair direction. If it is decided that a goodwill repair is to be made on the vehicle, even with the installation of such non-GM approved components, the customer is to be made aware of General Motors position on this issue and is to sign the appropriate goodwill documentation required by General Motors. It is imperative for dealers to understand that by installing such devices, they are jeopardizing not only the warranty coverage, but also the performance and reliability of the customer's vehicle. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 83-81-32 > Sep > 98 > PCM Connector - Information on New Service Kits Engine Control Module: All Technical Service Bulletins PCM Connector - Information on New Service Kits File In Section: 8 - Chassis/Body Electrical Bulletin No.: 83-81-32 Date: September, 1998 INFORMATION Subject: New Powertrain Control Module (PCM) Connector Service Kits Models: 1996-99 All Passenger Cars except Geo and Catera Two new kits have been released to service the Powertrain Control Module (PCM) connector If the connector has been damaged during servicing. This PCM has an aluminum body and is usually mounted underhood. Kit (P/N 12167308) contains the 80 way connector body, the cover, two each of four different terminal retainers and 25 empty cavity plugs. No terminals are included. If terminals are needed, use P/N 12084913 for 0.35 mm and 0.50 mm wire and P/N 12084912 for 0.80 mm wire. These terminals are included in the terminal repair kit J 38125A or B, and replacements can be ordered from Kent-Moore. kit (P/N 12167313) contains one connector seal. Whenever the connector is unbolted from the aluminum body of the PCM, the seal can stick to the body, or may be twisted. This seal should be replaced whenever the connector is removed in service. Parts Information P/N Description 12167308 Kit, PCM Harness Repair 12167313 Seal Kit, PCM Connector 12084912 Terminal 12084913 Terminal Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 77-71-53 > Apr > 97 > A/T - Chuggle/Surge on TCC Apply/No DTC's Engine Control Module: All Technical Service Bulletins A/T - Chuggle/Surge on TCC Apply/No DTC's File In Section: 7 - Transmission Bulletin No.: 77-71-53 Date: April, 1997 Subject: Chuggle/Surge on TCC Apply/No DTC's (Reflash PCM) Models: 1996-97 Chevrolet and GMC C/K, G Models with 5.7L Engine (VIN R - RPO L31) and HYDRA-MATIC 4L60-E Transmission (RPO M30) Condition Some owners of the above models may experience a chuggle/surge when TCC is applied under light throttle acceleration. Cause Engine inputs (Combustion events) exciting the vehicle platform/driveline or tire balance may be a contributing factor. Correction First ensure the most recent engine, not transmission calibration has been installed (Corp. # 76-65-04) and check tire balance. A new transmission calibration to correct chuggle/surge is available for use on vehicles with persistent concerns only. Important: This calibration will raise TCC engagement approximately 7-10 mph depending on application. This calibration should not be installed until the engine calibration listed above has been installed. Installation of this calibration may lead to decreased fuel economy due to TCC engagement at higher speeds. Reflash the Powertrain Control Module with the appropriate part numbers below. Refer to your Service Manual for proper procedure. Parts Information This new calibration will be available starting with the 1997 Disc 4 update. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J6355 Reflash Control Module Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter Engine Control Module: All Technical Service Bulletins PROM - Reprogram Using Off Board Program Adapter File In Section: 6E - Engine Fuel & Emission Bulletin No.: 73-65-13 Date: March, 1997 INFORMATION Subject: Reprogramming Capability using the Off Board Programming Adapter Models: 1993-97 Passenger Cars and Trucks (Applicable Reprogrammable Vehicles) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 3246 The General Motors vehicles contain Electronically Reprogrammable Devices (i.e. PCM, VCM, ECM). These vehicles cannot be programmed through PROM replacement, however service programming capability is available through the Tech 1/1A, Tech 2 and Techline terminals via direct or remote programming. The Environmental Protection Agency (EPA) has requested that all new vehicle manufacturers ensure their dealers/retailers are aware that they are responsible for providing customers access to reprogramming services at a reasonable cost and in a timely manner. Although programming of controllers has become a common service practice at GM dealers/retailers, the EPA has received reports from consumers and the aftermarket repair industry that they were unable to purchase a new (programmed) Electronically Reprogrammable Device (ERD) over-the-counter. As a result, on August 1, 1995, the Federal Government issued a regulation requiring all manufacturers to make available reprogramming to the independent aftermarket by December 1, 1997. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 3247 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 3248 Today, the Off Board Programming Adapter (OBPA) is used to reprogram ERD's sold over-the-counter. For all practical purposes, the OBPA takes the place of the vehicle when the vehicle is not available. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 3249 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 3250 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 3251 The list of dealerships/retailers currently own the OBPA (see Attachments 1 - 3). These locations are equipped to provide over-the-counter preprogrammed ERD's. The hardware required to perform reprogramming in addition to the OBPA is a Techline terminal, Tech 1/1A and associated cables and adapters. THE TECH 2 SHOULD NOT BE USED WITH THE OBPA AT THIS TIME BECAUSE OF INADEQUATE OBPA GROUNDING. The current OBPA can support reprogramming on all late model General Motor's vehicles except: ^ Premium V-8's ^ 1996 Diesel Truck ^ Cadillac Catera Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 3252 ^ All 1997 programmable vehicles (requires use of the Tech 2) A modification to the OBPA is being offered by Kent-Moore to support these additional vehicles and to allow reprogramming using the Tech 2. The revisions to the OBPA for the Tech 2 is very important as the Tech 2 is the only tool used for service programming for 1997 and future vehicles. To have the modifications performed, contact Kent-Moore at (800) 345-2233. The revisions (part number J 41207 REV-C) are free of charge for GM dealerships/retailers. A dealership/retailer can purchase the OBPA by contacting Kent-Moore (part number J 41207-C). Support on how to use the OBPA is provided by the Techline Customer Support Center (TCSC) at (800) 828-6860 (English) or (800) 503-3222 (French). If you need to purchase an OBPA and/or cable, contact Kent-Moore at (800) 345-2233. The OBPA retails for $695.00 (includes all revisions 1-4) under part number J 41207-C. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules Relay Module: All Technical Service Bulletins Electrical - MIL ON/DTC's Set By Various Control Modules TECHNICAL Bulletin No.: 09-06-03-004D Date: December 08, 2010 Subject: Intermittent No Crank/No Start, No Module Communication, MIL, Warning Lights, Vehicle Messages or DTCs Set by Various Control Modules - Diagnosing and Repairing Fretting Corrosion (Disconnect Affected Connector and Apply Dielectric Lubricant) Models: 2011 and Prior GM Passenger Cars and Trucks Attention: This repair can be applied to ANY electrical connection including, but not limited to: lighting, body electrical, in-line connections, powertrain control sensors, etc. DO NOT over apply lubricant to the point where it prevents the full engagement of sealed connectors. A light coating on the terminal surfaces is sufficient to correct the condition. Supercede: This bulletin is being revised to update the Attention statement and add the 2011 model year. Please discard Corporate Bulletin Number 09-06-03-004C (Section 06 Engine/Propulsion System). Condition Some customers may comment on any of the following conditions: - An intermittent no crank/no start - Intermittent malfunction indicator lamp (MIL) illumination - Intermittent service lamp illumination - Intermittent service message(s) being displayed The technician may determine that he is unable to duplicate the intermittent condition. Cause This condition may be caused by a buildup of nonconductive insulating oxidized debris known as fretting corrosion, occurring between two electrical contact surfaces of the connection or connector. This may be caused by any of the following conditions: - Vibration - Thermal cycling - Poor connection/terminal retention - Micro motion - A connector, component or wiring harness not properly secured resulting in movement On low current signal circuits this condition may cause high resistance, resulting in intermittent connections. On high current power circuits this condition may cause permanent increases in the resistance and may cause a device to become inoperative. Representative List of Control Modules and Components The following is only a representative list of control modules and components that may be affected by this connection or connector condition and DOES NOT include every possible module or component for every vehicle. - Blower Control Module - Body Control Module (BCM) - Communication Interface Module (CIM) - Cooling Fan Control Module - Electronic Brake Control Module (EBCM) - Electronic Brake and Traction Control Module (EBTCM) - Electronic Suspension Control (ESC) Module - Engine Control Module (ECM) - Heating, Ventilation and Air Conditioning (HVAC) Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 3258 - HVAC Actuator - Inflatable Restraint Sensing and Diagnostic Module (SDM) - Any AIR BAG module - Seatbelt Lap Anchor Pretensioner - Seatbelt Retractor Pretensioner - An SIR system connection or connector condition resulting in the following DTCs being set: B0015, B0016, B0019, B0020, B0022, or B0023 - Powertrain Control Module (PCM) - Remote Control Door Lock Receiver (RCDLR) - Transmission Control Module (TCM) Correction Important DO NOT replace the control module, wiring or component for the following conditions: - The condition is intermittent and cannot be duplicated. - The condition is present and by disconnecting and reconnecting the connector the condition can no longer be duplicated. Use the following procedure to correct the conditions listed above. 1. Install a scan tool and perform the Diagnostic System Check - Vehicle. Retrieve and record any existing history or current DTCs from all of the control modules (refer to SI). ‹› If any DTC(s) are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). ‹› If DTCs are not set, refer to Symptoms - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). 2. When identified, use the appropriate DTC Diagnostics, Symptoms, Schematics, Component Connector End Views and Component Locator documents to locate and disconnect the affected harness connector(s) which are causing the condition. Note Fretting corrosion looks like little dark smudges on electrical terminals and appear where the actual electrical contact is being made. In less severe cases it may be unable to be seen or identified without the use of a magnifying glass. Important DO NOT apply an excessive amount of dielectric lubricant to the connectors as shown, as hydrolock may result when attempting to mate the connectors. Use ONLY a clean nylon brush that is dedicated to the repair of the conditions in this bulletin. 3. With a one-inch nylon bristle brush, apply dielectric lubricant to both the module/component side and the harness side of the affected connector(s). 4. Reconnect the affected connector(s) and wipe away any excess lubricant that may be present. 5. Attempt to duplicate the condition by using the following information: - DTC Diagnostic Procedure - Circuit/System Description - Conditions for Running the DTC - Conditions for Setting the DTC - Diagnostic Aids - Circuit/System Verification ‹› If the condition cannot be duplicated, the repair is complete. ‹› If the condition can be duplicated, then follow the appropriate DTC, Symptom or Circuit/System Testing procedure (refer to SI). Repair Order Documentation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 3259 Important The following information MUST be documented on the repair order. Failure to do so may result in a chargeback. - Customer vehicle condition. - Was a Service Lamp or Service Message illuminated? If yes, specify which Service Lamp or Service Message. - Was a DTC(s) set? If yes, specify which DTC(s) were set. - After following the procedure contained within this bulletin, could the condition be duplicated? ‹› If the condition was not duplicated, then document the affected module/component connector name and number on the repair order. - If the condition was duplicated after the procedure contained within this bulletin was followed, and additional diagnosis led to the replacement of a module or component, the SI Document ID Number MUST be written on the repair order. Parts Information Alternate Distributor For All of North America Note NyoGel(R) 760G Lubricant* is equivalent to GMSPO P/N 12377900, and P/N 10953529 (Canada), specified for use to correct the condition in this bulletin. *We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for, or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 3260 For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to refer to the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 3266 - HVAC Actuator - Inflatable Restraint Sensing and Diagnostic Module (SDM) - Any AIR BAG module - Seatbelt Lap Anchor Pretensioner - Seatbelt Retractor Pretensioner - An SIR system connection or connector condition resulting in the following DTCs being set: B0015, B0016, B0019, B0020, B0022, or B0023 - Powertrain Control Module (PCM) - Remote Control Door Lock Receiver (RCDLR) - Transmission Control Module (TCM) Correction Important DO NOT replace the control module, wiring or component for the following conditions: - The condition is intermittent and cannot be duplicated. - The condition is present and by disconnecting and reconnecting the connector the condition can no longer be duplicated. Use the following procedure to correct the conditions listed above. 1. Install a scan tool and perform the Diagnostic System Check - Vehicle. Retrieve and record any existing history or current DTCs from all of the control modules (refer to SI). ‹› If any DTC(s) are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). ‹› If DTCs are not set, refer to Symptoms - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). 2. When identified, use the appropriate DTC Diagnostics, Symptoms, Schematics, Component Connector End Views and Component Locator documents to locate and disconnect the affected harness connector(s) which are causing the condition. Note Fretting corrosion looks like little dark smudges on electrical terminals and appear where the actual electrical contact is being made. In less severe cases it may be unable to be seen or identified without the use of a magnifying glass. Important DO NOT apply an excessive amount of dielectric lubricant to the connectors as shown, as hydrolock may result when attempting to mate the connectors. Use ONLY a clean nylon brush that is dedicated to the repair of the conditions in this bulletin. 3. With a one-inch nylon bristle brush, apply dielectric lubricant to both the module/component side and the harness side of the affected connector(s). 4. Reconnect the affected connector(s) and wipe away any excess lubricant that may be present. 5. Attempt to duplicate the condition by using the following information: - DTC Diagnostic Procedure - Circuit/System Description - Conditions for Running the DTC - Conditions for Setting the DTC - Diagnostic Aids - Circuit/System Verification ‹› If the condition cannot be duplicated, the repair is complete. ‹› If the condition can be duplicated, then follow the appropriate DTC, Symptom or Circuit/System Testing procedure (refer to SI). Repair Order Documentation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 3267 Important The following information MUST be documented on the repair order. Failure to do so may result in a chargeback. - Customer vehicle condition. - Was a Service Lamp or Service Message illuminated? If yes, specify which Service Lamp or Service Message. - Was a DTC(s) set? If yes, specify which DTC(s) were set. - After following the procedure contained within this bulletin, could the condition be duplicated? ‹› If the condition was not duplicated, then document the affected module/component connector name and number on the repair order. - If the condition was duplicated after the procedure contained within this bulletin was followed, and additional diagnosis led to the replacement of a module or component, the SI Document ID Number MUST be written on the repair order. Parts Information Alternate Distributor For All of North America Note NyoGel(R) 760G Lubricant* is equivalent to GMSPO P/N 12377900, and P/N 10953529 (Canada), specified for use to correct the condition in this bulletin. *We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for, or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 3268 For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to refer to the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > Page 3269 Engine Control Module: Locations Underhood Fuse-Relay Center Brake Pressure Modulator Valve Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > Page 3270 Vehicle Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions Engine Control Module: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3273 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3274 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3275 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3276 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3277 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3278 Engine Control Module: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3279 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3280 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3281 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3282 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3283 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3284 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3285 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3286 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3287 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3288 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3289 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3290 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3291 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3292 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3293 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3294 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3295 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3296 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3297 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3298 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3299 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3300 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3301 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3302 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3303 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3304 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3305 Engine Control Module: Connector Views Connector End View Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3306 Connector End View Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3307 Connector Terminal ID ECM/PCM/VCM Pinout Voltage The OE manufacture does not provide an ECM/PCM/VCM connector voltage pinout chart for this vehicle, only a function description. Connector End View Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3308 Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3309 Connector Terminal ID Connector End View Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3310 Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 3311 Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Page 3312 Engine Control Module: Service Precautions Control Module Service Precautions The control module is designed to withstand normal current draws associated with vehicle operations. Avoid overloading any circuit. When testing for opens or shorts, do not ground any of the control module circuits unless instructed. When testing for opens or shorts, do not apply voltage to any of the control module circuits unless instructed. Only test these circuits with a digital voltmeter J 39200, while the control module connectors remain connected to the control module. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Page 3313 Engine Control Module: Description and Operation GENERAL DESCRIPTION The VCM is located on the right hand side fenderwell. The VCM is the control center for the fuel, emissions, ignition, and automatic transmission control functions. The VCM constantly monitors the information from the various sensors. The VCM controls the component systems which affect the engine operation. The VCM alerts the driver through the Malfunction Indicator Lamp (MIL) or the antilock indicator lamp. The VCM stores the DTCs which identify the problem areas for the technician making repairs. Refer to Vehicle Control Module, for further information on using the diagnostic function of the VCM for engine operation. ^ Refer to Transmission for the diagnosis of the automatic transmission. ^ Refer to Anti-lock brakes for diagnosis of the brake system. The VCM in this vehicle is programmable. The only services allowed on the VCM is the control module replacement with the Knock Sensor (KS) calibrator Programmable Read Only Memory (PROM) transferred or the KS calibrator PROM only. The KS calibrator contains the up integrated knock sensor calibration. The VCM stores the 4 calibrations in the Electronically Erasable Programmable Read Only Memory (EEPROM). When replacing the VCM, programming the EEPROM and transferring the KS calibrator PROM to the new VCM is mandatory. Refer to the EEPROM Programming. Refer to VCM Replacement/Programming. See: Service and Repair The 4 calibrations required for the VCM are the Powertrain, the ABS, the VSS buffer, and the A/C. Each calibration has its own part number. Determine the correct calibrations for a particular vehicle based on the VIN number of the vehicle. MALFUNCTION INDICATOR LAMP (MIL) The MIL (Malfunction Indicator Lamp) is on the instrument panel. The MIL has the following functions: ^ The MIL informs the driver that a fault that affects the vehicle's emission levels has occurred. The owner should take the vehicle for service as soon as possible. ^ As a bulb and system check, the MIL (Malfunction Indicator Lamp) comes on with the key on and the engine not running. When the engine is started, the MIL turns off if no DTCs are set. When the MIL remains on while the engine is running, or when a malfunction is suspected due to a driveability or emissions problem, perform an On-Board Diagnostic (OBD) System Check. The procedures for these checks are given in engine controls. These checks expose faults which the technician may not detect if other diagnostics are performed first. DIAGNOSTIC INFORMATION The diagnostic Tables and functional checks are designed to locate a faulty circuit or component through a process of logical decisions. The Tables are prepared with the assumption that the vehicle functioned correctly at the time of assembly and that there are not multiple faults present. There is a continuous self-diagnosis on certain control functions. This diagnostic capability is complemented by the diagnostic procedures contained in this manual. The language of communicating the source of the malfunction is a system of diagnostic trouble codes. When a malfunction is detected by the control module, a diagnostic trouble code will set and the Malfunction Indicator Lamp (MIL) Malfunction Indicator Lamp will illuminate on some applications. VCM LEARNING ABILITY WARNING: Since the VCM is located under the hood, its connectors are sealed and cannot be backprobed as in the previous model years. Do not attempt to backprobe as a connector or seal damage could occur. The VCM's learning ability allows it to make corrections for minor variations in the fuel system in order to improve driveability. When the battery is disconnected for other repairs, the learning process resets. The driver my note a change in the vehicle's performance. In order to teach the vehicle ensure that the engine is at the operating temperature. Drive the vehicle at part throttle with a moderate acceleration and idle conditions until normal performance returns. INPUT INFORMATION The VCM processes the various input information. Then the VCM sends the necessary electrical responses to the control fuel delivery, the spark timing, and the other emission control systems. The input information interrelates to more than one output; therefore, if the one input fails, the failure can affect more than one system's operation. PROM (KS Module) This assembly contains an electronic Knock Sensor (KS) module. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Page 3314 MEMORY There are two types of memory storage within the VCM, EEPROM and RAM. EEPROM Electrically Erasable Programmable Read Only Memory (EEPROM) is a permanent memory that is physically soldered to the circuit boards within the VCM. The EEPROM contains the overall control algorithms. The EEPROM can be reprogrammed by using the scan tool. RAM Random Access Memory (RAM) is the microprocessor scratch pad. The processor can write into or read from this memory as needed. This memory is volatile and needs a constant supply of voltage to be retained. If the voltage is lost, the memory is lost. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Testing and Inspection > Component Tests and General Diagnostics Engine Control Module: Component Tests and General Diagnostics The approved procedure for diagnosing all powertrain control system faults is included in the Strategy Based Diagnostics. The preliminary checks and the Powertrain On-board Diagnostic System Check must be performed to successfully diagnose and repair the powertrain systems. To read and clear diagnostic trouble codes, use a scan tool. See: Computers and Control Systems/Testing and Inspection Use a scan tool to clear diagnostic trouble codes from the VCM memory. Diagnostic trouble codes can also be cleared by turning OFF the ignition and disconnecting the battery power from the VCM for 30 seconds, but this method will also cause all diagnostic information in the VCM memory to be cleared and all the diagnostic tests will have to be re-run. Since the VCM can have a failure which may affect only one circuit, following the approved diagnostic procedures will determine which circuit has a problem and where it is. If a diagnostic table indicates that the VCM connections or VCM is the cause of a problem and the VCM is replaced. but does not correct the problem, one of the following conditions may exist: ^ There is a problem with the VCM terminal connections. The diagnostic table will indicate that the VCM connections or VCM is the problem. The terminals may have to be removed from the VCM connector in order to check them properly. ^ The EEPROM program is not correct for the application. Incorrect components may cause a malfunction and may or may not set a DTC. ^ The problem is intermittent. This means that the problem is not present at the time the system is being checked. In this case, refer to Symptoms and make a careful visual and physical inspection of all suspected components and wiring associated with the affected system. See: Computers and Control Systems/Testing and Inspection ^ There is a shorted solenoid, relay coil, or harness. Solenoids and relays are turned ON and OFF by the VCM using internal electronic switches called drivers. Each driver is part of a group of seven called output driver modules. A shorted solenoid, relay coil, or harness will not damage the VCM but will cause the solenoid or relay to be inoperative. The J 34636 tester, or equivalent, provides a fast, accurate means of checking for a shorted coil or a short to battery voltage. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Service and Repair > Control Module Replacement Engine Control Module: Service and Repair Control Module Replacement VCM Harness Connections VCM Access Cover Removing Knock Sensor Module From PCM Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Service and Repair > Control Module Replacement > Page 3319 VCM REPLACEMENT/PROGRAMMING Service of the VCM consists of either replacement of VCM or reprogramming of the EEPROM. If the diagnostics call for replacement of the VCM, it will be necessary to transfer the PROM and program the EEPROM. NOTE: When replacing the production VCM with a service VCM (controller), it is important to transfer the broadcast code and production VCM number to the service VCM label. This will allow positive identification of VCM parts throughout the service life of the vehicle. Also transfer the PROM. CAUTION: To prevent internal VCM damage, the ignition must be OFF when disconnecting or reconnecting power to the VCM (for example, battery cable, VCM fuse, jumper cables, etc.). CAUTION: In order to prevent possible Electrostatic Discharge damage to the VCM, do not touch the connector pins or soldered components on the circuit board. VCM REPLACEMENT/PROGRAMMING (WITH KNOCK SENSOR (KS) CALIBRATION PROM) REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Remove the connectors from the VCM. 3. Remove the spring retainer off and over the rail of the VCM. Slide the VCM out of the bracket at an angle. 4. Remove the VCM access cover. 5. Remove the PROM/Knock Sensor (KS) module. 6. Inspect for the alignment notches of the KS Calibration PROM. 7. Carefully set it aside. 8. Do not open the KS Calibration PROM. 9. Remove the new VCM from the packaging. Check the service number in order to make sure it is the same as the defective VCM. 10. Remove the access cover. NOTE ^ The Knock Sensor (KS) module must be transferred to the replacement VCM. ^ The replacement VCM is supplied without a EEPROM program, the replacement VCM must be programmed before the vehicle will run. ^ Using the thumb and first finger, remove the KS Calibration PROM by gently squeezing each end of the blue KS Calibration PROM ^ Do not remove the cover of the KS Calibration PROM. Use of an unapproved KS Calibration PROM removal methods may cause damage to the KS Calibration PROM or the socket. INSTALLATION PROCEDURE NOTE: Press only on the ends of the KS Calibration PROM. Gently press on the KS Calibration PROM until it is firmly seated in the socket. Listen for the click. 1. Align the notches of the KS Calibration PROM with the notches in the KS Calibration PROM socket. 2. Install the KS Calibration PROM in the KS Calibration PROM socket. 3. Install the access cover on the VCM. 4. Install the VCM in the engine compartment. 5. Install the connectors to the VCM. 6. The MIL, antilock and brake lamps will continue to be enabled until the VCM is programmed. Once the programming is complete, the lamps will turn off and normal operation will occur. 7. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Service and Repair > Control Module Replacement > Page 3320 CAUTION: In order to prevent possible Electrostatic Discharge damage to the VCM, do not touch the connector pins or soldered components on the circuit board. 8. Proceed to the EEPROM programming. See: EEPROM Programming Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Service and Repair > Control Module Replacement > Page 3321 Engine Control Module: Service and Repair EEPROM Programming CAUTION: The ignition should always be "off" when installing or removing the Vehicle Control Module (VCM) connectors. 1. Set-up: ^ Battery is charged. ^ Ignition is "ON." ^ Battery/cig. lighter Connection secure. ^ Data Link Connector (DLC). 2. Refer to up-to-date Techline terminal/equipment user's instructions. 3. If Vehicle Control Module (VCM) fails to program, do the following: ^ Check all VCM connections. ^ check Techline terminal/equipment for latest software version. ^ Try again to program the VCM. If it fails again, replace the VCM. Refer to VCM replacement. See: Control Module Replacement 4. Perform the Idle Air Control (IAC) valve reset procedure with the scan tool. use misc. test. 5. For a functional check perform one of the steps: ^ Use the Techline terminal and equipment in order to perform the On-Board Diagnostic (OBD) System Check ^ Refer to Powertrain OBD System Check. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Knock Sensor Module > Component Information > Diagrams Knock Sensor Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Emission Control Systems > Air Injection Pump Relay > Component Information > Locations Air Injection Pump Relay: Locations Underhood Fuse-Relay center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Locations Fuel Pump Balance Module: Locations FUEL PUMP BALANCE MODULE (Vehicles with Dual Tanks Only) On vehicles over 15,000 GVWR and equipped with dual fuel tanks, the Fuel Pump Balance Module is located inside the left frame rail, near Transmission Crossmember. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Locations > Page 3333 Fuel Pump Balance Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Locations > Page 3334 Fuel Pump Balance Module: Description and Operation FUEL BALANCE CONTROL SYSTEM The fuel balance control system consists of the following components: - Front (main) fuel tank sender. - Rear (auxiliary) fuel tank sender. - Balance fuel pump. - Balance fuel pump relay. - Fuel sender and balance module. On vehicles with dual tanks, the front tank is the main and the rear tank is the auxiliary. The main fuel pump supplies fuel to the fuel injection unit. The low pressure (about 32 kPa or 7 psi) fuel balance pump is used only to transfer fuel from the auxiliary tank to the main tank in order to balance the fuel levels in both tanks. As the main tank level drops to about 25 % below the level in the auxiliary tank, the fuel sender and balance module energizes the fuel pump relay. This pumps the fuel from the auxiliary tank to the main tank. When the level in the main tank reaches a level slightly higher than the level in the auxiliary tank, or the auxiliary tank is empty, the module de-energizes the balance pump relay and fuel pump. Any malfunction in either of the fuel gage circuits will disable the system and the fuel will not be transferred from the main fuel tank to the auxiliary fuel tank. FUEL PUMP BALANCE MODULE The Fuel Pump Balance Module relies on input from the primary and secondary fuel senders, and cannot operate if the fuel gauge is not working properly. For Fuel Pump Balance Module testing and inspection refer to Instrument Panel, Gauges and Warning Indicators / Symptom Releated Diagnostic Procedures / Fuel Gauge See: Instrument Panel, Gauges and Warning Indicators/Testing and Inspection/Symptom Related Diagnostic Procedures For Fuel Pump Balance Module electrical diagrams refer to Instrument Panel, Gauges and Warning Indicators / Diagrams / Electrical. See: Instrument Panel, Gauges and Warning Indicators/Diagrams Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times Fuel Gage Indicates Empty At All Times Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times > Page 3337 Fuel Gage Indicates Full At All Times Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times > Page 3338 Fuel Pump Balance Module: Testing and Inspection Fuel Gage Is Inaccurate Fuel Gage Is Inaccurate (Part 1 Of 2) Fuel Gage Is Inaccurate (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times > Page 3339 Fuel Pump Balance Module: Testing and Inspection Vehicle Runs Out of Fuel (Rear Tank Not Empty) Vehicle Runs Out Of Fuel At Half-Full/rear Tank Is Full At All Times (Part 1 Of 2) Vehicle Runs Out Of Fuel At Half-Full/rear Tank Is Full At All Times (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times > Page 3340 Fuel Gage Does Not Change Position On Scale Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Page 3341 Fuel Pump Balance Module: Service and Repair REMOVAL PROCEDURE WARNING: To reduce the risk of fire and personal in jury that may result from a fuel leak, always replace O-ring seals exposed during component service. 1. Disconnect the negative battery cable. 2. Loosen the filler cap(s) to Relieve fuel tank pressure. See: Fuel Delivery and Air Induction/Service and Repair 3. Disconnect the electrical connector. 4. Clean both fuel pipe connections and surrounding areas at the fuel pump before disconnecting to avoid possible contamination of the fuel system. 5. Disconnect both fuel pipes from the pump. 6. Slide the pump out of the bracket. INSTALLATION PROCEDURE 1. Install the new fuel pipe O-rings. 2. Position the new pump in the pump bracket. 3. Connect the fuel feed pipe and suction pipe to the fuel pump. Tighten Use a backup wrench to prevent the pump from turning. Tighten the fittings to 3O Nm (22 lb. ft.). 4. Connect the electrical connector. 5. Connect the negative battery cable. 6. Check for fuel leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Page 3342 6.1. Turn the ignition ON for 2 seconds. 6.2. Turn OFF the ignition for 10 seconds. 6.3. Again, turn the ignition switch to the ON position. 6.4. Check for fuel leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Locations > Fuel Pump Relay Fuel Pump Relay: Locations Fuel Pump Relay FUEL PUMP RELAY Auxiliary Battery Wiring Underhood Fuse-Relay Center The Fuel Pump Relay is located in Underhood Fuse Relay Center. The Underhood Fuse Relay Center is located on the LH rear of engine compartment, on fender. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Locations > Fuel Pump Relay > Page 3347 Fuel Pump Relay: Locations Fuel Pump Relay (Balance Pump) FUEL PUMP RELAY (BALANCE PUMP) (Vehicles with Dual Tanks Only) On vehicles over 15,000 GVWR and equipped with dual fuel tanks, the Fuel Pump Balance Relay is located inside the left frame rail, near Transmission Crossmember. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions Fuel Pump Relay: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3350 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3351 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3352 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3353 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3354 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3355 Fuel Pump Relay: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3356 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3357 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3358 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3359 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3360 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3361 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3362 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3363 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3364 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3365 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3366 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3367 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3368 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3369 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3370 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3371 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3372 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3373 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3374 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3375 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3376 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3377 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3378 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3379 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3380 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3381 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3382 Fuel Pump Relay: Connector Views Fuel Pump Balance Relay Fuel Pump Relay FUEL PUMP RELAY CONNECTOR VIEW Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 3383 Underhood Fuse-Relay Center (Part 1 Of 2) The Fuel Pump Relay is located in the Underhood Fuse-Relay Center. Refer to terminals, A1 - B1 B2 - A3 - B3. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Description and Operation > Fuel Pump Relay Operation Fuel Pump Relay: Description and Operation Fuel Pump Relay Operation OPERATION When the key is turned ON with out the engine running, the control module turns a fuel pump relay ON for two seconds. This builds up fuel pressure quickly. If the engine is not started within two seconds, the control module shuts the fuel pump OFF and waits until the engine starts. As soon as the engine is cranked, the control module turns the relay ON and runs the fuel pump. When the engine is cranking or running, the control module receives the Crankshaft Position (CKP) sensor reference pulses which in turn energize the fuel injectors. As a backup system to the fuel pump relay, the fuel pump can also be turned ON by a fuel pump oil pressure switch. When the engine reaches about 28 kPa (4 psi), and the fuel pump relay does not complete the circuit, the fuel pump oil pressure switch will close to complete the circuit to run the fuel pump. An inoperative fuel pump relay can result in long cranking times, particularly if the engine is cold. The fuel pump oil pressure switch will turn ON the fuel pump as soon as oil pressure reaches about 28 kPa (4 psi). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Description and Operation > Fuel Pump Relay Operation > Page 3386 Fuel Pump Relay: Description and Operation Fuel Balance Module Control System (Dual Tanks) FUEL BALANCE CONTROL SYSTEM The fuel balance control system consists of the following components: - Front (main) fuel tank sender. - Rear (auxiliary) fuel tank sender. - Balance fuel pump. - Balance fuel pump relay. - Fuel sender and balance module. On vehicles with dual tanks, the front tank is the main and the rear tank is the auxiliary. The main fuel pump supplies fuel to the fuel injection unit. The low pressure (about 32 kPa or 7 psi) fuel balance pump is used only to transfer fuel from the auxiliary tank to the main tank in order to balance the fuel levels in both tanks. As the main tank level drops to about 25 % below the level in the auxiliary tank, the fuel sender and balance module energizes the fuel pump relay. This pumps the fuel from the auxiliary tank to the main tank. When the level in the main tank reaches a level slightly higher than the level in the auxiliary tank, or the auxiliary tank is empty, the module de-energizes the balance pump relay and fuel pump. Any malfunction in either of the fuel gage circuits will disable the system and the fuel will not be transferred from the main fuel tank to the auxiliary fuel tank. FUEL PUMP BALANCE MODULE The Fuel Pump Balance Module relies on input from the primary and secondary fuel senders, and cannot operate if the fuel gauge is not working properly. For Fuel Pump Balance Module testing and inspection refer to Instrument Panel, Gauges and Warning Indicators / Symptom Releated Diagnostic Procedures / Fuel Gauge See: Instrument Panel, Gauges and Warning Indicators/Testing and Inspection/Symptom Related Diagnostic Procedures For Fuel Pump Balance Module electrical diagrams refer to Instrument Panel, Gauges and Warning Indicators / Diagrams / Electrical. See: Instrument Panel, Gauges and Warning Indicators/Diagrams Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Description and Operation > Page 3387 Fuel Pump Relay: Service and Repair Removal Procedure 1. Remove the underhood electrical center cover. 2. Remove the relay. Installation Procedure 1. Install the relay. 2. Install the underhood electrical center cover. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Ignition System > Ignition Control Module > Component Information > Description and Operation Ignition Control Module: Description and Operation Ignition Control Driver (ICD) Module And Ignition Coil The Ignition Coil Driver Module is mounted on a bracket next to the coil. The Vehicle Control Module (VCM) signals the Ignition Control Driver (ICD) to turn "ON" primary current to the ignition coil by pulling the Ignition Control (IC) line high (4 volts). The IC turns the primary current "ON" and "OFF" by applying and removing the ground to the primary winding at the appropriate time. This module is of 'minimum function" and does not contain backup calibrations that would allow the engine to continue to rim if the IC signal is lost. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Ignition System > Ignition Control Module > Component Information > Description and Operation > Page 3392 Ignition Control Module: Testing and Inspection If the vehicle cranks for at least 5 seconds and the Engine Control Module doesn't see a referance signal, some Models will set a code, 42 (Hard) or 12 (Soft). If your vehicle has one of these codes, begin with the Diagnostic System Check in Computers and Controls, then proceed to the Trouble Code Chart (Yes, some vehicles have a DTC Chart for Code 12). If the vehicle does not set a code, begin with the Diagnostic System Check, and it will send you to a Diagnostic Chart that checks for your particular condition. These types of tests are found under Computers and Control Systems. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions Mass Air Flow (MAF) Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3399 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3400 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3401 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3402 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3403 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3404 Mass Air Flow (MAF) Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3405 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3406 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3407 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3408 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3409 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3410 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3411 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3412 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3413 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3414 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3415 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3416 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3417 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3418 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3419 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3420 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3421 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3422 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3423 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3424 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3425 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3426 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3427 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3428 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3429 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3430 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3431 Mass Air Flow System Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Page 3432 Mass Air Flow (MAF) Sensor: Description and Operation Mass Air Flow (MAF) Sensor The Mass Air Flow (MAF) sensor measures the amount of air which passes through it. The VCM uses this information to determine the operating condition of the engine, to control fuel delivery. A large quantity of air indicates acceleration. A small quantity of air indicates deceleration or idle. The scan tool reads the MAF value and displays it in grams per second (gm/Sec). At idle, it should read between 5-7 gm/Sec on a fully warmed up engine. Values should change rather quickly on acceleration, but values should remain fairly stable at any given RPM. When the VCM detects a malfunction in the MAF sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0101 system performance. ^ DTC P0102 frequency low. ^ DTC P0103 frequency high. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Page 3433 Mass Air Flow (MAF) Sensor: Service and Repair MAF Sensor MAF Sensor Intake Duct REMOVAL PROCEDURE CAUTION: Take care when handling the Mass Air Flow (MAF). Do Not dent, puncture, or otherwise damage the honeywell located at the air inlet end of the MAF. Do Not touch the sensing elements or allow anything (including solvents and lubricants) to come in contact with them. A small amount of GM lubricant (P/N 99855406) may be used on the air duct only to aid in installation. Do Not drop or roughly handle the MAF. 1. Disconnect the 3 wire electrical connector. 2. Loosen the clamp on the intake duct. 3. Carefully remove the MAF sensor. INSTALLATION PROCEDURE 1. Install the MAF sensor. 2. Install the intake ducts. 3. Tighten the clamp. 4. Connect the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Camshaft Position Sensor: Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3438 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3439 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3440 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3441 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3442 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3443 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3444 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Page 3445 Camshaft Position Sensor: Specifications Camshaft position sensor retaining screw ........................................................................................................................................... 4-6 Nm (35-53 lb. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Page 3446 Engine View, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Camshaft Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3449 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3450 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3451 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3452 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3453 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3454 Camshaft Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3455 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3456 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3457 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3458 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3459 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3460 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3461 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3462 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3463 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3464 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3465 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3466 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3467 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3468 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3469 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3470 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3471 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3472 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3473 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3474 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3475 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3476 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3477 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3478 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3479 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3480 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Page 3481 Camshaft Position Sensor: Description and Operation Camshaft Position Sensor The Camshaft Position (CMP) sensor is located within the distributor. It's operation is very similar to the Crankshaft Position (CKP) sensor however it will provide one pulse per camshaft revolution (1x signal). This signal is not detrimental to the driveability of the vehicle. The Vehicle Control Module (VCM) utilizes this signal in conjunction with the crankshaft position to determine which cylinder(s) are misfiring. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Testing and Inspection > Cam Signal Camshaft Position Sensor: Testing and Inspection Cam Signal The VCM uses this signal to determine the position of the #1 piston during its power stroke. This signal is used by the VCM to calculate fuel injection mode of operation. A loss of this signal will set DTC P0340. If the cam signal is lost while the engine is running, the fuel injection system will shift to a calculated fuel injection mode based on the last fuel injection pulse, and the engine will continue to run. The engine can be restarted and will run in the calculated mode as long as the fault is present Refer to Diagnostic Trouble Code (DTC) P0340 Camshaft Position Sensor (CKP) Sensor Circuit. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Camshaft Position Sensor > Component Information > Testing and Inspection > Page 3484 Camshaft Position Sensor: Service and Repair REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Disconnect the electrical connector from the camshaft position sensor. 3. Remove the camshaft position sensor retaining screw. 4. Remove the camshaft position sensor. INSTALLATION PROCEDURE 1. Install the camshaft position sensor. 2. Install the camshaft position sensor retaining screw, torque to 4-6 Nm (35-53 lb. in.). 3. Connect the electrical connector. 4. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Specifications Coolant Temperature Sensor/Switch (For Computer): Specifications Engine Coolant Temperature (ECT) sensor .............................................................................................................................................. 13 Nm (10 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Specifications > Page 3488 Engine Side, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions Coolant Temperature Sensor/Switch (For Computer): Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3491 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3492 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3493 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3494 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3495 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3496 Coolant Temperature Sensor/Switch (For Computer): Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3497 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3498 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3499 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3500 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3501 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3502 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3503 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3504 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3505 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3506 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3507 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3508 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3509 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3510 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3511 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3512 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3513 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3514 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3515 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3516 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3517 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3518 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3519 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3520 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3521 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3522 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 3523 ECT Sensor Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 3524 Coolant Temperature Sensor/Switch (For Computer): Description and Operation Engine Coolant Temperature (ECT) Sensor DESCRIPTION The engine coolant temperature sensor is a thermistor (a resistor which changes value based on temperature) mounted in the engine coolant passage. Low coolant temperature produces a high resistance 100,000 ohms at -40°C (-40°F) while high temperature causes low resistance 70 ohms at 130°C (266°F). OPERATION The VCM supplies a 5 volt signal to the engine coolant temperature sensor through a resistor in the VCM and measures the voltage. The voltage will be high when the engine is cold. The voltage will be low when the engine is hot. By measuring the voltage, the VCM calculates the engine coolant temperature. Engine coolant temperature affects most systems the VCM controls. The scan tool displays engine coolant temperature in degrees. After engine start-up, the temperature should rise steadily to about 9O°C (194°F) then stabilize when thermostat opens. If the engine has not been run for several hours (overnight), the engine coolant temperature and intake air temperature displays should be close to each other. When the VCM detects a malfunction in the Engine Coolant Temperature (ECT) sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0117 circuit low. ^ DTC P0118 circuit high. ^ DTC P0125 excessive time to Closed Loop. ^ DTC P1114 circuit intermittent low. ^ DTC P1115 circuit intermittent high. The above DTCs contain a table to check for sensor resistance values relative to temperature. Refer to Specifications. See: Computers and Control Systems/Specifications Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 3525 Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection The scan tool displays engine coolant temperature in degrees. After engine start-up, the temperature should rise steadily to about 90°C (194°F) then stabilize when thermostat opens. If the engine has not been run for several hours (overnight), the engine coolant temperature and intake air temperature displays should be close to each other. When the VCM detects a malfunction in the Engine Coolant Temperature (ECT) sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0117 circuit low. ^ DTC P0118 circuit high. ^ DTC P0125 excessive time to Closed Loop. ^ DTC P1114 circuit intermittent low. ^ DTC P1115 circuit intermittent high. The above DTCs contain a table to check for sensor resistance values relative to temperature. Refer to Diagnostic Tables. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 3526 Coolant Temperature Sensor/Switch (For Computer): Service and Repair Engine Coolant Temperature (ECT) Sensor Electrical Connector Engine Coolant Temperature (ECT) Sensor CAUTION: Use care when handling the coolant sensor. Damage to the coolant sensor will affect the operation of the fuel control system. REMOVAL PROCEDURE 1. Relieve the coolant pressure. 2. Disconnect the negative battery cable. 3. Drain the cooling system below the level of the sensor. 4. Disconnect the electrical connector releasing locking tab. 5. Remove the coolant sensor from engine. INSTALLATION PROCEDURE 1. Coat the threads (only) with sealer P/N 9985253 or equivalent. Tighten ^ Tighten the sensor to 13 N.m (10 lb. ft.). 2. Install the coolant sensor in the engine. 3. Connect the electrical connector. 4. Refill the cooling system. 5. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-014 > Apr > 00 > Engine - No/Hard/Slow Start/Backfire/Kickback Crankshaft Position Sensor: Customer Interest Engine - No/Hard/Slow Start/Backfire/Kickback File In Section: 06 - Engine/Propulsion System Bulletin No.: 00-06-04-014 Date: April, 2000 TECHNICAL Subject: No, Hard, or Slow Start, Backfire or "Kickback" During Crank/Start, "Grinding" or Unusual Noises During Crank, DTC P0338 (Replace Crankshaft Position Sensor) Models: 1999-2000 Cadillac Escalade 1995-2000 Chevrolet and GMC SIT Models 1996-2000 Chevrolet and GMC C/K, M/L, G, P Models 1996-2000 Oldsmobile Bravada with 4.3 L, 5.0 L, 5.7 L or 7.4 L Engine (VINs W, X, M, R, J RPOs L35, LF6, L30, L31, L29) Condition: Some customers may comment on one or more of the following conditions: ^ Backfire during crank/start ^ "Kickback" during crank/start ^ "No" start ^ "Slow" or "hard" start/crank ^ "Grinding" or unusual noises during crank/start ^ Cracked or broken engine block at the starter boss ^ Broken starter drive housing ^ Broken starter ring gear on flywheel ^ Any combination of the above Cause: A condition may exist that allows the crankshaft position sensor to command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss. Correction: Inspect for a stored powertrain DTC code P0338. This DTC will NOT illuminate the "Service Engine Soon" light. If this code is stored, the Crankshaft Position Sensor, P/N 10456607, MUST be replaced and the remaining components inspected for damage (engine block at the starter boss, the starter drive housing, and the engine flywheel starter ring gear). Notice: When DTC code P0338 is set, failure to replace the Crankshaft Position Sensor could result in repeated inoperative conditions of the starter or flywheel. Important: Some flywheel wear is normal; broken or missing teeth and/or cracks, are not normal. Parts Information Parts are currently available from GMSPO. Warranty Information: For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 00-06-04-014 > Apr > 00 > Engine No/Hard/Slow Start/Backfire/Kickback Crankshaft Position Sensor: All Technical Service Bulletins Engine - No/Hard/Slow Start/Backfire/Kickback File In Section: 06 - Engine/Propulsion System Bulletin No.: 00-06-04-014 Date: April, 2000 TECHNICAL Subject: No, Hard, or Slow Start, Backfire or "Kickback" During Crank/Start, "Grinding" or Unusual Noises During Crank, DTC P0338 (Replace Crankshaft Position Sensor) Models: 1999-2000 Cadillac Escalade 1995-2000 Chevrolet and GMC SIT Models 1996-2000 Chevrolet and GMC C/K, M/L, G, P Models 1996-2000 Oldsmobile Bravada with 4.3 L, 5.0 L, 5.7 L or 7.4 L Engine (VINs W, X, M, R, J RPOs L35, LF6, L30, L31, L29) Condition: Some customers may comment on one or more of the following conditions: ^ Backfire during crank/start ^ "Kickback" during crank/start ^ "No" start ^ "Slow" or "hard" start/crank ^ "Grinding" or unusual noises during crank/start ^ Cracked or broken engine block at the starter boss ^ Broken starter drive housing ^ Broken starter ring gear on flywheel ^ Any combination of the above Cause: A condition may exist that allows the crankshaft position sensor to command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss. Correction: Inspect for a stored powertrain DTC code P0338. This DTC will NOT illuminate the "Service Engine Soon" light. If this code is stored, the Crankshaft Position Sensor, P/N 10456607, MUST be replaced and the remaining components inspected for damage (engine block at the starter boss, the starter drive housing, and the engine flywheel starter ring gear). Notice: When DTC code P0338 is set, failure to replace the Crankshaft Position Sensor could result in repeated inoperative conditions of the starter or flywheel. Important: Some flywheel wear is normal; broken or missing teeth and/or cracks, are not normal. Parts Information Parts are currently available from GMSPO. Warranty Information: For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls Revised DTC P1345 (CKP/CMP) Diagnosis Crankshaft Position Sensor: All Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3544 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3545 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3546 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3547 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3548 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3549 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3550 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Crankshaft Position Sensor: All Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3556 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3557 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3558 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3559 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3560 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3561 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 3562 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Page 3563 Crankshaft Position Sensor: Specifications Crankshaft Position Sensor mounting bolts ................................................................................................................................................. 8 Nm (71 lb. In.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Page 3564 Engine Side, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Crankshaft Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3567 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3568 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3569 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3570 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3571 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3572 Crankshaft Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3573 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3574 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3575 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3576 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3577 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3578 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3579 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3580 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3581 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3582 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3583 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3584 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3585 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3586 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3587 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3588 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3589 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3590 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3591 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3592 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3593 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3594 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3595 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3596 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3597 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3598 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Page 3599 Crankshaft Position Sensor: Description and Operation DESCRIPTION The Crankshaft Position (CKP) Sensor is located in the front engine cover and is perpendicular to the crankshaft target wheel. The air gap between the sensor and the wheel is preset and not adjustable. The target wheel has three slots 60° apart and is keyed to the crankshaft. As the target wheel rotates, the slots passing by the sensor create a change in the magnetic field of the sensor which results in an induced voltage pulse. One revolution of the crankshaft results in three pulses (3x signal). Based on these pulses, the VCM is able to determine crankshaft position and engine speed. The VCM then activates the fuel injector and provides a spark to the Distributor. The relation between the crankshaft position sensor and the target wheel is crucial. The sensor must be exactly perpendicular to the target wheel with the correct air gap. OPERATION The crankshaft position sensor provides the VCM with crankshaft speed and crankshaft position. The VCM utilizes this information to determine if an engine Misfire is present. The VCM monitors the Crankshaft Position Sensor (CKP) sensor for momentarily drop in crankshaft speed to determine if a misfire is occurring. When the VCM detects a misfire, a Diagnostic Trouble Code (DTC) P0300 will set. The VCM also monitors the CKP sensor signal circuit for malfunctions. The VCM monitors CKP signal and the High and Low resolution signals. The VCM calculates these signals to determine a ratio. When the VCM detects that the ratio is out of normal operating range, the VCM will set a Diagnostic Trouble Code (DTC) P0337 or a DTC P0338. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Page 3600 Crankshaft Position Sensor: Service and Repair REMOVAL PROCEDURE 1. Remove the electrical connector. 2. Remove the sensor hold down bolt. 3. Remove the sensor from the timing cover. NOTE: When installing or removing a crankshaft position (CKP) sensor make sure the sensor is fully seated and held stationary in the front cover before torquing the hold down bolt into the front cover. A sensor which is not seated may result in erratic operation and lead to the setting of false codes. 4. Inspect the sensor O-ring for wear, cracks or leakage. Replace if necessary. Lube the new O-ring with clean engine oil before installing. INSTALLATION PROCEDURE NOTE: Make certain that the Crankshaft Position (CKP) sensor mounting surfaces are clean and free of burrs before installing the CKP sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Page 3601 1. Install the sensor into the timing cover. 2. Install the sensor hold down bolt. Tighten ^ Tighten the hold down bolt to 8 Nm (71 lb. in.). 3. Install the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Specifications Intake Air Temperature (IAT) Sensor: Specifications Torque Valve Torque Valve Induction Air Sensor 44 in.lb Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions Intake Air Temperature (IAT) Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3607 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3608 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3609 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3610 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3611 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3612 Intake Air Temperature (IAT) Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3613 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3614 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3615 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3616 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3617 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3618 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3619 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3620 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3621 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3622 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3623 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3624 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3625 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3626 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3627 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3628 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3629 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3630 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3631 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3632 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3633 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3634 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3635 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3636 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3637 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3638 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3639 IAT Sensor Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Page 3640 Intake Air Temperature (IAT) Sensor: Description and Operation Intake Air Temperature (IAT) Sensor PURPOSE The Intake Air Temperature (IAT) sensor is a thermistor which changes value based on the temperature of air entering the engine. OPERATION Low temperature produces a high resistance 100,000 ohms at -40° (-40°F). A high temperature causes low resistance 70 ohms at 130°C (266°F). The VCM supplies a 5.0 volt signal to the sensor through a resistor in the VCM and measures the voltage. The voltage will be high when the incoming air is cold, and low when the air is hot. By measuring the voltage, the VCM calculates the incoming air temperature. The IAT sensor signal is used to adjust spark timing according to incoming air density. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Page 3641 Intake Air Temperature (IAT) Sensor: Testing and Inspection The scan tool displays temperature of the air entering the engine, which should read close to ambient air temperature when engine is cold, and rise as underhood temperature increases. If the engine has not been run for several hours (overnight) the Intake Air Temperature (IAT) sensor temperature and engine coolant temperature should read close to each other. If the VCM detects a malfunction in the AT sensor circuit, the following DTCs will set: ^ DTC P0112 circuit low. ^ DTC P0113 circuit high. ^ DTC P0111 circuit intermittent high. ^ DTC P0112 circuit intermittent low. Refer to Diagnostic Tables. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Page 3642 Intake Air Temperature (IAT) Sensor: Service and Repair IAT Sensor And Electrical Connector REMOVAL PROCEDURE 1. Disconnect the electrical connector releasing locking tab. 2. Remove the Intake Air Temperature (IAT) sensor by grasping sensor, twist and pull out from air cleaner INSTALLATION PROCEDURE 1. Install the IAT sensor. 2. Connect the electrical connector Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Specifications Knock Sensor: Specifications Knock sensor ....................................................................................................................................... ....................................................... 19 Nm (14 lb. ft.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Specifications > Page 3646 Knock Sensor: Locations Engine View, Rear LH side of Engine Block, below Exhaust Manifold, forward of Starter Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions Knock Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3649 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3650 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3651 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3652 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3653 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3654 Knock Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3655 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3656 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3657 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3658 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3659 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3660 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3661 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3662 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3663 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3664 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3665 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3666 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3667 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3668 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3669 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3670 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3671 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3672 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3673 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3674 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3675 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3676 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3677 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3678 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3679 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3680 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3681 Knock Sensor Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Page 3682 Knock Sensor: Description and Operation Description The Knock Sensor (KS) system is used to detect engine detonation The VCM will retard the spark timing based on the signals from the KS module. The Knock Sensor(s) produce an AC voltage that is sent to the KS module. The amount of AC voltage produced is proportional to the amount of knock. Operation An operating engine produces a normal amount of engine mechanical vibration (Noise). The knock sensor(s) will produce an AC voltage signal from this Noise. When an engine is operating, the VCM will learn the minimum and maximum frequency of the noise the engine produces. When the VCM determines that this frequency is less than or greater than the expected amount, a knock sensor DTC will set. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Page 3683 Knock Sensor: Service and Repair Diagram Removal Procedure NOTE: The knock sensor is located in areas of the cylinder head. On most applications, the knock sensors are installed in a hole which is exposed to engine coolant. Care should be exercised when servicing these sensors. 1. Disconnect the negative battery cable. Important: On knock sensors which are mounted in the end of the cylinder head draining the cooling system will not be necessary. 2. Drain the cooling system. Refer to Draining and Filling Cooling System. 3. Remove the wiring harness connector from knock sensor. 4. Remove the knock sensor from cylinder head. Installation Procedure Important: Do not use silicon tape as this will insulate the sensor from the engine block. 2. After applying a water base caulk to the sensor threads, install the knock sensor into the cylinder head. Tighten ^ Tighten to 19 Nm (14 lb. ft.). 2. Connect the negative battery cable. 3. Refill cooling system if required. Refer to Draining and Filling Cooling System. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Locations Engine Side, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions Manifold Absolute Pressure (MAP) Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3689 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3690 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3691 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3692 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3693 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3694 Manifold Absolute Pressure (MAP) Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3695 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3696 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3697 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3698 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3699 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3700 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3701 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3702 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3703 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3704 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3705 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3706 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3707 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3708 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3709 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3710 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3711 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3712 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3713 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3714 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3715 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3716 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3717 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3718 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3719 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3720 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3721 MAP System Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Page 3722 Manifold Absolute Pressure (MAP) Sensor: Description and Operation Manifold Absolute Pressure (MAP) Sensor PURPOSE The Manifold Absolute Pressure (MAP) sensor responds to changes in the intake manifold pressure. The pressure changes as a result of engine load and speed. The map sensor converts this to a voltage output. OPERATION A closed throttle on engine coast down would produce a relatively low MAP output voltage. A wide open throttle would produce a high MAP output voltage. This high output voltage is produced because the pressure inside the manifold is the same as outside the manifold. The MAP is inversely proportional to what is measured on a vacuum gage. The MAP sensor is used for the following: ^ Altitude determination. ^ Ignition timing control. ^ Exhaust Gas Recirculation (EGR) diagnostic. ^ Speed density fuel management default. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Page 3723 Manifold Absolute Pressure (MAP) Sensor: Testing and Inspection When the VCM detects a malfunction in the MAP sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0106 circuit performance. ^ DTC P0107 circuit low. ^ DTC P0108 circuit high. ^ DTC P1106 intermittent circuit high. ^ DTC P1107 intermittent circuit low. Refer to System Diagnosis / Diagnostic Charts for testing information. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Page 3724 Manifold Absolute Pressure (MAP) Sensor: Service and Repair MAP Sensor NOTE: Other than checking for loose hoses and electrical connections, the only service possible is unit replacement, if the diagnosis shows the sensor to be faulty. REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Disconnect the vacuum harness assembly. 3. Disconnect the electrical connector releasing locking tab. 4. Remove the bolts or release lock tabs and remove the sensor. INSTALLATION PROCEDURE 1. Install the bolts or snap sensor on bracket. 2. Connect the electrical connector. 3. Connect the vacuum harness. 4. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Oxygen Sensor - Locations in Various Exhaust Systems Oxygen Sensor: Technical Service Bulletins Oxygen Sensor - Locations in Various Exhaust Systems File In Section: 6E - Engine Fuel & Emission Bulletin No.: 67-65-40 Date: March, 1997 INFORMATION Subject: Pictorial of Oxygen Sensor Designations in Various Exhaust Systems Configurations Models: 1996-97 Passenger Cars, Geos and Trucks Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Oxygen Sensor - Locations in Various Exhaust Systems > Page 3729 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Oxygen Sensor - Locations in Various Exhaust Systems > Page 3730 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Oxygen Sensor - Locations in Various Exhaust Systems > Page 3731 Pictorials of the designation of oxygen sensors in General Motors vehicles. There has been some confusion relative to OBD II oxygen sensor designation. The intent of this bulletin is to eliminate misdiagnosis of those oxygen sensors due to misidentification. When using Section 6E of the Service Manual, this chart can help locate the appropriate bank and sensor for the diagnostic. For "V" engines; BANK 1 is always on the side of the engine with the number 1 cylinder (odd cylinders), and BANK 2 is always on the side of the engine where the number 2 cylinder (even cylinders) is located. Just a reminder, the OBD II P-codes, technician observations and customer comments are all to be recorded on the repair order in accordance with article 1.6.2G of the GM Service Policies and Procedures Manual. Use the approved labor operation for the sensors replaced. J 6372 is used for engine out sensors. Labor Operation J 6380 is for the pre-sensor (the sensor just in front of the catalytic converter) and the post sensor (the sensor behind the catalytic converter). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Page 3732 Oxygen Sensor: Specifications Heated Oxygen Sensor (HO2S) .......................................................................................................... ...................................................... 41 Nm (30 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations Oxygen Sensor: Component Locations Light Duty Vehicles Bulletin No.: 67-65-40 PICTORIALS OF THE DESIGNATION OF OXYGEN SENSORS There has been some confusion relative to OBD II oxygen sensor designation. The intent of this article is to eliminate misdiagnosis of those oxygen sensors due to mis-identification. This chart can help locate the appropriate bank and sensor for the diagnostic. NOTE: For "V" engines; BANK 1 is always on the side of the engine with the number 1 cylinder (odd cylinders), and BANK 2 is always on the side of the engine where the number 2 cylinder (even cylinders) is located. Heavy Duty Vehicles Bulletin No.: 67-65-40 PICTORIALS OF THE DESIGNATION OF OXYGEN SENSORS Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 3735 There has been some confusion relative to OBD II oxygen sensor designation. The intent of this article is to eliminate misdiagnosis of those oxygen sensors due to mis-identification. This chart can help locate the appropriate bank and sensor for the diagnostic. NOTE: For "V" engines; BANK 1 is always on the side of the engine with the number 1 cylinder (odd cylinders), and BANK 2 is always on the side of the engine where the number 2 cylinder (even cylinders) is located. 5-Speed Manual Transmission (MW3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 3736 Oxygen Sensor: Connector Locations Engine View, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 3737 Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 3738 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 3739 5-Speed Manual Transmission W/4WD 5-Speed Manual Transmission (MW3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 3740 5-Speed Manual Transmission (MW3) 5-Speed Manual Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 3741 Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions Oxygen Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3744 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3745 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3746 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3747 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3748 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3749 Oxygen Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3750 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3751 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3752 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3753 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3754 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3755 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3756 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3757 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3758 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3759 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3760 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3761 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3762 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3763 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3764 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3765 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3766 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3767 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3768 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3769 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3770 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3771 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3772 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3773 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3774 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3775 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3776 Oxygen Sensor: Connector Views C107: Engine HARN To Oxygen Sensor HARN Oxygen Sensor RH, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3777 HO2S Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Page 3778 Oxygen Sensor: Description and Operation Heated Oxygen Sensor (HO2S) Cutaway OPERATION To control emissions of Hydrocarbons (HO), Carbon Monoxide (CO), and Oxides of Nitrogen (NOx), a three-way catalytic converter is used. The catalyst within the converter promotes a chemical reaction which oxidizes the HO and CO present in the exhaust gas, converting them into harmless water vapor and carbon dioxide. The catalyst also reduces NOx, converting it to nitrogen. The VCM has the ability to monitor this process using the Bank 1 Sensor 2 and the Bank 2 Sensor 2 heated oxygen sensors. The Bank 1 Sensor 2 sensor produces an output signal which indicates the amount of oxygen present in the exhaust gas entering the three way catalytic converter. The Bank 2 Sensor 2 sensor produces an output signal which indicates the oxygen storage capacity of the catalyst; this in turn indicates the catalyst ability to convert exhaust gases efficiently. If the catalyst is operating efficiently, the Bank 1 Sensor 2 sensor will produce a far more active signal than that produced by the Bank 2 Sensor 2 sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Page 3779 The catalyst monitor sensors operate the same as the fuel control sensors. Although the Bank 1 Sensor 2 and Bank 2 Sensor 2 sensors main function is catalyst monitoring, they also play a limited role in fuel control. If a sensor output indicates a voltage either above or below the 450 millivolt bias voltage for an extended period of time, the VCM will make a slight adjustment to fuel trim to ensure that fuel delivery is correct for catalyst monitoring. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Testing and Inspection > Heated Oxygen Sensor (HO2S 1) Testing Oxygen Sensor: Testing and Inspection Heated Oxygen Sensor (HO2S 1) Testing The heated oxygen sensor circuit, if open, should set a Diagnostic Trouble Code (DTC) P0134 and the Scan tool will display a constant voltage between 350-550 mV. A constant voltage below 250 mV in the sensor circuit should set DTC P0131, while a constant voltage above 750 mV in the circuit should set DTC P0132. DTC P0131 and DTC P0132 could also be set as a result of fuel system problems. Refer to DTC P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1 or DTC P0132 HO2S Circuit High Voltage Bank 1 Sensor 1 or DTC P0134 HO2S Insufficient Activity Bank 1 Sensor 1. Refer to System Diagnosis / Diagnostic Charts for testing information. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Testing and Inspection > Heated Oxygen Sensor (HO2S 1) Testing > Page 3782 Oxygen Sensor: Testing and Inspection Heated Oxygen Sensor (HO2S 2) Testing A problem with the HO2S 2 electrical circuits should set Diagnostic Trouble Code (DTC) P0137, P0138 or P0140, depending on the specific condition. If the catalyst is functioning correctly, the HO2S 2 signal will be far less active than that produced by HO2S 1. If a problem exists which causes the VCM to detect excessive HO2S 2 activity outside of an acceptable range for an extended period of time, the VCM will set DTC P0420, indicating that the three-way catalytic converter [prime ]s oxygen storage capacity is below a threshold considered acceptable. Refer to DTC P0137 HO2S Circuit Low Voltage Bank 1 Sensor 2 or DTC P0138 HO2S Circuit High Voltage Bank 1 Sensor 2 or DTC P0140 HO2S Insufficient Activity Bank 1 Sensor 2 or DTC P0420 TWC System Low Efficiency Bank 1. Refer to System Diagnosis / Diagnostic Charts for testing information. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Testing and Inspection > Page 3783 Oxygen Sensor: Service and Repair Heated Oxygen Sensor (HO2S) Electrical Connector Heated Oxygen Sensor (HO2S) REMOVAL PROCEDURE CAUTION: The Heated Oxygen Sensor (HO2S) and the Oxygen Sensor use a permanently attached pigtail and connector. Do not remove this pigtail from the Heated Oxygen Sensor. Damage or the removal of the pigtail or the connector could affect the proper operation of the sensor. CAUTION: Take care when handling the HO2S. Keep the in-line electrical connector and the louvered end free of grease, dirt, or other contaminants. Also avoid using cleaning solvents of any type. Do not drop or roughly handle the HO2S. CAUTION: If the heated oxygen sensor pigtail wiring, connector or terminal is damaged, the entire oxygen sensor assembly must be replaced. Do Not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. CAUTION: This clean air reference is obtained by way of the oxygen sensor signal and heater wires. Any attempt to repair the wires, connectors, or terminals could result in the obstruction of the air reference and degraded sensor performance. The following guidelines should be used when servicing the heated oxygen sensor: ^ Do Not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. ^ The sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems, ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do Not remove or defeat the oxygen sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will cause poor engine performance. ^ To prevent damage due to water intrusion. be sure that the peripheral seal remains intact on the vehicle harness connector. The engine harness Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Oxygen Sensor > Component Information > Testing and Inspection > Page 3784 may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. CAUTION: The Heated Oxygen Sensor (HO2S) may be difficult to remove when the engine temperature is below 48°C (120°F). Excessive force may damage the threads in the exhaust manifold or the exhaust pipe. 1. Disconnect the negative battery cable. 2. Remove the electrical connector by releasing the locking tab. 3. Carefully back out the heated oxygen sensor. INSTALLATION PROCEDURE NOTE: A special anti-seize compound is used on the Heated Oxygen Sensor (HO2S) threads. The compound consists of liquid graphite and glass beads. The graphite tends to burn away, but the glass beads remain, making the sensor easier to remove. New, or service replacement sensors already have the compound applied to the threads. If the sensor is removed from an engine and if for any reason it is to be reinstalled, the threads must have anti-seize compound applied before the reinstallation. 1. Coat the threads of the oxygen sensor with anti-seize compound GM P/N 5613695 or the equivalent if necessary. 2. Install the sensor. Tighten ^ Tighten the sensor to 41 Nm (30 lb. ft.). 3. Install the electrical connector. 4. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Specifications Throttle Position Sensor: Specifications Screw assemblies ................................................................................................................................ .................................................. 2.0 Nm (18.0 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Specifications > Page 3788 Engine Side, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Throttle Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3791 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3792 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3793 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3794 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3795 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3796 Throttle Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3797 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3798 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3799 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3800 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3801 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3802 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3803 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3804 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3805 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3806 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3807 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3808 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3809 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3810 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3811 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3812 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3813 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3814 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3815 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3816 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3817 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3818 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3819 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3820 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3821 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3822 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3823 TP Sensor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Page 3824 Throttle Position Sensor: Description and Operation Diagram The non-adjustable Throttle Position (TP) sensor is mounted on the throttle body assembly opposite the throttle lever. The TP sensor senses the throttle valve angle and relays that information to the VCM. Knowledge of throttle angle is one of the inputs needed by the VCM to generate the required injector control signals (pulses). For further information on replacement, refer to TP Sensor. See: Service and Repair Legend (1) Throttle Body Assembly. (2) IAC Valve Assembly 0-ring. (3) IAC Valve Assembly Attaching Screw. (4) Idle Air Control (IAC) Valve Assembly. (5) TP Sensor 0-ring (6) Throttle Position (TP) Sensor. (7) TP Sensor Attaching Screw. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Testing and Inspection > Throttle Position (TP) Sensor Throttle Position Sensor: Testing and Inspection Throttle Position (TP) Sensor When the VCM detects a malfunction with the Throttle Position (TP) sensor circuits, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0121 circuit performance ^ DTC P0122 circuit low. ^ DTC P0123 circuit high. ^ DTC P1121 intermittent circuit high. ^ DTC P1122 intermittent circuit low. Refer to Diagnostic Tables. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Testing and Inspection > Throttle Position (TP) Sensor > Page 3827 Throttle Position Sensor: Testing and Inspection Throttle Position Sensor Output This check should be performed when Throttle Position (TP) sensor attaching parts have been replaced. A scan tool can be used to read the TP signal output voltage. 1. Connect digital voltmeter J 39200 from TP sensor connector terminal B (BLk wire) to terminal C (DK Blue wire). Jumpers for terminal access can be made using terminals 1214836 and 12014837. 2. With ignition ON, engine stopped, the TP signal voltage should be less than 1.25V if more than 1.25V verify free throttle movement. If still more than 1.25V, replace TP sensor. 3. Remove the voltmeter and jumpers, reconnect the TP sensor connector to the sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Testing and Inspection > Page 3828 Throttle Position Sensor: Service and Repair Throttle Position Sensor Electrical Connector REMOVAL PROCEDURE CAUTION: The Throttle Position (TP) sensor is an electrical component. Do not soak the TP sensor in any liquid cleaner or solvent, as damage may result. 1. Remove the air cleaner and adapter. 2. Disconnect the electrical connector releasing locking tab. 3. Remove the two TP sensor attaching screw assemblies. 4. Remove the TP sensor from throttle body assembly. 5. Remove the TP sensor seal. INSTALLATION PROCEDURE 1. Install the TP sensor seal over throttle shaft. 2. With throttle valve closed, install the TP sensor on the throttle shaft. Rotate counterclockwise to align mounting holes. 3. Install the two TP sensor attaching screw assemblies. Tighten ^ Tighten the screw assemblies to 2.0 Nm (18.0 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Throttle Position Sensor > Component Information > Testing and Inspection > Page 3829 4. Connect the electrical connector. 5. Install the air cleaner and adapter. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Technical Service Bulletins > A/T - Park/Neutral Switch Connector Cannot Be Removed Transmission Position Switch/Sensor: Technical Service Bulletins A/T - Park/Neutral Switch Connector Cannot Be Removed File In Section: 7 - Transmission Bulletin No.: 83-71-10 Date: May, 1998 Subject: Park (Neutral Position Switch Connector Cannot be Removed (Replace Switch and Connectors) Models: 1997-98 Chevrolet Corvette 1995-98 Chevrolet and GMC S/T Models 1996-98 Chevrolet and GMC M/L, P Models 1996-99 Chevrolet and GMC C/K, G Models 1996-98 Oldsmobile Bravada Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer conditions, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to insure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to insure water-tight connections. Parts Information P/N Description 12450016 Switch 15305925 4-Way Connector Assembly 15305887 7-Way Connector Assembly Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 3836 Transmission Position Switch/Sensor: Locations Park/Neutral Position Switch Electronic 4-Speed Automatic Overdrive Transmission Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 3837 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions Transmission Position Switch/Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3840 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3841 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3842 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3843 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3844 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3845 Transmission Position Switch/Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3846 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3847 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3848 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3849 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3850 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3851 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3852 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3853 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3854 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3855 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3856 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3857 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3858 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3859 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3860 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3861 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3862 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3863 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3864 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3865 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3866 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3867 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3868 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3869 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3870 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3871 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3872 Transmission Position Switch/Sensor: Connector Views C1: Transmission Range Switch C2: Transmission Range Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3873 Transmission Position Switch/Sensor: Electrical Diagrams Electronic PRNDL Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 3874 Starter And Charging (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 3875 Transmission Position Switch/Sensor: Testing and Inspection Pressure Switch Assembly Resistance Check (1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 3876 Pressure Switch Assembly Resistance Check (2 Of 2) Tools Required - J 39775 4L60E Jumper Harness - J 39200 Digital Multimeter - J 35616 Connector Test Adapter Kit Important: Whenever the transmission 20-way connector is disconnected and the engine is running, multiple DTCs will set. Be sure to clear these codes when you are finished with this procedure Important: This procedure tests the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) circuits and the Automatic Transmission Fluid Temperature (TFT) Sensor circuit. Do not use this procedure to test other Automatic Transmission circuits, refer to 4L60-E Automatic Transmission Internal Wiring Harness check. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 3877 Transmission Position Switch/Sensor: Adjustments PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 3878 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 3879 Transmission Position Switch/Sensor: Service and Repair PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 3880 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations Vehicle Speed Sensor: Component Locations 5-Speed Manual Transmission 5-Speed Manual Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 3885 5-Speed Manual Transmission (MW3) 5-Speed Manual Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 3886 5-Speed Manual Transmission Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 3887 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 3888 Electronic 4-Speed Automatic Overdrive Transmission Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 3889 Vehicle Speed Sensor: Connector Locations 5-Speed Manual Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 3890 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions Vehicle Speed Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3893 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3894 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3895 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3896 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3897 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3898 Vehicle Speed Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3899 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3900 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3901 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3902 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3903 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3904 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3905 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3906 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3907 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3908 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3909 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3910 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3911 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3912 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3913 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3914 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3915 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3916 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3917 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3918 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3919 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3920 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3921 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3922 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3923 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3924 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Page 3925 Vehicle Speed Sensor: Description and Operation Vehicle Speed Sensor (2WD) DESCRIPTION The Vehicle Speed Sensor (VSS) is a pulse counter type input that informs the VCM how fast the vehicle is being driven. The VSS system uses an inductive sensor mounted in the tail housing of the transmission and a toothed reluctor wheel on the tail shaft. OPERATION As the reluctor rotates, the teeth alternately interfere with the magnetic field of the sensor creating an induced voltage pulse. The VSS produces an AC voltage signal that increases with vehicle speed. The VCM processes this signal and sends it to the following components: ^ Instrument Panel. ^ Cruise Control Module. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions Mass Air Flow (MAF) Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3931 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3932 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3933 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3934 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3935 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3936 Mass Air Flow (MAF) Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3937 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3938 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3939 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3940 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3941 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3942 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3943 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3944 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3945 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3946 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3947 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3948 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3949 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3950 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3951 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3952 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3953 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3954 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3955 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3956 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3957 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3958 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3959 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3960 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3961 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3962 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 3963 Mass Air Flow System Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Page 3964 Mass Air Flow (MAF) Sensor: Description and Operation Mass Air Flow (MAF) Sensor The Mass Air Flow (MAF) sensor measures the amount of air which passes through it. The VCM uses this information to determine the operating condition of the engine, to control fuel delivery. A large quantity of air indicates acceleration. A small quantity of air indicates deceleration or idle. The scan tool reads the MAF value and displays it in grams per second (gm/Sec). At idle, it should read between 5-7 gm/Sec on a fully warmed up engine. Values should change rather quickly on acceleration, but values should remain fairly stable at any given RPM. When the VCM detects a malfunction in the MAF sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0101 system performance. ^ DTC P0102 frequency low. ^ DTC P0103 frequency high. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Page 3965 Mass Air Flow (MAF) Sensor: Service and Repair MAF Sensor MAF Sensor Intake Duct REMOVAL PROCEDURE CAUTION: Take care when handling the Mass Air Flow (MAF). Do Not dent, puncture, or otherwise damage the honeywell located at the air inlet end of the MAF. Do Not touch the sensing elements or allow anything (including solvents and lubricants) to come in contact with them. A small amount of GM lubricant (P/N 99855406) may be used on the air duct only to aid in installation. Do Not drop or roughly handle the MAF. 1. Disconnect the 3 wire electrical connector. 2. Loosen the clamp on the intake duct. 3. Carefully remove the MAF sensor. INSTALLATION PROCEDURE 1. Install the MAF sensor. 2. Install the intake ducts. 3. Tighten the clamp. 4. Connect the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Fuel Pump Oil Pressure Switch and Sender Engine View, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Fuel Pump Oil Pressure Switch and Sender > Page 3970 Oil Pressure Switch (For Fuel Pump): Locations Oil Pressure Switch and Sender LH side of Engine, rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Page 3971 Fuel Pump Oil Pressure Switch And Sender Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Page 3972 Oil Pressure Switch (For Fuel Pump): Service and Repair Oil Pressure Switch Electrical Connector Oil Pressure Switch REMOVAL PROCEDURE 1. Remove the electrical connector. 2. Remove the fuel pump and oil pressure indicator switch, using wrench J 35748 it required. INSTALLATION PROCEDURE 1. Install the fuel pump and oil pressure indicator switch. 2. Install the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Specifications Throttle Position Sensor: Specifications Screw assemblies ................................................................................................................................ .................................................. 2.0 Nm (18.0 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Specifications > Page 3976 Engine Side, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Throttle Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3979 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3980 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3981 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3982 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3983 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3984 Throttle Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3985 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3986 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3987 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3988 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3989 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3990 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3991 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3992 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3993 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3994 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3995 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3996 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3997 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3998 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 3999 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4000 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4001 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4002 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4003 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4004 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4005 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4006 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4007 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4008 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4009 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4010 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4011 TP Sensor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Page 4012 Throttle Position Sensor: Description and Operation Diagram The non-adjustable Throttle Position (TP) sensor is mounted on the throttle body assembly opposite the throttle lever. The TP sensor senses the throttle valve angle and relays that information to the VCM. Knowledge of throttle angle is one of the inputs needed by the VCM to generate the required injector control signals (pulses). For further information on replacement, refer to TP Sensor. See: Service and Repair Legend (1) Throttle Body Assembly. (2) IAC Valve Assembly 0-ring. (3) IAC Valve Assembly Attaching Screw. (4) Idle Air Control (IAC) Valve Assembly. (5) TP Sensor 0-ring (6) Throttle Position (TP) Sensor. (7) TP Sensor Attaching Screw. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Testing and Inspection > Throttle Position (TP) Sensor Throttle Position Sensor: Testing and Inspection Throttle Position (TP) Sensor When the VCM detects a malfunction with the Throttle Position (TP) sensor circuits, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0121 circuit performance ^ DTC P0122 circuit low. ^ DTC P0123 circuit high. ^ DTC P1121 intermittent circuit high. ^ DTC P1122 intermittent circuit low. Refer to Diagnostic Tables. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Testing and Inspection > Throttle Position (TP) Sensor > Page 4015 Throttle Position Sensor: Testing and Inspection Throttle Position Sensor Output This check should be performed when Throttle Position (TP) sensor attaching parts have been replaced. A scan tool can be used to read the TP signal output voltage. 1. Connect digital voltmeter J 39200 from TP sensor connector terminal B (BLk wire) to terminal C (DK Blue wire). Jumpers for terminal access can be made using terminals 1214836 and 12014837. 2. With ignition ON, engine stopped, the TP signal voltage should be less than 1.25V if more than 1.25V verify free throttle movement. If still more than 1.25V, replace TP sensor. 3. Remove the voltmeter and jumpers, reconnect the TP sensor connector to the sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Testing and Inspection > Page 4016 Throttle Position Sensor: Service and Repair Throttle Position Sensor Electrical Connector REMOVAL PROCEDURE CAUTION: The Throttle Position (TP) sensor is an electrical component. Do not soak the TP sensor in any liquid cleaner or solvent, as damage may result. 1. Remove the air cleaner and adapter. 2. Disconnect the electrical connector releasing locking tab. 3. Remove the two TP sensor attaching screw assemblies. 4. Remove the TP sensor from throttle body assembly. 5. Remove the TP sensor seal. INSTALLATION PROCEDURE 1. Install the TP sensor seal over throttle shaft. 2. With throttle valve closed, install the TP sensor on the throttle shaft. Rotate counterclockwise to align mounting holes. 3. Install the two TP sensor attaching screw assemblies. Tighten ^ Tighten the screw assemblies to 2.0 Nm (18.0 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Testing and Inspection > Page 4017 4. Connect the electrical connector. 5. Install the air cleaner and adapter. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Camshaft Position Sensor: Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4023 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4024 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4025 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4026 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4027 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4028 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4029 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Page 4030 Camshaft Position Sensor: Specifications Camshaft position sensor retaining screw ........................................................................................................................................... 4-6 Nm (35-53 lb. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Page 4031 Engine View, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Camshaft Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4034 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4035 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4036 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4037 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4038 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4039 Camshaft Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4040 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4041 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4042 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4043 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4044 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4045 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4046 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4047 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4048 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4049 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4050 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4051 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4052 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4053 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4054 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4055 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4056 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4057 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4058 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4059 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4060 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4061 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4062 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4063 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4064 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4065 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Page 4066 Camshaft Position Sensor: Description and Operation Camshaft Position Sensor The Camshaft Position (CMP) sensor is located within the distributor. It's operation is very similar to the Crankshaft Position (CKP) sensor however it will provide one pulse per camshaft revolution (1x signal). This signal is not detrimental to the driveability of the vehicle. The Vehicle Control Module (VCM) utilizes this signal in conjunction with the crankshaft position to determine which cylinder(s) are misfiring. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Testing and Inspection > Cam Signal Camshaft Position Sensor: Testing and Inspection Cam Signal The VCM uses this signal to determine the position of the #1 piston during its power stroke. This signal is used by the VCM to calculate fuel injection mode of operation. A loss of this signal will set DTC P0340. If the cam signal is lost while the engine is running, the fuel injection system will shift to a calculated fuel injection mode based on the last fuel injection pulse, and the engine will continue to run. The engine can be restarted and will run in the calculated mode as long as the fault is present Refer to Diagnostic Trouble Code (DTC) P0340 Camshaft Position Sensor (CKP) Sensor Circuit. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Testing and Inspection > Page 4069 Camshaft Position Sensor: Service and Repair REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Disconnect the electrical connector from the camshaft position sensor. 3. Remove the camshaft position sensor retaining screw. 4. Remove the camshaft position sensor. INSTALLATION PROCEDURE 1. Install the camshaft position sensor. 2. Install the camshaft position sensor retaining screw, torque to 4-6 Nm (35-53 lb. in.). 3. Connect the electrical connector. 4. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-014 > Apr > 00 > Engine - No/Hard/Slow Start/Backfire/Kickback Crankshaft Position Sensor: Customer Interest Engine - No/Hard/Slow Start/Backfire/Kickback File In Section: 06 - Engine/Propulsion System Bulletin No.: 00-06-04-014 Date: April, 2000 TECHNICAL Subject: No, Hard, or Slow Start, Backfire or "Kickback" During Crank/Start, "Grinding" or Unusual Noises During Crank, DTC P0338 (Replace Crankshaft Position Sensor) Models: 1999-2000 Cadillac Escalade 1995-2000 Chevrolet and GMC SIT Models 1996-2000 Chevrolet and GMC C/K, M/L, G, P Models 1996-2000 Oldsmobile Bravada with 4.3 L, 5.0 L, 5.7 L or 7.4 L Engine (VINs W, X, M, R, J RPOs L35, LF6, L30, L31, L29) Condition: Some customers may comment on one or more of the following conditions: ^ Backfire during crank/start ^ "Kickback" during crank/start ^ "No" start ^ "Slow" or "hard" start/crank ^ "Grinding" or unusual noises during crank/start ^ Cracked or broken engine block at the starter boss ^ Broken starter drive housing ^ Broken starter ring gear on flywheel ^ Any combination of the above Cause: A condition may exist that allows the crankshaft position sensor to command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss. Correction: Inspect for a stored powertrain DTC code P0338. This DTC will NOT illuminate the "Service Engine Soon" light. If this code is stored, the Crankshaft Position Sensor, P/N 10456607, MUST be replaced and the remaining components inspected for damage (engine block at the starter boss, the starter drive housing, and the engine flywheel starter ring gear). Notice: When DTC code P0338 is set, failure to replace the Crankshaft Position Sensor could result in repeated inoperative conditions of the starter or flywheel. Important: Some flywheel wear is normal; broken or missing teeth and/or cracks, are not normal. Parts Information Parts are currently available from GMSPO. Warranty Information: For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 00-06-04-014 > Apr > 00 > Engine - No/Hard/Slow Start/Backfire/Kickback Crankshaft Position Sensor: All Technical Service Bulletins Engine - No/Hard/Slow Start/Backfire/Kickback File In Section: 06 - Engine/Propulsion System Bulletin No.: 00-06-04-014 Date: April, 2000 TECHNICAL Subject: No, Hard, or Slow Start, Backfire or "Kickback" During Crank/Start, "Grinding" or Unusual Noises During Crank, DTC P0338 (Replace Crankshaft Position Sensor) Models: 1999-2000 Cadillac Escalade 1995-2000 Chevrolet and GMC SIT Models 1996-2000 Chevrolet and GMC C/K, M/L, G, P Models 1996-2000 Oldsmobile Bravada with 4.3 L, 5.0 L, 5.7 L or 7.4 L Engine (VINs W, X, M, R, J RPOs L35, LF6, L30, L31, L29) Condition: Some customers may comment on one or more of the following conditions: ^ Backfire during crank/start ^ "Kickback" during crank/start ^ "No" start ^ "Slow" or "hard" start/crank ^ "Grinding" or unusual noises during crank/start ^ Cracked or broken engine block at the starter boss ^ Broken starter drive housing ^ Broken starter ring gear on flywheel ^ Any combination of the above Cause: A condition may exist that allows the crankshaft position sensor to command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss. Correction: Inspect for a stored powertrain DTC code P0338. This DTC will NOT illuminate the "Service Engine Soon" light. If this code is stored, the Crankshaft Position Sensor, P/N 10456607, MUST be replaced and the remaining components inspected for damage (engine block at the starter boss, the starter drive housing, and the engine flywheel starter ring gear). Notice: When DTC code P0338 is set, failure to replace the Crankshaft Position Sensor could result in repeated inoperative conditions of the starter or flywheel. Important: Some flywheel wear is normal; broken or missing teeth and/or cracks, are not normal. Parts Information Parts are currently available from GMSPO. Warranty Information: For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Crankshaft Position Sensor: All Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4087 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4088 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4089 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4090 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4091 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4092 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4093 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Crankshaft Position Sensor: All Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4099 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4100 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4101 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4102 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4103 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4104 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4105 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Page 4106 Crankshaft Position Sensor: Specifications Crankshaft Position Sensor mounting bolts ................................................................................................................................................. 8 Nm (71 lb. In.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Page 4107 Engine Side, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Crankshaft Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4110 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4111 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4112 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4113 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4114 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4115 Crankshaft Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4116 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4117 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4118 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4119 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4120 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4121 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4122 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4123 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4124 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4125 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4126 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4127 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4128 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4129 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4130 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4131 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4132 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4133 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4134 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4135 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4136 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4137 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4138 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4139 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4140 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4141 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Page 4142 Crankshaft Position Sensor: Description and Operation DESCRIPTION The Crankshaft Position (CKP) Sensor is located in the front engine cover and is perpendicular to the crankshaft target wheel. The air gap between the sensor and the wheel is preset and not adjustable. The target wheel has three slots 60° apart and is keyed to the crankshaft. As the target wheel rotates, the slots passing by the sensor create a change in the magnetic field of the sensor which results in an induced voltage pulse. One revolution of the crankshaft results in three pulses (3x signal). Based on these pulses, the VCM is able to determine crankshaft position and engine speed. The VCM then activates the fuel injector and provides a spark to the Distributor. The relation between the crankshaft position sensor and the target wheel is crucial. The sensor must be exactly perpendicular to the target wheel with the correct air gap. OPERATION The crankshaft position sensor provides the VCM with crankshaft speed and crankshaft position. The VCM utilizes this information to determine if an engine Misfire is present. The VCM monitors the Crankshaft Position Sensor (CKP) sensor for momentarily drop in crankshaft speed to determine if a misfire is occurring. When the VCM detects a misfire, a Diagnostic Trouble Code (DTC) P0300 will set. The VCM also monitors the CKP sensor signal circuit for malfunctions. The VCM monitors CKP signal and the High and Low resolution signals. The VCM calculates these signals to determine a ratio. When the VCM detects that the ratio is out of normal operating range, the VCM will set a Diagnostic Trouble Code (DTC) P0337 or a DTC P0338. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Page 4143 Crankshaft Position Sensor: Service and Repair REMOVAL PROCEDURE 1. Remove the electrical connector. 2. Remove the sensor hold down bolt. 3. Remove the sensor from the timing cover. NOTE: When installing or removing a crankshaft position (CKP) sensor make sure the sensor is fully seated and held stationary in the front cover before torquing the hold down bolt into the front cover. A sensor which is not seated may result in erratic operation and lead to the setting of false codes. 4. Inspect the sensor O-ring for wear, cracks or leakage. Replace if necessary. Lube the new O-ring with clean engine oil before installing. INSTALLATION PROCEDURE NOTE: Make certain that the Crankshaft Position (CKP) sensor mounting surfaces are clean and free of burrs before installing the CKP sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Page 4144 1. Install the sensor into the timing cover. 2. Install the sensor hold down bolt. Tighten ^ Tighten the hold down bolt to 8 Nm (71 lb. in.). 3. Install the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Hall Effect Sensor, Ignition > Component Information > Description and Operation Hall Effect Sensor: Description and Operation Description The hall effect switch connects to the VCM through the primary engine harness and provides cylinder identification information. The hall effect switch is located under the distributor cap. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder Technical Service Bulletin # 73-01-09 Date: 971001 Starting - Revised Procedures for Inop Ignition Cylinder File In Section: 0 - General Information Bulletin No.: 73-01-09 Date: October, 1997 INFORMATION Subject: New Tumblers for Cylinder Recoding, Revised Repair Procedures for Inoperative Ignition Cylinders (Seized/Won't Rotate), Labor Operation/Time Allowances Models: 1995-97 Buick Skylark, Riviera 1995-97 Chevrolet Cavalier 1997 Chevrolet Corvette, Malibu, Venture 1995-97 Oldsmobile Achieva 1997 Oldsmobile Aurora, Cutlass, Silhouette 1995-97 Pontiac Grand Am, Sunfire 1997 Pontiac Grand Prix, Trans Sport 1995-97 Chevrolet and GMC C/K, S/T Models 1996-97 Chevrolet and GMC G, M/L Vans 1996-97 Oldsmobile Bravada The information in this bulletin concerns new designed tumblers for recoding lock cylinders that use double sided reversible keys, revised procedures for servicing ignition lock cylinders that are seized or not able to rotate and revised labor time guide information and allowances. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 4157 The existing labor operation (E7200) has been changed to include "Add" conditions for cylinders that will not rotate. New Tumblers New tumblers are available from GMSPO for recoding lock cylinders that use double-sided reversible keys. These new tumblers should be used immediately and information about the disposition of original tumblers will be provided by GMSPO. Figure 1 shows the new tumbler profile. The shaded area was part of the original tumbler profile, and is removed on the new tumblers. The new part numbers for the tumblers are as follows: Part No. 2852732 = Tumbler # 1 Part No. 2852733 = Tumbler # 2 Part No. 2852734 = Tumbler # 3 Part No. 2852735 = Tumbler # 4 Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. New Procedures For Seized/Won't Rotate Column Mounted Ign. CYL. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 4158 A. On G, J and N Models: DO NOT REMOVE THE STEERING COLUMN as indicated in the Service Manual procedure. 1. Remove the tilt lever, upper and lower column covers. 2. Drill hole in module housing as indicated in the illustration using a short drill bit (1/8" followed by 9/32") and 90 degree drill motor or go degree drill attachment to break or access the retaining spring for the lock cylinder button, see Figure 2. 3. Using a pick or needle nose pliers, remove the retaining spring from the hole. 4. Using pliers, grasp and remove the retaining button for the cylinder. 5. Remove the cylinder from the housing. 6. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 7. Install the new cylinder and reinstall the steering column components. B. On U, W, and light duty trucks, follow the Service Manual procedure for keys missing, or cylinders won't rotate. Procedure: Instrument Panel Mounted Switches Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 4159 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder Technical Service Bulletin # 73-01-09 Date: 971001 Starting - Revised Procedures for Inop Ignition Cylinder File In Section: 0 - General Information Bulletin No.: 73-01-09 Date: October, 1997 INFORMATION Subject: New Tumblers for Cylinder Recoding, Revised Repair Procedures for Inoperative Ignition Cylinders (Seized/Won't Rotate), Labor Operation/Time Allowances Models: 1995-97 Buick Skylark, Riviera 1995-97 Chevrolet Cavalier 1997 Chevrolet Corvette, Malibu, Venture 1995-97 Oldsmobile Achieva 1997 Oldsmobile Aurora, Cutlass, Silhouette 1995-97 Pontiac Grand Am, Sunfire 1997 Pontiac Grand Prix, Trans Sport 1995-97 Chevrolet and GMC C/K, S/T Models 1996-97 Chevrolet and GMC G, M/L Vans 1996-97 Oldsmobile Bravada The information in this bulletin concerns new designed tumblers for recoding lock cylinders that use double sided reversible keys, revised procedures for servicing ignition lock cylinders that are seized or not able to rotate and revised labor time guide information and allowances. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 4165 The existing labor operation (E7200) has been changed to include "Add" conditions for cylinders that will not rotate. New Tumblers New tumblers are available from GMSPO for recoding lock cylinders that use double-sided reversible keys. These new tumblers should be used immediately and information about the disposition of original tumblers will be provided by GMSPO. Figure 1 shows the new tumbler profile. The shaded area was part of the original tumbler profile, and is removed on the new tumblers. The new part numbers for the tumblers are as follows: Part No. 2852732 = Tumbler # 1 Part No. 2852733 = Tumbler # 2 Part No. 2852734 = Tumbler # 3 Part No. 2852735 = Tumbler # 4 Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. New Procedures For Seized/Won't Rotate Column Mounted Ign. CYL. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 4166 A. On G, J and N Models: DO NOT REMOVE THE STEERING COLUMN as indicated in the Service Manual procedure. 1. Remove the tilt lever, upper and lower column covers. 2. Drill hole in module housing as indicated in the illustration using a short drill bit (1/8" followed by 9/32") and 90 degree drill motor or go degree drill attachment to break or access the retaining spring for the lock cylinder button, see Figure 2. 3. Using a pick or needle nose pliers, remove the retaining spring from the hole. 4. Using pliers, grasp and remove the retaining button for the cylinder. 5. Remove the cylinder from the housing. 6. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 7. Install the new cylinder and reinstall the steering column components. B. On U, W, and light duty trucks, follow the Service Manual procedure for keys missing, or cylinders won't rotate. Procedure: Instrument Panel Mounted Switches Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 4167 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Page 4168 Ignition Switch Lock Cylinder: Service and Repair The procedure has been updated by TSB# 73-01-09 Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Specifications Knock Sensor: Specifications Knock sensor ....................................................................................................................................... ....................................................... 19 Nm (14 lb. ft.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Specifications > Page 4172 Knock Sensor: Locations Engine View, Rear LH side of Engine Block, below Exhaust Manifold, forward of Starter Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions Knock Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4175 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4176 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4177 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4178 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4179 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4180 Knock Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4181 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4182 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4183 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4184 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4185 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4186 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4187 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4188 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4189 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4190 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4191 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4192 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4193 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4194 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4195 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4196 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4197 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4198 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4199 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4200 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4201 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4202 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4203 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4204 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4205 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4206 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4207 Knock Sensor Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Page 4208 Knock Sensor: Description and Operation Description The Knock Sensor (KS) system is used to detect engine detonation The VCM will retard the spark timing based on the signals from the KS module. The Knock Sensor(s) produce an AC voltage that is sent to the KS module. The amount of AC voltage produced is proportional to the amount of knock. Operation An operating engine produces a normal amount of engine mechanical vibration (Noise). The knock sensor(s) will produce an AC voltage signal from this Noise. When an engine is operating, the VCM will learn the minimum and maximum frequency of the noise the engine produces. When the VCM determines that this frequency is less than or greater than the expected amount, a knock sensor DTC will set. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Sensors and Switches - Powertrain Management > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Page 4209 Knock Sensor: Service and Repair Diagram Removal Procedure NOTE: The knock sensor is located in areas of the cylinder head. On most applications, the knock sensors are installed in a hole which is exposed to engine coolant. Care should be exercised when servicing these sensors. 1. Disconnect the negative battery cable. Important: On knock sensors which are mounted in the end of the cylinder head draining the cooling system will not be necessary. 2. Drain the cooling system. Refer to Draining and Filling Cooling System. 3. Remove the wiring harness connector from knock sensor. 4. Remove the knock sensor from cylinder head. Installation Procedure Important: Do not use silicon tape as this will insulate the sensor from the engine block. 2. After applying a water base caulk to the sensor threads, install the knock sensor into the cylinder head. Tighten ^ Tighten to 19 Nm (14 lb. ft.). 2. Connect the negative battery cable. 3. Refill cooling system if required. Refer to Draining and Filling Cooling System. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Fuel Pressure > Diagnostic Connector - Fuel Pump > Component Information > Locations Diagnostic Connector - Fuel Pump: Locations For Fuel Pump Prime and Run Connector, See Computer and Control Systems, Data Link Connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Idle Speed > System Information > Specifications > Controlled Idle Speed Idle Speed: Specifications Controlled Idle Speed Under 8500 GVW Transmission Gear Idle Speed IAC Counts [1] OPEN/CLOSED Loop [2] Manual N 675 +/- 25 Varies CL Automatic D 550 +/- 25 Varies CL [1] On manual transmission vehicles the SCAN tool will display RDL in Neutral. Add 2 counts for engines with less than 500 miles. Add 2 counts for every 1000 ft. above sea level. [2] Let engine idle until proper fuel control status is reached (OPEN/CLOSED loop). Note: Engine should be at operating temperature 92°C to 104° (196°F to 222°F). Over 8500 GVW Transmission Gear Idle Speed IAC Counts [1] OPEN/CLOSED Loop [2] Manual N 675 +/- 25 Varies CL Automatic D 550 +/- 25 Varies CL [1] On manual transmission vehicles the SCAN tool will display RDL in Neutral. Add 2 counts for engines with less than 500 miles. Add 2 counts for every 1000 ft. above sea level. [2] Let engine idle until proper fuel control status is reached (OPEN/CLOSED loop). Note: Engine should be at operating temperature 92°C to 104° (196°F to 222°F). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Idle Speed > System Information > Adjustments > Controlled Idle Speed Idle Speed: Adjustments Controlled Idle Speed NOTE: There should be no Diagnostic Trouble Code (DTC)s displayed. The idle air control system has been checked. 1. Set the parking brake. 2. Block the drive wheels. 3. Connect a scan tool to the Data Link Connector (DLC) connector with the tool in the open mode. 4. Start the engine. 5. Bring the engine to the normal operating temperature. 6. Check for the correct state of the Transmission Range (TR) switch position on the scan tool. 7. Check the specifications for controlled idle speed and Idle Air Control (IAC) valve pintle position (counts). Refer to Idle Air Control Valve / Service and Repair. See: Computers and Control Systems/Idle Air Control (IAC) Valve/Service and Repair 8. If within specifications, the idle speed is being correctly controlled by the control module. 9. If not within specifications, refer to Driveability Symptoms. Refer to System Diagnosis for testing information. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Cleaner Fresh Air Duct/Hose > Component Information > Specifications Air Cleaner Fresh Air Duct/Hose: Specifications Air intake duct screw ........................................................................................................................... ........................................................ 2 Nm (18 lb. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Cleaner Fresh Air Duct/Hose > Component Information > Specifications > Page 4225 Air Cleaner Fresh Air Duct/Hose: Service and Repair Air Intake Duct Retainer Bolt Air Intake Duct Removal Procedure 1. Remove the retainer. 2. Remove the screw. 3. Remove the air intake duct Installation Procedure 1. Install the air intake duct. 2. Install the screw. Tighten Tighten the screw 2 Nm (18 lb. in.). 3. Install the retainer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Customer Interest for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T - Shift/Driveability Concerns/MIL ON Air Filter Element: Customer Interest Engine, A/T - Shift/Driveability Concerns/MIL ON Bulletin No.: 04-07-30-013B Date: February 01, 2007 INFORMATION Subject: Automatic Transmission Shift, Engine Driveability Concerns or Service Engine Soon (SES) Light On as a Result of the Use of an Excessively/Over-Oiled Aftermarket, Reusable Air Filter Models: 2007 and Prior GM Cars and Light Duty Trucks 2007 and Prior Saturn Models 2003-2007 HUMMER H2 2006-2007 HUMMER H3 2005-2007 Saab 9-7X Supercede: This bulletin is being revised to add models and model years. Please discard Corporate Bulletin Number 04-07-30-013A (Section 07 - Transmission/Transaxle). The use of an excessively/over-oiled aftermarket, reusable air filter may result in: Service Engine Soon (SES) light on Transmission shift concerns, slipping and damaged clutch(es) or band(s) Engine driveability concerns, poor acceleration from a stop, limited engine RPM range The oil that is used on these air filter elements may be transferred onto the Mass Air Flow (MAF) sensor causing contamination of the sensor. As a result, the Grams per Second (GPS) signal from the MAF may be low and any or all of the concerns listed above may occur. When servicing a vehicle with any of these concerns, be sure to check for the presence of an aftermarket reusable, excessively/over-oiled air filter. The MAF, GPS reading should be compared to a like vehicle with an OEM air box and filter under the same driving conditions to verify the concern. The use of an aftermarket reusable air filter DOES NOT void the vehicle's warranty. If an aftermarket reusable air filter is used, technicians should inspect the MAF sensor element and the air induction hose for contamination of oil prior to making warranty repairs. Transmission or engine driveability concerns (related to the MAF sensor being contaminated with oil) that are the result of the use of an aftermarket reusable, excessively/over-oiled air filter are not considered to be warrantable repair items. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Customer Interest for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T - Shift/Driveability Concerns/MIL ON > Page 4234 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T - Shift/Driveability Concerns/MIL ON Air Filter Element: All Technical Service Bulletins Engine, A/T - Shift/Driveability Concerns/MIL ON Bulletin No.: 04-07-30-013B Date: February 01, 2007 INFORMATION Subject: Automatic Transmission Shift, Engine Driveability Concerns or Service Engine Soon (SES) Light On as a Result of the Use of an Excessively/Over-Oiled Aftermarket, Reusable Air Filter Models: 2007 and Prior GM Cars and Light Duty Trucks 2007 and Prior Saturn Models 2003-2007 HUMMER H2 2006-2007 HUMMER H3 2005-2007 Saab 9-7X Supercede: This bulletin is being revised to add models and model years. Please discard Corporate Bulletin Number 04-07-30-013A (Section 07 - Transmission/Transaxle). The use of an excessively/over-oiled aftermarket, reusable air filter may result in: Service Engine Soon (SES) light on Transmission shift concerns, slipping and damaged clutch(es) or band(s) Engine driveability concerns, poor acceleration from a stop, limited engine RPM range The oil that is used on these air filter elements may be transferred onto the Mass Air Flow (MAF) sensor causing contamination of the sensor. As a result, the Grams per Second (GPS) signal from the MAF may be low and any or all of the concerns listed above may occur. When servicing a vehicle with any of these concerns, be sure to check for the presence of an aftermarket reusable, excessively/over-oiled air filter. The MAF, GPS reading should be compared to a like vehicle with an OEM air box and filter under the same driving conditions to verify the concern. The use of an aftermarket reusable air filter DOES NOT void the vehicle's warranty. If an aftermarket reusable air filter is used, technicians should inspect the MAF sensor element and the air induction hose for contamination of oil prior to making warranty repairs. Transmission or engine driveability concerns (related to the MAF sensor being contaminated with oil) that are the result of the use of an aftermarket reusable, excessively/over-oiled air filter are not considered to be warrantable repair items. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T - Shift/Driveability Concerns/MIL ON > Page 4240 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Page 4241 Air Filter Element: Testing and Inspection The air cleaner restriction indicator is located on the intake duct between the air cleaner assembly and the Mass Air Flow (MAF) sensor. If the area inside of the clear section is green, no air filter service is required. If the area inside the clear section is orange and Change Air Filter appears, replace the air filter. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Page 4242 Air Filter Element: Service and Repair Air Cleaner Element Holddown REMOVAL PROCEDURE 1. Disconnect the hold down clips. 2. Remove the air cleaner cover. 3. Remove the filter. Hold the duct and remove the filter by pulling and twisting the filter away from the duct. 4. Clean the air cleaner housing. INSTALLATION PROCEDURE 1. Install the filter. - Install the new filter by pushing it all the way to the stops of the duct. - Install the duct and filter in the air cleaner housing. Make sure that the duct fits properly into the housing. 2. Install the air cleaner cover. 3. Connect the hold down clips. 4. Push the button on the top of the indicator to reset it to the green (Clean) filter zone. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Fuel Filter > Fuel Pressure Release > System Information > Service and Repair Fuel Pressure Release: Service and Repair TOOLS REQUIRED - J 34730 Fuel Pressure Gauge WARNING: Relieve the fuel system pressure before servicing fuel system components In order to reduce the risk of fire and personal Injury. After relieving the system pressure, a small amount of fuel may be released when servicing the fuel lines or connections. In order to reduce the chance of personal Injury, cover the regulator and the fuel line fittings with a shop towel before disconnecting. This will catch any fuel that may leak out. Place the towel In an approved container when the disconnection Is complete. 1. Disconnect the negative battery cable in order to avoid possible fuel discharge if an accidental attempt is made to start the engine. 2. Loosen the fuel filler cap in order to relieve the tank vapor pressure. 3. Connect the gauge J 34730-1A or the equivalent to the fuel pressure connection. 4. Wrap a shop towel around the fitting while connecting the gauge in order to avoid spillage. 5. Install the bleed hose into an approved container and open valve in order to bleed the system pressure. The fuel connections are now safe for servicing. 6. Drain any fuel remaining in gauge into an approved container. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Firing Order > Component Information > Specifications > Ignition Firing Order Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Ignition Timing > Number One Cylinder > Component Information > Locations > Number 1 Cylinder Location Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Ignition Timing > Timing Marks and Indicators > System Information > Locations > Crankshaft Rotation Timing Marks and Indicators: Locations Crankshaft Rotation Crankshaft Rotation (Typical Crankshaft Pulley) Crankshaft rotation is clockwise when viewed from in front of the crankshaft pulley as shown in the generic image. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Ignition Timing > Timing Marks and Indicators > System Information > Locations > Crankshaft Rotation > Page 4260 Timing Marks and Indicators: Locations Timing Marks The ignition timing is completely controlled by the Vehicle Control Module (VCM). No timing reference marks are provided. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications Spark Plug Wire: Specifications 0-15 inch cable .................................................................................................................................... .................................................. 3,000 - 10,000 ohms. 15-25 inch cable .................................................................................................................................. .................................................. 4,000 - 15,000 ohms. 25-35 inch cable .................................................................................................................................. .................................................. 6,000 - 20,000 ohms. Longer wires should measure about 5,000 to 10,000 ohms per foot. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 4264 Spark Plug Wire: Locations Spark Plug Wire Routing Right Side Spark Plug Wire Routing Left Side Wire routings must be kept intact during service and followed exactly when wires have been disconnected or when replacement of the wires is necessary. Failure to route the wires properly can lead to radio ignition noise and crossfiring of the plugs or shorting of the leads to ground Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 4265 Spark Plug Wire: Service Precautions Service Precautions 1. Twist boots one-half turn before removing. 2. When removing the boot, do not use pliers or other tools that could tear the boot. 3. Do not force anything between the wire and the boot, or through the silicone jacket of the wiring. 4. Do not pull on the wires to remove the boot. Pull on the boot or use a tool designed for this purpose. 5. Special care should be used when installing spark plug boots to ensure the metal terminal within the boot is fully seated on the spark plug terminal and the boot has not moved on the wire. NOTE: If boot to wire movement has occurred, the boot will give a false visual impression of being fully seated. Make sure that boots have been properly assembled by pushing sideways on the in stalled boots. Failure to properly seat the terminal onto the spark plug will lead to wire core erosion and result in an engine misfire or crossfire condition, and possible internal damage to the engine. ^ If they have been correctly installed, a stiff boot with only slight looseness will be noted. If the terminal has not been properly seated on the spark plug, only the resistance of the boot will be felt when pushing sideways. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 4266 Spark Plug Wire: Testing and Inspection VISUAL INSPECTION 1. Inspect the routing of the wires. Improper routing can cause crossfiring. 2. Inspect each wire for any signs of cracks or splits in the wire. 3. Inspect each boot for signs of tears, piercing, arc through, or carbon tracking. If the boot needs to be replaced, twist it a half-turn in either direction to break the seal before pulling on the boot to remove the wire. SPARK PLUG WIRE RESISTANCE TEST 1. Disconnect both ends of each wire. Make sure the wire terminals are clean. 2. Set ohmmeter on the high scale and connect it to each end of the wire being tested. Twist the wire gently while watching ohmmeter. 3. If ohmmeter reads above 30,000 ohms (no matter how long the wire is), or fluctuates from infinity any value, replace the wire. 4. If the resistance of any wire is not within the following ranges, replace the wire being tested. - 0 to 381 mm (0 to 15 in.) wire - 3,000 to 10,000 ohms. - 381 mm to 635 mm (15 in. to 25 in.) wire - 4,000 to 15,000 ohms. - 635 mm to 889 mm (25 in. to 35 in.) wire - 6,000 to 20,000 ohms. - Longer wire - should measure about 5,000 to 10,000 ohms per foot. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 4267 Spark Plug Wire: Service and Repair Spark Plug Wire Routing Right Side Spark Plug Wire Routing Left Side SERVICE CAUTIONS 1. Twist boots one-half turn before removing. 2. When removing the boot, do not use pliers or other tools that could tear the boot. 3. Do not force anything between the wire and the boot, or through the silicone jacket of the wiring. 4. Do not pull on the wires to remove the boot. Pull on the boot or use a tool designed for this purpose. 5. Special care should be used when installing spark plug boots to ensure the metal terminal within the boot is fully seated on the spark plug terminal and the boot has not moved on the wire. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 4268 WARNING: If boot to wire movement has occurred, the boot will give a false visual impression of being seated. Make sure that boots have been properly assembled by pushing sideways on the installed boots. Failure to properly seat the terminal onto the spark plug will lead to wire core erosion and result in an engine misfire or crossfire condition, and possible internal damage to the engine. ^ If they have been correctly installed, a stiff boot with only slight looseness will be noted. If the terminal has not been properly seated on the spark plug, only the resistance of the boot will be felt when pushing sideways. SPARK PLUG WIRE REPLACEMENT Spark plug wire routings must be kept intact during service and followed exactly when spark plug wires have been disconnected or when replacement of the spark plug wires is necessary. Failure to route the spark plug wires properly can lead to radio noise and crossfiring of the spark plugs, or shorting of the leads to ground. The correct routing is shown in the images. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Ignition System - Distributor Is Now Repairable Distributor: Technical Service Bulletins Ignition System - Distributor Is Now Repairable CHEVROLET 71-65-40 Issued: 05/01/97 SMU - SECTION 6E - REVISED ENHANCED IGNITION SYSTEM DESCRIPTION AND OPERATION SUBJECT: SERVICE MANUAL UPDATE - SECTION 6E - ENGINE CONTROLS REVISED ENHANCED IGNITION SYSTEM DESCRIPTION AND OPERATION MODELS: 1995-97 CHEVROLET AND GMC S/T, M/L, C/K, GMT600, P MODELS 1996-97 OLDSMOBILE BRAVADA WITH 4.3L, 5.0L, 5.7L, 7.4L ENGINE (VINS W, M, R, J - RPOS L35, L30, L31, L29) THIS BULLETIN IS BEING ISSUED TO INFORM TECHNICIANS OF A REVISION TO THE ENHANCED IGNITION SYSTEM DESCRIPTION AND OPERATION. THE DISTRIBUTOR IS NOW REPAIRABLE. TECHNICIANS WILL BE REFERRED TO DISTRIBUTOR OVERHAUL IN ENGINE ELECTRICAL FOR PROPER REPAIR AND REPLACEMENT OF ALL COMPONENTS. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Ignition System - Distributor Is Now Repairable > Page 4273 Distributor: Technical Service Bulletins Ignition - Distributor Service Kits Now Available File In Section: 6 - Engine Bulletin No.: 77-64-04 Date: April, 1997 SERVICE MANUAL UPDATE Subject: Distributor Service Kits Models: 1995 Chevrolet and GMC S/T Utility Models with 4.3L OBDII Engines ONLY (VIN W - RPO L35) 1996 Chevrolet and GMC C/K, M/L, S/T; P, G 1996 Oldsmobile Bravada 1997 Chevrolet and GMC C/K, M/L, S/T; P, G 1997 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L, 7.4L Engines (VINs W, X, M, R, J - RPOs L35, LF6, L3O, L31, L29) Service kits are now available to field service Distributor Assemblies. Important: Fastening screws have pre-applied thread locking adhesive and should be discarded after removal. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Ignition System - Distributor Is Now Repairable > Page 4274 1995 4.3L L35 OBDII Distributor Assemblies are now serviced with 1996 Distributor Assemblies (P/N 1104050). Installation instructions are included with each replacement assembly and must be followed. The following Service Kits are now available: Important: Removed fasteners are not to be re-used. Always use the new fasteners supplied in each kit. Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Ignition System - Distributor Is Now Repairable > Page 4275 Warranty Information For Vehicles repaired under warranty use the table shown. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Page 4276 Distributor: Specifications Distributor clamp and bolt .................................................................................................................... .................................................. 27 N.m (20 lbs. ft.) Distributor cap screws ........................................ ....................................................................................................................... 4.5-5.0 N.m (40-45 lbs. in.) Distributor rotor .................................................................................................................................... ................................................... 2 N.m (20 lbs. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Page 4277 Distributor: Locations Top of Engine, at rear, near Bulkhead Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Technical Service Bulletins > Page 4278 Distributor: Application and ID The part number is pin stamped into the plastic base (directly below the high tension terminals and next to the three pin camshaft sensor connection.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Description and Operation > Distributor Operation Distributor: Description and Operation Distributor Operation DISTRIBUTORS Distributor This ignition system includes the distributor, hall effect switch, ignition coil, secondary wires, spark plugs, knock sensor and crankshaft position sensor. The ignition system is controlled by the vehicle control module (VCM). The VCM monitors information from various engine sensors, computes the desired spark timing and controls the dwell and firing of the ignition coil via an ignition control line to the coil driver. The distributor connects the ignition coil and spark plugs through secondary wires. The rotor directs the spark to the appropriate cylinder. The distributor has a hall effect switch that connects to the VCM through the primary engine harness and provides cylinder identification information. Identification The part number is pin stamped into the plastic base (directly below the high tension terminals and next to the three pin camshaft sensor connection.) Ignition Coil The coil driver controls the current flow in the primary winding of the ignition coil when signaled by the VCM. The interconnects are made by the primary engine harness. The ignition coil can generate up to 35,000 volts and connects to the distributor through a secondary wire. Secondary Wires The secondary wires carry voltage between the ignition coil, distributor, and spark plugs. The secondary wire connections form a tight seal that prevents voltage arching. Hall Effect Switch The hall effect switch connects to the VCM through the primary engine harness and provides cylinder identification information. The hall effect switch is located under the distributor cap. Crankshaft Position Sensor The crankshaft position sensor connects to the VCM through the primary engine harness and provides crank- shaft reference information to the VCM for spark and fuel delivery. The crankshaft position sensor is located in the front cover behind the crankshaft balancer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Description and Operation > Distributor Operation > Page 4281 Distributor: Description and Operation General Description Distributor The distributor is actually an assembly that contains the Camshaft Position (CMP) sensor, cap, rotor and shaft. The distributor is splined by a helical gear to the camshaft and provides spark to each spark plug wire. when servicing the distributor, it is critical to ensure proper cap sealing to the distributor body and correct installation to the camshaft. If the distributor is installed a tooth off in relation to the camshaft, a Diagnostic Trouble Code (DTC) will set. The distributor is not repairable and must be replaced as an assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Description and Operation > Page 4282 Distributor: Testing and Inspection NOTICE: Discoloration of the cap and some whitish build up around the cap terminals is normal. Yellowing of the rotor cap, darkening and some carbon build-up under the rotor segment is normal. Replacement of the cap and rotor is not necessary unless there is a driveablity concern. Inspect 1. Cap for cracks, tiny holes or carbon tracks between cap terminal traces. Carbon tracks can be diagnosed by using an ohmmeter. With the cap removed, place one base ohmmeter lead on a cap terminal. Use the other lead to probe all other terminals and the center carbon ball. Move the base lead to the next terminal and probe all other leads. Continue until all secondary terminals have been tested. If there are any non-infinite readings, replace the cap. 2. Cap for excessive build up of corrosion on the terminals. Scrape them clean or replace the cap. Some build up is normal. 3. Rotor segment. Replace the rotor if there is excessive wear on the rotor segment or the plastic under the segment or staked post is melted. Some looseness of the rotor segment is normal and does not cause performance problems. 4. Shaft for shaft-to-bushing looseness. Insert the shaft in the housing. If the shaft wobbles, replace the housing assembly. 5. Housing for cracks or damage. ^ Refer to Computers and Control Systems for ignition system diagnosis. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment Distributor: Adjustments Camshaft Retard Offset Adjustment Description TEST PROCEDURE The ignition timing cannot be adjusted. The distributor may need adjusting to prevent crossfire. To insure proper alignment of the distributor, perform the following: 1. With the ignition OFF, install a scan tool to the DLC. 2. Start the engine and bring to normal operating temperature. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM. 3. Increase engine speed to 1000 RPM. 4. Monitor the Cam Retard Offset. 5. If the Cam Retard indicates a value of 0° +/-2°, the distributor is properly adjusted. 6. If the Cam Retard does not indicate 0° +/-2°, the distributor must be adjusted. ADJUSTING PROCEDURE 1. With the engine OFF, slightly loosen the distributor hold down bolt. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM. 2. Start the engine and raise engine speed to 1000 RPM. 3. Using a scan tool monitor Cam Retard Offset. 4. Rotate the distributor as follows: 4.1. To compensate for a negative reading, rotate the distributor in the counterclockwise direction. 4.2. To compensate for a positive reading, rotate the distributor in the clockwise direction. 5. Repeat step 4 until 0° +/-2°, is obtained. 6. Turn the ignition OFF. 7. Tighten the distributor hold-down bolt to 3 Nm (25 lb. ft.). 8. Start the engine, raise engine speed to 1000 RPM and recheck Camshaft Retard Offset. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 4285 Distributor: Adjustments Timing Adjustment NOTICE: The distributor is located in a fixed, non-adjustable position. No attempt should be made to adjust the engine base timing by rotating the distributor. Attempting to do so may result in engine cross-fire and mis-fire conditions. The distributor ignition system has no provision for timing adjustment. The base timing is preset when the engine is manufactured and no adjustment is possible. NOTICE: If the distributor is removed from the engine, It can be re-installed using "procedure A" as long as the crankshaft has not rotated from its Initial position. if the intake manifold, cylinder head, crankshaft, camshaft, timing gear or complete engine was removed or replaced, "procedure B" must be followed to correctly install the distributor. A Diagnostic Trouble Code (DTC) code may also indicate an Incorrectly installed distributor and engine or distributor damage may occur. Procedure B must then be used. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 4286 Distributor: Adjustments Procedure A Distributor Installation and Removal Procedure A Remove or Disconnect ^ Make sure the ignition switch is "OFF." 1. Spark plug and coil leads from the distributor cap. 2. Three wire hail effect switch plug from the base of the distributor. 3. Two screws holding the distributor cap to the housing. 4. Distributor cap. A. Use a grease pencil to note the position of the rotor segment in relation to the distributor housing. Identify the mark with a 1. B. The distributor housing and intake manifold should also be marked with a grease pencil for proper alignment when reinstalling. 5. Mounting clamp hold down bolt. 6. Distributor. ^ As the distributor is being removed from the engine, you will notice the rotor move in a counter-clockwise direction, 42°. This will appear as slightly more than one clock position. Noting the position of the rotor segment, by placing a second mark on the base of the distributor, will aid in achieving proper rotor alignment during distributor installation. Be sure to identify the second mark on the base with the number 2. Install or Connect Distributor Alignment Indicator A. If the original distributor is to be replaced, rather than repaired, remove the new distributor cap. Using a grease pencil, place two marks on the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 4287 new distributor housing in the same location as the two marks on the original housing. B. When installing the distributor, align the rotor segment with the number 2 mark on the base of the distributor. Guide the distributor into place, making sure the grease pencil marks on the distributor housing and the intake manifold are in line. As the the distributor is being installed, you will notice the rotor will move in a clockwise direction, 42°. ONCE THE DISTRIBUT0R IS COMPLETELY SEATED, the rotor segment should be aligned with the number 1 mark on the base. If the rotor segment is not aligned with the number 1 mark, the gear teeth of the distributor and camshaft have meshed one or more teeth out of time. To correct this condition, remove the distributor and re-install it following the procedure at step B. 1. Distributor cap and mounting screws. Do not overtighten the screws as the boss may strip. 2. Distributor mounting clamp and tighten to proper torque. Tighten ^ Distributor clamp and bolt to 27 Nm (20 lbs. ft.) ^ Distributor cap screws to 4.5-5.0 Nm (40-45 lbs. in.) 3. Three wire hall effect switch connector to base of the distributor. 4. Spark plug and coil leads to the distributor cap. ^ If a check engine light is illuminated after installing the distributor and a DTC P1345 is found, the distributor has been installed incorrectly. You now must refer to procedure; B or proper distributor installation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 4288 Distributor: Adjustments Procedure B Distributor Installation and Removal Procedure B Remove or Disconnect ^ Make sure the ignition switch is "OFF." ^ Bring the engine up to Top Dead Center (TDC) of cylinder number 1. Make sure it is on the compression stroke. A. Remove the distributor cap screws and cap to expose the rotor. Rotor Location B. Align the pre-drilled indent hole in the distributor driven gear with the white painted alignment line on the lower portion of the shaft housing. The rotor segment should point to the cap hold area as shown in the illustration. C. Using a long screw driver, align the oil pump drive shaft in the engine in the mating drive tab in the distributor. D. Guide the distributor into place, making sure the the spark plug towers are perpendicular to the center line of the engine. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 4289 Installed Rotor Position E. ONCE The DISTRIBUTOR IS FULLY SEATED, the rotor segment should be aligned with the pointer cast into the distributor base. This pointer will have a "8" cast into it, indicating the distributor is to be used in a 8 cylinder engine. if the rotor segment does not come within a few degrees of the pointer, the gear mesh between the distributor and camshaft may be off a tooth or more. If this is the case, repeat the procedure again to achieve proper alignment. Install or Connect 1. Cap and mounting screws. Do not overtighten as the boss may strip. 2. Distributor mounting clamp and tighten to proper torque. Tighten ^ Distributor clamp and bolt to 27 Nm (20 lbs. ft.) ^ Distributor cap screws to 4.5-5.0 Nm (40-45 lbs. in.) 3. Three wire hall effect switch plug to base of distributor. 4. Spark plug and coil leads to the distributor cap. ^ If a check engine light is illuminated after installing the distributor and a DTC P1345 is found, the distributor has been installed incorrectly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation Distributor: Service and Repair Distributor Removal & Installation Distributor Removal 1. Remove the ignition coil wire harness from the ignition coil and distributor cap. 2. Remove two screws holding the distributor cap to the housing. 3. Distributor cap. 4. Remove the distributor clamp bolt. 5. Remove the distributor and the distributor clamp. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 4292 6. Remove the distributor gasket and discard. Distributor Installation 1. Bring cylinder number one piston to Top Dead Center (TDC) of compression stroke. 2. Install the distributor cap screws. 3. Install the distributor cap. 4. Install a NEW distributor gasket onto the distributor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 4293 5. Align the indent hole on the driven gear with the paint mark on the distributor housing. 5. Ensure that the distributor rotor segment points to the cap hold area. 7. Align the slotted tang in the oil pump driveshaft with the distributor driveshaft. Rotate the oil pump driveshaft with a screwdriver if necessary. 8. Align the flat (1) in the distributor housing toward the front of the engine. 9. Install the distributor and distributor clamp. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 4294 10. Once the distributor is fully seated, align the distributor rotor segment with the number 8 pointer that is cast into the distributor base. 11. If the distributor rotor segment does not come within a few degrees of the number 8 pointer, the gear mesh between the distributor and camshaft may be off a tooth or more. Repeat the procedure in order to achieve proper alignment. Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems. 12. Install the distributor clamp bolt. Tighten the distributor clamp bolt to 25 Nm (18 ft. lbs.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 4295 13. Install the distributor cap onto the distributor. 14. Install the NEW distributor cap screws. Do not overtighten the NEW distributor cap screws. Tighten the distributor cap screws to 2.4 Nm (21 in. lbs.). 15. Install the ignition coil wire harness. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 4296 Distributor: Service and Repair Distributor Disassembly and Assembly Distributor Components NOTICE: The distributor driven gear can be installed in two positions. Make sure when installing the gear that the dimple found below the roll pin hole in the gear is on the same side as the rotor segment. The dimple will not align directly with the rotor segment if not, the gear is Installed 180° off and a no start condition may occur. Premature wear and damage may result. Remove or Disconnect 1. Two screws holding the cap to the housing. 2. Cap from the housing. 3. Two screws from the rotor. Vane Wheel In Distributor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 4297 4. Rotor. ^ Note which locating holes (B) the rotor was removed from. 5. Two screws holding the hall effect switch. 6. Hall effect switch. ^ The square cut hole (C) in the vane wheel must be aligned with the hall effect switch in order to remove the switch. 7. Roil pin from the shaft. A. Note the dimple located below the roil pin hole on the one side of the gear. The dimple will be used to properly orient the gear on the shaft during assembly. 8. Driven gear, washer, and tang washer. 9. Shaft. ^ If the shaft can't be removed from the distributor housing due to varnish buildup, use a cloth dampened with varnish remover to clean the shaft. NOTICE: Failure to keep cleaning agents away from the hall effect switch may result in premature failure. Install or Connect 1. Hall effect switch. 2. Two screws holding the hall effect switch. Do not overtighten as the base may strip. 3. Shaft. 4. Tang washer, washer, and driven gear. ^ When the driven gear is properly installed the dimple located below the roll pin hole, in the driven gear, will be on the same side as the rotor segment when the rotor is installed in the distributor. If the driven gear is installed incorrectly, the dimple will be on the opposite of the rotor segment. 5. Roll pin. 6. Rotor. ^ "A" shows the mounting holes. "B" shows the locating holes. 7. Two screws holding rotor. Tighten ^ Screws to 2.0 Nm (20 lbs. In.) Installation of the distributor into the engine will require the distributor cap off of the assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 4298 Distributor: Service and Repair Distributor Alignment/Camshaft Retard Offset Adjustment Description TEST PROCEDURE The ignition timing cannot be adjusted. The distributor may need adjusting to prevent crossfire. To insure proper alignment of the distributor, perform the following: 1. With the ignition OFF, install a scan tool to the DLC. 2. Start the engine and bring to normal operating temperature. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM. 3. Increase engine speed to 1000 RPM. 4. Monitor the Cam Retard Offset. 5. If the Cam Retard indicates a value of 0° +/-2°, the distributor is properly adjusted. 6. If the Cam Retard does not indicate 0° +/-2°, the distributor must be adjusted. ADJUSTING PROCEDURE 1. With the engine OFF, slightly loosen the distributor hold down bolt. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM. 2. Start the engine and raise engine speed to 1000 RPM. 3. Using a scan tool monitor Cam Retard Offset. 4. Rotate the distributor as follows: 4.1. To compensate for a negative reading, rotate the distributor in the counterclockwise direction. 4.2. To compensate for a positive reading, rotate the distributor in the clockwise direction. 5. Repeat step 4 until 0° +/-2°, is obtained. 6. Turn the ignition OFF. 7. Tighten the distributor hold-down bolt to 3 Nm (25 lb. ft.). 8. Start the engine, raise engine speed to 1000 RPM and recheck Camshaft Retard Offset. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 4299 Distributor: Service and Repair Distributor Assembly Replacement Removal Procedure NOTICE: If the distributor is removed from the engine, It can be re-installed using "procedure A" as long as the crankshaft has not rotated from the original position. If the intake manifold, cylinder head, crankshaft, camshaft, timing gear or complete engine was removed or replaced, "Procedure B" must be followed in order to correctly install the distributor. A DTC code may also indicate an incorrectly installed distributor and engine or distributor damage may occur. Procedure B must then be used. 1. Turn OFF the ignition switch. 2. Remove the spark plug and the ignition coil wires from distributor cap. 3. Remove the three-wire hall effect switch connector from the base of the distributor. 4. Remove the two screws holding the distributor cap to the housing. 5. Remove the distributor cap. A. Use a grease pencil in order to note the position of the rotor in relation to the distributor housing. Identify the mark with the number 1. B. Mark the distributor housing and the intake manifold with a grease pencil for proper alignment when reinstalling. 6. Remove the mounting clamp hold down bolt. 7. Remove the distributor. 8. As the distributor is being removed from the engine, you will notice the rotor move in a counter-clockwise direction about 42 degrees. This will appear as slightly more than one clock position. Noting the position of the rotor segment by placing a second mark on the base of the distributor will aid in achieving proper rotor alignment during the distributor installation. Identify the second mark on the distributor housing at number 2. Installation Procedure A 1. Remove the new distributor cap. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 4300 2. If installing a new distributor assembly, place two marks on the new distributor housing in the same location as the two marks on the original housing. 3. When installing the distributor, align the rotor with mark made at location 2.. 4. Guide the distributor into place, making sure the mounting hole in the distributor hold down base is aligned over the mounting hole in the intake manifold. 5. As the distributor is being installed, you will notice the rotor will move in a clockwise direction about 42 degrees. 6. Once the distributor is completely seated, the rotor segment should be aligned with mark on the base in location number 1. If the rotor segment is not aligned with the number 1 mark, the gear teeth of the distributor and the camshaft have meshed one or more teeth out of time. In order to correct the condition, remove the distributor and reinstall it. 7. Install the cap and the mounting screws. Do not overtighten as they may strip. Tighten Tighten the distributor cap screws to 5 Nm (45 lb in). NOTICE: Use the correct fasteners in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces inless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems. 8. Install the distributor clamp bolt. Tighten Tighten the distributor clamp bolt to to 27 Nm (20 lb ft). NOTICE: Use the correct fasteners in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 4301 paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces inless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems. 9. Install the three wire hall effect switch connector to the base of the distributor. 10. Install the spark plug and the ignition coil wires to the distributor cap. Important: If a check engine light is illuminated after installing the distributor and a DTC P1345 is found, the distributor has been installed incorrectly. Refer to procedure B for proper distributor installation. Installation Procedure B 1. Rotate the number 1 cylinder up to Top Dead Center (TDC) of the compression stroke. 2. Remove the distributor cap screws and the distributor cap to expose the rotor. 3. Align the pre-drilled indent hole in the distributor driven gear with the white alignment line on the lower portion of the shaft housing. 4. The rotor should point to the cap hold down mount nearest the flat side of the housing. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 4302 5. Using a long screw driver, align the oil pump drive shaft to the drive tab of the distributor. 6. Guide the distributor in place, ensuring that the spark plug towers are perpendicular to the centerline of engine. 7. Once the distributor is fully seated, the rotor segment should be aligned with the pointer cast into the distributor base. This pointer will have a 6 or 8 cast into it, indicating that the distributor is to be used on a 6 or 8 cylinder engine. If the rotor segment does not come within a few degrees of the pointer, the gear mesh between the distributor and the camshaft may be off a tooth or more. If this is the case, repeat the procedure again in order to achieve proper alignment. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Spark Plug > Component Information > Specifications Spark Plug: Specifications Spark plug type .................................................................................................................................... ....................................................................... 41-932 Spark plug gap ................................................ ....................................................................................................................................................... 0.060 inch Spark plugs (new cylinder head) ........................................................................................ ........................................................................ 30 Nm (22 lb. ft.) Spark plugs (used cylinder head) ... ............................................................................................................................................................ 20 Nm (14 lb. ft.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Spark Plug > Component Information > Specifications > Page 4306 Spark Plug: Description and Operation DESCRIPTION Resistor-type. tapered-seat spark plugs are used. No gasket is used on these plugs. These spark plugs are a High Efficiency (HE) spark plug that has a fine wire electrode, nickel plated shell and a platinum pad across from the electrode. These features give the HE spark plug long life durability. Refer to Specifications or to the Vehicle Emissions Control Information label on the fan shroud for correct gap information. See: Specifications CONSTRUCTION If the spark plug shell hex is not fully engaged in the spark plug socket wrench, the socket may cock at an angle and cause insulator cracking and/or breakage during plug installation or removal. OPERATION Normal or average service is assumed to be a mixture of idling, low speed, and high speed operation with some of each making up the daily total driving. Occasional or intermittent high-speed driving is essential to good spark plug performance. It provides increased and sustained combustion heat that burns away any excess deposits of carbon or oxide that may have accumulated from frequent idling or continual stop-and-go or slow-speed driving. Spark plugs are protected by an insulating boot made of special heat-resistant material that covers the spark plug terminal and extends downward over a portion of the plug insulation These boots prevent flash-over with resultant missing of the engine, even though a film is allowed to accumulate on the exposed portion of plug porcelains. Do not mistake corona discharge for flash-over or a shorted insulator. Corona discharge is a steady blue light appearing around the insulator. just above the shell crimp It is the visible evidence of a high-tension field, and has no effect on ignition performance. Usually it can be detected only in darkness. This discharge may repel dust particles, leaving a clear ring on the insulator just above the shell. This ring is sometimes mistakenly regarded as evidence that combustion gases have blown out between the shell and insulator. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Spark Plug > Component Information > Specifications > Page 4307 Spark Plug Diagnosis Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Spark Plug > Component Information > Specifications > Page 4308 Spark Plug: Service and Repair CAUTION ^ Allow the engine to cool before removing the spark plugs. Attempting to remove the plugs from a hot engine may cause the plug to seize, causing damage to the cylinder head threads. ^ Clean the spark plug recess area before removing the plug. Failure to do so can result in engine damage due to dirt or foreign material entering the cylinder head or contamination of the cylinder head threads. Contaminated threads may prevent proper seating of a new plug. ^ Do not install plugs that are either hotter or colder than the heat range specified. Using plugs of the wrong heat range can severely damage the engine. REMOVE OR DISCONNECT ^ Make sure the ignition switch is OFF. CAUTION: Twist the spark plug boot one-half turn to release it. Pull on the spark plug boot only. Do not pull on the wire or the spark plug lead may be damaged. 1. Spark plug wires and boots. ^ Label the plug wires. CAUTION: Be sure to use J 39358 or equivalent spark plug socket Failure to do so could cause cracking of the insulator and arcing inside the plug, resulting in engine misfire. 2. Spark plugs using J 39358 or equivalent. Inspect ^ Each spark plug for wear and gap. ^ Spark plugs should be gapped to 0.060 inch. INSTALL OR CONNECT CAUTION: Make sure each sparkplug threads smoothly into the cylinder head and is fully seated. Cross-threading or falling to fully seat spark plugs can cause overheating of the plugs, exhaust blow-by, or thread damage. 1. Spark plugs. Tighten ^ Spark plugs to 30 Nm (22 lb. ft.) in a new cylinder head and 20 Nm (14 lb. ft.) in a used head. 2. Wire and boot assemblies. Refer to Spark Plug Wiring and Boots for precautions. See: Spark Plug Wire/Service Precautions Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Compression Check > System Information > Specifications Compression Check: Specifications Minimum, 698 kPa (100 psi) @ 200 rpm. The lowest cylinder reading should not be less than 80% of the highest. Perform compression test with engine at normal operating temperature, spark plugs removed and throttle wide open. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Valve Clearance > System Information > Specifications > Valve Clearance Specifications Valve Clearance: Specifications Valve Clearance Specifications One turn down from zero lash. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Valve Clearance > System Information > Specifications > Valve Clearance Specifications > Page 4316 Valve Clearance: Specifications Valve Arrangement FRONT TO REAR 5.7L/V8-350 ......................................................................................................................................... ........................................................... E-I-I-E-E-I-I-E Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Tune-up and Engine Performance Checks > Valve Clearance > System Information > Specifications > Page 4317 Valve Clearance: Adjustments 1. Remove rocker arm cover. 2. Crank engine until the mark on the vibration damper aligns with the "0 mark on the timing tab and the engine is in the number one firing position. This may be determined by placing fingers on valves of number one cylinder as the mark on the damper comes near the " 0 mark on the timing tab. If the rocker arms are not moving, the engine is in the number one firing position. If the rocker arms move as the marks comes up to the timing tab, the engine is in the number six firing position and should be turned over one more time to reach the number one firing position. 3. With the engine in this position, exhaust valves 1, 3, 4 and 8 and intake valves 1, 2, 5 and 7 can be adjusted. Even numbered cylinders are in the right bank, odd numbered cylinders are in the left bank when viewed from the rear of the engine. 4. Back off the adjusting nut until lash is felt at the pushrod, then turn in the adjusting nut until all lash is removed. This can be determined by rotating the pushrod while turning the adjusting nut. When play has been removed, turn the adjusting nut in one full additional turn. 5. Crank engine one complete revolution until the timing tab " 0 mark and vibration damper mark are aligned. This is the number six firing position. 6. With the engine in this position, exhaust valves 2, 5, 6 and 7 and intake valves 3, 4, 6 and 8 can be adjusted. 7. With valves properly adjusted, install rocker arm cover. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > A/C Signal > Component Information > Description and Operation A/C Signal: Description and Operation The A/C request circuit signals the VCM when an A/C mode is selected at the A/C control head. The VCM uses this information to enable the A/C compressor clutch and to adjust the idle speed before turning ON the A/C clutch. If this signal is not available to the VCM, the A/C compressor will be inoperative. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions Mass Air Flow (MAF) Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4326 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4327 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4328 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4329 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4330 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4331 Mass Air Flow (MAF) Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4332 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4333 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4334 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4335 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4336 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4337 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4338 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4339 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4340 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4341 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4342 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4343 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4344 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4345 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4346 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4347 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4348 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4349 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4350 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4351 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4352 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4353 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4354 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4355 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4356 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4357 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4358 Mass Air Flow System Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Page 4359 Mass Air Flow (MAF) Sensor: Description and Operation Mass Air Flow (MAF) Sensor The Mass Air Flow (MAF) sensor measures the amount of air which passes through it. The VCM uses this information to determine the operating condition of the engine, to control fuel delivery. A large quantity of air indicates acceleration. A small quantity of air indicates deceleration or idle. The scan tool reads the MAF value and displays it in grams per second (gm/Sec). At idle, it should read between 5-7 gm/Sec on a fully warmed up engine. Values should change rather quickly on acceleration, but values should remain fairly stable at any given RPM. When the VCM detects a malfunction in the MAF sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0101 system performance. ^ DTC P0102 frequency low. ^ DTC P0103 frequency high. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Page 4360 Mass Air Flow (MAF) Sensor: Service and Repair MAF Sensor MAF Sensor Intake Duct REMOVAL PROCEDURE CAUTION: Take care when handling the Mass Air Flow (MAF). Do Not dent, puncture, or otherwise damage the honeywell located at the air inlet end of the MAF. Do Not touch the sensing elements or allow anything (including solvents and lubricants) to come in contact with them. A small amount of GM lubricant (P/N 99855406) may be used on the air duct only to aid in installation. Do Not drop or roughly handle the MAF. 1. Disconnect the 3 wire electrical connector. 2. Loosen the clamp on the intake duct. 3. Carefully remove the MAF sensor. INSTALLATION PROCEDURE 1. Install the MAF sensor. 2. Install the intake ducts. 3. Tighten the clamp. 4. Connect the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Specifications Intake Air Temperature (IAT) Sensor: Specifications Torque Valve Torque Valve Induction Air Sensor 44 in.lb Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions Intake Air Temperature (IAT) Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4366 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4367 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4368 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4369 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4370 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4371 Intake Air Temperature (IAT) Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4372 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4373 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4374 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4375 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4376 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4377 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4378 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4379 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4380 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4381 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4382 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4383 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4384 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4385 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4386 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4387 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4388 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4389 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4390 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4391 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4392 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4393 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4394 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4395 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4396 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4397 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4398 IAT Sensor Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Page 4399 Intake Air Temperature (IAT) Sensor: Description and Operation Intake Air Temperature (IAT) Sensor PURPOSE The Intake Air Temperature (IAT) sensor is a thermistor which changes value based on the temperature of air entering the engine. OPERATION Low temperature produces a high resistance 100,000 ohms at -40° (-40°F). A high temperature causes low resistance 70 ohms at 130°C (266°F). The VCM supplies a 5.0 volt signal to the sensor through a resistor in the VCM and measures the voltage. The voltage will be high when the incoming air is cold, and low when the air is hot. By measuring the voltage, the VCM calculates the incoming air temperature. The IAT sensor signal is used to adjust spark timing according to incoming air density. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Page 4400 Intake Air Temperature (IAT) Sensor: Testing and Inspection The scan tool displays temperature of the air entering the engine, which should read close to ambient air temperature when engine is cold, and rise as underhood temperature increases. If the engine has not been run for several hours (overnight) the Intake Air Temperature (IAT) sensor temperature and engine coolant temperature should read close to each other. If the VCM detects a malfunction in the AT sensor circuit, the following DTCs will set: ^ DTC P0112 circuit low. ^ DTC P0113 circuit high. ^ DTC P0111 circuit intermittent high. ^ DTC P0112 circuit intermittent low. Refer to Diagnostic Tables. See: Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Page 4401 Intake Air Temperature (IAT) Sensor: Service and Repair IAT Sensor And Electrical Connector REMOVAL PROCEDURE 1. Disconnect the electrical connector releasing locking tab. 2. Remove the Intake Air Temperature (IAT) sensor by grasping sensor, twist and pull out from air cleaner INSTALLATION PROCEDURE 1. Install the IAT sensor. 2. Connect the electrical connector Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Camshaft Position Sensor: Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4406 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4407 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4408 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4409 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4410 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4411 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4412 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Page 4413 Camshaft Position Sensor: Specifications Camshaft position sensor retaining screw ........................................................................................................................................... 4-6 Nm (35-53 lb. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Page 4414 Engine View, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Camshaft Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4417 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4418 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4419 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4420 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4421 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4422 Camshaft Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4423 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4424 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4425 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4426 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4427 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4428 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4429 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4430 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4431 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4432 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4433 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4434 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4435 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4436 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4437 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4438 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4439 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4440 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4441 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4442 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4443 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4444 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4445 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4446 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4447 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4448 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Page 4449 Camshaft Position Sensor: Description and Operation Camshaft Position Sensor The Camshaft Position (CMP) sensor is located within the distributor. It's operation is very similar to the Crankshaft Position (CKP) sensor however it will provide one pulse per camshaft revolution (1x signal). This signal is not detrimental to the driveability of the vehicle. The Vehicle Control Module (VCM) utilizes this signal in conjunction with the crankshaft position to determine which cylinder(s) are misfiring. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Testing and Inspection > Cam Signal Camshaft Position Sensor: Testing and Inspection Cam Signal The VCM uses this signal to determine the position of the #1 piston during its power stroke. This signal is used by the VCM to calculate fuel injection mode of operation. A loss of this signal will set DTC P0340. If the cam signal is lost while the engine is running, the fuel injection system will shift to a calculated fuel injection mode based on the last fuel injection pulse, and the engine will continue to run. The engine can be restarted and will run in the calculated mode as long as the fault is present Refer to Diagnostic Trouble Code (DTC) P0340 Camshaft Position Sensor (CKP) Sensor Circuit. See: Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Camshaft Position Sensor > Component Information > Testing and Inspection > Page 4452 Camshaft Position Sensor: Service and Repair REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Disconnect the electrical connector from the camshaft position sensor. 3. Remove the camshaft position sensor retaining screw. 4. Remove the camshaft position sensor. INSTALLATION PROCEDURE 1. Install the camshaft position sensor. 2. Install the camshaft position sensor retaining screw, torque to 4-6 Nm (35-53 lb. in.). 3. Connect the electrical connector. 4. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Specifications Coolant Temperature Sensor/Switch (For Computer): Specifications Engine Coolant Temperature (ECT) sensor .............................................................................................................................................. 13 Nm (10 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Specifications > Page 4456 Engine Side, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions Coolant Temperature Sensor/Switch (For Computer): Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4459 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4460 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4461 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4462 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4463 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4464 Coolant Temperature Sensor/Switch (For Computer): Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4465 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4466 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4467 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4468 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4469 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4470 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4471 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4472 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4473 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4474 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4475 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4476 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4477 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4478 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4479 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4480 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4481 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4482 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4483 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4484 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4485 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4486 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4487 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4488 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4489 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4490 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 4491 ECT Sensor Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 4492 Coolant Temperature Sensor/Switch (For Computer): Description and Operation Engine Coolant Temperature (ECT) Sensor DESCRIPTION The engine coolant temperature sensor is a thermistor (a resistor which changes value based on temperature) mounted in the engine coolant passage. Low coolant temperature produces a high resistance 100,000 ohms at -40°C (-40°F) while high temperature causes low resistance 70 ohms at 130°C (266°F). OPERATION The VCM supplies a 5 volt signal to the engine coolant temperature sensor through a resistor in the VCM and measures the voltage. The voltage will be high when the engine is cold. The voltage will be low when the engine is hot. By measuring the voltage, the VCM calculates the engine coolant temperature. Engine coolant temperature affects most systems the VCM controls. The scan tool displays engine coolant temperature in degrees. After engine start-up, the temperature should rise steadily to about 9O°C (194°F) then stabilize when thermostat opens. If the engine has not been run for several hours (overnight), the engine coolant temperature and intake air temperature displays should be close to each other. When the VCM detects a malfunction in the Engine Coolant Temperature (ECT) sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0117 circuit low. ^ DTC P0118 circuit high. ^ DTC P0125 excessive time to Closed Loop. ^ DTC P1114 circuit intermittent low. ^ DTC P1115 circuit intermittent high. The above DTCs contain a table to check for sensor resistance values relative to temperature. Refer to Specifications. See: Specifications Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 4493 Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection The scan tool displays engine coolant temperature in degrees. After engine start-up, the temperature should rise steadily to about 90°C (194°F) then stabilize when thermostat opens. If the engine has not been run for several hours (overnight), the engine coolant temperature and intake air temperature displays should be close to each other. When the VCM detects a malfunction in the Engine Coolant Temperature (ECT) sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0117 circuit low. ^ DTC P0118 circuit high. ^ DTC P0125 excessive time to Closed Loop. ^ DTC P1114 circuit intermittent low. ^ DTC P1115 circuit intermittent high. The above DTCs contain a table to check for sensor resistance values relative to temperature. Refer to Diagnostic Tables. See: Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 4494 Coolant Temperature Sensor/Switch (For Computer): Service and Repair Engine Coolant Temperature (ECT) Sensor Electrical Connector Engine Coolant Temperature (ECT) Sensor CAUTION: Use care when handling the coolant sensor. Damage to the coolant sensor will affect the operation of the fuel control system. REMOVAL PROCEDURE 1. Relieve the coolant pressure. 2. Disconnect the negative battery cable. 3. Drain the cooling system below the level of the sensor. 4. Disconnect the electrical connector releasing locking tab. 5. Remove the coolant sensor from engine. INSTALLATION PROCEDURE 1. Coat the threads (only) with sealer P/N 9985253 or equivalent. Tighten ^ Tighten the sensor to 13 N.m (10 lb. ft.). 2. Install the coolant sensor in the engine. 3. Connect the electrical connector. 4. Refill the cooling system. 5. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-014 > Apr > 00 > Engine No/Hard/Slow Start/Backfire/Kickback Crankshaft Position Sensor: Customer Interest Engine - No/Hard/Slow Start/Backfire/Kickback File In Section: 06 - Engine/Propulsion System Bulletin No.: 00-06-04-014 Date: April, 2000 TECHNICAL Subject: No, Hard, or Slow Start, Backfire or "Kickback" During Crank/Start, "Grinding" or Unusual Noises During Crank, DTC P0338 (Replace Crankshaft Position Sensor) Models: 1999-2000 Cadillac Escalade 1995-2000 Chevrolet and GMC SIT Models 1996-2000 Chevrolet and GMC C/K, M/L, G, P Models 1996-2000 Oldsmobile Bravada with 4.3 L, 5.0 L, 5.7 L or 7.4 L Engine (VINs W, X, M, R, J RPOs L35, LF6, L30, L31, L29) Condition: Some customers may comment on one or more of the following conditions: ^ Backfire during crank/start ^ "Kickback" during crank/start ^ "No" start ^ "Slow" or "hard" start/crank ^ "Grinding" or unusual noises during crank/start ^ Cracked or broken engine block at the starter boss ^ Broken starter drive housing ^ Broken starter ring gear on flywheel ^ Any combination of the above Cause: A condition may exist that allows the crankshaft position sensor to command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss. Correction: Inspect for a stored powertrain DTC code P0338. This DTC will NOT illuminate the "Service Engine Soon" light. If this code is stored, the Crankshaft Position Sensor, P/N 10456607, MUST be replaced and the remaining components inspected for damage (engine block at the starter boss, the starter drive housing, and the engine flywheel starter ring gear). Notice: When DTC code P0338 is set, failure to replace the Crankshaft Position Sensor could result in repeated inoperative conditions of the starter or flywheel. Important: Some flywheel wear is normal; broken or missing teeth and/or cracks, are not normal. Parts Information Parts are currently available from GMSPO. Warranty Information: For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 00-06-04-014 > Apr > 00 > Engine - No/Hard/Slow Start/Backfire/Kickback Crankshaft Position Sensor: All Technical Service Bulletins Engine - No/Hard/Slow Start/Backfire/Kickback File In Section: 06 - Engine/Propulsion System Bulletin No.: 00-06-04-014 Date: April, 2000 TECHNICAL Subject: No, Hard, or Slow Start, Backfire or "Kickback" During Crank/Start, "Grinding" or Unusual Noises During Crank, DTC P0338 (Replace Crankshaft Position Sensor) Models: 1999-2000 Cadillac Escalade 1995-2000 Chevrolet and GMC SIT Models 1996-2000 Chevrolet and GMC C/K, M/L, G, P Models 1996-2000 Oldsmobile Bravada with 4.3 L, 5.0 L, 5.7 L or 7.4 L Engine (VINs W, X, M, R, J RPOs L35, LF6, L30, L31, L29) Condition: Some customers may comment on one or more of the following conditions: ^ Backfire during crank/start ^ "Kickback" during crank/start ^ "No" start ^ "Slow" or "hard" start/crank ^ "Grinding" or unusual noises during crank/start ^ Cracked or broken engine block at the starter boss ^ Broken starter drive housing ^ Broken starter ring gear on flywheel ^ Any combination of the above Cause: A condition may exist that allows the crankshaft position sensor to command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss. Correction: Inspect for a stored powertrain DTC code P0338. This DTC will NOT illuminate the "Service Engine Soon" light. If this code is stored, the Crankshaft Position Sensor, P/N 10456607, MUST be replaced and the remaining components inspected for damage (engine block at the starter boss, the starter drive housing, and the engine flywheel starter ring gear). Notice: When DTC code P0338 is set, failure to replace the Crankshaft Position Sensor could result in repeated inoperative conditions of the starter or flywheel. Important: Some flywheel wear is normal; broken or missing teeth and/or cracks, are not normal. Parts Information Parts are currently available from GMSPO. Warranty Information: For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Crankshaft Position Sensor: All Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4512 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4513 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4514 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4515 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4516 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4517 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4518 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Crankshaft Position Sensor: All Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4524 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4525 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4526 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4527 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4528 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4529 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 4530 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Page 4531 Crankshaft Position Sensor: Specifications Crankshaft Position Sensor mounting bolts ................................................................................................................................................. 8 Nm (71 lb. In.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Page 4532 Engine Side, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Crankshaft Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4535 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4536 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4537 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4538 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4539 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4540 Crankshaft Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4541 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4542 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4543 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4544 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4545 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4546 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4547 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4548 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4549 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4550 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4551 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4552 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4553 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4554 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4555 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4556 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4557 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4558 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4559 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4560 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4561 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4562 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4563 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4564 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4565 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4566 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Page 4567 Crankshaft Position Sensor: Description and Operation DESCRIPTION The Crankshaft Position (CKP) Sensor is located in the front engine cover and is perpendicular to the crankshaft target wheel. The air gap between the sensor and the wheel is preset and not adjustable. The target wheel has three slots 60° apart and is keyed to the crankshaft. As the target wheel rotates, the slots passing by the sensor create a change in the magnetic field of the sensor which results in an induced voltage pulse. One revolution of the crankshaft results in three pulses (3x signal). Based on these pulses, the VCM is able to determine crankshaft position and engine speed. The VCM then activates the fuel injector and provides a spark to the Distributor. The relation between the crankshaft position sensor and the target wheel is crucial. The sensor must be exactly perpendicular to the target wheel with the correct air gap. OPERATION The crankshaft position sensor provides the VCM with crankshaft speed and crankshaft position. The VCM utilizes this information to determine if an engine Misfire is present. The VCM monitors the Crankshaft Position Sensor (CKP) sensor for momentarily drop in crankshaft speed to determine if a misfire is occurring. When the VCM detects a misfire, a Diagnostic Trouble Code (DTC) P0300 will set. The VCM also monitors the CKP sensor signal circuit for malfunctions. The VCM monitors CKP signal and the High and Low resolution signals. The VCM calculates these signals to determine a ratio. When the VCM detects that the ratio is out of normal operating range, the VCM will set a Diagnostic Trouble Code (DTC) P0337 or a DTC P0338. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Page 4568 Crankshaft Position Sensor: Service and Repair REMOVAL PROCEDURE 1. Remove the electrical connector. 2. Remove the sensor hold down bolt. 3. Remove the sensor from the timing cover. NOTE: When installing or removing a crankshaft position (CKP) sensor make sure the sensor is fully seated and held stationary in the front cover before torquing the hold down bolt into the front cover. A sensor which is not seated may result in erratic operation and lead to the setting of false codes. 4. Inspect the sensor O-ring for wear, cracks or leakage. Replace if necessary. Lube the new O-ring with clean engine oil before installing. INSTALLATION PROCEDURE NOTE: Make certain that the Crankshaft Position (CKP) sensor mounting surfaces are clean and free of burrs before installing the CKP sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Page 4569 1. Install the sensor into the timing cover. 2. Install the sensor hold down bolt. Tighten ^ Tighten the hold down bolt to 8 Nm (71 lb. in.). 3. Install the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Locations Data Link Connector Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions Data Link Connector: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4575 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4576 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4577 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4578 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4579 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4580 Data Link Connector: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4581 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4582 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4583 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4584 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4585 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4586 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4587 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4588 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4589 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4590 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4591 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4592 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4593 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4594 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4595 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4596 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4597 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4598 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4599 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4600 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4601 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4602 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4603 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4604 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4605 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4606 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4607 Data Link Connector: Connector Views Data Link Connector Data Link Connector Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Diagrams > Diagram Information and Instructions > Page 4608 Data Link Connector (DLC) Pin Assignment Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Description and Operation > Circuit Operation Data Link Connector: Description and Operation Circuit Operation A Scan Tool can be connected to the Data Link Connector (DLC), this allows the Scan Tool to communicate with the Diesel Powertrain Control Module (PCM) Gasoline Vehicle Control Module (VCM) the Diagnostic Energy Reserve Module (DERM), the Transfer Case Control Module or the Brake Pressure Modulator Valve. System operations can then be monitored for diagnostic purposes. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Data Link Connector > Component Information > Description and Operation > Circuit Operation > Page 4611 Data Link Connector: Description and Operation Data Link Connector (DLC) Data Link Connector The provision for communicating with the control module is a Data Link Connector (DLC). The DLC is usually located under the instrument panel. The DLC is used in order to connect to a scan tool. Some common uses of the scan tool are listed below: ^ Identifying stored Diagnostic Trouble Codes (DTCs). ^ Clearing the DTCs. ^ Performing output control tests. ^ Reading serial data. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > Customer Interest: > 77-71-53 > Apr > 97 > A/T - Chuggle/Surge on TCC Apply/No DTC's Engine Control Module: Customer Interest A/T - Chuggle/Surge on TCC Apply/No DTC's File In Section: 7 - Transmission Bulletin No.: 77-71-53 Date: April, 1997 Subject: Chuggle/Surge on TCC Apply/No DTC's (Reflash PCM) Models: 1996-97 Chevrolet and GMC C/K, G Models with 5.7L Engine (VIN R - RPO L31) and HYDRA-MATIC 4L60-E Transmission (RPO M30) Condition Some owners of the above models may experience a chuggle/surge when TCC is applied under light throttle acceleration. Cause Engine inputs (Combustion events) exciting the vehicle platform/driveline or tire balance may be a contributing factor. Correction First ensure the most recent engine, not transmission calibration has been installed (Corp. # 76-65-04) and check tire balance. A new transmission calibration to correct chuggle/surge is available for use on vehicles with persistent concerns only. Important: This calibration will raise TCC engagement approximately 7-10 mph depending on application. This calibration should not be installed until the engine calibration listed above has been installed. Installation of this calibration may lead to decreased fuel economy due to TCC engagement at higher speeds. Reflash the Powertrain Control Module with the appropriate part numbers below. Refer to your Service Manual for proper procedure. Parts Information This new calibration will be available starting with the 1997 Disc 4 update. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J6355 Reflash Control Module Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Engine Control Module: > 04-06-04-054B > Nov > 10 > Engine Controls - Aftermarket Accessory Usage Engine Control Module: All Technical Service Bulletins Engine Controls - Aftermarket Accessory Usage INFORMATION Bulletin No.: 04-06-04-054B Date: November 18, 2010 Subject: Info - Non-GM Parts and Accessories (Aftermarket) Models: 2011 and Prior GM Passenger Cars and Trucks Supercede: This bulletin is being revised to add model years and update to the new U.S. Fixed Operation Manager (FOM) and Canada Warranty Manager (WM) names. Please discard Corporate Bulletin Number 04-06-04-054A (Section 06 - Engine/Propulsion System). The recent rise and expansion of companies selling non-GM parts and accessories has made it necessary to issue this reminder to dealers regarding GM's policy on the use and installation of these aftermarket components. When a dealer is performing a repair under the New Vehicle Limited Warranty, they are required to use only genuine GM or GM-approved parts and accessories. This applies to all warranty repairs, special policy repairs or any repairs paid for by GM. Parts and accessories advertised as being "the same" as parts manufactured by GM, but not sold through GM, do not qualify for use in warranty repairs, special policy repairs or any repairs paid for by GM. During a warranty repair, if a GM original equipment part is not available through GM Customer Care and Aftersales (GM CC&A;), ACDelco(R) distributors, other GM dealers or approved sources, the dealer is to obtain comparable, non-GM parts and clearly indicate, in detail, on the repair order the circumstances surrounding why non-GM parts were used. The dealer must give customers written notice, prior to the sale or service, that such parts or accessories are not marketed or warranted by General Motors. It should also be noted that dealers modifying new vehicles and installing equipment, parts and accessories obtained from sources not authorized by GM are responsible for complying with the National Traffic and Motor Vehicle Safety Act. Certain non-approved parts or assemblies, installed by the dealer or its agent not authorized by GM, may result in a change to the vehicle's design characteristics and may affect the vehicle's ability to conform to federal law. Dealers must fully understand that non-GM approved parts may not have been validated, tested or certified for use. This puts the dealer at risk for potential liability in the event of a part or vehicle failure. If a GM part failure occurs as the result of the installation or use of a non-GM approved part, the warranty will not be honored. A good example of non-authorized modification of vehicles is the result of an ever increasing supply of aftermarket devices available to the customer, which claim to increase the horsepower and torque of the Duramax(TM) Diesel Engines. These include the addition of, but are not limited to one or more of the following modifications: - Propane injection - Nitrous oxide injection - Additional modules (black boxes) that connect to the vehicle wiring systems - Revised engine calibrations downloaded for the engine control module - Calibration modules which connect to the vehicle diagnostic connector - Modification to the engine turbocharger waste gate Although the installation of these devices, or modification of vehicle components, can increase engine horsepower and torque, they may also negatively affect the engine emissions, reliability and/or durability. In addition, other powertrain components, such as transmissions, universal joints, drive shafts, and front/rear axle components, can be stressed beyond design safety limits by the installation of these devices. General Motors does not support or endorse the use of devices or modifications that, when installed, increase the engine horsepower and torque. It is because of these unknown stresses, and the potential to alter reliability, durability and emissions performance, that GM has adopted a policy that prevents any UNAUTHORIZED dealer warranty claim submissions to any remaining warranty coverage, to the powertrain and driveline components whenever the presence of a non-GM (aftermarket) calibration is confirmed - even if the non-GM control module calibration is subsequently removed. Refer to the latest version of Bulletin 09-06-04-026 (V8 Gas Engines) or 06-06-01-007 (Duramax(TM) Diesel Engines) for more information on dealer requirements for calibration verification. These same policies apply as they relate to the use of non-GM accessories. Damage or failure from the use or installation of a non-GM accessory will not be covered under warranty. Failure resulting from the alteration or modification of the vehicle, including the cutting, welding or disconnecting of the vehicle's original equipment parts and components will void the warranty. Additionally, dealers will NOT be reimbursed or compensated by GM in the event of any legal inquiry at either the local, state or federal level that Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Engine Control Module: > 04-06-04-054B > Nov > 10 > Engine Controls - Aftermarket Accessory Usage > Page 4625 results from the alteration or modification of a vehicle using non-GM approved parts or accessories. Dealers should be especially cautious of accessory companies that claim the installation of their product will not void the factory warranty. Many times these companies have even given direction on how to quickly disassemble the accessory in an attempt to preclude the manufacturer from finding out that is has been installed. Any suspect repairs should be reviewed by the Fixed Operations Manager (FOM), and in Canada by the Warranty Manager (WM) for appropriate repair direction. If it is decided that a goodwill repair is to be made on the vehicle, even with the installation of such non-GM approved components, the customer is to be made aware of General Motors position on this issue and is to sign the appropriate goodwill documentation required by General Motors. It is imperative for dealers to understand that by installing such devices, they are jeopardizing not only the warranty coverage, but also the performance and reliability of the customer's vehicle. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Engine Control Module: > 83-81-32 > Sep > 98 > PCM Connector - Information on New Service Kits Engine Control Module: All Technical Service Bulletins PCM Connector - Information on New Service Kits File In Section: 8 - Chassis/Body Electrical Bulletin No.: 83-81-32 Date: September, 1998 INFORMATION Subject: New Powertrain Control Module (PCM) Connector Service Kits Models: 1996-99 All Passenger Cars except Geo and Catera Two new kits have been released to service the Powertrain Control Module (PCM) connector If the connector has been damaged during servicing. This PCM has an aluminum body and is usually mounted underhood. Kit (P/N 12167308) contains the 80 way connector body, the cover, two each of four different terminal retainers and 25 empty cavity plugs. No terminals are included. If terminals are needed, use P/N 12084913 for 0.35 mm and 0.50 mm wire and P/N 12084912 for 0.80 mm wire. These terminals are included in the terminal repair kit J 38125A or B, and replacements can be ordered from Kent-Moore. kit (P/N 12167313) contains one connector seal. Whenever the connector is unbolted from the aluminum body of the PCM, the seal can stick to the body, or may be twisted. This seal should be replaced whenever the connector is removed in service. Parts Information P/N Description 12167308 Kit, PCM Harness Repair 12167313 Seal Kit, PCM Connector 12084912 Terminal 12084913 Terminal Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Engine Control Module: > 77-71-53 > Apr > 97 > A/T - Chuggle/Surge on TCC Apply/No DTC's Engine Control Module: All Technical Service Bulletins A/T - Chuggle/Surge on TCC Apply/No DTC's File In Section: 7 - Transmission Bulletin No.: 77-71-53 Date: April, 1997 Subject: Chuggle/Surge on TCC Apply/No DTC's (Reflash PCM) Models: 1996-97 Chevrolet and GMC C/K, G Models with 5.7L Engine (VIN R - RPO L31) and HYDRA-MATIC 4L60-E Transmission (RPO M30) Condition Some owners of the above models may experience a chuggle/surge when TCC is applied under light throttle acceleration. Cause Engine inputs (Combustion events) exciting the vehicle platform/driveline or tire balance may be a contributing factor. Correction First ensure the most recent engine, not transmission calibration has been installed (Corp. # 76-65-04) and check tire balance. A new transmission calibration to correct chuggle/surge is available for use on vehicles with persistent concerns only. Important: This calibration will raise TCC engagement approximately 7-10 mph depending on application. This calibration should not be installed until the engine calibration listed above has been installed. Installation of this calibration may lead to decreased fuel economy due to TCC engagement at higher speeds. Reflash the Powertrain Control Module with the appropriate part numbers below. Refer to your Service Manual for proper procedure. Parts Information This new calibration will be available starting with the 1997 Disc 4 update. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J6355 Reflash Control Module Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Engine Control Module: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter Engine Control Module: All Technical Service Bulletins PROM - Reprogram Using Off Board Program Adapter File In Section: 6E - Engine Fuel & Emission Bulletin No.: 73-65-13 Date: March, 1997 INFORMATION Subject: Reprogramming Capability using the Off Board Programming Adapter Models: 1993-97 Passenger Cars and Trucks (Applicable Reprogrammable Vehicles) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Engine Control Module: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4638 The General Motors vehicles contain Electronically Reprogrammable Devices (i.e. PCM, VCM, ECM). These vehicles cannot be programmed through PROM replacement, however service programming capability is available through the Tech 1/1A, Tech 2 and Techline terminals via direct or remote programming. The Environmental Protection Agency (EPA) has requested that all new vehicle manufacturers ensure their dealers/retailers are aware that they are responsible for providing customers access to reprogramming services at a reasonable cost and in a timely manner. Although programming of controllers has become a common service practice at GM dealers/retailers, the EPA has received reports from consumers and the aftermarket repair industry that they were unable to purchase a new (programmed) Electronically Reprogrammable Device (ERD) over-the-counter. As a result, on August 1, 1995, the Federal Government issued a regulation requiring all manufacturers to make available reprogramming to the independent aftermarket by December 1, 1997. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Engine Control Module: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4639 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Engine Control Module: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4640 Today, the Off Board Programming Adapter (OBPA) is used to reprogram ERD's sold over-the-counter. For all practical purposes, the OBPA takes the place of the vehicle when the vehicle is not available. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Engine Control Module: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4641 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Engine Control Module: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4642 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Engine Control Module: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4643 The list of dealerships/retailers currently own the OBPA (see Attachments 1 - 3). These locations are equipped to provide over-the-counter preprogrammed ERD's. The hardware required to perform reprogramming in addition to the OBPA is a Techline terminal, Tech 1/1A and associated cables and adapters. THE TECH 2 SHOULD NOT BE USED WITH THE OBPA AT THIS TIME BECAUSE OF INADEQUATE OBPA GROUNDING. The current OBPA can support reprogramming on all late model General Motor's vehicles except: ^ Premium V-8's ^ 1996 Diesel Truck ^ Cadillac Catera Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Engine Control Module: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4644 ^ All 1997 programmable vehicles (requires use of the Tech 2) A modification to the OBPA is being offered by Kent-Moore to support these additional vehicles and to allow reprogramming using the Tech 2. The revisions to the OBPA for the Tech 2 is very important as the Tech 2 is the only tool used for service programming for 1997 and future vehicles. To have the modifications performed, contact Kent-Moore at (800) 345-2233. The revisions (part number J 41207 REV-C) are free of charge for GM dealerships/retailers. A dealership/retailer can purchase the OBPA by contacting Kent-Moore (part number J 41207-C). Support on how to use the OBPA is provided by the Techline Customer Support Center (TCSC) at (800) 828-6860 (English) or (800) 503-3222 (French). If you need to purchase an OBPA and/or cable, contact Kent-Moore at (800) 345-2233. The OBPA retails for $695.00 (includes all revisions 1-4) under part number J 41207-C. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 04-06-04-054B > Nov > 10 > Engine Controls - Aftermarket Accessory Usage Engine Control Module: All Technical Service Bulletins Engine Controls - Aftermarket Accessory Usage INFORMATION Bulletin No.: 04-06-04-054B Date: November 18, 2010 Subject: Info - Non-GM Parts and Accessories (Aftermarket) Models: 2011 and Prior GM Passenger Cars and Trucks Supercede: This bulletin is being revised to add model years and update to the new U.S. Fixed Operation Manager (FOM) and Canada Warranty Manager (WM) names. Please discard Corporate Bulletin Number 04-06-04-054A (Section 06 - Engine/Propulsion System). The recent rise and expansion of companies selling non-GM parts and accessories has made it necessary to issue this reminder to dealers regarding GM's policy on the use and installation of these aftermarket components. When a dealer is performing a repair under the New Vehicle Limited Warranty, they are required to use only genuine GM or GM-approved parts and accessories. This applies to all warranty repairs, special policy repairs or any repairs paid for by GM. Parts and accessories advertised as being "the same" as parts manufactured by GM, but not sold through GM, do not qualify for use in warranty repairs, special policy repairs or any repairs paid for by GM. During a warranty repair, if a GM original equipment part is not available through GM Customer Care and Aftersales (GM CC&A;), ACDelco(R) distributors, other GM dealers or approved sources, the dealer is to obtain comparable, non-GM parts and clearly indicate, in detail, on the repair order the circumstances surrounding why non-GM parts were used. The dealer must give customers written notice, prior to the sale or service, that such parts or accessories are not marketed or warranted by General Motors. It should also be noted that dealers modifying new vehicles and installing equipment, parts and accessories obtained from sources not authorized by GM are responsible for complying with the National Traffic and Motor Vehicle Safety Act. Certain non-approved parts or assemblies, installed by the dealer or its agent not authorized by GM, may result in a change to the vehicle's design characteristics and may affect the vehicle's ability to conform to federal law. Dealers must fully understand that non-GM approved parts may not have been validated, tested or certified for use. This puts the dealer at risk for potential liability in the event of a part or vehicle failure. If a GM part failure occurs as the result of the installation or use of a non-GM approved part, the warranty will not be honored. A good example of non-authorized modification of vehicles is the result of an ever increasing supply of aftermarket devices available to the customer, which claim to increase the horsepower and torque of the Duramax(TM) Diesel Engines. These include the addition of, but are not limited to one or more of the following modifications: - Propane injection - Nitrous oxide injection - Additional modules (black boxes) that connect to the vehicle wiring systems - Revised engine calibrations downloaded for the engine control module - Calibration modules which connect to the vehicle diagnostic connector - Modification to the engine turbocharger waste gate Although the installation of these devices, or modification of vehicle components, can increase engine horsepower and torque, they may also negatively affect the engine emissions, reliability and/or durability. In addition, other powertrain components, such as transmissions, universal joints, drive shafts, and front/rear axle components, can be stressed beyond design safety limits by the installation of these devices. General Motors does not support or endorse the use of devices or modifications that, when installed, increase the engine horsepower and torque. It is because of these unknown stresses, and the potential to alter reliability, durability and emissions performance, that GM has adopted a policy that prevents any UNAUTHORIZED dealer warranty claim submissions to any remaining warranty coverage, to the powertrain and driveline components whenever the presence of a non-GM (aftermarket) calibration is confirmed - even if the non-GM control module calibration is subsequently removed. Refer to the latest version of Bulletin 09-06-04-026 (V8 Gas Engines) or 06-06-01-007 (Duramax(TM) Diesel Engines) for more information on dealer requirements for calibration verification. These same policies apply as they relate to the use of non-GM accessories. Damage or failure from the use or installation of a non-GM accessory will not be covered under warranty. Failure resulting from the alteration or modification of the vehicle, including the cutting, welding or disconnecting of the vehicle's original equipment parts and components will void the warranty. Additionally, dealers will NOT be reimbursed or compensated by GM in the event of any legal inquiry at either the local, state or federal level that Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 04-06-04-054B > Nov > 10 > Engine Controls - Aftermarket Accessory Usage > Page 4650 results from the alteration or modification of a vehicle using non-GM approved parts or accessories. Dealers should be especially cautious of accessory companies that claim the installation of their product will not void the factory warranty. Many times these companies have even given direction on how to quickly disassemble the accessory in an attempt to preclude the manufacturer from finding out that is has been installed. Any suspect repairs should be reviewed by the Fixed Operations Manager (FOM), and in Canada by the Warranty Manager (WM) for appropriate repair direction. If it is decided that a goodwill repair is to be made on the vehicle, even with the installation of such non-GM approved components, the customer is to be made aware of General Motors position on this issue and is to sign the appropriate goodwill documentation required by General Motors. It is imperative for dealers to understand that by installing such devices, they are jeopardizing not only the warranty coverage, but also the performance and reliability of the customer's vehicle. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 83-81-32 > Sep > 98 > PCM Connector - Information on New Service Kits Engine Control Module: All Technical Service Bulletins PCM Connector - Information on New Service Kits File In Section: 8 - Chassis/Body Electrical Bulletin No.: 83-81-32 Date: September, 1998 INFORMATION Subject: New Powertrain Control Module (PCM) Connector Service Kits Models: 1996-99 All Passenger Cars except Geo and Catera Two new kits have been released to service the Powertrain Control Module (PCM) connector If the connector has been damaged during servicing. This PCM has an aluminum body and is usually mounted underhood. Kit (P/N 12167308) contains the 80 way connector body, the cover, two each of four different terminal retainers and 25 empty cavity plugs. No terminals are included. If terminals are needed, use P/N 12084913 for 0.35 mm and 0.50 mm wire and P/N 12084912 for 0.80 mm wire. These terminals are included in the terminal repair kit J 38125A or B, and replacements can be ordered from Kent-Moore. kit (P/N 12167313) contains one connector seal. Whenever the connector is unbolted from the aluminum body of the PCM, the seal can stick to the body, or may be twisted. This seal should be replaced whenever the connector is removed in service. Parts Information P/N Description 12167308 Kit, PCM Harness Repair 12167313 Seal Kit, PCM Connector 12084912 Terminal 12084913 Terminal Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter Engine Control Module: All Technical Service Bulletins PROM - Reprogram Using Off Board Program Adapter File In Section: 6E - Engine Fuel & Emission Bulletin No.: 73-65-13 Date: March, 1997 INFORMATION Subject: Reprogramming Capability using the Off Board Programming Adapter Models: 1993-97 Passenger Cars and Trucks (Applicable Reprogrammable Vehicles) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4659 The General Motors vehicles contain Electronically Reprogrammable Devices (i.e. PCM, VCM, ECM). These vehicles cannot be programmed through PROM replacement, however service programming capability is available through the Tech 1/1A, Tech 2 and Techline terminals via direct or remote programming. The Environmental Protection Agency (EPA) has requested that all new vehicle manufacturers ensure their dealers/retailers are aware that they are responsible for providing customers access to reprogramming services at a reasonable cost and in a timely manner. Although programming of controllers has become a common service practice at GM dealers/retailers, the EPA has received reports from consumers and the aftermarket repair industry that they were unable to purchase a new (programmed) Electronically Reprogrammable Device (ERD) over-the-counter. As a result, on August 1, 1995, the Federal Government issued a regulation requiring all manufacturers to make available reprogramming to the independent aftermarket by December 1, 1997. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4660 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4661 Today, the Off Board Programming Adapter (OBPA) is used to reprogram ERD's sold over-the-counter. For all practical purposes, the OBPA takes the place of the vehicle when the vehicle is not available. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4662 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4663 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4664 The list of dealerships/retailers currently own the OBPA (see Attachments 1 - 3). These locations are equipped to provide over-the-counter preprogrammed ERD's. The hardware required to perform reprogramming in addition to the OBPA is a Techline terminal, Tech 1/1A and associated cables and adapters. THE TECH 2 SHOULD NOT BE USED WITH THE OBPA AT THIS TIME BECAUSE OF INADEQUATE OBPA GROUNDING. The current OBPA can support reprogramming on all late model General Motor's vehicles except: ^ Premium V-8's ^ 1996 Diesel Truck ^ Cadillac Catera Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4665 ^ All 1997 programmable vehicles (requires use of the Tech 2) A modification to the OBPA is being offered by Kent-Moore to support these additional vehicles and to allow reprogramming using the Tech 2. The revisions to the OBPA for the Tech 2 is very important as the Tech 2 is the only tool used for service programming for 1997 and future vehicles. To have the modifications performed, contact Kent-Moore at (800) 345-2233. The revisions (part number J 41207 REV-C) are free of charge for GM dealerships/retailers. A dealership/retailer can purchase the OBPA by contacting Kent-Moore (part number J 41207-C). Support on how to use the OBPA is provided by the Techline Customer Support Center (TCSC) at (800) 828-6860 (English) or (800) 503-3222 (French). If you need to purchase an OBPA and/or cable, contact Kent-Moore at (800) 345-2233. The OBPA retails for $695.00 (includes all revisions 1-4) under part number J 41207-C. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > Page 4666 Engine Control Module: Locations Underhood Fuse-Relay Center Brake Pressure Modulator Valve Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > Page 4667 Vehicle Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions Engine Control Module: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4670 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4671 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4672 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4673 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4674 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4675 Engine Control Module: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4676 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4677 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4678 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4679 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4680 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4681 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4682 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4683 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4684 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4685 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4686 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4687 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4688 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4689 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4690 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4691 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4692 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4693 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4694 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4695 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4696 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4697 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4698 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4699 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4700 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4701 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4702 Engine Control Module: Connector Views Connector End View Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4703 Connector End View Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4704 Connector Terminal ID ECM/PCM/VCM Pinout Voltage The OE manufacture does not provide an ECM/PCM/VCM connector voltage pinout chart for this vehicle, only a function description. Connector End View Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4705 Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4706 Connector Terminal ID Connector End View Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4707 Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 4708 Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Page 4709 Engine Control Module: Service Precautions Control Module Service Precautions The control module is designed to withstand normal current draws associated with vehicle operations. Avoid overloading any circuit. When testing for opens or shorts, do not ground any of the control module circuits unless instructed. When testing for opens or shorts, do not apply voltage to any of the control module circuits unless instructed. Only test these circuits with a digital voltmeter J 39200, while the control module connectors remain connected to the control module. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Page 4710 Engine Control Module: Description and Operation GENERAL DESCRIPTION The VCM is located on the right hand side fenderwell. The VCM is the control center for the fuel, emissions, ignition, and automatic transmission control functions. The VCM constantly monitors the information from the various sensors. The VCM controls the component systems which affect the engine operation. The VCM alerts the driver through the Malfunction Indicator Lamp (MIL) or the antilock indicator lamp. The VCM stores the DTCs which identify the problem areas for the technician making repairs. Refer to Vehicle Control Module, for further information on using the diagnostic function of the VCM for engine operation. ^ Refer to Transmission for the diagnosis of the automatic transmission. ^ Refer to Anti-lock brakes for diagnosis of the brake system. The VCM in this vehicle is programmable. The only services allowed on the VCM is the control module replacement with the Knock Sensor (KS) calibrator Programmable Read Only Memory (PROM) transferred or the KS calibrator PROM only. The KS calibrator contains the up integrated knock sensor calibration. The VCM stores the 4 calibrations in the Electronically Erasable Programmable Read Only Memory (EEPROM). When replacing the VCM, programming the EEPROM and transferring the KS calibrator PROM to the new VCM is mandatory. Refer to the EEPROM Programming. Refer to VCM Replacement/Programming. See: Service and Repair The 4 calibrations required for the VCM are the Powertrain, the ABS, the VSS buffer, and the A/C. Each calibration has its own part number. Determine the correct calibrations for a particular vehicle based on the VIN number of the vehicle. MALFUNCTION INDICATOR LAMP (MIL) The MIL (Malfunction Indicator Lamp) is on the instrument panel. The MIL has the following functions: ^ The MIL informs the driver that a fault that affects the vehicle's emission levels has occurred. The owner should take the vehicle for service as soon as possible. ^ As a bulb and system check, the MIL (Malfunction Indicator Lamp) comes on with the key on and the engine not running. When the engine is started, the MIL turns off if no DTCs are set. When the MIL remains on while the engine is running, or when a malfunction is suspected due to a driveability or emissions problem, perform an On-Board Diagnostic (OBD) System Check. The procedures for these checks are given in engine controls. These checks expose faults which the technician may not detect if other diagnostics are performed first. DIAGNOSTIC INFORMATION The diagnostic Tables and functional checks are designed to locate a faulty circuit or component through a process of logical decisions. The Tables are prepared with the assumption that the vehicle functioned correctly at the time of assembly and that there are not multiple faults present. There is a continuous self-diagnosis on certain control functions. This diagnostic capability is complemented by the diagnostic procedures contained in this manual. The language of communicating the source of the malfunction is a system of diagnostic trouble codes. When a malfunction is detected by the control module, a diagnostic trouble code will set and the Malfunction Indicator Lamp (MIL) Malfunction Indicator Lamp will illuminate on some applications. VCM LEARNING ABILITY WARNING: Since the VCM is located under the hood, its connectors are sealed and cannot be backprobed as in the previous model years. Do not attempt to backprobe as a connector or seal damage could occur. The VCM's learning ability allows it to make corrections for minor variations in the fuel system in order to improve driveability. When the battery is disconnected for other repairs, the learning process resets. The driver my note a change in the vehicle's performance. In order to teach the vehicle ensure that the engine is at the operating temperature. Drive the vehicle at part throttle with a moderate acceleration and idle conditions until normal performance returns. INPUT INFORMATION The VCM processes the various input information. Then the VCM sends the necessary electrical responses to the control fuel delivery, the spark timing, and the other emission control systems. The input information interrelates to more than one output; therefore, if the one input fails, the failure can affect more than one system's operation. PROM (KS Module) This assembly contains an electronic Knock Sensor (KS) module. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Page 4711 MEMORY There are two types of memory storage within the VCM, EEPROM and RAM. EEPROM Electrically Erasable Programmable Read Only Memory (EEPROM) is a permanent memory that is physically soldered to the circuit boards within the VCM. The EEPROM contains the overall control algorithms. The EEPROM can be reprogrammed by using the scan tool. RAM Random Access Memory (RAM) is the microprocessor scratch pad. The processor can write into or read from this memory as needed. This memory is volatile and needs a constant supply of voltage to be retained. If the voltage is lost, the memory is lost. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Testing and Inspection > Component Tests and General Diagnostics Engine Control Module: Component Tests and General Diagnostics The approved procedure for diagnosing all powertrain control system faults is included in the Strategy Based Diagnostics. The preliminary checks and the Powertrain On-board Diagnostic System Check must be performed to successfully diagnose and repair the powertrain systems. To read and clear diagnostic trouble codes, use a scan tool. See: Testing and Inspection Use a scan tool to clear diagnostic trouble codes from the VCM memory. Diagnostic trouble codes can also be cleared by turning OFF the ignition and disconnecting the battery power from the VCM for 30 seconds, but this method will also cause all diagnostic information in the VCM memory to be cleared and all the diagnostic tests will have to be re-run. Since the VCM can have a failure which may affect only one circuit, following the approved diagnostic procedures will determine which circuit has a problem and where it is. If a diagnostic table indicates that the VCM connections or VCM is the cause of a problem and the VCM is replaced. but does not correct the problem, one of the following conditions may exist: ^ There is a problem with the VCM terminal connections. The diagnostic table will indicate that the VCM connections or VCM is the problem. The terminals may have to be removed from the VCM connector in order to check them properly. ^ The EEPROM program is not correct for the application. Incorrect components may cause a malfunction and may or may not set a DTC. ^ The problem is intermittent. This means that the problem is not present at the time the system is being checked. In this case, refer to Symptoms and make a careful visual and physical inspection of all suspected components and wiring associated with the affected system. See: Testing and Inspection ^ There is a shorted solenoid, relay coil, or harness. Solenoids and relays are turned ON and OFF by the VCM using internal electronic switches called drivers. Each driver is part of a group of seven called output driver modules. A shorted solenoid, relay coil, or harness will not damage the VCM but will cause the solenoid or relay to be inoperative. The J 34636 tester, or equivalent, provides a fast, accurate means of checking for a shorted coil or a short to battery voltage. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Service and Repair > Control Module Replacement Engine Control Module: Service and Repair Control Module Replacement VCM Harness Connections VCM Access Cover Removing Knock Sensor Module From PCM Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Service and Repair > Control Module Replacement > Page 4716 VCM REPLACEMENT/PROGRAMMING Service of the VCM consists of either replacement of VCM or reprogramming of the EEPROM. If the diagnostics call for replacement of the VCM, it will be necessary to transfer the PROM and program the EEPROM. NOTE: When replacing the production VCM with a service VCM (controller), it is important to transfer the broadcast code and production VCM number to the service VCM label. This will allow positive identification of VCM parts throughout the service life of the vehicle. Also transfer the PROM. CAUTION: To prevent internal VCM damage, the ignition must be OFF when disconnecting or reconnecting power to the VCM (for example, battery cable, VCM fuse, jumper cables, etc.). CAUTION: In order to prevent possible Electrostatic Discharge damage to the VCM, do not touch the connector pins or soldered components on the circuit board. VCM REPLACEMENT/PROGRAMMING (WITH KNOCK SENSOR (KS) CALIBRATION PROM) REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Remove the connectors from the VCM. 3. Remove the spring retainer off and over the rail of the VCM. Slide the VCM out of the bracket at an angle. 4. Remove the VCM access cover. 5. Remove the PROM/Knock Sensor (KS) module. 6. Inspect for the alignment notches of the KS Calibration PROM. 7. Carefully set it aside. 8. Do not open the KS Calibration PROM. 9. Remove the new VCM from the packaging. Check the service number in order to make sure it is the same as the defective VCM. 10. Remove the access cover. NOTE ^ The Knock Sensor (KS) module must be transferred to the replacement VCM. ^ The replacement VCM is supplied without a EEPROM program, the replacement VCM must be programmed before the vehicle will run. ^ Using the thumb and first finger, remove the KS Calibration PROM by gently squeezing each end of the blue KS Calibration PROM ^ Do not remove the cover of the KS Calibration PROM. Use of an unapproved KS Calibration PROM removal methods may cause damage to the KS Calibration PROM or the socket. INSTALLATION PROCEDURE NOTE: Press only on the ends of the KS Calibration PROM. Gently press on the KS Calibration PROM until it is firmly seated in the socket. Listen for the click. 1. Align the notches of the KS Calibration PROM with the notches in the KS Calibration PROM socket. 2. Install the KS Calibration PROM in the KS Calibration PROM socket. 3. Install the access cover on the VCM. 4. Install the VCM in the engine compartment. 5. Install the connectors to the VCM. 6. The MIL, antilock and brake lamps will continue to be enabled until the VCM is programmed. Once the programming is complete, the lamps will turn off and normal operation will occur. 7. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Service and Repair > Control Module Replacement > Page 4717 CAUTION: In order to prevent possible Electrostatic Discharge damage to the VCM, do not touch the connector pins or soldered components on the circuit board. 8. Proceed to the EEPROM programming. See: EEPROM Programming Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Engine Control Module > Component Information > Service and Repair > Control Module Replacement > Page 4718 Engine Control Module: Service and Repair EEPROM Programming CAUTION: The ignition should always be "off" when installing or removing the Vehicle Control Module (VCM) connectors. 1. Set-up: ^ Battery is charged. ^ Ignition is "ON." ^ Battery/cig. lighter Connection secure. ^ Data Link Connector (DLC). 2. Refer to up-to-date Techline terminal/equipment user's instructions. 3. If Vehicle Control Module (VCM) fails to program, do the following: ^ Check all VCM connections. ^ check Techline terminal/equipment for latest software version. ^ Try again to program the VCM. If it fails again, replace the VCM. Refer to VCM replacement. See: Control Module Replacement 4. Perform the Idle Air Control (IAC) valve reset procedure with the scan tool. use misc. test. 5. For a functional check perform one of the steps: ^ Use the Techline terminal and equipment in order to perform the On-Board Diagnostic (OBD) System Check ^ Refer to Powertrain OBD System Check. See: Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Specifications Idle Air Control (IAC) Valve: Specifications IAC valve attaching screws ................................................................................................................. ..................................................... 3.0 Nm (26 lb. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Specifications > Page 4722 Engine Side, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions Idle Air Control (IAC) Valve: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4725 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4726 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4727 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4728 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4729 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4730 Idle Air Control (IAC) Valve: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4731 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4732 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4733 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4734 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4735 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4736 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4737 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4738 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4739 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4740 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4741 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4742 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4743 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4744 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4745 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4746 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4747 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4748 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4749 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4750 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4751 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4752 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4753 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4754 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4755 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4756 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 4757 Idle Control System Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Page 4758 Idle Air Control (IAC) Valve: Description and Operation PURPOSE The purpose of the Idle Air Control (IAC) valve assembly is to control the engine idle speed, while preventing stalls due to changes in the engine load. OPERATION The IAC valve, mounted in the throttle body assembly, controls the bypass air around the throttle valve. By moving a conical valve known as a pintle IN toward the seat (to decrease air flow), or OUT away from the seat (to increase air flow), a controlled amount of air moves around the throttle valve. If engine speed is too low, more air is bypassed around the throttle valve in order to increase the RPM. If the engine speed is too high, less air is bypassed around the throttle valve in order to decrease the RPM. The VCM moves the IAC valve in small steps, called counts which can be measured using a scan tool connected to the Data Link Connector (DLC). During idle, the proper position of the IAC valve is calculated by the VCM. This position is based on battery voltage, engine coolant temperature, engine load, and engine RPM. If the RPM drops below specification and the throttle valve is closed, the VCM senses a near stall condition, and then the VCM calculates a new valve position in order to prevent stalling. If the IAC valve is disconnected and reconnected while the engine is running, the resulting idle RPM may be wrong. This will require the resetting of the IAC valve. After running the engine, the IAC valve will reset when the ignition is turned OFF. When servicing the IAC valve, it should only be disconnected or connected with the ignition OFF. If the VCM is without battery power for any reason, the programmed position of the IAC valve pintle is lost. The control module replaces the lost position with a default value. In order to return the IAC valve pintle to the correct position, see the Idle Learn Procedure. The IAC valve affects the idle characteristics of the vehicle. A fully retracted valve allows too much air into the manifold causing a high idle speed. A valve which is stuck closed allows too little air in the manifold, causing a low idle speed. If the valve is stuck part way open, the idle may be rough, and the idle will not respond to engine load changes. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Page 4759 Idle Air Control (IAC) Valve: Testing and Inspection If the Idle Air Control (IAC) valve is disconnected or connected when the engine is running, the idle RPM may be wrong. The IAC valve may be reset by turning the ignition switch ON for 10 seconds, OFF for 5 seconds. The IAC valve affects the idle characteristics of the engine as well as throttle follow-up to compensation for sudden throttle closing. If it is open fully too much air will be allowed in the manifold and idle speed will be high. If it is stuck closed, too little air will be allowed in the manifold, and idle speed will be too low. If it is stuck part way open, the idle may be rough, and will not respond to engine load changes. The diagnosis of Idle Air Control (IAC) can be found in VCM Outputs Diagnosis. See: Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Service and Repair > Idle Air Control (IAC) Reset Procedure Idle Air Control (IAC) Valve: Service and Repair Idle Air Control (IAC) Reset Procedure 1. Turn the ignition switch to the ON position for 5 seconds. 2. Turn the ignition switch to the OFF position for 10 seconds. 3. Start the engine. 4. Check for the proper idle operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Service and Repair > Idle Air Control (IAC) Reset Procedure > Page 4762 Idle Air Control (IAC) Valve: Service and Repair Idle Air Control (IAC) Valve Replacement Throttle Position Sensor Electrical Connector REMOVAL PROCEDURE 1. Remove the electrical connector from the Idle Air Control (IAC) valve Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Service and Repair > Idle Air Control (IAC) Reset Procedure > Page 4763 2. Remove the IAC valve attaching screws. CAUTION: If the IAC valve has been in service: DO NOT push or pull on the IAC valve pintle. The force required to move the pintle may damage the threads on the worm drive. Also, DO NOT soak the IAC valve in any liquid cleaner or solvent, as damage may result. 3. Remove the IAC valve assembly. 4. Remove the O-ring. CLEANING AND INSPECTION PROCEDURE 1. Clean the IAC valve O-ring sealing surface, pintle valve seat, and air passage. ^ Use the carburetor cleaner and a parts cleaning brush in order to remove carbon deposits. Follow instructions on the container. ^ Do not use a cleaner that contains methyl ethyl ketone, an extremely strong solvent and not necessary for this type of deposit. ^ Shiny spots on the pintle or seat are normal. They do not indicate misalignment or a bent pintle shaft. ^ If air passage has heavy deposits, remove the throttle body for complete cleaning. 2. Inspect the IAC valve O-ring for cuts, cracks, or distortion. Replace if damaged. NOTE: If installing a new IAC valve, replace with an identical part. The IAC valve pintle shape and diameter are designed for the specific application. 3. Measure the distance A between tip of IAC valve pintle and mounting flange. If greater than 28 mm, use finger pressure in order to slowly retract the pintle. The force required to retract the pintle of a new valve will not cause damage to the valve. MEASUREMENT PROCEDURE NOTE: If installing a new IAC valve, replace with an identical part. The AC valve pintle shape and diameter are designed for the specific application. Measure the distance A between tip of IAC valve pintle and mounting flange. If greater than 28 mm, use finger pressure in order to slowly retract the pintle. The force required to retract the pintle of a new valve will not cause damage to the valve. INSTALLATION PROCEDURE 2. Lubricate the IAC valve O-ring with clean engine oil. 2. Install the IAC valve assembly. 3. Install the attaching screws. Tighten ^ Tighten the IAC valve attaching screws to 3.0 Nm (26 lb. in.). 4. Install the electrical connector. 5. Reset the IAC valve pintle position. 5.1.Turn the ignition switch to the ON position for 5 seconds. 5.2.Turn the ignition switch to the OFF position for 10 seconds. 5.3.Start the engine. 5.4.Check for the proper idle operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Serial Data <--> [Information Bus] > Component Information > Description and Operation > Serial Data Communications Serial Data: Description and Operation Serial Data Communications Class II Serial Data U.S. Federal regulations require that all automobile manufacturers establish a common communications system. General Motors utilizes the "Class II" communications system. Each bit of information can have one of two lengths: long or short. This allows vehicle wiring to be reduced by the transmission and reception of multiple signals over a single wire. The messages carried on Class II data streams are also prioritized. In other words, if two messages attempt to establish communications on the data line at the same time, only the message with higher priority will continue. The device with the lower priority message must wait. The most significant result of this regulation is that it provides scan tool manufacturers with the capability of accessing data from any make or model vehicle sold in the United States. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Serial Data <--> [Information Bus] > Component Information > Description and Operation > Serial Data Communications > Page 4768 Serial Data: Description and Operation Circuit Operation A Scan Tool can be connected to the Data Link Connector (DLC), this allows the Scan Tool to communicate with the Diesel Powertrain Control Module (PCM) Gasoline Vehicle Control Module (VCM) the Diagnostic Energy Reserve Module (DERM), the Transfer Case Control Module or the Brake Pressure Modulator Valve. System operations can then be monitored for diagnostic purposes. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Serial Data <--> [Information Bus] > Component Information > Testing and Inspection > Initial Inspection and Diagnostic Overview Serial Data: Initial Inspection and Diagnostic Overview 1. CHECK condition of AUX PWR Fuse. If Fuse is open, LOCATE and REPAIR source of overload. REPLACE Fuse. 2. CHECK Grounds G103, G104, and G200 are clean and light. 3. CHECK for 12 volts at terminal 16 (CKT 840) of the DATA LINK CONNECTOR. REPAIR if necessary. 4. CHECK terminal 4, CKT 150 and terminal 5, CKT 451 for continuity to ground. REPAIR if necessary. DATA LINE(S) 1. Check for proper connection of Scan Tool to Data Link Connector (DLC). 2. Check for loose or missing terminals at DLC. 3. If VCM/PCM is not accessible with a Scan Tool, check for an open in PPL (1807) wire between component and DLC terminal 2. 4. If Brake Pressure Modulator Valve is not accessible with a Scan Tool, check for an open in TAN/WHT (799) wire between component and DLC terminal 12. 5. If Diagnostic Energy Reserve Module (DERM) not accessible with a Scan Tool, check for an open in TAN (800) wire between component and DLC terminal 9. 6. If Transfer Case Control Module is not accessible with a Scan Tool, check for an open in ORN (1568) wire between component and DLC terminal 13. 7. Check for proper installation of aftermarket electronic equipment that may affect the integrity of other systems. ^ CHECK for a broken (or partially broken) wire inside of the insulation which could cause system malfunction but prove "GOOD" in a Continuity/Voltage check with a system disconnected. These Circuits may be intermittent or resistive when loaded, and if possible, should be checked by monitoring for a Voltage drop with the system operational (under load). ^ CHECK for proper installation of aftermarket electronic equipment which may affect the integrity of other system (Refer "Troubleshooting Procedures"). See: Diagrams/Diagnostic Aids Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Serial Data <--> [Information Bus] > Component Information > Testing and Inspection > Initial Inspection and Diagnostic Overview > Page 4771 Serial Data: Symptom Related Diagnostic Procedures Scan Tool Will Not Communicate With Brake Pressure Modulator Valve (Part 1 Of 2) Scan Tool Will Not Communicate With Brake Pressure Modulator Valve (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Serial Data <--> [Information Bus] > Component Information > Testing and Inspection > Initial Inspection and Diagnostic Overview > Page 4772 Scan Tool Will Not Communicate With Components On Class-2 Data Line (Part 1 Of 2) Scan Tool Will Not Communicate With Components On Class-2 Data Line (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Serial Data <--> [Information Bus] > Component Information > Testing and Inspection > Initial Inspection and Diagnostic Overview > Page 4773 Scan Tool Will Not Communicate With Components On UART Data Line Scan Tool Will Not Communicate With Components On UART Data Line (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Serial Data <--> [Information Bus] > Component Information > Testing and Inspection > Initial Inspection and Diagnostic Overview > Page 4774 Scan Tool Will Not Communicate With Transfer Case Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Serial Data <--> [Information Bus] > Component Information > Testing and Inspection > Initial Inspection and Diagnostic Overview > Page 4775 Serial Data: Component Tests and General Diagnostics A Scan Tool can be connected to the Data Link Connector (DLC), this allows the Scan Tool to communicate with the Diesel Powertrain Control Module (PCM) Gasoline Vehicle Control Module (VCM) the Diagnostic Energy Reserve Module (DERM), the Transfer Case Control Module or the Brake Pressure Modulator Valve. System operations can then be monitored for diagnostic purposes. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Specifications Knock Sensor: Specifications Knock sensor ....................................................................................................................................... ....................................................... 19 Nm (14 lb. ft.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Specifications > Page 4779 Knock Sensor: Locations Engine View, Rear LH side of Engine Block, below Exhaust Manifold, forward of Starter Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions Knock Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4782 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4783 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4784 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4785 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4786 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4787 Knock Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4788 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4789 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4790 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4791 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4792 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4793 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4794 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4795 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4796 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4797 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4798 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4799 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4800 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4801 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4802 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4803 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4804 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4805 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4806 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4807 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4808 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4809 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4810 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4811 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4812 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4813 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4814 Knock Sensor Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Page 4815 Knock Sensor: Description and Operation Description The Knock Sensor (KS) system is used to detect engine detonation The VCM will retard the spark timing based on the signals from the KS module. The Knock Sensor(s) produce an AC voltage that is sent to the KS module. The amount of AC voltage produced is proportional to the amount of knock. Operation An operating engine produces a normal amount of engine mechanical vibration (Noise). The knock sensor(s) will produce an AC voltage signal from this Noise. When an engine is operating, the VCM will learn the minimum and maximum frequency of the noise the engine produces. When the VCM determines that this frequency is less than or greater than the expected amount, a knock sensor DTC will set. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Page 4816 Knock Sensor: Service and Repair Diagram Removal Procedure NOTE: The knock sensor is located in areas of the cylinder head. On most applications, the knock sensors are installed in a hole which is exposed to engine coolant. Care should be exercised when servicing these sensors. 1. Disconnect the negative battery cable. Important: On knock sensors which are mounted in the end of the cylinder head draining the cooling system will not be necessary. 2. Drain the cooling system. Refer to Draining and Filling Cooling System. 3. Remove the wiring harness connector from knock sensor. 4. Remove the knock sensor from cylinder head. Installation Procedure Important: Do not use silicon tape as this will insulate the sensor from the engine block. 2. After applying a water base caulk to the sensor threads, install the knock sensor into the cylinder head. Tighten ^ Tighten to 19 Nm (14 lb. ft.). 2. Connect the negative battery cable. 3. Refill cooling system if required. Refer to Draining and Filling Cooling System. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Knock Sensor Module > Component Information > Diagrams Knock Sensor Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition Malfunction Indicator Lamp: Customer Interest PROM - MIL ON, Poor Driveability Condition File In Section: 6E - Engine Fuel & Emission Bulletin No.: 76-65-04 Date: March, 1997 Subject: Malfunction Indicator Light (MIL) On, Poor Driveability Conditions (Perform Flash Calibration) Models: 1996-97 Chevrolet and GMC Light Duty Trucks 1996-97 Chevrolet Tiltmaster and GMC Forward W4 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L Engines (VINs X, W, M, R RPOs LF6, L35, L3O, L31) Condition An owner of the above mentioned vehicles may report that the Malfunction Indicator Light (MIL) is on and/or the vehicle has one or more of the following driveability conditions. 1. 5.7L (L31) only: Surge or chuggle at speeds of 42 to 65 MPH while at steady speed or under light to moderate acceleration with the TCC applied. 2. MIL on with DTC P0172 or P0175 stored but no reported driveability symptoms. 3. MIL on with TDC P1406 stored and rough engine or poor driveability symptoms. 4. When operating at altitudes above 5,000 feet, an audible spark knock noise is heard. 5. Hesitation and/or misfire during light cruise conditions due to ignition cross-fire with no DTC stored. This will only occur on V-6 engines with cam retard offset in excess of 26° and V-8's with cam retard offset in excess of 15°. 6. The MIL may be on and a DTC stored for an engine misfire but no misfire occurred. 7. Engine exhibits an idle speed surge or roll. 1996 Models Only 8. MIL on with DTC P0102 stored but no reported driveability symptoms. 9. 5.0L (L30) & 5.7L (L31) only: Difficult starting in extreme cold (below 0° F) conditions. 10. 5.7L (L31) only: Poorer than expected fuel economy when heavily loaded. 1997 Models Only 11. MIL on with DTC P0121 stored but no reported driveability symptoms. 12. C/K & S/T Models with either V-6 engine and manual transmission: An engine flare between shifts may be noted when the engine is cold. 13. Either V-6 engine and manual transmission: An engine flare between shifts may be noted when the engine is cold. 14. C/K, S/T and M/L Models equipped with L35 V-6 engine, an improvement to the vapor canister purge diagnostics is incorporated into the new calibrations so that the Tech II can turn on canister purge at idle speed. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 4828 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 4829 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 4830 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 4831 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 4832 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 4833 Follow the Strategy Based Diagnostic Steps for the customer's reported symptoms. If diagnosis does not reveal a cause, refer to the tables below for the applicable calibration change. Perform programming per the latest Techline information for programming procedures. Important The calibrations listed are FLASH calibrations and are not available from GMSPO. They are available on 1997 Techline CD Disc 5 and later. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J-6355 Use Published Labor Operation Time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition Malfunction Indicator Lamp: All Technical Service Bulletins PROM - MIL ON, Poor Driveability Condition File In Section: 6E - Engine Fuel & Emission Bulletin No.: 76-65-04 Date: March, 1997 Subject: Malfunction Indicator Light (MIL) On, Poor Driveability Conditions (Perform Flash Calibration) Models: 1996-97 Chevrolet and GMC Light Duty Trucks 1996-97 Chevrolet Tiltmaster and GMC Forward W4 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L Engines (VINs X, W, M, R RPOs LF6, L35, L3O, L31) Condition An owner of the above mentioned vehicles may report that the Malfunction Indicator Light (MIL) is on and/or the vehicle has one or more of the following driveability conditions. 1. 5.7L (L31) only: Surge or chuggle at speeds of 42 to 65 MPH while at steady speed or under light to moderate acceleration with the TCC applied. 2. MIL on with DTC P0172 or P0175 stored but no reported driveability symptoms. 3. MIL on with TDC P1406 stored and rough engine or poor driveability symptoms. 4. When operating at altitudes above 5,000 feet, an audible spark knock noise is heard. 5. Hesitation and/or misfire during light cruise conditions due to ignition cross-fire with no DTC stored. This will only occur on V-6 engines with cam retard offset in excess of 26° and V-8's with cam retard offset in excess of 15°. 6. The MIL may be on and a DTC stored for an engine misfire but no misfire occurred. 7. Engine exhibits an idle speed surge or roll. 1996 Models Only 8. MIL on with DTC P0102 stored but no reported driveability symptoms. 9. 5.0L (L30) & 5.7L (L31) only: Difficult starting in extreme cold (below 0° F) conditions. 10. 5.7L (L31) only: Poorer than expected fuel economy when heavily loaded. 1997 Models Only 11. MIL on with DTC P0121 stored but no reported driveability symptoms. 12. C/K & S/T Models with either V-6 engine and manual transmission: An engine flare between shifts may be noted when the engine is cold. 13. Either V-6 engine and manual transmission: An engine flare between shifts may be noted when the engine is cold. 14. C/K, S/T and M/L Models equipped with L35 V-6 engine, an improvement to the vapor canister purge diagnostics is incorporated into the new calibrations so that the Tech II can turn on canister purge at idle speed. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 4839 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 4840 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 4841 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 4842 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 4843 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 4844 Follow the Strategy Based Diagnostic Steps for the customer's reported symptoms. If diagnosis does not reveal a cause, refer to the tables below for the applicable calibration change. Perform programming per the latest Techline information for programming procedures. Important The calibrations listed are FLASH calibrations and are not available from GMSPO. They are available on 1997 Techline CD Disc 5 and later. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J-6355 Use Published Labor Operation Time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Page 4845 Malfunction Indicator Lamp: Service and Repair The CHECK ENGINE LAMP will be illuminated when the ignition switch is placed in the "ON" position. When the engine is started, the lamp should turn "OFF". If the lamp remains "ON" for 10 seconds or constantly after the engine is started, the self diagnosis system has detected a problem and has stored a code in the system Control Module. After diagnosis and repair, the ECM memory can be cleared of codes by removing the Control Module fuse or disconnecting the battery ground cable for approximately 30 seconds, with ignition switch in the "OFF" position. NOTE If battery ground cable is disconnected to clear codes, components such as clocks, electronically tuned radios etc., will have to be reset. - It is a good idea to record preset radio stations before disconnecting the negative battery cable. This will allow the stations to be reset as to not inconvenience the customer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Locations Engine Side, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions Manifold Absolute Pressure (MAP) Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4851 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4852 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4853 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4854 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4855 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4856 Manifold Absolute Pressure (MAP) Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4857 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4858 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4859 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4860 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4861 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4862 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4863 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4864 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4865 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4866 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4867 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4868 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4869 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4870 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4871 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4872 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4873 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4874 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4875 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4876 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4877 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4878 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4879 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4880 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4881 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4882 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 4883 MAP System Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Page 4884 Manifold Absolute Pressure (MAP) Sensor: Description and Operation Manifold Absolute Pressure (MAP) Sensor PURPOSE The Manifold Absolute Pressure (MAP) sensor responds to changes in the intake manifold pressure. The pressure changes as a result of engine load and speed. The map sensor converts this to a voltage output. OPERATION A closed throttle on engine coast down would produce a relatively low MAP output voltage. A wide open throttle would produce a high MAP output voltage. This high output voltage is produced because the pressure inside the manifold is the same as outside the manifold. The MAP is inversely proportional to what is measured on a vacuum gage. The MAP sensor is used for the following: ^ Altitude determination. ^ Ignition timing control. ^ Exhaust Gas Recirculation (EGR) diagnostic. ^ Speed density fuel management default. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Page 4885 Manifold Absolute Pressure (MAP) Sensor: Testing and Inspection When the VCM detects a malfunction in the MAP sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0106 circuit performance. ^ DTC P0107 circuit low. ^ DTC P0108 circuit high. ^ DTC P1106 intermittent circuit high. ^ DTC P1107 intermittent circuit low. Refer to System Diagnosis / Diagnostic Charts for testing information. See: Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Page 4886 Manifold Absolute Pressure (MAP) Sensor: Service and Repair MAP Sensor NOTE: Other than checking for loose hoses and electrical connections, the only service possible is unit replacement, if the diagnosis shows the sensor to be faulty. REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Disconnect the vacuum harness assembly. 3. Disconnect the electrical connector releasing locking tab. 4. Remove the bolts or release lock tabs and remove the sensor. INSTALLATION PROCEDURE 1. Install the bolts or snap sensor on bracket. 2. Connect the electrical connector. 3. Connect the vacuum harness. 4. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Quad Driver <--> [Output Driver] > Component Information > Locations Quad Driver: Locations Quad/Output drivers are hard wired onto the ECM/PCM/VCM. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Quad Driver <--> [Output Driver] > Component Information > Locations > Page 4890 Quad Driver: Description and Operation Quad/Output Driver Module The Control Module in this vehicle controls most components with electronic switches which complete a ground circuit when turned on. When the switches are arranged in groups of 4, they can independently control up to 4 outputs and are called Quad Drivers. When the switches are arranged in groups of 7, they can independently control up to 7 outputs and are called Output Drivers. Not all outputs are always used. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Quad Driver <--> [Output Driver] > Component Information > Locations > Page 4891 Quad Driver: Testing and Inspection Little or no quad driver testing was supplied by the manufacturer. The engine module decides when to turn each switch of the driver "ON". Even though some models will set codes, in the end, if you want to check the driver itself, you'll need: 1. To use a scantool to command the suspected driver switch to energize (ground) the circuit, while checking with a test light, 2. To operate the vehicle in a way that should cause the suspected portion of the driver to switch "ON". On the up side, since the early 90's, most driver load circuits utilized circuit breakers. This protected most drivers and engine models from burning up when the circuit was overloaded. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Quad Driver <--> [Output Driver] > Component Information > Locations > Page 4892 Quad Driver: Service and Repair Quad/Output drivers are hard wired onto the ECM/PCM/VCM, and can't be serviced separately. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Oxygen Sensor - Locations in Various Exhaust Systems Oxygen Sensor: Technical Service Bulletins Oxygen Sensor - Locations in Various Exhaust Systems File In Section: 6E - Engine Fuel & Emission Bulletin No.: 67-65-40 Date: March, 1997 INFORMATION Subject: Pictorial of Oxygen Sensor Designations in Various Exhaust Systems Configurations Models: 1996-97 Passenger Cars, Geos and Trucks Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Oxygen Sensor - Locations in Various Exhaust Systems > Page 4897 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Oxygen Sensor - Locations in Various Exhaust Systems > Page 4898 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Oxygen Sensor - Locations in Various Exhaust Systems > Page 4899 Pictorials of the designation of oxygen sensors in General Motors vehicles. There has been some confusion relative to OBD II oxygen sensor designation. The intent of this bulletin is to eliminate misdiagnosis of those oxygen sensors due to misidentification. When using Section 6E of the Service Manual, this chart can help locate the appropriate bank and sensor for the diagnostic. For "V" engines; BANK 1 is always on the side of the engine with the number 1 cylinder (odd cylinders), and BANK 2 is always on the side of the engine where the number 2 cylinder (even cylinders) is located. Just a reminder, the OBD II P-codes, technician observations and customer comments are all to be recorded on the repair order in accordance with article 1.6.2G of the GM Service Policies and Procedures Manual. Use the approved labor operation for the sensors replaced. J 6372 is used for engine out sensors. Labor Operation J 6380 is for the pre-sensor (the sensor just in front of the catalytic converter) and the post sensor (the sensor behind the catalytic converter). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Page 4900 Oxygen Sensor: Specifications Heated Oxygen Sensor (HO2S) .......................................................................................................... ...................................................... 41 Nm (30 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations Oxygen Sensor: Component Locations Light Duty Vehicles Bulletin No.: 67-65-40 PICTORIALS OF THE DESIGNATION OF OXYGEN SENSORS There has been some confusion relative to OBD II oxygen sensor designation. The intent of this article is to eliminate misdiagnosis of those oxygen sensors due to mis-identification. This chart can help locate the appropriate bank and sensor for the diagnostic. NOTE: For "V" engines; BANK 1 is always on the side of the engine with the number 1 cylinder (odd cylinders), and BANK 2 is always on the side of the engine where the number 2 cylinder (even cylinders) is located. Heavy Duty Vehicles Bulletin No.: 67-65-40 PICTORIALS OF THE DESIGNATION OF OXYGEN SENSORS Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 4903 There has been some confusion relative to OBD II oxygen sensor designation. The intent of this article is to eliminate misdiagnosis of those oxygen sensors due to mis-identification. This chart can help locate the appropriate bank and sensor for the diagnostic. NOTE: For "V" engines; BANK 1 is always on the side of the engine with the number 1 cylinder (odd cylinders), and BANK 2 is always on the side of the engine where the number 2 cylinder (even cylinders) is located. 5-Speed Manual Transmission (MW3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 4904 Oxygen Sensor: Connector Locations Engine View, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 4905 Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 4906 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 4907 5-Speed Manual Transmission W/4WD 5-Speed Manual Transmission (MW3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 4908 5-Speed Manual Transmission (MW3) 5-Speed Manual Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 4909 Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions Oxygen Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4912 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4913 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4914 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4915 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4916 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4917 Oxygen Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4918 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4919 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4920 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4921 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4922 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4923 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4924 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4925 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4926 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4927 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4928 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4929 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4930 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4931 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4932 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4933 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4934 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4935 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4936 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4937 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4938 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4939 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4940 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4941 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4942 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4943 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4944 Oxygen Sensor: Connector Views C107: Engine HARN To Oxygen Sensor HARN Oxygen Sensor RH, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 4945 HO2S Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Page 4946 Oxygen Sensor: Description and Operation Heated Oxygen Sensor (HO2S) Cutaway OPERATION To control emissions of Hydrocarbons (HO), Carbon Monoxide (CO), and Oxides of Nitrogen (NOx), a three-way catalytic converter is used. The catalyst within the converter promotes a chemical reaction which oxidizes the HO and CO present in the exhaust gas, converting them into harmless water vapor and carbon dioxide. The catalyst also reduces NOx, converting it to nitrogen. The VCM has the ability to monitor this process using the Bank 1 Sensor 2 and the Bank 2 Sensor 2 heated oxygen sensors. The Bank 1 Sensor 2 sensor produces an output signal which indicates the amount of oxygen present in the exhaust gas entering the three way catalytic converter. The Bank 2 Sensor 2 sensor produces an output signal which indicates the oxygen storage capacity of the catalyst; this in turn indicates the catalyst ability to convert exhaust gases efficiently. If the catalyst is operating efficiently, the Bank 1 Sensor 2 sensor will produce a far more active signal than that produced by the Bank 2 Sensor 2 sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Page 4947 The catalyst monitor sensors operate the same as the fuel control sensors. Although the Bank 1 Sensor 2 and Bank 2 Sensor 2 sensors main function is catalyst monitoring, they also play a limited role in fuel control. If a sensor output indicates a voltage either above or below the 450 millivolt bias voltage for an extended period of time, the VCM will make a slight adjustment to fuel trim to ensure that fuel delivery is correct for catalyst monitoring. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Testing and Inspection > Heated Oxygen Sensor (HO2S 1) Testing Oxygen Sensor: Testing and Inspection Heated Oxygen Sensor (HO2S 1) Testing The heated oxygen sensor circuit, if open, should set a Diagnostic Trouble Code (DTC) P0134 and the Scan tool will display a constant voltage between 350-550 mV. A constant voltage below 250 mV in the sensor circuit should set DTC P0131, while a constant voltage above 750 mV in the circuit should set DTC P0132. DTC P0131 and DTC P0132 could also be set as a result of fuel system problems. Refer to DTC P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1 or DTC P0132 HO2S Circuit High Voltage Bank 1 Sensor 1 or DTC P0134 HO2S Insufficient Activity Bank 1 Sensor 1. Refer to System Diagnosis / Diagnostic Charts for testing information. See: Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Testing and Inspection > Heated Oxygen Sensor (HO2S 1) Testing > Page 4950 Oxygen Sensor: Testing and Inspection Heated Oxygen Sensor (HO2S 2) Testing A problem with the HO2S 2 electrical circuits should set Diagnostic Trouble Code (DTC) P0137, P0138 or P0140, depending on the specific condition. If the catalyst is functioning correctly, the HO2S 2 signal will be far less active than that produced by HO2S 1. If a problem exists which causes the VCM to detect excessive HO2S 2 activity outside of an acceptable range for an extended period of time, the VCM will set DTC P0420, indicating that the three-way catalytic converter [prime ]s oxygen storage capacity is below a threshold considered acceptable. Refer to DTC P0137 HO2S Circuit Low Voltage Bank 1 Sensor 2 or DTC P0138 HO2S Circuit High Voltage Bank 1 Sensor 2 or DTC P0140 HO2S Insufficient Activity Bank 1 Sensor 2 or DTC P0420 TWC System Low Efficiency Bank 1. Refer to System Diagnosis / Diagnostic Charts for testing information. See: Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Testing and Inspection > Page 4951 Oxygen Sensor: Service and Repair Heated Oxygen Sensor (HO2S) Electrical Connector Heated Oxygen Sensor (HO2S) REMOVAL PROCEDURE CAUTION: The Heated Oxygen Sensor (HO2S) and the Oxygen Sensor use a permanently attached pigtail and connector. Do not remove this pigtail from the Heated Oxygen Sensor. Damage or the removal of the pigtail or the connector could affect the proper operation of the sensor. CAUTION: Take care when handling the HO2S. Keep the in-line electrical connector and the louvered end free of grease, dirt, or other contaminants. Also avoid using cleaning solvents of any type. Do not drop or roughly handle the HO2S. CAUTION: If the heated oxygen sensor pigtail wiring, connector or terminal is damaged, the entire oxygen sensor assembly must be replaced. Do Not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. CAUTION: This clean air reference is obtained by way of the oxygen sensor signal and heater wires. Any attempt to repair the wires, connectors, or terminals could result in the obstruction of the air reference and degraded sensor performance. The following guidelines should be used when servicing the heated oxygen sensor: ^ Do Not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. ^ The sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems, ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do Not remove or defeat the oxygen sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will cause poor engine performance. ^ To prevent damage due to water intrusion. be sure that the peripheral seal remains intact on the vehicle harness connector. The engine harness Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Oxygen Sensor > Component Information > Testing and Inspection > Page 4952 may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. CAUTION: The Heated Oxygen Sensor (HO2S) may be difficult to remove when the engine temperature is below 48°C (120°F). Excessive force may damage the threads in the exhaust manifold or the exhaust pipe. 1. Disconnect the negative battery cable. 2. Remove the electrical connector by releasing the locking tab. 3. Carefully back out the heated oxygen sensor. INSTALLATION PROCEDURE NOTE: A special anti-seize compound is used on the Heated Oxygen Sensor (HO2S) threads. The compound consists of liquid graphite and glass beads. The graphite tends to burn away, but the glass beads remain, making the sensor easier to remove. New, or service replacement sensors already have the compound applied to the threads. If the sensor is removed from an engine and if for any reason it is to be reinstalled, the threads must have anti-seize compound applied before the reinstallation. 1. Coat the threads of the oxygen sensor with anti-seize compound GM P/N 5613695 or the equivalent if necessary. 2. Install the sensor. Tighten ^ Tighten the sensor to 41 Nm (30 lb. ft.). 3. Install the electrical connector. 4. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > Customer Interest: > 77-71-53 > Apr > 97 > A/T - Chuggle/Surge on TCC Apply/No DTC's Engine Control Module: Customer Interest A/T - Chuggle/Surge on TCC Apply/No DTC's File In Section: 7 - Transmission Bulletin No.: 77-71-53 Date: April, 1997 Subject: Chuggle/Surge on TCC Apply/No DTC's (Reflash PCM) Models: 1996-97 Chevrolet and GMC C/K, G Models with 5.7L Engine (VIN R - RPO L31) and HYDRA-MATIC 4L60-E Transmission (RPO M30) Condition Some owners of the above models may experience a chuggle/surge when TCC is applied under light throttle acceleration. Cause Engine inputs (Combustion events) exciting the vehicle platform/driveline or tire balance may be a contributing factor. Correction First ensure the most recent engine, not transmission calibration has been installed (Corp. # 76-65-04) and check tire balance. A new transmission calibration to correct chuggle/surge is available for use on vehicles with persistent concerns only. Important: This calibration will raise TCC engagement approximately 7-10 mph depending on application. This calibration should not be installed until the engine calibration listed above has been installed. Installation of this calibration may lead to decreased fuel economy due to TCC engagement at higher speeds. Reflash the Powertrain Control Module with the appropriate part numbers below. Refer to your Service Manual for proper procedure. Parts Information This new calibration will be available starting with the 1997 Disc 4 update. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J6355 Reflash Control Module Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 04-06-04-054B > Nov > 10 > Engine Controls - Aftermarket Accessory Usage Engine Control Module: All Technical Service Bulletins Engine Controls - Aftermarket Accessory Usage INFORMATION Bulletin No.: 04-06-04-054B Date: November 18, 2010 Subject: Info - Non-GM Parts and Accessories (Aftermarket) Models: 2011 and Prior GM Passenger Cars and Trucks Supercede: This bulletin is being revised to add model years and update to the new U.S. Fixed Operation Manager (FOM) and Canada Warranty Manager (WM) names. Please discard Corporate Bulletin Number 04-06-04-054A (Section 06 - Engine/Propulsion System). The recent rise and expansion of companies selling non-GM parts and accessories has made it necessary to issue this reminder to dealers regarding GM's policy on the use and installation of these aftermarket components. When a dealer is performing a repair under the New Vehicle Limited Warranty, they are required to use only genuine GM or GM-approved parts and accessories. This applies to all warranty repairs, special policy repairs or any repairs paid for by GM. Parts and accessories advertised as being "the same" as parts manufactured by GM, but not sold through GM, do not qualify for use in warranty repairs, special policy repairs or any repairs paid for by GM. During a warranty repair, if a GM original equipment part is not available through GM Customer Care and Aftersales (GM CC&A;), ACDelco(R) distributors, other GM dealers or approved sources, the dealer is to obtain comparable, non-GM parts and clearly indicate, in detail, on the repair order the circumstances surrounding why non-GM parts were used. The dealer must give customers written notice, prior to the sale or service, that such parts or accessories are not marketed or warranted by General Motors. It should also be noted that dealers modifying new vehicles and installing equipment, parts and accessories obtained from sources not authorized by GM are responsible for complying with the National Traffic and Motor Vehicle Safety Act. Certain non-approved parts or assemblies, installed by the dealer or its agent not authorized by GM, may result in a change to the vehicle's design characteristics and may affect the vehicle's ability to conform to federal law. Dealers must fully understand that non-GM approved parts may not have been validated, tested or certified for use. This puts the dealer at risk for potential liability in the event of a part or vehicle failure. If a GM part failure occurs as the result of the installation or use of a non-GM approved part, the warranty will not be honored. A good example of non-authorized modification of vehicles is the result of an ever increasing supply of aftermarket devices available to the customer, which claim to increase the horsepower and torque of the Duramax(TM) Diesel Engines. These include the addition of, but are not limited to one or more of the following modifications: - Propane injection - Nitrous oxide injection - Additional modules (black boxes) that connect to the vehicle wiring systems - Revised engine calibrations downloaded for the engine control module - Calibration modules which connect to the vehicle diagnostic connector - Modification to the engine turbocharger waste gate Although the installation of these devices, or modification of vehicle components, can increase engine horsepower and torque, they may also negatively affect the engine emissions, reliability and/or durability. In addition, other powertrain components, such as transmissions, universal joints, drive shafts, and front/rear axle components, can be stressed beyond design safety limits by the installation of these devices. General Motors does not support or endorse the use of devices or modifications that, when installed, increase the engine horsepower and torque. It is because of these unknown stresses, and the potential to alter reliability, durability and emissions performance, that GM has adopted a policy that prevents any UNAUTHORIZED dealer warranty claim submissions to any remaining warranty coverage, to the powertrain and driveline components whenever the presence of a non-GM (aftermarket) calibration is confirmed - even if the non-GM control module calibration is subsequently removed. Refer to the latest version of Bulletin 09-06-04-026 (V8 Gas Engines) or 06-06-01-007 (Duramax(TM) Diesel Engines) for more information on dealer requirements for calibration verification. These same policies apply as they relate to the use of non-GM accessories. Damage or failure from the use or installation of a non-GM accessory will not be covered under warranty. Failure resulting from the alteration or modification of the vehicle, including the cutting, welding or disconnecting of the vehicle's original equipment parts and components will void the warranty. Additionally, dealers will NOT be reimbursed or compensated by GM in the event of any legal inquiry at either the local, state or federal level that Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 04-06-04-054B > Nov > 10 > Engine Controls - Aftermarket Accessory Usage > Page 4967 results from the alteration or modification of a vehicle using non-GM approved parts or accessories. Dealers should be especially cautious of accessory companies that claim the installation of their product will not void the factory warranty. Many times these companies have even given direction on how to quickly disassemble the accessory in an attempt to preclude the manufacturer from finding out that is has been installed. Any suspect repairs should be reviewed by the Fixed Operations Manager (FOM), and in Canada by the Warranty Manager (WM) for appropriate repair direction. If it is decided that a goodwill repair is to be made on the vehicle, even with the installation of such non-GM approved components, the customer is to be made aware of General Motors position on this issue and is to sign the appropriate goodwill documentation required by General Motors. It is imperative for dealers to understand that by installing such devices, they are jeopardizing not only the warranty coverage, but also the performance and reliability of the customer's vehicle. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 83-81-32 > Sep > 98 > PCM Connector - Information on New Service Kits Engine Control Module: All Technical Service Bulletins PCM Connector - Information on New Service Kits File In Section: 8 - Chassis/Body Electrical Bulletin No.: 83-81-32 Date: September, 1998 INFORMATION Subject: New Powertrain Control Module (PCM) Connector Service Kits Models: 1996-99 All Passenger Cars except Geo and Catera Two new kits have been released to service the Powertrain Control Module (PCM) connector If the connector has been damaged during servicing. This PCM has an aluminum body and is usually mounted underhood. Kit (P/N 12167308) contains the 80 way connector body, the cover, two each of four different terminal retainers and 25 empty cavity plugs. No terminals are included. If terminals are needed, use P/N 12084913 for 0.35 mm and 0.50 mm wire and P/N 12084912 for 0.80 mm wire. These terminals are included in the terminal repair kit J 38125A or B, and replacements can be ordered from Kent-Moore. kit (P/N 12167313) contains one connector seal. Whenever the connector is unbolted from the aluminum body of the PCM, the seal can stick to the body, or may be twisted. This seal should be replaced whenever the connector is removed in service. Parts Information P/N Description 12167308 Kit, PCM Harness Repair 12167313 Seal Kit, PCM Connector 12084912 Terminal 12084913 Terminal Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 77-71-53 > Apr > 97 > A/T - Chuggle/Surge on TCC Apply/No DTC's Engine Control Module: All Technical Service Bulletins A/T - Chuggle/Surge on TCC Apply/No DTC's File In Section: 7 - Transmission Bulletin No.: 77-71-53 Date: April, 1997 Subject: Chuggle/Surge on TCC Apply/No DTC's (Reflash PCM) Models: 1996-97 Chevrolet and GMC C/K, G Models with 5.7L Engine (VIN R - RPO L31) and HYDRA-MATIC 4L60-E Transmission (RPO M30) Condition Some owners of the above models may experience a chuggle/surge when TCC is applied under light throttle acceleration. Cause Engine inputs (Combustion events) exciting the vehicle platform/driveline or tire balance may be a contributing factor. Correction First ensure the most recent engine, not transmission calibration has been installed (Corp. # 76-65-04) and check tire balance. A new transmission calibration to correct chuggle/surge is available for use on vehicles with persistent concerns only. Important: This calibration will raise TCC engagement approximately 7-10 mph depending on application. This calibration should not be installed until the engine calibration listed above has been installed. Installation of this calibration may lead to decreased fuel economy due to TCC engagement at higher speeds. Reflash the Powertrain Control Module with the appropriate part numbers below. Refer to your Service Manual for proper procedure. Parts Information This new calibration will be available starting with the 1997 Disc 4 update. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J6355 Reflash Control Module Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter Engine Control Module: All Technical Service Bulletins PROM - Reprogram Using Off Board Program Adapter File In Section: 6E - Engine Fuel & Emission Bulletin No.: 73-65-13 Date: March, 1997 INFORMATION Subject: Reprogramming Capability using the Off Board Programming Adapter Models: 1993-97 Passenger Cars and Trucks (Applicable Reprogrammable Vehicles) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4980 The General Motors vehicles contain Electronically Reprogrammable Devices (i.e. PCM, VCM, ECM). These vehicles cannot be programmed through PROM replacement, however service programming capability is available through the Tech 1/1A, Tech 2 and Techline terminals via direct or remote programming. The Environmental Protection Agency (EPA) has requested that all new vehicle manufacturers ensure their dealers/retailers are aware that they are responsible for providing customers access to reprogramming services at a reasonable cost and in a timely manner. Although programming of controllers has become a common service practice at GM dealers/retailers, the EPA has received reports from consumers and the aftermarket repair industry that they were unable to purchase a new (programmed) Electronically Reprogrammable Device (ERD) over-the-counter. As a result, on August 1, 1995, the Federal Government issued a regulation requiring all manufacturers to make available reprogramming to the independent aftermarket by December 1, 1997. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4981 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4982 Today, the Off Board Programming Adapter (OBPA) is used to reprogram ERD's sold over-the-counter. For all practical purposes, the OBPA takes the place of the vehicle when the vehicle is not available. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4983 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4984 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4985 The list of dealerships/retailers currently own the OBPA (see Attachments 1 - 3). These locations are equipped to provide over-the-counter preprogrammed ERD's. The hardware required to perform reprogramming in addition to the OBPA is a Techline terminal, Tech 1/1A and associated cables and adapters. THE TECH 2 SHOULD NOT BE USED WITH THE OBPA AT THIS TIME BECAUSE OF INADEQUATE OBPA GROUNDING. The current OBPA can support reprogramming on all late model General Motor's vehicles except: ^ Premium V-8's ^ 1996 Diesel Truck ^ Cadillac Catera Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 4986 ^ All 1997 programmable vehicles (requires use of the Tech 2) A modification to the OBPA is being offered by Kent-Moore to support these additional vehicles and to allow reprogramming using the Tech 2. The revisions to the OBPA for the Tech 2 is very important as the Tech 2 is the only tool used for service programming for 1997 and future vehicles. To have the modifications performed, contact Kent-Moore at (800) 345-2233. The revisions (part number J 41207 REV-C) are free of charge for GM dealerships/retailers. A dealership/retailer can purchase the OBPA by contacting Kent-Moore (part number J 41207-C). Support on how to use the OBPA is provided by the Techline Customer Support Center (TCSC) at (800) 828-6860 (English) or (800) 503-3222 (French). If you need to purchase an OBPA and/or cable, contact Kent-Moore at (800) 345-2233. The OBPA retails for $695.00 (includes all revisions 1-4) under part number J 41207-C. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON Torque Converter Clutch Solenoid: All Technical Service Bulletins A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-023B Date: March, 2002 TECHNICAL Subject: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1999-2000 Cadillac Escalade 1996-2000 Chevrolet Camaro, Corvette 1996-2000 Pontiac Firebird 1996-2000 Chevrolet and GMC Light Duty Truck Models 1996-2000 Oldsmobile Bravada with 4L60-E Automatic Transmission (RPO M30) Built Prior to January 15, 2000 (Julian Date 0015) This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 Transmission/Transaxle). Condition Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated. Diagnosis Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs. The scan tool may show a DTC P1870 set as a history code. A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93° C (200°F). Cause The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply. Important: ^ DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code. ^ When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result. ^ This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle). ^ When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code. ^ When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL). Correction Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 4992 regulator and isolator valves. Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body. ^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears). ^ The torque converter is not blue or overheated. ^ The transmission fluid is not burned or has no burned odor ^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 4993 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 4999 regulator and isolator valves. Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body. ^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears). ^ The torque converter is not blue or overheated. ^ The transmission fluid is not burned or has no burned odor ^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > All Other Service Bulletins for Engine Control Module: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 5000 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > Page 5001 Engine Control Module: Locations Underhood Fuse-Relay Center Brake Pressure Modulator Valve Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Technical Service Bulletins > Page 5002 Vehicle Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions Engine Control Module: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5005 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5006 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5007 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5008 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5009 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5010 Engine Control Module: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5011 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5012 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5013 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5014 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5015 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5016 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5017 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5018 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5019 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5020 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5021 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5022 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5023 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5024 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5025 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5026 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5027 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5028 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5029 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5030 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5031 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5032 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5033 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5034 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5035 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5036 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5037 Engine Control Module: Connector Views Connector End View Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5038 Connector End View Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5039 Connector Terminal ID ECM/PCM/VCM Pinout Voltage The OE manufacture does not provide an ECM/PCM/VCM connector voltage pinout chart for this vehicle, only a function description. Connector End View Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5040 Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5041 Connector Terminal ID Connector End View Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5042 Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 5043 Connector Terminal ID Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Page 5044 Engine Control Module: Service Precautions Control Module Service Precautions The control module is designed to withstand normal current draws associated with vehicle operations. Avoid overloading any circuit. When testing for opens or shorts, do not ground any of the control module circuits unless instructed. When testing for opens or shorts, do not apply voltage to any of the control module circuits unless instructed. Only test these circuits with a digital voltmeter J 39200, while the control module connectors remain connected to the control module. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Page 5045 Engine Control Module: Description and Operation GENERAL DESCRIPTION The VCM is located on the right hand side fenderwell. The VCM is the control center for the fuel, emissions, ignition, and automatic transmission control functions. The VCM constantly monitors the information from the various sensors. The VCM controls the component systems which affect the engine operation. The VCM alerts the driver through the Malfunction Indicator Lamp (MIL) or the antilock indicator lamp. The VCM stores the DTCs which identify the problem areas for the technician making repairs. Refer to Vehicle Control Module, for further information on using the diagnostic function of the VCM for engine operation. ^ Refer to Transmission for the diagnosis of the automatic transmission. ^ Refer to Anti-lock brakes for diagnosis of the brake system. The VCM in this vehicle is programmable. The only services allowed on the VCM is the control module replacement with the Knock Sensor (KS) calibrator Programmable Read Only Memory (PROM) transferred or the KS calibrator PROM only. The KS calibrator contains the up integrated knock sensor calibration. The VCM stores the 4 calibrations in the Electronically Erasable Programmable Read Only Memory (EEPROM). When replacing the VCM, programming the EEPROM and transferring the KS calibrator PROM to the new VCM is mandatory. Refer to the EEPROM Programming. Refer to VCM Replacement/Programming. See: Service and Repair The 4 calibrations required for the VCM are the Powertrain, the ABS, the VSS buffer, and the A/C. Each calibration has its own part number. Determine the correct calibrations for a particular vehicle based on the VIN number of the vehicle. MALFUNCTION INDICATOR LAMP (MIL) The MIL (Malfunction Indicator Lamp) is on the instrument panel. The MIL has the following functions: ^ The MIL informs the driver that a fault that affects the vehicle's emission levels has occurred. The owner should take the vehicle for service as soon as possible. ^ As a bulb and system check, the MIL (Malfunction Indicator Lamp) comes on with the key on and the engine not running. When the engine is started, the MIL turns off if no DTCs are set. When the MIL remains on while the engine is running, or when a malfunction is suspected due to a driveability or emissions problem, perform an On-Board Diagnostic (OBD) System Check. The procedures for these checks are given in engine controls. These checks expose faults which the technician may not detect if other diagnostics are performed first. DIAGNOSTIC INFORMATION The diagnostic Tables and functional checks are designed to locate a faulty circuit or component through a process of logical decisions. The Tables are prepared with the assumption that the vehicle functioned correctly at the time of assembly and that there are not multiple faults present. There is a continuous self-diagnosis on certain control functions. This diagnostic capability is complemented by the diagnostic procedures contained in this manual. The language of communicating the source of the malfunction is a system of diagnostic trouble codes. When a malfunction is detected by the control module, a diagnostic trouble code will set and the Malfunction Indicator Lamp (MIL) Malfunction Indicator Lamp will illuminate on some applications. VCM LEARNING ABILITY WARNING: Since the VCM is located under the hood, its connectors are sealed and cannot be backprobed as in the previous model years. Do not attempt to backprobe as a connector or seal damage could occur. The VCM's learning ability allows it to make corrections for minor variations in the fuel system in order to improve driveability. When the battery is disconnected for other repairs, the learning process resets. The driver my note a change in the vehicle's performance. In order to teach the vehicle ensure that the engine is at the operating temperature. Drive the vehicle at part throttle with a moderate acceleration and idle conditions until normal performance returns. INPUT INFORMATION The VCM processes the various input information. Then the VCM sends the necessary electrical responses to the control fuel delivery, the spark timing, and the other emission control systems. The input information interrelates to more than one output; therefore, if the one input fails, the failure can affect more than one system's operation. PROM (KS Module) This assembly contains an electronic Knock Sensor (KS) module. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Diagrams > Page 5046 MEMORY There are two types of memory storage within the VCM, EEPROM and RAM. EEPROM Electrically Erasable Programmable Read Only Memory (EEPROM) is a permanent memory that is physically soldered to the circuit boards within the VCM. The EEPROM contains the overall control algorithms. The EEPROM can be reprogrammed by using the scan tool. RAM Random Access Memory (RAM) is the microprocessor scratch pad. The processor can write into or read from this memory as needed. This memory is volatile and needs a constant supply of voltage to be retained. If the voltage is lost, the memory is lost. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Testing and Inspection > Component Tests and General Diagnostics Engine Control Module: Component Tests and General Diagnostics The approved procedure for diagnosing all powertrain control system faults is included in the Strategy Based Diagnostics. The preliminary checks and the Powertrain On-board Diagnostic System Check must be performed to successfully diagnose and repair the powertrain systems. To read and clear diagnostic trouble codes, use a scan tool. See: Testing and Inspection Use a scan tool to clear diagnostic trouble codes from the VCM memory. Diagnostic trouble codes can also be cleared by turning OFF the ignition and disconnecting the battery power from the VCM for 30 seconds, but this method will also cause all diagnostic information in the VCM memory to be cleared and all the diagnostic tests will have to be re-run. Since the VCM can have a failure which may affect only one circuit, following the approved diagnostic procedures will determine which circuit has a problem and where it is. If a diagnostic table indicates that the VCM connections or VCM is the cause of a problem and the VCM is replaced. but does not correct the problem, one of the following conditions may exist: ^ There is a problem with the VCM terminal connections. The diagnostic table will indicate that the VCM connections or VCM is the problem. The terminals may have to be removed from the VCM connector in order to check them properly. ^ The EEPROM program is not correct for the application. Incorrect components may cause a malfunction and may or may not set a DTC. ^ The problem is intermittent. This means that the problem is not present at the time the system is being checked. In this case, refer to Symptoms and make a careful visual and physical inspection of all suspected components and wiring associated with the affected system. See: Testing and Inspection ^ There is a shorted solenoid, relay coil, or harness. Solenoids and relays are turned ON and OFF by the VCM using internal electronic switches called drivers. Each driver is part of a group of seven called output driver modules. A shorted solenoid, relay coil, or harness will not damage the VCM but will cause the solenoid or relay to be inoperative. The J 34636 tester, or equivalent, provides a fast, accurate means of checking for a shorted coil or a short to battery voltage. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Service and Repair > Control Module Replacement Engine Control Module: Service and Repair Control Module Replacement VCM Harness Connections VCM Access Cover Removing Knock Sensor Module From PCM Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Service and Repair > Control Module Replacement > Page 5051 VCM REPLACEMENT/PROGRAMMING Service of the VCM consists of either replacement of VCM or reprogramming of the EEPROM. If the diagnostics call for replacement of the VCM, it will be necessary to transfer the PROM and program the EEPROM. NOTE: When replacing the production VCM with a service VCM (controller), it is important to transfer the broadcast code and production VCM number to the service VCM label. This will allow positive identification of VCM parts throughout the service life of the vehicle. Also transfer the PROM. CAUTION: To prevent internal VCM damage, the ignition must be OFF when disconnecting or reconnecting power to the VCM (for example, battery cable, VCM fuse, jumper cables, etc.). CAUTION: In order to prevent possible Electrostatic Discharge damage to the VCM, do not touch the connector pins or soldered components on the circuit board. VCM REPLACEMENT/PROGRAMMING (WITH KNOCK SENSOR (KS) CALIBRATION PROM) REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Remove the connectors from the VCM. 3. Remove the spring retainer off and over the rail of the VCM. Slide the VCM out of the bracket at an angle. 4. Remove the VCM access cover. 5. Remove the PROM/Knock Sensor (KS) module. 6. Inspect for the alignment notches of the KS Calibration PROM. 7. Carefully set it aside. 8. Do not open the KS Calibration PROM. 9. Remove the new VCM from the packaging. Check the service number in order to make sure it is the same as the defective VCM. 10. Remove the access cover. NOTE ^ The Knock Sensor (KS) module must be transferred to the replacement VCM. ^ The replacement VCM is supplied without a EEPROM program, the replacement VCM must be programmed before the vehicle will run. ^ Using the thumb and first finger, remove the KS Calibration PROM by gently squeezing each end of the blue KS Calibration PROM ^ Do not remove the cover of the KS Calibration PROM. Use of an unapproved KS Calibration PROM removal methods may cause damage to the KS Calibration PROM or the socket. INSTALLATION PROCEDURE NOTE: Press only on the ends of the KS Calibration PROM. Gently press on the KS Calibration PROM until it is firmly seated in the socket. Listen for the click. 1. Align the notches of the KS Calibration PROM with the notches in the KS Calibration PROM socket. 2. Install the KS Calibration PROM in the KS Calibration PROM socket. 3. Install the access cover on the VCM. 4. Install the VCM in the engine compartment. 5. Install the connectors to the VCM. 6. The MIL, antilock and brake lamps will continue to be enabled until the VCM is programmed. Once the programming is complete, the lamps will turn off and normal operation will occur. 7. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Service and Repair > Control Module Replacement > Page 5052 CAUTION: In order to prevent possible Electrostatic Discharge damage to the VCM, do not touch the connector pins or soldered components on the circuit board. 8. Proceed to the EEPROM programming. See: EEPROM Programming Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Engine Control Module > Component Information > Service and Repair > Control Module Replacement > Page 5053 Engine Control Module: Service and Repair EEPROM Programming CAUTION: The ignition should always be "off" when installing or removing the Vehicle Control Module (VCM) connectors. 1. Set-up: ^ Battery is charged. ^ Ignition is "ON." ^ Battery/cig. lighter Connection secure. ^ Data Link Connector (DLC). 2. Refer to up-to-date Techline terminal/equipment user's instructions. 3. If Vehicle Control Module (VCM) fails to program, do the following: ^ Check all VCM connections. ^ check Techline terminal/equipment for latest software version. ^ Try again to program the VCM. If it fails again, replace the VCM. Refer to VCM replacement. See: Control Module Replacement 4. Perform the Idle Air Control (IAC) valve reset procedure with the scan tool. use misc. test. 5. For a functional check perform one of the steps: ^ Use the Techline terminal and equipment in order to perform the On-Board Diagnostic (OBD) System Check ^ Refer to Powertrain OBD System Check. See: Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Relays and Modules Computers and Control Systems > Knock Sensor Module > Component Information > Diagrams Knock Sensor Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions Mass Air Flow (MAF) Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5062 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5063 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5064 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5065 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5066 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5067 Mass Air Flow (MAF) Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5068 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5069 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5070 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5071 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5072 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5073 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5074 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5075 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5076 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5077 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5078 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5079 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5080 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5081 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5082 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5083 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5084 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5085 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5086 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5087 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5088 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5089 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5090 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5091 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5092 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5093 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5094 Mass Air Flow System Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Page 5095 Mass Air Flow (MAF) Sensor: Description and Operation Mass Air Flow (MAF) Sensor The Mass Air Flow (MAF) sensor measures the amount of air which passes through it. The VCM uses this information to determine the operating condition of the engine, to control fuel delivery. A large quantity of air indicates acceleration. A small quantity of air indicates deceleration or idle. The scan tool reads the MAF value and displays it in grams per second (gm/Sec). At idle, it should read between 5-7 gm/Sec on a fully warmed up engine. Values should change rather quickly on acceleration, but values should remain fairly stable at any given RPM. When the VCM detects a malfunction in the MAF sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0101 system performance. ^ DTC P0102 frequency low. ^ DTC P0103 frequency high. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Page 5096 Mass Air Flow (MAF) Sensor: Service and Repair MAF Sensor MAF Sensor Intake Duct REMOVAL PROCEDURE CAUTION: Take care when handling the Mass Air Flow (MAF). Do Not dent, puncture, or otherwise damage the honeywell located at the air inlet end of the MAF. Do Not touch the sensing elements or allow anything (including solvents and lubricants) to come in contact with them. A small amount of GM lubricant (P/N 99855406) may be used on the air duct only to aid in installation. Do Not drop or roughly handle the MAF. 1. Disconnect the 3 wire electrical connector. 2. Loosen the clamp on the intake duct. 3. Carefully remove the MAF sensor. INSTALLATION PROCEDURE 1. Install the MAF sensor. 2. Install the intake ducts. 3. Tighten the clamp. 4. Connect the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Camshaft Position Sensor: Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5101 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5102 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5103 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5104 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5105 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5106 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5107 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Page 5108 Camshaft Position Sensor: Specifications Camshaft position sensor retaining screw ........................................................................................................................................... 4-6 Nm (35-53 lb. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Page 5109 Engine View, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Camshaft Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5112 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5113 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5114 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5115 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5116 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5117 Camshaft Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5118 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5119 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5120 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5121 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5122 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5123 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5124 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5125 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5126 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5127 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5128 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5129 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5130 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5131 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5132 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5133 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5134 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5135 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5136 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5137 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5138 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5139 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5140 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5141 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5142 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5143 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Diagrams > Page 5144 Camshaft Position Sensor: Description and Operation Camshaft Position Sensor The Camshaft Position (CMP) sensor is located within the distributor. It's operation is very similar to the Crankshaft Position (CKP) sensor however it will provide one pulse per camshaft revolution (1x signal). This signal is not detrimental to the driveability of the vehicle. The Vehicle Control Module (VCM) utilizes this signal in conjunction with the crankshaft position to determine which cylinder(s) are misfiring. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Testing and Inspection > Cam Signal Camshaft Position Sensor: Testing and Inspection Cam Signal The VCM uses this signal to determine the position of the #1 piston during its power stroke. This signal is used by the VCM to calculate fuel injection mode of operation. A loss of this signal will set DTC P0340. If the cam signal is lost while the engine is running, the fuel injection system will shift to a calculated fuel injection mode based on the last fuel injection pulse, and the engine will continue to run. The engine can be restarted and will run in the calculated mode as long as the fault is present Refer to Diagnostic Trouble Code (DTC) P0340 Camshaft Position Sensor (CKP) Sensor Circuit. See: Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Camshaft Position Sensor > Component Information > Testing and Inspection > Page 5147 Camshaft Position Sensor: Service and Repair REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Disconnect the electrical connector from the camshaft position sensor. 3. Remove the camshaft position sensor retaining screw. 4. Remove the camshaft position sensor. INSTALLATION PROCEDURE 1. Install the camshaft position sensor. 2. Install the camshaft position sensor retaining screw, torque to 4-6 Nm (35-53 lb. in.). 3. Connect the electrical connector. 4. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Specifications Coolant Temperature Sensor/Switch (For Computer): Specifications Engine Coolant Temperature (ECT) sensor .............................................................................................................................................. 13 Nm (10 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Specifications > Page 5151 Engine Side, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions Coolant Temperature Sensor/Switch (For Computer): Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5154 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5155 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5156 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5157 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5158 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5159 Coolant Temperature Sensor/Switch (For Computer): Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5160 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5161 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5162 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5163 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5164 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5165 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5166 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5167 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5168 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5169 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5170 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5171 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5172 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5173 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5174 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5175 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5176 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5177 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5178 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5179 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5180 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5181 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5182 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5183 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5184 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5185 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Diagram Information and Instructions > Page 5186 ECT Sensor Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 5187 Coolant Temperature Sensor/Switch (For Computer): Description and Operation Engine Coolant Temperature (ECT) Sensor DESCRIPTION The engine coolant temperature sensor is a thermistor (a resistor which changes value based on temperature) mounted in the engine coolant passage. Low coolant temperature produces a high resistance 100,000 ohms at -40°C (-40°F) while high temperature causes low resistance 70 ohms at 130°C (266°F). OPERATION The VCM supplies a 5 volt signal to the engine coolant temperature sensor through a resistor in the VCM and measures the voltage. The voltage will be high when the engine is cold. The voltage will be low when the engine is hot. By measuring the voltage, the VCM calculates the engine coolant temperature. Engine coolant temperature affects most systems the VCM controls. The scan tool displays engine coolant temperature in degrees. After engine start-up, the temperature should rise steadily to about 9O°C (194°F) then stabilize when thermostat opens. If the engine has not been run for several hours (overnight), the engine coolant temperature and intake air temperature displays should be close to each other. When the VCM detects a malfunction in the Engine Coolant Temperature (ECT) sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0117 circuit low. ^ DTC P0118 circuit high. ^ DTC P0125 excessive time to Closed Loop. ^ DTC P1114 circuit intermittent low. ^ DTC P1115 circuit intermittent high. The above DTCs contain a table to check for sensor resistance values relative to temperature. Refer to Specifications. See: Specifications Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 5188 Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection The scan tool displays engine coolant temperature in degrees. After engine start-up, the temperature should rise steadily to about 90°C (194°F) then stabilize when thermostat opens. If the engine has not been run for several hours (overnight), the engine coolant temperature and intake air temperature displays should be close to each other. When the VCM detects a malfunction in the Engine Coolant Temperature (ECT) sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0117 circuit low. ^ DTC P0118 circuit high. ^ DTC P0125 excessive time to Closed Loop. ^ DTC P1114 circuit intermittent low. ^ DTC P1115 circuit intermittent high. The above DTCs contain a table to check for sensor resistance values relative to temperature. Refer to Diagnostic Tables. See: Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagrams > Page 5189 Coolant Temperature Sensor/Switch (For Computer): Service and Repair Engine Coolant Temperature (ECT) Sensor Electrical Connector Engine Coolant Temperature (ECT) Sensor CAUTION: Use care when handling the coolant sensor. Damage to the coolant sensor will affect the operation of the fuel control system. REMOVAL PROCEDURE 1. Relieve the coolant pressure. 2. Disconnect the negative battery cable. 3. Drain the cooling system below the level of the sensor. 4. Disconnect the electrical connector releasing locking tab. 5. Remove the coolant sensor from engine. INSTALLATION PROCEDURE 1. Coat the threads (only) with sealer P/N 9985253 or equivalent. Tighten ^ Tighten the sensor to 13 N.m (10 lb. ft.). 2. Install the coolant sensor in the engine. 3. Connect the electrical connector. 4. Refill the cooling system. 5. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-014 > Apr > 00 > Engine - No/Hard/Slow Start/Backfire/Kickback Crankshaft Position Sensor: Customer Interest Engine - No/Hard/Slow Start/Backfire/Kickback File In Section: 06 - Engine/Propulsion System Bulletin No.: 00-06-04-014 Date: April, 2000 TECHNICAL Subject: No, Hard, or Slow Start, Backfire or "Kickback" During Crank/Start, "Grinding" or Unusual Noises During Crank, DTC P0338 (Replace Crankshaft Position Sensor) Models: 1999-2000 Cadillac Escalade 1995-2000 Chevrolet and GMC SIT Models 1996-2000 Chevrolet and GMC C/K, M/L, G, P Models 1996-2000 Oldsmobile Bravada with 4.3 L, 5.0 L, 5.7 L or 7.4 L Engine (VINs W, X, M, R, J RPOs L35, LF6, L30, L31, L29) Condition: Some customers may comment on one or more of the following conditions: ^ Backfire during crank/start ^ "Kickback" during crank/start ^ "No" start ^ "Slow" or "hard" start/crank ^ "Grinding" or unusual noises during crank/start ^ Cracked or broken engine block at the starter boss ^ Broken starter drive housing ^ Broken starter ring gear on flywheel ^ Any combination of the above Cause: A condition may exist that allows the crankshaft position sensor to command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss. Correction: Inspect for a stored powertrain DTC code P0338. This DTC will NOT illuminate the "Service Engine Soon" light. If this code is stored, the Crankshaft Position Sensor, P/N 10456607, MUST be replaced and the remaining components inspected for damage (engine block at the starter boss, the starter drive housing, and the engine flywheel starter ring gear). Notice: When DTC code P0338 is set, failure to replace the Crankshaft Position Sensor could result in repeated inoperative conditions of the starter or flywheel. Important: Some flywheel wear is normal; broken or missing teeth and/or cracks, are not normal. Parts Information Parts are currently available from GMSPO. Warranty Information: For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 00-06-04-014 > Apr > 00 > Engine - No/Hard/Slow Start/Backfire/Kickback Crankshaft Position Sensor: All Technical Service Bulletins Engine - No/Hard/Slow Start/Backfire/Kickback File In Section: 06 - Engine/Propulsion System Bulletin No.: 00-06-04-014 Date: April, 2000 TECHNICAL Subject: No, Hard, or Slow Start, Backfire or "Kickback" During Crank/Start, "Grinding" or Unusual Noises During Crank, DTC P0338 (Replace Crankshaft Position Sensor) Models: 1999-2000 Cadillac Escalade 1995-2000 Chevrolet and GMC SIT Models 1996-2000 Chevrolet and GMC C/K, M/L, G, P Models 1996-2000 Oldsmobile Bravada with 4.3 L, 5.0 L, 5.7 L or 7.4 L Engine (VINs W, X, M, R, J RPOs L35, LF6, L30, L31, L29) Condition: Some customers may comment on one or more of the following conditions: ^ Backfire during crank/start ^ "Kickback" during crank/start ^ "No" start ^ "Slow" or "hard" start/crank ^ "Grinding" or unusual noises during crank/start ^ Cracked or broken engine block at the starter boss ^ Broken starter drive housing ^ Broken starter ring gear on flywheel ^ Any combination of the above Cause: A condition may exist that allows the crankshaft position sensor to command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss. Correction: Inspect for a stored powertrain DTC code P0338. This DTC will NOT illuminate the "Service Engine Soon" light. If this code is stored, the Crankshaft Position Sensor, P/N 10456607, MUST be replaced and the remaining components inspected for damage (engine block at the starter boss, the starter drive housing, and the engine flywheel starter ring gear). Notice: When DTC code P0338 is set, failure to replace the Crankshaft Position Sensor could result in repeated inoperative conditions of the starter or flywheel. Important: Some flywheel wear is normal; broken or missing teeth and/or cracks, are not normal. Parts Information Parts are currently available from GMSPO. Warranty Information: For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Crankshaft Position Sensor: All Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5207 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5208 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5209 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5210 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5211 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5212 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5213 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Crankshaft Position Sensor: All Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5219 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5220 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5221 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5222 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5223 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5224 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 5225 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Page 5226 Crankshaft Position Sensor: Specifications Crankshaft Position Sensor mounting bolts ................................................................................................................................................. 8 Nm (71 lb. In.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Page 5227 Engine Side, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Crankshaft Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5230 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5231 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5232 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5233 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5234 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5235 Crankshaft Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5236 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5237 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5238 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5239 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5240 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5241 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5242 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5243 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5244 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5245 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5246 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5247 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5248 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5249 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5250 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5251 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5252 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5253 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5254 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5255 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5256 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5257 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5258 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5259 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5260 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5261 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Page 5262 Crankshaft Position Sensor: Description and Operation DESCRIPTION The Crankshaft Position (CKP) Sensor is located in the front engine cover and is perpendicular to the crankshaft target wheel. The air gap between the sensor and the wheel is preset and not adjustable. The target wheel has three slots 60° apart and is keyed to the crankshaft. As the target wheel rotates, the slots passing by the sensor create a change in the magnetic field of the sensor which results in an induced voltage pulse. One revolution of the crankshaft results in three pulses (3x signal). Based on these pulses, the VCM is able to determine crankshaft position and engine speed. The VCM then activates the fuel injector and provides a spark to the Distributor. The relation between the crankshaft position sensor and the target wheel is crucial. The sensor must be exactly perpendicular to the target wheel with the correct air gap. OPERATION The crankshaft position sensor provides the VCM with crankshaft speed and crankshaft position. The VCM utilizes this information to determine if an engine Misfire is present. The VCM monitors the Crankshaft Position Sensor (CKP) sensor for momentarily drop in crankshaft speed to determine if a misfire is occurring. When the VCM detects a misfire, a Diagnostic Trouble Code (DTC) P0300 will set. The VCM also monitors the CKP sensor signal circuit for malfunctions. The VCM monitors CKP signal and the High and Low resolution signals. The VCM calculates these signals to determine a ratio. When the VCM detects that the ratio is out of normal operating range, the VCM will set a Diagnostic Trouble Code (DTC) P0337 or a DTC P0338. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Page 5263 Crankshaft Position Sensor: Service and Repair REMOVAL PROCEDURE 1. Remove the electrical connector. 2. Remove the sensor hold down bolt. 3. Remove the sensor from the timing cover. NOTE: When installing or removing a crankshaft position (CKP) sensor make sure the sensor is fully seated and held stationary in the front cover before torquing the hold down bolt into the front cover. A sensor which is not seated may result in erratic operation and lead to the setting of false codes. 4. Inspect the sensor O-ring for wear, cracks or leakage. Replace if necessary. Lube the new O-ring with clean engine oil before installing. INSTALLATION PROCEDURE NOTE: Make certain that the Crankshaft Position (CKP) sensor mounting surfaces are clean and free of burrs before installing the CKP sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Crankshaft Position Sensor > Component Information > Diagrams > Page 5264 1. Install the sensor into the timing cover. 2. Install the sensor hold down bolt. Tighten ^ Tighten the hold down bolt to 8 Nm (71 lb. in.). 3. Install the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Specifications Intake Air Temperature (IAT) Sensor: Specifications Torque Valve Torque Valve Induction Air Sensor 44 in.lb Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions Intake Air Temperature (IAT) Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5270 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5271 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5272 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5273 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5274 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5275 Intake Air Temperature (IAT) Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5276 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5277 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5278 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5279 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5280 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5281 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5282 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5283 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5284 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5285 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5286 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5287 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5288 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5289 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5290 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5291 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5292 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5293 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5294 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5295 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5296 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5297 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5298 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5299 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5300 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5301 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5302 IAT Sensor Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Page 5303 Intake Air Temperature (IAT) Sensor: Description and Operation Intake Air Temperature (IAT) Sensor PURPOSE The Intake Air Temperature (IAT) sensor is a thermistor which changes value based on the temperature of air entering the engine. OPERATION Low temperature produces a high resistance 100,000 ohms at -40° (-40°F). A high temperature causes low resistance 70 ohms at 130°C (266°F). The VCM supplies a 5.0 volt signal to the sensor through a resistor in the VCM and measures the voltage. The voltage will be high when the incoming air is cold, and low when the air is hot. By measuring the voltage, the VCM calculates the incoming air temperature. The IAT sensor signal is used to adjust spark timing according to incoming air density. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Page 5304 Intake Air Temperature (IAT) Sensor: Testing and Inspection The scan tool displays temperature of the air entering the engine, which should read close to ambient air temperature when engine is cold, and rise as underhood temperature increases. If the engine has not been run for several hours (overnight) the Intake Air Temperature (IAT) sensor temperature and engine coolant temperature should read close to each other. If the VCM detects a malfunction in the AT sensor circuit, the following DTCs will set: ^ DTC P0112 circuit low. ^ DTC P0113 circuit high. ^ DTC P0111 circuit intermittent high. ^ DTC P0112 circuit intermittent low. Refer to Diagnostic Tables. See: Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Intake Air Temperature (IAT) Sensor <--> [Intake Air Temperature Sensor] > Component Information > Diagrams > Page 5305 Intake Air Temperature (IAT) Sensor: Service and Repair IAT Sensor And Electrical Connector REMOVAL PROCEDURE 1. Disconnect the electrical connector releasing locking tab. 2. Remove the Intake Air Temperature (IAT) sensor by grasping sensor, twist and pull out from air cleaner INSTALLATION PROCEDURE 1. Install the IAT sensor. 2. Connect the electrical connector Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Specifications Knock Sensor: Specifications Knock sensor ....................................................................................................................................... ....................................................... 19 Nm (14 lb. ft.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Specifications > Page 5309 Knock Sensor: Locations Engine View, Rear LH side of Engine Block, below Exhaust Manifold, forward of Starter Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions Knock Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5312 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5313 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5314 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5315 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5316 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5317 Knock Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5318 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5319 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5320 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5321 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5322 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5323 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5324 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5325 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5326 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5327 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5328 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5329 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5330 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5331 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5332 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5333 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5334 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5335 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5336 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5337 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5338 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5339 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5340 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5341 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5342 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5343 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5344 Knock Sensor Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Page 5345 Knock Sensor: Description and Operation Description The Knock Sensor (KS) system is used to detect engine detonation The VCM will retard the spark timing based on the signals from the KS module. The Knock Sensor(s) produce an AC voltage that is sent to the KS module. The amount of AC voltage produced is proportional to the amount of knock. Operation An operating engine produces a normal amount of engine mechanical vibration (Noise). The knock sensor(s) will produce an AC voltage signal from this Noise. When an engine is operating, the VCM will learn the minimum and maximum frequency of the noise the engine produces. When the VCM determines that this frequency is less than or greater than the expected amount, a knock sensor DTC will set. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Knock Sensor > Component Information > Diagrams > Page 5346 Knock Sensor: Service and Repair Diagram Removal Procedure NOTE: The knock sensor is located in areas of the cylinder head. On most applications, the knock sensors are installed in a hole which is exposed to engine coolant. Care should be exercised when servicing these sensors. 1. Disconnect the negative battery cable. Important: On knock sensors which are mounted in the end of the cylinder head draining the cooling system will not be necessary. 2. Drain the cooling system. Refer to Draining and Filling Cooling System. 3. Remove the wiring harness connector from knock sensor. 4. Remove the knock sensor from cylinder head. Installation Procedure Important: Do not use silicon tape as this will insulate the sensor from the engine block. 2. After applying a water base caulk to the sensor threads, install the knock sensor into the cylinder head. Tighten ^ Tighten to 19 Nm (14 lb. ft.). 2. Connect the negative battery cable. 3. Refill cooling system if required. Refer to Draining and Filling Cooling System. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Locations Engine Side, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions Manifold Absolute Pressure (MAP) Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5352 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5353 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5354 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5355 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5356 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5357 Manifold Absolute Pressure (MAP) Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5358 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5359 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5360 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5361 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5362 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5363 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5364 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5365 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5366 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5367 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5368 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5369 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5370 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5371 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5372 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5373 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5374 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5375 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5376 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5377 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5378 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5379 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5380 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5381 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5382 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5383 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5384 MAP System Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Page 5385 Manifold Absolute Pressure (MAP) Sensor: Description and Operation Manifold Absolute Pressure (MAP) Sensor PURPOSE The Manifold Absolute Pressure (MAP) sensor responds to changes in the intake manifold pressure. The pressure changes as a result of engine load and speed. The map sensor converts this to a voltage output. OPERATION A closed throttle on engine coast down would produce a relatively low MAP output voltage. A wide open throttle would produce a high MAP output voltage. This high output voltage is produced because the pressure inside the manifold is the same as outside the manifold. The MAP is inversely proportional to what is measured on a vacuum gage. The MAP sensor is used for the following: ^ Altitude determination. ^ Ignition timing control. ^ Exhaust Gas Recirculation (EGR) diagnostic. ^ Speed density fuel management default. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Page 5386 Manifold Absolute Pressure (MAP) Sensor: Testing and Inspection When the VCM detects a malfunction in the MAP sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0106 circuit performance. ^ DTC P0107 circuit low. ^ DTC P0108 circuit high. ^ DTC P1106 intermittent circuit high. ^ DTC P1107 intermittent circuit low. Refer to System Diagnosis / Diagnostic Charts for testing information. See: Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Manifold Absolute Pressure (MAP) Sensor <--> [Manifold Pressure/Vacuum Sensor] > Component Information > Diagrams > Page 5387 Manifold Absolute Pressure (MAP) Sensor: Service and Repair MAP Sensor NOTE: Other than checking for loose hoses and electrical connections, the only service possible is unit replacement, if the diagnosis shows the sensor to be faulty. REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Disconnect the vacuum harness assembly. 3. Disconnect the electrical connector releasing locking tab. 4. Remove the bolts or release lock tabs and remove the sensor. INSTALLATION PROCEDURE 1. Install the bolts or snap sensor on bracket. 2. Connect the electrical connector. 3. Connect the vacuum harness. 4. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Oxygen Sensor - Locations in Various Exhaust Systems Oxygen Sensor: Technical Service Bulletins Oxygen Sensor - Locations in Various Exhaust Systems File In Section: 6E - Engine Fuel & Emission Bulletin No.: 67-65-40 Date: March, 1997 INFORMATION Subject: Pictorial of Oxygen Sensor Designations in Various Exhaust Systems Configurations Models: 1996-97 Passenger Cars, Geos and Trucks Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Oxygen Sensor - Locations in Various Exhaust Systems > Page 5392 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Oxygen Sensor - Locations in Various Exhaust Systems > Page 5393 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Oxygen Sensor - Locations in Various Exhaust Systems > Page 5394 Pictorials of the designation of oxygen sensors in General Motors vehicles. There has been some confusion relative to OBD II oxygen sensor designation. The intent of this bulletin is to eliminate misdiagnosis of those oxygen sensors due to misidentification. When using Section 6E of the Service Manual, this chart can help locate the appropriate bank and sensor for the diagnostic. For "V" engines; BANK 1 is always on the side of the engine with the number 1 cylinder (odd cylinders), and BANK 2 is always on the side of the engine where the number 2 cylinder (even cylinders) is located. Just a reminder, the OBD II P-codes, technician observations and customer comments are all to be recorded on the repair order in accordance with article 1.6.2G of the GM Service Policies and Procedures Manual. Use the approved labor operation for the sensors replaced. J 6372 is used for engine out sensors. Labor Operation J 6380 is for the pre-sensor (the sensor just in front of the catalytic converter) and the post sensor (the sensor behind the catalytic converter). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Technical Service Bulletins > Page 5395 Oxygen Sensor: Specifications Heated Oxygen Sensor (HO2S) .......................................................................................................... ...................................................... 41 Nm (30 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations Oxygen Sensor: Component Locations Light Duty Vehicles Bulletin No.: 67-65-40 PICTORIALS OF THE DESIGNATION OF OXYGEN SENSORS There has been some confusion relative to OBD II oxygen sensor designation. The intent of this article is to eliminate misdiagnosis of those oxygen sensors due to mis-identification. This chart can help locate the appropriate bank and sensor for the diagnostic. NOTE: For "V" engines; BANK 1 is always on the side of the engine with the number 1 cylinder (odd cylinders), and BANK 2 is always on the side of the engine where the number 2 cylinder (even cylinders) is located. Heavy Duty Vehicles Bulletin No.: 67-65-40 PICTORIALS OF THE DESIGNATION OF OXYGEN SENSORS Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 5398 There has been some confusion relative to OBD II oxygen sensor designation. The intent of this article is to eliminate misdiagnosis of those oxygen sensors due to mis-identification. This chart can help locate the appropriate bank and sensor for the diagnostic. NOTE: For "V" engines; BANK 1 is always on the side of the engine with the number 1 cylinder (odd cylinders), and BANK 2 is always on the side of the engine where the number 2 cylinder (even cylinders) is located. 5-Speed Manual Transmission (MW3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 5399 Oxygen Sensor: Connector Locations Engine View, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 5400 Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 5401 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 5402 5-Speed Manual Transmission W/4WD 5-Speed Manual Transmission (MW3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 5403 5-Speed Manual Transmission (MW3) 5-Speed Manual Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Locations > Component Locations > Page 5404 Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions Oxygen Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5407 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5408 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5409 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5410 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5411 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5412 Oxygen Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5413 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5414 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5415 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5416 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5417 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5418 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5419 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5420 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5421 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5422 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5423 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5424 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5425 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5426 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5427 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5428 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5429 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5430 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5431 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5432 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5433 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5434 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5435 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5436 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5437 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5438 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5439 Oxygen Sensor: Connector Views C107: Engine HARN To Oxygen Sensor HARN Oxygen Sensor RH, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5440 HO2S Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Page 5441 Oxygen Sensor: Description and Operation Heated Oxygen Sensor (HO2S) Cutaway OPERATION To control emissions of Hydrocarbons (HO), Carbon Monoxide (CO), and Oxides of Nitrogen (NOx), a three-way catalytic converter is used. The catalyst within the converter promotes a chemical reaction which oxidizes the HO and CO present in the exhaust gas, converting them into harmless water vapor and carbon dioxide. The catalyst also reduces NOx, converting it to nitrogen. The VCM has the ability to monitor this process using the Bank 1 Sensor 2 and the Bank 2 Sensor 2 heated oxygen sensors. The Bank 1 Sensor 2 sensor produces an output signal which indicates the amount of oxygen present in the exhaust gas entering the three way catalytic converter. The Bank 2 Sensor 2 sensor produces an output signal which indicates the oxygen storage capacity of the catalyst; this in turn indicates the catalyst ability to convert exhaust gases efficiently. If the catalyst is operating efficiently, the Bank 1 Sensor 2 sensor will produce a far more active signal than that produced by the Bank 2 Sensor 2 sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Diagrams > Page 5442 The catalyst monitor sensors operate the same as the fuel control sensors. Although the Bank 1 Sensor 2 and Bank 2 Sensor 2 sensors main function is catalyst monitoring, they also play a limited role in fuel control. If a sensor output indicates a voltage either above or below the 450 millivolt bias voltage for an extended period of time, the VCM will make a slight adjustment to fuel trim to ensure that fuel delivery is correct for catalyst monitoring. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Testing and Inspection > Heated Oxygen Sensor (HO2S 1) Testing Oxygen Sensor: Testing and Inspection Heated Oxygen Sensor (HO2S 1) Testing The heated oxygen sensor circuit, if open, should set a Diagnostic Trouble Code (DTC) P0134 and the Scan tool will display a constant voltage between 350-550 mV. A constant voltage below 250 mV in the sensor circuit should set DTC P0131, while a constant voltage above 750 mV in the circuit should set DTC P0132. DTC P0131 and DTC P0132 could also be set as a result of fuel system problems. Refer to DTC P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1 or DTC P0132 HO2S Circuit High Voltage Bank 1 Sensor 1 or DTC P0134 HO2S Insufficient Activity Bank 1 Sensor 1. Refer to System Diagnosis / Diagnostic Charts for testing information. See: Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Testing and Inspection > Heated Oxygen Sensor (HO2S 1) Testing > Page 5445 Oxygen Sensor: Testing and Inspection Heated Oxygen Sensor (HO2S 2) Testing A problem with the HO2S 2 electrical circuits should set Diagnostic Trouble Code (DTC) P0137, P0138 or P0140, depending on the specific condition. If the catalyst is functioning correctly, the HO2S 2 signal will be far less active than that produced by HO2S 1. If a problem exists which causes the VCM to detect excessive HO2S 2 activity outside of an acceptable range for an extended period of time, the VCM will set DTC P0420, indicating that the three-way catalytic converter [prime ]s oxygen storage capacity is below a threshold considered acceptable. Refer to DTC P0137 HO2S Circuit Low Voltage Bank 1 Sensor 2 or DTC P0138 HO2S Circuit High Voltage Bank 1 Sensor 2 or DTC P0140 HO2S Insufficient Activity Bank 1 Sensor 2 or DTC P0420 TWC System Low Efficiency Bank 1. Refer to System Diagnosis / Diagnostic Charts for testing information. See: Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Testing and Inspection > Page 5446 Oxygen Sensor: Service and Repair Heated Oxygen Sensor (HO2S) Electrical Connector Heated Oxygen Sensor (HO2S) REMOVAL PROCEDURE CAUTION: The Heated Oxygen Sensor (HO2S) and the Oxygen Sensor use a permanently attached pigtail and connector. Do not remove this pigtail from the Heated Oxygen Sensor. Damage or the removal of the pigtail or the connector could affect the proper operation of the sensor. CAUTION: Take care when handling the HO2S. Keep the in-line electrical connector and the louvered end free of grease, dirt, or other contaminants. Also avoid using cleaning solvents of any type. Do not drop or roughly handle the HO2S. CAUTION: If the heated oxygen sensor pigtail wiring, connector or terminal is damaged, the entire oxygen sensor assembly must be replaced. Do Not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. CAUTION: This clean air reference is obtained by way of the oxygen sensor signal and heater wires. Any attempt to repair the wires, connectors, or terminals could result in the obstruction of the air reference and degraded sensor performance. The following guidelines should be used when servicing the heated oxygen sensor: ^ Do Not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. ^ The sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems, ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do Not remove or defeat the oxygen sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will cause poor engine performance. ^ To prevent damage due to water intrusion. be sure that the peripheral seal remains intact on the vehicle harness connector. The engine harness Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Oxygen Sensor > Component Information > Testing and Inspection > Page 5447 may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. CAUTION: The Heated Oxygen Sensor (HO2S) may be difficult to remove when the engine temperature is below 48°C (120°F). Excessive force may damage the threads in the exhaust manifold or the exhaust pipe. 1. Disconnect the negative battery cable. 2. Remove the electrical connector by releasing the locking tab. 3. Carefully back out the heated oxygen sensor. INSTALLATION PROCEDURE NOTE: A special anti-seize compound is used on the Heated Oxygen Sensor (HO2S) threads. The compound consists of liquid graphite and glass beads. The graphite tends to burn away, but the glass beads remain, making the sensor easier to remove. New, or service replacement sensors already have the compound applied to the threads. If the sensor is removed from an engine and if for any reason it is to be reinstalled, the threads must have anti-seize compound applied before the reinstallation. 1. Coat the threads of the oxygen sensor with anti-seize compound GM P/N 5613695 or the equivalent if necessary. 2. Install the sensor. Tighten ^ Tighten the sensor to 41 Nm (30 lb. ft.). 3. Install the electrical connector. 4. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Specifications Throttle Position Sensor: Specifications Screw assemblies ................................................................................................................................ .................................................. 2.0 Nm (18.0 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Specifications > Page 5451 Engine Side, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Throttle Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5454 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5455 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5456 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5457 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5458 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5459 Throttle Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5460 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5461 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5462 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5463 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5464 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5465 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5466 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5467 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5468 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5469 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5470 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5471 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5472 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5473 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5474 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5475 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5476 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5477 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5478 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5479 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5480 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5481 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5482 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5483 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5484 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5485 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5486 TP Sensor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Page 5487 Throttle Position Sensor: Description and Operation Diagram The non-adjustable Throttle Position (TP) sensor is mounted on the throttle body assembly opposite the throttle lever. The TP sensor senses the throttle valve angle and relays that information to the VCM. Knowledge of throttle angle is one of the inputs needed by the VCM to generate the required injector control signals (pulses). For further information on replacement, refer to TP Sensor. See: Service and Repair Legend (1) Throttle Body Assembly. (2) IAC Valve Assembly 0-ring. (3) IAC Valve Assembly Attaching Screw. (4) Idle Air Control (IAC) Valve Assembly. (5) TP Sensor 0-ring (6) Throttle Position (TP) Sensor. (7) TP Sensor Attaching Screw. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Testing and Inspection > Throttle Position (TP) Sensor Throttle Position Sensor: Testing and Inspection Throttle Position (TP) Sensor When the VCM detects a malfunction with the Throttle Position (TP) sensor circuits, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0121 circuit performance ^ DTC P0122 circuit low. ^ DTC P0123 circuit high. ^ DTC P1121 intermittent circuit high. ^ DTC P1122 intermittent circuit low. Refer to Diagnostic Tables. See: Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Testing and Inspection > Throttle Position (TP) Sensor > Page 5490 Throttle Position Sensor: Testing and Inspection Throttle Position Sensor Output This check should be performed when Throttle Position (TP) sensor attaching parts have been replaced. A scan tool can be used to read the TP signal output voltage. 1. Connect digital voltmeter J 39200 from TP sensor connector terminal B (BLk wire) to terminal C (DK Blue wire). Jumpers for terminal access can be made using terminals 1214836 and 12014837. 2. With ignition ON, engine stopped, the TP signal voltage should be less than 1.25V if more than 1.25V verify free throttle movement. If still more than 1.25V, replace TP sensor. 3. Remove the voltmeter and jumpers, reconnect the TP sensor connector to the sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Testing and Inspection > Page 5491 Throttle Position Sensor: Service and Repair Throttle Position Sensor Electrical Connector REMOVAL PROCEDURE CAUTION: The Throttle Position (TP) sensor is an electrical component. Do not soak the TP sensor in any liquid cleaner or solvent, as damage may result. 1. Remove the air cleaner and adapter. 2. Disconnect the electrical connector releasing locking tab. 3. Remove the two TP sensor attaching screw assemblies. 4. Remove the TP sensor from throttle body assembly. 5. Remove the TP sensor seal. INSTALLATION PROCEDURE 1. Install the TP sensor seal over throttle shaft. 2. With throttle valve closed, install the TP sensor on the throttle shaft. Rotate counterclockwise to align mounting holes. 3. Install the two TP sensor attaching screw assemblies. Tighten ^ Tighten the screw assemblies to 2.0 Nm (18.0 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Throttle Position Sensor > Component Information > Testing and Inspection > Page 5492 4. Connect the electrical connector. 5. Install the air cleaner and adapter. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Technical Service Bulletins > A/T - Park/Neutral Switch Connector Cannot Be Removed Transmission Position Switch/Sensor: Technical Service Bulletins A/T - Park/Neutral Switch Connector Cannot Be Removed File In Section: 7 - Transmission Bulletin No.: 83-71-10 Date: May, 1998 Subject: Park (Neutral Position Switch Connector Cannot be Removed (Replace Switch and Connectors) Models: 1997-98 Chevrolet Corvette 1995-98 Chevrolet and GMC S/T Models 1996-98 Chevrolet and GMC M/L, P Models 1996-99 Chevrolet and GMC C/K, G Models 1996-98 Oldsmobile Bravada Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer conditions, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to insure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to insure water-tight connections. Parts Information P/N Description 12450016 Switch 15305925 4-Way Connector Assembly 15305887 7-Way Connector Assembly Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 5499 Transmission Position Switch/Sensor: Locations Park/Neutral Position Switch Electronic 4-Speed Automatic Overdrive Transmission Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 5500 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions Transmission Position Switch/Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5503 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5504 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5505 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5506 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5507 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5508 Transmission Position Switch/Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5509 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5510 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5511 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5512 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5513 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5514 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5515 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5516 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5517 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5518 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5519 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5520 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5521 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5522 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5523 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5524 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5525 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5526 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5527 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5528 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5529 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5530 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5531 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5532 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5533 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5534 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5535 Transmission Position Switch/Sensor: Connector Views C1: Transmission Range Switch C2: Transmission Range Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5536 Transmission Position Switch/Sensor: Electrical Diagrams Electronic PRNDL Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5537 Starter And Charging (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 5538 Transmission Position Switch/Sensor: Testing and Inspection Pressure Switch Assembly Resistance Check (1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 5539 Pressure Switch Assembly Resistance Check (2 Of 2) Tools Required - J 39775 4L60E Jumper Harness - J 39200 Digital Multimeter - J 35616 Connector Test Adapter Kit Important: Whenever the transmission 20-way connector is disconnected and the engine is running, multiple DTCs will set. Be sure to clear these codes when you are finished with this procedure Important: This procedure tests the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) circuits and the Automatic Transmission Fluid Temperature (TFT) Sensor circuit. Do not use this procedure to test other Automatic Transmission circuits, refer to 4L60-E Automatic Transmission Internal Wiring Harness check. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 5540 Transmission Position Switch/Sensor: Adjustments PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 5541 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 5542 Transmission Position Switch/Sensor: Service and Repair PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 5543 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations Vehicle Speed Sensor: Component Locations 5-Speed Manual Transmission 5-Speed Manual Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 5548 5-Speed Manual Transmission (MW3) 5-Speed Manual Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 5549 5-Speed Manual Transmission Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 5550 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 5551 Electronic 4-Speed Automatic Overdrive Transmission Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 5552 Vehicle Speed Sensor: Connector Locations 5-Speed Manual Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 5553 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions Vehicle Speed Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5556 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5557 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5558 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5559 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5560 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5561 Vehicle Speed Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5562 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5563 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5564 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5565 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5566 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5567 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5568 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5569 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5570 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5571 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5572 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5573 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5574 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5575 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5576 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5577 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5578 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5579 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5580 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5581 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5582 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5583 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5584 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5585 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5586 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5587 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Sensors and Switches Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Page 5588 Vehicle Speed Sensor: Description and Operation Vehicle Speed Sensor (2WD) DESCRIPTION The Vehicle Speed Sensor (VSS) is a pulse counter type input that informs the VCM how fast the vehicle is being driven. The VSS system uses an inductive sensor mounted in the tail housing of the transmission and a toothed reluctor wheel on the tail shaft. OPERATION As the reluctor rotates, the teeth alternately interfere with the magnetic field of the sensor creating an induced voltage pulse. The VSS produces an AC voltage signal that increases with vehicle speed. The VCM processes this signal and sends it to the following components: ^ Instrument Panel. ^ Cruise Control Module. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Specifications Throttle Position Sensor: Specifications Screw assemblies ................................................................................................................................ .................................................. 2.0 Nm (18.0 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Specifications > Page 5592 Engine Side, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Throttle Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5595 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5596 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5597 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5598 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5599 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5600 Throttle Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5601 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5602 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5603 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5604 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5605 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5606 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5607 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5608 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5609 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5610 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5611 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5612 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5613 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5614 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5615 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5616 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5617 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5618 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5619 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5620 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5621 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5622 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5623 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5624 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5625 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5626 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5627 TP Sensor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Diagrams > Page 5628 Throttle Position Sensor: Description and Operation Diagram The non-adjustable Throttle Position (TP) sensor is mounted on the throttle body assembly opposite the throttle lever. The TP sensor senses the throttle valve angle and relays that information to the VCM. Knowledge of throttle angle is one of the inputs needed by the VCM to generate the required injector control signals (pulses). For further information on replacement, refer to TP Sensor. See: Service and Repair Legend (1) Throttle Body Assembly. (2) IAC Valve Assembly 0-ring. (3) IAC Valve Assembly Attaching Screw. (4) Idle Air Control (IAC) Valve Assembly. (5) TP Sensor 0-ring (6) Throttle Position (TP) Sensor. (7) TP Sensor Attaching Screw. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Testing and Inspection > Throttle Position (TP) Sensor Throttle Position Sensor: Testing and Inspection Throttle Position (TP) Sensor When the VCM detects a malfunction with the Throttle Position (TP) sensor circuits, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0121 circuit performance ^ DTC P0122 circuit low. ^ DTC P0123 circuit high. ^ DTC P1121 intermittent circuit high. ^ DTC P1122 intermittent circuit low. Refer to Diagnostic Tables. See: Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Testing and Inspection > Throttle Position (TP) Sensor > Page 5631 Throttle Position Sensor: Testing and Inspection Throttle Position Sensor Output This check should be performed when Throttle Position (TP) sensor attaching parts have been replaced. A scan tool can be used to read the TP signal output voltage. 1. Connect digital voltmeter J 39200 from TP sensor connector terminal B (BLk wire) to terminal C (DK Blue wire). Jumpers for terminal access can be made using terminals 1214836 and 12014837. 2. With ignition ON, engine stopped, the TP signal voltage should be less than 1.25V if more than 1.25V verify free throttle movement. If still more than 1.25V, replace TP sensor. 3. Remove the voltmeter and jumpers, reconnect the TP sensor connector to the sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Testing and Inspection > Page 5632 Throttle Position Sensor: Service and Repair Throttle Position Sensor Electrical Connector REMOVAL PROCEDURE CAUTION: The Throttle Position (TP) sensor is an electrical component. Do not soak the TP sensor in any liquid cleaner or solvent, as damage may result. 1. Remove the air cleaner and adapter. 2. Disconnect the electrical connector releasing locking tab. 3. Remove the two TP sensor attaching screw assemblies. 4. Remove the TP sensor from throttle body assembly. 5. Remove the TP sensor seal. INSTALLATION PROCEDURE 1. Install the TP sensor seal over throttle shaft. 2. With throttle valve closed, install the TP sensor on the throttle shaft. Rotate counterclockwise to align mounting holes. 3. Install the two TP sensor attaching screw assemblies. Tighten ^ Tighten the screw assemblies to 2.0 Nm (18.0 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Throttle Position Sensor > Component Information > Testing and Inspection > Page 5633 4. Connect the electrical connector. 5. Install the air cleaner and adapter. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Technical Service Bulletins > A/T - Park/Neutral Switch Connector Cannot Be Removed Transmission Position Switch/Sensor: Technical Service Bulletins A/T - Park/Neutral Switch Connector Cannot Be Removed File In Section: 7 - Transmission Bulletin No.: 83-71-10 Date: May, 1998 Subject: Park (Neutral Position Switch Connector Cannot be Removed (Replace Switch and Connectors) Models: 1997-98 Chevrolet Corvette 1995-98 Chevrolet and GMC S/T Models 1996-98 Chevrolet and GMC M/L, P Models 1996-99 Chevrolet and GMC C/K, G Models 1996-98 Oldsmobile Bravada Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer conditions, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to insure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to insure water-tight connections. Parts Information P/N Description 12450016 Switch 15305925 4-Way Connector Assembly 15305887 7-Way Connector Assembly Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 5640 Transmission Position Switch/Sensor: Locations Park/Neutral Position Switch Electronic 4-Speed Automatic Overdrive Transmission Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 5641 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions Transmission Position Switch/Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5644 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5645 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5646 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5647 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5648 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5649 Transmission Position Switch/Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5650 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5651 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5652 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5653 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5654 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5655 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5656 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5657 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5658 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5659 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5660 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5661 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5662 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5663 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5664 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5665 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5666 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5667 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5668 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5669 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5670 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5671 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5672 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5673 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5674 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5675 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5676 Transmission Position Switch/Sensor: Connector Views C1: Transmission Range Switch C2: Transmission Range Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5677 Transmission Position Switch/Sensor: Electrical Diagrams Electronic PRNDL Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 5678 Starter And Charging (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 5679 Transmission Position Switch/Sensor: Testing and Inspection Pressure Switch Assembly Resistance Check (1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 5680 Pressure Switch Assembly Resistance Check (2 Of 2) Tools Required - J 39775 4L60E Jumper Harness - J 39200 Digital Multimeter - J 35616 Connector Test Adapter Kit Important: Whenever the transmission 20-way connector is disconnected and the engine is running, multiple DTCs will set. Be sure to clear these codes when you are finished with this procedure Important: This procedure tests the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) circuits and the Automatic Transmission Fluid Temperature (TFT) Sensor circuit. Do not use this procedure to test other Automatic Transmission circuits, refer to 4L60-E Automatic Transmission Internal Wiring Harness check. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 5681 Transmission Position Switch/Sensor: Adjustments PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 5682 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 5683 Transmission Position Switch/Sensor: Service and Repair PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 5684 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations Vehicle Speed Sensor: Component Locations 5-Speed Manual Transmission 5-Speed Manual Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 5689 5-Speed Manual Transmission (MW3) 5-Speed Manual Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 5690 5-Speed Manual Transmission Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 5691 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 5692 Electronic 4-Speed Automatic Overdrive Transmission Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 5693 Vehicle Speed Sensor: Connector Locations 5-Speed Manual Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Locations > Component Locations > Page 5694 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions Vehicle Speed Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5697 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5698 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5699 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5700 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5701 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5702 Vehicle Speed Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5703 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5704 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5705 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5706 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5707 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5708 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5709 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5710 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5711 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5712 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5713 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5714 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5715 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5716 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5717 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5718 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5719 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5720 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5721 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5722 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5723 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5724 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5725 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5726 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5727 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 5728 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor > Component Information > Diagrams > Page 5729 Vehicle Speed Sensor: Description and Operation Vehicle Speed Sensor (2WD) DESCRIPTION The Vehicle Speed Sensor (VSS) is a pulse counter type input that informs the VCM how fast the vehicle is being driven. The VSS system uses an inductive sensor mounted in the tail housing of the transmission and a toothed reluctor wheel on the tail shaft. OPERATION As the reluctor rotates, the teeth alternately interfere with the magnetic field of the sensor creating an induced voltage pulse. The VSS produces an AC voltage signal that increases with vehicle speed. The VCM processes this signal and sends it to the following components: ^ Instrument Panel. ^ Cruise Control Module. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor Signal Buffer > Component Information > Locations Instrument Panel Wiring, RH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Computers and Control Systems > Vehicle Speed Sensor Signal Buffer > Component Information > Locations > Page 5733 Vehicle Speed Sensor Buffer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Air Injection > Air Injection Pump > Component Information > Locations Air Injection Pump: Locations Front of Engine Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Air Injection > Air Injection Pump Clutch > Component Information > Locations Air Injection Pump Clutch: Locations On front of Pump Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Air Injection > Air Injection Pump Relay > Component Information > Locations Air Injection Pump Relay: Locations Underhood Fuse-Relay center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Catalytic Converter > Component Information > Locations > Utility 2 Door Catalytic Converter Location Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Catalytic Converter > Component Information > Locations > Utility 2 Door > Page 5749 Catalytic Converter Location Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Evaporative Emissions System > Canister Purge Solenoid > Component Information > Locations Engine Side, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Evaporative Emissions System > Canister Purge Solenoid > Component Information > Locations > Page 5754 Canister Purge Solenoid: Service and Repair Diagram Diagram Diagram REMOVAL PROCEDURE 1. Remove the purge solenoid electrical connector. 2. Remove the purge solenoid retaining bolts. 3. Remove the purge solenoid from the intake manifold. INSTALLATION PROCEDURE 1. Install the purge solenoid to the intake manifold. 2. Install the purge solenoid retaining bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Evaporative Emissions System > Canister Purge Solenoid > Component Information > Locations > Page 5755 3. Install the purge solenoid electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Evaporative Emissions System > Evaporative Emission Control Canister > Component Information > Service and Repair > Vapor Canister Replacement Evaporative Emission Control Canister: Service and Repair Vapor Canister Replacement EVAP Canister REMOVAL PROCEDURE 1. Disconnect the EVAP hoses from the canister. Mark the hoses for installation on the new canister. 2. Remove the screw from the mounting bracket and canister. INSTALLATION PROCEDURE 1. Install the EVAP canister and bracket screw. 2. Connect the EVAP hoses to canister. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Evaporative Emissions System > Evaporative Emission Control Canister > Component Information > Service and Repair > Vapor Canister Replacement > Page 5760 Evaporative Emission Control Canister: Service and Repair Vapor Canister Hose Replacement The EVAP pipe is secured to the underbody with clamp and screw assemblies. Flexible hoses are connected at the fuel tank and the EVAP canister. The pipe should be inspected occasionally for leaks, kinks, or dents and repaired as required. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Evaporative Emissions System > Evaporative Fuel Vapor Return Hose > Component Information > Service and Repair Evaporative Fuel Vapor Return Hose: Service and Repair EVAP Pipe Repair Repair the EVAP pipe in sections using brazed seamless steel tubing meeting GM specification 123M or equivalent or hose identified with the word Fluoroelastomer. Hose not so marked could cause failure or failure to meet emission standard. ^ Do not use copper or aluminum tubing to replace steel tubing. Those materials do not have satisfactory durability to withstand normal vehicle vibrations. ^ Do not use rubber hose within 100 mm (4 inches) of any part of the exhaust system or within 250 mm (10 inches) of the catalytic converter. The replacement hose's inside diameter must match the steel tubing outside diameter. 1. In repairable areas, cut a piece of fuel hose 100 mm (4 inches) longer than the portion of the line being removed. When more than a 150 mm (6 inches) length of pipe is removed, use a combination of steel tubing and hose so that the entire hose length will not be more than 250 mm (10 inches). 2. Cut the ends of the pipe remaining on the vehicle square by using a tubing cutter. By using the first step of a double flaring tool, form a bead on the ends of both pipe sections. If the pipe is too corroded to withstand bead operation without damage, the pipe should be replaced. If a new section of pipe is used, form a bead on both ends. 3. Use screw type hose clamps GM part number 2494772 or equivalent. Slide the clamps onto the pipe and push the hose 50 mm (2 inches) onto each portion of the fuel pipe. Tighten the clamps on each side of the repair. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Evaporative Emissions System > Thermal Vacuum Valve - EVAP > Component Information > Description and Operation Thermal Vacuum Valve - EVAP: Description and Operation EVAP Vacuum Switch The EVAP Purge Vacuum Switch is used by the VCM to monitor EVAP canister purge solenoid operation and purge system integrity. The EVAP Purge Vacuum Switch should be closed to ground with no vacuum present (0% EVAP Purge Pulse Width Modulation (PWM). With EVAP Purge PWM at 25% or greater, the EVAP Purge Vacuum Switch should open. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Evaporative Emissions System > Thermal Vacuum Valve - EVAP > Component Information > Description and Operation > Page 5767 Thermal Vacuum Valve - EVAP: Service and Repair EVAP Vacuum Switch REMOVAL PROCEDURE 1. Disconnect the EVAP vacuum switch electrical connector. 2. Disconnect the EVAP vacuum switch vacuum hoses. 3. Remove the EVAP vacuum switch. INSTALLATION PROCEDURE 1. Install the EVAP vacuum switch. 2. Connect the EVAP vacuum switch vacuum hoses. 3. Connect the EVAP vacuum switch electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > Recalls: > 97024 > Aug > 97 > Recall - Incorrect Exhaust Gas Recirculation Valve Used Technical Service Bulletin # 97024 Date: 970801 Recall - Incorrect Exhaust Gas Recirculation Valve Used Bulletin No.: 97024 Date: August, 1997 PRODUCT EMISSION CAMPAIGN SUBJECT: 97024 INCORRECT LINEAR EXHAUST GAS RECIRCULATION VALVES USED FOR SERVICE MODELS: 1996-1997 C/K, G AND P TRUCKS WITH 4.3L (L35/LF6), 5.0L (L30) AND 5.7L (L31) ENGINES General Motors has decided to conduct a Voluntary Emission Campaign involving certain 1996-97 C/K, S/T, M/L, G and P model vehicles equipped with 4.3L (RPO L35 or LF6), 5.0L (RPO L30), and 5.7L (RPO L31) engines. Due to Service Parts Catalog part number reference errors, these vehicles may have been serviced with an incorrect Linear Exhaust Gas Recirculation (LEGR) valve according to warranty records. An incorrect LEGR valve may cause the On-Board Diagnostic emission system to not operate as intended and/or cause driveability complaints. To correct this condition dealers are to install the correct LEGR valve on vehicles identified as having been serviced with incorrect part number. Vehicles Involved Involved are certain 1996-97 C/K, M/L, G and P model vehicles equipped with 4.3L (RPO L35 or LF6), 5.0L (RPO L30), and 5.7L (RPO L31) engines that were serviced with an incorrect Linear EGR valve. NOTICE: Dealers should confirm vehicle eligibility through VISS (Vehicle Information Service System) or ServiceNet (GMC only) prior to beginning campaign repairs. Involved vehicles have been identified by Vehicle Identification Number. Computer listings containing the complete Vehicle Identification Number, customer name and address data have been prepared, and are being furnished to involved dealers with the campaign bulletin. The customer name and address data furnished will enable dealers to follow-up with customers involved in this campaign. Any dealer not receiving a computer listing with the campaign bulletin has no involved vehicles currently assigned. These dealer listings may contain customer names and addresses obtained from State Motor Vehicle Registration Records. The use of such motor vehicle registration data (or any other purpose is a violation of law in several stales Accordingly, you are urged to limit the use of this listing to the follow-up necessary to complete this campaign. Parts Information Parts required-to-complete this campaign are to be obtained from General Motor Service Parts Operations (GMSPO). Please refer to your involved vehicles listing prior to ordering. Normal orders should be placed on a DRO = Daily Replenishment Order. An emergency requirement should be ordered on a CSO = Customer Special Order. Part Quantity/ Number Description Vehicle 17113405 Valve Assembly, EGR 1 12555896 Gasket, EGR 1 Customer Notification Customers will be notified of this campaign on their vehicles by General Motors (see copy of typical customer letter included with this bulletin actual divisional letter may vary slightly). In order to ensure full protection under the emission warranty, and the right to participate in future recalls, the customer notification letter recommends that customers have their vehicles serviced as soon as possible. It also advises that failure to do so could legally be determined to be lack of proper maintenance. Dealer Campaign Responsibility All unsold new vehicles in dealers possession and subject to this campaign must be held and inspected/repaired per the service procedure of this campaign bulletin before customers take possession of these vehicles. Dealers are to service all vehicles subject to this campaign at no charge to customers, regardless of mileage, age of vehicle or ownership, from this time forward. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > Recalls: > 97024 > Aug > 97 > Recall - Incorrect Exhaust Gas Recirculation Valve Used > Page 5777 Customers who have recently purchased vehicles sold from your vehicle inventory, and for which there is no customer information indicated on the dealer listing, are to be contacted by the dealer. Arrangements are to be made to make the required correction according to the instructions contained in this bulletin. This could be done by mailing to such customers a copy of the appropriate divisional customer letter accompanying this bulletin. Campaign follow up cards should not be used for this purpose, since the customer may not as yet have received the notification letter. In summary, whenever a vehicle subject to this campaign enters your vehicle inventory, or is in your dealership for service in the future, please take the steps necessary to be sure the campaign correction has been made before selling or releasing the vehicle. When a California emissions campaign is completed by a GM dealer, the dealer must provide the vehicle owner a "Proof Of Correction Certificate: which the owner may need to present to the California Department Of Motor Vehicles (DMV) when renewing their vehicle registration. Without this correction certificate, the owner may be unable to renew their vehicle registration. Additional Certificates can be obtained, at no charge, from VISPAC, Incorporated by calling 1-800-269-5100, Monday through Friday, 8:00 A.M. to 4:30 P.M. Eastern Standard Time. Ask for GM Item Number 1825 when ordering. Service Procedure 1. Remove air cleaner element (G/P, and M/L only). 2. Loosen air inlet pipe clamp closet to the air intake bonnet assembly (G/P, and M/L only). 3. Remove the air intake bonnet assembly (G/P, and M/L only). 4. Disconnect the linear EGR valve electrical connector. 5. Remove the EGR valve attaching bolts. 6. Remove the EGR valve and gasket. 7. Install new gasket p/n 12555896. 8. Install new EGR valve p/n 17113405. Important: The gasket and valve must be properly aligned as shown in Figure 1 such that the electrical connection terminal on the EGR valve is approximately in the nine o'clock position or on the left, when facing the front of engine. 9. Reinstall fastening bolts. Tighten bolts the first time to 10 Nm (89 lb.in.) each. Tighten bolts a final time to 25 Nm (18 lb.ft.) each. 10. Install the electrical connector. 11. Reinstall the air intake bonnet assembly (G/P, and M/L only). 12. Tighten air inlet pipe clamp closest to the air intake bonnet assembly (G/P, and M/L only). 13. Reinstall air cleaner element (G/P, and M/L only). 14. Install the GM Campaign Identification Label. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > Recalls: > 97024 > Aug > 97 > Recall - Incorrect Exhaust Gas Recirculation Valve Used > Page 5778 15. California dealers only, provide owner with a "Vehicle Emission Recall Proof Of Correction" certificate. Campaign Identification Label Each vehicle corrected in accordance with the instructions outlined in this Product Campaign Bulletin will require a "Campaign Identification Label". Each label provides a space to include the campaign number and the five (5) digit dealer code of the dealer performing the campaign service. This information may be inserted with a typewriter or a ball point pen. Each "Campaign Identification Label" is to be located on the radiator core support in an area which will be visible when the vehicle is brought in by the customer for periodic servicing. When installing the Campaign Identification Label, be sure to install the clear protective covering. Additional Campaign Identification Labels can be obtained from VISPAC Incorporated by calling 1-800-259-5100 (Monday-Friday, 8:00 a.m. to 4:30 p.m. EST). Ask for item Number S-1015 when ordering. Apply the "Campaign Identification Label" only on a clean, dry surface. Claim Information Submit a Product Campaign Claim with the information indicated. Refer to the General Motors Corporation Claims Processing Manual for details on Product Campaign Claim Submissions. Owner Letter 97024 (Sample of Notification Used) August 1997 Dear Customer: This notice is sent to inform you that General Motors is conducting a voluntary emission recall campaign that includes your vehicle. Reason For This Recall: General Motors has decided that certain 1996-97 C/K, G, P, S/T and M/L model vehicles equipped with 4.3L, 5.0L and 5.7L engines may have been serviced with an incorrect Linear Exhaust Gas Recirculation valve, due to Service Parts Catalog part number reference errors. According to GM warranty repair records, your vehicle is one of the affected models that has had an incorrect valve installed during service. An incorrect valve may cause your On-Board Diagnostic emission system to not operate as intended and/or cause driveability complaints. What Will Be Done: To correct this condition, your dealer will install the correct valve on your vehicle. This service will be performed for you at no charge. Contacting Your Dealer: Please contact your dealer as soon as possible to arrange a service date and to assure parts availability instructions for making this correction have been Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > Recalls: > 97024 > Aug > 97 > Recall - Incorrect Exhaust Gas Recirculation Valve Used > Page 5779 sent to your dealer. Please ask your dealer if you wish to know how much time will be need to schedule, process and repair your vehicle. Should your dealer be unable to schedule a service date within a reasonable time, you should contact the appropriate Customer Assistance/Relations Center at the listed number below: Deaf, Hearing Impaired Division Number or Speech Impaired * Chevrolet 1-800-222-1020 1-800-833-2438 GMC 1-800-462-8782 1-800-462-8583 Oldsmobile 1-800-442-6537 1-800-833-8537 * Utilizes Telecommunication Devices for the Deaf/Text Telephones (TDD/TTY) Customer Reply Card: The enclosed customer reply card identifies your vehicle. Presentation of this card to your dealer will assist in making the necessary correction in the shortest possible time. If you no longer own this vehicle, please let us know by completing the postage paid reply card and returning it to us. Emission Law Information: In order to ensure your full protection under the emission warranty made applicable to your vehicle by State or Federal Law, and vehicle serviced as soon as possible. Failure to do so could legally be determined to be lack of proper maintenance of your vehicle. Also, your vehicle may fail a state or local emission inspection if this recall is not accomplished. IMPORTANT MESSAGE FOR CALIFORNIA RESIDENTS The California Air Resources Board (CARB) requires vehicle emission recall campaigns be completed prior to California registration renewal. Uncorrected emission recall campaigns will result in the inability to renew your California vehicle registration. At the time of emission campaign completion, your California dealer will issue a "Proof Of Correction Certificate". Keep this certificate and, if required, present it to the Department of Motor Vehicles when renewing your California registration as proof of campaign completion. We are sorry to cause you this inconvenience; however, we have taken this action in the interest of your continued satisfaction with our products. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > All Technical Service Bulletins for EGR Valve: > 97024 > Aug > 97 > Recall - Incorrect Exhaust Gas Recirculation Valve Used Technical Service Bulletin # 97024 Date: 970801 Recall - Incorrect Exhaust Gas Recirculation Valve Used Bulletin No.: 97024 Date: August, 1997 PRODUCT EMISSION CAMPAIGN SUBJECT: 97024 INCORRECT LINEAR EXHAUST GAS RECIRCULATION VALVES USED FOR SERVICE MODELS: 1996-1997 C/K, G AND P TRUCKS WITH 4.3L (L35/LF6), 5.0L (L30) AND 5.7L (L31) ENGINES General Motors has decided to conduct a Voluntary Emission Campaign involving certain 1996-97 C/K, S/T, M/L, G and P model vehicles equipped with 4.3L (RPO L35 or LF6), 5.0L (RPO L30), and 5.7L (RPO L31) engines. Due to Service Parts Catalog part number reference errors, these vehicles may have been serviced with an incorrect Linear Exhaust Gas Recirculation (LEGR) valve according to warranty records. An incorrect LEGR valve may cause the On-Board Diagnostic emission system to not operate as intended and/or cause driveability complaints. To correct this condition dealers are to install the correct LEGR valve on vehicles identified as having been serviced with incorrect part number. Vehicles Involved Involved are certain 1996-97 C/K, M/L, G and P model vehicles equipped with 4.3L (RPO L35 or LF6), 5.0L (RPO L30), and 5.7L (RPO L31) engines that were serviced with an incorrect Linear EGR valve. NOTICE: Dealers should confirm vehicle eligibility through VISS (Vehicle Information Service System) or ServiceNet (GMC only) prior to beginning campaign repairs. Involved vehicles have been identified by Vehicle Identification Number. Computer listings containing the complete Vehicle Identification Number, customer name and address data have been prepared, and are being furnished to involved dealers with the campaign bulletin. The customer name and address data furnished will enable dealers to follow-up with customers involved in this campaign. Any dealer not receiving a computer listing with the campaign bulletin has no involved vehicles currently assigned. These dealer listings may contain customer names and addresses obtained from State Motor Vehicle Registration Records. The use of such motor vehicle registration data (or any other purpose is a violation of law in several stales Accordingly, you are urged to limit the use of this listing to the follow-up necessary to complete this campaign. Parts Information Parts required-to-complete this campaign are to be obtained from General Motor Service Parts Operations (GMSPO). Please refer to your involved vehicles listing prior to ordering. Normal orders should be placed on a DRO = Daily Replenishment Order. An emergency requirement should be ordered on a CSO = Customer Special Order. Part Quantity/ Number Description Vehicle 17113405 Valve Assembly, EGR 1 12555896 Gasket, EGR 1 Customer Notification Customers will be notified of this campaign on their vehicles by General Motors (see copy of typical customer letter included with this bulletin actual divisional letter may vary slightly). In order to ensure full protection under the emission warranty, and the right to participate in future recalls, the customer notification letter recommends that customers have their vehicles serviced as soon as possible. It also advises that failure to do so could legally be determined to be lack of proper maintenance. Dealer Campaign Responsibility All unsold new vehicles in dealers possession and subject to this campaign must be held and inspected/repaired per the service procedure of this campaign bulletin before customers take possession of these vehicles. Dealers are to service all vehicles subject to this campaign at no charge to customers, regardless of mileage, age of vehicle or ownership, from this time forward. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > All Technical Service Bulletins for EGR Valve: > 97024 > Aug > 97 > Recall - Incorrect Exhaust Gas Recirculation Valve Used > Page 5785 Customers who have recently purchased vehicles sold from your vehicle inventory, and for which there is no customer information indicated on the dealer listing, are to be contacted by the dealer. Arrangements are to be made to make the required correction according to the instructions contained in this bulletin. This could be done by mailing to such customers a copy of the appropriate divisional customer letter accompanying this bulletin. Campaign follow up cards should not be used for this purpose, since the customer may not as yet have received the notification letter. In summary, whenever a vehicle subject to this campaign enters your vehicle inventory, or is in your dealership for service in the future, please take the steps necessary to be sure the campaign correction has been made before selling or releasing the vehicle. When a California emissions campaign is completed by a GM dealer, the dealer must provide the vehicle owner a "Proof Of Correction Certificate: which the owner may need to present to the California Department Of Motor Vehicles (DMV) when renewing their vehicle registration. Without this correction certificate, the owner may be unable to renew their vehicle registration. Additional Certificates can be obtained, at no charge, from VISPAC, Incorporated by calling 1-800-269-5100, Monday through Friday, 8:00 A.M. to 4:30 P.M. Eastern Standard Time. Ask for GM Item Number 1825 when ordering. Service Procedure 1. Remove air cleaner element (G/P, and M/L only). 2. Loosen air inlet pipe clamp closet to the air intake bonnet assembly (G/P, and M/L only). 3. Remove the air intake bonnet assembly (G/P, and M/L only). 4. Disconnect the linear EGR valve electrical connector. 5. Remove the EGR valve attaching bolts. 6. Remove the EGR valve and gasket. 7. Install new gasket p/n 12555896. 8. Install new EGR valve p/n 17113405. Important: The gasket and valve must be properly aligned as shown in Figure 1 such that the electrical connection terminal on the EGR valve is approximately in the nine o'clock position or on the left, when facing the front of engine. 9. Reinstall fastening bolts. Tighten bolts the first time to 10 Nm (89 lb.in.) each. Tighten bolts a final time to 25 Nm (18 lb.ft.) each. 10. Install the electrical connector. 11. Reinstall the air intake bonnet assembly (G/P, and M/L only). 12. Tighten air inlet pipe clamp closest to the air intake bonnet assembly (G/P, and M/L only). 13. Reinstall air cleaner element (G/P, and M/L only). 14. Install the GM Campaign Identification Label. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > All Technical Service Bulletins for EGR Valve: > 97024 > Aug > 97 > Recall - Incorrect Exhaust Gas Recirculation Valve Used > Page 5786 15. California dealers only, provide owner with a "Vehicle Emission Recall Proof Of Correction" certificate. Campaign Identification Label Each vehicle corrected in accordance with the instructions outlined in this Product Campaign Bulletin will require a "Campaign Identification Label". Each label provides a space to include the campaign number and the five (5) digit dealer code of the dealer performing the campaign service. This information may be inserted with a typewriter or a ball point pen. Each "Campaign Identification Label" is to be located on the radiator core support in an area which will be visible when the vehicle is brought in by the customer for periodic servicing. When installing the Campaign Identification Label, be sure to install the clear protective covering. Additional Campaign Identification Labels can be obtained from VISPAC Incorporated by calling 1-800-259-5100 (Monday-Friday, 8:00 a.m. to 4:30 p.m. EST). Ask for item Number S-1015 when ordering. Apply the "Campaign Identification Label" only on a clean, dry surface. Claim Information Submit a Product Campaign Claim with the information indicated. Refer to the General Motors Corporation Claims Processing Manual for details on Product Campaign Claim Submissions. Owner Letter 97024 (Sample of Notification Used) August 1997 Dear Customer: This notice is sent to inform you that General Motors is conducting a voluntary emission recall campaign that includes your vehicle. Reason For This Recall: General Motors has decided that certain 1996-97 C/K, G, P, S/T and M/L model vehicles equipped with 4.3L, 5.0L and 5.7L engines may have been serviced with an incorrect Linear Exhaust Gas Recirculation valve, due to Service Parts Catalog part number reference errors. According to GM warranty repair records, your vehicle is one of the affected models that has had an incorrect valve installed during service. An incorrect valve may cause your On-Board Diagnostic emission system to not operate as intended and/or cause driveability complaints. What Will Be Done: To correct this condition, your dealer will install the correct valve on your vehicle. This service will be performed for you at no charge. Contacting Your Dealer: Please contact your dealer as soon as possible to arrange a service date and to assure parts availability instructions for making this correction have been Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > All Technical Service Bulletins for EGR Valve: > 97024 > Aug > 97 > Recall - Incorrect Exhaust Gas Recirculation Valve Used > Page 5787 sent to your dealer. Please ask your dealer if you wish to know how much time will be need to schedule, process and repair your vehicle. Should your dealer be unable to schedule a service date within a reasonable time, you should contact the appropriate Customer Assistance/Relations Center at the listed number below: Deaf, Hearing Impaired Division Number or Speech Impaired * Chevrolet 1-800-222-1020 1-800-833-2438 GMC 1-800-462-8782 1-800-462-8583 Oldsmobile 1-800-442-6537 1-800-833-8537 * Utilizes Telecommunication Devices for the Deaf/Text Telephones (TDD/TTY) Customer Reply Card: The enclosed customer reply card identifies your vehicle. Presentation of this card to your dealer will assist in making the necessary correction in the shortest possible time. If you no longer own this vehicle, please let us know by completing the postage paid reply card and returning it to us. Emission Law Information: In order to ensure your full protection under the emission warranty made applicable to your vehicle by State or Federal Law, and vehicle serviced as soon as possible. Failure to do so could legally be determined to be lack of proper maintenance of your vehicle. Also, your vehicle may fail a state or local emission inspection if this recall is not accomplished. IMPORTANT MESSAGE FOR CALIFORNIA RESIDENTS The California Air Resources Board (CARB) requires vehicle emission recall campaigns be completed prior to California registration renewal. Uncorrected emission recall campaigns will result in the inability to renew your California vehicle registration. At the time of emission campaign completion, your California dealer will issue a "Proof Of Correction Certificate". Keep this certificate and, if required, present it to the Department of Motor Vehicles when renewing your California registration as proof of campaign completion. We are sorry to cause you this inconvenience; however, we have taken this action in the interest of your continued satisfaction with our products. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > All Technical Service Bulletins for EGR Valve: > 61-65-59 > Dec > 96 > Engine Controls - Clear DTC's After PCM/VCM/EGR Service EGR Valve: All Technical Service Bulletins Engine Controls - Clear DTC's After PCM/VCM/EGR Service File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-59 Date: December, 1996 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Clear DTCs after PCM or VCM Replacement/Programming or EGR Valve Replacement Models: 1997 Buick Skylark 1997 Chevrolet Cavalier, Malibu 1997 Oldsmobile Achieva, Cutlass 1997 Pontiac Grand Am, Sunfire 1995-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 2.2L, 2.4L, 4.3L, 5.0L, 5.7L, 7.4L Engine (VINs 4, T, J, M, R, W, X - RPOs LN2, LD9, L29, L30, L31, L35, LF6) PCM Equipped Vehicles This bulletin is being issued to revise the 1997 GMP/97-N-2, 1997 GMP/97-J-2 and 1997 GMT/97-ST-2 Service Manuals. Make the following revisions to the EGR replacement P0404, DTC P0405, DTC P1404 and PCM EEPROM reprogramming sections of the Service Manual due to possible setting of EGR DTCs after performing these procedures. Clear DTCs from the PCM anytime either the PCM is reprogrammed or the EGR valve is replaced, or anytime the ignition switch is turned on with the EGR valve electrical connector disconnected. This is due to the auto zeroing function of the PCM on the EGR pintle. VCM Equipped Trucks This bulletin updates the following Service Manuals: 1997 1997 1997 GMT/97-ST-2 GMT/97-CK-2 GMT/97-ML-2 1997 1997 1997 GMT/97-G6-2 GMT/97-P3-2 GMT/96-ST-2 1996 1996 1996 GMT/96-CK-2 GMT/96-ML-2 GMT/96-G6-2 1996 1995 1995 GMT/96-P3-2 GMT/95-ST-2 GMT/95-CK-2 1995 1995 1995 GMT/95-ML-2 GMT/95-G6-2 GMT/95-P3-2 Add the following revision to these Engine Controls sections: EGR Valve Replacement, VCM Replacement/Programming, EGR System Diagnosis, DTC P0401 and DTC P1406. Clear any DTCs from the VCM anytime after doing VCM Replacement/programming, turning the ignition ON while the EGR valve is disconnected, or replacing the EGR valve. Please make a note of these revisions in your Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > All Technical Service Bulletins for EGR Valve: > 576528 > Jan > 96 > Linear EGR Valve - Installation EGR Valve: All Technical Service Bulletins Linear EGR Valve - Installation File In Section: 6E - Engine Fuel & Emission Bulletin No.: 57-65-28 Date: January, 1996 INFORMATION Subject: Linear EGR Valve Installation Models: 1993-96 Chevrolet and GMC Truck S/T; M/L, C/K, P, G Models 1993-94 Oldsmobile Bravada 1996 Oldsmobile Bravada with 4.3L V6, 5.0L V8, 5.7L V8 Engine (VINs W, X, M, R RPOs L35, LF6, L30, L31) When installing Linear EGR Valves, take care to orientate the valve properly before installation. It is possible to rotate the Linear EGR valve 18O°, and then install it on the intake manifold. Notice: Linear EGR Valves improperly installed do not function as intended. Possible driveability concerns include a rough idle and the setting of codes DTC 32 (EGR Error) or DTC 1406 (Pintle Position Error). Linear EGR Valves improperly installed may respond to high vacuum conditions (at idle) by pulling the valve open, or high back pressure conditions by pushing the valve open. When replacing or re-installing a LEGR valve, install the valve (with a new gasket) in the correct orientation. A new insulated gasket for use with this valve has been released for production and service. (figure 1) Linear EGR Legend Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > All Technical Service Bulletins for EGR Valve: > 576528 > Jan > 96 > Linear EGR Valve - Installation > Page 5796 (figure 1) Linear EGR Legend See figures. Parts Information Application Description Service P/N All Linear EGR Valves Gasket Only 12555896 Important: The new gasket must be used whenever a LEGR valve is removed and reinstalled. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > All Technical Service Bulletins for EGR Valve: > 576528 > Jan > 96 > Linear EGR Valve - Installation > Page 5797 Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > All Other Service Bulletins for EGR Valve: > 61-65-59 > Dec > 96 > Engine Controls - Clear DTC's After PCM/VCM/EGR Service EGR Valve: All Technical Service Bulletins Engine Controls - Clear DTC's After PCM/VCM/EGR Service File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-59 Date: December, 1996 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Clear DTCs after PCM or VCM Replacement/Programming or EGR Valve Replacement Models: 1997 Buick Skylark 1997 Chevrolet Cavalier, Malibu 1997 Oldsmobile Achieva, Cutlass 1997 Pontiac Grand Am, Sunfire 1995-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 2.2L, 2.4L, 4.3L, 5.0L, 5.7L, 7.4L Engine (VINs 4, T, J, M, R, W, X - RPOs LN2, LD9, L29, L30, L31, L35, LF6) PCM Equipped Vehicles This bulletin is being issued to revise the 1997 GMP/97-N-2, 1997 GMP/97-J-2 and 1997 GMT/97-ST-2 Service Manuals. Make the following revisions to the EGR replacement P0404, DTC P0405, DTC P1404 and PCM EEPROM reprogramming sections of the Service Manual due to possible setting of EGR DTCs after performing these procedures. Clear DTCs from the PCM anytime either the PCM is reprogrammed or the EGR valve is replaced, or anytime the ignition switch is turned on with the EGR valve electrical connector disconnected. This is due to the auto zeroing function of the PCM on the EGR pintle. VCM Equipped Trucks This bulletin updates the following Service Manuals: 1997 1997 1997 GMT/97-ST-2 GMT/97-CK-2 GMT/97-ML-2 1997 1997 1997 GMT/97-G6-2 GMT/97-P3-2 GMT/96-ST-2 1996 1996 1996 GMT/96-CK-2 GMT/96-ML-2 GMT/96-G6-2 1996 1995 1995 GMT/96-P3-2 GMT/95-ST-2 GMT/95-CK-2 1995 1995 1995 GMT/95-ML-2 GMT/95-G6-2 GMT/95-P3-2 Add the following revision to these Engine Controls sections: EGR Valve Replacement, VCM Replacement/Programming, EGR System Diagnosis, DTC P0401 and DTC P1406. Clear any DTCs from the VCM anytime after doing VCM Replacement/programming, turning the ignition ON while the EGR valve is disconnected, or replacing the EGR valve. Please make a note of these revisions in your Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > All Other Service Bulletins for EGR Valve: > 576528 > Jan > 96 > Linear EGR Valve - Installation EGR Valve: All Technical Service Bulletins Linear EGR Valve - Installation File In Section: 6E - Engine Fuel & Emission Bulletin No.: 57-65-28 Date: January, 1996 INFORMATION Subject: Linear EGR Valve Installation Models: 1993-96 Chevrolet and GMC Truck S/T; M/L, C/K, P, G Models 1993-94 Oldsmobile Bravada 1996 Oldsmobile Bravada with 4.3L V6, 5.0L V8, 5.7L V8 Engine (VINs W, X, M, R RPOs L35, LF6, L30, L31) When installing Linear EGR Valves, take care to orientate the valve properly before installation. It is possible to rotate the Linear EGR valve 18O°, and then install it on the intake manifold. Notice: Linear EGR Valves improperly installed do not function as intended. Possible driveability concerns include a rough idle and the setting of codes DTC 32 (EGR Error) or DTC 1406 (Pintle Position Error). Linear EGR Valves improperly installed may respond to high vacuum conditions (at idle) by pulling the valve open, or high back pressure conditions by pushing the valve open. When replacing or re-installing a LEGR valve, install the valve (with a new gasket) in the correct orientation. A new insulated gasket for use with this valve has been released for production and service. (figure 1) Linear EGR Legend Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > All Other Service Bulletins for EGR Valve: > 576528 > Jan > 96 > Linear EGR Valve - Installation > Page 5807 (figure 1) Linear EGR Legend See figures. Parts Information Application Description Service P/N All Linear EGR Valves Gasket Only 12555896 Important: The new gasket must be used whenever a LEGR valve is removed and reinstalled. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > All Other Service Bulletins for EGR Valve: > 576528 > Jan > 96 > Linear EGR Valve - Installation > Page 5808 Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > Page 5809 EGR Valve: Specifications Valve To Flange Bolts Torques Valve To Flange Bolts Torques Valve To Flange Bolts First Time 89 in.lb Note: Each Valve To Flange Bolts Final Time 18 in.lb Note: Each Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > Page 5810 Engine Side, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > Page 5811 Linear EGR Valve Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > Page 5812 EGR Valve: Description and Operation Exhaust Gas Flow EGR Valve Subassemblies DESCRIPTION The control module command exclusively operates the linear Exhaust Gas Recirculation (EGR) valve (1). The control module monitors the following various engine parameters: ^ The Throttle Position (TP) sensor. ^ The Manifold Absolute Pressure (MAP). ^ The Engine Coolant Temperature (ECT) sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > Page 5813 ^ The EGR Pintle position sensor. Output messages are then sent to the EGR system indicating the proper amount of exhaust gas (2) recirculation [with intake air (3)] necessary in order to lower the combustion temperatures. This electronic metering of exhaust gas is ten times faster than the vacuum-operated models as well as an improved diagnostic capabilities. CONNECTOR Positioned at the top of the linear EGR assembly are 5 terminals. ^ A is the pulse width modulated negative signal from the control module. ^ B is the sensor ground. ^ C is the sensor output. ^ D is the +5 volts supply. E is the positive from ignition. OPERATION A 12 volt current which enters the valve through an electrical connector (terminal E) energizes the solenoid (bobbin and coil) assembly (3). The 12 volt current then flows through the solenoid assembly to the control module and creates an electromagnetic field. This field causes the armature assembly (4,6) to be pulled upward, lifting the pintle (5) a variable amount off the base. The exhaust gas then flows from the exhaust manifold through the orifice into the intake manifold. The pintle position sensor (2,1-sensor cap) reads the height of the pintle, and the control module closes the loop on a desired position versus the actual position read. This changes the pulse width modulated command to the solenoid accordingly, until the actual pintle position equals the desired pintle position. The linear EGR valve is unique in that the control module continuously monitors the pintle height and continuously corrects it in order to obtain accurate flow, making linear EGR a Closed Loop system. When the solenoid is de-energized (the control module breaks the circuit), the pintle seals against the orifice, blocking the exhaust flow to the intake manifold. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Exhaust Gas Recirculation > EGR Valve > Component Information > Technical Service Bulletins > Page 5814 EGR Valve: Service and Repair Linear EGR Valve **THIS REPAIR PROCEDURE HAS BEEN UPDATED BY TSB 57-65-28** REMOVAL PROCEDURE NOTES ^ Do not try to disassemble the linear EGR valve. Service only as a complete assembly. ^ When installing Linear EGR Valves, take care to orientate the valve properly before installation. It is possible to rotate the Linear EGR valve 18O°, and then install it on the intake manifold. ^ Linear EGR Valves improperly installed do not function as intended. Possible driveability concerns include a rough idle and the setting of code DTC 1406 (Pintle Position Error). ^ Linear EGR Valves improperly installed may respond to high vacuum conditions (at idle) by pulling the valve open, or high back pressure conditions by pushing the valve open. ^ When replacing or re-installing a LEGR valve, install the valve (with a new gasket) in the correct orientation. A new insulated gasket for use with this valve has been released for production and service. ^ The new gasket must be used whenever a LEGR valve is removed and reinstalled. CAUTION: The Linear EGR valve is an electrical component. DO NOT soak in any liquid cleaner or solvent because damage may result. 1. Remove the electrical connector. 2. Remove the valve to flange attaching bolts. 3. Remove the linear EGR valve. 4. Remove the flange gasket. INSTALLATION PROCEDURE 1. Install the new flange gasket 2. Install the linear EGR valve. 3. Install the Valve to flange bolts. Tighten 3.1. Tighten the bolts the first time to 10 Nm (89 lb. in.) each. 3.2. Tighten the bolts a final time to 25 Nm (18 lb. ft.) each. 4. Install the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Fillpipe Restrictor > Component Information > Description and Operation Fillpipe Restrictor: Description and Operation DESCRIPTION To prevent refueling with leaded fuel, the fuel filler neck is equipped with restrictor and deflector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Positive Crankcase Ventilation > Component Information > Technical Service Bulletins > Crankcase Ventilation System - Revised Maintenance Positive Crankcase Ventilation: Technical Service Bulletins Crankcase Ventilation System Revised Maintenance File In Section: 0 - General Information Bulletin No.: 83-02-01 Date: September, 1998 SERVICE MANUAL UPDATE Subject: Section OB - Corrected Crankcase Ventilation System Maintenance Models: 1994-98 All Passenger Cars and Trucks Some Service Manuals for the affected vehicles contain an error in Section OB - Maintenance and Lubrication. The error is incorrect crankcase ventilation system maintenance recommendations. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Positive Crankcase Ventilation > Component Information > Technical Service Bulletins > Crankcase Ventilation System - Revised Maintenance > Page 5822 The chart that follows has the correct crankcase ventilation system maintenance recommendations. Owners Manual maintenance schedules for the above vehicles have correct crankcase ventilation system maintenance recommendations. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Positive Crankcase Ventilation > Component Information > Technical Service Bulletins > Page 5823 Positive Crankcase Ventilation: Description and Operation Crankcase Ventilation Valve Cross Section EVAP System DESCRIPTION A crankcase ventilation system is used in order to provide a more complete scavenging of crankcase vapors. The air cleaner supplies fresh air through a filter to the crankcase. The crankcase mixes the fresh air with blow-by gases. This mixture then passes through a crankcase ventilation valve into the intake manifold. The primary control is through the crankcase ventilation valve (1), which meters the flow at a rate depending on the manifold vacuum. In order to maintain an idle quality, the crankcase ventilation valve restricts the flow when the intake manifold vacuum is high. If abnormal operating conditions arise, the system is designed to allow the excessive amounts of blow-by gases to back flow through the crankcase vent tube into the air cleaner in order to be consumed by normal combustion. The Evaporative Emission (EVAP) control system limits the fuel vapors from escaping into the atmosphere. The EVAP transfers the fuel vapor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Positive Crankcase Ventilation > Component Information > Technical Service Bulletins > Page 5824 from the sealed fuel tank to an activated carbon (charcoal) storage device (EVAP canister). The EVAP canister stores the vapors until the engine is able to use the extra fuel vapor. When the engine is able to use the extra fuel vapor, the intake air flow purges the fuel vapor from the carbon element, and then the normal combustion process consumes the fuel vapor. The system is required in order to detect the evaporative fuel system leaks as small as 0.040 between the fuel filler cap and the purge solenoid. The system can test the evaporative system integrity by applying a vacuum signal (ported or manifold) to the fuel tank in order to create a small vacuum. OPERATION The Control Module then monitors the ability of the system to maintain the vacuum. If the vacuum remains for a specified period of time, then there are no evaporative leaks, and a PASS report is sent to the control module. If there is a leak, the system either will not achieve a vacuum, or a vacuum cannot be maintained. Usually a fault can only be detected after a cold start with a trip of sufficient length and driving conditions to run the needed tests. The enhanced evaporative system diagnostic conducts up to 8 specific sub-tests in order to detect the fault conditions. If the diagnostic fails a sub-test, the Control Module stores a Diagnostic Trouble Code (DTC) in order to indicate the type of fault detected. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Positive Crankcase Ventilation > Component Information > Technical Service Bulletins > Page 5825 Positive Crankcase Ventilation: Testing and Inspection RESULTS OF INCORRECT OPERATION A plugged valve or hose may cause: Rough idle. - Stalling or slow idle speed. - Oil leakage. - Oil in air cleaner. - Sludge in engine. A leaking Positive Crankcase Ventilation (PCV) valve or hose will cause: Rough idle. - Stalling. - High idle speeds. FUNCTIONAL CHECK With these systems, any blow-by in excess of the system capacity (from a badly worn engine, sustained heavy load, etc.) is exhausted into the air cleaner and is drawn into the engine. Proper operation of the crankcase ventilation system is dependent upon a sealed engine. If oil sludging or dilution is noted and the crankcase ventilation system is functioning properly, check the engine for possible cause and correct to ensure that the system will function as intended. If an engine is idling rough, check for a clogged crankcase ventilation valve, dirty vent filter, air cleaner element, or plugged hose. Replace as required. Use the following procedure: 1. Remove crankcase ventilation valve from the rocker cover. 2. Operate engine at idle. 3. Place your thumb over the end of the valve to check for vacuum. If there is NO vacuum at the valve, check: For plugged hoses. - Manifold port. - Crankcase ventilation valve. 4. Turn "OFF" the engine and remove crankcase ventilation valve. Shake the valve and listen for the rattle of the check needle inside of the valve. If it does NOT rattle, replace the valve. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Positive Crankcase Ventilation > Component Information > Technical Service Bulletins > Page 5826 Positive Crankcase Ventilation: Service and Repair CAUTION: An engine can be damaged if it is operated without crankcase ventilation. Therefore, it is important to perform the "Functional Check". Refer to System Diagnosis / Procedures. See: Testing and Inspection ^ Replace crankcase ventilation components as diagnosis requires. ^ Periodically, inspect the hoses and clamps and replace any showing signs of deterioration. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Emission Control Systems > Relays and Modules - Emission Control Systems > Air Injection Pump Relay > Component Information > Locations Air Injection Pump Relay: Locations Underhood Fuse-Relay center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pressure > Diagnostic Connector - Fuel Pump > Component Information > Locations Diagnostic Connector - Fuel Pump: Locations For Fuel Pump Prime and Run Connector, See Computer and Control Systems, Data Link Connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pressure Release > System Information > Service and Repair Fuel Pressure Release: Service and Repair TOOLS REQUIRED - J 34730 Fuel Pressure Gauge WARNING: Relieve the fuel system pressure before servicing fuel system components In order to reduce the risk of fire and personal Injury. After relieving the system pressure, a small amount of fuel may be released when servicing the fuel lines or connections. In order to reduce the chance of personal Injury, cover the regulator and the fuel line fittings with a shop towel before disconnecting. This will catch any fuel that may leak out. Place the towel In an approved container when the disconnection Is complete. 1. Disconnect the negative battery cable in order to avoid possible fuel discharge if an accidental attempt is made to start the engine. 2. Loosen the fuel filler cap in order to relieve the tank vapor pressure. 3. Connect the gauge J 34730-1A or the equivalent to the fuel pressure connection. 4. Wrap a shop towel around the fitting while connecting the gauge in order to avoid spillage. 5. Install the bleed hose into an approved container and open valve in order to bleed the system pressure. The fuel connections are now safe for servicing. 6. Drain any fuel remaining in gauge into an approved container. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Speed > System Information > Specifications > Controlled Idle Speed Idle Speed: Specifications Controlled Idle Speed Under 8500 GVW Transmission Gear Idle Speed IAC Counts [1] OPEN/CLOSED Loop [2] Manual N 675 +/- 25 Varies CL Automatic D 550 +/- 25 Varies CL [1] On manual transmission vehicles the SCAN tool will display RDL in Neutral. Add 2 counts for engines with less than 500 miles. Add 2 counts for every 1000 ft. above sea level. [2] Let engine idle until proper fuel control status is reached (OPEN/CLOSED loop). Note: Engine should be at operating temperature 92°C to 104° (196°F to 222°F). Over 8500 GVW Transmission Gear Idle Speed IAC Counts [1] OPEN/CLOSED Loop [2] Manual N 675 +/- 25 Varies CL Automatic D 550 +/- 25 Varies CL [1] On manual transmission vehicles the SCAN tool will display RDL in Neutral. Add 2 counts for engines with less than 500 miles. Add 2 counts for every 1000 ft. above sea level. [2] Let engine idle until proper fuel control status is reached (OPEN/CLOSED loop). Note: Engine should be at operating temperature 92°C to 104° (196°F to 222°F). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Speed > System Information > Adjustments > Controlled Idle Speed Idle Speed: Adjustments Controlled Idle Speed NOTE: There should be no Diagnostic Trouble Code (DTC)s displayed. The idle air control system has been checked. 1. Set the parking brake. 2. Block the drive wheels. 3. Connect a scan tool to the Data Link Connector (DLC) connector with the tool in the open mode. 4. Start the engine. 5. Bring the engine to the normal operating temperature. 6. Check for the correct state of the Transmission Range (TR) switch position on the scan tool. 7. Check the specifications for controlled idle speed and Idle Air Control (IAC) valve pintle position (counts). Refer to Idle Air Control Valve / Service and Repair. See: Idle Air Control (IAC) Valve/Service and Repair 8. If within specifications, the idle speed is being correctly controlled by the control module. 9. If not within specifications, refer to Driveability Symptoms. Refer to System Diagnosis for testing information. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Accelerator Pedal > Component Information > Description and Operation Accelerator Pedal: Description and Operation DESCRIPTION The accelerator pedal (3) through a cable (2) controls the throttle. There are no linkage adjustments. Replace the accelerator control cable with an identical replacement part. Check all linkages and cables in order to assure free movement with no rubbing, chafing, or binding. The accelerator pedal must operate freely, without binding, between the full closed and the Wide Open Throttle (WOT). Observe the following, when performing service on the accelerator pedal: - The mounting surface between the support and the dash panel must be free of insulation. The carpet and padding in the pedal and tunnel area must be positioned to lay flat and be free of wrinkles and bunches. - Slip the accelerator control cable through the slot in the rod (4) before installing the retainer (1) in the rod. Make sure it is seated properly. Use care in pressing the retainer into the hole, so the cable is not kinked or damaged. - The linkage must operate freely without binding between the closed throttle and the full throttle position. - Do not place the wire, hoses, cable, and other flexible components within 13 mm (0.521) of the cable or rod, at any point in their travel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Accelerator Pedal > Component Information > Description and Operation > Page 5848 Accelerator Pedal: Testing and Inspection Check for correct cable routing, or binding. Correct as necessary. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Air Cleaner Housing > Air Cleaner Fresh Air Duct/Hose > Component Information > Specifications Air Cleaner Fresh Air Duct/Hose: Specifications Air intake duct screw ........................................................................................................................... ........................................................ 2 Nm (18 lb. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Air Cleaner Housing > Air Cleaner Fresh Air Duct/Hose > Component Information > Specifications > Page 5853 Air Cleaner Fresh Air Duct/Hose: Service and Repair Air Intake Duct Retainer Bolt Air Intake Duct Removal Procedure 1. Remove the retainer. 2. Remove the screw. 3. Remove the air intake duct Installation Procedure 1. Install the air intake duct. 2. Install the screw. Tighten Tighten the screw 2 Nm (18 lb. in.). 3. Install the retainer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Customer Interest for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T - Shift/Driveability Concerns/MIL ON Air Filter Element: Customer Interest Engine, A/T - Shift/Driveability Concerns/MIL ON Bulletin No.: 04-07-30-013B Date: February 01, 2007 INFORMATION Subject: Automatic Transmission Shift, Engine Driveability Concerns or Service Engine Soon (SES) Light On as a Result of the Use of an Excessively/Over-Oiled Aftermarket, Reusable Air Filter Models: 2007 and Prior GM Cars and Light Duty Trucks 2007 and Prior Saturn Models 2003-2007 HUMMER H2 2006-2007 HUMMER H3 2005-2007 Saab 9-7X Supercede: This bulletin is being revised to add models and model years. Please discard Corporate Bulletin Number 04-07-30-013A (Section 07 - Transmission/Transaxle). The use of an excessively/over-oiled aftermarket, reusable air filter may result in: Service Engine Soon (SES) light on Transmission shift concerns, slipping and damaged clutch(es) or band(s) Engine driveability concerns, poor acceleration from a stop, limited engine RPM range The oil that is used on these air filter elements may be transferred onto the Mass Air Flow (MAF) sensor causing contamination of the sensor. As a result, the Grams per Second (GPS) signal from the MAF may be low and any or all of the concerns listed above may occur. When servicing a vehicle with any of these concerns, be sure to check for the presence of an aftermarket reusable, excessively/over-oiled air filter. The MAF, GPS reading should be compared to a like vehicle with an OEM air box and filter under the same driving conditions to verify the concern. The use of an aftermarket reusable air filter DOES NOT void the vehicle's warranty. If an aftermarket reusable air filter is used, technicians should inspect the MAF sensor element and the air induction hose for contamination of oil prior to making warranty repairs. Transmission or engine driveability concerns (related to the MAF sensor being contaminated with oil) that are the result of the use of an aftermarket reusable, excessively/over-oiled air filter are not considered to be warrantable repair items. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Customer Interest for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T - Shift/Driveability Concerns/MIL ON > Page 5862 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T - Shift/Driveability Concerns/MIL ON Air Filter Element: All Technical Service Bulletins Engine, A/T - Shift/Driveability Concerns/MIL ON Bulletin No.: 04-07-30-013B Date: February 01, 2007 INFORMATION Subject: Automatic Transmission Shift, Engine Driveability Concerns or Service Engine Soon (SES) Light On as a Result of the Use of an Excessively/Over-Oiled Aftermarket, Reusable Air Filter Models: 2007 and Prior GM Cars and Light Duty Trucks 2007 and Prior Saturn Models 2003-2007 HUMMER H2 2006-2007 HUMMER H3 2005-2007 Saab 9-7X Supercede: This bulletin is being revised to add models and model years. Please discard Corporate Bulletin Number 04-07-30-013A (Section 07 - Transmission/Transaxle). The use of an excessively/over-oiled aftermarket, reusable air filter may result in: Service Engine Soon (SES) light on Transmission shift concerns, slipping and damaged clutch(es) or band(s) Engine driveability concerns, poor acceleration from a stop, limited engine RPM range The oil that is used on these air filter elements may be transferred onto the Mass Air Flow (MAF) sensor causing contamination of the sensor. As a result, the Grams per Second (GPS) signal from the MAF may be low and any or all of the concerns listed above may occur. When servicing a vehicle with any of these concerns, be sure to check for the presence of an aftermarket reusable, excessively/over-oiled air filter. The MAF, GPS reading should be compared to a like vehicle with an OEM air box and filter under the same driving conditions to verify the concern. The use of an aftermarket reusable air filter DOES NOT void the vehicle's warranty. If an aftermarket reusable air filter is used, technicians should inspect the MAF sensor element and the air induction hose for contamination of oil prior to making warranty repairs. Transmission or engine driveability concerns (related to the MAF sensor being contaminated with oil) that are the result of the use of an aftermarket reusable, excessively/over-oiled air filter are not considered to be warrantable repair items. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Air Filter Element: > 04-07-30-013B > Feb > 07 > Engine, A/T - Shift/Driveability Concerns/MIL ON > Page 5868 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Page 5869 Air Filter Element: Testing and Inspection The air cleaner restriction indicator is located on the intake duct between the air cleaner assembly and the Mass Air Flow (MAF) sensor. If the area inside of the clear section is green, no air filter service is required. If the area inside the clear section is orange and Change Air Filter appears, replace the air filter. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Air Cleaner Housing > Air Filter Element > Component Information > Technical Service Bulletins > Page 5870 Air Filter Element: Service and Repair Air Cleaner Element Holddown REMOVAL PROCEDURE 1. Disconnect the hold down clips. 2. Remove the air cleaner cover. 3. Remove the filter. Hold the duct and remove the filter by pulling and twisting the filter away from the duct. 4. Clean the air cleaner housing. INSTALLATION PROCEDURE 1. Install the filter. - Install the new filter by pushing it all the way to the stops of the duct. - Install the duct and filter in the air cleaner housing. Make sure that the duct fits properly into the housing. 2. Install the air cleaner cover. 3. Connect the hold down clips. 4. Push the button on the top of the indicator to reset it to the green (Clean) filter zone. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions Mass Air Flow (MAF) Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5875 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5876 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5877 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5878 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5879 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5880 Mass Air Flow (MAF) Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5881 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5882 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5883 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5884 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5885 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5886 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5887 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5888 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5889 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5890 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5891 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5892 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5893 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5894 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5895 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5896 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5897 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5898 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5899 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5900 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5901 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5902 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5903 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5904 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5905 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5906 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 5907 Mass Air Flow System Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Page 5908 Mass Air Flow (MAF) Sensor: Description and Operation Mass Air Flow (MAF) Sensor The Mass Air Flow (MAF) sensor measures the amount of air which passes through it. The VCM uses this information to determine the operating condition of the engine, to control fuel delivery. A large quantity of air indicates acceleration. A small quantity of air indicates deceleration or idle. The scan tool reads the MAF value and displays it in grams per second (gm/Sec). At idle, it should read between 5-7 gm/Sec on a fully warmed up engine. Values should change rather quickly on acceleration, but values should remain fairly stable at any given RPM. When the VCM detects a malfunction in the MAF sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0101 system performance. ^ DTC P0102 frequency low. ^ DTC P0103 frequency high. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Page 5909 Mass Air Flow (MAF) Sensor: Service and Repair MAF Sensor MAF Sensor Intake Duct REMOVAL PROCEDURE CAUTION: Take care when handling the Mass Air Flow (MAF). Do Not dent, puncture, or otherwise damage the honeywell located at the air inlet end of the MAF. Do Not touch the sensing elements or allow anything (including solvents and lubricants) to come in contact with them. A small amount of GM lubricant (P/N 99855406) may be used on the air duct only to aid in installation. Do Not drop or roughly handle the MAF. 1. Disconnect the 3 wire electrical connector. 2. Loosen the clamp on the intake duct. 3. Carefully remove the MAF sensor. INSTALLATION PROCEDURE 1. Install the MAF sensor. 2. Install the intake ducts. 3. Tighten the clamp. 4. Connect the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Diagnostic Connector - Fuel Pump > Component Information > Locations Diagnostic Connector - Fuel Pump: Locations For Fuel Pump Prime and Run Connector, See Computer and Control Systems, Data Link Connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fillpipe Restrictor > Component Information > Description and Operation Fillpipe Restrictor: Description and Operation DESCRIPTION To prevent refueling with leaded fuel, the fuel filler neck is equipped with restrictor and deflector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel > Component Information > Technical Service Bulletins > Fuel System - TOP TIER Detergent Gasoline (Canada) Fuel: Technical Service Bulletins Fuel System - TOP TIER Detergent Gasoline (Canada) INFORMATION Bulletin No.: 05-06-04-022G Date: October 27, 2010 Subject: TOP TIER Detergent Gasoline Information and Available Brands (Deposits, Fuel Economy, No Start, Power, Performance, Stall Concerns) - Canada ONLY Models: 2011 and Prior GM Passenger Cars and Trucks (Canada Only) Supercede: This bulletin is being revised to update the model years and include an additional gasoline brand as a TOP TIER source. Please discard Corporate Bulletin Number 05-06-04-022F (Section 06 - Engine/Propulsion System). In the U.S., refer to the latest version of Corporate Bulletin Number 04-06-04-047I. A new class of fuel called TOP TIER Detergent Gasoline is appearing at retail stations of some fuel marketers. This gasoline meets detergency standards developed by six automotive companies. All vehicles will benefit from using TOP TIER Detergent Gasoline over gasoline containing the "Lowest Additive Concentration" recommended by the Canadian General Standards Board (CGSB). Those vehicles that have experienced deposit related concerns may especially benefit from use of TOP TIER Detergent Gasoline. Intake valve: 16,093 km (10,000 mi) with TOP TIER Detergent Gasoline Intake valve: 16,093 km (10,000 mi) with Minimum Additive recommended by the CGSB Top Tier Fuel Availability Chevron was the first to offer TOP TIER Detergent Gasoline in Canada. Shell became the first national gasoline retailer to offer TOP TIER Detergent Gasoline across Canada. Petro-Canada began offering TOP TIER Detergent Gasoline nationally as of October 1, 2006. Sunoco began offering TOP TIER Detergent Gasoline in March of 2007. Esso began offering TOP TIER Detergent Gasoline in May of 2010. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel > Component Information > Technical Service Bulletins > Fuel System - TOP TIER Detergent Gasoline (Canada) > Page 5920 Gasoline Brands That Currently Meet TOP TIER Detergent Gasoline Standards The following gasoline brands meet the TOP TIER Detergent Gasoline Standards in all octane grades : Chevron Canada (markets in British Columbia and western Alberta) - Shell Canada (nationally) - Petro-Canada (nationally) - Sunoco-Canada (Ontario) - Esso-Canada (nationally) What is TOP TIER Detergent Gasoline? TOP TIER Detergent Gasoline is a new class of gasoline with enhanced detergency and no metallic additives. It meets new, voluntary deposit control standards developed by six automotive companies that exceed the detergent recommendations of Canadian standards and does not contain metallic additives, which can damage vehicle emission control components. Where Can TOP TIER Detergent Gasoline Be Purchased? The TOP TIER program began in the U.S. and Canada on May 3, 2004. Some fuel marketers have already joined and introduced TOP TIER Detergent Gasoline. This is a voluntary program and not all fuel marketers will offer this product. Once fuel marketers make public announcements, they will appear on a list of brands that meet the TOP TIER standards. Who developed TOP TIER Detergent Gasoline standards? TOP TIER Detergent Gasoline standards were developed by six automotive companies: BMW, General Motors, Honda, Toyota, Volkswagen and Audi. Why was TOP TIER Detergent Gasoline developed? TOP TIER Detergent Gasoline was developed to increase the level of detergent additive in gasoline. In the U.S., government regulations require that all gasoline sold in the U.S. contain a detergent additive. However, the requirement is minimal and in many cases, is not sufficient to keep engines clean. In Canada, gasoline standards recommend adherence to U.S. detergency requirements but do not require it. In fact, many brands of gasoline in Canada do not contain any detergent additive. In order to meet TOP TIER Detergent Gasoline standards, a higher level of detergent is needed than what is required or recommended, and no metallic additives are allowed. Also, TOP TIER was developed to give fuel marketers the opportunity to differentiate their product. Why did the six automotive companies join together to develop TOP TIER? All six corporations recognized the benefits to both the vehicle and the consumer. Also, joining together emphasized that low detergency and the intentional addition of metallic additives is an issue of concern to several automotive companies. What are the benefits of TOP TIER Detergent Gasoline? TOP TIER Detergent Gasoline will help keep engines cleaner than gasoline containing the "Lowest Additive Concentration" recommended by Canadian standards. Clean engines help provide optimal fuel economy and engine performance, and also provide reduced emissions. Also, the use of TOP TIER Detergent Gasoline will help reduce deposit related concerns. Who should use TOP TIER Detergent Gasoline? All vehicles will benefit from using TOP TIER Detergent Gasoline over gasoline containing the "Lowest Additive Concentration" recommended by Canadian standards. Those vehicles that have experienced deposit related concerns may especially benefit from use of TOP TIER Detergent Gasoline. More information on TOP TIER Detergent Gasoline can be found at this website, http://www.toptiergas.com/. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel > Component Information > Technical Service Bulletins > Fuel System - TOP TIER Detergent Gasoline (Canada) > Page 5921 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel > Component Information > Technical Service Bulletins > Fuel System - TOP TIER Detergent Gasoline (Canada) > Page 5922 Fuel: Technical Service Bulletins Fuel System - 'TOP TIER' Detergent Gasoline Information INFORMATION Bulletin No.: 04-06-04-047I Date: August 17, 2009 Subject: TOP TIER Detergent Gasoline (Deposits, Fuel Economy, No Start, Power, Performance, Stall Concerns) - U.S. Only Models: 2010 and Prior GM Passenger Cars and Trucks (including Saturn) (U.S. Only) 2003-2010 HUMMER H2 (U.S. Only) 2006-2010 HUMMER H3 (U.S. Only) 2005-2009 Saab 9-7X (U.S. Only) Supercede: This bulletin is being revised to add model years and additional sources to the Top Tier Fuel Retailers list. Please discard Corporate Bulletin Number 04-06-04-047H (Section 06 Engine/Propulsion System). In Canada, refer to Corporate Bulletin Number 05-06-04-022F. A new class of fuel called TOP TIER Detergent Gasoline is appearing at retail stations of some fuel marketers. This gasoline meets detergency standards developed by six automotive companies. All vehicles will benefit from using TOP TIER Detergent Gasoline over gasoline containing the "Lowest Additive Concentration" set by the EPA. Those vehicles that have experienced deposit related concerns may especially benefit from the use of TOP TIER Detergent Gasoline. Intake valve: - 10,000 miles with TOP TIER Detergent Gasoline Intake valve: - 10,000 miles with Legal Minimum additive Gasoline Brands That Currently Meet TOP TIER Detergent Gasoline Standards As of August 1, 2009, all grades of the following gasoline brands meet the TOP TIER Detergent Gasoline Standards: - Chevron - Chevron-Canada - QuikTrip - Conoco Phillips 66 - 76 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel > Component Information > Technical Service Bulletins > Fuel System - TOP TIER Detergent Gasoline (Canada) > Page 5923 - Shell - Shell-Canada - Entec Stations located in the greater Montgomery, Alabama area. - MFA Oil Company located throughout Missouri. - Kwik Trip, Inc. in Minnesota and Wisconsin and Kwik Star convenience stores in Iowa. The Somerset Refinery, Inc. at Somerset Oil stations in Kentucky. Aloha Petroleum - Tri-Par Oil Company - Turkey Hill Minit Markets - Texaco - Petro-Canada - Sunoco-Canada - Road Ranger located in Illinois, Indiana, Iowa, Kentucky, Missouri, Ohio and Wisconsin What is TOP TIER Detergent Gasoline? TOP TIER Detergent Gasoline is a new class of gasoline with enhanced detergency. It meets new, voluntary deposit control standards developed by six automotive companies that exceed the detergent requirements imposed by the EPA. Where Can TOP TIER Detergent Gasoline Be Purchased? The TOP TIER program began on May 3, 2004 and many fuel marketers have joined the program and have introduced TOP TIER Detergent Gasoline. This is a voluntary program and not all fuel marketers will offer this product. Once fuel marketers make public announcements, they will appear on a list of brands that meet the TOP TIER standards. Where Can I find the Latest Information on TOP TIER Fuel and Retailers? On the web, please visit www.toptiergas.com for additional information and updated retailer lists. Who developed TOP TIER Detergent Gasoline standards? TOP TIER Detergent Gasoline standards were developed by six automotive companies: Audi, BMW, General Motors, Honda, Toyota and Volkswagen. Why was TOP TIER Detergent Gasoline developed? TOP TIER Detergent Gasoline was developed to increase the level of detergent additive in gasoline. The EPA requires that all gasoline sold in the U.S. contain a detergent additive. However, the requirement is minimal and in many cases, is not sufficient to keep engines clean. In order to meet TOP TIER Detergent Gasoline standards, a higher level of detergent is needed than what is required by the EPA. Also, TOP TIER was developed to give fuel marketers the opportunity to differentiate their product. Why did the six automotive companies join together to develop TOP TIER? All six corporations recognized the benefits to both the vehicle and the consumer. Also, joining together emphasized that low detergency is an issue of concern to several automotive companies. What are the benefits of TOP TIER Detergent Gasoline? TOP TIER Detergent Gasoline will help keep engines cleaner than gasoline containing the "Lowest Additive Concentration" set by the EPA. Clean engines help provide optimal fuel economy and performance and reduced emissions. Also, use of TOP TIER Detergent Gasoline will help reduce deposit related concerns. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel > Component Information > Technical Service Bulletins > Fuel System - TOP TIER Detergent Gasoline (Canada) > Page 5924 Fuel: Technical Service Bulletins Fuel - Top Tier Detergent Gasoline Information Bulletin No.: 04-06-00-047 Date: June 24, 2004 ADVANCED SERVICE INFORMATION Subject: Top Tier Detergent Gasoline (Deposits, Fuel Economy, No Start, Power, Performance, Stall Concerns) Models: 2005 and Prior All General Motors Passenger Cars and Trucks (U.S. Only) A new class of gasoline, called Top Tier Detergent Gasoline, will be appearing at retail stations of some fuel marketers. This gasoline meets detergency standards developed by four automotive companies. A description of the concept and benefits of Top Tier is provided in the following question and answer section. What is Top Tier Detergent Gasoline? Top Tier Detergent Gasoline is a new class of gasoline with enhanced detergency. It meets new, voluntary deposit control standards developed by four automotive companies that exceed the detergent requirements imposed by the EPA. Who developed Top Tier Detergent Gasoline standards? Top Tier Detergent Gasoline standards were developed by four automotive companies: BMW, General Motors, Honda and Toyota. Why was Top Tier Detergent Gasoline developed? Top Tier Detergent Gasoline was developed to increase the level of detergent additive in gasoline. The EPA requires that all gasoline sold in the U.S. contain a detergent additive. However, the requirement is minimal and in many cases, is not sufficient to keep engines clean. In order to meet Top Tier Detergent Gasoline standards, a higher level of detergent is needed than what is required by the EPA. Also, Top Tier was developed to give fuel marketers the opportunity to differentiate their product. Why did the four automotive companies join together to develop Top Tier? All four corporations recognized the benefits to both the vehicle and the consumer. Also, joining together emphasized that low detergency is an issue of concern to several automotive companies. What are the benefits of Top Tier Detergent Gasoline? Top Tier Detergent Gasoline will help keep engines cleaner than gasoline containing the "Lowest Additive Concentration" set by the EPA. Clean engines help provide optimal fuel economy and performance and reduced emissions. Also, use of Top Tier Detergent Gasoline will help reduce deposit related concerns. Who should use Top Tier Detergent Gasoline? All vehicles will benefit from using Top Tier Detergent Gasoline over gasoline containing the "Lowest Additive Concentration" set by the EPA. Those vehicles that have experienced deposit related concerns may especially benefit from use of Top Tier Detergent Gasoline. Where can Top Tier Detergent Gasoline be purchased? The Top Tier program began on May 3, 2004. Some fuel marketers have already joined and are making plans to introduce Top Tier Detergent Gasoline. This is a voluntary program and not all fuel marketers will offer this product. Once fuel marketers make public announcements, a list of all fuel marketers meeting Top Tier standards will be made available. For now, look for the "Top Tier" designation at the gas pump. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel > Component Information > Technical Service Bulletins > Fuel System - TOP TIER Detergent Gasoline (Canada) > Page 5925 Fuel: Technical Service Bulletins Warranty - Fuel Fill Allowance Changes File In Section: Warranty Administration Bulletin No: 52-05-11 Date: September, 1995 WARRANTY ADMINISTRATION Subject: 1996 Fuel Fill Allowance Changes Models: 1996 Chevrolet/Geo Passenger Cars and Trucks Attention: Dealer Service Manager and Warranty Administrator For the beginning of the 1996 model year, the General Motors fuel fill reimbursement rate for self-serve fuel is listed below. Please refer to the chart included with this bulletin for individual passenger car and truck fuel prices. Regular, Unleaded Gasoline $1.10 per gallon Premium, Unleaded Gasoline $1.30 per gallon Diesel Fuel $1.20 per gallon Dealer fuel fill credit is triggered by the retail delivery report. All passenger cars and light-duty trucks delivered retail are eligible for this credit, except chassis cab, G-Cutaway, high cube P-models. Also, any unit showing a "retail amenities delete" notation on the invoice. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel > Component Information > Technical Service Bulletins > Fuel System - TOP TIER Detergent Gasoline (Canada) > Page 5926 The chart shows the AVERAGE AMOUNT OF FUEL ADDED BY DEALER, PER UNIT FUEL PRICE, and the PROPOSED DEALER CREDIT a dealer should receive for each 1996 vehicle sold retail. Non-eligible models are shown with $0.00 amount in the PROPOSED DEALER CREDIT column. Eligible past model units delivered from inventory will receive credit based on their proper fuel capacity multiplied by the fuel price in effect at the time of delivery. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel > Component Information > Technical Service Bulletins > Fuel System - TOP TIER Detergent Gasoline (Canada) > Page 5927 Fuel: Technical Service Bulletins Warranty - Fuel Expense and Fuel Price Change File In Section: Warranty Administration Bulletin No: 52-05-10 Date: September, 1995 WARRANTY ADMINISTRATION Subject: 1996 G.S.A. Fuel Expense / Fuel Price Change Models: 1996 Chevrolet / Geo Passenger Cars and Light Duty Trucks Attention: Dealer Service Manager/Warranty Administrator The purpose of this bulletin is to advise retail/wholesale personnel of the fuel expense allowed for G.S.A. units. Please refer to the chart listing individual passenger car and light truck "DEALER CREDIT." Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel > Component Information > Specifications > Fuel Specifications/Alcohol In Fuel Fuel: Specifications Fuel Specifications/Alcohol In Fuel GASOLINE All engines are designed to use unleaded fuel only. Unleaded fuel must be used for proper emission control system operation. It's use will also minimize spark plug fouling and extend engine oil life. Using leaded fuel can damage the emission control system and could result in loss of emission warranty coverage. The fuel should meet specification ASTM D4814 for the U.s. or CGSB 3.5-M87 for Canada. This engine is designed to use unleaded fuel with a minimum U(R+M) / 2e (pump) octane number of 87, where; R=research octane number, and M=motor octane number. METHYL TERTIARY-BUTYL ETHER (MTBE) Methyl tertiary-butyl ether (MTBE) fuel may be used, providing there is no more than 15% (MTBE) by volume. ETHANOL Ethanol (ethyl) or grain alcohol fuel may be used, providing that there is no more than 10% ethanol alcohol by volume. METHANOL Methanol (methyl) or wood alcohol fuels may be used, providing there is no more than 5% of methanol by volume. NOTICE: Do not use fuel that contains more than 5% methanol. Use of a fuel (gasohol) that contains more than 5% of methanol can corrode metal fuel system components and damage plastic and rubber parts. - Do not spill fuel containing alcohol on the vehicle. Alcohol can cause damage to the paint finish and trim. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel > Component Information > Specifications > Fuel Specifications/Alcohol In Fuel > Page 5930 Fuel: Specifications Fuel (Alcohol and Gasoline) Types General Motors customers will be potentially exposed to a variety of different fuel types. Besides the conventional gasoline available, new types such as Reformulated Gasoline (RFG), oxygenated gasoline, and starting in 1996, California Phase 2 RFG. Reformulated Gasoline (RFG) is blended to burn more cleanly and not to evaporate as readily. RFG must contain a minimum of 2 percent oxygen, which is usually achieved with ethanol or EPA-approved ethers such as methyl tertiary-butyl ether (MTBE). This type of fuel is required by the Clean Air Act in the nine worst ozone non-attainment areas of the country, and may also be required in other areas designated ozone non-attainment, at the option of the states. RFG is intended to produce approximately 15 percent less pollution than conventional gasoline. Using RFG should reduce the total health risk to the public by reducing exposure to ozone and air toxins. General Motors supports the use of RFG as a cost effective means of providing air quality benefits. Oxygenated gasolines are prevalent in the wintertime for Carbon Monoxide (CO) non-attainment areas. These fuels contain oxygen components similar to RFG. Approximately 50 percent of the fuel sold in the U.s. in the wintertime contains an oxygenate component. Vehicle fuel economy may be slightly reduced, if at all, by the use of gasoline containing oxygenates. Fuel economy is most affected by engine and vehicle type, driving habits, weather conditions, and vehicle maintenance. Properly blended RFG, oxygenated gasoline, and California Phase 2 RFG will have no adverse effect on vehicle performance or to the durability of engine and fuel system components. In fact, the General Motors Owner's Manual fuel statements have consistently permitted the use of properly blended fuels containing up to 10 percent ethanol (since 1980) and up to 15 percent methyl tertiary-butyl ether (MTBE) for current and all past model year vehicles. These statements continue to be valid. The use of oxygenate-containing fuels will not invalidate the GM vehicle warranty. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel > Component Information > Specifications > Page 5931 Fuel: Testing and Inspection PROCEDURE Alcohol concentrations greater than 10% in fuel can be detrimental to fuel system components and may cause driveability problems such as hesitation, lack of power, stall, no start, etc. The problems may be due to fuel system corrosion and subsequent fuel filter plugging, deterioration of rubber components, and/or air4tiel mixture leaning. Various types and concentrations of alcohol are used in commercial fuel. Some alcohol is more detrimental to fuel system components than others. If an excessive amount of alcohol in the fuel is suspected as the cause of a driveability condition, the following procedure may be used to detect the presence of alcohol in the fuel. TESTING PROCEDURE The fuel sample should be drawn from the bottom of the tank so that any water present in the tank will be detected. The sample should be bright and clear. If the sample appears cloudy, or contaminated with water (as indicated by a water layer at the bottom of the sample), this procedure should not be used, and the fuel system should be cleaned. 1. Using a 100 ml specified cylinder with 1 ml graduation marks, fill the cylinder with fuel to the 90 ml mark. 2. Add 10 ml of water in order to bring the total fluid volume to 100 ml and install a stopper. 3. Shake the cylinder vigorously for 10 to 15 seconds. 4. Carefully loosen the stopper in order to release the pressure. 5. Re-install the stopper and shake the cylinder vigorously again for 10 to 15 seconds. 6. Put the cylinder on a level surface for approximately 5 minutes in order to allow adequate liquid separation. If alcohol is present in the fuel, the volume of the lower layer (which would now contain both alcohol and water) will be greater than 10 ml. For example, if the volume of the lower layer is increased to 15 ml, this indicates at least 5 percent alcohol in the fuel. The actual amount of alcohol may be somewhat greater because this procedure does not extract all of the alcohol from the fuel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Filler Cap > Component Information > Description and Operation Fuel Filler Cap: Description and Operation The fuel tank filler neck is equipped with a screw type cap. The threaded part of the cap requires several turns counter-clockwise to remove. The long threaded area is designed to allow any remaining fuel tank pressure to escape during the cap removal operation. A built-in rachet type torque limiting device prevents over-tightening. To install, turn the cap clockwise until a clicking noise is heard. This signals that the correct torque has been reached and the cap is fully seated. NOTICE: If a fuel filler cap requires replacement, only a cap with the same features should be used. Failure to use the correct cap can result in a serious malfunction of the system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Filler Cap > Component Information > Description and Operation > Page 5935 Fuel Filler Cap: Service and Repair If a fuel tank filler cap requires replacement, use only a cap with the same features. Failure to use the correct cap can result in a malfunctioning of the evaporative system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Filter > Fuel Pressure Release > System Information > Service and Repair Fuel Pressure Release: Service and Repair TOOLS REQUIRED - J 34730 Fuel Pressure Gauge WARNING: Relieve the fuel system pressure before servicing fuel system components In order to reduce the risk of fire and personal Injury. After relieving the system pressure, a small amount of fuel may be released when servicing the fuel lines or connections. In order to reduce the chance of personal Injury, cover the regulator and the fuel line fittings with a shop towel before disconnecting. This will catch any fuel that may leak out. Place the towel In an approved container when the disconnection Is complete. 1. Disconnect the negative battery cable in order to avoid possible fuel discharge if an accidental attempt is made to start the engine. 2. Loosen the fuel filler cap in order to relieve the tank vapor pressure. 3. Connect the gauge J 34730-1A or the equivalent to the fuel pressure connection. 4. Wrap a shop towel around the fitting while connecting the gauge in order to avoid spillage. 5. Install the bleed hose into an approved container and open valve in order to bleed the system pressure. The fuel connections are now safe for servicing. 6. Drain any fuel remaining in gauge into an approved container. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Recalls: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed Fuel Injector: Recalls Campaign - Fuel Injector Sticking Closed File In Section: 06-Engine Emissions Bulletin No.: 99066F Date: March, 2003 SPECIAL POLICY SUBJECT: 99066F - SPECIAL POLICY ADJUSTMENT - SEQUENTIAL CENTRAL PORT FUEL INJECTION (SCPI) FAILURES IN CALIFORNIA ONLY (YF5 EMISSION EQUIPPED) MODELS: CERTAIN 1996, 1997, 1998, 1999, 2000, 2001, 2002 S/T, M/L, C/K, G, P, W4/NPR TRUCKS AND 2003 NPR TRUCKS EQUIPPED WITH 4.3L (RPO L35 - VIN CODE W OR RPO LF6 - VIN CODE X), 5.0L (RPO L30 - VIN CODE M) OR 5.7L (RPO L31 - VIN CODE R) ENGINE AND CALIFORNIA EMISSION EQUIPPED (RPO YF5) This bulletin is being revised to add the 2002 and 2003 model years to the SCPI Special Policy on certain S/T, M/L, C/K, G, P and W4/NPR truck models. Please discard Special Policy Bulletin Number 99066E, dated February, 2003. CONDITION Some customers of 1996, 1997, 1998, 1999, 2000, 2001, 2002 model year S/T, M/L, C/K, G, P, W4/NPR trucks and 2003 NPR trucks, that are registered in California, equipped with 4.3L (RPO L35 and VIN Code W, or RPO LF6 and VIN Code X), 5.0L (RPO L30 and VIN Code M) or 5.7L (RPO L31 and VIN Code R) engine, and California emissions (RPO YF5), may experience a "Service Engine Soon" light, misfire, rough idle or hard start due to a deposit build-up on the Sequential Central Port Fuel Injector (SCPI) poppet valve(s). The deposit build-up may cause injector poppets to stick closed. Certain fuels have been found to interact with the SCPI system to cause the deposits. SPECIAL POLICY ADJUSTMENT This special policy covers the SCPI failure condition described above for a period of ten (10) years or 200,000 miles, whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership. The repairs will be made at no charge to the owner. This special policy applies ONLY to repairs requiring SCPI system servicing, injector cleaning and/or MFI assembly replacement of the SCPI system. The customer should not be charged for performing a system check when it is determined that the SCPI system is not the cause of a customer complaint (labor operation T5532 is provided to submit claims for such system checks). Any additional necessary diagnosis and repairs that are not related to the SCPI condition are not covered by this special policy. The customer should be informed that any further service that is not covered by new vehicle warranty will not be covered by this policy. VEHICLES INVOLVED Involved are certain 1996,1997,1998,1999, 2000, 2001, 2002 S/T, M/L, C/K, G, P, W4/NPR and 2003 NPR model vehicles, registered in California, equipped with 4.3L (RPO L35 - VIN Code W, or RPO LF6 - VIN Code X), 5.0L (RPO L30 - VIN Code M) or 5.7L (RPO L31 - VIN Code R) engine; and California emissions (RPO YF5). This Special Policy covers all vehicles within these model years, with these engine and emissions RPO's. PARTS INFORMATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Recalls: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed > Page 5948 Parts required to complete this special policy are to be obtained from General Motors Service Parts Operations (GMSPO). Please refer to your "involved vehicles listing" prior to ordering parts. Normal orders should be placed on a DRO Daily Replenishment Order. In an emergency, parts should be ordered on a CSO = Customer Special Order. IMPORTANT: Isuzu Parts Ordering: In order to comply with the 10-digit Isuzu part numbering system, Isuzu dealers must add an "8" to the beginning and a "0" to the end of the listed 8-digit part numbers when ordering parts through AIPDN. CUSTOMER NOTIFICATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Recalls: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed > Page 5949 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Recalls: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed > Page 5950 Customers will be notified of this special policy on their vehicles by General Motors (see copy of typical customer letter included with this bulletin - actual divisional letter may vary slightly). SERVICE PROCEDURE System Check: Use strategy-based diagnoses listed in the front of the Driveability and Emissions section of the service manual. If the SCPI system is operating properly, inform the customer that the vehicle does not have the condition listed in the owner letter. If poor driveability conditions persist, inform the customer that any further diagnosis and repairs will be at their expense if the vehicle is outside the parameters of the new vehicle warranty. SCPI Injector Cleaning Procedure: If diagnosis leads to sticking poppet nozzles, use the service procedure from Service Bulletin 00-06-04-003B to clean the SCPI poppet nozzles. Please note that the service bulletin term for SCPI is Central Sequential Fuel Injection (CSFI), but is referring to the same fuel system assembly. If the poppet nozzles have previously been cleaned and the sticking condition has reoccurred, refer to the correction paragraph below. SCPI Fuel Tank Fill Pipe Assembly for 1997-99 M/L Van and 1999 - some 2000 C/K Truck: with 4.3L, 5.0L, 5.7L engines and built prior to listed VIN/Production dates on Service Bulletin 00-06-04-018: If diagnosis leads to sticking poppet nozzles on these models, use the service procedure from Service Bulletin 00-06-04-018 to replace the fuel tank fill pipe assembly, if this procedure has not been performed previously. Previous service procedure can be verified by checking GMVIS for Labor Operation L1065 on "M/L" trucks with replacement part number 15050573; or Labor Operation L1065 on "C/K" trucks with replacement part numbers 15747585 or 15747588. Correction: If, after cleaning the SCPI poppet nozzles, the normal service manual diagnosis still indicates that the SCPI is the cause of the customer complaint, or if the injectors have previously been cleaned and the vehicle has again experienced sticking poppet nozzles, refer to Service Bulletin 00-06-04-003B and replace the SCPI fuel assembly with the MFI fuel assembly. Please note that the service bulletin term for SCPI is Central Sequential Fuel Injection (CSFI), but is referring to the same fuel system assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Recalls: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed > Page 5951 CLAIM INFORMATION For vehicles repaired under this special policy, submit a claim with the information indicated. CUSTOMER REIMBURSEMENT Customer requests for reimbursement are for any previously paid repairs to, or replacement of, the Sequential Central Port Fuel Injection (SCPI) system. Repairs must have occurred within 10 years of the date the vehicle was originally placed in service, or 200,000 miles, whichever occurs first. The requests are to be submitted within two (2) years of the date on which the repair was paid or within two (2) years of the date of this Special Policy Bulletin, whichever is greater. When a customer requests reimbursement, they must provide the following: - Proof of ownership at time of repair. - Original paid receipt confirming the amount of unreimbursed repair expense(s) (including Service Contract deductibles), a description of the repair, and the person or entity performing the repair. Customers from the State of California, must submit requests for reimbursement directly to (Divisions) per instructions in the owner letter. If the work was done by someone other than a GM dealership, the amount of reimbursement will be limited to the amount that the repair would have cost GM to have it completed by a GM dealership. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up Technical Service Bulletin # 00-06-04-003B Date: 030201 Fuel System - MIL ON/Rough Idle on Start-Up File In Section: 06 - Engine/Propulsion System Bulletin No.: 00-06-04-003B Date: February, 2003 TECHNICAL Subject: Rough Idle After Start, And/Or A Service Engine Soon (SES) Light (Unstick And Clean Central Sequential Fuel Injection (CSFI) Poppet Valves or Convert to MFI) Models: 1995-2002 Chevrolet and GMC S/T Models 1996-2002 Chevrolet and GMC C/K, M/L, G, P Models 1996-2001 Oldsmobile Bravada 1999-2000 Cadillac Escalade with 4.3L, 5.0L or 5.7L Engine (VINS W, X, M, R - RPOs L35, LF6, L30, L31) Except 2002 VIN X - RPO LU3 Models This bulletin is being revised to update the Warranty Information. Please discard previous copies of Corporate Bulletin Number 00-06-04-003B with warranty chart (Section 06 - Engine). This copy is for Dealers in the state of CALIFORNIA ONLY. Condition Some customers may comment on rough idle after start-up, especially if the vehicle has sat overnight. These symptoms may be intermittent. The Service Engine Soon (SES) light may also be illuminated. Current misfire or history misfire codes may be detected with the Tech 2 scan tool. Cause A deposit build-up on the CSFI poppet valve ball and/or seat may cause the poppet ball to stick open or closed. In either case, the specific cylinder will be mis-fueled, resulting in a cylinder mis-fire condition. Correction A new injector unsticking and cleaning process has proven to be effective in restoring poppet valves to an "as new" condition. CSFI injector replacement should NOT be considered as a correction for this customer concern. Check the vehicle history to determine if the vehicle is returning for a second fuel system repair for this condition. If the fuel system has been repaired for this condition previously, then inform the customer that an alternate fix is available. A new MFI fuel system has been developed that will back service the CSFI fuel system. The MFI fuel system eliminates the CSFI poppet valve ball and seat. The CSFI fuel system will need to be replaced as a unit. Refer to Central SFI to MFI Conversion instructions in this bulletin. Notice: Individual CSFI injectors can not be replaced with MFI injectors. The entire CSFI fuel meter body will need to be replaced. The bracket used to retain the injectors in the fuel meter body is different between the CSFI and MFI unit. The unit may not seal if you mix injectors. Severe engine damage could result. Cleaning the CSFI injectors is the preferred repair. The CSFI unit should not be replaced until cleaning has been attempted. If the vehicle should return for the same repair, then the CSFI unit can be replaced with an MFI unit. If the vehicle is out of warranty, the customer should be given the option of which fix to pursue. Important: "GM of Canada" dealers require District Service Manager approval prior to replacing the CSFI unit with a MFI unit under warranty. The first step of this process is to use the J 41413 Evap Pressure/Purge Station, in conjunction with the J 44466-10 pressure regulator/hose assembly, to provide the required high pressure (150 psi) source to perform the unsticking procedure. The J 39021 fuel injector tester and accessories provide the means to "energize" the injector. Some later model-year vehicles may utilize the Tech 2(R) to "energize" the injectors. The second step of this process is to run the engine on a solution of 10% Top Engine Cleaner and 90% gasoline. This will effectively clean any deposits from the ball and seats of the poppets. It is very important that the engine fuel system is separated from the vehicle fuel system. Top Engine Cleaner may have detrimental effects on the fuel pump. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5957 Parts Information Cleaning Procedure Parts CSFI to MFI Conversion Parts Parts are currently available from GMSPO. Warranty Information Important: Some California vehicles may be covered by Special Policy 99066E if built with California Emissions RPO YF5. If the vehicle is covered by the special policy, then that warranty information should be used. For vehicles repaired under warranty, use information contained in Special Policy 99066E. Information This procedure should be performed before any attempt to convert the fuel system to MFI. S/T and C/K Truck 1. Loosen the fuel filler cap to relieve vapor pressure in the fuel tank. 2. Remove the Positive Crankcase Ventilation (PCV) clean air tube from the air inlet tube and set aside. 3. Remove the bonnet and inlet tube from the throttle body. 4. Remove the brake booster vacuum hose and connector from the intake manifold. 5. Remove the electrical connector from the CSFI fuel metering body. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5958 6. Remove ignition wires 1, 3, 5, and 7 from the distributor cap. 7. Remove the fuel line bolt (4) at the rear of the intake manifold. 8. Relieve the fuel system pressure at the service fitting on the fuel line. Use a shop towel to contain any fuel that may exit the service fitting. 9. Remove the nuts (1) and clamp (2) from the fuel pipe. 10. Remove the fuel pipes from the metering body. Be careful not to disturb the O-rings, washer, and spacer in the metering body. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5959 11. Install the J 44466-12 (2) and the J 44466-13 (1) to the metering body and tighten. Make sure that the fuel pipe 0-rings, washer, and spacers are present and in their proper position. 12. Install the J 44466-11 (4), clamp (2), and J 44466-13 (1) to the fuel pipe and tighten. 13. Obtain the J 41413, close the valve (2) on the tank, and remove the regulator assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5960 14. Install the J 44466-10 (5) to the J 41413 tank (3). The J 44466-10 regulator is preset to 150 psi. 15. Connect the J 44466-10 hose (1) to the J 44466-12 (3). 16. Install the J 39021 Injector/Coil Balance Tester, the J 39021-210 Injector Tester Adapter Box, and J 39021-301 V6 Fuel Injector Test Adapter (1) or J 39021-302 V8 Fuel Injector Test Adapter to the metering body electrical connector. 17. Adjust the amperage selector switch on J 39021 to 0.5 amps. 18. Open the valve (2) on the tank (3). 19. Open the valve (4) on the J 44466-10 to pressurize the fuel system. The minimum pressure required on the gauge (6) is 150 psi. If 150 psi is not obtained, the tank (3) must be refilled prior to performing this procedure. 20. Close the valve (4) on the J 44466-10. 21. Energize one injector using the J 39021. Observe a pressure drop on the gauge (6) and verity the injector/poppet valve operation. An injector/poppet that is "stuck" and not operational will have no pressure drop on the gauge. It an injector remains "stuck", repeat the procedure multiple times (as required) until the injector is operational. 22. Repeat Steps 19, 20 and 21 for each individual injector to verify that all injector/poppet valve assemblies are "unstuck" and functional. 23. Shut off pressure valve (2) on the tank (3) of the J 41413. 24. Bleed off the pressure at the J 44466-10. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5961 25. Disconnect and remove the J 44466-10 (5) from the J 44466-12, and the J 41413. 26. Remove the J 39021-301 or J 39021-302, J 39021-210, and J 39021 from the metering body. 27. Install the vehicle electrical connector to the metering body. 28. Install the brake booster vacuum hose and connector to the intake manifold. 29. Install ignition wires 1, 3, 5, and 7 to the distributor cap. 30. Install the air inlet bonnet 10 the throttle body, tighten the wing-nut. 31. Install the PCV fresh air tube to the air inlet tube. 32. Obtain J 35800-A (2). Make sure the valve at the bottom of the canister (3) is closed. 33. Remove the canister top and add 24 ml (0.8 fl. oz.) Top Engine Cleaner, P/N 1050002 (Canada P/N 992872), to the canister. 34. Fill the remainder of the canister with regular unleaded gasoline and install the canister top. 35. Suspend J 35800-A from a convenient underhood location. 36. Connect the hose from J 35800-A to the service port on the J 44466-12 37. Open the valve (3) at the bottom of J 35800-A. 38. Connect a "shop air" source to the fitting at the top of J 35800-A and adjust the regulator (1) to 75 psi. 39. Start the vehicle. It may be necessary to re-adjust the J 35800-A pressure regulator to maintain 75 psi. 40. Let the vehicle run at idle until the canister is empty and the vehicle stalls. 41. Remove the shop air supply from J 35800-A. 42. Depressurize the J 35800-A. 43. Disconnect the J 35800-A hose from the J 44466-12. 44. Remove the PCV clean air tube from the air inlet tube and set aside. 45. Remove the bonnet from the throttle body, and set aside. 46. Remove ignition wires 1, 3, 5, and 7 from the distributor cap. 47. Remove the brake booster vacuum hose and connector from the intake manifold. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5962 48. Bleed the residual pressure from the J 44466-12. 49. Remove J 44466-13 (1) and J 44466-12 (2) from the metering body. 50. Remove J 44466-13 (1), clamp (2), and J 44466-11 (4), from the fuel pipe (3). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5963 51. Install the fuel pipe (3) to the metering body. Make sure that all of the 0-rings (6 and 8), washers (7), and spacers (5) are present and in their proper position. 52. Install the clamp (2) and nuts (1). Tighten Tighten the nuts to 3 N.m (27 lb in). 53. Apply threadlock, P/N 12345382, or equivalent to the threads of the fuel pipe bolt (4). Install the bolt. Tighten Tighten the fuel pipe bolt to 6 N.m (53 lb in). 54. Install the brake booster vacuum hose and connector to the intake manifold. 55. Install the bonnet and air inlet tube to the throttle body. 56. Install the PCV fresh air tube to the inlet duct. 57. Install ignition wires 1, 3, 5 (7) to the distributor cap. 58. Add one (1) ounce of Port Fuel Injector Cleaner, P/N 12345104 (Canada P/N 10953467), to the vehicle fuel tank for each gallon of gasoline estimated to be in the tank. Instruct the customer to add the remainder of the bottle of Port Fuel Injector Cleaner to the vehicle fuel tank at the next fill-up. Further recommend that Port Fuel Injector Cleaner be added to the fuel tank every 3000 miles (4800 km) particularly if the vehicle is not started and driven every day. Inform the customer that the Port Fuel Injector Cleaner is not to be used at every fill up but may be reapplied every 3000 miles (4800 km). 59. Tighten the fuel tank filler cap. 60. Start the vehicle and check for fuel leaks. 61. Using the Tech 2(R) scan tool, check for any stored Powertrain DTC codes. Clear codes as required. 62. Disconnect the Tech 2(R) Scan tool. 63. Advise the customer to change brands of fuel. M/L, G Van and P Truck 1. Loosen the fuel tank filler cap to relieve fuel tank vapor pressure. 2. Remove the engine cover. 3. Remove ignition wires 1 3, 5, and 7 from the distributor cap. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5964 4. Remove the vacuum brake booster hose and connector from the intake manifold. 5. Remove the fuel pipe bolt (4) at the rear of the intake manifold. 6. Relieve the fuel system pressure at the service fitting on the fuel pipe. Use a shop towel to contain any fuel that may exit the service fitting. 7. Disconnect the fuel pipes (3) at the rear of intake manifold (1). 8. Remove the nuts (1) and clamp (2) from the fuel pipe. 9. Remove the fuel pipes from the metering body. Be careful not to disturb the 0-rings, washer, and spacer in the metering body. 10. Remove the electrical connector from metering body. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5965 11. Install J 44466-12 (2) and J 44466-13 (1) to the fuel metering body and tighten. Make sure that the fuel pipe 0-rings, washer, and spacers are present and in their proper position. 12. Install J 44466-01 (1) to the vehicle fuel lines. 13. Obtain the J 41413, close the valve (2) on the tank, and remove the regulator assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5966 14. Install the J 44466-10 (5) to the J 41413 tank (3). The J 44466-10 regulator is preset to 150 psi. The minimum pressure required on the gauge (6) is 150 psi. If 150 psi is not obtained, the tank must be refilled prior to performing this procedure. 15. Connect the J 44466-10 hose to the J 44466-12. 16. Install J 39021 Injector/Coil Balance Tester, the J 39021-210 Injector Tester Adapter Box, and J 39021-301 V6 Fuel Injector Test Adapter or J 39021-302 V8 Fuel Injector Test Adapter to metering body electrical connector. 17. Adjust the amperage selector switch on J 39021 to 0.5 amps. 18. Open the valve (2) on the tank (3). 19. Open the valve (4) on the J 44466-10 to pressurize the fuel system. 20. Close the valve (4) on the J 44466-10. 21. Energize one injector using the J 39021. Observe a pressure drop on the gauge (6) and verify the injector/poppet valve operation. An injector/poppet that is "stuck" and not operational will have no pressure drop on the gauge. If an injector remains "stuck", repeat the procedure multiple times (as required) until the injector is operational. 22. Repeat steps 19, 20, and 21, for each individual injector to verify that all injector/poppet valve assemblies are "unstuck" and functional. 23. Shut off the pressure valve (2) on the tank (3) of the J 41413. 24. Bleed off pressure at J 44466-10. 25. Disconnect and remove the J 44466-10 hose from the J 44466-12 and the J 41413. 26. Remove the J 39021-301 or J 39021-210, J 39021-210, and J 39021 from the metering body. 27. Install the vehicle electrical connector to the metering body. 28. Install ignition wires 1, 3, 5, and 7 to the distributor cap. 29. Install the vacuum brake booster hose and connector to the intake manifold. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5967 30. Obtain J 35800-A (2). Make sure the valve (3) at the bottom of the canister is closed. 31. Remove the canister top and add 24 ml (0.8 fl. oz.) Top Engine Cleaner, P/N 1050002 (Canada P/N 992872), to the canister. 32. Fill the remainder of the canister with regular unleaded gasoline and install the canister top. 33. Suspend the J 35800-A in a convenient location. 34. Connect the hose from the J 35800-A to the service port on the J 44466-12. 35. Open the valve (3) at the bottom of J 35800-A. 36. Connect a "shop air" source to the fitting at the top of J 35800-A and adjust the regulator (1) to 75 psi. 37. Start the vehicle. It may be necessary to re-adjust the J 35800-A pressure regulator to maintain 75 psi. 38. Let the vehicle run at idle until the canister is empty and the vehicle stalls. 39. Remove the shop air supply from J 35800-A. 40. Depressurize the J 35800-A. 41. Disconnect the J 35800-A hose from the J 44466-12. 42. Remove the vacuum brake booster hose and connector from the intake manifold. 43. Remove ignition wires 1, 3, 5, and 7 from the distributor cap. 44. Bleed the residual pressure from J 44466-12. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5968 45. Remove the J 44466-13 (1) and J 44466-12 (2) from the metering body. 46. Remove the J 44466-01 (1) from the vehicle fuel lines. 47. Install the fuel pipe (3) to the metering body. Make sure the all of the 0-rings (6 and 8), washers (7), and spacers (5) are present and in their proper position. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5969 48. Install the clamp (2) and nuts (1). Tighten Tighten the nuts to 3 N.m (27 lb in). 49. Inspect the 0-rings at the fuel pipe-to-vehicle lines (1). Replace as necessary. Tighten Tighten the fuel line nuts to 30 N.m (22 lb ft). 50. Apply threadlock, P/N 12345382, or equivalent to the threads of the fuel pipe bolt. Install the bolt. Tighten Tighten the fuel pipe bolt to 6 N.m (53 lb in). 51. Install ignition wires 1, 3, 5, and 7 to the distributor cap. 52. Install the vacuum brake booster hose and connector to the intake manifold. 53. Add one (1) ounce of Port Fuel Injector Cleaner, P/N 12345104 (Canada P/N 10953467), to the vehicle fuel tank for each gallon of gasoline estimated to be in the tank. Instruct the customer to add the remainder of the bottle of Port Fuel Injector Cleaner to the vehicle fuel tank at the next fill-up. Further recommend that Port Fuel Injector Cleaner be added to the fuel tank every 3000 miles (4800 km) particularly if the vehicle is not started and driven every day. Inform the customer that the Port Fuel Injector Cleaner is not to be used at every fill up but may be reapplied every 3000 miles (4800 km). 54. Tighten the fuel tank filler cap. 55. Start the engine and check for fuel leaks. 56. Use the Tech 2(R) Scan Tool to check for any stored Powertrain DTC codes. Clear codes as required. 57. Disconnect the Tech 2(R) Scan tool. 58. Install the engine cover. 59. Advise customer to change brands of fuel. Central SFI to MFI Conversion Instructions This procedure outlines the steps required to replace the existing Central SFI Fuel System with a new MFI (Multiport Flexible Injection) Fuel System. Be sure to use the appropriate year and model Service Manual for proper disassembly and re-assembly procedure(s). Important: Cleaning the CSFI injectors is the preferred repair. The CSFI unit should not be replaced until cleaning has been attempted. If the vehicle should Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5970 return for the same repair, then the CSFI unit can be replaced with a MFI unit. If the vehicle is out of warranty, the customer should be given the option of which fix to pursue. V6 Engines 1. Remove Upper Intake Manifold plenum and SFI Fuel Meter Body according to Service Manual Procedures. 2. Remove the Fuel Meter Body bracket and discard. Install the new bracket as shown in Figure 1. 3. Position Fuel Tubes of MFI Fuel Meter Body as shown in Figure 2. Tubes must be oriented away from the fuel pressure regulator end of the fuel meter body. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5971 Notice: The number 3 Fuel Tube must be positioned behind the number 1 Fuel Tube to eliminate interference with the Upper Intake Manifold plenum when installed. See Figure 2. 4. Insert the MFI Fuel Meter Body into the Fuel Meter Body Bracket on the Lower Intake Manifold being careful not to bind the Fuel Tubes. Make sure that the number three Fuel Tube is routed in behind number 1 and 5 Fuel Tubes as shown in Figure 2. Push down firmly on the fuel meter body locking it into the bracket. Notice: Use caution when inserting injectors into lower intake manifold to be sure the correct injector is being placed into the correct hole. Injectors should not be removed once they have been installed. Removal of injectors from the intake manifold may cause damage to the retaining lugs on the injector. Important: The Injector holes are numbered on the Lower Intake Manifold. The injectors are numbered on the side of the Fuel Meter Body. 5. Insert the number 3 injector into the correct Injector hole in the Lower Intake Manifold first. Install the number 5 injector next and then number 1. This sequence must be followed correctly to prevent interference of the Fuel Tubes. Injectors 2, 4, and 6 are then installed. 6. Insure that the electrical connectors of the injectors are positioned so that they do not interfere with each other and are pointing towards the center of the Intake Manifold. If necessary, rotate the electrical connectors inboard. Notice: Lack of lubrication will make installation of the Upper Intake Manifold plenum difficult and may cause damage to the 0-ring. 7. Lubricate the Fuel Meter Body Upper Manifold 0-ring (orange in color) with clean engine oil. 8. Inspect the Upper Intake Manifold plenum gasket and replace if necessary. Reinstall the Upper Intake Manifold plenum following the procedures outlined in the Service Manual. Important: Lubricate the Fuel Inlet and Return Lines with clean engine oil before inserting them into the Fuel Meter Body. Make sure that the Fuel Line Retaining Bracket is properly oriented with the tabs down. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5972 V8 Engines This procedure outlines the steps required to replace the existing Central SFI Fuel System with a new MFI (Multipoint Flexible Injection) Fuel System. Be sure to use the appropriate year and model Service Manual for proper disassembly and re-assembly procedure(s). 1. Remove Upper Intake Manifold plenum and SFI Fuel Meter Body according to Service Manual Procedures. 2. Remove the Fuel Meter Body bracket and discard. Install the new bracket. 3. Position Fuel Tubes of MFI Fuel Meter Body as shown in Figure 3. Fuel tubes 1, 3, 5, and 7 are oriented toward the fuel inlet side of the fuel meter body. Fuel tubes 2, 4, 6, and 8 are oriented toward the fuel pressure regulator side if the fuel meter body. 4. Insert the MFI Fuel Meter Body into the Fuel Meter Body Bracket on the Lower Intake Manifold being careful not to bind the Fuel Tubes. Push down firmly on the fuel meter body until the tabs snap into the bracket locking the fuel meter body in place. 5. Orient the fuel tubes to coincide with their corresponding cylinder. The fuel tubes are numbered on the side of the fuel meter body and the corresponding cylinder number is cast in the intake manifold. Notice: Use caution when inserting injectors into lower intake manifold to be sure the correct injector is being placed into the correct hole. Injectors should not be removed once they have been installed. Removal of injectors from the intake manifold may cause damage to the retaining lugs on the injector. Important: The Injector holes are numbered on the Lower Intake Manifold. The injectors are numbered on the side of the Fuel Meter Body. 6. Insert the fuel tubes into their corresponding holes in the intake manifold. Install tubes for cylinders 1, 3, 6 and 8 making sure that the injector electrical connectors are facing in toward the center of the manifold. 7. Insert fuel tubes for cylinders 2, 4, 5, and 7 in the same manner. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5973 Important: When installing fuel tubes, it is important that the tubes are oriented properly to provide minimal interference when installing the upper intake manifold plenum. Intake holes for cylinders 2, 4, 5, and 7 are closer to the fuel meter body. It is necessary to cross tube 5 over tube 7 and tube 4 over tube 2 as shown in Figure 4. Notice: Lack of lubrication will make installation of the Upper Intake Manifold plenum difficult and may cause damage to the 0-ring. 8. Lubricate the Fuel Meter Body Upper Manifold 0-ring (blue in color) with clean engine oil. 9. Inspect Upper Intake Manifold Gasket and replace if necessary. Reinstall the Upper Intake Manifold plenum following the procedures in the Service Manual. Important: Lubricate the Fuel Inlet and Return Lines with clean engine oil before inserting them in the of the Fuel Meter Body. Make sure that Fuel Line Retaining Bracket is properly oriented with the tabs down. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 04-06-04-051B > Jan > 06 > Fuel System - Fuel Injector Maintenance Cleaning Fuel Injector: All Technical Service Bulletins Fuel System - Fuel Injector Maintenance Cleaning Bulletin No.: 04-06-04-051B Date: January 04, 2006 INFORMATION Subject: Maintenance Cleaning of Fuel Injectors Models: 2006 and Prior All General Motors Passenger Cars and Trucks 2003-2006 HUMMER H2 2006 HUMMER H3 Supercede: This bulletin is being revised to add models and model years and update the name and part number of GM Fuel System Treatment. Please discard Corporate Bulletin Number 04-06-04-051A (Section 06 - Engine/Propulsion System). General Motors is aware that some companies are marketing tools, equipment and programs to support fuel injector cleaning as a preventative maintenance procedure. General Motors does not endorse, support or acknowledge the need for fuel injector cleaning as a preventative maintenance procedure. Fuel injector cleaning is approved only when performed as directed by a published GM driveability or DTC diagnostic service procedure. Due to variation in fuel quality in different areas of the country, the only preventative maintenance currently endorsed by GM regarding its gasoline engine fuel systems is the addition of GM Fuel System Treatment PLUS, P/N 88861011 (for U.S. ACDelco(R), use P/N 88861013) (in Canada, P/N 88861012), added to a tank of fuel at each oil change. Refer to Corporate Bulletin Number 03-06-04-030A for proper cleaning instructions. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed Fuel Injector: All Technical Service Bulletins Campaign - Fuel Injector Sticking Closed File In Section: 06-Engine Emissions Bulletin No.: 99066F Date: March, 2003 SPECIAL POLICY SUBJECT: 99066F - SPECIAL POLICY ADJUSTMENT - SEQUENTIAL CENTRAL PORT FUEL INJECTION (SCPI) FAILURES IN CALIFORNIA ONLY (YF5 EMISSION EQUIPPED) MODELS: CERTAIN 1996, 1997, 1998, 1999, 2000, 2001, 2002 S/T, M/L, C/K, G, P, W4/NPR TRUCKS AND 2003 NPR TRUCKS EQUIPPED WITH 4.3L (RPO L35 - VIN CODE W OR RPO LF6 - VIN CODE X), 5.0L (RPO L30 - VIN CODE M) OR 5.7L (RPO L31 - VIN CODE R) ENGINE AND CALIFORNIA EMISSION EQUIPPED (RPO YF5) This bulletin is being revised to add the 2002 and 2003 model years to the SCPI Special Policy on certain S/T, M/L, C/K, G, P and W4/NPR truck models. Please discard Special Policy Bulletin Number 99066E, dated February, 2003. CONDITION Some customers of 1996, 1997, 1998, 1999, 2000, 2001, 2002 model year S/T, M/L, C/K, G, P, W4/NPR trucks and 2003 NPR trucks, that are registered in California, equipped with 4.3L (RPO L35 and VIN Code W, or RPO LF6 and VIN Code X), 5.0L (RPO L30 and VIN Code M) or 5.7L (RPO L31 and VIN Code R) engine, and California emissions (RPO YF5), may experience a "Service Engine Soon" light, misfire, rough idle or hard start due to a deposit build-up on the Sequential Central Port Fuel Injector (SCPI) poppet valve(s). The deposit build-up may cause injector poppets to stick closed. Certain fuels have been found to interact with the SCPI system to cause the deposits. SPECIAL POLICY ADJUSTMENT This special policy covers the SCPI failure condition described above for a period of ten (10) years or 200,000 miles, whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership. The repairs will be made at no charge to the owner. This special policy applies ONLY to repairs requiring SCPI system servicing, injector cleaning and/or MFI assembly replacement of the SCPI system. The customer should not be charged for performing a system check when it is determined that the SCPI system is not the cause of a customer complaint (labor operation T5532 is provided to submit claims for such system checks). Any additional necessary diagnosis and repairs that are not related to the SCPI condition are not covered by this special policy. The customer should be informed that any further service that is not covered by new vehicle warranty will not be covered by this policy. VEHICLES INVOLVED Involved are certain 1996,1997,1998,1999, 2000, 2001, 2002 S/T, M/L, C/K, G, P, W4/NPR and 2003 NPR model vehicles, registered in California, equipped with 4.3L (RPO L35 - VIN Code W, or RPO LF6 - VIN Code X), 5.0L (RPO L30 - VIN Code M) or 5.7L (RPO L31 - VIN Code R) engine; and California emissions (RPO YF5). This Special Policy covers all vehicles within these model years, with these engine and emissions RPO's. PARTS INFORMATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed > Page 5983 Parts required to complete this special policy are to be obtained from General Motors Service Parts Operations (GMSPO). Please refer to your "involved vehicles listing" prior to ordering parts. Normal orders should be placed on a DRO Daily Replenishment Order. In an emergency, parts should be ordered on a CSO = Customer Special Order. IMPORTANT: Isuzu Parts Ordering: In order to comply with the 10-digit Isuzu part numbering system, Isuzu dealers must add an "8" to the beginning and a "0" to the end of the listed 8-digit part numbers when ordering parts through AIPDN. CUSTOMER NOTIFICATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed > Page 5984 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed > Page 5985 Customers will be notified of this special policy on their vehicles by General Motors (see copy of typical customer letter included with this bulletin - actual divisional letter may vary slightly). SERVICE PROCEDURE System Check: Use strategy-based diagnoses listed in the front of the Driveability and Emissions section of the service manual. If the SCPI system is operating properly, inform the customer that the vehicle does not have the condition listed in the owner letter. If poor driveability conditions persist, inform the customer that any further diagnosis and repairs will be at their expense if the vehicle is outside the parameters of the new vehicle warranty. SCPI Injector Cleaning Procedure: If diagnosis leads to sticking poppet nozzles, use the service procedure from Service Bulletin 00-06-04-003B to clean the SCPI poppet nozzles. Please note that the service bulletin term for SCPI is Central Sequential Fuel Injection (CSFI), but is referring to the same fuel system assembly. If the poppet nozzles have previously been cleaned and the sticking condition has reoccurred, refer to the correction paragraph below. SCPI Fuel Tank Fill Pipe Assembly for 1997-99 M/L Van and 1999 - some 2000 C/K Truck: with 4.3L, 5.0L, 5.7L engines and built prior to listed VIN/Production dates on Service Bulletin 00-06-04-018: If diagnosis leads to sticking poppet nozzles on these models, use the service procedure from Service Bulletin 00-06-04-018 to replace the fuel tank fill pipe assembly, if this procedure has not been performed previously. Previous service procedure can be verified by checking GMVIS for Labor Operation L1065 on "M/L" trucks with replacement part number 15050573; or Labor Operation L1065 on "C/K" trucks with replacement part numbers 15747585 or 15747588. Correction: If, after cleaning the SCPI poppet nozzles, the normal service manual diagnosis still indicates that the SCPI is the cause of the customer complaint, or if the injectors have previously been cleaned and the vehicle has again experienced sticking poppet nozzles, refer to Service Bulletin 00-06-04-003B and replace the SCPI fuel assembly with the MFI fuel assembly. Please note that the service bulletin term for SCPI is Central Sequential Fuel Injection (CSFI), but is referring to the same fuel system assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed > Page 5986 CLAIM INFORMATION For vehicles repaired under this special policy, submit a claim with the information indicated. CUSTOMER REIMBURSEMENT Customer requests for reimbursement are for any previously paid repairs to, or replacement of, the Sequential Central Port Fuel Injection (SCPI) system. Repairs must have occurred within 10 years of the date the vehicle was originally placed in service, or 200,000 miles, whichever occurs first. The requests are to be submitted within two (2) years of the date on which the repair was paid or within two (2) years of the date of this Special Policy Bulletin, whichever is greater. When a customer requests reimbursement, they must provide the following: - Proof of ownership at time of repair. - Original paid receipt confirming the amount of unreimbursed repair expense(s) (including Service Contract deductibles), a description of the repair, and the person or entity performing the repair. Customers from the State of California, must submit requests for reimbursement directly to (Divisions) per instructions in the owner letter. If the work was done by someone other than a GM dealership, the amount of reimbursement will be limited to the amount that the repair would have cost GM to have it completed by a GM dealership. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up Technical Service Bulletin # 00-06-04-003B Date: 030201 Fuel System - MIL ON/Rough Idle on Start-Up File In Section: 06 - Engine/Propulsion System Bulletin No.: 00-06-04-003B Date: February, 2003 TECHNICAL Subject: Rough Idle After Start, And/Or A Service Engine Soon (SES) Light (Unstick And Clean Central Sequential Fuel Injection (CSFI) Poppet Valves or Convert to MFI) Models: 1995-2002 Chevrolet and GMC S/T Models 1996-2002 Chevrolet and GMC C/K, M/L, G, P Models 1996-2001 Oldsmobile Bravada 1999-2000 Cadillac Escalade with 4.3L, 5.0L or 5.7L Engine (VINS W, X, M, R - RPOs L35, LF6, L30, L31) Except 2002 VIN X - RPO LU3 Models This bulletin is being revised to update the Warranty Information. Please discard previous copies of Corporate Bulletin Number 00-06-04-003B with warranty chart (Section 06 - Engine). This copy is for Dealers in the state of CALIFORNIA ONLY. Condition Some customers may comment on rough idle after start-up, especially if the vehicle has sat overnight. These symptoms may be intermittent. The Service Engine Soon (SES) light may also be illuminated. Current misfire or history misfire codes may be detected with the Tech 2 scan tool. Cause A deposit build-up on the CSFI poppet valve ball and/or seat may cause the poppet ball to stick open or closed. In either case, the specific cylinder will be mis-fueled, resulting in a cylinder mis-fire condition. Correction A new injector unsticking and cleaning process has proven to be effective in restoring poppet valves to an "as new" condition. CSFI injector replacement should NOT be considered as a correction for this customer concern. Check the vehicle history to determine if the vehicle is returning for a second fuel system repair for this condition. If the fuel system has been repaired for this condition previously, then inform the customer that an alternate fix is available. A new MFI fuel system has been developed that will back service the CSFI fuel system. The MFI fuel system eliminates the CSFI poppet valve ball and seat. The CSFI fuel system will need to be replaced as a unit. Refer to Central SFI to MFI Conversion instructions in this bulletin. Notice: Individual CSFI injectors can not be replaced with MFI injectors. The entire CSFI fuel meter body will need to be replaced. The bracket used to retain the injectors in the fuel meter body is different between the CSFI and MFI unit. The unit may not seal if you mix injectors. Severe engine damage could result. Cleaning the CSFI injectors is the preferred repair. The CSFI unit should not be replaced until cleaning has been attempted. If the vehicle should return for the same repair, then the CSFI unit can be replaced with an MFI unit. If the vehicle is out of warranty, the customer should be given the option of which fix to pursue. Important: "GM of Canada" dealers require District Service Manager approval prior to replacing the CSFI unit with a MFI unit under warranty. The first step of this process is to use the J 41413 Evap Pressure/Purge Station, in conjunction with the J 44466-10 pressure regulator/hose assembly, to provide the required high pressure (150 psi) source to perform the unsticking procedure. The J 39021 fuel injector tester and accessories provide the means to "energize" the injector. Some later model-year vehicles may utilize the Tech 2(R) to "energize" the injectors. The second step of this process is to run the engine on a solution of 10% Top Engine Cleaner and 90% gasoline. This will effectively clean any deposits from the ball and seats of the poppets. It is very important that the engine fuel system is separated from the vehicle fuel system. Top Engine Cleaner may have detrimental effects on the fuel pump. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5991 Parts Information Cleaning Procedure Parts CSFI to MFI Conversion Parts Parts are currently available from GMSPO. Warranty Information Important: Some California vehicles may be covered by Special Policy 99066E if built with California Emissions RPO YF5. If the vehicle is covered by the special policy, then that warranty information should be used. For vehicles repaired under warranty, use information contained in Special Policy 99066E. Information This procedure should be performed before any attempt to convert the fuel system to MFI. S/T and C/K Truck 1. Loosen the fuel filler cap to relieve vapor pressure in the fuel tank. 2. Remove the Positive Crankcase Ventilation (PCV) clean air tube from the air inlet tube and set aside. 3. Remove the bonnet and inlet tube from the throttle body. 4. Remove the brake booster vacuum hose and connector from the intake manifold. 5. Remove the electrical connector from the CSFI fuel metering body. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5992 6. Remove ignition wires 1, 3, 5, and 7 from the distributor cap. 7. Remove the fuel line bolt (4) at the rear of the intake manifold. 8. Relieve the fuel system pressure at the service fitting on the fuel line. Use a shop towel to contain any fuel that may exit the service fitting. 9. Remove the nuts (1) and clamp (2) from the fuel pipe. 10. Remove the fuel pipes from the metering body. Be careful not to disturb the O-rings, washer, and spacer in the metering body. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5993 11. Install the J 44466-12 (2) and the J 44466-13 (1) to the metering body and tighten. Make sure that the fuel pipe 0-rings, washer, and spacers are present and in their proper position. 12. Install the J 44466-11 (4), clamp (2), and J 44466-13 (1) to the fuel pipe and tighten. 13. Obtain the J 41413, close the valve (2) on the tank, and remove the regulator assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5994 14. Install the J 44466-10 (5) to the J 41413 tank (3). The J 44466-10 regulator is preset to 150 psi. 15. Connect the J 44466-10 hose (1) to the J 44466-12 (3). 16. Install the J 39021 Injector/Coil Balance Tester, the J 39021-210 Injector Tester Adapter Box, and J 39021-301 V6 Fuel Injector Test Adapter (1) or J 39021-302 V8 Fuel Injector Test Adapter to the metering body electrical connector. 17. Adjust the amperage selector switch on J 39021 to 0.5 amps. 18. Open the valve (2) on the tank (3). 19. Open the valve (4) on the J 44466-10 to pressurize the fuel system. The minimum pressure required on the gauge (6) is 150 psi. If 150 psi is not obtained, the tank (3) must be refilled prior to performing this procedure. 20. Close the valve (4) on the J 44466-10. 21. Energize one injector using the J 39021. Observe a pressure drop on the gauge (6) and verity the injector/poppet valve operation. An injector/poppet that is "stuck" and not operational will have no pressure drop on the gauge. It an injector remains "stuck", repeat the procedure multiple times (as required) until the injector is operational. 22. Repeat Steps 19, 20 and 21 for each individual injector to verify that all injector/poppet valve assemblies are "unstuck" and functional. 23. Shut off pressure valve (2) on the tank (3) of the J 41413. 24. Bleed off the pressure at the J 44466-10. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5995 25. Disconnect and remove the J 44466-10 (5) from the J 44466-12, and the J 41413. 26. Remove the J 39021-301 or J 39021-302, J 39021-210, and J 39021 from the metering body. 27. Install the vehicle electrical connector to the metering body. 28. Install the brake booster vacuum hose and connector to the intake manifold. 29. Install ignition wires 1, 3, 5, and 7 to the distributor cap. 30. Install the air inlet bonnet 10 the throttle body, tighten the wing-nut. 31. Install the PCV fresh air tube to the air inlet tube. 32. Obtain J 35800-A (2). Make sure the valve at the bottom of the canister (3) is closed. 33. Remove the canister top and add 24 ml (0.8 fl. oz.) Top Engine Cleaner, P/N 1050002 (Canada P/N 992872), to the canister. 34. Fill the remainder of the canister with regular unleaded gasoline and install the canister top. 35. Suspend J 35800-A from a convenient underhood location. 36. Connect the hose from J 35800-A to the service port on the J 44466-12 37. Open the valve (3) at the bottom of J 35800-A. 38. Connect a "shop air" source to the fitting at the top of J 35800-A and adjust the regulator (1) to 75 psi. 39. Start the vehicle. It may be necessary to re-adjust the J 35800-A pressure regulator to maintain 75 psi. 40. Let the vehicle run at idle until the canister is empty and the vehicle stalls. 41. Remove the shop air supply from J 35800-A. 42. Depressurize the J 35800-A. 43. Disconnect the J 35800-A hose from the J 44466-12. 44. Remove the PCV clean air tube from the air inlet tube and set aside. 45. Remove the bonnet from the throttle body, and set aside. 46. Remove ignition wires 1, 3, 5, and 7 from the distributor cap. 47. Remove the brake booster vacuum hose and connector from the intake manifold. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5996 48. Bleed the residual pressure from the J 44466-12. 49. Remove J 44466-13 (1) and J 44466-12 (2) from the metering body. 50. Remove J 44466-13 (1), clamp (2), and J 44466-11 (4), from the fuel pipe (3). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5997 51. Install the fuel pipe (3) to the metering body. Make sure that all of the 0-rings (6 and 8), washers (7), and spacers (5) are present and in their proper position. 52. Install the clamp (2) and nuts (1). Tighten Tighten the nuts to 3 N.m (27 lb in). 53. Apply threadlock, P/N 12345382, or equivalent to the threads of the fuel pipe bolt (4). Install the bolt. Tighten Tighten the fuel pipe bolt to 6 N.m (53 lb in). 54. Install the brake booster vacuum hose and connector to the intake manifold. 55. Install the bonnet and air inlet tube to the throttle body. 56. Install the PCV fresh air tube to the inlet duct. 57. Install ignition wires 1, 3, 5 (7) to the distributor cap. 58. Add one (1) ounce of Port Fuel Injector Cleaner, P/N 12345104 (Canada P/N 10953467), to the vehicle fuel tank for each gallon of gasoline estimated to be in the tank. Instruct the customer to add the remainder of the bottle of Port Fuel Injector Cleaner to the vehicle fuel tank at the next fill-up. Further recommend that Port Fuel Injector Cleaner be added to the fuel tank every 3000 miles (4800 km) particularly if the vehicle is not started and driven every day. Inform the customer that the Port Fuel Injector Cleaner is not to be used at every fill up but may be reapplied every 3000 miles (4800 km). 59. Tighten the fuel tank filler cap. 60. Start the vehicle and check for fuel leaks. 61. Using the Tech 2(R) scan tool, check for any stored Powertrain DTC codes. Clear codes as required. 62. Disconnect the Tech 2(R) Scan tool. 63. Advise the customer to change brands of fuel. M/L, G Van and P Truck 1. Loosen the fuel tank filler cap to relieve fuel tank vapor pressure. 2. Remove the engine cover. 3. Remove ignition wires 1 3, 5, and 7 from the distributor cap. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5998 4. Remove the vacuum brake booster hose and connector from the intake manifold. 5. Remove the fuel pipe bolt (4) at the rear of the intake manifold. 6. Relieve the fuel system pressure at the service fitting on the fuel pipe. Use a shop towel to contain any fuel that may exit the service fitting. 7. Disconnect the fuel pipes (3) at the rear of intake manifold (1). 8. Remove the nuts (1) and clamp (2) from the fuel pipe. 9. Remove the fuel pipes from the metering body. Be careful not to disturb the 0-rings, washer, and spacer in the metering body. 10. Remove the electrical connector from metering body. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 5999 11. Install J 44466-12 (2) and J 44466-13 (1) to the fuel metering body and tighten. Make sure that the fuel pipe 0-rings, washer, and spacers are present and in their proper position. 12. Install J 44466-01 (1) to the vehicle fuel lines. 13. Obtain the J 41413, close the valve (2) on the tank, and remove the regulator assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6000 14. Install the J 44466-10 (5) to the J 41413 tank (3). The J 44466-10 regulator is preset to 150 psi. The minimum pressure required on the gauge (6) is 150 psi. If 150 psi is not obtained, the tank must be refilled prior to performing this procedure. 15. Connect the J 44466-10 hose to the J 44466-12. 16. Install J 39021 Injector/Coil Balance Tester, the J 39021-210 Injector Tester Adapter Box, and J 39021-301 V6 Fuel Injector Test Adapter or J 39021-302 V8 Fuel Injector Test Adapter to metering body electrical connector. 17. Adjust the amperage selector switch on J 39021 to 0.5 amps. 18. Open the valve (2) on the tank (3). 19. Open the valve (4) on the J 44466-10 to pressurize the fuel system. 20. Close the valve (4) on the J 44466-10. 21. Energize one injector using the J 39021. Observe a pressure drop on the gauge (6) and verify the injector/poppet valve operation. An injector/poppet that is "stuck" and not operational will have no pressure drop on the gauge. If an injector remains "stuck", repeat the procedure multiple times (as required) until the injector is operational. 22. Repeat steps 19, 20, and 21, for each individual injector to verify that all injector/poppet valve assemblies are "unstuck" and functional. 23. Shut off the pressure valve (2) on the tank (3) of the J 41413. 24. Bleed off pressure at J 44466-10. 25. Disconnect and remove the J 44466-10 hose from the J 44466-12 and the J 41413. 26. Remove the J 39021-301 or J 39021-210, J 39021-210, and J 39021 from the metering body. 27. Install the vehicle electrical connector to the metering body. 28. Install ignition wires 1, 3, 5, and 7 to the distributor cap. 29. Install the vacuum brake booster hose and connector to the intake manifold. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6001 30. Obtain J 35800-A (2). Make sure the valve (3) at the bottom of the canister is closed. 31. Remove the canister top and add 24 ml (0.8 fl. oz.) Top Engine Cleaner, P/N 1050002 (Canada P/N 992872), to the canister. 32. Fill the remainder of the canister with regular unleaded gasoline and install the canister top. 33. Suspend the J 35800-A in a convenient location. 34. Connect the hose from the J 35800-A to the service port on the J 44466-12. 35. Open the valve (3) at the bottom of J 35800-A. 36. Connect a "shop air" source to the fitting at the top of J 35800-A and adjust the regulator (1) to 75 psi. 37. Start the vehicle. It may be necessary to re-adjust the J 35800-A pressure regulator to maintain 75 psi. 38. Let the vehicle run at idle until the canister is empty and the vehicle stalls. 39. Remove the shop air supply from J 35800-A. 40. Depressurize the J 35800-A. 41. Disconnect the J 35800-A hose from the J 44466-12. 42. Remove the vacuum brake booster hose and connector from the intake manifold. 43. Remove ignition wires 1, 3, 5, and 7 from the distributor cap. 44. Bleed the residual pressure from J 44466-12. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6002 45. Remove the J 44466-13 (1) and J 44466-12 (2) from the metering body. 46. Remove the J 44466-01 (1) from the vehicle fuel lines. 47. Install the fuel pipe (3) to the metering body. Make sure the all of the 0-rings (6 and 8), washers (7), and spacers (5) are present and in their proper position. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6003 48. Install the clamp (2) and nuts (1). Tighten Tighten the nuts to 3 N.m (27 lb in). 49. Inspect the 0-rings at the fuel pipe-to-vehicle lines (1). Replace as necessary. Tighten Tighten the fuel line nuts to 30 N.m (22 lb ft). 50. Apply threadlock, P/N 12345382, or equivalent to the threads of the fuel pipe bolt. Install the bolt. Tighten Tighten the fuel pipe bolt to 6 N.m (53 lb in). 51. Install ignition wires 1, 3, 5, and 7 to the distributor cap. 52. Install the vacuum brake booster hose and connector to the intake manifold. 53. Add one (1) ounce of Port Fuel Injector Cleaner, P/N 12345104 (Canada P/N 10953467), to the vehicle fuel tank for each gallon of gasoline estimated to be in the tank. Instruct the customer to add the remainder of the bottle of Port Fuel Injector Cleaner to the vehicle fuel tank at the next fill-up. Further recommend that Port Fuel Injector Cleaner be added to the fuel tank every 3000 miles (4800 km) particularly if the vehicle is not started and driven every day. Inform the customer that the Port Fuel Injector Cleaner is not to be used at every fill up but may be reapplied every 3000 miles (4800 km). 54. Tighten the fuel tank filler cap. 55. Start the engine and check for fuel leaks. 56. Use the Tech 2(R) Scan Tool to check for any stored Powertrain DTC codes. Clear codes as required. 57. Disconnect the Tech 2(R) Scan tool. 58. Install the engine cover. 59. Advise customer to change brands of fuel. Central SFI to MFI Conversion Instructions This procedure outlines the steps required to replace the existing Central SFI Fuel System with a new MFI (Multiport Flexible Injection) Fuel System. Be sure to use the appropriate year and model Service Manual for proper disassembly and re-assembly procedure(s). Important: Cleaning the CSFI injectors is the preferred repair. The CSFI unit should not be replaced until cleaning has been attempted. If the vehicle should Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6004 return for the same repair, then the CSFI unit can be replaced with a MFI unit. If the vehicle is out of warranty, the customer should be given the option of which fix to pursue. V6 Engines 1. Remove Upper Intake Manifold plenum and SFI Fuel Meter Body according to Service Manual Procedures. 2. Remove the Fuel Meter Body bracket and discard. Install the new bracket as shown in Figure 1. 3. Position Fuel Tubes of MFI Fuel Meter Body as shown in Figure 2. Tubes must be oriented away from the fuel pressure regulator end of the fuel meter body. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6005 Notice: The number 3 Fuel Tube must be positioned behind the number 1 Fuel Tube to eliminate interference with the Upper Intake Manifold plenum when installed. See Figure 2. 4. Insert the MFI Fuel Meter Body into the Fuel Meter Body Bracket on the Lower Intake Manifold being careful not to bind the Fuel Tubes. Make sure that the number three Fuel Tube is routed in behind number 1 and 5 Fuel Tubes as shown in Figure 2. Push down firmly on the fuel meter body locking it into the bracket. Notice: Use caution when inserting injectors into lower intake manifold to be sure the correct injector is being placed into the correct hole. Injectors should not be removed once they have been installed. Removal of injectors from the intake manifold may cause damage to the retaining lugs on the injector. Important: The Injector holes are numbered on the Lower Intake Manifold. The injectors are numbered on the side of the Fuel Meter Body. 5. Insert the number 3 injector into the correct Injector hole in the Lower Intake Manifold first. Install the number 5 injector next and then number 1. This sequence must be followed correctly to prevent interference of the Fuel Tubes. Injectors 2, 4, and 6 are then installed. 6. Insure that the electrical connectors of the injectors are positioned so that they do not interfere with each other and are pointing towards the center of the Intake Manifold. If necessary, rotate the electrical connectors inboard. Notice: Lack of lubrication will make installation of the Upper Intake Manifold plenum difficult and may cause damage to the 0-ring. 7. Lubricate the Fuel Meter Body Upper Manifold 0-ring (orange in color) with clean engine oil. 8. Inspect the Upper Intake Manifold plenum gasket and replace if necessary. Reinstall the Upper Intake Manifold plenum following the procedures outlined in the Service Manual. Important: Lubricate the Fuel Inlet and Return Lines with clean engine oil before inserting them into the Fuel Meter Body. Make sure that the Fuel Line Retaining Bracket is properly oriented with the tabs down. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6006 V8 Engines This procedure outlines the steps required to replace the existing Central SFI Fuel System with a new MFI (Multipoint Flexible Injection) Fuel System. Be sure to use the appropriate year and model Service Manual for proper disassembly and re-assembly procedure(s). 1. Remove Upper Intake Manifold plenum and SFI Fuel Meter Body according to Service Manual Procedures. 2. Remove the Fuel Meter Body bracket and discard. Install the new bracket. 3. Position Fuel Tubes of MFI Fuel Meter Body as shown in Figure 3. Fuel tubes 1, 3, 5, and 7 are oriented toward the fuel inlet side of the fuel meter body. Fuel tubes 2, 4, 6, and 8 are oriented toward the fuel pressure regulator side if the fuel meter body. 4. Insert the MFI Fuel Meter Body into the Fuel Meter Body Bracket on the Lower Intake Manifold being careful not to bind the Fuel Tubes. Push down firmly on the fuel meter body until the tabs snap into the bracket locking the fuel meter body in place. 5. Orient the fuel tubes to coincide with their corresponding cylinder. The fuel tubes are numbered on the side of the fuel meter body and the corresponding cylinder number is cast in the intake manifold. Notice: Use caution when inserting injectors into lower intake manifold to be sure the correct injector is being placed into the correct hole. Injectors should not be removed once they have been installed. Removal of injectors from the intake manifold may cause damage to the retaining lugs on the injector. Important: The Injector holes are numbered on the Lower Intake Manifold. The injectors are numbered on the side of the Fuel Meter Body. 6. Insert the fuel tubes into their corresponding holes in the intake manifold. Install tubes for cylinders 1, 3, 6 and 8 making sure that the injector electrical connectors are facing in toward the center of the manifold. 7. Insert fuel tubes for cylinders 2, 4, 5, and 7 in the same manner. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6007 Important: When installing fuel tubes, it is important that the tubes are oriented properly to provide minimal interference when installing the upper intake manifold plenum. Intake holes for cylinders 2, 4, 5, and 7 are closer to the fuel meter body. It is necessary to cross tube 5 over tube 7 and tube 4 over tube 2 as shown in Figure 4. Notice: Lack of lubrication will make installation of the Upper Intake Manifold plenum difficult and may cause damage to the 0-ring. 8. Lubricate the Fuel Meter Body Upper Manifold 0-ring (blue in color) with clean engine oil. 9. Inspect Upper Intake Manifold Gasket and replace if necessary. Reinstall the Upper Intake Manifold plenum following the procedures in the Service Manual. Important: Lubricate the Fuel Inlet and Return Lines with clean engine oil before inserting them in the of the Fuel Meter Body. Make sure that Fuel Line Retaining Bracket is properly oriented with the tabs down. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 99-06-04-006 > Feb > 99 > Fuel - Correct Solvent for CSFI Poppet Cleaning Fuel Injector: All Technical Service Bulletins Fuel - Correct Solvent for CSFI Poppet Cleaning File In Section: 06 - Engine Bulletin No.: 99-06-04-006 Date: February, 1999 INFORMATION Subject: Correct Solvent for CSFI Poppet Cleaning Procedure Models: 1999 Cadillac Escalade 1996-99 Chevrolet, GMC S/T, M/L, C/K, G, P Models 1996-99 Oldsmobile Bravada with 4.3L, 5.0L or 5.7L Engine (VINs X, W, M, R - RPOs LF6, L35, L3O, L31) and All Transmission Types Some technicians, when servicing 1996 and newer Truck CSFI (Central Sequential Fuel Injection) fuel systems (ref. Corporate Bulletin 87-65-07A), may be using an incorrect solvent when attempting to clean CSFI poppet valves. Important: The ONLY solvent that will have any effect on the deposits occurring on poppet valves is: "PORT FUEL INJECTOR GASOLINE DETERGENT" (P/N 12345104) (IN CANADA USE P/N 12345515). The use of Goodwrench "Fuel Injector Cleaner" (P/N 12346291), or any other "Fuel Injector Cleaner" is completely non-effective, and not appropriate for this concern. Parts Information Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 616316 > Feb > 97 > Fuel System - Injection Balance Test Procedure Revised Fuel Injector: All Technical Service Bulletins Fuel System - Injection Balance Test Procedure Revised File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-63-16 Date: February, 1997 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Injector Balance Test Procedure Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7, 7.4L Engine (VINs W, X, M, R, J - RPOs L35, LF6, L30, L31, L29) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 616316 > Feb > 97 > Fuel System - Injection Balance Test Procedure Revised > Page 6016 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 616316 > Feb > 97 > Fuel System - Injection Balance Test Procedure Revised > Page 6017 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 616316 > Feb > 97 > Fuel System - Injection Balance Test Procedure Revised > Page 6018 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Injector: > 616316 > Feb > 97 > Fuel System - Injection Balance Test Procedure Revised > Page 6019 This bulletin is being issued to inform technicians of a revision to the Injector Balance Test. This revised procedure will help the technician to use the Injector Balance Test with greater clarity and accuracy. Please use this revised procedure of the Injector Balance Test for the following model years: ^ 1996-97 S/T Truck V-6 ^ 1996-97 M/L Van V-6 ^ 1996-97 G Van, V-6, V-8 ^ 1996-97 C/K Truck, V-6, V-8 ^ 1996-97 P Truck, V-6, V-8 Technicians diagnosing vehicles with misfire DTCs (P0300-P0308) must perform the Injector Coil Test and the Injector Balance Test prior to injector replacement. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 04-06-04-051B > Jan > 06 > Fuel System - Fuel Injector Maintenance Cleaning Fuel Injector: All Technical Service Bulletins Fuel System - Fuel Injector Maintenance Cleaning Bulletin No.: 04-06-04-051B Date: January 04, 2006 INFORMATION Subject: Maintenance Cleaning of Fuel Injectors Models: 2006 and Prior All General Motors Passenger Cars and Trucks 2003-2006 HUMMER H2 2006 HUMMER H3 Supercede: This bulletin is being revised to add models and model years and update the name and part number of GM Fuel System Treatment. Please discard Corporate Bulletin Number 04-06-04-051A (Section 06 - Engine/Propulsion System). General Motors is aware that some companies are marketing tools, equipment and programs to support fuel injector cleaning as a preventative maintenance procedure. General Motors does not endorse, support or acknowledge the need for fuel injector cleaning as a preventative maintenance procedure. Fuel injector cleaning is approved only when performed as directed by a published GM driveability or DTC diagnostic service procedure. Due to variation in fuel quality in different areas of the country, the only preventative maintenance currently endorsed by GM regarding its gasoline engine fuel systems is the addition of GM Fuel System Treatment PLUS, P/N 88861011 (for U.S. ACDelco(R), use P/N 88861013) (in Canada, P/N 88861012), added to a tank of fuel at each oil change. Refer to Corporate Bulletin Number 03-06-04-030A for proper cleaning instructions. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up Technical Service Bulletin # 00-06-04-003B Date: 030201 Fuel System - MIL ON/Rough Idle on Start-Up File In Section: 06 - Engine/Propulsion System Bulletin No.: 00-06-04-003B Date: February, 2003 TECHNICAL Subject: Rough Idle After Start, And/Or A Service Engine Soon (SES) Light (Unstick And Clean Central Sequential Fuel Injection (CSFI) Poppet Valves or Convert to MFI) Models: 1995-2002 Chevrolet and GMC S/T Models 1996-2002 Chevrolet and GMC C/K, M/L, G, P Models 1996-2001 Oldsmobile Bravada 1999-2000 Cadillac Escalade with 4.3L, 5.0L or 5.7L Engine (VINS W, X, M, R - RPOs L35, LF6, L30, L31) Except 2002 VIN X - RPO LU3 Models This bulletin is being revised to update the Warranty Information. Please discard previous copies of Corporate Bulletin Number 00-06-04-003B with warranty chart (Section 06 - Engine). This copy is for Dealers in the state of CALIFORNIA ONLY. Condition Some customers may comment on rough idle after start-up, especially if the vehicle has sat overnight. These symptoms may be intermittent. The Service Engine Soon (SES) light may also be illuminated. Current misfire or history misfire codes may be detected with the Tech 2 scan tool. Cause A deposit build-up on the CSFI poppet valve ball and/or seat may cause the poppet ball to stick open or closed. In either case, the specific cylinder will be mis-fueled, resulting in a cylinder mis-fire condition. Correction A new injector unsticking and cleaning process has proven to be effective in restoring poppet valves to an "as new" condition. CSFI injector replacement should NOT be considered as a correction for this customer concern. Check the vehicle history to determine if the vehicle is returning for a second fuel system repair for this condition. If the fuel system has been repaired for this condition previously, then inform the customer that an alternate fix is available. A new MFI fuel system has been developed that will back service the CSFI fuel system. The MFI fuel system eliminates the CSFI poppet valve ball and seat. The CSFI fuel system will need to be replaced as a unit. Refer to Central SFI to MFI Conversion instructions in this bulletin. Notice: Individual CSFI injectors can not be replaced with MFI injectors. The entire CSFI fuel meter body will need to be replaced. The bracket used to retain the injectors in the fuel meter body is different between the CSFI and MFI unit. The unit may not seal if you mix injectors. Severe engine damage could result. Cleaning the CSFI injectors is the preferred repair. The CSFI unit should not be replaced until cleaning has been attempted. If the vehicle should return for the same repair, then the CSFI unit can be replaced with an MFI unit. If the vehicle is out of warranty, the customer should be given the option of which fix to pursue. Important: "GM of Canada" dealers require District Service Manager approval prior to replacing the CSFI unit with a MFI unit under warranty. The first step of this process is to use the J 41413 Evap Pressure/Purge Station, in conjunction with the J 44466-10 pressure regulator/hose assembly, to provide the required high pressure (150 psi) source to perform the unsticking procedure. The J 39021 fuel injector tester and accessories provide the means to "energize" the injector. Some later model-year vehicles may utilize the Tech 2(R) to "energize" the injectors. The second step of this process is to run the engine on a solution of 10% Top Engine Cleaner and 90% gasoline. This will effectively clean any deposits from the ball and seats of the poppets. It is very important that the engine fuel system is separated from the vehicle fuel system. Top Engine Cleaner may have detrimental effects on the fuel pump. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6029 Parts Information Cleaning Procedure Parts CSFI to MFI Conversion Parts Parts are currently available from GMSPO. Warranty Information Important: Some California vehicles may be covered by Special Policy 99066E if built with California Emissions RPO YF5. If the vehicle is covered by the special policy, then that warranty information should be used. For vehicles repaired under warranty, use information contained in Special Policy 99066E. Information This procedure should be performed before any attempt to convert the fuel system to MFI. S/T and C/K Truck 1. Loosen the fuel filler cap to relieve vapor pressure in the fuel tank. 2. Remove the Positive Crankcase Ventilation (PCV) clean air tube from the air inlet tube and set aside. 3. Remove the bonnet and inlet tube from the throttle body. 4. Remove the brake booster vacuum hose and connector from the intake manifold. 5. Remove the electrical connector from the CSFI fuel metering body. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6030 6. Remove ignition wires 1, 3, 5, and 7 from the distributor cap. 7. Remove the fuel line bolt (4) at the rear of the intake manifold. 8. Relieve the fuel system pressure at the service fitting on the fuel line. Use a shop towel to contain any fuel that may exit the service fitting. 9. Remove the nuts (1) and clamp (2) from the fuel pipe. 10. Remove the fuel pipes from the metering body. Be careful not to disturb the O-rings, washer, and spacer in the metering body. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6031 11. Install the J 44466-12 (2) and the J 44466-13 (1) to the metering body and tighten. Make sure that the fuel pipe 0-rings, washer, and spacers are present and in their proper position. 12. Install the J 44466-11 (4), clamp (2), and J 44466-13 (1) to the fuel pipe and tighten. 13. Obtain the J 41413, close the valve (2) on the tank, and remove the regulator assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6032 14. Install the J 44466-10 (5) to the J 41413 tank (3). The J 44466-10 regulator is preset to 150 psi. 15. Connect the J 44466-10 hose (1) to the J 44466-12 (3). 16. Install the J 39021 Injector/Coil Balance Tester, the J 39021-210 Injector Tester Adapter Box, and J 39021-301 V6 Fuel Injector Test Adapter (1) or J 39021-302 V8 Fuel Injector Test Adapter to the metering body electrical connector. 17. Adjust the amperage selector switch on J 39021 to 0.5 amps. 18. Open the valve (2) on the tank (3). 19. Open the valve (4) on the J 44466-10 to pressurize the fuel system. The minimum pressure required on the gauge (6) is 150 psi. If 150 psi is not obtained, the tank (3) must be refilled prior to performing this procedure. 20. Close the valve (4) on the J 44466-10. 21. Energize one injector using the J 39021. Observe a pressure drop on the gauge (6) and verity the injector/poppet valve operation. An injector/poppet that is "stuck" and not operational will have no pressure drop on the gauge. It an injector remains "stuck", repeat the procedure multiple times (as required) until the injector is operational. 22. Repeat Steps 19, 20 and 21 for each individual injector to verify that all injector/poppet valve assemblies are "unstuck" and functional. 23. Shut off pressure valve (2) on the tank (3) of the J 41413. 24. Bleed off the pressure at the J 44466-10. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6033 25. Disconnect and remove the J 44466-10 (5) from the J 44466-12, and the J 41413. 26. Remove the J 39021-301 or J 39021-302, J 39021-210, and J 39021 from the metering body. 27. Install the vehicle electrical connector to the metering body. 28. Install the brake booster vacuum hose and connector to the intake manifold. 29. Install ignition wires 1, 3, 5, and 7 to the distributor cap. 30. Install the air inlet bonnet 10 the throttle body, tighten the wing-nut. 31. Install the PCV fresh air tube to the air inlet tube. 32. Obtain J 35800-A (2). Make sure the valve at the bottom of the canister (3) is closed. 33. Remove the canister top and add 24 ml (0.8 fl. oz.) Top Engine Cleaner, P/N 1050002 (Canada P/N 992872), to the canister. 34. Fill the remainder of the canister with regular unleaded gasoline and install the canister top. 35. Suspend J 35800-A from a convenient underhood location. 36. Connect the hose from J 35800-A to the service port on the J 44466-12 37. Open the valve (3) at the bottom of J 35800-A. 38. Connect a "shop air" source to the fitting at the top of J 35800-A and adjust the regulator (1) to 75 psi. 39. Start the vehicle. It may be necessary to re-adjust the J 35800-A pressure regulator to maintain 75 psi. 40. Let the vehicle run at idle until the canister is empty and the vehicle stalls. 41. Remove the shop air supply from J 35800-A. 42. Depressurize the J 35800-A. 43. Disconnect the J 35800-A hose from the J 44466-12. 44. Remove the PCV clean air tube from the air inlet tube and set aside. 45. Remove the bonnet from the throttle body, and set aside. 46. Remove ignition wires 1, 3, 5, and 7 from the distributor cap. 47. Remove the brake booster vacuum hose and connector from the intake manifold. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6034 48. Bleed the residual pressure from the J 44466-12. 49. Remove J 44466-13 (1) and J 44466-12 (2) from the metering body. 50. Remove J 44466-13 (1), clamp (2), and J 44466-11 (4), from the fuel pipe (3). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6035 51. Install the fuel pipe (3) to the metering body. Make sure that all of the 0-rings (6 and 8), washers (7), and spacers (5) are present and in their proper position. 52. Install the clamp (2) and nuts (1). Tighten Tighten the nuts to 3 N.m (27 lb in). 53. Apply threadlock, P/N 12345382, or equivalent to the threads of the fuel pipe bolt (4). Install the bolt. Tighten Tighten the fuel pipe bolt to 6 N.m (53 lb in). 54. Install the brake booster vacuum hose and connector to the intake manifold. 55. Install the bonnet and air inlet tube to the throttle body. 56. Install the PCV fresh air tube to the inlet duct. 57. Install ignition wires 1, 3, 5 (7) to the distributor cap. 58. Add one (1) ounce of Port Fuel Injector Cleaner, P/N 12345104 (Canada P/N 10953467), to the vehicle fuel tank for each gallon of gasoline estimated to be in the tank. Instruct the customer to add the remainder of the bottle of Port Fuel Injector Cleaner to the vehicle fuel tank at the next fill-up. Further recommend that Port Fuel Injector Cleaner be added to the fuel tank every 3000 miles (4800 km) particularly if the vehicle is not started and driven every day. Inform the customer that the Port Fuel Injector Cleaner is not to be used at every fill up but may be reapplied every 3000 miles (4800 km). 59. Tighten the fuel tank filler cap. 60. Start the vehicle and check for fuel leaks. 61. Using the Tech 2(R) scan tool, check for any stored Powertrain DTC codes. Clear codes as required. 62. Disconnect the Tech 2(R) Scan tool. 63. Advise the customer to change brands of fuel. M/L, G Van and P Truck 1. Loosen the fuel tank filler cap to relieve fuel tank vapor pressure. 2. Remove the engine cover. 3. Remove ignition wires 1 3, 5, and 7 from the distributor cap. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6036 4. Remove the vacuum brake booster hose and connector from the intake manifold. 5. Remove the fuel pipe bolt (4) at the rear of the intake manifold. 6. Relieve the fuel system pressure at the service fitting on the fuel pipe. Use a shop towel to contain any fuel that may exit the service fitting. 7. Disconnect the fuel pipes (3) at the rear of intake manifold (1). 8. Remove the nuts (1) and clamp (2) from the fuel pipe. 9. Remove the fuel pipes from the metering body. Be careful not to disturb the 0-rings, washer, and spacer in the metering body. 10. Remove the electrical connector from metering body. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6037 11. Install J 44466-12 (2) and J 44466-13 (1) to the fuel metering body and tighten. Make sure that the fuel pipe 0-rings, washer, and spacers are present and in their proper position. 12. Install J 44466-01 (1) to the vehicle fuel lines. 13. Obtain the J 41413, close the valve (2) on the tank, and remove the regulator assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6038 14. Install the J 44466-10 (5) to the J 41413 tank (3). The J 44466-10 regulator is preset to 150 psi. The minimum pressure required on the gauge (6) is 150 psi. If 150 psi is not obtained, the tank must be refilled prior to performing this procedure. 15. Connect the J 44466-10 hose to the J 44466-12. 16. Install J 39021 Injector/Coil Balance Tester, the J 39021-210 Injector Tester Adapter Box, and J 39021-301 V6 Fuel Injector Test Adapter or J 39021-302 V8 Fuel Injector Test Adapter to metering body electrical connector. 17. Adjust the amperage selector switch on J 39021 to 0.5 amps. 18. Open the valve (2) on the tank (3). 19. Open the valve (4) on the J 44466-10 to pressurize the fuel system. 20. Close the valve (4) on the J 44466-10. 21. Energize one injector using the J 39021. Observe a pressure drop on the gauge (6) and verify the injector/poppet valve operation. An injector/poppet that is "stuck" and not operational will have no pressure drop on the gauge. If an injector remains "stuck", repeat the procedure multiple times (as required) until the injector is operational. 22. Repeat steps 19, 20, and 21, for each individual injector to verify that all injector/poppet valve assemblies are "unstuck" and functional. 23. Shut off the pressure valve (2) on the tank (3) of the J 41413. 24. Bleed off pressure at J 44466-10. 25. Disconnect and remove the J 44466-10 hose from the J 44466-12 and the J 41413. 26. Remove the J 39021-301 or J 39021-210, J 39021-210, and J 39021 from the metering body. 27. Install the vehicle electrical connector to the metering body. 28. Install ignition wires 1, 3, 5, and 7 to the distributor cap. 29. Install the vacuum brake booster hose and connector to the intake manifold. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6039 30. Obtain J 35800-A (2). Make sure the valve (3) at the bottom of the canister is closed. 31. Remove the canister top and add 24 ml (0.8 fl. oz.) Top Engine Cleaner, P/N 1050002 (Canada P/N 992872), to the canister. 32. Fill the remainder of the canister with regular unleaded gasoline and install the canister top. 33. Suspend the J 35800-A in a convenient location. 34. Connect the hose from the J 35800-A to the service port on the J 44466-12. 35. Open the valve (3) at the bottom of J 35800-A. 36. Connect a "shop air" source to the fitting at the top of J 35800-A and adjust the regulator (1) to 75 psi. 37. Start the vehicle. It may be necessary to re-adjust the J 35800-A pressure regulator to maintain 75 psi. 38. Let the vehicle run at idle until the canister is empty and the vehicle stalls. 39. Remove the shop air supply from J 35800-A. 40. Depressurize the J 35800-A. 41. Disconnect the J 35800-A hose from the J 44466-12. 42. Remove the vacuum brake booster hose and connector from the intake manifold. 43. Remove ignition wires 1, 3, 5, and 7 from the distributor cap. 44. Bleed the residual pressure from J 44466-12. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6040 45. Remove the J 44466-13 (1) and J 44466-12 (2) from the metering body. 46. Remove the J 44466-01 (1) from the vehicle fuel lines. 47. Install the fuel pipe (3) to the metering body. Make sure the all of the 0-rings (6 and 8), washers (7), and spacers (5) are present and in their proper position. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6041 48. Install the clamp (2) and nuts (1). Tighten Tighten the nuts to 3 N.m (27 lb in). 49. Inspect the 0-rings at the fuel pipe-to-vehicle lines (1). Replace as necessary. Tighten Tighten the fuel line nuts to 30 N.m (22 lb ft). 50. Apply threadlock, P/N 12345382, or equivalent to the threads of the fuel pipe bolt. Install the bolt. Tighten Tighten the fuel pipe bolt to 6 N.m (53 lb in). 51. Install ignition wires 1, 3, 5, and 7 to the distributor cap. 52. Install the vacuum brake booster hose and connector to the intake manifold. 53. Add one (1) ounce of Port Fuel Injector Cleaner, P/N 12345104 (Canada P/N 10953467), to the vehicle fuel tank for each gallon of gasoline estimated to be in the tank. Instruct the customer to add the remainder of the bottle of Port Fuel Injector Cleaner to the vehicle fuel tank at the next fill-up. Further recommend that Port Fuel Injector Cleaner be added to the fuel tank every 3000 miles (4800 km) particularly if the vehicle is not started and driven every day. Inform the customer that the Port Fuel Injector Cleaner is not to be used at every fill up but may be reapplied every 3000 miles (4800 km). 54. Tighten the fuel tank filler cap. 55. Start the engine and check for fuel leaks. 56. Use the Tech 2(R) Scan Tool to check for any stored Powertrain DTC codes. Clear codes as required. 57. Disconnect the Tech 2(R) Scan tool. 58. Install the engine cover. 59. Advise customer to change brands of fuel. Central SFI to MFI Conversion Instructions This procedure outlines the steps required to replace the existing Central SFI Fuel System with a new MFI (Multiport Flexible Injection) Fuel System. Be sure to use the appropriate year and model Service Manual for proper disassembly and re-assembly procedure(s). Important: Cleaning the CSFI injectors is the preferred repair. The CSFI unit should not be replaced until cleaning has been attempted. If the vehicle should Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6042 return for the same repair, then the CSFI unit can be replaced with a MFI unit. If the vehicle is out of warranty, the customer should be given the option of which fix to pursue. V6 Engines 1. Remove Upper Intake Manifold plenum and SFI Fuel Meter Body according to Service Manual Procedures. 2. Remove the Fuel Meter Body bracket and discard. Install the new bracket as shown in Figure 1. 3. Position Fuel Tubes of MFI Fuel Meter Body as shown in Figure 2. Tubes must be oriented away from the fuel pressure regulator end of the fuel meter body. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6043 Notice: The number 3 Fuel Tube must be positioned behind the number 1 Fuel Tube to eliminate interference with the Upper Intake Manifold plenum when installed. See Figure 2. 4. Insert the MFI Fuel Meter Body into the Fuel Meter Body Bracket on the Lower Intake Manifold being careful not to bind the Fuel Tubes. Make sure that the number three Fuel Tube is routed in behind number 1 and 5 Fuel Tubes as shown in Figure 2. Push down firmly on the fuel meter body locking it into the bracket. Notice: Use caution when inserting injectors into lower intake manifold to be sure the correct injector is being placed into the correct hole. Injectors should not be removed once they have been installed. Removal of injectors from the intake manifold may cause damage to the retaining lugs on the injector. Important: The Injector holes are numbered on the Lower Intake Manifold. The injectors are numbered on the side of the Fuel Meter Body. 5. Insert the number 3 injector into the correct Injector hole in the Lower Intake Manifold first. Install the number 5 injector next and then number 1. This sequence must be followed correctly to prevent interference of the Fuel Tubes. Injectors 2, 4, and 6 are then installed. 6. Insure that the electrical connectors of the injectors are positioned so that they do not interfere with each other and are pointing towards the center of the Intake Manifold. If necessary, rotate the electrical connectors inboard. Notice: Lack of lubrication will make installation of the Upper Intake Manifold plenum difficult and may cause damage to the 0-ring. 7. Lubricate the Fuel Meter Body Upper Manifold 0-ring (orange in color) with clean engine oil. 8. Inspect the Upper Intake Manifold plenum gasket and replace if necessary. Reinstall the Upper Intake Manifold plenum following the procedures outlined in the Service Manual. Important: Lubricate the Fuel Inlet and Return Lines with clean engine oil before inserting them into the Fuel Meter Body. Make sure that the Fuel Line Retaining Bracket is properly oriented with the tabs down. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6044 V8 Engines This procedure outlines the steps required to replace the existing Central SFI Fuel System with a new MFI (Multipoint Flexible Injection) Fuel System. Be sure to use the appropriate year and model Service Manual for proper disassembly and re-assembly procedure(s). 1. Remove Upper Intake Manifold plenum and SFI Fuel Meter Body according to Service Manual Procedures. 2. Remove the Fuel Meter Body bracket and discard. Install the new bracket. 3. Position Fuel Tubes of MFI Fuel Meter Body as shown in Figure 3. Fuel tubes 1, 3, 5, and 7 are oriented toward the fuel inlet side of the fuel meter body. Fuel tubes 2, 4, 6, and 8 are oriented toward the fuel pressure regulator side if the fuel meter body. 4. Insert the MFI Fuel Meter Body into the Fuel Meter Body Bracket on the Lower Intake Manifold being careful not to bind the Fuel Tubes. Push down firmly on the fuel meter body until the tabs snap into the bracket locking the fuel meter body in place. 5. Orient the fuel tubes to coincide with their corresponding cylinder. The fuel tubes are numbered on the side of the fuel meter body and the corresponding cylinder number is cast in the intake manifold. Notice: Use caution when inserting injectors into lower intake manifold to be sure the correct injector is being placed into the correct hole. Injectors should not be removed once they have been installed. Removal of injectors from the intake manifold may cause damage to the retaining lugs on the injector. Important: The Injector holes are numbered on the Lower Intake Manifold. The injectors are numbered on the side of the Fuel Meter Body. 6. Insert the fuel tubes into their corresponding holes in the intake manifold. Install tubes for cylinders 1, 3, 6 and 8 making sure that the injector electrical connectors are facing in toward the center of the manifold. 7. Insert fuel tubes for cylinders 2, 4, 5, and 7 in the same manner. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 00-06-04-003B > Feb > 03 > Fuel System - MIL ON/Rough Idle on Start-Up > Page 6045 Important: When installing fuel tubes, it is important that the tubes are oriented properly to provide minimal interference when installing the upper intake manifold plenum. Intake holes for cylinders 2, 4, 5, and 7 are closer to the fuel meter body. It is necessary to cross tube 5 over tube 7 and tube 4 over tube 2 as shown in Figure 4. Notice: Lack of lubrication will make installation of the Upper Intake Manifold plenum difficult and may cause damage to the 0-ring. 8. Lubricate the Fuel Meter Body Upper Manifold 0-ring (blue in color) with clean engine oil. 9. Inspect Upper Intake Manifold Gasket and replace if necessary. Reinstall the Upper Intake Manifold plenum following the procedures in the Service Manual. Important: Lubricate the Fuel Inlet and Return Lines with clean engine oil before inserting them in the of the Fuel Meter Body. Make sure that Fuel Line Retaining Bracket is properly oriented with the tabs down. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 99-06-04-006 > Feb > 99 > Fuel Correct Solvent for CSFI Poppet Cleaning Fuel Injector: All Technical Service Bulletins Fuel - Correct Solvent for CSFI Poppet Cleaning File In Section: 06 - Engine Bulletin No.: 99-06-04-006 Date: February, 1999 INFORMATION Subject: Correct Solvent for CSFI Poppet Cleaning Procedure Models: 1999 Cadillac Escalade 1996-99 Chevrolet, GMC S/T, M/L, C/K, G, P Models 1996-99 Oldsmobile Bravada with 4.3L, 5.0L or 5.7L Engine (VINs X, W, M, R - RPOs LF6, L35, L3O, L31) and All Transmission Types Some technicians, when servicing 1996 and newer Truck CSFI (Central Sequential Fuel Injection) fuel systems (ref. Corporate Bulletin 87-65-07A), may be using an incorrect solvent when attempting to clean CSFI poppet valves. Important: The ONLY solvent that will have any effect on the deposits occurring on poppet valves is: "PORT FUEL INJECTOR GASOLINE DETERGENT" (P/N 12345104) (IN CANADA USE P/N 12345515). The use of Goodwrench "Fuel Injector Cleaner" (P/N 12346291), or any other "Fuel Injector Cleaner" is completely non-effective, and not appropriate for this concern. Parts Information Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 616316 > Feb > 97 > Fuel System - Injection Balance Test Procedure Revised Fuel Injector: All Technical Service Bulletins Fuel System - Injection Balance Test Procedure Revised File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-63-16 Date: February, 1997 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Injector Balance Test Procedure Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7, 7.4L Engine (VINs W, X, M, R, J - RPOs L35, LF6, L30, L31, L29) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 616316 > Feb > 97 > Fuel System - Injection Balance Test Procedure Revised > Page 6054 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 616316 > Feb > 97 > Fuel System - Injection Balance Test Procedure Revised > Page 6055 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 616316 > Feb > 97 > Fuel System - Injection Balance Test Procedure Revised > Page 6056 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 616316 > Feb > 97 > Fuel System - Injection Balance Test Procedure Revised > Page 6057 This bulletin is being issued to inform technicians of a revision to the Injector Balance Test. This revised procedure will help the technician to use the Injector Balance Test with greater clarity and accuracy. Please use this revised procedure of the Injector Balance Test for the following model years: ^ 1996-97 S/T Truck V-6 ^ 1996-97 M/L Van V-6 ^ 1996-97 G Van, V-6, V-8 ^ 1996-97 C/K Truck, V-6, V-8 ^ 1996-97 P Truck, V-6, V-8 Technicians diagnosing vehicles with misfire DTCs (P0300-P0308) must perform the Injector Coil Test and the Injector Balance Test prior to injector replacement. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 99066F > Mar > 03 > Campaign Fuel Injector Sticking Closed Fuel Injector: All Technical Service Bulletins Campaign - Fuel Injector Sticking Closed File In Section: 06-Engine Emissions Bulletin No.: 99066F Date: March, 2003 SPECIAL POLICY SUBJECT: 99066F - SPECIAL POLICY ADJUSTMENT - SEQUENTIAL CENTRAL PORT FUEL INJECTION (SCPI) FAILURES IN CALIFORNIA ONLY (YF5 EMISSION EQUIPPED) MODELS: CERTAIN 1996, 1997, 1998, 1999, 2000, 2001, 2002 S/T, M/L, C/K, G, P, W4/NPR TRUCKS AND 2003 NPR TRUCKS EQUIPPED WITH 4.3L (RPO L35 - VIN CODE W OR RPO LF6 - VIN CODE X), 5.0L (RPO L30 - VIN CODE M) OR 5.7L (RPO L31 - VIN CODE R) ENGINE AND CALIFORNIA EMISSION EQUIPPED (RPO YF5) This bulletin is being revised to add the 2002 and 2003 model years to the SCPI Special Policy on certain S/T, M/L, C/K, G, P and W4/NPR truck models. Please discard Special Policy Bulletin Number 99066E, dated February, 2003. CONDITION Some customers of 1996, 1997, 1998, 1999, 2000, 2001, 2002 model year S/T, M/L, C/K, G, P, W4/NPR trucks and 2003 NPR trucks, that are registered in California, equipped with 4.3L (RPO L35 and VIN Code W, or RPO LF6 and VIN Code X), 5.0L (RPO L30 and VIN Code M) or 5.7L (RPO L31 and VIN Code R) engine, and California emissions (RPO YF5), may experience a "Service Engine Soon" light, misfire, rough idle or hard start due to a deposit build-up on the Sequential Central Port Fuel Injector (SCPI) poppet valve(s). The deposit build-up may cause injector poppets to stick closed. Certain fuels have been found to interact with the SCPI system to cause the deposits. SPECIAL POLICY ADJUSTMENT This special policy covers the SCPI failure condition described above for a period of ten (10) years or 200,000 miles, whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership. The repairs will be made at no charge to the owner. This special policy applies ONLY to repairs requiring SCPI system servicing, injector cleaning and/or MFI assembly replacement of the SCPI system. The customer should not be charged for performing a system check when it is determined that the SCPI system is not the cause of a customer complaint (labor operation T5532 is provided to submit claims for such system checks). Any additional necessary diagnosis and repairs that are not related to the SCPI condition are not covered by this special policy. The customer should be informed that any further service that is not covered by new vehicle warranty will not be covered by this policy. VEHICLES INVOLVED Involved are certain 1996,1997,1998,1999, 2000, 2001, 2002 S/T, M/L, C/K, G, P, W4/NPR and 2003 NPR model vehicles, registered in California, equipped with 4.3L (RPO L35 - VIN Code W, or RPO LF6 - VIN Code X), 5.0L (RPO L30 - VIN Code M) or 5.7L (RPO L31 - VIN Code R) engine; and California emissions (RPO YF5). This Special Policy covers all vehicles within these model years, with these engine and emissions RPO's. PARTS INFORMATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 99066F > Mar > 03 > Campaign Fuel Injector Sticking Closed > Page 6067 Parts required to complete this special policy are to be obtained from General Motors Service Parts Operations (GMSPO). Please refer to your "involved vehicles listing" prior to ordering parts. Normal orders should be placed on a DRO Daily Replenishment Order. In an emergency, parts should be ordered on a CSO = Customer Special Order. IMPORTANT: Isuzu Parts Ordering: In order to comply with the 10-digit Isuzu part numbering system, Isuzu dealers must add an "8" to the beginning and a "0" to the end of the listed 8-digit part numbers when ordering parts through AIPDN. CUSTOMER NOTIFICATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 99066F > Mar > 03 > Campaign Fuel Injector Sticking Closed > Page 6068 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 99066F > Mar > 03 > Campaign Fuel Injector Sticking Closed > Page 6069 Customers will be notified of this special policy on their vehicles by General Motors (see copy of typical customer letter included with this bulletin - actual divisional letter may vary slightly). SERVICE PROCEDURE System Check: Use strategy-based diagnoses listed in the front of the Driveability and Emissions section of the service manual. If the SCPI system is operating properly, inform the customer that the vehicle does not have the condition listed in the owner letter. If poor driveability conditions persist, inform the customer that any further diagnosis and repairs will be at their expense if the vehicle is outside the parameters of the new vehicle warranty. SCPI Injector Cleaning Procedure: If diagnosis leads to sticking poppet nozzles, use the service procedure from Service Bulletin 00-06-04-003B to clean the SCPI poppet nozzles. Please note that the service bulletin term for SCPI is Central Sequential Fuel Injection (CSFI), but is referring to the same fuel system assembly. If the poppet nozzles have previously been cleaned and the sticking condition has reoccurred, refer to the correction paragraph below. SCPI Fuel Tank Fill Pipe Assembly for 1997-99 M/L Van and 1999 - some 2000 C/K Truck: with 4.3L, 5.0L, 5.7L engines and built prior to listed VIN/Production dates on Service Bulletin 00-06-04-018: If diagnosis leads to sticking poppet nozzles on these models, use the service procedure from Service Bulletin 00-06-04-018 to replace the fuel tank fill pipe assembly, if this procedure has not been performed previously. Previous service procedure can be verified by checking GMVIS for Labor Operation L1065 on "M/L" trucks with replacement part number 15050573; or Labor Operation L1065 on "C/K" trucks with replacement part numbers 15747585 or 15747588. Correction: If, after cleaning the SCPI poppet nozzles, the normal service manual diagnosis still indicates that the SCPI is the cause of the customer complaint, or if the injectors have previously been cleaned and the vehicle has again experienced sticking poppet nozzles, refer to Service Bulletin 00-06-04-003B and replace the SCPI fuel assembly with the MFI fuel assembly. Please note that the service bulletin term for SCPI is Central Sequential Fuel Injection (CSFI), but is referring to the same fuel system assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 99066F > Mar > 03 > Campaign Fuel Injector Sticking Closed > Page 6070 CLAIM INFORMATION For vehicles repaired under this special policy, submit a claim with the information indicated. CUSTOMER REIMBURSEMENT Customer requests for reimbursement are for any previously paid repairs to, or replacement of, the Sequential Central Port Fuel Injection (SCPI) system. Repairs must have occurred within 10 years of the date the vehicle was originally placed in service, or 200,000 miles, whichever occurs first. The requests are to be submitted within two (2) years of the date on which the repair was paid or within two (2) years of the date of this Special Policy Bulletin, whichever is greater. When a customer requests reimbursement, they must provide the following: - Proof of ownership at time of repair. - Original paid receipt confirming the amount of unreimbursed repair expense(s) (including Service Contract deductibles), a description of the repair, and the person or entity performing the repair. Customers from the State of California, must submit requests for reimbursement directly to (Divisions) per instructions in the owner letter. If the work was done by someone other than a GM dealership, the amount of reimbursement will be limited to the amount that the repair would have cost GM to have it completed by a GM dealership. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 616316 > Feb > 97 > Fuel System - Injection Balance Test Procedure Revised > Page 6079 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 616316 > Feb > 97 > Fuel System - Injection Balance Test Procedure Revised > Page 6080 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 616316 > Feb > 97 > Fuel System - Injection Balance Test Procedure Revised > Page 6081 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Injector: > 616316 > Feb > 97 > Fuel System - Injection Balance Test Procedure Revised > Page 6082 This bulletin is being issued to inform technicians of a revision to the Injector Balance Test. This revised procedure will help the technician to use the Injector Balance Test with greater clarity and accuracy. Please use this revised procedure of the Injector Balance Test for the following model years: ^ 1996-97 S/T Truck V-6 ^ 1996-97 M/L Van V-6 ^ 1996-97 G Van, V-6, V-8 ^ 1996-97 C/K Truck, V-6, V-8 ^ 1996-97 P Truck, V-6, V-8 Technicians diagnosing vehicles with misfire DTCs (P0300-P0308) must perform the Injector Coil Test and the Injector Balance Test prior to injector replacement. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Page 6083 Fuel Injector: Specifications Lower hold down plate and nut ............................................................................................................ ................................................... 3.0 N.m (27 lb. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Technical Service Bulletins > Page 6084 Engine Side, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions Fuel Injector: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6087 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6088 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6089 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6090 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6091 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6092 Fuel Injector: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6093 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6094 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6095 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6096 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6097 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6098 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6099 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6100 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6101 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6102 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6103 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6104 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6105 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6106 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6107 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6108 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6109 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6110 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6111 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6112 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6113 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6114 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6115 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6116 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6117 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6118 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6119 Fuel Injectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Diagram Information and Instructions > Page 6120 Fuel Injectors (Under 8600 GVW) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Diagrams > Page 6121 Fuel Injector: Description and Operation Injector And Poppet Nozzle Assembly DESCRIPTION Each fuel injector assembly is a solenoid-operated device, controlled by the VCM. The fuel injector assembly meters the pressurized fuel through a poppet nozzle (5) to a single engine cylinder. The VCM energizes the injector solenoid, which opens an armature valve (3), allowing fuel to flow past the ball valve and through a fuel tube (1) to the poppet nozzle. An increase in fuel pressure causes the poppet nozzle ball to open from its seat against the extension spring force. This allows the fuel to flow from the nozzle (at approximately 280 kPa (40 psi)). De-energizing the injector solenoid (4) closes the armature. De-energizing also reduces the fuel pressure acting on the poppet nozzle ball. The extension spring closes the ball to the seat (2). The extension spring also checks the pressure between the ball and seat and the injector armature and fuel tube shutoff. An injector poppet nozzle that is stuck partly open would cause a loss of pressure after the engine shut down. Consequently, the driver would notice long cranking times on some engines. Dieseling could also occur because the fuel injector could deliver some fuel to the engine after the driver turns the ignition to OFF. These components are diagnosed in The Injector Balance Test and The Injector Coil Test. Refer to Fuel Injector Balance Test. Refer to System Diagnosis / Diagnostic Tables. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Service and Repair > Removal and Installation Fuel Injector: Service and Repair Removal and Installation REMOVAL PROCEDURE CAUTION: Use care in removing the fuel injectors to prevent damage to the electrical connector terminals, the injector filter, and the fuel nozzle. NOTE: The fuel injector is serviced as a complete assembly only. CAUTION: Also since the injectors are electrical components, these injectors should not be immersed in any type of liquid solvent or cleaner as damage may occur. 1. Disconnect the negative battery cable. 2. Relieve the fuel system pressure. Refer to Fuel Pressure Relief Procedure. See: Service and Repair 3. Remove the Upper Manifold Assembly. Refer to Engine Mechanical. 4. Remove the Fuel Meter Body Assembly. Refer to Fuel Meter Body Assembly. See: Throttle Body/Service and Repair INSTALLATION PROCEDURE 1. Install the fuel meter body assembly. Refer to Fuel Meter Body Assembly. See: Throttle Body/Service and Repair 2. Install the upper manifold assembly. Refer to Engine Mechanical. 3. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Injector > Component Information > Service and Repair > Removal and Installation > Page 6124 Fuel Injector: Service and Repair Disassemble and Assemble DISASSEMBLE PROCEDURE 1. Disassemble the lower hold down plate and nuts. 2. While pulling the poppet nozzle tube downward, push with small screwdriver down between the injector terminals until the injector is removed. ASSEMBLE PROCEDURE NOTE: Each injector is calibrated for a specific flow rate. When replacing fuel injectors, order the correct injector for the application being serviced. 1. Lubricate the new injector O-ring seals with clean engine oil. 2. Install on the injector assembly. 3. Assemble the Central SFI fuel injector assembly into the fuel meter body injector socket. 4. Assemble the lower hold down plate and nuts. Tighten Tighten the nuts to 3.0 Nm (27 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Line Coupler > Component Information > Service and Repair Fuel Line Coupler: Service and Repair REMOVAL PROCEDURE 1. Grasp both sides of the fitting. Twist the female connector 1/4 turn in each direction to loosen any dirt within the fitting. WARNING: Wear safety glasses when using compressed air because flying dirt particles may cause eye Injury. 2. Using compressed air, blow dirt out of the fitting. 3. Choose the correct tool from J37O88 tool set for size of the fitting. Insert the tool into the female connector, then push inward to release the locking tabs. 4. Pull the connection apart. CLEANING AND INSPECTION CAUTION: If it is necessary to remove rust or burrs from a fuel pipe, use emery cloth in a radial motion with the fuel pipe end in order to prevent damage to the O-ring sealing surface. Using a clean shop towel, wipe off the male pipe end. Inspect both ends of the fitting for dirt and burrs. Clean or replace components/assemblies as required. INSTALLATION PROCEDURE WARNING: To Reduce the Risk of Fire and Personal Injury: Before connecting the fluing, always apply a few drops of clean engine oil to the male pipe end. This will ensure proper reconnection and prevent a possible fuel leak. (During normal operation, the O-rings located in the female connector will swell and may prevent proper reconnection if not lubricated. 1. Apply a few drops of clean engine oil to the male pipe end. 2. Push both sides of the fitting together to cause the retaining tabs/fingers to snap into place. 3. Once installed, pull on both sides of the fitting to make sure the connection is secure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pressure Regulator > Component Information > Locations Fuel Pressure Regulator: Locations Fuel Pressure Regulator Assembly, Located In Fuel Meter Assy Inside Intake Manifold Fuel Supply System Legend (1) Fuel Pressure Regulator Assembly. (2) Regulator Retainer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pressure Regulator > Component Information > Locations > Page 6131 Fuel Pressure Regulator: Description and Operation Fuel Pressure Regulator Assembly, Located In Fuel Meter Assy Inside Intake Manifold The fuel pressure regulator (1) is a diaphragm-operated cartridge relief valve with the fuel pump pressure on one side and the regulator spring pressure and intake manifold vacuum on the other. A retainer (2) holds the fuel pressure regulator. The regulator's function is to maintain a constant pressure differential across the injectors at all times. The pressure regulator compensates for engine load by increasing the fuel pressure as engine vacuum drops. With the ignition ON leaving the engine off (zero vacuum), the fuel pressure at the pressure test connection should be 415-455 kPa (6O-66 psi). If the pressure is too low, poor performance could result. If the pressure is too high, excessive odor may result. The Fuel System Diagnosis has information on diagnosing fuel pressure conditions. Refer to Fuel System Pressure Test. Refer to System Diagnosis / Diagnostic Tables. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pressure Regulator > Component Information > Locations > Page 6132 Fuel Pressure Regulator: Service and Repair REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Relieve fuel system pressure. Refer to Fuel Pressure Relief Procedure. See: Service and Repair 3. Remove the upper manifold assembly. Refer to Engine Mechanical. DISASSEMBLE PROCEDURE 1. Disassemble the fuel pressure regulator snap ring retainer. 2. Disassemble the regulator assembly and the O-rings. 3. Discard the O-rings. NOTE: If the fuel pressure regulator is to be reinstalled, inspect the filter screen (if equipped) for contamination. If contaminated, remove. Discard the filter screen. ASSEMBLE PROCEDURE 1. Lubricate the new O-rings with clean engine oil. 2. Install as an assembly, backup O-ring, large O-ring, filter and small O-ring. 3. Assemble the regulator with vacuum tube pointing down and snap ring retainer. INSTALLATION PROCEDURE 1. Install the upper manifold assembly. Refer to Engine Mechanical. 2. Disconnect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pressure Pulsation Damper > Component Information > Technical Service Bulletins > Customer Interest: > 66-63-09 > Apr > 97 > Engine Hard Start or No Start Fuel Pressure Pulsation Damper: Customer Interest Engine - Hard Start or No Start File In Section: 6E - Engine Fuel & Emission Bulletin No.: 66-63-09 Date: April, 1997 Subject: Engine Hard Start or No Start (Replace Fuel Pump Pulsator) Models: 1992-96 Chevrolet and GMC Trucks 1992-96 Oldsmobile Bravada with Gasoline Engines Condition Some owners may report their engine is hard to start or will not start. Cause The fuel delivery system may have low or no pressure due to a ruptured fuel pump pulsator The pulsator is the flexible connector between the fuel pump and the metal fuel line in the tank. This rupture appears as a tear in the pulsator openings and is the result of exposure to gasoline containing a high percentage of ethanol. Correction Follow the Strategy Based Diagnostic Steps for the reported symptoms. If diagnosis reveals low or no fuel system pressure, and the fuel pump is identified as a possible cause, follow the service procedure for, On-Vehicle Service, Fuel Pump, in the appropriate Truck Service Manual. Before replacing the fuel pump, inspect the pulsator for signs of tears or leaks It the pulsator is damaged, replace it with P/N 25175836 and re-test the fuel system for normal pressure. This pulsator is made of Viton which is resistant to Ethanol content fuels. P/N 25175836 replaces P/N 25094266 for trucks. This change will appear in GMSPO parts catalogs as they are revised. Part Information P/N Description QTY 25175836 Damper Asm - Fuel Pulsator 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Labor Op Description Labor Time J 5590 Pump, Fuel R&R; Use Published Labor Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pressure Pulsation Damper > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 66-63-09 > Apr > 97 > Engine - Hard Start or No Start Fuel Pressure Pulsation Damper: All Technical Service Bulletins Engine - Hard Start or No Start File In Section: 6E - Engine Fuel & Emission Bulletin No.: 66-63-09 Date: April, 1997 Subject: Engine Hard Start or No Start (Replace Fuel Pump Pulsator) Models: 1992-96 Chevrolet and GMC Trucks 1992-96 Oldsmobile Bravada with Gasoline Engines Condition Some owners may report their engine is hard to start or will not start. Cause The fuel delivery system may have low or no pressure due to a ruptured fuel pump pulsator The pulsator is the flexible connector between the fuel pump and the metal fuel line in the tank. This rupture appears as a tear in the pulsator openings and is the result of exposure to gasoline containing a high percentage of ethanol. Correction Follow the Strategy Based Diagnostic Steps for the reported symptoms. If diagnosis reveals low or no fuel system pressure, and the fuel pump is identified as a possible cause, follow the service procedure for, On-Vehicle Service, Fuel Pump, in the appropriate Truck Service Manual. Before replacing the fuel pump, inspect the pulsator for signs of tears or leaks It the pulsator is damaged, replace it with P/N 25175836 and re-test the fuel system for normal pressure. This pulsator is made of Viton which is resistant to Ethanol content fuels. P/N 25175836 replaces P/N 25094266 for trucks. This change will appear in GMSPO parts catalogs as they are revised. Part Information P/N Description QTY 25175836 Damper Asm - Fuel Pulsator 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Labor Op Description Labor Time J 5590 Pump, Fuel R&R; Use Published Labor Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pressure Pulsation Damper > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 666309 > Apr > 97 > Engine - Hard Start Or No Start Fuel Pressure Pulsation Damper: All Technical Service Bulletins Engine - Hard Start Or No Start File In Section: 6E Engine Fuel & Emission Bulletin No.: 66-63-09 Date: April, 1997 Subject: Engine Hard Start or No Start (Replace Fuel Pump Pulsator) Models: 1992-96 Chevrolet and GMC Trucks 1992-96 Oldsmobile Bravada with Gasoline Engines Condition Some owners may report their engine is hard to start or will not start. Cause The fuel delivery system may have low or no pressure due to a ruptured fuel pump pulsator. The pulsator is the flexible connector between the fuel pump and the metal fuel line in the tank. This rupture appears as a tear in the pulsator openings and is the result of exposure to gasoline containing a high percentage of ethanol. Correction Follow the Strategy Based Diagnostic Steps for the reported symptoms. If diagnosis reveals low or no fuel system pressure, and the fuel pump is identified as a possible cause, follow the service procedure for, On-Vehicle Service, Fuel Pump, in the appropriate Truck Service Manual. Before replacing the fuel pump, inspect the pulsator for signs of tears or leaks. If the pulsator is damaged, replace it with P/N 25175836 and re-test the fuel system for normal pressure. This pulsator is made of Viton which is resistant to Ethanol content fuels. P/N 25175836 replaces P/N 25094266 for trucks. This change will appear in GMSPO parts catalogs as they are revised. Part Information P/N Description Qty 25175836 Damper Asm - Fuel Pulsator 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty. use: Labor Op Description Labor Time Use Published Labor J 5590 Pump, Fuel R&R; Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pressure Pulsation Damper > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Pressure Pulsation Damper: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules Relay Module: All Technical Service Bulletins Electrical - MIL ON/DTC's Set By Various Control Modules TECHNICAL Bulletin No.: 09-06-03-004D Date: December 08, 2010 Subject: Intermittent No Crank/No Start, No Module Communication, MIL, Warning Lights, Vehicle Messages or DTCs Set by Various Control Modules - Diagnosing and Repairing Fretting Corrosion (Disconnect Affected Connector and Apply Dielectric Lubricant) Models: 2011 and Prior GM Passenger Cars and Trucks Attention: This repair can be applied to ANY electrical connection including, but not limited to: lighting, body electrical, in-line connections, powertrain control sensors, etc. DO NOT over apply lubricant to the point where it prevents the full engagement of sealed connectors. A light coating on the terminal surfaces is sufficient to correct the condition. Supercede: This bulletin is being revised to update the Attention statement and add the 2011 model year. Please discard Corporate Bulletin Number 09-06-03-004C (Section 06 Engine/Propulsion System). Condition Some customers may comment on any of the following conditions: - An intermittent no crank/no start - Intermittent malfunction indicator lamp (MIL) illumination - Intermittent service lamp illumination - Intermittent service message(s) being displayed The technician may determine that he is unable to duplicate the intermittent condition. Cause This condition may be caused by a buildup of nonconductive insulating oxidized debris known as fretting corrosion, occurring between two electrical contact surfaces of the connection or connector. This may be caused by any of the following conditions: - Vibration - Thermal cycling - Poor connection/terminal retention - Micro motion - A connector, component or wiring harness not properly secured resulting in movement On low current signal circuits this condition may cause high resistance, resulting in intermittent connections. On high current power circuits this condition may cause permanent increases in the resistance and may cause a device to become inoperative. Representative List of Control Modules and Components The following is only a representative list of control modules and components that may be affected by this connection or connector condition and DOES NOT include every possible module or component for every vehicle. - Blower Control Module - Body Control Module (BCM) - Communication Interface Module (CIM) - Cooling Fan Control Module - Electronic Brake Control Module (EBCM) - Electronic Brake and Traction Control Module (EBTCM) - Electronic Suspension Control (ESC) Module - Engine Control Module (ECM) - Heating, Ventilation and Air Conditioning (HVAC) Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pressure Pulsation Damper > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Pressure Pulsation Damper: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 6155 - HVAC Actuator - Inflatable Restraint Sensing and Diagnostic Module (SDM) - Any AIR BAG module - Seatbelt Lap Anchor Pretensioner - Seatbelt Retractor Pretensioner - An SIR system connection or connector condition resulting in the following DTCs being set: B0015, B0016, B0019, B0020, B0022, or B0023 - Powertrain Control Module (PCM) - Remote Control Door Lock Receiver (RCDLR) - Transmission Control Module (TCM) Correction Important DO NOT replace the control module, wiring or component for the following conditions: - The condition is intermittent and cannot be duplicated. - The condition is present and by disconnecting and reconnecting the connector the condition can no longer be duplicated. Use the following procedure to correct the conditions listed above. 1. Install a scan tool and perform the Diagnostic System Check - Vehicle. Retrieve and record any existing history or current DTCs from all of the control modules (refer to SI). ‹› If any DTC(s) are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). ‹› If DTCs are not set, refer to Symptoms - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). 2. When identified, use the appropriate DTC Diagnostics, Symptoms, Schematics, Component Connector End Views and Component Locator documents to locate and disconnect the affected harness connector(s) which are causing the condition. Note Fretting corrosion looks like little dark smudges on electrical terminals and appear where the actual electrical contact is being made. In less severe cases it may be unable to be seen or identified without the use of a magnifying glass. Important DO NOT apply an excessive amount of dielectric lubricant to the connectors as shown, as hydrolock may result when attempting to mate the connectors. Use ONLY a clean nylon brush that is dedicated to the repair of the conditions in this bulletin. 3. With a one-inch nylon bristle brush, apply dielectric lubricant to both the module/component side and the harness side of the affected connector(s). 4. Reconnect the affected connector(s) and wipe away any excess lubricant that may be present. 5. Attempt to duplicate the condition by using the following information: - DTC Diagnostic Procedure - Circuit/System Description - Conditions for Running the DTC - Conditions for Setting the DTC - Diagnostic Aids - Circuit/System Verification ‹› If the condition cannot be duplicated, the repair is complete. ‹› If the condition can be duplicated, then follow the appropriate DTC, Symptom or Circuit/System Testing procedure (refer to SI). Repair Order Documentation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pressure Pulsation Damper > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Pressure Pulsation Damper: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 6156 Important The following information MUST be documented on the repair order. Failure to do so may result in a chargeback. - Customer vehicle condition. - Was a Service Lamp or Service Message illuminated? If yes, specify which Service Lamp or Service Message. - Was a DTC(s) set? If yes, specify which DTC(s) were set. - After following the procedure contained within this bulletin, could the condition be duplicated? ‹› If the condition was not duplicated, then document the affected module/component connector name and number on the repair order. - If the condition was duplicated after the procedure contained within this bulletin was followed, and additional diagnosis led to the replacement of a module or component, the SI Document ID Number MUST be written on the repair order. Parts Information Alternate Distributor For All of North America Note NyoGel(R) 760G Lubricant* is equivalent to GMSPO P/N 12377900, and P/N 10953529 (Canada), specified for use to correct the condition in this bulletin. *We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for, or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pressure Pulsation Damper > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Pressure Pulsation Damper: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 6157 For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to refer to the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pressure Pulsation Damper > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Pressure Pulsation Damper: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 6163 - HVAC Actuator - Inflatable Restraint Sensing and Diagnostic Module (SDM) - Any AIR BAG module - Seatbelt Lap Anchor Pretensioner - Seatbelt Retractor Pretensioner - An SIR system connection or connector condition resulting in the following DTCs being set: B0015, B0016, B0019, B0020, B0022, or B0023 - Powertrain Control Module (PCM) - Remote Control Door Lock Receiver (RCDLR) - Transmission Control Module (TCM) Correction Important DO NOT replace the control module, wiring or component for the following conditions: - The condition is intermittent and cannot be duplicated. - The condition is present and by disconnecting and reconnecting the connector the condition can no longer be duplicated. Use the following procedure to correct the conditions listed above. 1. Install a scan tool and perform the Diagnostic System Check - Vehicle. Retrieve and record any existing history or current DTCs from all of the control modules (refer to SI). ‹› If any DTC(s) are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). ‹› If DTCs are not set, refer to Symptoms - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). 2. When identified, use the appropriate DTC Diagnostics, Symptoms, Schematics, Component Connector End Views and Component Locator documents to locate and disconnect the affected harness connector(s) which are causing the condition. Note Fretting corrosion looks like little dark smudges on electrical terminals and appear where the actual electrical contact is being made. In less severe cases it may be unable to be seen or identified without the use of a magnifying glass. Important DO NOT apply an excessive amount of dielectric lubricant to the connectors as shown, as hydrolock may result when attempting to mate the connectors. Use ONLY a clean nylon brush that is dedicated to the repair of the conditions in this bulletin. 3. With a one-inch nylon bristle brush, apply dielectric lubricant to both the module/component side and the harness side of the affected connector(s). 4. Reconnect the affected connector(s) and wipe away any excess lubricant that may be present. 5. Attempt to duplicate the condition by using the following information: - DTC Diagnostic Procedure - Circuit/System Description - Conditions for Running the DTC - Conditions for Setting the DTC - Diagnostic Aids - Circuit/System Verification ‹› If the condition cannot be duplicated, the repair is complete. ‹› If the condition can be duplicated, then follow the appropriate DTC, Symptom or Circuit/System Testing procedure (refer to SI). Repair Order Documentation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pressure Pulsation Damper > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Pressure Pulsation Damper: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 6164 Important The following information MUST be documented on the repair order. Failure to do so may result in a chargeback. - Customer vehicle condition. - Was a Service Lamp or Service Message illuminated? If yes, specify which Service Lamp or Service Message. - Was a DTC(s) set? If yes, specify which DTC(s) were set. - After following the procedure contained within this bulletin, could the condition be duplicated? ‹› If the condition was not duplicated, then document the affected module/component connector name and number on the repair order. - If the condition was duplicated after the procedure contained within this bulletin was followed, and additional diagnosis led to the replacement of a module or component, the SI Document ID Number MUST be written on the repair order. Parts Information Alternate Distributor For All of North America Note NyoGel(R) 760G Lubricant* is equivalent to GMSPO P/N 12377900, and P/N 10953529 (Canada), specified for use to correct the condition in this bulletin. *We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for, or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pressure Pulsation Damper > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fuel Pressure Pulsation Damper: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 6165 For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to refer to the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pressure > Diagnostic Connector - Fuel Pump > Component Information > Locations Diagnostic Connector - Fuel Pump: Locations For Fuel Pump Prime and Run Connector, See Computer and Control Systems, Data Link Connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Locations Fuel Pump Balance Module: Locations FUEL PUMP BALANCE MODULE (Vehicles with Dual Tanks Only) On vehicles over 15,000 GVWR and equipped with dual fuel tanks, the Fuel Pump Balance Module is located inside the left frame rail, near Transmission Crossmember. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Locations > Page 6174 Fuel Pump Balance Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Locations > Page 6175 Fuel Pump Balance Module: Description and Operation FUEL BALANCE CONTROL SYSTEM The fuel balance control system consists of the following components: - Front (main) fuel tank sender. - Rear (auxiliary) fuel tank sender. - Balance fuel pump. - Balance fuel pump relay. - Fuel sender and balance module. On vehicles with dual tanks, the front tank is the main and the rear tank is the auxiliary. The main fuel pump supplies fuel to the fuel injection unit. The low pressure (about 32 kPa or 7 psi) fuel balance pump is used only to transfer fuel from the auxiliary tank to the main tank in order to balance the fuel levels in both tanks. As the main tank level drops to about 25 % below the level in the auxiliary tank, the fuel sender and balance module energizes the fuel pump relay. This pumps the fuel from the auxiliary tank to the main tank. When the level in the main tank reaches a level slightly higher than the level in the auxiliary tank, or the auxiliary tank is empty, the module de-energizes the balance pump relay and fuel pump. Any malfunction in either of the fuel gage circuits will disable the system and the fuel will not be transferred from the main fuel tank to the auxiliary fuel tank. FUEL PUMP BALANCE MODULE The Fuel Pump Balance Module relies on input from the primary and secondary fuel senders, and cannot operate if the fuel gauge is not working properly. For Fuel Pump Balance Module testing and inspection refer to Instrument Panel, Gauges and Warning Indicators / Symptom Releated Diagnostic Procedures / Fuel Gauge See: Instrument Panel, Gauges and Warning Indicators/Testing and Inspection/Symptom Related Diagnostic Procedures For Fuel Pump Balance Module electrical diagrams refer to Instrument Panel, Gauges and Warning Indicators / Diagrams / Electrical. See: Instrument Panel, Gauges and Warning Indicators/Diagrams Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times Fuel Gage Indicates Empty At All Times Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times > Page 6178 Fuel Gage Indicates Full At All Times Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times > Page 6179 Fuel Pump Balance Module: Testing and Inspection Fuel Gage Is Inaccurate Fuel Gage Is Inaccurate (Part 1 Of 2) Fuel Gage Is Inaccurate (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times > Page 6180 Fuel Pump Balance Module: Testing and Inspection Vehicle Runs Out of Fuel (Rear Tank Not Empty) Vehicle Runs Out Of Fuel At Half-Full/rear Tank Is Full At All Times (Part 1 Of 2) Vehicle Runs Out Of Fuel At Half-Full/rear Tank Is Full At All Times (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times > Page 6181 Fuel Gage Does Not Change Position On Scale Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Page 6182 Fuel Pump Balance Module: Service and Repair REMOVAL PROCEDURE WARNING: To reduce the risk of fire and personal in jury that may result from a fuel leak, always replace O-ring seals exposed during component service. 1. Disconnect the negative battery cable. 2. Loosen the filler cap(s) to Relieve fuel tank pressure. See: Service and Repair 3. Disconnect the electrical connector. 4. Clean both fuel pipe connections and surrounding areas at the fuel pump before disconnecting to avoid possible contamination of the fuel system. 5. Disconnect both fuel pipes from the pump. 6. Slide the pump out of the bracket. INSTALLATION PROCEDURE 1. Install the new fuel pipe O-rings. 2. Position the new pump in the pump bracket. 3. Connect the fuel feed pipe and suction pipe to the fuel pump. Tighten Use a backup wrench to prevent the pump from turning. Tighten the fittings to 3O Nm (22 lb. ft.). 4. Connect the electrical connector. 5. Connect the negative battery cable. 6. Check for fuel leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Page 6183 6.1. Turn the ignition ON for 2 seconds. 6.2. Turn OFF the ignition for 10 seconds. 6.3. Again, turn the ignition switch to the ON position. 6.4. Check for fuel leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Locations > Fuel Pump Relay Fuel Pump Relay: Locations Fuel Pump Relay FUEL PUMP RELAY Auxiliary Battery Wiring Underhood Fuse-Relay Center The Fuel Pump Relay is located in Underhood Fuse Relay Center. The Underhood Fuse Relay Center is located on the LH rear of engine compartment, on fender. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Locations > Fuel Pump Relay > Page 6188 Fuel Pump Relay: Locations Fuel Pump Relay (Balance Pump) FUEL PUMP RELAY (BALANCE PUMP) (Vehicles with Dual Tanks Only) On vehicles over 15,000 GVWR and equipped with dual fuel tanks, the Fuel Pump Balance Relay is located inside the left frame rail, near Transmission Crossmember. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions Fuel Pump Relay: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6191 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6192 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6193 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6194 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6195 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6196 Fuel Pump Relay: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6197 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6198 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6199 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6200 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6201 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6202 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6203 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6204 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6205 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6206 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6207 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6208 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6209 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6210 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6211 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6212 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6213 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6214 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6215 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6216 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6217 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6218 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6219 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6220 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6221 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6222 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6223 Fuel Pump Relay: Connector Views Fuel Pump Balance Relay Fuel Pump Relay FUEL PUMP RELAY CONNECTOR VIEW Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6224 Underhood Fuse-Relay Center (Part 1 Of 2) The Fuel Pump Relay is located in the Underhood Fuse-Relay Center. Refer to terminals, A1 - B1 B2 - A3 - B3. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Description and Operation > Fuel Pump Relay Operation Fuel Pump Relay: Description and Operation Fuel Pump Relay Operation OPERATION When the key is turned ON with out the engine running, the control module turns a fuel pump relay ON for two seconds. This builds up fuel pressure quickly. If the engine is not started within two seconds, the control module shuts the fuel pump OFF and waits until the engine starts. As soon as the engine is cranked, the control module turns the relay ON and runs the fuel pump. When the engine is cranking or running, the control module receives the Crankshaft Position (CKP) sensor reference pulses which in turn energize the fuel injectors. As a backup system to the fuel pump relay, the fuel pump can also be turned ON by a fuel pump oil pressure switch. When the engine reaches about 28 kPa (4 psi), and the fuel pump relay does not complete the circuit, the fuel pump oil pressure switch will close to complete the circuit to run the fuel pump. An inoperative fuel pump relay can result in long cranking times, particularly if the engine is cold. The fuel pump oil pressure switch will turn ON the fuel pump as soon as oil pressure reaches about 28 kPa (4 psi). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Description and Operation > Fuel Pump Relay Operation > Page 6227 Fuel Pump Relay: Description and Operation Fuel Balance Module Control System (Dual Tanks) FUEL BALANCE CONTROL SYSTEM The fuel balance control system consists of the following components: - Front (main) fuel tank sender. - Rear (auxiliary) fuel tank sender. - Balance fuel pump. - Balance fuel pump relay. - Fuel sender and balance module. On vehicles with dual tanks, the front tank is the main and the rear tank is the auxiliary. The main fuel pump supplies fuel to the fuel injection unit. The low pressure (about 32 kPa or 7 psi) fuel balance pump is used only to transfer fuel from the auxiliary tank to the main tank in order to balance the fuel levels in both tanks. As the main tank level drops to about 25 % below the level in the auxiliary tank, the fuel sender and balance module energizes the fuel pump relay. This pumps the fuel from the auxiliary tank to the main tank. When the level in the main tank reaches a level slightly higher than the level in the auxiliary tank, or the auxiliary tank is empty, the module de-energizes the balance pump relay and fuel pump. Any malfunction in either of the fuel gage circuits will disable the system and the fuel will not be transferred from the main fuel tank to the auxiliary fuel tank. FUEL PUMP BALANCE MODULE The Fuel Pump Balance Module relies on input from the primary and secondary fuel senders, and cannot operate if the fuel gauge is not working properly. For Fuel Pump Balance Module testing and inspection refer to Instrument Panel, Gauges and Warning Indicators / Symptom Releated Diagnostic Procedures / Fuel Gauge See: Instrument Panel, Gauges and Warning Indicators/Testing and Inspection/Symptom Related Diagnostic Procedures For Fuel Pump Balance Module electrical diagrams refer to Instrument Panel, Gauges and Warning Indicators / Diagrams / Electrical. See: Instrument Panel, Gauges and Warning Indicators/Diagrams Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump > Fuel Pump Relay > Component Information > Description and Operation > Page 6228 Fuel Pump Relay: Service and Repair Removal Procedure 1. Remove the underhood electrical center cover. 2. Remove the relay. Installation Procedure 1. Install the relay. 2. Install the underhood electrical center cover. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pump Pickup Filter > Component Information > Description and Operation Fuel Pump Pickup Filter: Description and Operation A woven plastic filter attaches to the lower end of the fuel pump in the fuel tank. The functions of the strainer are to filter contaminants and to wick fuel. The life of the fuel pump strainer is generally considered to be that of the fuel pump. The fuel pump strainer is self-cleaning and normally requires no maintenance. Fuel stoppage at this point indicates that the fuel tank contains an abnormal amount of sediment or water. In which case the fuel tank should have a thorough cleaning. Refer to Fuel System Cleaning. If the fuel strainer is plugged, replace the strainer with a new fuel pump strainer. See: Service and Repair Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Return Line > Component Information > Specifications Fuel Return Line: Specifications Rear fuel line bracket bolt .................................................................................................................... .................................................... 6.O Nm (53 lb. in.) Fuel pipe retainer nuts ..................................... ......................................................................................................................................... 3.0 Nm (27 lb. in.) Fuel pipe nuts ........................................................................................................................... ............................................................... 30.O Nm (22 lb. ft) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Return Line > Component Information > Description and Operation > Fuel Pipe O-Rings Fuel Return Line: Description and Operation Fuel Pipe O-Rings The fuel feed and return pipe threaded connections at the fuel injection unit are sealed with replaceable O-ring seals. These O-ring seals are made of special material and should only be serviced with the correct service part. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Return Line > Component Information > Description and Operation > Fuel Pipe O-Rings > Page 6237 Fuel Return Line: Description and Operation Nylon Fuel Pipes WARNING: In Order To Reduce the Risk of Fire and Personal Injury: Always cover nylon fuel pipes with a wet towel before using a torch near them. Also, never expose the vehicle to temperatures higher then 115°C (239°F) for more than one hour, or more than 90°C (194°F) for any extended period. Take care not to nick or scratch the nylon fuel pipes. If damaged, they must be replaced. Nylon fuel pipes are designed to perform the same job as the steel or rubber fuel tubes they replace. Nylon pipes are constructed to withstand maximum fuel system pressure, exposure to fuel additives and changes in temperature. There are two sizes used: 3/8 in. ID for the fuel feed and 5/16 in. ID for the fuel return. The fuel teed and return pipes are assembled as a harness. Retaining clips hold the pipes together and provide a means for attaching the pipes to the vehicle. Quick-connect type fittings are used at the fuel tank ends of the fuel feed/return pipes and at the in-line fuel filter. They are described below. Sections of the pipes that are exposed to chafing, high temperature or vibration are protected with a heat resistant rubber hose and/or corrugated plastic conduit. Nylon fuel pipes are somewhat flexible and can be formed around gradual turns under the vehicle. However if forced into sharp bends nylon pipes will kink and restrict fuel flow. Once exposed to fuel, nylon pipes may become stiffer and are more likely to kink if bent too far. Special care should be taken when working on a vehicle with nylon fuel pipes. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Return Line > Component Information > Description and Operation > Fuel Pipe O-Rings > Page 6238 Fuel Return Line: Description and Operation Fuel and Vapor Pipes WARNING: In Order To Reduce the Risk of Fire and Personal Injury: Always cover nylon fuel pipes with a wet towel before using a torch near them. Also, never expose the vehicle to temperatures higher then 115°C (239°F) for more than one hour, or more than 9O°C (194°F) for any extended period. Take care not to nick or scratch the nylon fuel pipes. If damaged, they must be replaced. The vapor pipe extends from the fuel sender assembly to the charcoal canister. It is made up of nylon pipe and is connected to the fuel sender assembly and the EVAP canister with the fuel resistant rubber hoses. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Return Line > Component Information > Description and Operation > Page 6239 Fuel Return Line: Testing and Inspection The diagnosis of gasoline odor may be a condition of a leaking fuel feed, a return pipe or hose. Fuel pipes that are pinched, plugged, or mis-routed may cause restricted fuel delivery. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Return Line > Component Information > Service and Repair > Fuel Pressure Connection Fuel Return Line: Service and Repair Fuel Pressure Connection REMOVAL PROCEDURE The fuel pressure connection is non-replaceable, but it is serviceable. 1. Disconnect the negative battery cable. 2. Relieve the fuel system pressure. Refer to Fuel Pressure Relief Procedure. See: Service and Repair 3. Remove the fuel pressure connection cap. 4. Using a standard valve core removal tool, remove the valve core assembly. 5. Discard the valve core assembly. INSTALLATION PROCEDURE 1. Using the standard valve core tool, install a new valve core assembly. 2. Connect the negative battery cable. 3. Inspect for fuel leaks through the following steps: 3.1. Turn ON ignition switch for 2 seconds. 3.2. Then turn the ignition switch to the OFF position for 10 seconds. 3.3. Again turn the ignition switch to the ON position. 3.4. Check for fuel leaks. 4. Install the fuel pressure connection cap. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Return Line > Component Information > Service and Repair > Fuel Pressure Connection > Page 6242 Fuel Return Line: Service and Repair Fuel Hose and Pipes Diagram Diagram Removal Procedure 1. Disconnect the negative battery cable. 2. Relieve the fuel system pressure. Refer to Fuel Pressure Relief Procedure. See: Service and Repair 3. Disconnect the fittings at the engine compartment fuel feed and return pipes. 4. Disconnect the fuel pipe attaching hardware. 5. Disconnect the fuel feed and return pipe nuts at the fuel inlet and fuel outlet assembly. 6. Disconnect the fuel feed and return pipes and O-rings. Discard O-rings. 7. Remove the fuel tank. Refer to Fuel Tank Assembly. See: Fuel Tank/Service and Repair 8. Disconnect the fuel feed and vapor hoses. On 4DR Utility, the quick-connect fittings at the fuel sender assembly. Refer to Fuel Hose and Pipes. 9. Remove the hardware retaining section of pipe to be replaced. Note location of attaching hardware for installation. 10. Remove the section of pipe and hoses. 11. Remove rust or burrs from the engine compartment fuel pipes by the following procedure: 11.1. Use emery cloth in a radial motion with the fuel pipe end in order to prevent damage to the O-ring sealing surface. 11.2. Using a clean shop towel, wipe off the male tube ends. 11.3. Inspect all the Connectors for dirt and burrs. Clean or replace the components/assemblies as required. Installation Procedure WARNING: To Reduce the Risk of Fire and Personal Injury: Before connecting the fitting, always apply a few drops of clean engine oil to the male pipe end. This will ensure proper reconnection and prevent a possible fuel leak (During normal operation, the O-rings located in the female connector will swell and may prevent proper reconnection if not lubricated. 1. Install the new O-rings on the engine fuel feed and return pipes. 2. Connect the fuel feed and return pipes to the fuel injection unit. Finger tighten only. 3. Connect the fuel pipe attaching hardware. Tighten Fuel pipe attaching nuts to 27 Nm (20 lb. ft.) using a back-up wrench. 4. Position new fuel pipe harness in original location and fuel pipe harness attaching hardware. 5. Remove protective caps from one end of both fuel pipes. Leave caps on other end of pipes to prevent dirt from entering. 6. Apply a few drops of clean engine oil to the male connector tube ends. 7. Connect the quick-connect fittings at the fuel feed and pipe near the in-line filter and at the fuel sender assembly. Refer to Fuel Hose and Pipes. See: Fuel Pressure Connection 8. Install the fuel tank and attaching hardware if the tank was removed. 9. Tighten the fuel filler cap. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Return Line > Component Information > Service and Repair > Fuel Pressure Connection > Page 6243 10. Connect the negative battery cable. 11. Check for fuel leaks. 11.1. Turn the ignition switch to the ON position for 2 seconds. 11.2. Turn the ignition switch to the OFF position for 10 seconds. 11.3. Again, turn the ignition switch to the ON position. 11.4. Check for fuel leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Return Line > Component Information > Service and Repair > Fuel Pressure Connection > Page 6244 Fuel Return Line: Service and Repair Fuel Vapor Pipes and Hoses Diagram Diagram Removal Procedure NOTE: If the nylon pipes become kinked, and cannot be straightened, replace them. - Do Not attempt to repair sections of nylon pipes. If damaged, replace. - When replacing the vapor pipes, always replace them with original equipment or parts that meet GM specifications. - When replacing the vapor hoses, always replace them with original equipment or parts meeting GM specifications. Use only reinforced fuel-resistant hose identified with the word Fluoroelastomer or GM 6163-M on the hose. 1. Remove the hardware retaining section of the pipe to be replaced. Note the location of attaching hardware for installation. 2. Remove the section of the pipe and hoses. 3. Inspect the hoses for cuts, swelling, cracks and distortion. Replace as required. 4. Inspect the pipes for holes, kinks, and cracks. Replace the sections as required. Installation Procedure Important: - Follow the same routing as the original pipes and hoses. - Secure the pipes and hoses to prevent chafing. 1. Install the section of the pipe and hoses. 2. Install the hardware retaining section of the pipe being replaced. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Return Line > Component Information > Service and Repair > Fuel Pressure Connection > Page 6245 Fuel Return Line: Service and Repair Fuel Supply/Return/or Emission Pipe Service FUEL SYSTEM CLEANING (PURGE FEED AND RETURN PIPES) REMOVAL PROCEDURE 1. Disconnect the fuel feed and return pipes at the fuel injection unit. Refer to Fuel Hose and Pipes. See: Fuel Supply/Return/or Emission Pipe Replacement NOTE: Inspect the in-line fuel filter for contamination. Replace the fuel filter if it is plugged. 2. Disconnect the in-line fuel filter. Refer to In-Line Fuel Filter. See: Fuel Filter/Service and Repair NOTE: Use only oil free compressed air to blow out the fuel pipes. - If the in-line fuel filter is plugged, inspect the fuel tank internally and purge if necessary. 3. Clean the fuel lines by applying air pressure in the opposite direction of fuel flow. INSTALLATION PROCEDURE 1. Install a new strainer (if necessary) on the fuel sender assembly. Refer to Fuel Sender Assembly. See: Fuel Pump/Service and Repair NOTE: Do not fold or twist the strainer when installing the sending unit. This action restricts fuel flow. 2. Install the fuel sender assembly with a new seal into the fuel tank. 3. Install the fuel tank. Refer to Fuel Tank Assembly. See: Fuel Tank/Service and Repair 4. Disconnect the fuel feed pipe at the fuel injection unit. 5. Connect a hose to the fuel feed pipe at the fuel injection unit. Insert the other end of the hose into a 3.8 liter (one gallon) fuel can. 6. Connect the negative battery cable. 7. Add twenty-three liters (six gallons) of clean fuel into the fuel tank. 8. Purge the fuel pump and lines. 8.1. Using a fused jumper, connect the fuel pump test terminal to B+ to operate the fuel pump. Operate the fuel pump until 2 liters (1/2 gallon) flows into the fuel can. 9. Remove the jumper. 10. Connect the fuel line at the fuel injection unit. 11. Check for fuel leaks 11.1. Turn the ignition ON for 2 seconds. 11.2. Turn OFF the ignition for 10 seconds. 11.3. Again, turn the ignition switch to the ON position. 11.4. Check for fuel leaks. INSPECT Turn the ignition switch ON for two seconds then turn the switch OFF for ten seconds. Again turn the ignition switch ON and check for fuel leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Return Line > Component Information > Service and Repair > Fuel Pressure Connection > Page 6246 Fuel Return Line: Service and Repair Fuel Pressure Connection REMOVAL PROCEDURE The fuel pressure connection is non-replaceable, but it is serviceable. 1. Disconnect the negative battery cable. 2. Relieve the fuel system pressure. Refer to Fuel Pressure Relief Procedure. See: Service and Repair 3. Remove the fuel pressure connection cap. 4. Using a standard valve core removal tool, remove the valve core assembly. 5. Discard the valve core assembly. INSTALLATION PROCEDURE 1. Using the standard valve core tool, install a new valve core assembly. 2. Connect the negative battery cable. 3. Inspect for fuel leaks through the following steps: 3.1. Turn ON ignition switch for 2 seconds. 3.2. Then turn the ignition switch to the OFF position for 10 seconds. 3.3. Again turn the ignition switch to the ON position. 3.4. Check for fuel leaks. 4. Install the fuel pressure connection cap. Fuel Hose and Pipes Diagram Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Return Line > Component Information > Service and Repair > Fuel Pressure Connection > Page 6247 Diagram Removal Procedure 1. Disconnect the negative battery cable. 2. Relieve the fuel system pressure. Refer to Fuel Pressure Relief Procedure. See: Service and Repair 3. Disconnect the fittings at the engine compartment fuel feed and return pipes. 4. Disconnect the fuel pipe attaching hardware. 5. Disconnect the fuel feed and return pipe nuts at the fuel inlet and fuel outlet assembly. 6. Disconnect the fuel feed and return pipes and O-rings. Discard O-rings. 7. Remove the fuel tank. Refer to Fuel Tank Assembly. See: Fuel Tank/Service and Repair 8. Disconnect the fuel feed and vapor hoses. On 4DR Utility, the quick-connect fittings at the fuel sender assembly. Refer to Fuel Hose and Pipes. 9. Remove the hardware retaining section of pipe to be replaced. Note location of attaching hardware for installation. 10. Remove the section of pipe and hoses. 11. Remove rust or burrs from the engine compartment fuel pipes by the following procedure: 11.1. Use emery cloth in a radial motion with the fuel pipe end in order to prevent damage to the O-ring sealing surface. 11.2. Using a clean shop towel, wipe off the male tube ends. 11.3. Inspect all the Connectors for dirt and burrs. Clean or replace the components/assemblies as required. Installation Procedure WARNING: To Reduce the Risk of Fire and Personal Injury: Before connecting the fitting, always apply a few drops of clean engine oil to the male pipe end. This will ensure proper reconnection and prevent a possible fuel leak (During normal operation, the O-rings located in the female connector will swell and may prevent proper reconnection if not lubricated. 1. Install the new O-rings on the engine fuel feed and return pipes. 2. Connect the fuel feed and return pipes to the fuel injection unit. Finger tighten only. 3. Connect the fuel pipe attaching hardware. Tighten - Fuel pipe attaching nuts to 27 Nm (20 lb. ft.) using a back-up wrench. 4. Position new fuel pipe harness in original location and fuel pipe harness attaching hardware. 5. Remove protective caps from one end of both fuel pipes. Leave caps on other end of pipes to prevent dirt from entering. 6. Apply a few drops of clean engine oil to the male connector tube ends. 7. Connect the quick-connect fittings at the fuel feed and pipe near the in-line filter and at the fuel sender assembly. Refer to Fuel Hose and Pipes. See: Fuel Pressure Connection 8. Install the fuel tank and attaching hardware if the tank was removed. 9. Tighten the fuel filler cap. 10. Connect the negative battery cable. 11. Check for fuel leaks. 11.1. Turn the ignition switch to the ON position for 2 seconds. 11.2. Turn the ignition switch to the OFF position for 10 seconds. 11.3. Again, turn the ignition switch to the ON position. 11.4. Check for fuel leaks. Fuel Vapor Pipes and Hoses Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Return Line > Component Information > Service and Repair > Fuel Pressure Connection > Page 6248 Diagram Diagram Removal Procedure NOTE: If the nylon pipes become kinked, and cannot be straightened, replace them. - Do Not attempt to repair sections of nylon pipes. If damaged, replace. - When replacing the vapor pipes, always replace them with original equipment or parts that meet GM specifications. - When replacing the vapor hoses, always replace them with original equipment or parts meeting GM specifications. Use only reinforced fuel-resistant hose identified with the word Fluoroelastomer or GM 6163-M on the hose. 1. Remove the hardware retaining section of the pipe to be replaced. Note the location of attaching hardware for installation. 2. Remove the section of the pipe and hoses. 3. Inspect the hoses for cuts, swelling, cracks and distortion. Replace as required. 4. Inspect the pipes for holes, kinks, and cracks. Replace the sections as required. Installation Procedure Important: - Follow the same routing as the original pipes and hoses. - Secure the pipes and hoses to prevent chafing. 1. Install the section of the pipe and hoses. 2. Install the hardware retaining section of the pipe being replaced. Fuel Supply/Return/or Emission Pipe Service FUEL SYSTEM CLEANING (PURGE FEED AND RETURN PIPES) REMOVAL PROCEDURE 1. Disconnect the fuel feed and return pipes at the fuel injection unit. Refer to Fuel Hose and Pipes. See: Fuel Supply/Return/or Emission Pipe Replacement NOTE: Inspect the in-line fuel filter for contamination. Replace the fuel filter if it is plugged. 2. Disconnect the in-line fuel filter. Refer to In-Line Fuel Filter. See: Fuel Filter/Service and Repair NOTE: Use only oil free compressed air to blow out the fuel pipes. - If the in-line fuel filter is plugged, inspect the fuel tank internally and purge if necessary. 3. Clean the fuel lines by applying air pressure in the opposite direction of fuel flow. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Return Line > Component Information > Service and Repair > Fuel Pressure Connection > Page 6249 INSTALLATION PROCEDURE 1. Install a new strainer (if necessary) on the fuel sender assembly. Refer to Fuel Sender Assembly. See: Fuel Pump/Service and Repair NOTE: Do not fold or twist the strainer when installing the sending unit. This action restricts fuel flow. 2. Install the fuel sender assembly with a new seal into the fuel tank. 3. Install the fuel tank. Refer to Fuel Tank Assembly. See: Fuel Tank/Service and Repair 4. Disconnect the fuel feed pipe at the fuel injection unit. 5. Connect a hose to the fuel feed pipe at the fuel injection unit. Insert the other end of the hose into a 3.8 liter (one gallon) fuel can. 6. Connect the negative battery cable. 7. Add twenty-three liters (six gallons) of clean fuel into the fuel tank. 8. Purge the fuel pump and lines. 8.1. Using a fused jumper, connect the fuel pump test terminal to B+ to operate the fuel pump. Operate the fuel pump until 2 liters (1/2 gallon) flows into the fuel can. 9. Remove the jumper. 10. Connect the fuel line at the fuel injection unit. 11. Check for fuel leaks 11.1. Turn the ignition ON for 2 seconds. 11.2. Turn OFF the ignition for 10 seconds. 11.3. Again, turn the ignition switch to the ON position. 11.4. Check for fuel leaks. INSPECT Turn the ignition switch ON for two seconds then turn the switch OFF for ten seconds. Again turn the ignition switch ON and check for fuel leaks. Fuel Supply/Return/or Emission Pipe Replacement MATERIALS FUEL LINES These are welded steel tubes, meeting GM Specifications 124-M, or its equivalent. The fuel feed line is 3/8" diameter and the fuel return line is 5/16" diameter. Not use copper or aluminum tubing to replace steel tubing. Those materials do not have satisfactory durability to withstand normal vehicle vibration. COUPLED HOSE These are not to be repaired and are replaced only as an assembly. UNCOUPLED HOSE Use only reinforced furl resistant hose, made of "Fluoroelastomer" material. Do not use a hose within 4" (100 mm) of any part of the exhaust system, or within 10" (254 mm) of the catalytic converter. The hose's inside diameter must match the outside diameter of the steel tubing. CLAMPS These are stainless steel, screw bank-type clamps, #2494772, or equivalent. FUEL LINE REPAIR 1. Cut a piece of fuel hose 4" (100 mm) longer than the section of line to be removed. If more than 6" (152 mm) is to be removed, use a combination of steel pipe and hose. The hose length should not be more than 10" total. 2. Cut a section of the pipe to be replaced with a tube cutter. Use the first step of a double flaring tool to form a bead on the ends of the pipe and, also, on the new section of pipe, if used. 3. Slide the hose clamps onto the pipe and push the hose 2" (31 mm) onto each portion of the fuel pipe. Tighten a clamp on each side of the repair. 4. Secure fuel line to the frame. 5. Check for leaks. Engine Compartment Fuel Pipes Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Return Line > Component Information > Service and Repair > Fuel Pressure Connection > Page 6250 Diagram Diagram Diagram Diagram Removal Procedure 1. Disconnect the negative battery cable. 2. Relieve the fuel system pressure. Refer to the Fuel Pressure Relief Procedure. See: Service and Repair 3. Disconnect the fuel lines at rear of the intake manifold. 4. Remove the nuts 5. Remove the retainer 6. Disconnect the injector fuel inlet pipe and the outlet pipe. 7. Remove the rear fuel line bracket. 8. Pull straight up on fuel pipe to remove fuel pipes from injector assembly. 9. Remove the O-ring seals from both ends of the fuel feed and return pipes and discard. NOTE: Check the injector assembly to insure the O-rings have been removed, using the seal retainer tool. Installation Procedure WARNING: To Reduce the Risk of Fire and Personal Injury: Before connecting the fitting, always apply a few drops of clean engine oil to the male pipe end. This will ensure proper reconnection and prevent a possible fuel leak (During normal operation, the O-rings located in the female connector wall swell and may prevent proper reconnection if not lubricated. NOTE: Remember to install the new O-rings into the inlet and outlet of the fuel injector assembly, using the seal retainer tool. 1. Apply a few drops of clean engine oil to the male tube ends. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Return Line > Component Information > Service and Repair > Fuel Pressure Connection > Page 6251 2. Connect the fuel feed and return pipes to fuel assembly. 3. Install the fuel pipe retainer and attaching nuts. Once installed, pull on both ends of each connection to make sure they are secure. 4. Install the rear fuel pipe clip retaining bolt. Tighten Tighten the rear fuel line bracket bolt to 6.O Nm (53 lb. in.). - Tighten the fuel pipe retainer nuts to 3.0 Nm (27 lb. in.). 5. Install the new O-ring seals on the engine fuel feed and return pipes. 6. Connect the fuel feed and return lines to the engine fuel pipes. Tighten Tighten the fuel pipe nuts to 30.O Nm (22 lb. ft). 7. Tighten the fuel filler cap. 8. Connect the negative battery cable. 9. Check for fuel leaks. 9.1. Turn the ignition switch to the ON position for 2 seconds. 9.2. Turn the ignition switch to the OFF position for 10 seconds. 9.3. Again, turn the ignition switch to the ON position. 9.4. Check for fuel leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Supply Line > Component Information > Specifications Fuel Supply Line: Specifications Rear fuel line bracket bolt .................................................................................................................... .................................................... 6.O Nm (53 lb. in.) Fuel pipe retainer nuts ..................................... ......................................................................................................................................... 3.0 Nm (27 lb. in.) Fuel pipe nuts ........................................................................................................................... ............................................................... 30.O Nm (22 lb. ft) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Supply Line > Component Information > Description and Operation > Nylon Fuel Pipes Fuel Supply Line: Description and Operation Nylon Fuel Pipes WARNING: In Order To Reduce the Risk of Fire and Personal Injury: Always cover nylon fuel pipes with a wet towel before using a torch near them. Also, never expose the vehicle to temperatures higher then 115°C (239°F) for more than one hour, or more than 90°C (194°F) for any extended period. Take care not to nick or scratch the nylon fuel pipes. If damaged, they must be replaced. Nylon fuel pipes are designed to perform the same job as the steel or rubber fuel tubes they replace. Nylon pipes are constructed to withstand maximum fuel system pressure, exposure to fuel additives and changes in temperature. There are two sizes used: 3/8 in. ID for the fuel feed and 5/16 in. ID for the fuel return. The fuel teed and return pipes are assembled as a harness. Retaining clips hold the pipes together and provide a means for attaching the pipes to the vehicle. Quick-connect type fittings are used at the fuel tank ends of the fuel feed/return pipes and at the in-line fuel filter. They are described below. Sections of the pipes that are exposed to chafing, high temperature or vibration are protected with a heat resistant rubber hose and/or corrugated plastic conduit. Nylon fuel pipes are somewhat flexible and can be formed around gradual turns under the vehicle. However if forced into sharp bends nylon pipes will kink and restrict fuel flow. Once exposed to fuel, nylon pipes may become stiffer and are more likely to kink if bent too far. Special care should be taken when working on a vehicle with nylon fuel pipes. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Supply Line > Component Information > Description and Operation > Nylon Fuel Pipes > Page 6257 Fuel Supply Line: Description and Operation Fuel Pipe O-Rings The fuel feed and return pipe threaded connections at the fuel injection unit are sealed with replaceable O-ring seals. These O-ring seals are made of special material and should only be serviced with the correct service part. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Supply Line > Component Information > Description and Operation > Nylon Fuel Pipes > Page 6258 Fuel Supply Line: Description and Operation Fuel and Vapor Pipes WARNING: In Order To Reduce the Risk of Fire and Personal Injury: Always cover nylon fuel pipes with a wet towel before using a torch near them. Also, never expose the vehicle to temperatures higher then 115°C (239°F) for more than one hour, or more than 9O°C (194°F) for any extended period. Take care not to nick or scratch the nylon fuel pipes. If damaged, they must be replaced. The vapor pipe extends from the fuel sender assembly to the charcoal canister. It is made up of nylon pipe and is connected to the fuel sender assembly and the EVAP canister with the fuel resistant rubber hoses. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Supply Line > Component Information > Description and Operation > Page 6259 Fuel Supply Line: Testing and Inspection The diagnosis of gasoline odor may be a condition of a leaking fuel feed, a return pipe or hose. Fuel pipes that are pinched, plugged, or mis-routed may cause restricted fuel delivery. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Supply Line > Component Information > Service and Repair > Fuel Pressure Connection Fuel Supply Line: Service and Repair Fuel Pressure Connection REMOVAL PROCEDURE The fuel pressure connection is non-replaceable, but it is serviceable. 1. Disconnect the negative battery cable. 2. Relieve the fuel system pressure. Refer to Fuel Pressure Relief Procedure. See: Service and Repair 3. Remove the fuel pressure connection cap. 4. Using a standard valve core removal tool, remove the valve core assembly. 5. Discard the valve core assembly. INSTALLATION PROCEDURE 1. Using the standard valve core tool, install a new valve core assembly. 2. Connect the negative battery cable. 3. Inspect for fuel leaks through the following steps: 3.1. Turn ON ignition switch for 2 seconds. 3.2. Then turn the ignition switch to the OFF position for 10 seconds. 3.3. Again turn the ignition switch to the ON position. 3.4. Check for fuel leaks. 4. Install the fuel pressure connection cap. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Supply Line > Component Information > Service and Repair > Fuel Pressure Connection > Page 6262 Fuel Supply Line: Service and Repair Fuel Hose and Pipes Diagram Diagram Removal Procedure 1. Disconnect the negative battery cable. 2. Relieve the fuel system pressure. Refer to Fuel Pressure Relief Procedure. See: Service and Repair 3. Disconnect the fittings at the engine compartment fuel feed and return pipes. 4. Disconnect the fuel pipe attaching hardware. 5. Disconnect the fuel feed and return pipe nuts at the fuel inlet and fuel outlet assembly. 6. Disconnect the fuel feed and return pipes and O-rings. Discard O-rings. 7. Remove the fuel tank. Refer to Fuel Tank Assembly. See: Fuel Tank/Service and Repair 8. Disconnect the fuel feed and vapor hoses. The quick-connect fittings at the fuel sender assembly. Refer to Fuel Line Coupler. See: Fuel Line Coupler/Service and Repair 9. Remove the hardware retaining section of pipe to be replaced. Note location of attaching hardware for installation. 10. Remove the section of pipe and hoses. 11. Remove rust or burrs from the engine compartment fuel pipes by the following procedure: 11.1. Use emery cloth in a radial motion with the fuel pipe end in order to prevent damage to the O-ring sealing surface. 11.2. Using a clean shop towel, wipe off the male tube ends. 11.3. Inspect all the Connectors for dirt and burrs. Clean or replace the components/assemblies as required. Installation Procedure WARNING: To Reduce the Risk of Fire and Personal Injury: Before connecting the fitting, always apply a few drops of clean engine oil to the male pipe end. This will ensure proper reconnection and prevent a possible fuel leak (During normal operation, the O-rings located in the female connector will swell and may prevent proper reconnection if not lubricated. 1. Install the new O-rings on the engine fuel feed and return pipes. 2. Connect the fuel feed and return pipes to the fuel injection unit. Finger tighten only. 3. Connect the fuel pipe attaching hardware. Tighten Fuel pipe attaching nuts to 27 Nm (20 lb. ft.) using a back-up wrench. 4. Position new fuel pipe harness in original location and fuel pipe harness attaching hardware. 5. Remove protective caps from one end of both fuel pipes. Leave caps on other end of pipes to prevent dirt from entering. 6. Apply a few drops of clean engine oil to the male connector tube ends. 7. Connect the quick-connect fittings at the fuel feed and pipe near the in-line filter and at the fuel sender assembly. Refer to Fuel Hose and Pipes. See: Fuel Pressure Connection 8. Install the fuel tank and attaching hardware if the tank was removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Supply Line > Component Information > Service and Repair > Fuel Pressure Connection > Page 6263 9. Tighten the fuel filler cap. 10. Connect the negative battery cable. 11. Check for fuel leaks. 11.1. Turn the ignition switch to the ON position for 2 seconds. 11.2. Turn the ignition switch to the OFF position for 10 seconds. 11.3. Again, turn the ignition switch to the ON position. 11.4. Check for fuel leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Supply Line > Component Information > Service and Repair > Fuel Pressure Connection > Page 6264 Fuel Supply Line: Service and Repair Fuel Vapor Pipes and Hoses Diagram Diagram Removal Procedure NOTE: If the nylon pipes become kinked, and cannot be straightened, replace them. - Do Not attempt to repair sections of nylon pipes. If damaged, replace. - When replacing the vapor pipes, always replace them with original equipment or parts that meet GM specifications. - When replacing the vapor hoses, always replace them with original equipment or parts meeting GM specifications. Use only reinforced fuel-resistant hose identified with the word Fluoroelastomer or GM 6163-M on the hose. 1. Remove the hardware retaining section of the pipe to be replaced. Note the location of attaching hardware for installation. 2. Remove the section of the pipe and hoses. 3. Inspect the hoses for cuts, swelling, cracks and distortion. Replace as required. 4. Inspect the pipes for holes, kinks, and cracks. Replace the sections as required. Installation Procedure Important: - Follow the same routing as the original pipes and hoses. - Secure the pipes and hoses to prevent chafing. 1. Install the section of the pipe and hoses. 2. Install the hardware retaining section of the pipe being replaced. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Supply Line > Component Information > Service and Repair > Fuel Pressure Connection > Page 6265 Fuel Supply Line: Service and Repair Fuel Supply/Return/or Emission Pipe Service FUEL SYSTEM CLEANING (PURGE FEED AND RETURN PIPES) REMOVAL PROCEDURE 1. Disconnect the fuel feed and return pipes at the fuel injection unit. Refer to Fuel Hose and Pipes. See: Fuel Return Line/Service and Repair/Fuel Supply/Return/or Emission Pipe Replacement NOTE: Inspect the in-line fuel filter for contamination. Replace the fuel filter if it is plugged. 2. Disconnect the in-line fuel filter. Refer to In-Line Fuel Filter. See: Fuel Filter/Service and Repair NOTE: Use only oil free compressed air to blow out the fuel pipes. - If the in-line fuel filter is plugged, inspect the fuel tank internally and purge if necessary. 3. Clean the fuel lines by applying air pressure in the opposite direction of fuel flow. INSTALLATION PROCEDURE 1. Install a new strainer (if necessary) on the fuel sender assembly. Refer to Fuel Sender Assembly. See: Fuel Pump/Service and Repair NOTE: Do not fold or twist the strainer when installing the sending unit. This action restricts fuel flow. 2. Install the fuel sender assembly with a new seal into the fuel tank. 3. Install the fuel tank. Refer to Fuel Tank Assembly. See: Fuel Tank/Service and Repair 4. Disconnect the fuel feed pipe at the fuel injection unit. 5. Connect a hose to the fuel feed pipe at the fuel injection unit. Insert the other end of the hose into a 3.8 liter (one gallon) fuel can. 6. Connect the negative battery cable. 7. Add twenty-three liters (six gallons) of clean fuel into the fuel tank. 8. Purge the fuel pump and lines. 8.1. Using a fused jumper, connect the fuel pump test terminal to B+ to operate the fuel pump. Operate the fuel pump until 2 liters (1/2 gallon) flows into the fuel can. 9. Remove the jumper. 10. Connect the fuel line at the fuel injection unit. 11. Check for fuel leaks 11.1. Turn the ignition ON for 2 seconds. 11.2. Turn OFF the ignition for 10 seconds. 11.3. Again, turn the ignition switch to the ON position. 11.4. Check for fuel leaks. INSPECT Turn the ignition switch ON for two seconds then turn the switch OFF for ten seconds. Again turn the ignition switch ON and check for fuel leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Supply Line > Component Information > Service and Repair > Fuel Pressure Connection > Page 6266 Fuel Supply Line: Service and Repair Engine Compartment Fuel Pipes Diagram Diagram Diagram Diagram Removal Procedure 1. Disconnect the negative battery cable. 2. Relieve the fuel system pressure. Refer to the Fuel Pressure Relief Procedure. See: Service and Repair 3. Disconnect the fuel lines at rear of the intake manifold. 4. Remove the nuts 5. Remove the retainer 6. Disconnect the injector fuel inlet pipe and the outlet pipe. 7. Remove the rear fuel line bracket. 8. Pull straight up on fuel pipe to remove fuel pipes from injector assembly. 9. Remove the O-ring seals from both ends of the fuel feed and return pipes and discard. NOTE: Check the injector assembly to insure the O-rings have been removed, using the seal retainer tool. Installation Procedure WARNING: To Reduce the Risk of Fire and Personal Injury: Before connecting the fitting, always apply a few drops of clean engine oil to the male pipe end. This will ensure proper reconnection and prevent a possible fuel leak (During normal operation, the O-rings located in the female connector wall swell and may prevent proper reconnection if not lubricated. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Supply Line > Component Information > Service and Repair > Fuel Pressure Connection > Page 6267 NOTE: Remember to install the new O-rings into the inlet and outlet of the fuel injector assembly, using the seal retainer tool. 1. Apply a few drops of clean engine oil to the male tube ends. 2. Connect the fuel feed and return pipes to fuel assembly. 3. Install the fuel pipe retainer and attaching nuts. Once installed, pull on both ends of each connection to make sure they are secure. 4. Install the rear fuel pipe clip retaining bolt. Tighten Tighten the rear fuel line bracket bolt to 6.O Nm (53 lb. in.). - Tighten the fuel pipe retainer nuts to 3.0 Nm (27 lb. in.). 5. Install the new O-ring seals on the engine fuel feed and return pipes. 6. Connect the fuel feed and return lines to the engine fuel pipes. Tighten Tighten the fuel pipe nuts to 30.O Nm (22 lb. ft). 7. Tighten the fuel filler cap. 8. Connect the negative battery cable. 9. Check for fuel leaks. 9.1. Turn the ignition switch to the ON position for 2 seconds. 9.2. Turn the ignition switch to the OFF position for 10 seconds. 9.3. Again, turn the ignition switch to the ON position. 9.4. Check for fuel leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Hose > Component Information > Technical Service Bulletins > Recalls for Fuel Filler Hose: > 99066F > Mar > 03 > Campaign Fuel Injector Sticking Closed Fuel Filler Hose: Recalls Campaign - Fuel Injector Sticking Closed File In Section: 06-Engine Emissions Bulletin No.: 99066F Date: March, 2003 SPECIAL POLICY SUBJECT: 99066F - SPECIAL POLICY ADJUSTMENT - SEQUENTIAL CENTRAL PORT FUEL INJECTION (SCPI) FAILURES IN CALIFORNIA ONLY (YF5 EMISSION EQUIPPED) MODELS: CERTAIN 1996, 1997, 1998, 1999, 2000, 2001, 2002 S/T, M/L, C/K, G, P, W4/NPR TRUCKS AND 2003 NPR TRUCKS EQUIPPED WITH 4.3L (RPO L35 - VIN CODE W OR RPO LF6 - VIN CODE X), 5.0L (RPO L30 - VIN CODE M) OR 5.7L (RPO L31 - VIN CODE R) ENGINE AND CALIFORNIA EMISSION EQUIPPED (RPO YF5) This bulletin is being revised to add the 2002 and 2003 model years to the SCPI Special Policy on certain S/T, M/L, C/K, G, P and W4/NPR truck models. Please discard Special Policy Bulletin Number 99066E, dated February, 2003. CONDITION Some customers of 1996, 1997, 1998, 1999, 2000, 2001, 2002 model year S/T, M/L, C/K, G, P, W4/NPR trucks and 2003 NPR trucks, that are registered in California, equipped with 4.3L (RPO L35 and VIN Code W, or RPO LF6 and VIN Code X), 5.0L (RPO L30 and VIN Code M) or 5.7L (RPO L31 and VIN Code R) engine, and California emissions (RPO YF5), may experience a "Service Engine Soon" light, misfire, rough idle or hard start due to a deposit build-up on the Sequential Central Port Fuel Injector (SCPI) poppet valve(s). The deposit build-up may cause injector poppets to stick closed. Certain fuels have been found to interact with the SCPI system to cause the deposits. SPECIAL POLICY ADJUSTMENT This special policy covers the SCPI failure condition described above for a period of ten (10) years or 200,000 miles, whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership. The repairs will be made at no charge to the owner. This special policy applies ONLY to repairs requiring SCPI system servicing, injector cleaning and/or MFI assembly replacement of the SCPI system. The customer should not be charged for performing a system check when it is determined that the SCPI system is not the cause of a customer complaint (labor operation T5532 is provided to submit claims for such system checks). Any additional necessary diagnosis and repairs that are not related to the SCPI condition are not covered by this special policy. The customer should be informed that any further service that is not covered by new vehicle warranty will not be covered by this policy. VEHICLES INVOLVED Involved are certain 1996,1997,1998,1999, 2000, 2001, 2002 S/T, M/L, C/K, G, P, W4/NPR and 2003 NPR model vehicles, registered in California, equipped with 4.3L (RPO L35 - VIN Code W, or RPO LF6 - VIN Code X), 5.0L (RPO L30 - VIN Code M) or 5.7L (RPO L31 - VIN Code R) engine; and California emissions (RPO YF5). This Special Policy covers all vehicles within these model years, with these engine and emissions RPO's. PARTS INFORMATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Hose > Component Information > Technical Service Bulletins > Recalls for Fuel Filler Hose: > 99066F > Mar > 03 > Campaign Fuel Injector Sticking Closed > Page 6277 Parts required to complete this special policy are to be obtained from General Motors Service Parts Operations (GMSPO). Please refer to your "involved vehicles listing" prior to ordering parts. Normal orders should be placed on a DRO Daily Replenishment Order. In an emergency, parts should be ordered on a CSO = Customer Special Order. IMPORTANT: Isuzu Parts Ordering: In order to comply with the 10-digit Isuzu part numbering system, Isuzu dealers must add an "8" to the beginning and a "0" to the end of the listed 8-digit part numbers when ordering parts through AIPDN. CUSTOMER NOTIFICATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Hose > Component Information > Technical Service Bulletins > Recalls for Fuel Filler Hose: > 99066F > Mar > 03 > Campaign Fuel Injector Sticking Closed > Page 6278 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Hose > Component Information > Technical Service Bulletins > Recalls for Fuel Filler Hose: > 99066F > Mar > 03 > Campaign Fuel Injector Sticking Closed > Page 6279 Customers will be notified of this special policy on their vehicles by General Motors (see copy of typical customer letter included with this bulletin - actual divisional letter may vary slightly). SERVICE PROCEDURE System Check: Use strategy-based diagnoses listed in the front of the Driveability and Emissions section of the service manual. If the SCPI system is operating properly, inform the customer that the vehicle does not have the condition listed in the owner letter. If poor driveability conditions persist, inform the customer that any further diagnosis and repairs will be at their expense if the vehicle is outside the parameters of the new vehicle warranty. SCPI Injector Cleaning Procedure: If diagnosis leads to sticking poppet nozzles, use the service procedure from Service Bulletin 00-06-04-003B to clean the SCPI poppet nozzles. Please note that the service bulletin term for SCPI is Central Sequential Fuel Injection (CSFI), but is referring to the same fuel system assembly. If the poppet nozzles have previously been cleaned and the sticking condition has reoccurred, refer to the correction paragraph below. SCPI Fuel Tank Fill Pipe Assembly for 1997-99 M/L Van and 1999 - some 2000 C/K Truck: with 4.3L, 5.0L, 5.7L engines and built prior to listed VIN/Production dates on Service Bulletin 00-06-04-018: If diagnosis leads to sticking poppet nozzles on these models, use the service procedure from Service Bulletin 00-06-04-018 to replace the fuel tank fill pipe assembly, if this procedure has not been performed previously. Previous service procedure can be verified by checking GMVIS for Labor Operation L1065 on "M/L" trucks with replacement part number 15050573; or Labor Operation L1065 on "C/K" trucks with replacement part numbers 15747585 or 15747588. Correction: If, after cleaning the SCPI poppet nozzles, the normal service manual diagnosis still indicates that the SCPI is the cause of the customer complaint, or if the injectors have previously been cleaned and the vehicle has again experienced sticking poppet nozzles, refer to Service Bulletin 00-06-04-003B and replace the SCPI fuel assembly with the MFI fuel assembly. Please note that the service bulletin term for SCPI is Central Sequential Fuel Injection (CSFI), but is referring to the same fuel system assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Hose > Component Information > Technical Service Bulletins > Recalls for Fuel Filler Hose: > 99066F > Mar > 03 > Campaign Fuel Injector Sticking Closed > Page 6280 CLAIM INFORMATION For vehicles repaired under this special policy, submit a claim with the information indicated. CUSTOMER REIMBURSEMENT Customer requests for reimbursement are for any previously paid repairs to, or replacement of, the Sequential Central Port Fuel Injection (SCPI) system. Repairs must have occurred within 10 years of the date the vehicle was originally placed in service, or 200,000 miles, whichever occurs first. The requests are to be submitted within two (2) years of the date on which the repair was paid or within two (2) years of the date of this Special Policy Bulletin, whichever is greater. When a customer requests reimbursement, they must provide the following: - Proof of ownership at time of repair. - Original paid receipt confirming the amount of unreimbursed repair expense(s) (including Service Contract deductibles), a description of the repair, and the person or entity performing the repair. Customers from the State of California, must submit requests for reimbursement directly to (Divisions) per instructions in the owner letter. If the work was done by someone other than a GM dealership, the amount of reimbursement will be limited to the amount that the repair would have cost GM to have it completed by a GM dealership. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Hose > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Filler Hose: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed Fuel Filler Hose: All Technical Service Bulletins Campaign - Fuel Injector Sticking Closed File In Section: 06-Engine Emissions Bulletin No.: 99066F Date: March, 2003 SPECIAL POLICY SUBJECT: 99066F - SPECIAL POLICY ADJUSTMENT - SEQUENTIAL CENTRAL PORT FUEL INJECTION (SCPI) FAILURES IN CALIFORNIA ONLY (YF5 EMISSION EQUIPPED) MODELS: CERTAIN 1996, 1997, 1998, 1999, 2000, 2001, 2002 S/T, M/L, C/K, G, P, W4/NPR TRUCKS AND 2003 NPR TRUCKS EQUIPPED WITH 4.3L (RPO L35 - VIN CODE W OR RPO LF6 - VIN CODE X), 5.0L (RPO L30 - VIN CODE M) OR 5.7L (RPO L31 - VIN CODE R) ENGINE AND CALIFORNIA EMISSION EQUIPPED (RPO YF5) This bulletin is being revised to add the 2002 and 2003 model years to the SCPI Special Policy on certain S/T, M/L, C/K, G, P and W4/NPR truck models. Please discard Special Policy Bulletin Number 99066E, dated February, 2003. CONDITION Some customers of 1996, 1997, 1998, 1999, 2000, 2001, 2002 model year S/T, M/L, C/K, G, P, W4/NPR trucks and 2003 NPR trucks, that are registered in California, equipped with 4.3L (RPO L35 and VIN Code W, or RPO LF6 and VIN Code X), 5.0L (RPO L30 and VIN Code M) or 5.7L (RPO L31 and VIN Code R) engine, and California emissions (RPO YF5), may experience a "Service Engine Soon" light, misfire, rough idle or hard start due to a deposit build-up on the Sequential Central Port Fuel Injector (SCPI) poppet valve(s). The deposit build-up may cause injector poppets to stick closed. Certain fuels have been found to interact with the SCPI system to cause the deposits. SPECIAL POLICY ADJUSTMENT This special policy covers the SCPI failure condition described above for a period of ten (10) years or 200,000 miles, whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership. The repairs will be made at no charge to the owner. This special policy applies ONLY to repairs requiring SCPI system servicing, injector cleaning and/or MFI assembly replacement of the SCPI system. The customer should not be charged for performing a system check when it is determined that the SCPI system is not the cause of a customer complaint (labor operation T5532 is provided to submit claims for such system checks). Any additional necessary diagnosis and repairs that are not related to the SCPI condition are not covered by this special policy. The customer should be informed that any further service that is not covered by new vehicle warranty will not be covered by this policy. VEHICLES INVOLVED Involved are certain 1996,1997,1998,1999, 2000, 2001, 2002 S/T, M/L, C/K, G, P, W4/NPR and 2003 NPR model vehicles, registered in California, equipped with 4.3L (RPO L35 - VIN Code W, or RPO LF6 - VIN Code X), 5.0L (RPO L30 - VIN Code M) or 5.7L (RPO L31 - VIN Code R) engine; and California emissions (RPO YF5). This Special Policy covers all vehicles within these model years, with these engine and emissions RPO's. PARTS INFORMATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Hose > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Filler Hose: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed > Page 6286 Parts required to complete this special policy are to be obtained from General Motors Service Parts Operations (GMSPO). Please refer to your "involved vehicles listing" prior to ordering parts. Normal orders should be placed on a DRO Daily Replenishment Order. In an emergency, parts should be ordered on a CSO = Customer Special Order. IMPORTANT: Isuzu Parts Ordering: In order to comply with the 10-digit Isuzu part numbering system, Isuzu dealers must add an "8" to the beginning and a "0" to the end of the listed 8-digit part numbers when ordering parts through AIPDN. CUSTOMER NOTIFICATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Hose > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Filler Hose: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed > Page 6287 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Hose > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Filler Hose: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed > Page 6288 Customers will be notified of this special policy on their vehicles by General Motors (see copy of typical customer letter included with this bulletin - actual divisional letter may vary slightly). SERVICE PROCEDURE System Check: Use strategy-based diagnoses listed in the front of the Driveability and Emissions section of the service manual. If the SCPI system is operating properly, inform the customer that the vehicle does not have the condition listed in the owner letter. If poor driveability conditions persist, inform the customer that any further diagnosis and repairs will be at their expense if the vehicle is outside the parameters of the new vehicle warranty. SCPI Injector Cleaning Procedure: If diagnosis leads to sticking poppet nozzles, use the service procedure from Service Bulletin 00-06-04-003B to clean the SCPI poppet nozzles. Please note that the service bulletin term for SCPI is Central Sequential Fuel Injection (CSFI), but is referring to the same fuel system assembly. If the poppet nozzles have previously been cleaned and the sticking condition has reoccurred, refer to the correction paragraph below. SCPI Fuel Tank Fill Pipe Assembly for 1997-99 M/L Van and 1999 - some 2000 C/K Truck: with 4.3L, 5.0L, 5.7L engines and built prior to listed VIN/Production dates on Service Bulletin 00-06-04-018: If diagnosis leads to sticking poppet nozzles on these models, use the service procedure from Service Bulletin 00-06-04-018 to replace the fuel tank fill pipe assembly, if this procedure has not been performed previously. Previous service procedure can be verified by checking GMVIS for Labor Operation L1065 on "M/L" trucks with replacement part number 15050573; or Labor Operation L1065 on "C/K" trucks with replacement part numbers 15747585 or 15747588. Correction: If, after cleaning the SCPI poppet nozzles, the normal service manual diagnosis still indicates that the SCPI is the cause of the customer complaint, or if the injectors have previously been cleaned and the vehicle has again experienced sticking poppet nozzles, refer to Service Bulletin 00-06-04-003B and replace the SCPI fuel assembly with the MFI fuel assembly. Please note that the service bulletin term for SCPI is Central Sequential Fuel Injection (CSFI), but is referring to the same fuel system assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Hose > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Filler Hose: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed > Page 6289 CLAIM INFORMATION For vehicles repaired under this special policy, submit a claim with the information indicated. CUSTOMER REIMBURSEMENT Customer requests for reimbursement are for any previously paid repairs to, or replacement of, the Sequential Central Port Fuel Injection (SCPI) system. Repairs must have occurred within 10 years of the date the vehicle was originally placed in service, or 200,000 miles, whichever occurs first. The requests are to be submitted within two (2) years of the date on which the repair was paid or within two (2) years of the date of this Special Policy Bulletin, whichever is greater. When a customer requests reimbursement, they must provide the following: - Proof of ownership at time of repair. - Original paid receipt confirming the amount of unreimbursed repair expense(s) (including Service Contract deductibles), a description of the repair, and the person or entity performing the repair. Customers from the State of California, must submit requests for reimbursement directly to (Divisions) per instructions in the owner letter. If the work was done by someone other than a GM dealership, the amount of reimbursement will be limited to the amount that the repair would have cost GM to have it completed by a GM dealership. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Hose > Component Information > Technical Service Bulletins > Page 6290 Fuel Filler Hose: Description and Operation To help prevent refueling with leaded fuel, the fuel filler neck has a built-in restrictor and deflector. The opening in the restrictor will accept only the smaller unleaded gasoline fuel nozzle which must be fully inserted to bypass the deflector. Attempted refueling with a leaded gas nozzle, or failure to fully insert the unleaded gas nozzle, will result in gasoline splashing back out of the filler neck. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Neck > Component Information > Technical Service Bulletins > Recalls for Fuel Filler Neck: > 99066F > Mar > 03 > Campaign Fuel Injector Sticking Closed Fuel Filler Neck: Recalls Campaign - Fuel Injector Sticking Closed File In Section: 06-Engine Emissions Bulletin No.: 99066F Date: March, 2003 SPECIAL POLICY SUBJECT: 99066F - SPECIAL POLICY ADJUSTMENT - SEQUENTIAL CENTRAL PORT FUEL INJECTION (SCPI) FAILURES IN CALIFORNIA ONLY (YF5 EMISSION EQUIPPED) MODELS: CERTAIN 1996, 1997, 1998, 1999, 2000, 2001, 2002 S/T, M/L, C/K, G, P, W4/NPR TRUCKS AND 2003 NPR TRUCKS EQUIPPED WITH 4.3L (RPO L35 - VIN CODE W OR RPO LF6 - VIN CODE X), 5.0L (RPO L30 - VIN CODE M) OR 5.7L (RPO L31 - VIN CODE R) ENGINE AND CALIFORNIA EMISSION EQUIPPED (RPO YF5) This bulletin is being revised to add the 2002 and 2003 model years to the SCPI Special Policy on certain S/T, M/L, C/K, G, P and W4/NPR truck models. Please discard Special Policy Bulletin Number 99066E, dated February, 2003. CONDITION Some customers of 1996, 1997, 1998, 1999, 2000, 2001, 2002 model year S/T, M/L, C/K, G, P, W4/NPR trucks and 2003 NPR trucks, that are registered in California, equipped with 4.3L (RPO L35 and VIN Code W, or RPO LF6 and VIN Code X), 5.0L (RPO L30 and VIN Code M) or 5.7L (RPO L31 and VIN Code R) engine, and California emissions (RPO YF5), may experience a "Service Engine Soon" light, misfire, rough idle or hard start due to a deposit build-up on the Sequential Central Port Fuel Injector (SCPI) poppet valve(s). The deposit build-up may cause injector poppets to stick closed. Certain fuels have been found to interact with the SCPI system to cause the deposits. SPECIAL POLICY ADJUSTMENT This special policy covers the SCPI failure condition described above for a period of ten (10) years or 200,000 miles, whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership. The repairs will be made at no charge to the owner. This special policy applies ONLY to repairs requiring SCPI system servicing, injector cleaning and/or MFI assembly replacement of the SCPI system. The customer should not be charged for performing a system check when it is determined that the SCPI system is not the cause of a customer complaint (labor operation T5532 is provided to submit claims for such system checks). Any additional necessary diagnosis and repairs that are not related to the SCPI condition are not covered by this special policy. The customer should be informed that any further service that is not covered by new vehicle warranty will not be covered by this policy. VEHICLES INVOLVED Involved are certain 1996,1997,1998,1999, 2000, 2001, 2002 S/T, M/L, C/K, G, P, W4/NPR and 2003 NPR model vehicles, registered in California, equipped with 4.3L (RPO L35 - VIN Code W, or RPO LF6 - VIN Code X), 5.0L (RPO L30 - VIN Code M) or 5.7L (RPO L31 - VIN Code R) engine; and California emissions (RPO YF5). This Special Policy covers all vehicles within these model years, with these engine and emissions RPO's. PARTS INFORMATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Neck > Component Information > Technical Service Bulletins > Recalls for Fuel Filler Neck: > 99066F > Mar > 03 > Campaign Fuel Injector Sticking Closed > Page 6299 Parts required to complete this special policy are to be obtained from General Motors Service Parts Operations (GMSPO). Please refer to your "involved vehicles listing" prior to ordering parts. Normal orders should be placed on a DRO Daily Replenishment Order. In an emergency, parts should be ordered on a CSO = Customer Special Order. IMPORTANT: Isuzu Parts Ordering: In order to comply with the 10-digit Isuzu part numbering system, Isuzu dealers must add an "8" to the beginning and a "0" to the end of the listed 8-digit part numbers when ordering parts through AIPDN. CUSTOMER NOTIFICATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Neck > Component Information > Technical Service Bulletins > Recalls for Fuel Filler Neck: > 99066F > Mar > 03 > Campaign Fuel Injector Sticking Closed > Page 6300 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Neck > Component Information > Technical Service Bulletins > Recalls for Fuel Filler Neck: > 99066F > Mar > 03 > Campaign Fuel Injector Sticking Closed > Page 6301 Customers will be notified of this special policy on their vehicles by General Motors (see copy of typical customer letter included with this bulletin - actual divisional letter may vary slightly). SERVICE PROCEDURE System Check: Use strategy-based diagnoses listed in the front of the Driveability and Emissions section of the service manual. If the SCPI system is operating properly, inform the customer that the vehicle does not have the condition listed in the owner letter. If poor driveability conditions persist, inform the customer that any further diagnosis and repairs will be at their expense if the vehicle is outside the parameters of the new vehicle warranty. SCPI Injector Cleaning Procedure: If diagnosis leads to sticking poppet nozzles, use the service procedure from Service Bulletin 00-06-04-003B to clean the SCPI poppet nozzles. Please note that the service bulletin term for SCPI is Central Sequential Fuel Injection (CSFI), but is referring to the same fuel system assembly. If the poppet nozzles have previously been cleaned and the sticking condition has reoccurred, refer to the correction paragraph below. SCPI Fuel Tank Fill Pipe Assembly for 1997-99 M/L Van and 1999 - some 2000 C/K Truck: with 4.3L, 5.0L, 5.7L engines and built prior to listed VIN/Production dates on Service Bulletin 00-06-04-018: If diagnosis leads to sticking poppet nozzles on these models, use the service procedure from Service Bulletin 00-06-04-018 to replace the fuel tank fill pipe assembly, if this procedure has not been performed previously. Previous service procedure can be verified by checking GMVIS for Labor Operation L1065 on "M/L" trucks with replacement part number 15050573; or Labor Operation L1065 on "C/K" trucks with replacement part numbers 15747585 or 15747588. Correction: If, after cleaning the SCPI poppet nozzles, the normal service manual diagnosis still indicates that the SCPI is the cause of the customer complaint, or if the injectors have previously been cleaned and the vehicle has again experienced sticking poppet nozzles, refer to Service Bulletin 00-06-04-003B and replace the SCPI fuel assembly with the MFI fuel assembly. Please note that the service bulletin term for SCPI is Central Sequential Fuel Injection (CSFI), but is referring to the same fuel system assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Neck > Component Information > Technical Service Bulletins > Recalls for Fuel Filler Neck: > 99066F > Mar > 03 > Campaign Fuel Injector Sticking Closed > Page 6302 CLAIM INFORMATION For vehicles repaired under this special policy, submit a claim with the information indicated. CUSTOMER REIMBURSEMENT Customer requests for reimbursement are for any previously paid repairs to, or replacement of, the Sequential Central Port Fuel Injection (SCPI) system. Repairs must have occurred within 10 years of the date the vehicle was originally placed in service, or 200,000 miles, whichever occurs first. The requests are to be submitted within two (2) years of the date on which the repair was paid or within two (2) years of the date of this Special Policy Bulletin, whichever is greater. When a customer requests reimbursement, they must provide the following: - Proof of ownership at time of repair. - Original paid receipt confirming the amount of unreimbursed repair expense(s) (including Service Contract deductibles), a description of the repair, and the person or entity performing the repair. Customers from the State of California, must submit requests for reimbursement directly to (Divisions) per instructions in the owner letter. If the work was done by someone other than a GM dealership, the amount of reimbursement will be limited to the amount that the repair would have cost GM to have it completed by a GM dealership. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Neck > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Filler Neck: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed Fuel Filler Neck: All Technical Service Bulletins Campaign - Fuel Injector Sticking Closed File In Section: 06-Engine Emissions Bulletin No.: 99066F Date: March, 2003 SPECIAL POLICY SUBJECT: 99066F - SPECIAL POLICY ADJUSTMENT - SEQUENTIAL CENTRAL PORT FUEL INJECTION (SCPI) FAILURES IN CALIFORNIA ONLY (YF5 EMISSION EQUIPPED) MODELS: CERTAIN 1996, 1997, 1998, 1999, 2000, 2001, 2002 S/T, M/L, C/K, G, P, W4/NPR TRUCKS AND 2003 NPR TRUCKS EQUIPPED WITH 4.3L (RPO L35 - VIN CODE W OR RPO LF6 - VIN CODE X), 5.0L (RPO L30 - VIN CODE M) OR 5.7L (RPO L31 - VIN CODE R) ENGINE AND CALIFORNIA EMISSION EQUIPPED (RPO YF5) This bulletin is being revised to add the 2002 and 2003 model years to the SCPI Special Policy on certain S/T, M/L, C/K, G, P and W4/NPR truck models. Please discard Special Policy Bulletin Number 99066E, dated February, 2003. CONDITION Some customers of 1996, 1997, 1998, 1999, 2000, 2001, 2002 model year S/T, M/L, C/K, G, P, W4/NPR trucks and 2003 NPR trucks, that are registered in California, equipped with 4.3L (RPO L35 and VIN Code W, or RPO LF6 and VIN Code X), 5.0L (RPO L30 and VIN Code M) or 5.7L (RPO L31 and VIN Code R) engine, and California emissions (RPO YF5), may experience a "Service Engine Soon" light, misfire, rough idle or hard start due to a deposit build-up on the Sequential Central Port Fuel Injector (SCPI) poppet valve(s). The deposit build-up may cause injector poppets to stick closed. Certain fuels have been found to interact with the SCPI system to cause the deposits. SPECIAL POLICY ADJUSTMENT This special policy covers the SCPI failure condition described above for a period of ten (10) years or 200,000 miles, whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership. The repairs will be made at no charge to the owner. This special policy applies ONLY to repairs requiring SCPI system servicing, injector cleaning and/or MFI assembly replacement of the SCPI system. The customer should not be charged for performing a system check when it is determined that the SCPI system is not the cause of a customer complaint (labor operation T5532 is provided to submit claims for such system checks). Any additional necessary diagnosis and repairs that are not related to the SCPI condition are not covered by this special policy. The customer should be informed that any further service that is not covered by new vehicle warranty will not be covered by this policy. VEHICLES INVOLVED Involved are certain 1996,1997,1998,1999, 2000, 2001, 2002 S/T, M/L, C/K, G, P, W4/NPR and 2003 NPR model vehicles, registered in California, equipped with 4.3L (RPO L35 - VIN Code W, or RPO LF6 - VIN Code X), 5.0L (RPO L30 - VIN Code M) or 5.7L (RPO L31 - VIN Code R) engine; and California emissions (RPO YF5). This Special Policy covers all vehicles within these model years, with these engine and emissions RPO's. PARTS INFORMATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Neck > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Filler Neck: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed > Page 6308 Parts required to complete this special policy are to be obtained from General Motors Service Parts Operations (GMSPO). Please refer to your "involved vehicles listing" prior to ordering parts. Normal orders should be placed on a DRO Daily Replenishment Order. In an emergency, parts should be ordered on a CSO = Customer Special Order. IMPORTANT: Isuzu Parts Ordering: In order to comply with the 10-digit Isuzu part numbering system, Isuzu dealers must add an "8" to the beginning and a "0" to the end of the listed 8-digit part numbers when ordering parts through AIPDN. CUSTOMER NOTIFICATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Neck > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Filler Neck: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed > Page 6309 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Neck > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Filler Neck: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed > Page 6310 Customers will be notified of this special policy on their vehicles by General Motors (see copy of typical customer letter included with this bulletin - actual divisional letter may vary slightly). SERVICE PROCEDURE System Check: Use strategy-based diagnoses listed in the front of the Driveability and Emissions section of the service manual. If the SCPI system is operating properly, inform the customer that the vehicle does not have the condition listed in the owner letter. If poor driveability conditions persist, inform the customer that any further diagnosis and repairs will be at their expense if the vehicle is outside the parameters of the new vehicle warranty. SCPI Injector Cleaning Procedure: If diagnosis leads to sticking poppet nozzles, use the service procedure from Service Bulletin 00-06-04-003B to clean the SCPI poppet nozzles. Please note that the service bulletin term for SCPI is Central Sequential Fuel Injection (CSFI), but is referring to the same fuel system assembly. If the poppet nozzles have previously been cleaned and the sticking condition has reoccurred, refer to the correction paragraph below. SCPI Fuel Tank Fill Pipe Assembly for 1997-99 M/L Van and 1999 - some 2000 C/K Truck: with 4.3L, 5.0L, 5.7L engines and built prior to listed VIN/Production dates on Service Bulletin 00-06-04-018: If diagnosis leads to sticking poppet nozzles on these models, use the service procedure from Service Bulletin 00-06-04-018 to replace the fuel tank fill pipe assembly, if this procedure has not been performed previously. Previous service procedure can be verified by checking GMVIS for Labor Operation L1065 on "M/L" trucks with replacement part number 15050573; or Labor Operation L1065 on "C/K" trucks with replacement part numbers 15747585 or 15747588. Correction: If, after cleaning the SCPI poppet nozzles, the normal service manual diagnosis still indicates that the SCPI is the cause of the customer complaint, or if the injectors have previously been cleaned and the vehicle has again experienced sticking poppet nozzles, refer to Service Bulletin 00-06-04-003B and replace the SCPI fuel assembly with the MFI fuel assembly. Please note that the service bulletin term for SCPI is Central Sequential Fuel Injection (CSFI), but is referring to the same fuel system assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Filler Neck > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Filler Neck: > 99066F > Mar > 03 > Campaign - Fuel Injector Sticking Closed > Page 6311 CLAIM INFORMATION For vehicles repaired under this special policy, submit a claim with the information indicated. CUSTOMER REIMBURSEMENT Customer requests for reimbursement are for any previously paid repairs to, or replacement of, the Sequential Central Port Fuel Injection (SCPI) system. Repairs must have occurred within 10 years of the date the vehicle was originally placed in service, or 200,000 miles, whichever occurs first. The requests are to be submitted within two (2) years of the date on which the repair was paid or within two (2) years of the date of this Special Policy Bulletin, whichever is greater. When a customer requests reimbursement, they must provide the following: - Proof of ownership at time of repair. - Original paid receipt confirming the amount of unreimbursed repair expense(s) (including Service Contract deductibles), a description of the repair, and the person or entity performing the repair. Customers from the State of California, must submit requests for reimbursement directly to (Divisions) per instructions in the owner letter. If the work was done by someone other than a GM dealership, the amount of reimbursement will be limited to the amount that the repair would have cost GM to have it completed by a GM dealership. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Customer Interest for Fuel Gauge Sender: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not Fuel Gauge Sender: Customer Interest Instruments - Fuel Gauge Indicates Empty When Not File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-03A Date: June, 1998 Subject: Fuel Gauge Indicates Empty with 7-8 Gallons (30 Liters) Left in Tank (Replace Fuel Level Sensor Float Arm Assembly) Models: 1995-97 Chevrolet and GMC C/K 4 Door Models Built Prior to VIN Breakpoints: Models VIN Breakpoints Chevrolet VJ355982 GMC VJ724930 This bulletin is being revised to change the labor operation number. Please discard Corporate Bulletin Number 76-83-03 (Section 8 - Chassis/Body Electrical). Condition Some owners may comment that the fuel gauge indicates empty after only going 200 to 250 miles, and they are only able to put approximately 23 gallons or less of fuel in the 30 gallon tank. Cause The Fuel Level Indication System was designed with excessive empty reserve. The Fuel Level Sender will be labeled with Broadcast code "TCB", (see Figure 1). Vehicles built after December 14, 1996, have the revised Float Arm Assembly. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Customer Interest for Fuel Gauge Sender: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not > Page 6320 Following the procedure described in Section 8A of the Service Manual, remove the Sender Assembly and replace the original Float and Arm with P/N 25312833 (see Figure 2). Reinstall the Sender Assembly and Tank. Parts Information P/N Description Qty 25312833 Float Kit, Fuel Level Sensor 1 The part is currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time L1225 Sender Use published Assembly, Fuel Labor Operation (Tank Unit) - Time Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Customer Interest for Fuel Gauge Sender: > 76-83-05 > Sep > 97 > Instruments - Excessive Fuel Gauge Fluctuation Fuel Gauge Sender: Customer Interest Instruments - Excessive Fuel Gauge Fluctuation File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-05 Date: September, 1997 Subject: Excessive Fuel Gauge Fluctuation (Install Fuel Level Damper Kit) Models: 1995-97 Chevrolet and GMC C/K 4 Door Utility Models Condition Some owners may comment about excessive fuel gauge needle fluctuation when making turns or braking with less than a half tank of fuel. Correction Install fuel level damper module kit P/N 12167652 following the procedure described on the instruction sheets included with the kit. Parts Information P/N Description Qty 12167652 Module Kit, Fuel Level Damper 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time N4844 Module, Anti-slosh - Install 0.8 hr Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Gauge Sender > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Gauge Sender: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not Fuel Gauge Sender: All Technical Service Bulletins Instruments - Fuel Gauge Indicates Empty When Not File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-03A Date: June, 1998 Subject: Fuel Gauge Indicates Empty with 7-8 Gallons (30 Liters) Left in Tank (Replace Fuel Level Sensor Float Arm Assembly) Models: 1995-97 Chevrolet and GMC C/K 4 Door Models Built Prior to VIN Breakpoints: Models VIN Breakpoints Chevrolet VJ355982 GMC VJ724930 This bulletin is being revised to change the labor operation number. Please discard Corporate Bulletin Number 76-83-03 (Section 8 - Chassis/Body Electrical). Condition Some owners may comment that the fuel gauge indicates empty after only going 200 to 250 miles, and they are only able to put approximately 23 gallons or less of fuel in the 30 gallon tank. Cause The Fuel Level Indication System was designed with excessive empty reserve. The Fuel Level Sender will be labeled with Broadcast code "TCB", (see Figure 1). Vehicles built after December 14, 1996, have the revised Float Arm Assembly. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Gauge Sender > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Gauge Sender: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not > Page 6330 Following the procedure described in Section 8A of the Service Manual, remove the Sender Assembly and replace the original Float and Arm with P/N 25312833 (see Figure 2). Reinstall the Sender Assembly and Tank. Parts Information P/N Description Qty 25312833 Float Kit, Fuel Level Sensor 1 The part is currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time L1225 Sender Use published Assembly, Fuel Labor Operation (Tank Unit) - Time Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Gauge Sender > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Gauge Sender: > 76-83-05 > Sep > 97 > Instruments - Excessive Fuel Gauge Fluctuation Fuel Gauge Sender: All Technical Service Bulletins Instruments - Excessive Fuel Gauge Fluctuation File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-05 Date: September, 1997 Subject: Excessive Fuel Gauge Fluctuation (Install Fuel Level Damper Kit) Models: 1995-97 Chevrolet and GMC C/K 4 Door Utility Models Condition Some owners may comment about excessive fuel gauge needle fluctuation when making turns or braking with less than a half tank of fuel. Correction Install fuel level damper module kit P/N 12167652 following the procedure described on the instruction sheets included with the kit. Parts Information P/N Description Qty 12167652 Module Kit, Fuel Level Damper 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time N4844 Module, Anti-slosh - Install 0.8 hr Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Page 6335 Fuel Gauge Sender: Locations In rear Fuel Tank Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Page 6336 Fuel Gage Sender (Auxiliary Fuel Tank) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank Unit > Component Information > Technical Service Bulletins > Customer Interest for Fuel Tank Unit: > 76-83-03A > Jun > 98 > Instruments Fuel Gauge Indicates Empty When Not Fuel Tank Unit: Customer Interest Instruments - Fuel Gauge Indicates Empty When Not File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-03A Date: June, 1998 Subject: Fuel Gauge Indicates Empty with 7-8 Gallons (30 Liters) Left in Tank (Replace Fuel Level Sensor Float Arm Assembly) Models: 1995-97 Chevrolet and GMC C/K 4 Door Models Built Prior to VIN Breakpoints: Models VIN Breakpoints Chevrolet VJ355982 GMC VJ724930 This bulletin is being revised to change the labor operation number. Please discard Corporate Bulletin Number 76-83-03 (Section 8 - Chassis/Body Electrical). Condition Some owners may comment that the fuel gauge indicates empty after only going 200 to 250 miles, and they are only able to put approximately 23 gallons or less of fuel in the 30 gallon tank. Cause The Fuel Level Indication System was designed with excessive empty reserve. The Fuel Level Sender will be labeled with Broadcast code "TCB", (see Figure 1). Vehicles built after December 14, 1996, have the revised Float Arm Assembly. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank Unit > Component Information > Technical Service Bulletins > Customer Interest for Fuel Tank Unit: > 76-83-03A > Jun > 98 > Instruments Fuel Gauge Indicates Empty When Not > Page 6345 Following the procedure described in Section 8A of the Service Manual, remove the Sender Assembly and replace the original Float and Arm with P/N 25312833 (see Figure 2). Reinstall the Sender Assembly and Tank. Parts Information P/N Description Qty 25312833 Float Kit, Fuel Level Sensor 1 The part is currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time L1225 Sender Use published Assembly, Fuel Labor Operation (Tank Unit) - Time Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank Unit > Component Information > Technical Service Bulletins > Customer Interest for Fuel Tank Unit: > 76-83-05 > Sep > 97 > Instruments Excessive Fuel Gauge Fluctuation Fuel Tank Unit: Customer Interest Instruments - Excessive Fuel Gauge Fluctuation File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-05 Date: September, 1997 Subject: Excessive Fuel Gauge Fluctuation (Install Fuel Level Damper Kit) Models: 1995-97 Chevrolet and GMC C/K 4 Door Utility Models Condition Some owners may comment about excessive fuel gauge needle fluctuation when making turns or braking with less than a half tank of fuel. Correction Install fuel level damper module kit P/N 12167652 following the procedure described on the instruction sheets included with the kit. Parts Information P/N Description Qty 12167652 Module Kit, Fuel Level Damper 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time N4844 Module, Anti-slosh - Install 0.8 hr Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank Unit > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Tank Unit: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not Fuel Tank Unit: All Technical Service Bulletins Instruments - Fuel Gauge Indicates Empty When Not File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-03A Date: June, 1998 Subject: Fuel Gauge Indicates Empty with 7-8 Gallons (30 Liters) Left in Tank (Replace Fuel Level Sensor Float Arm Assembly) Models: 1995-97 Chevrolet and GMC C/K 4 Door Models Built Prior to VIN Breakpoints: Models VIN Breakpoints Chevrolet VJ355982 GMC VJ724930 This bulletin is being revised to change the labor operation number. Please discard Corporate Bulletin Number 76-83-03 (Section 8 - Chassis/Body Electrical). Condition Some owners may comment that the fuel gauge indicates empty after only going 200 to 250 miles, and they are only able to put approximately 23 gallons or less of fuel in the 30 gallon tank. Cause The Fuel Level Indication System was designed with excessive empty reserve. The Fuel Level Sender will be labeled with Broadcast code "TCB", (see Figure 1). Vehicles built after December 14, 1996, have the revised Float Arm Assembly. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank Unit > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Tank Unit: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not > Page 6355 Following the procedure described in Section 8A of the Service Manual, remove the Sender Assembly and replace the original Float and Arm with P/N 25312833 (see Figure 2). Reinstall the Sender Assembly and Tank. Parts Information P/N Description Qty 25312833 Float Kit, Fuel Level Sensor 1 The part is currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time L1225 Sender Use published Assembly, Fuel Labor Operation (Tank Unit) - Time Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank Unit > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Tank Unit: > 76-83-05 > Sep > 97 > Instruments - Excessive Fuel Gauge Fluctuation Fuel Tank Unit: All Technical Service Bulletins Instruments - Excessive Fuel Gauge Fluctuation File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-05 Date: September, 1997 Subject: Excessive Fuel Gauge Fluctuation (Install Fuel Level Damper Kit) Models: 1995-97 Chevrolet and GMC C/K 4 Door Utility Models Condition Some owners may comment about excessive fuel gauge needle fluctuation when making turns or braking with less than a half tank of fuel. Correction Install fuel level damper module kit P/N 12167652 following the procedure described on the instruction sheets included with the kit. Parts Information P/N Description Qty 12167652 Module Kit, Fuel Level Damper 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time N4844 Module, Anti-slosh - Install 0.8 hr Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank Unit > Component Information > Technical Service Bulletins > Page 6360 Fuel Tank Unit: Description and Operation The fuel sender assembly is located inside the fuel tank and attaches to the top of the fuel tank. The fuel sender assembly consists of the following major components: - The fuel sender. - The fuel pump. - The fuel pump strainer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank Unit > Component Information > Service and Repair > Remove and Install Fuel Tank Unit: Service and Repair Remove and Install REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Relieve the fuel system pressure. Refer to Fuel Pressure Relief Procedure. See: Service and Repair 3. Drain the fuel tank. Refer to Draining Fuel Tank. See: Fuel Tank/Service and Repair 4. Remove the fuel tank and sender assembly. Refer to Fuel Tank Assembly. See: Fuel Tank/Service and Repair INSTALLATION PROCEDURE 1. Install a new seal, sending assembly and lock ring. Make sure the lock ring alignment holes fit over the tabs on the tank. 2. Install the cam lock assembly. Turn the cam lock clockwise to lock it. 3. Install the fuel tank. Refer to Fuel Tank Assembly. See: Fuel Tank/Service and Repair 4. Add fuel removed from the tank. 5. Connect the negative battery cable. 6. Check for fuel leaks. 6.1. Turn the ignition ON for 2 seconds. 6.2. Turn OFF the ignition for 10 seconds. 6.3. Again, turn the ignition switch to the ON position. 6.4. Check for fuel leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Fuel Tank Unit > Component Information > Service and Repair > Remove and Install > Page 6363 Fuel Tank Unit: Service and Repair Disassemble and Assemble DISASSEMBLE PROCEDURE 1. Note the position of the fuel pump strainer on the fuel pump. 2. Support the pump with one hand and grasp the strainer with the other hand. 3. Rotate the strainer in one direction and pull off the pump. Discard the strainer after inspection. 4. Inspect the fuel pump strainer. Replace the strainer if it has contaminates and clean the fuel tank. 5. Inspect the fuel pump inlet for dirt and debris. If found, replace the pump. ASSEMBLE PROCEDURE NOTE: Do not fold or twist the strainer when installing the sending unit. This action restricts fuel flow. 1. Push on the outer edge of the ferrule until fully seated. 2. Support the pump with one hand and position the new pump strainer on pump in the same position as noted during disassembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Specifications Idle Air Control (IAC) Valve: Specifications IAC valve attaching screws ................................................................................................................. ..................................................... 3.0 Nm (26 lb. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Specifications > Page 6367 Engine Side, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions Idle Air Control (IAC) Valve: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6370 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6371 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6372 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6373 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6374 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6375 Idle Air Control (IAC) Valve: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6376 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6377 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6378 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6379 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6380 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6381 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6382 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6383 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6384 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6385 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6386 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6387 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6388 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6389 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6390 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6391 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6392 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6393 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6394 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6395 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6396 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6397 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6398 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6399 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6400 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6401 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Diagram Information and Instructions > Page 6402 Idle Control System Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Page 6403 Idle Air Control (IAC) Valve: Description and Operation PURPOSE The purpose of the Idle Air Control (IAC) valve assembly is to control the engine idle speed, while preventing stalls due to changes in the engine load. OPERATION The IAC valve, mounted in the throttle body assembly, controls the bypass air around the throttle valve. By moving a conical valve known as a pintle IN toward the seat (to decrease air flow), or OUT away from the seat (to increase air flow), a controlled amount of air moves around the throttle valve. If engine speed is too low, more air is bypassed around the throttle valve in order to increase the RPM. If the engine speed is too high, less air is bypassed around the throttle valve in order to decrease the RPM. The VCM moves the IAC valve in small steps, called counts which can be measured using a scan tool connected to the Data Link Connector (DLC). During idle, the proper position of the IAC valve is calculated by the VCM. This position is based on battery voltage, engine coolant temperature, engine load, and engine RPM. If the RPM drops below specification and the throttle valve is closed, the VCM senses a near stall condition, and then the VCM calculates a new valve position in order to prevent stalling. If the IAC valve is disconnected and reconnected while the engine is running, the resulting idle RPM may be wrong. This will require the resetting of the IAC valve. After running the engine, the IAC valve will reset when the ignition is turned OFF. When servicing the IAC valve, it should only be disconnected or connected with the ignition OFF. If the VCM is without battery power for any reason, the programmed position of the IAC valve pintle is lost. The control module replaces the lost position with a default value. In order to return the IAC valve pintle to the correct position, see the Idle Learn Procedure. The IAC valve affects the idle characteristics of the vehicle. A fully retracted valve allows too much air into the manifold causing a high idle speed. A valve which is stuck closed allows too little air in the manifold, causing a low idle speed. If the valve is stuck part way open, the idle may be rough, and the idle will not respond to engine load changes. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Diagrams > Page 6404 Idle Air Control (IAC) Valve: Testing and Inspection If the Idle Air Control (IAC) valve is disconnected or connected when the engine is running, the idle RPM may be wrong. The IAC valve may be reset by turning the ignition switch ON for 10 seconds, OFF for 5 seconds. The IAC valve affects the idle characteristics of the engine as well as throttle follow-up to compensation for sudden throttle closing. If it is open fully too much air will be allowed in the manifold and idle speed will be high. If it is stuck closed, too little air will be allowed in the manifold, and idle speed will be too low. If it is stuck part way open, the idle may be rough, and will not respond to engine load changes. The diagnosis of Idle Air Control (IAC) can be found in VCM Outputs Diagnosis. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Service and Repair > Idle Air Control (IAC) Reset Procedure Idle Air Control (IAC) Valve: Service and Repair Idle Air Control (IAC) Reset Procedure 1. Turn the ignition switch to the ON position for 5 seconds. 2. Turn the ignition switch to the OFF position for 10 seconds. 3. Start the engine. 4. Check for the proper idle operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Service and Repair > Idle Air Control (IAC) Reset Procedure > Page 6407 Idle Air Control (IAC) Valve: Service and Repair Idle Air Control (IAC) Valve Replacement Throttle Position Sensor Electrical Connector REMOVAL PROCEDURE 1. Remove the electrical connector from the Idle Air Control (IAC) valve Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Idle Air Control (IAC) Valve <--> [Idle Speed/Throttle Actuator - Electronic] > Component Information > Service and Repair > Idle Air Control (IAC) Reset Procedure > Page 6408 2. Remove the IAC valve attaching screws. CAUTION: If the IAC valve has been in service: DO NOT push or pull on the IAC valve pintle. The force required to move the pintle may damage the threads on the worm drive. Also, DO NOT soak the IAC valve in any liquid cleaner or solvent, as damage may result. 3. Remove the IAC valve assembly. 4. Remove the O-ring. CLEANING AND INSPECTION PROCEDURE 1. Clean the IAC valve O-ring sealing surface, pintle valve seat, and air passage. ^ Use the carburetor cleaner and a parts cleaning brush in order to remove carbon deposits. Follow instructions on the container. ^ Do not use a cleaner that contains methyl ethyl ketone, an extremely strong solvent and not necessary for this type of deposit. ^ Shiny spots on the pintle or seat are normal. They do not indicate misalignment or a bent pintle shaft. ^ If air passage has heavy deposits, remove the throttle body for complete cleaning. 2. Inspect the IAC valve O-ring for cuts, cracks, or distortion. Replace if damaged. NOTE: If installing a new IAC valve, replace with an identical part. The IAC valve pintle shape and diameter are designed for the specific application. 3. Measure the distance A between tip of IAC valve pintle and mounting flange. If greater than 28 mm, use finger pressure in order to slowly retract the pintle. The force required to retract the pintle of a new valve will not cause damage to the valve. MEASUREMENT PROCEDURE NOTE: If installing a new IAC valve, replace with an identical part. The AC valve pintle shape and diameter are designed for the specific application. Measure the distance A between tip of IAC valve pintle and mounting flange. If greater than 28 mm, use finger pressure in order to slowly retract the pintle. The force required to retract the pintle of a new valve will not cause damage to the valve. INSTALLATION PROCEDURE 2. Lubricate the IAC valve O-ring with clean engine oil. 2. Install the IAC valve assembly. 3. Install the attaching screws. Tighten ^ Tighten the IAC valve attaching screws to 3.0 Nm (26 lb. in.). 4. Install the electrical connector. 5. Reset the IAC valve pintle position. 5.1.Turn the ignition switch to the ON position for 5 seconds. 5.2.Turn the ignition switch to the OFF position for 10 seconds. 5.3.Start the engine. 5.4.Check for the proper idle operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Fuel Pump Oil Pressure Switch and Sender Engine View, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Fuel Pump Oil Pressure Switch and Sender > Page 6413 Oil Pressure Switch (For Fuel Pump): Locations Oil Pressure Switch and Sender LH side of Engine, rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Page 6414 Fuel Pump Oil Pressure Switch And Sender Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Page 6415 Oil Pressure Switch (For Fuel Pump): Service and Repair Oil Pressure Switch Electrical Connector Oil Pressure Switch REMOVAL PROCEDURE 1. Remove the electrical connector. 2. Remove the fuel pump and oil pressure indicator switch, using wrench J 35748 it required. INSTALLATION PROCEDURE 1. Install the fuel pump and oil pressure indicator switch. 2. Install the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Locations Fuel Pump Balance Module: Locations FUEL PUMP BALANCE MODULE (Vehicles with Dual Tanks Only) On vehicles over 15,000 GVWR and equipped with dual fuel tanks, the Fuel Pump Balance Module is located inside the left frame rail, near Transmission Crossmember. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Locations > Page 6420 Fuel Pump Balance Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Locations > Page 6421 Fuel Pump Balance Module: Description and Operation FUEL BALANCE CONTROL SYSTEM The fuel balance control system consists of the following components: - Front (main) fuel tank sender. - Rear (auxiliary) fuel tank sender. - Balance fuel pump. - Balance fuel pump relay. - Fuel sender and balance module. On vehicles with dual tanks, the front tank is the main and the rear tank is the auxiliary. The main fuel pump supplies fuel to the fuel injection unit. The low pressure (about 32 kPa or 7 psi) fuel balance pump is used only to transfer fuel from the auxiliary tank to the main tank in order to balance the fuel levels in both tanks. As the main tank level drops to about 25 % below the level in the auxiliary tank, the fuel sender and balance module energizes the fuel pump relay. This pumps the fuel from the auxiliary tank to the main tank. When the level in the main tank reaches a level slightly higher than the level in the auxiliary tank, or the auxiliary tank is empty, the module de-energizes the balance pump relay and fuel pump. Any malfunction in either of the fuel gage circuits will disable the system and the fuel will not be transferred from the main fuel tank to the auxiliary fuel tank. FUEL PUMP BALANCE MODULE The Fuel Pump Balance Module relies on input from the primary and secondary fuel senders, and cannot operate if the fuel gauge is not working properly. For Fuel Pump Balance Module testing and inspection refer to Instrument Panel, Gauges and Warning Indicators / Symptom Releated Diagnostic Procedures / Fuel Gauge See: Instrument Panel, Gauges and Warning Indicators/Testing and Inspection/Symptom Related Diagnostic Procedures For Fuel Pump Balance Module electrical diagrams refer to Instrument Panel, Gauges and Warning Indicators / Diagrams / Electrical. See: Instrument Panel, Gauges and Warning Indicators/Diagrams Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times Fuel Gage Indicates Empty At All Times Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times > Page 6424 Fuel Gage Indicates Full At All Times Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times > Page 6425 Fuel Pump Balance Module: Testing and Inspection Fuel Gage Is Inaccurate Fuel Gage Is Inaccurate (Part 1 Of 2) Fuel Gage Is Inaccurate (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times > Page 6426 Fuel Pump Balance Module: Testing and Inspection Vehicle Runs Out of Fuel (Rear Tank Not Empty) Vehicle Runs Out Of Fuel At Half-Full/rear Tank Is Full At All Times (Part 1 Of 2) Vehicle Runs Out Of Fuel At Half-Full/rear Tank Is Full At All Times (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Fuel Gage Indicates Empty at All Times > Page 6427 Fuel Gage Does Not Change Position On Scale Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Page 6428 Fuel Pump Balance Module: Service and Repair REMOVAL PROCEDURE WARNING: To reduce the risk of fire and personal in jury that may result from a fuel leak, always replace O-ring seals exposed during component service. 1. Disconnect the negative battery cable. 2. Loosen the filler cap(s) to Relieve fuel tank pressure. See: Service and Repair 3. Disconnect the electrical connector. 4. Clean both fuel pipe connections and surrounding areas at the fuel pump before disconnecting to avoid possible contamination of the fuel system. 5. Disconnect both fuel pipes from the pump. 6. Slide the pump out of the bracket. INSTALLATION PROCEDURE 1. Install the new fuel pipe O-rings. 2. Position the new pump in the pump bracket. 3. Connect the fuel feed pipe and suction pipe to the fuel pump. Tighten Use a backup wrench to prevent the pump from turning. Tighten the fittings to 3O Nm (22 lb. ft.). 4. Connect the electrical connector. 5. Connect the negative battery cable. 6. Check for fuel leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Balance Module <--> [Fuel Pump Control Unit] > Component Information > Testing and Inspection > Page 6429 6.1. Turn the ignition ON for 2 seconds. 6.2. Turn OFF the ignition for 10 seconds. 6.3. Again, turn the ignition switch to the ON position. 6.4. Check for fuel leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Locations > Fuel Pump Relay Fuel Pump Relay: Locations Fuel Pump Relay FUEL PUMP RELAY Auxiliary Battery Wiring Underhood Fuse-Relay Center The Fuel Pump Relay is located in Underhood Fuse Relay Center. The Underhood Fuse Relay Center is located on the LH rear of engine compartment, on fender. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Locations > Fuel Pump Relay > Page 6434 Fuel Pump Relay: Locations Fuel Pump Relay (Balance Pump) FUEL PUMP RELAY (BALANCE PUMP) (Vehicles with Dual Tanks Only) On vehicles over 15,000 GVWR and equipped with dual fuel tanks, the Fuel Pump Balance Relay is located inside the left frame rail, near Transmission Crossmember. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions Fuel Pump Relay: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6437 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6438 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6439 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6440 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6441 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6442 Fuel Pump Relay: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6443 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6444 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6445 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6446 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6447 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6448 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6449 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6450 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6451 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6452 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6453 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6454 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6455 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6456 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6457 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6458 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6459 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6460 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6461 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6462 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6463 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6464 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6465 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6466 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6467 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6468 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6469 Fuel Pump Relay: Connector Views Fuel Pump Balance Relay Fuel Pump Relay FUEL PUMP RELAY CONNECTOR VIEW Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Diagrams > Diagram Information and Instructions > Page 6470 Underhood Fuse-Relay Center (Part 1 Of 2) The Fuel Pump Relay is located in the Underhood Fuse-Relay Center. Refer to terminals, A1 - B1 B2 - A3 - B3. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Description and Operation > Fuel Pump Relay Operation Fuel Pump Relay: Description and Operation Fuel Pump Relay Operation OPERATION When the key is turned ON with out the engine running, the control module turns a fuel pump relay ON for two seconds. This builds up fuel pressure quickly. If the engine is not started within two seconds, the control module shuts the fuel pump OFF and waits until the engine starts. As soon as the engine is cranked, the control module turns the relay ON and runs the fuel pump. When the engine is cranking or running, the control module receives the Crankshaft Position (CKP) sensor reference pulses which in turn energize the fuel injectors. As a backup system to the fuel pump relay, the fuel pump can also be turned ON by a fuel pump oil pressure switch. When the engine reaches about 28 kPa (4 psi), and the fuel pump relay does not complete the circuit, the fuel pump oil pressure switch will close to complete the circuit to run the fuel pump. An inoperative fuel pump relay can result in long cranking times, particularly if the engine is cold. The fuel pump oil pressure switch will turn ON the fuel pump as soon as oil pressure reaches about 28 kPa (4 psi). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Description and Operation > Fuel Pump Relay Operation > Page 6473 Fuel Pump Relay: Description and Operation Fuel Balance Module Control System (Dual Tanks) FUEL BALANCE CONTROL SYSTEM The fuel balance control system consists of the following components: - Front (main) fuel tank sender. - Rear (auxiliary) fuel tank sender. - Balance fuel pump. - Balance fuel pump relay. - Fuel sender and balance module. On vehicles with dual tanks, the front tank is the main and the rear tank is the auxiliary. The main fuel pump supplies fuel to the fuel injection unit. The low pressure (about 32 kPa or 7 psi) fuel balance pump is used only to transfer fuel from the auxiliary tank to the main tank in order to balance the fuel levels in both tanks. As the main tank level drops to about 25 % below the level in the auxiliary tank, the fuel sender and balance module energizes the fuel pump relay. This pumps the fuel from the auxiliary tank to the main tank. When the level in the main tank reaches a level slightly higher than the level in the auxiliary tank, or the auxiliary tank is empty, the module de-energizes the balance pump relay and fuel pump. Any malfunction in either of the fuel gage circuits will disable the system and the fuel will not be transferred from the main fuel tank to the auxiliary fuel tank. FUEL PUMP BALANCE MODULE The Fuel Pump Balance Module relies on input from the primary and secondary fuel senders, and cannot operate if the fuel gauge is not working properly. For Fuel Pump Balance Module testing and inspection refer to Instrument Panel, Gauges and Warning Indicators / Symptom Releated Diagnostic Procedures / Fuel Gauge See: Instrument Panel, Gauges and Warning Indicators/Testing and Inspection/Symptom Related Diagnostic Procedures For Fuel Pump Balance Module electrical diagrams refer to Instrument Panel, Gauges and Warning Indicators / Diagrams / Electrical. See: Instrument Panel, Gauges and Warning Indicators/Diagrams Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Relays and Modules - Fuel Delivery and Air Induction > Fuel Pump Relay > Component Information > Description and Operation > Page 6474 Fuel Pump Relay: Service and Repair Removal Procedure 1. Remove the underhood electrical center cover. 2. Remove the relay. Installation Procedure 1. Install the relay. 2. Install the underhood electrical center cover. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions Mass Air Flow (MAF) Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6480 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6481 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6482 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6483 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6484 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6485 Mass Air Flow (MAF) Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6486 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6487 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6488 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6489 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6490 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6491 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6492 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6493 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6494 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6495 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6496 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6497 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6498 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6499 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6500 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6501 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6502 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6503 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6504 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6505 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6506 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6507 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6508 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6509 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6510 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6511 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Diagram Information and Instructions > Page 6512 Mass Air Flow System Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Page 6513 Mass Air Flow (MAF) Sensor: Description and Operation Mass Air Flow (MAF) Sensor The Mass Air Flow (MAF) sensor measures the amount of air which passes through it. The VCM uses this information to determine the operating condition of the engine, to control fuel delivery. A large quantity of air indicates acceleration. A small quantity of air indicates deceleration or idle. The scan tool reads the MAF value and displays it in grams per second (gm/Sec). At idle, it should read between 5-7 gm/Sec on a fully warmed up engine. Values should change rather quickly on acceleration, but values should remain fairly stable at any given RPM. When the VCM detects a malfunction in the MAF sensor circuit, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0101 system performance. ^ DTC P0102 frequency low. ^ DTC P0103 frequency high. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Mass Air Flow (MAF) Sensor <--> [Air Flow Meter/Sensor] > Component Information > Diagrams > Page 6514 Mass Air Flow (MAF) Sensor: Service and Repair MAF Sensor MAF Sensor Intake Duct REMOVAL PROCEDURE CAUTION: Take care when handling the Mass Air Flow (MAF). Do Not dent, puncture, or otherwise damage the honeywell located at the air inlet end of the MAF. Do Not touch the sensing elements or allow anything (including solvents and lubricants) to come in contact with them. A small amount of GM lubricant (P/N 99855406) may be used on the air duct only to aid in installation. Do Not drop or roughly handle the MAF. 1. Disconnect the 3 wire electrical connector. 2. Loosen the clamp on the intake duct. 3. Carefully remove the MAF sensor. INSTALLATION PROCEDURE 1. Install the MAF sensor. 2. Install the intake ducts. 3. Tighten the clamp. 4. Connect the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Fuel Pump Oil Pressure Switch and Sender Engine View, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Fuel Pump Oil Pressure Switch and Sender > Page 6519 Oil Pressure Switch (For Fuel Pump): Locations Oil Pressure Switch and Sender LH side of Engine, rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Page 6520 Fuel Pump Oil Pressure Switch And Sender Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Oil Pressure Switch (For Fuel Pump) > Component Information > Locations > Page 6521 Oil Pressure Switch (For Fuel Pump): Service and Repair Oil Pressure Switch Electrical Connector Oil Pressure Switch REMOVAL PROCEDURE 1. Remove the electrical connector. 2. Remove the fuel pump and oil pressure indicator switch, using wrench J 35748 it required. INSTALLATION PROCEDURE 1. Install the fuel pump and oil pressure indicator switch. 2. Install the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Specifications Throttle Position Sensor: Specifications Screw assemblies ................................................................................................................................ .................................................. 2.0 Nm (18.0 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Specifications > Page 6525 Engine Side, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Throttle Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6528 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6529 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6530 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6531 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6532 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6533 Throttle Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6534 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6535 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6536 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6537 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6538 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6539 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6540 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6541 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6542 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6543 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6544 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6545 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6546 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6547 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6548 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6549 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6550 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6551 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6552 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6553 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6554 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6555 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6556 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6557 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6558 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6559 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6560 TP Sensor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Page 6561 Throttle Position Sensor: Description and Operation Diagram The non-adjustable Throttle Position (TP) sensor is mounted on the throttle body assembly opposite the throttle lever. The TP sensor senses the throttle valve angle and relays that information to the VCM. Knowledge of throttle angle is one of the inputs needed by the VCM to generate the required injector control signals (pulses). For further information on replacement, refer to TP Sensor. See: Service and Repair Legend (1) Throttle Body Assembly. (2) IAC Valve Assembly 0-ring. (3) IAC Valve Assembly Attaching Screw. (4) Idle Air Control (IAC) Valve Assembly. (5) TP Sensor 0-ring (6) Throttle Position (TP) Sensor. (7) TP Sensor Attaching Screw. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Testing and Inspection > Throttle Position (TP) Sensor Throttle Position Sensor: Testing and Inspection Throttle Position (TP) Sensor When the VCM detects a malfunction with the Throttle Position (TP) sensor circuits, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0121 circuit performance ^ DTC P0122 circuit low. ^ DTC P0123 circuit high. ^ DTC P1121 intermittent circuit high. ^ DTC P1122 intermittent circuit low. Refer to Diagnostic Tables. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Testing and Inspection > Throttle Position (TP) Sensor > Page 6564 Throttle Position Sensor: Testing and Inspection Throttle Position Sensor Output This check should be performed when Throttle Position (TP) sensor attaching parts have been replaced. A scan tool can be used to read the TP signal output voltage. 1. Connect digital voltmeter J 39200 from TP sensor connector terminal B (BLk wire) to terminal C (DK Blue wire). Jumpers for terminal access can be made using terminals 1214836 and 12014837. 2. With ignition ON, engine stopped, the TP signal voltage should be less than 1.25V if more than 1.25V verify free throttle movement. If still more than 1.25V, replace TP sensor. 3. Remove the voltmeter and jumpers, reconnect the TP sensor connector to the sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Testing and Inspection > Page 6565 Throttle Position Sensor: Service and Repair Throttle Position Sensor Electrical Connector REMOVAL PROCEDURE CAUTION: The Throttle Position (TP) sensor is an electrical component. Do not soak the TP sensor in any liquid cleaner or solvent, as damage may result. 1. Remove the air cleaner and adapter. 2. Disconnect the electrical connector releasing locking tab. 3. Remove the two TP sensor attaching screw assemblies. 4. Remove the TP sensor from throttle body assembly. 5. Remove the TP sensor seal. INSTALLATION PROCEDURE 1. Install the TP sensor seal over throttle shaft. 2. With throttle valve closed, install the TP sensor on the throttle shaft. Rotate counterclockwise to align mounting holes. 3. Install the two TP sensor attaching screw assemblies. Tighten ^ Tighten the screw assemblies to 2.0 Nm (18.0 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Sensors and Switches - Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Testing and Inspection > Page 6566 4. Connect the electrical connector. 5. Install the air cleaner and adapter. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Body > Component Information > Specifications Throttle Body: Specifications Throttle body retaining bolt or stud ........................................................................................................................................................... 25 Nm (18 lb. in.) Air inlet duct retaining nut ....................................................................................... ................................................................................. 2.5 Nm (22 lb. in.) Fuel meter body attaching bolts .............................................................................................................................................................. 10.0 Nm (88 lb. in.) fuel pipe nuts ........................................................................................................ ................................................................................... 30.0 Nm (22 lb. ft.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Body > Component Information > Specifications > Page 6570 Throttle Body: Application and ID An 8 digit part identification number is stamped on the bottom of the throttle body casting. Refer to this number if servicing, or part replacement is required. While on-vehicle or off, clean the throttle bore and valve deposits using the carburetor cleaner and a parts cleaning brush. Follow the instructions on container. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Body > Component Information > Specifications > Page 6571 Throttle Body: Description and Operation Throttle Body Assembly DESCRIPTION The throttle body assembly is a downdraft design. The throttle body is mounted on the intake manifold plenum. The VCM uses the throttle body to control air flow into the engine, thereby, controlling engine output. The throttle valve within the throttle body is opened by the driver through the accelerator controls. During engine idle, the throttle valve is almost closed, and the Idle Air Control (IAC) valve handles the air flow control. The throttle body also provides the location for mounting the Throttle Position (TP) sensor. The throttle body also senses changes in the engine vacuum due to the throttle valve position. The vacuum ports are located at, above, or below the throttle valve in order to generate the vacuum signals needed by various components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Body > Component Information > Service and Repair > Throttle Body Cleaning Throttle Body: Service and Repair Throttle Body Cleaning CLEANING AND INSPECTION Removing the fuel meter body assembly from the engine requires removing the top portion of the intake manifold, called the upper manifold assembly and throttle body. An 8 digit part identification number is on a mylar label affixed to one of the fuel meter body assemblies. Refer to this number if servicing or part replacement is required. NOTE: Do not use a cleaner which contains methyl ethyl ketone. This extremely strong solvent is not necessary for this type of cleaning. Use a carburetor cleaner in order to remove deposits. Refer to the package instructions on the use of the product. NOTE: Cover the injector sockets in order to prevent dirt and other contaminants from entering the open fuel passages. - Before removal, the fuel meter body assembly may be cleaned with a spray type engine cleaner, GM X-3OA or the equivalent. - Follow the package instructions. - Do not soak fuel meter body assemblies in liquid cleaning solvent. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Body > Component Information > Service and Repair > Throttle Body Cleaning > Page 6574 Throttle Body: Service and Repair Throttle Body Assembly Removal and Replacement Throttle Position Sensor Electrical Connector Air Inlet Duct Fastener Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Body > Component Information > Service and Repair > Throttle Body Cleaning > Page 6575 SERVICE INFORMATION The throttle body assembly repair procedures cover component replacement with the unit on the vehicle. However, the throttle body replacement requires that the complete unit be removed from the engine. An 8 digit part identification number is stamped on the bottom of the throttle body casting. Refer to this number if servicing, or part replacement is required. While on-vehicle or off, clean the throttle bore and valve deposits using the carburetor cleaner and a parts cleaning brush. Follow the instructions on container. THREAD LOCKING COMPOUND WARNING: In precoating screws, do not use a higher strength locking compound than recommended. Doing so could make removing the screw extremely difficult or result in damaging the screw head. The service repair kits are supplied with a small vial of thread-locking compound with directions for use. If the material is not available, use Loctite 262 or the equivalent. Do not use a cleaner that contains methyl ethyl ketone, an extremely strong solvent, and not necessary for this type of deposit. The throttle body metal parts may be cleaned following the disassembly in a cold immersion-type cleaner such as GM X-55 or the equivalent. WARNING: Do not immerse the Throttle Position (TP) sensor and Idle Air Control (IAC) valve in any type of cleaner because they are electronic devices. REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Remove the air inlet duct fastener and the duct. 3. Remove the IAC valve and the TP sensor electrical connectors. 4. Remove the throttle and cruise control cables. 5. Remove the accelerator cable bracket nuts and the bracket. 6. Remove the throttle body retaining bolts or studs. 7. Remove the throttle body assembly. 8. Remove the flange gasket. 9. Discard the flange gasket. INSTALLATION PROCEDURE WARNING: In order to prevent damage to the sealing surfaces, carefully use sharp tools in cleaning the old gasket from the aluminum surfaces. 1. Clean the gasket surface on the intake manifold. 2. Install a new flange gasket. 3. Install the throttle body assembly. 4. Install the throttle body assembly retaining bolt or stud. Tighten Tighten the throttle body attaching bolt or stud to 25 Nm (18 lb. in.). NOTE: Make sure the throttle and cruise control linkage does not hold the throttle open. Refer to Accelerator Controls. See: Throttle Cable/Linkage/Service and Repair Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Body > Component Information > Service and Repair > Throttle Body Cleaning > Page 6576 5. Install the throttle and cruise control cables. 6. Install the accelerator cable bracket. 7. install the accelerator cable bracket nuts. 8. Install the IAC valve electrical connector. 9. Install the TP sensor electrical connector. 10. Install the air inlet duct and retaining nut. Tighten Tighten the nut to 2.5 Nm (22 lb. in.). 11. Connect the negative battery cable. 12. With the engine off, check to see that the accelerator pedal is free. 12.1. Depress the pedal to the floor. 12.2. Release the accelerator pedal. CONTROLLED IDLE SPEED There should be no DTCs displayed. The idle air control system has been checked. 1. Set the parking brake. 2. Block the drive wheels. 3. Connect a scan tool to the Data Link Connector (DLC) with the tool in the open mode. 4. Start the engine. 5. Bring the engine to the normal operating temperature. 6. Check for the correct state of PRNDL (R-D-L) switch position on the scan tool. 7. Check the specifications table for controlled idle speed and IAC valve pintle position (counts). Refer to Specifications. See: Idle Air Control (IAC) Valve/Service and Repair 8. If within specifications, the idle speed is being correctly controlled by the control module. 9. If not within specifications, refer to Symptoms. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Body > Component Information > Service and Repair > Throttle Body Cleaning > Page 6577 Throttle Body: Service and Repair Fuel Meter Body Assembly Fuel Feed And Return Hoses From Engine Fuel Pipes Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Body > Component Information > Service and Repair > Throttle Body Cleaning > Page 6578 REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Relieve the fuel system pressure. Refer to Fuel Pressure Relief Procedure. See: Service and Repair 3. Remove the electrical connector to the fuel meter body. 4. Remove the fuel feed and return hoses from engine fuel pipes. 5. Remove the upper manifold assembly. Refer to Engine Mechanical. NOTE: When disconnecting the poppet nozzles, remember the sequence in order to ensure correct poppet nozzle placement to each cylinder. 6. Squeeze the poppet nozzle locking tabs together while lifting the nozzle out of the casting socket. 7. Remove the fuel meter body from the bracket by releasing the lock tabs on the bracket. INSTALLATION PROCEDURE 1. Install the fuel meter body assembly in the intake manifold. Tighten Tighten the fuel meter body attaching bolts to 10.0 Nm (88 lb. in.). WARNING: In order to reduce the risk of fire and personal injury verify that the poppet nozzles are firmly seated and locked in their casting sockets. An unlocked poppet nozzle could work loose from its socket thus resulting in a fuel leak. 2. Push the fuel meter body into the bracket. Make sure all the tabs are locked into place. NOTE: The fuel meter body assemblies are numbered to indicate poppet nozzle order. 3. Push the poppet nozzles into the casting sockets. 4. Inspect the poppet nozzles in order to ensure they are firmly seated and locked in the casting sockets. 5. Install the upper manifold electrical connector. 6. Install the new O-ring seal on engine fuel feed and return pipes. 7. Install the fuel feed and return hoses to the engine fuel pipes. Tighten Tighten the fuel pipe nuts to 30.0 Nm (22 lb. ft.). 8. Inspect for fuel leaks. 8.1. Turn ON the ignition switch for 2 seconds. 8.2. Then turn the ignition switch to the OFF position for 10 seconds. 8.3. Again turn the ignition switch to the ON position. 8.4. Check for fuel leaks. 9. Disconnect the negative battery cable. 10. Disconnect the fuel pipes. 11. Install the upper manifold assembly. Refer to Engine Mechanical. 12. Tighten the fuel filler cap. 13. Connect the fuel Pipes. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Body > Component Information > Service and Repair > Throttle Body Cleaning > Page 6579 14. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Cable/Linkage > Component Information > Technical Service Bulletins > Recalls for Throttle Cable/Linkage: > 96C26 > Apr > 96 > Recall Throttle Cable May Contact Dash Mat Technical Service Bulletin # 96C26 Date: 960401 Recall - Throttle Cable May Contact Dash Mat CHEVROLET No.: 96-C-26 Date: 04-01-96 Subject: PRODUCT SAFETY CAMPAIGN 96-C-26 - THROTTLE CABLE DASH MAT CONTACT Model and Year: 1995-96 C/K PICKUPS/CAB CHASSIS, SUBURBANS & TAHOES WITH GASOLINE ENGINES To: All Chevrolet/Geo Dealers The National Traffic and Motor Vehicle Safety Act as amended, provides that each vehicle which is subject to a recall campaign of this type must be adequately repaired within a reasonable time after the owner has tendered it for repair. A failure to repair within sixty (60) days after tender of a vehicle is prima facie evidence of failure to repair within a reasonable time. If the condition is not adequately repaired within a reasonable time, the owner may be entitled to an identical or reasonably equivalent vehicle at no charge or to a refund of the purchase price less a reasonable allowance for depreciation. To avoid having to provide these burdensome solution, every effort must be made to promptly schedule an appointment with each owner and to repair their vehicle as soon as possible. As you will see in reading the attached cop of the letter that is being sent to owner, the owners are being instructed to contact the Chevrolet Customer Assistance Center if their dealer does not remedy the condition within five (5) days of the mutually agreed upon service date. If the condition is not remedied within a reasonable time, they are instructed on how to contact the National Highway Traffic Safety Administration. Defect & Vehicles Involved DEFECT INVOLVED General Motors has decided that certain 1995-96 Chevrolet C/K Pickups/Cab Chassis, Utilities, and Suburban model trucks equipped with gasoline engines fail to conform to Federal Motor Vehicle Safety Standard (FMVSS) 124, "Accelerator Control Systems". Some of these vehicles were assembled with the throttle cable contacting the dash mat. The dash mat may bind the throttle such that if this system were tested for maximum throttle return times as required by FMVSS 124, it may not meet these requirements. To correct this condition, dealers are to inspect for adequate throttle cable to dash mat clearance, and , if there is insufficient clearance, cut out a portion of the dash mat to provide clearance. VEHICLES INVOLVED Involved are certain 1995-96 Chevrolet C/K Pickups/Cab Chassis, Suburbans & Tahoes equipped with gasoline engines and built within the VIN breakpoints as shown. Involved vehicles have been identified by Vehicle Identification Number Computer Listings. Computer listings contain the complete Vehicle Identification Number, owner name and address data, and are furnished to involved dealers with campaign bulletin. Owner name and address data furnished will enable dealers to follow-up with owners involved in this campaign. These listings may contain owner name and addresses obtained from State Motor Vehicle Registration Records. The use of such motor vehicle Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Cable/Linkage > Component Information > Technical Service Bulletins > Recalls for Throttle Cable/Linkage: > 96C26 > Apr > 96 > Recall Throttle Cable May Contact Dash Mat > Page 6588 registration data for any other purpose is a violation of law in several states. Accordingly, you are urged to limit the use of this listing to the follow-up necessary to complete this campaign. Any dealer not receiving as computer listing with the campaign bulletin has no involved vehicles currently assigned. Owner Notification & Dealer Campaign Responsibility OWNER NOTIFICATION Owners will be notified of this campaign on their vehicles by Chevrolet Motor Division (see copy of owner letter included with this bulletin). DEALER CAMPAIGN RESPONSIBILITY All unsold new vehicles in dealers, possession and subject to this campaign must be held and inspected/repaired per the service procedure of this campaign bulletin before owners take possession of these vehicles. Dealers are to service all vehicles subject to this campaign at no charge to owners, regardless of mileage, age of vehicle, or ownership, from this time forward. Owners of vehicles recently sold from your new vehicle inventory with no owner information indicated on the dealer listing, are to be contacted by the dealer, and arrangements made to make the required correction according to the instructions contained in this bulletin. This could be done by mailing to such owners a copy of the owners letter accompanying this bulletin. Campaign follow-up cards should not be used for this purpose, since the owner may not as yet have received the notification letter. In summary, whenever a vehicle subject to this campaign enters your vehicle inventory, or is in your dealership for service in the future, please take the steps necessary to be sure the campaign correction has been made before selling or releasing the vehicle. This bulletin is notice to you that the new motor vehicles included in this campaign may not comply with the standard identified above. Under Section 108 of the National Traffic and Motor Vehicle Safety Act, it is illegal for a dealer to sell a new motor vehicle which the dealer knows does not comply with an applicable Federal Motor Vehicle Safety Standard. As a consequence, if you sell any of these motor vehicles without first performing the campaign correction, your dealership may be subject to civil penalty up to $1,000 for each such sale. Parts Information No parts are required to complete this campaign. Service Procedure 1. Place vehicle in park, set parking brake and turn engine to full lock position. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Cable/Linkage > Component Information > Technical Service Bulletins > Recalls for Throttle Cable/Linkage: > 96C26 > Apr > 96 > Recall Throttle Cable May Contact Dash Mat > Page 6589 2. Locate accelerator cable between accelerator lever assembly and bulkhead under dash (Figure 1). 3. Measure minimum clearance between accelerator cable and dash mat. 4. If clearance of at least 12 mm (0.5 in.) exists between cable and dash insulator mat through entire range of pedal travel, proceed to step 7. 5. Inspect area under mat around location to insure no wiring was routed under this section. 6. Using a carpet knife or similar tool, carefully cut away a sufficient section of the dash mat to provide at least 12 mm (0.5 in.) clearance between pad and accelerator cable through entire range of motion. 7. Install Campaign Identification Label. Campaign ID Label & Claim Information CAMPAIGN IDENTIFICATION LABEL Each vehicle corrected in accordance with the instructions outlined in this Product Campaign Bulletin will require a "Campaign Identification Label". Each label provide a space to include the campaign number and the five (5) digit dealer code of the dealer performing the campaign service. This information may be inserted with a typewriter or a ball point pen. Each "Campaign Identification Label" is to be located on the radiator core support in an area which will be visible when the vehicle is brought in for periodic servicing by the owner. When installing the new Campaign Identification Label, be sure to install the clear protective covering. Additional Campaign Identification Labels can be obtained from VISPAC Incorporated by calling 1-800-269-5100 (Monday-Friday, 8:00 a.m. to 4:30 p.m. EST). Ask for Item Number S-1015 when ordering. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Cable/Linkage > Component Information > Technical Service Bulletins > Recalls for Throttle Cable/Linkage: > 96C26 > Apr > 96 > Recall Throttle Cable May Contact Dash Mat > Page 6590 Apply "Campaign Identification Label", only on a clean, dry surface. CLAIM INFORMATION Refer to the General Motors Corporation Claims Processing Manual for details on Product Campaign Claim Submission. Owner Letter Dear Chevrolet Customer: This notice is sent to you in accordance with the requirements of the National Traffic and Motor Vehicle Safety Act. REASON FOR THIS RECALL General Motors has decided that certain 1995-96 Chevrolet C/K Pickups/Cab Chassis, Utilities, and Suburban model trucks equipped with gasoline engines fail to conform to Federal Motor Vehicle Safety Standard (FMVSS) 124, "Accelerator Control Systems". Some of these vehicles were assembled with the throttle cable contacting the dash mat. The dash mat may bind the throttle such that if this system were tested for maximum throttle return times as required by FMVSS 124, it may not meet these requirements. WHAT WE WILL DO To correct this condition, your dealer will inspect for adequate throttle cable to dash mat clearance, and , if there is insufficient clearance, cut out a portion of the dash mat to provide clearance. This service will be performed at no charge to you. WHAT YOU SHOULD DO Please contact your Chevrolet dealer as soon as possible to arrange a service date and so the dealer may order the necessary parts for the repair. Instructions for making this correction have been sent to your dealer. The labor time necessary to perform this service correction is approximately 15 minutes. Please ask your dealer if you wish to know how much additional time will be needed to schedule and process your vehicle. The enclosed owner reply card identifies your vehicle. Presentation of this card to your dealer will assist in making the necessary correction in the shortest possible time. If you have sold or traded your vehicle, please let us know by completing the postage paid reply card and returning it to us. Your Chevrolet dealer is best equipped to provide service to ensure that your vehicle is corrected as promptly as possible. If, however you take your vehicle to your dealer on the agreed service date, and they do not remedy this condition that date or within five (5) days, we recommend you contact the Chevrolet Customer Assistance Center by calling 1-800-222-1020. After contacting your dealer and the Customer Assistance Center, if you are still not satisfied that we have done our best to remedy this condition without charge and within a reasonable time, you may wish to write the Administrator, National Highway Traffic Safety Administration, 400 Seventh Street, S.W., Washington, D.C. 20590 or call 1-800-424-9393 (Washington D.C. residents use 202-366-0123). We are sorry to cause you this inconvenience; however, we have taken this action in the interest of your safety and continue satisfaction with our products. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Cable/Linkage > Component Information > Technical Service Bulletins > Recalls for Throttle Cable/Linkage: > NHTSA96V057000 > Mar > 96 > Recall 96V057000: Throttle Binding Throttle Cable/Linkage: Recalls Recall 96V057000: Throttle Binding THESE VEHICLES WERE ASSEMBLED WITH THE THROTTLE CABLE CONTACTING THE DASH MAT WHICH COULD BIND THE THROTTLE. THIS DOES NOT MEET WITH THE MAXIMUM RETURN TIMES REQUIRED BY FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 124, "ACCELERATOR CONTROL SYSTEMS." CONSEQUENCE OF NON-COMPLIANCE: THE ENGINE SPEED MAY NOT RETURN TO IDLE INCREASING THE POTENTIAL FOR A VEHICLE ACCIDENT. DEALERS WILL INSPECT FOR ADEQUATE THROTTLE CABLE TO DASH MAT CLEARANCE, AND IF THERE IS INSUFFICIENT CLEARANCE, CUT OUT A PORTION OF THE DASH MAT TO PROVIDE PROPER CLEARANCE. SYSTEM: FUEL; THROTTLE LINKAGES AND CONTROL; FMVSS NO. 124. VEHICLE DESCRIPTION: PICKUP TRUCKS, CAB/CHASSIS, UTILITY AND MULTI-PURPOSE TRUCKS EQUIPPED WITH GASOLINE ENGINES. NOTE: OWNERS WHO TAKE THEIR VEHICLES TO AN AUTHORIZED DEALER ON AN AGREED UPON SERVICE DATE AND DO NOT RECEIVE THE FREE REMEDY WITHIN A REASONABLE TIME, SHOULD CONTACT CHEVROLET AT 1-800-222-1020 OR GMC AT 1-800-462-8782. ALSO CONTACT THE NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION'S AUTO SAFETY HOTLINE AT 1-800-424-9393. 1995 CHEVROLET TRUCK C10 1995 CHEVROLET TRUCK C20 1995 CHEVROLET TRUCK C30 1995 CHEVROLET TRUCK K10 1995 CHEVROLET TRUCK K20 1995 CHEVROLET TRUCK K30 1995 CHEVROLET TRUCK SUBURBAN 1995 CHEVROLET TRUCK TAHOE 1995 GMC C15 1995 GMC C25 1995 GMC C35 1995 GMC SIERRA 1995 GMC SUBURBAN 1995 GMC YUKON 1996 CHEVROLET TRUCK C10 1996 CHEVROLET TRUCK C20 1996 CHEVROLET TRUCK C30 1996 CHEVROLET TRUCK K10 1996 CHEVROLET TRUCK K20 1996 CHEVROLET TRUCK K30 1996 CHEVROLET TRUCK SUBURBAN 1996 CHEVROLET TRUCK TAHOE 1996 GMC C15 1996 GMC C25 1996 GMC C35 1996 GMC SIERRA 1996 GMC SUBURBAN 1996 GMC YUKON Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Cable/Linkage > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Throttle Cable/Linkage: > 96C26 > Apr > 96 > Recall - Throttle Cable May Contact Dash Mat Technical Service Bulletin # 96C26 Date: 960401 Recall - Throttle Cable May Contact Dash Mat CHEVROLET No.: 96-C-26 Date: 04-01-96 Subject: PRODUCT SAFETY CAMPAIGN 96-C-26 - THROTTLE CABLE DASH MAT CONTACT Model and Year: 1995-96 C/K PICKUPS/CAB CHASSIS, SUBURBANS & TAHOES WITH GASOLINE ENGINES To: All Chevrolet/Geo Dealers The National Traffic and Motor Vehicle Safety Act as amended, provides that each vehicle which is subject to a recall campaign of this type must be adequately repaired within a reasonable time after the owner has tendered it for repair. A failure to repair within sixty (60) days after tender of a vehicle is prima facie evidence of failure to repair within a reasonable time. If the condition is not adequately repaired within a reasonable time, the owner may be entitled to an identical or reasonably equivalent vehicle at no charge or to a refund of the purchase price less a reasonable allowance for depreciation. To avoid having to provide these burdensome solution, every effort must be made to promptly schedule an appointment with each owner and to repair their vehicle as soon as possible. As you will see in reading the attached cop of the letter that is being sent to owner, the owners are being instructed to contact the Chevrolet Customer Assistance Center if their dealer does not remedy the condition within five (5) days of the mutually agreed upon service date. If the condition is not remedied within a reasonable time, they are instructed on how to contact the National Highway Traffic Safety Administration. Defect & Vehicles Involved DEFECT INVOLVED General Motors has decided that certain 1995-96 Chevrolet C/K Pickups/Cab Chassis, Utilities, and Suburban model trucks equipped with gasoline engines fail to conform to Federal Motor Vehicle Safety Standard (FMVSS) 124, "Accelerator Control Systems". Some of these vehicles were assembled with the throttle cable contacting the dash mat. The dash mat may bind the throttle such that if this system were tested for maximum throttle return times as required by FMVSS 124, it may not meet these requirements. To correct this condition, dealers are to inspect for adequate throttle cable to dash mat clearance, and , if there is insufficient clearance, cut out a portion of the dash mat to provide clearance. VEHICLES INVOLVED Involved are certain 1995-96 Chevrolet C/K Pickups/Cab Chassis, Suburbans & Tahoes equipped with gasoline engines and built within the VIN breakpoints as shown. Involved vehicles have been identified by Vehicle Identification Number Computer Listings. Computer listings contain the complete Vehicle Identification Number, owner name and address data, and are furnished to involved dealers with campaign bulletin. Owner name and address data furnished will enable dealers to follow-up with owners involved in this campaign. These listings may contain owner name and addresses obtained from State Motor Vehicle Registration Records. The use of such motor vehicle Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Cable/Linkage > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Throttle Cable/Linkage: > 96C26 > Apr > 96 > Recall - Throttle Cable May Contact Dash Mat > Page 6600 registration data for any other purpose is a violation of law in several states. Accordingly, you are urged to limit the use of this listing to the follow-up necessary to complete this campaign. Any dealer not receiving as computer listing with the campaign bulletin has no involved vehicles currently assigned. Owner Notification & Dealer Campaign Responsibility OWNER NOTIFICATION Owners will be notified of this campaign on their vehicles by Chevrolet Motor Division (see copy of owner letter included with this bulletin). DEALER CAMPAIGN RESPONSIBILITY All unsold new vehicles in dealers, possession and subject to this campaign must be held and inspected/repaired per the service procedure of this campaign bulletin before owners take possession of these vehicles. Dealers are to service all vehicles subject to this campaign at no charge to owners, regardless of mileage, age of vehicle, or ownership, from this time forward. Owners of vehicles recently sold from your new vehicle inventory with no owner information indicated on the dealer listing, are to be contacted by the dealer, and arrangements made to make the required correction according to the instructions contained in this bulletin. This could be done by mailing to such owners a copy of the owners letter accompanying this bulletin. Campaign follow-up cards should not be used for this purpose, since the owner may not as yet have received the notification letter. In summary, whenever a vehicle subject to this campaign enters your vehicle inventory, or is in your dealership for service in the future, please take the steps necessary to be sure the campaign correction has been made before selling or releasing the vehicle. This bulletin is notice to you that the new motor vehicles included in this campaign may not comply with the standard identified above. Under Section 108 of the National Traffic and Motor Vehicle Safety Act, it is illegal for a dealer to sell a new motor vehicle which the dealer knows does not comply with an applicable Federal Motor Vehicle Safety Standard. As a consequence, if you sell any of these motor vehicles without first performing the campaign correction, your dealership may be subject to civil penalty up to $1,000 for each such sale. Parts Information No parts are required to complete this campaign. Service Procedure 1. Place vehicle in park, set parking brake and turn engine to full lock position. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Cable/Linkage > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Throttle Cable/Linkage: > 96C26 > Apr > 96 > Recall - Throttle Cable May Contact Dash Mat > Page 6601 2. Locate accelerator cable between accelerator lever assembly and bulkhead under dash (Figure 1). 3. Measure minimum clearance between accelerator cable and dash mat. 4. If clearance of at least 12 mm (0.5 in.) exists between cable and dash insulator mat through entire range of pedal travel, proceed to step 7. 5. Inspect area under mat around location to insure no wiring was routed under this section. 6. Using a carpet knife or similar tool, carefully cut away a sufficient section of the dash mat to provide at least 12 mm (0.5 in.) clearance between pad and accelerator cable through entire range of motion. 7. Install Campaign Identification Label. Campaign ID Label & Claim Information CAMPAIGN IDENTIFICATION LABEL Each vehicle corrected in accordance with the instructions outlined in this Product Campaign Bulletin will require a "Campaign Identification Label". Each label provide a space to include the campaign number and the five (5) digit dealer code of the dealer performing the campaign service. This information may be inserted with a typewriter or a ball point pen. Each "Campaign Identification Label" is to be located on the radiator core support in an area which will be visible when the vehicle is brought in for periodic servicing by the owner. When installing the new Campaign Identification Label, be sure to install the clear protective covering. Additional Campaign Identification Labels can be obtained from VISPAC Incorporated by calling 1-800-269-5100 (Monday-Friday, 8:00 a.m. to 4:30 p.m. EST). Ask for Item Number S-1015 when ordering. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Cable/Linkage > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Throttle Cable/Linkage: > 96C26 > Apr > 96 > Recall - Throttle Cable May Contact Dash Mat > Page 6602 Apply "Campaign Identification Label", only on a clean, dry surface. CLAIM INFORMATION Refer to the General Motors Corporation Claims Processing Manual for details on Product Campaign Claim Submission. Owner Letter Dear Chevrolet Customer: This notice is sent to you in accordance with the requirements of the National Traffic and Motor Vehicle Safety Act. REASON FOR THIS RECALL General Motors has decided that certain 1995-96 Chevrolet C/K Pickups/Cab Chassis, Utilities, and Suburban model trucks equipped with gasoline engines fail to conform to Federal Motor Vehicle Safety Standard (FMVSS) 124, "Accelerator Control Systems". Some of these vehicles were assembled with the throttle cable contacting the dash mat. The dash mat may bind the throttle such that if this system were tested for maximum throttle return times as required by FMVSS 124, it may not meet these requirements. WHAT WE WILL DO To correct this condition, your dealer will inspect for adequate throttle cable to dash mat clearance, and , if there is insufficient clearance, cut out a portion of the dash mat to provide clearance. This service will be performed at no charge to you. WHAT YOU SHOULD DO Please contact your Chevrolet dealer as soon as possible to arrange a service date and so the dealer may order the necessary parts for the repair. Instructions for making this correction have been sent to your dealer. The labor time necessary to perform this service correction is approximately 15 minutes. Please ask your dealer if you wish to know how much additional time will be needed to schedule and process your vehicle. The enclosed owner reply card identifies your vehicle. Presentation of this card to your dealer will assist in making the necessary correction in the shortest possible time. If you have sold or traded your vehicle, please let us know by completing the postage paid reply card and returning it to us. Your Chevrolet dealer is best equipped to provide service to ensure that your vehicle is corrected as promptly as possible. If, however you take your vehicle to your dealer on the agreed service date, and they do not remedy this condition that date or within five (5) days, we recommend you contact the Chevrolet Customer Assistance Center by calling 1-800-222-1020. After contacting your dealer and the Customer Assistance Center, if you are still not satisfied that we have done our best to remedy this condition without charge and within a reasonable time, you may wish to write the Administrator, National Highway Traffic Safety Administration, 400 Seventh Street, S.W., Washington, D.C. 20590 or call 1-800-424-9393 (Washington D.C. residents use 202-366-0123). We are sorry to cause you this inconvenience; however, we have taken this action in the interest of your safety and continue satisfaction with our products. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Cable/Linkage > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Throttle Cable/Linkage: > NHTSA96V057000 > Mar > 96 > Recall 96V057000: Throttle Binding Throttle Cable/Linkage: All Technical Service Bulletins Recall 96V057000: Throttle Binding THESE VEHICLES WERE ASSEMBLED WITH THE THROTTLE CABLE CONTACTING THE DASH MAT WHICH COULD BIND THE THROTTLE. THIS DOES NOT MEET WITH THE MAXIMUM RETURN TIMES REQUIRED BY FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 124, "ACCELERATOR CONTROL SYSTEMS." CONSEQUENCE OF NON-COMPLIANCE: THE ENGINE SPEED MAY NOT RETURN TO IDLE INCREASING THE POTENTIAL FOR A VEHICLE ACCIDENT. DEALERS WILL INSPECT FOR ADEQUATE THROTTLE CABLE TO DASH MAT CLEARANCE, AND IF THERE IS INSUFFICIENT CLEARANCE, CUT OUT A PORTION OF THE DASH MAT TO PROVIDE PROPER CLEARANCE. SYSTEM: FUEL; THROTTLE LINKAGES AND CONTROL; FMVSS NO. 124. VEHICLE DESCRIPTION: PICKUP TRUCKS, CAB/CHASSIS, UTILITY AND MULTI-PURPOSE TRUCKS EQUIPPED WITH GASOLINE ENGINES. NOTE: OWNERS WHO TAKE THEIR VEHICLES TO AN AUTHORIZED DEALER ON AN AGREED UPON SERVICE DATE AND DO NOT RECEIVE THE FREE REMEDY WITHIN A REASONABLE TIME, SHOULD CONTACT CHEVROLET AT 1-800-222-1020 OR GMC AT 1-800-462-8782. ALSO CONTACT THE NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION'S AUTO SAFETY HOTLINE AT 1-800-424-9393. 1995 CHEVROLET TRUCK C10 1995 CHEVROLET TRUCK C20 1995 CHEVROLET TRUCK C30 1995 CHEVROLET TRUCK K10 1995 CHEVROLET TRUCK K20 1995 CHEVROLET TRUCK K30 1995 CHEVROLET TRUCK SUBURBAN 1995 CHEVROLET TRUCK TAHOE 1995 GMC C15 1995 GMC C25 1995 GMC C35 1995 GMC SIERRA 1995 GMC SUBURBAN 1995 GMC YUKON 1996 CHEVROLET TRUCK C10 1996 CHEVROLET TRUCK C20 1996 CHEVROLET TRUCK C30 1996 CHEVROLET TRUCK K10 1996 CHEVROLET TRUCK K20 1996 CHEVROLET TRUCK K30 1996 CHEVROLET TRUCK SUBURBAN 1996 CHEVROLET TRUCK TAHOE 1996 GMC C15 1996 GMC C25 1996 GMC C35 1996 GMC SIERRA 1996 GMC SUBURBAN 1996 GMC YUKON Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Cable/Linkage > Component Information > Technical Service Bulletins > Page 6607 Throttle Cable/Linkage: Description and Operation The accelerator control system is a control cable type attached at one end to an accelerator pedal assembly. On the other end is the throttle valve. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Cable/Linkage > Component Information > Technical Service Bulletins > Page 6608 Throttle Cable/Linkage: Testing and Inspection Check for correct cable routing, or binding. Correct as necessary. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Cable/Linkage > Component Information > Technical Service Bulletins > Page 6609 Throttle Cable/Linkage: Service and Repair Throttle Cable Routing Accelerator Cable Routing Bracket REMOVAL PROCEDURE 1. Remove the throttle cable from the throttle lever. 2. Remove the accelerator cable from the engine cable bracket. 3. Remove the accelerator cable from the cable routing bracket. 4. Remove the accelerator cable from the accelerator pedal (2). 5. Remove the accelerator cable from the dash panel (1). INSTALLATION PROCEDURE Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Cable/Linkage > Component Information > Technical Service Bulletins > Page 6610 1. Install the accelerator cable from the dash panel (1). 2. Install the accelerator cable from the accelerator pedal (2). 3. Install the accelerator cable from the cable routing bracket. 4. Install the accelerator cable from the engine cable bracket. 5. Install the throttle cable from the throttle lever. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Specifications Throttle Position Sensor: Specifications Screw assemblies ................................................................................................................................ .................................................. 2.0 Nm (18.0 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Specifications > Page 6614 Engine Side, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Throttle Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6617 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6618 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6619 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6620 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6621 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6622 Throttle Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6623 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6624 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6625 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6626 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6627 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6628 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6629 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6630 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6631 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6632 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6633 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6634 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6635 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6636 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6637 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6638 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6639 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6640 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6641 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6642 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6643 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6644 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6645 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6646 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6647 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6648 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6649 TP Sensor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Diagrams > Page 6650 Throttle Position Sensor: Description and Operation Diagram The non-adjustable Throttle Position (TP) sensor is mounted on the throttle body assembly opposite the throttle lever. The TP sensor senses the throttle valve angle and relays that information to the VCM. Knowledge of throttle angle is one of the inputs needed by the VCM to generate the required injector control signals (pulses). For further information on replacement, refer to TP Sensor. See: Service and Repair Legend (1) Throttle Body Assembly. (2) IAC Valve Assembly 0-ring. (3) IAC Valve Assembly Attaching Screw. (4) Idle Air Control (IAC) Valve Assembly. (5) TP Sensor 0-ring (6) Throttle Position (TP) Sensor. (7) TP Sensor Attaching Screw. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Testing and Inspection > Throttle Position (TP) Sensor Throttle Position Sensor: Testing and Inspection Throttle Position (TP) Sensor When the VCM detects a malfunction with the Throttle Position (TP) sensor circuits, the following Diagnostic Trouble Code (DTC)s will set: ^ DTC P0121 circuit performance ^ DTC P0122 circuit low. ^ DTC P0123 circuit high. ^ DTC P1121 intermittent circuit high. ^ DTC P1122 intermittent circuit low. Refer to Diagnostic Tables. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Testing and Inspection > Throttle Position (TP) Sensor > Page 6653 Throttle Position Sensor: Testing and Inspection Throttle Position Sensor Output This check should be performed when Throttle Position (TP) sensor attaching parts have been replaced. A scan tool can be used to read the TP signal output voltage. 1. Connect digital voltmeter J 39200 from TP sensor connector terminal B (BLk wire) to terminal C (DK Blue wire). Jumpers for terminal access can be made using terminals 1214836 and 12014837. 2. With ignition ON, engine stopped, the TP signal voltage should be less than 1.25V if more than 1.25V verify free throttle movement. If still more than 1.25V, replace TP sensor. 3. Remove the voltmeter and jumpers, reconnect the TP sensor connector to the sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Testing and Inspection > Page 6654 Throttle Position Sensor: Service and Repair Throttle Position Sensor Electrical Connector REMOVAL PROCEDURE CAUTION: The Throttle Position (TP) sensor is an electrical component. Do not soak the TP sensor in any liquid cleaner or solvent, as damage may result. 1. Remove the air cleaner and adapter. 2. Disconnect the electrical connector releasing locking tab. 3. Remove the two TP sensor attaching screw assemblies. 4. Remove the TP sensor from throttle body assembly. 5. Remove the TP sensor seal. INSTALLATION PROCEDURE 1. Install the TP sensor seal over throttle shaft. 2. With throttle valve closed, install the TP sensor on the throttle shaft. Rotate counterclockwise to align mounting holes. 3. Install the two TP sensor attaching screw assemblies. Tighten ^ Tighten the screw assemblies to 2.0 Nm (18.0 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Throttle Position Sensor > Component Information > Testing and Inspection > Page 6655 4. Connect the electrical connector. 5. Install the air cleaner and adapter. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Firing Order > Component Information > Specifications > Ignition Firing Order Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Ignition Timing > Number One Cylinder > Component Information > Locations > Number 1 Cylinder Location Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Ignition Timing > Timing Marks and Indicators > System Information > Locations > Crankshaft Rotation Timing Marks and Indicators: Locations Crankshaft Rotation Crankshaft Rotation (Typical Crankshaft Pulley) Crankshaft rotation is clockwise when viewed from in front of the crankshaft pulley as shown in the generic image. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Ignition Timing > Timing Marks and Indicators > System Information > Locations > Crankshaft Rotation > Page 6670 Timing Marks and Indicators: Locations Timing Marks The ignition timing is completely controlled by the Vehicle Control Module (VCM). No timing reference marks are provided. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Camshaft Position Sensor: Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6675 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6676 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6677 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6678 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6679 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6680 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6681 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Page 6682 Camshaft Position Sensor: Specifications Camshaft position sensor retaining screw ........................................................................................................................................... 4-6 Nm (35-53 lb. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Page 6683 Engine View, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Camshaft Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6686 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6687 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6688 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6689 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6690 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6691 Camshaft Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6692 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6693 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6694 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6695 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6696 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6697 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6698 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6699 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6700 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6701 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6702 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6703 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6704 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6705 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6706 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6707 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6708 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6709 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6710 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6711 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6712 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6713 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6714 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6715 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6716 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6717 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Page 6718 Camshaft Position Sensor: Description and Operation Camshaft Position Sensor The Camshaft Position (CMP) sensor is located within the distributor. It's operation is very similar to the Crankshaft Position (CKP) sensor however it will provide one pulse per camshaft revolution (1x signal). This signal is not detrimental to the driveability of the vehicle. The Vehicle Control Module (VCM) utilizes this signal in conjunction with the crankshaft position to determine which cylinder(s) are misfiring. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Testing and Inspection > Cam Signal Camshaft Position Sensor: Testing and Inspection Cam Signal The VCM uses this signal to determine the position of the #1 piston during its power stroke. This signal is used by the VCM to calculate fuel injection mode of operation. A loss of this signal will set DTC P0340. If the cam signal is lost while the engine is running, the fuel injection system will shift to a calculated fuel injection mode based on the last fuel injection pulse, and the engine will continue to run. The engine can be restarted and will run in the calculated mode as long as the fault is present Refer to Diagnostic Trouble Code (DTC) P0340 Camshaft Position Sensor (CKP) Sensor Circuit. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Camshaft Position Sensor > Component Information > Testing and Inspection > Page 6721 Camshaft Position Sensor: Service and Repair REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Disconnect the electrical connector from the camshaft position sensor. 3. Remove the camshaft position sensor retaining screw. 4. Remove the camshaft position sensor. INSTALLATION PROCEDURE 1. Install the camshaft position sensor. 2. Install the camshaft position sensor retaining screw, torque to 4-6 Nm (35-53 lb. in.). 3. Connect the electrical connector. 4. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-014 > Apr > 00 > Engine - No/Hard/Slow Start/Backfire/Kickback Crankshaft Position Sensor: Customer Interest Engine - No/Hard/Slow Start/Backfire/Kickback File In Section: 06 - Engine/Propulsion System Bulletin No.: 00-06-04-014 Date: April, 2000 TECHNICAL Subject: No, Hard, or Slow Start, Backfire or "Kickback" During Crank/Start, "Grinding" or Unusual Noises During Crank, DTC P0338 (Replace Crankshaft Position Sensor) Models: 1999-2000 Cadillac Escalade 1995-2000 Chevrolet and GMC SIT Models 1996-2000 Chevrolet and GMC C/K, M/L, G, P Models 1996-2000 Oldsmobile Bravada with 4.3 L, 5.0 L, 5.7 L or 7.4 L Engine (VINs W, X, M, R, J RPOs L35, LF6, L30, L31, L29) Condition: Some customers may comment on one or more of the following conditions: ^ Backfire during crank/start ^ "Kickback" during crank/start ^ "No" start ^ "Slow" or "hard" start/crank ^ "Grinding" or unusual noises during crank/start ^ Cracked or broken engine block at the starter boss ^ Broken starter drive housing ^ Broken starter ring gear on flywheel ^ Any combination of the above Cause: A condition may exist that allows the crankshaft position sensor to command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss. Correction: Inspect for a stored powertrain DTC code P0338. This DTC will NOT illuminate the "Service Engine Soon" light. If this code is stored, the Crankshaft Position Sensor, P/N 10456607, MUST be replaced and the remaining components inspected for damage (engine block at the starter boss, the starter drive housing, and the engine flywheel starter ring gear). Notice: When DTC code P0338 is set, failure to replace the Crankshaft Position Sensor could result in repeated inoperative conditions of the starter or flywheel. Important: Some flywheel wear is normal; broken or missing teeth and/or cracks, are not normal. Parts Information Parts are currently available from GMSPO. Warranty Information: For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 00-06-04-014 > Apr > 00 > Engine - No/Hard/Slow Start/Backfire/Kickback Crankshaft Position Sensor: All Technical Service Bulletins Engine - No/Hard/Slow Start/Backfire/Kickback File In Section: 06 - Engine/Propulsion System Bulletin No.: 00-06-04-014 Date: April, 2000 TECHNICAL Subject: No, Hard, or Slow Start, Backfire or "Kickback" During Crank/Start, "Grinding" or Unusual Noises During Crank, DTC P0338 (Replace Crankshaft Position Sensor) Models: 1999-2000 Cadillac Escalade 1995-2000 Chevrolet and GMC SIT Models 1996-2000 Chevrolet and GMC C/K, M/L, G, P Models 1996-2000 Oldsmobile Bravada with 4.3 L, 5.0 L, 5.7 L or 7.4 L Engine (VINs W, X, M, R, J RPOs L35, LF6, L30, L31, L29) Condition: Some customers may comment on one or more of the following conditions: ^ Backfire during crank/start ^ "Kickback" during crank/start ^ "No" start ^ "Slow" or "hard" start/crank ^ "Grinding" or unusual noises during crank/start ^ Cracked or broken engine block at the starter boss ^ Broken starter drive housing ^ Broken starter ring gear on flywheel ^ Any combination of the above Cause: A condition may exist that allows the crankshaft position sensor to command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss. Correction: Inspect for a stored powertrain DTC code P0338. This DTC will NOT illuminate the "Service Engine Soon" light. If this code is stored, the Crankshaft Position Sensor, P/N 10456607, MUST be replaced and the remaining components inspected for damage (engine block at the starter boss, the starter drive housing, and the engine flywheel starter ring gear). Notice: When DTC code P0338 is set, failure to replace the Crankshaft Position Sensor could result in repeated inoperative conditions of the starter or flywheel. Important: Some flywheel wear is normal; broken or missing teeth and/or cracks, are not normal. Parts Information Parts are currently available from GMSPO. Warranty Information: For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Crankshaft Position Sensor: All Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6739 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6740 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6741 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6742 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6743 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6744 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6745 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Crankshaft Position Sensor: All Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6751 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6752 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6753 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6754 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6755 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6756 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6757 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Page 6758 Crankshaft Position Sensor: Specifications Crankshaft Position Sensor mounting bolts ................................................................................................................................................. 8 Nm (71 lb. In.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Page 6759 Engine Side, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Crankshaft Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6762 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6763 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6764 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6765 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6766 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6767 Crankshaft Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6768 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6769 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6770 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6771 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6772 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6773 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6774 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6775 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6776 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6777 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6778 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6779 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6780 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6781 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6782 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6783 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6784 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6785 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6786 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6787 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6788 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6789 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6790 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6791 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6792 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6793 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Page 6794 Crankshaft Position Sensor: Description and Operation DESCRIPTION The Crankshaft Position (CKP) Sensor is located in the front engine cover and is perpendicular to the crankshaft target wheel. The air gap between the sensor and the wheel is preset and not adjustable. The target wheel has three slots 60° apart and is keyed to the crankshaft. As the target wheel rotates, the slots passing by the sensor create a change in the magnetic field of the sensor which results in an induced voltage pulse. One revolution of the crankshaft results in three pulses (3x signal). Based on these pulses, the VCM is able to determine crankshaft position and engine speed. The VCM then activates the fuel injector and provides a spark to the Distributor. The relation between the crankshaft position sensor and the target wheel is crucial. The sensor must be exactly perpendicular to the target wheel with the correct air gap. OPERATION The crankshaft position sensor provides the VCM with crankshaft speed and crankshaft position. The VCM utilizes this information to determine if an engine Misfire is present. The VCM monitors the Crankshaft Position Sensor (CKP) sensor for momentarily drop in crankshaft speed to determine if a misfire is occurring. When the VCM detects a misfire, a Diagnostic Trouble Code (DTC) P0300 will set. The VCM also monitors the CKP sensor signal circuit for malfunctions. The VCM monitors CKP signal and the High and Low resolution signals. The VCM calculates these signals to determine a ratio. When the VCM detects that the ratio is out of normal operating range, the VCM will set a Diagnostic Trouble Code (DTC) P0337 or a DTC P0338. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Page 6795 Crankshaft Position Sensor: Service and Repair REMOVAL PROCEDURE 1. Remove the electrical connector. 2. Remove the sensor hold down bolt. 3. Remove the sensor from the timing cover. NOTE: When installing or removing a crankshaft position (CKP) sensor make sure the sensor is fully seated and held stationary in the front cover before torquing the hold down bolt into the front cover. A sensor which is not seated may result in erratic operation and lead to the setting of false codes. 4. Inspect the sensor O-ring for wear, cracks or leakage. Replace if necessary. Lube the new O-ring with clean engine oil before installing. INSTALLATION PROCEDURE NOTE: Make certain that the Crankshaft Position (CKP) sensor mounting surfaces are clean and free of burrs before installing the CKP sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Page 6796 1. Install the sensor into the timing cover. 2. Install the sensor hold down bolt. Tighten ^ Tighten the hold down bolt to 8 Nm (71 lb. in.). 3. Install the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Technical Service Bulletins > Ignition System - Distributor Is Now Repairable Distributor: Technical Service Bulletins Ignition System - Distributor Is Now Repairable CHEVROLET 71-65-40 Issued: 05/01/97 SMU - SECTION 6E - REVISED ENHANCED IGNITION SYSTEM DESCRIPTION AND OPERATION SUBJECT: SERVICE MANUAL UPDATE - SECTION 6E - ENGINE CONTROLS REVISED ENHANCED IGNITION SYSTEM DESCRIPTION AND OPERATION MODELS: 1995-97 CHEVROLET AND GMC S/T, M/L, C/K, GMT600, P MODELS 1996-97 OLDSMOBILE BRAVADA WITH 4.3L, 5.0L, 5.7L, 7.4L ENGINE (VINS W, M, R, J - RPOS L35, L30, L31, L29) THIS BULLETIN IS BEING ISSUED TO INFORM TECHNICIANS OF A REVISION TO THE ENHANCED IGNITION SYSTEM DESCRIPTION AND OPERATION. THE DISTRIBUTOR IS NOW REPAIRABLE. TECHNICIANS WILL BE REFERRED TO DISTRIBUTOR OVERHAUL IN ENGINE ELECTRICAL FOR PROPER REPAIR AND REPLACEMENT OF ALL COMPONENTS. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Technical Service Bulletins > Ignition System - Distributor Is Now Repairable > Page 6801 Distributor: Technical Service Bulletins Ignition - Distributor Service Kits Now Available File In Section: 6 - Engine Bulletin No.: 77-64-04 Date: April, 1997 SERVICE MANUAL UPDATE Subject: Distributor Service Kits Models: 1995 Chevrolet and GMC S/T Utility Models with 4.3L OBDII Engines ONLY (VIN W - RPO L35) 1996 Chevrolet and GMC C/K, M/L, S/T; P, G 1996 Oldsmobile Bravada 1997 Chevrolet and GMC C/K, M/L, S/T; P, G 1997 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L, 7.4L Engines (VINs W, X, M, R, J - RPOs L35, LF6, L3O, L31, L29) Service kits are now available to field service Distributor Assemblies. Important: Fastening screws have pre-applied thread locking adhesive and should be discarded after removal. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Technical Service Bulletins > Ignition System - Distributor Is Now Repairable > Page 6802 1995 4.3L L35 OBDII Distributor Assemblies are now serviced with 1996 Distributor Assemblies (P/N 1104050). Installation instructions are included with each replacement assembly and must be followed. The following Service Kits are now available: Important: Removed fasteners are not to be re-used. Always use the new fasteners supplied in each kit. Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Technical Service Bulletins > Ignition System - Distributor Is Now Repairable > Page 6803 Warranty Information For Vehicles repaired under warranty use the table shown. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Technical Service Bulletins > Page 6804 Distributor: Specifications Distributor clamp and bolt .................................................................................................................... .................................................. 27 N.m (20 lbs. ft.) Distributor cap screws ........................................ ....................................................................................................................... 4.5-5.0 N.m (40-45 lbs. in.) Distributor rotor .................................................................................................................................... ................................................... 2 N.m (20 lbs. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Technical Service Bulletins > Page 6805 Distributor: Locations Top of Engine, at rear, near Bulkhead Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Technical Service Bulletins > Page 6806 Distributor: Application and ID The part number is pin stamped into the plastic base (directly below the high tension terminals and next to the three pin camshaft sensor connection.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Description and Operation > Distributor Operation Distributor: Description and Operation Distributor Operation DISTRIBUTORS Distributor This ignition system includes the distributor, hall effect switch, ignition coil, secondary wires, spark plugs, knock sensor and crankshaft position sensor. The ignition system is controlled by the vehicle control module (VCM). The VCM monitors information from various engine sensors, computes the desired spark timing and controls the dwell and firing of the ignition coil via an ignition control line to the coil driver. The distributor connects the ignition coil and spark plugs through secondary wires. The rotor directs the spark to the appropriate cylinder. The distributor has a hall effect switch that connects to the VCM through the primary engine harness and provides cylinder identification information. Identification The part number is pin stamped into the plastic base (directly below the high tension terminals and next to the three pin camshaft sensor connection.) Ignition Coil The coil driver controls the current flow in the primary winding of the ignition coil when signaled by the VCM. The interconnects are made by the primary engine harness. The ignition coil can generate up to 35,000 volts and connects to the distributor through a secondary wire. Secondary Wires The secondary wires carry voltage between the ignition coil, distributor, and spark plugs. The secondary wire connections form a tight seal that prevents voltage arching. Hall Effect Switch The hall effect switch connects to the VCM through the primary engine harness and provides cylinder identification information. The hall effect switch is located under the distributor cap. Crankshaft Position Sensor The crankshaft position sensor connects to the VCM through the primary engine harness and provides crank- shaft reference information to the VCM for spark and fuel delivery. The crankshaft position sensor is located in the front cover behind the crankshaft balancer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Description and Operation > Distributor Operation > Page 6809 Distributor: Description and Operation General Description Distributor The distributor is actually an assembly that contains the Camshaft Position (CMP) sensor, cap, rotor and shaft. The distributor is splined by a helical gear to the camshaft and provides spark to each spark plug wire. when servicing the distributor, it is critical to ensure proper cap sealing to the distributor body and correct installation to the camshaft. If the distributor is installed a tooth off in relation to the camshaft, a Diagnostic Trouble Code (DTC) will set. The distributor is not repairable and must be replaced as an assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Description and Operation > Page 6810 Distributor: Testing and Inspection NOTICE: Discoloration of the cap and some whitish build up around the cap terminals is normal. Yellowing of the rotor cap, darkening and some carbon build-up under the rotor segment is normal. Replacement of the cap and rotor is not necessary unless there is a driveablity concern. Inspect 1. Cap for cracks, tiny holes or carbon tracks between cap terminal traces. Carbon tracks can be diagnosed by using an ohmmeter. With the cap removed, place one base ohmmeter lead on a cap terminal. Use the other lead to probe all other terminals and the center carbon ball. Move the base lead to the next terminal and probe all other leads. Continue until all secondary terminals have been tested. If there are any non-infinite readings, replace the cap. 2. Cap for excessive build up of corrosion on the terminals. Scrape them clean or replace the cap. Some build up is normal. 3. Rotor segment. Replace the rotor if there is excessive wear on the rotor segment or the plastic under the segment or staked post is melted. Some looseness of the rotor segment is normal and does not cause performance problems. 4. Shaft for shaft-to-bushing looseness. Insert the shaft in the housing. If the shaft wobbles, replace the housing assembly. 5. Housing for cracks or damage. ^ Refer to Computers and Control Systems for ignition system diagnosis. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment Distributor: Adjustments Camshaft Retard Offset Adjustment Description TEST PROCEDURE The ignition timing cannot be adjusted. The distributor may need adjusting to prevent crossfire. To insure proper alignment of the distributor, perform the following: 1. With the ignition OFF, install a scan tool to the DLC. 2. Start the engine and bring to normal operating temperature. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM. 3. Increase engine speed to 1000 RPM. 4. Monitor the Cam Retard Offset. 5. If the Cam Retard indicates a value of 0° +/-2°, the distributor is properly adjusted. 6. If the Cam Retard does not indicate 0° +/-2°, the distributor must be adjusted. ADJUSTING PROCEDURE 1. With the engine OFF, slightly loosen the distributor hold down bolt. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM. 2. Start the engine and raise engine speed to 1000 RPM. 3. Using a scan tool monitor Cam Retard Offset. 4. Rotate the distributor as follows: 4.1. To compensate for a negative reading, rotate the distributor in the counterclockwise direction. 4.2. To compensate for a positive reading, rotate the distributor in the clockwise direction. 5. Repeat step 4 until 0° +/-2°, is obtained. 6. Turn the ignition OFF. 7. Tighten the distributor hold-down bolt to 3 Nm (25 lb. ft.). 8. Start the engine, raise engine speed to 1000 RPM and recheck Camshaft Retard Offset. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 6813 Distributor: Adjustments Timing Adjustment NOTICE: The distributor is located in a fixed, non-adjustable position. No attempt should be made to adjust the engine base timing by rotating the distributor. Attempting to do so may result in engine cross-fire and mis-fire conditions. The distributor ignition system has no provision for timing adjustment. The base timing is preset when the engine is manufactured and no adjustment is possible. NOTICE: If the distributor is removed from the engine, It can be re-installed using "procedure A" as long as the crankshaft has not rotated from its Initial position. if the intake manifold, cylinder head, crankshaft, camshaft, timing gear or complete engine was removed or replaced, "procedure B" must be followed to correctly install the distributor. A Diagnostic Trouble Code (DTC) code may also indicate an Incorrectly installed distributor and engine or distributor damage may occur. Procedure B must then be used. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 6814 Distributor: Adjustments Procedure A Distributor Installation and Removal Procedure A Remove or Disconnect ^ Make sure the ignition switch is "OFF." 1. Spark plug and coil leads from the distributor cap. 2. Three wire hail effect switch plug from the base of the distributor. 3. Two screws holding the distributor cap to the housing. 4. Distributor cap. A. Use a grease pencil to note the position of the rotor segment in relation to the distributor housing. Identify the mark with a 1. B. The distributor housing and intake manifold should also be marked with a grease pencil for proper alignment when reinstalling. 5. Mounting clamp hold down bolt. 6. Distributor. ^ As the distributor is being removed from the engine, you will notice the rotor move in a counter-clockwise direction, 42°. This will appear as slightly more than one clock position. Noting the position of the rotor segment, by placing a second mark on the base of the distributor, will aid in achieving proper rotor alignment during distributor installation. Be sure to identify the second mark on the base with the number 2. Install or Connect Distributor Alignment Indicator A. If the original distributor is to be replaced, rather than repaired, remove the new distributor cap. Using a grease pencil, place two marks on the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 6815 new distributor housing in the same location as the two marks on the original housing. B. When installing the distributor, align the rotor segment with the number 2 mark on the base of the distributor. Guide the distributor into place, making sure the grease pencil marks on the distributor housing and the intake manifold are in line. As the the distributor is being installed, you will notice the rotor will move in a clockwise direction, 42°. ONCE THE DISTRIBUT0R IS COMPLETELY SEATED, the rotor segment should be aligned with the number 1 mark on the base. If the rotor segment is not aligned with the number 1 mark, the gear teeth of the distributor and camshaft have meshed one or more teeth out of time. To correct this condition, remove the distributor and re-install it following the procedure at step B. 1. Distributor cap and mounting screws. Do not overtighten the screws as the boss may strip. 2. Distributor mounting clamp and tighten to proper torque. Tighten ^ Distributor clamp and bolt to 27 Nm (20 lbs. ft.) ^ Distributor cap screws to 4.5-5.0 Nm (40-45 lbs. in.) 3. Three wire hall effect switch connector to base of the distributor. 4. Spark plug and coil leads to the distributor cap. ^ If a check engine light is illuminated after installing the distributor and a DTC P1345 is found, the distributor has been installed incorrectly. You now must refer to procedure; B or proper distributor installation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 6816 Distributor: Adjustments Procedure B Distributor Installation and Removal Procedure B Remove or Disconnect ^ Make sure the ignition switch is "OFF." ^ Bring the engine up to Top Dead Center (TDC) of cylinder number 1. Make sure it is on the compression stroke. A. Remove the distributor cap screws and cap to expose the rotor. Rotor Location B. Align the pre-drilled indent hole in the distributor driven gear with the white painted alignment line on the lower portion of the shaft housing. The rotor segment should point to the cap hold area as shown in the illustration. C. Using a long screw driver, align the oil pump drive shaft in the engine in the mating drive tab in the distributor. D. Guide the distributor into place, making sure the the spark plug towers are perpendicular to the center line of the engine. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Adjustments > Camshaft Retard Offset Adjustment > Page 6817 Installed Rotor Position E. ONCE The DISTRIBUTOR IS FULLY SEATED, the rotor segment should be aligned with the pointer cast into the distributor base. This pointer will have a "8" cast into it, indicating the distributor is to be used in a 8 cylinder engine. if the rotor segment does not come within a few degrees of the pointer, the gear mesh between the distributor and camshaft may be off a tooth or more. If this is the case, repeat the procedure again to achieve proper alignment. Install or Connect 1. Cap and mounting screws. Do not overtighten as the boss may strip. 2. Distributor mounting clamp and tighten to proper torque. Tighten ^ Distributor clamp and bolt to 27 Nm (20 lbs. ft.) ^ Distributor cap screws to 4.5-5.0 Nm (40-45 lbs. in.) 3. Three wire hall effect switch plug to base of distributor. 4. Spark plug and coil leads to the distributor cap. ^ If a check engine light is illuminated after installing the distributor and a DTC P1345 is found, the distributor has been installed incorrectly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation Distributor: Service and Repair Distributor Removal & Installation Distributor Removal 1. Remove the ignition coil wire harness from the ignition coil and distributor cap. 2. Remove two screws holding the distributor cap to the housing. 3. Distributor cap. 4. Remove the distributor clamp bolt. 5. Remove the distributor and the distributor clamp. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 6820 6. Remove the distributor gasket and discard. Distributor Installation 1. Bring cylinder number one piston to Top Dead Center (TDC) of compression stroke. 2. Install the distributor cap screws. 3. Install the distributor cap. 4. Install a NEW distributor gasket onto the distributor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 6821 5. Align the indent hole on the driven gear with the paint mark on the distributor housing. 5. Ensure that the distributor rotor segment points to the cap hold area. 7. Align the slotted tang in the oil pump driveshaft with the distributor driveshaft. Rotate the oil pump driveshaft with a screwdriver if necessary. 8. Align the flat (1) in the distributor housing toward the front of the engine. 9. Install the distributor and distributor clamp. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 6822 10. Once the distributor is fully seated, align the distributor rotor segment with the number 8 pointer that is cast into the distributor base. 11. If the distributor rotor segment does not come within a few degrees of the number 8 pointer, the gear mesh between the distributor and camshaft may be off a tooth or more. Repeat the procedure in order to achieve proper alignment. Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems. 12. Install the distributor clamp bolt. Tighten the distributor clamp bolt to 25 Nm (18 ft. lbs.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 6823 13. Install the distributor cap onto the distributor. 14. Install the NEW distributor cap screws. Do not overtighten the NEW distributor cap screws. Tighten the distributor cap screws to 2.4 Nm (21 in. lbs.). 15. Install the ignition coil wire harness. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 6824 Distributor: Service and Repair Distributor Disassembly and Assembly Distributor Components NOTICE: The distributor driven gear can be installed in two positions. Make sure when installing the gear that the dimple found below the roll pin hole in the gear is on the same side as the rotor segment. The dimple will not align directly with the rotor segment if not, the gear is Installed 180° off and a no start condition may occur. Premature wear and damage may result. Remove or Disconnect 1. Two screws holding the cap to the housing. 2. Cap from the housing. 3. Two screws from the rotor. Vane Wheel In Distributor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 6825 4. Rotor. ^ Note which locating holes (B) the rotor was removed from. 5. Two screws holding the hall effect switch. 6. Hall effect switch. ^ The square cut hole (C) in the vane wheel must be aligned with the hall effect switch in order to remove the switch. 7. Roil pin from the shaft. A. Note the dimple located below the roil pin hole on the one side of the gear. The dimple will be used to properly orient the gear on the shaft during assembly. 8. Driven gear, washer, and tang washer. 9. Shaft. ^ If the shaft can't be removed from the distributor housing due to varnish buildup, use a cloth dampened with varnish remover to clean the shaft. NOTICE: Failure to keep cleaning agents away from the hall effect switch may result in premature failure. Install or Connect 1. Hall effect switch. 2. Two screws holding the hall effect switch. Do not overtighten as the base may strip. 3. Shaft. 4. Tang washer, washer, and driven gear. ^ When the driven gear is properly installed the dimple located below the roll pin hole, in the driven gear, will be on the same side as the rotor segment when the rotor is installed in the distributor. If the driven gear is installed incorrectly, the dimple will be on the opposite of the rotor segment. 5. Roll pin. 6. Rotor. ^ "A" shows the mounting holes. "B" shows the locating holes. 7. Two screws holding rotor. Tighten ^ Screws to 2.0 Nm (20 lbs. In.) Installation of the distributor into the engine will require the distributor cap off of the assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 6826 Distributor: Service and Repair Distributor Alignment/Camshaft Retard Offset Adjustment Description TEST PROCEDURE The ignition timing cannot be adjusted. The distributor may need adjusting to prevent crossfire. To insure proper alignment of the distributor, perform the following: 1. With the ignition OFF, install a scan tool to the DLC. 2. Start the engine and bring to normal operating temperature. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM. 3. Increase engine speed to 1000 RPM. 4. Monitor the Cam Retard Offset. 5. If the Cam Retard indicates a value of 0° +/-2°, the distributor is properly adjusted. 6. If the Cam Retard does not indicate 0° +/-2°, the distributor must be adjusted. ADJUSTING PROCEDURE 1. With the engine OFF, slightly loosen the distributor hold down bolt. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM. 2. Start the engine and raise engine speed to 1000 RPM. 3. Using a scan tool monitor Cam Retard Offset. 4. Rotate the distributor as follows: 4.1. To compensate for a negative reading, rotate the distributor in the counterclockwise direction. 4.2. To compensate for a positive reading, rotate the distributor in the clockwise direction. 5. Repeat step 4 until 0° +/-2°, is obtained. 6. Turn the ignition OFF. 7. Tighten the distributor hold-down bolt to 3 Nm (25 lb. ft.). 8. Start the engine, raise engine speed to 1000 RPM and recheck Camshaft Retard Offset. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 6827 Distributor: Service and Repair Distributor Assembly Replacement Removal Procedure NOTICE: If the distributor is removed from the engine, It can be re-installed using "procedure A" as long as the crankshaft has not rotated from the original position. If the intake manifold, cylinder head, crankshaft, camshaft, timing gear or complete engine was removed or replaced, "Procedure B" must be followed in order to correctly install the distributor. A DTC code may also indicate an incorrectly installed distributor and engine or distributor damage may occur. Procedure B must then be used. 1. Turn OFF the ignition switch. 2. Remove the spark plug and the ignition coil wires from distributor cap. 3. Remove the three-wire hall effect switch connector from the base of the distributor. 4. Remove the two screws holding the distributor cap to the housing. 5. Remove the distributor cap. A. Use a grease pencil in order to note the position of the rotor in relation to the distributor housing. Identify the mark with the number 1. B. Mark the distributor housing and the intake manifold with a grease pencil for proper alignment when reinstalling. 6. Remove the mounting clamp hold down bolt. 7. Remove the distributor. 8. As the distributor is being removed from the engine, you will notice the rotor move in a counter-clockwise direction about 42 degrees. This will appear as slightly more than one clock position. Noting the position of the rotor segment by placing a second mark on the base of the distributor will aid in achieving proper rotor alignment during the distributor installation. Identify the second mark on the distributor housing at number 2. Installation Procedure A 1. Remove the new distributor cap. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 6828 2. If installing a new distributor assembly, place two marks on the new distributor housing in the same location as the two marks on the original housing. 3. When installing the distributor, align the rotor with mark made at location 2.. 4. Guide the distributor into place, making sure the mounting hole in the distributor hold down base is aligned over the mounting hole in the intake manifold. 5. As the distributor is being installed, you will notice the rotor will move in a clockwise direction about 42 degrees. 6. Once the distributor is completely seated, the rotor segment should be aligned with mark on the base in location number 1. If the rotor segment is not aligned with the number 1 mark, the gear teeth of the distributor and the camshaft have meshed one or more teeth out of time. In order to correct the condition, remove the distributor and reinstall it. 7. Install the cap and the mounting screws. Do not overtighten as they may strip. Tighten Tighten the distributor cap screws to 5 Nm (45 lb in). NOTICE: Use the correct fasteners in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces inless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems. 8. Install the distributor clamp bolt. Tighten Tighten the distributor clamp bolt to to 27 Nm (20 lb ft). NOTICE: Use the correct fasteners in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 6829 paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces inless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems. 9. Install the three wire hall effect switch connector to the base of the distributor. 10. Install the spark plug and the ignition coil wires to the distributor cap. Important: If a check engine light is illuminated after installing the distributor and a DTC P1345 is found, the distributor has been installed incorrectly. Refer to procedure B for proper distributor installation. Installation Procedure B 1. Rotate the number 1 cylinder up to Top Dead Center (TDC) of the compression stroke. 2. Remove the distributor cap screws and the distributor cap to expose the rotor. 3. Align the pre-drilled indent hole in the distributor driven gear with the white alignment line on the lower portion of the shaft housing. 4. The rotor should point to the cap hold down mount nearest the flat side of the housing. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Distributor, Ignition > Component Information > Service and Repair > Distributor Removal & Installation > Page 6830 5. Using a long screw driver, align the oil pump drive shaft to the drive tab of the distributor. 6. Guide the distributor in place, ensuring that the spark plug towers are perpendicular to the centerline of engine. 7. Once the distributor is fully seated, the rotor segment should be aligned with the pointer cast into the distributor base. This pointer will have a 6 or 8 cast into it, indicating that the distributor is to be used on a 6 or 8 cylinder engine. If the rotor segment does not come within a few degrees of the pointer, the gear mesh between the distributor and the camshaft may be off a tooth or more. If this is the case, repeat the procedure again in order to achieve proper alignment. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Hall Effect Sensor, Ignition > Component Information > Description and Operation Hall Effect Sensor: Description and Operation Description The hall effect switch connects to the VCM through the primary engine harness and provides cylinder identification information. The hall effect switch is located under the distributor cap. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications Spark Plug Wire: Specifications 0-15 inch cable .................................................................................................................................... .................................................. 3,000 - 10,000 ohms. 15-25 inch cable .................................................................................................................................. .................................................. 4,000 - 15,000 ohms. 25-35 inch cable .................................................................................................................................. .................................................. 6,000 - 20,000 ohms. Longer wires should measure about 5,000 to 10,000 ohms per foot. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 6837 Spark Plug Wire: Locations Spark Plug Wire Routing Right Side Spark Plug Wire Routing Left Side Wire routings must be kept intact during service and followed exactly when wires have been disconnected or when replacement of the wires is necessary. Failure to route the wires properly can lead to radio ignition noise and crossfiring of the plugs or shorting of the leads to ground Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 6838 Spark Plug Wire: Service Precautions Service Precautions 1. Twist boots one-half turn before removing. 2. When removing the boot, do not use pliers or other tools that could tear the boot. 3. Do not force anything between the wire and the boot, or through the silicone jacket of the wiring. 4. Do not pull on the wires to remove the boot. Pull on the boot or use a tool designed for this purpose. 5. Special care should be used when installing spark plug boots to ensure the metal terminal within the boot is fully seated on the spark plug terminal and the boot has not moved on the wire. NOTE: If boot to wire movement has occurred, the boot will give a false visual impression of being fully seated. Make sure that boots have been properly assembled by pushing sideways on the in stalled boots. Failure to properly seat the terminal onto the spark plug will lead to wire core erosion and result in an engine misfire or crossfire condition, and possible internal damage to the engine. ^ If they have been correctly installed, a stiff boot with only slight looseness will be noted. If the terminal has not been properly seated on the spark plug, only the resistance of the boot will be felt when pushing sideways. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 6839 Spark Plug Wire: Testing and Inspection VISUAL INSPECTION 1. Inspect the routing of the wires. Improper routing can cause crossfiring. 2. Inspect each wire for any signs of cracks or splits in the wire. 3. Inspect each boot for signs of tears, piercing, arc through, or carbon tracking. If the boot needs to be replaced, twist it a half-turn in either direction to break the seal before pulling on the boot to remove the wire. SPARK PLUG WIRE RESISTANCE TEST 1. Disconnect both ends of each wire. Make sure the wire terminals are clean. 2. Set ohmmeter on the high scale and connect it to each end of the wire being tested. Twist the wire gently while watching ohmmeter. 3. If ohmmeter reads above 30,000 ohms (no matter how long the wire is), or fluctuates from infinity any value, replace the wire. 4. If the resistance of any wire is not within the following ranges, replace the wire being tested. - 0 to 381 mm (0 to 15 in.) wire - 3,000 to 10,000 ohms. - 381 mm to 635 mm (15 in. to 25 in.) wire - 4,000 to 15,000 ohms. - 635 mm to 889 mm (25 in. to 35 in.) wire - 6,000 to 20,000 ohms. - Longer wire - should measure about 5,000 to 10,000 ohms per foot. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 6840 Spark Plug Wire: Service and Repair Spark Plug Wire Routing Right Side Spark Plug Wire Routing Left Side SERVICE CAUTIONS 1. Twist boots one-half turn before removing. 2. When removing the boot, do not use pliers or other tools that could tear the boot. 3. Do not force anything between the wire and the boot, or through the silicone jacket of the wiring. 4. Do not pull on the wires to remove the boot. Pull on the boot or use a tool designed for this purpose. 5. Special care should be used when installing spark plug boots to ensure the metal terminal within the boot is fully seated on the spark plug terminal and the boot has not moved on the wire. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Spark Plug Wire <--> [Ignition Cable] > Component Information > Specifications > Page 6841 WARNING: If boot to wire movement has occurred, the boot will give a false visual impression of being seated. Make sure that boots have been properly assembled by pushing sideways on the installed boots. Failure to properly seat the terminal onto the spark plug will lead to wire core erosion and result in an engine misfire or crossfire condition, and possible internal damage to the engine. ^ If they have been correctly installed, a stiff boot with only slight looseness will be noted. If the terminal has not been properly seated on the spark plug, only the resistance of the boot will be felt when pushing sideways. SPARK PLUG WIRE REPLACEMENT Spark plug wire routings must be kept intact during service and followed exactly when spark plug wires have been disconnected or when replacement of the spark plug wires is necessary. Failure to route the spark plug wires properly can lead to radio noise and crossfiring of the spark plugs, or shorting of the leads to ground. The correct routing is shown in the images. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Ignition Coil > Component Information > Specifications > Electrical Specifications Ignition Coil: Electrical Specifications COIL PACK RESISTANCE SPECIFICATIONS: ^ The OEM service manual does not give a specification for coil resistance and recommends to test all other ignition components first and then switch affected coil with a good known coil and retest. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Ignition Coil > Component Information > Specifications > Electrical Specifications > Page 6846 Ignition Coil: Mechanical Specifications Ignition coil hold-down studs/bolts ............................................................................................................................................................ 27 Nm (20 lb. ft.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Ignition Coil > Component Information > Locations > Component Locations Engine Side, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Ignition Coil > Component Information > Locations > Component Locations > Page 6849 Engine Side, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Ignition Coil > Component Information > Locations > Page 6850 ICM Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Ignition Coil > Component Information > Locations > Page 6851 Ignition Coil: Description and Operation Ignition Control Driver (ICD) Module And Ignition Coil The Ignition Coil Driver Module is mounted on a bracket next to the coil. The Vehicle Control Module (VCM) signals the Ignition Control Driver (ICD) to turn "ON" primary current to the ignition coil by pulling the Ignition Control (IC) line high (4 volts). The IC turns the primary current "ON" and "OFF" by applying and removing the ground to the primary winding at the appropriate time. This module is of 'minimum function" and does not contain backup calibrations that would allow the engine to continue to rim if the IC signal is lost. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Ignition Coil > Component Information > Locations > Page 6852 Ignition Coil: Testing and Inspection IGNITION COIL TEST ^ Make sure the ignition switch is "OFF." 1. Disconnect the distributor lead and wiring from the ignition coil. CAUTION: Do not Insert the J 39200 probe into the ignition coil connectors. The female terminals could be spread and deformed, resulting In intermittent operation of the coil. Be sure to make contact with only the front edge of the terminals. 2. Connect an ohmmeter as shown in Figure, step 1. Use the high scale. The reading should be infinite. If not, replace the coil. 3. Connect the ohmmeter as shown in Figure, step 2. Use the low scale. The reading should be 0.2 - 0.5 ohms. If not, replace the coil. 4. Connect the ohmmeter as shown in Figure, step 3. Use the high scale. The meter should read 5k - 25k ohms. If not, replace the coil. 5. Reconnect the distributor lead and wiring to the coil. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Ignition Coil > Component Information > Locations > Page 6853 Ignition Coil: Service and Repair Ignition Coil Ignition Coil Mounting Remove or Disconnect NOTE: Make sure the ignition switch is "OFF." 1. Wiring connectors at the side of the coil. 2. Coil wire. 3. Studs/bolts holding the coil bracket and coil to the manifold. 4. Coil bracket and coil. ^ Drill and punch out the two rivets holding the coil to the bracket. 5. Coil from the bracket. Install or Connect NOTE: A replacement coil kit comes with two screws to attach the coil to the bracket. 1. Coil to the bracket with two screws. 2. Coil and bracket to the intake manifold with studs/bolts. Tighten ^ Ignition coil hold-down studs/bolts to 27 Nm (20 lb. ft.). 3. Coil wire. 4. Wiring connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Ignition Control Module > Component Information > Description and Operation Ignition Control Module: Description and Operation Ignition Control Driver (ICD) Module And Ignition Coil The Ignition Coil Driver Module is mounted on a bracket next to the coil. The Vehicle Control Module (VCM) signals the Ignition Control Driver (ICD) to turn "ON" primary current to the ignition coil by pulling the Ignition Control (IC) line high (4 volts). The IC turns the primary current "ON" and "OFF" by applying and removing the ground to the primary winding at the appropriate time. This module is of 'minimum function" and does not contain backup calibrations that would allow the engine to continue to rim if the IC signal is lost. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Ignition Control Module > Component Information > Description and Operation > Page 6857 Ignition Control Module: Testing and Inspection If the vehicle cranks for at least 5 seconds and the Engine Control Module doesn't see a referance signal, some Models will set a code, 42 (Hard) or 12 (Soft). If your vehicle has one of these codes, begin with the Diagnostic System Check in Computers and Controls, then proceed to the Trouble Code Chart (Yes, some vehicles have a DTC Chart for Code 12). If the vehicle does not set a code, begin with the Diagnostic System Check, and it will send you to a Diagnostic Chart that checks for your particular condition. These types of tests are found under Computers and Control Systems. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Specifications Knock Sensor: Specifications Knock sensor ....................................................................................................................................... ....................................................... 19 Nm (14 lb. ft.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Specifications > Page 6861 Knock Sensor: Locations Engine View, Rear LH side of Engine Block, below Exhaust Manifold, forward of Starter Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions Knock Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6864 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6865 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6866 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6867 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6868 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6869 Knock Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6870 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6871 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6872 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6873 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6874 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6875 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6876 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6877 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6878 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6879 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6880 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6881 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6882 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6883 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6884 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6885 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6886 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6887 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6888 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6889 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6890 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6891 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6892 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6893 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6894 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6895 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6896 Knock Sensor Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Page 6897 Knock Sensor: Description and Operation Description The Knock Sensor (KS) system is used to detect engine detonation The VCM will retard the spark timing based on the signals from the KS module. The Knock Sensor(s) produce an AC voltage that is sent to the KS module. The amount of AC voltage produced is proportional to the amount of knock. Operation An operating engine produces a normal amount of engine mechanical vibration (Noise). The knock sensor(s) will produce an AC voltage signal from this Noise. When an engine is operating, the VCM will learn the minimum and maximum frequency of the noise the engine produces. When the VCM determines that this frequency is less than or greater than the expected amount, a knock sensor DTC will set. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Knock Sensor > Component Information > Diagrams > Page 6898 Knock Sensor: Service and Repair Diagram Removal Procedure NOTE: The knock sensor is located in areas of the cylinder head. On most applications, the knock sensors are installed in a hole which is exposed to engine coolant. Care should be exercised when servicing these sensors. 1. Disconnect the negative battery cable. Important: On knock sensors which are mounted in the end of the cylinder head draining the cooling system will not be necessary. 2. Drain the cooling system. Refer to Draining and Filling Cooling System. 3. Remove the wiring harness connector from knock sensor. 4. Remove the knock sensor from cylinder head. Installation Procedure Important: Do not use silicon tape as this will insulate the sensor from the engine block. 2. After applying a water base caulk to the sensor threads, install the knock sensor into the cylinder head. Tighten ^ Tighten to 19 Nm (14 lb. ft.). 2. Connect the negative battery cable. 3. Refill cooling system if required. Refer to Draining and Filling Cooling System. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Relays and Modules - Ignition System > Ignition Control Module > Component Information > Description and Operation Ignition Control Module: Description and Operation Ignition Control Driver (ICD) Module And Ignition Coil The Ignition Coil Driver Module is mounted on a bracket next to the coil. The Vehicle Control Module (VCM) signals the Ignition Control Driver (ICD) to turn "ON" primary current to the ignition coil by pulling the Ignition Control (IC) line high (4 volts). The IC turns the primary current "ON" and "OFF" by applying and removing the ground to the primary winding at the appropriate time. This module is of 'minimum function" and does not contain backup calibrations that would allow the engine to continue to rim if the IC signal is lost. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Relays and Modules - Ignition System > Ignition Control Module > Component Information > Description and Operation > Page 6903 Ignition Control Module: Testing and Inspection If the vehicle cranks for at least 5 seconds and the Engine Control Module doesn't see a referance signal, some Models will set a code, 42 (Hard) or 12 (Soft). If your vehicle has one of these codes, begin with the Diagnostic System Check in Computers and Controls, then proceed to the Trouble Code Chart (Yes, some vehicles have a DTC Chart for Code 12). If the vehicle does not set a code, begin with the Diagnostic System Check, and it will send you to a Diagnostic Chart that checks for your particular condition. These types of tests are found under Computers and Control Systems. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Camshaft Position Sensor: Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6909 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6910 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6911 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6912 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6913 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6914 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6915 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Page 6916 Camshaft Position Sensor: Specifications Camshaft position sensor retaining screw ........................................................................................................................................... 4-6 Nm (35-53 lb. in.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Technical Service Bulletins > Page 6917 Engine View, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Camshaft Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6920 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6921 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6922 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6923 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6924 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6925 Camshaft Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6926 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6927 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6928 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6929 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6930 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6931 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6932 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6933 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6934 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6935 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6936 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6937 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6938 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6939 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6940 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6941 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6942 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6943 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6944 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6945 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6946 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6947 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6948 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6949 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6950 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6951 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Diagrams > Page 6952 Camshaft Position Sensor: Description and Operation Camshaft Position Sensor The Camshaft Position (CMP) sensor is located within the distributor. It's operation is very similar to the Crankshaft Position (CKP) sensor however it will provide one pulse per camshaft revolution (1x signal). This signal is not detrimental to the driveability of the vehicle. The Vehicle Control Module (VCM) utilizes this signal in conjunction with the crankshaft position to determine which cylinder(s) are misfiring. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Testing and Inspection > Cam Signal Camshaft Position Sensor: Testing and Inspection Cam Signal The VCM uses this signal to determine the position of the #1 piston during its power stroke. This signal is used by the VCM to calculate fuel injection mode of operation. A loss of this signal will set DTC P0340. If the cam signal is lost while the engine is running, the fuel injection system will shift to a calculated fuel injection mode based on the last fuel injection pulse, and the engine will continue to run. The engine can be restarted and will run in the calculated mode as long as the fault is present Refer to Diagnostic Trouble Code (DTC) P0340 Camshaft Position Sensor (CKP) Sensor Circuit. See: Computers and Control Systems/Testing and Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Camshaft Position Sensor > Component Information > Testing and Inspection > Page 6955 Camshaft Position Sensor: Service and Repair REMOVAL PROCEDURE 1. Disconnect the negative battery cable. 2. Disconnect the electrical connector from the camshaft position sensor. 3. Remove the camshaft position sensor retaining screw. 4. Remove the camshaft position sensor. INSTALLATION PROCEDURE 1. Install the camshaft position sensor. 2. Install the camshaft position sensor retaining screw, torque to 4-6 Nm (35-53 lb. in.). 3. Connect the electrical connector. 4. Connect the negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Customer Interest: > 00-06-04-014 > Apr > 00 > Engine - No/Hard/Slow Start/Backfire/Kickback Crankshaft Position Sensor: Customer Interest Engine - No/Hard/Slow Start/Backfire/Kickback File In Section: 06 - Engine/Propulsion System Bulletin No.: 00-06-04-014 Date: April, 2000 TECHNICAL Subject: No, Hard, or Slow Start, Backfire or "Kickback" During Crank/Start, "Grinding" or Unusual Noises During Crank, DTC P0338 (Replace Crankshaft Position Sensor) Models: 1999-2000 Cadillac Escalade 1995-2000 Chevrolet and GMC SIT Models 1996-2000 Chevrolet and GMC C/K, M/L, G, P Models 1996-2000 Oldsmobile Bravada with 4.3 L, 5.0 L, 5.7 L or 7.4 L Engine (VINs W, X, M, R, J RPOs L35, LF6, L30, L31, L29) Condition: Some customers may comment on one or more of the following conditions: ^ Backfire during crank/start ^ "Kickback" during crank/start ^ "No" start ^ "Slow" or "hard" start/crank ^ "Grinding" or unusual noises during crank/start ^ Cracked or broken engine block at the starter boss ^ Broken starter drive housing ^ Broken starter ring gear on flywheel ^ Any combination of the above Cause: A condition may exist that allows the crankshaft position sensor to command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss. Correction: Inspect for a stored powertrain DTC code P0338. This DTC will NOT illuminate the "Service Engine Soon" light. If this code is stored, the Crankshaft Position Sensor, P/N 10456607, MUST be replaced and the remaining components inspected for damage (engine block at the starter boss, the starter drive housing, and the engine flywheel starter ring gear). Notice: When DTC code P0338 is set, failure to replace the Crankshaft Position Sensor could result in repeated inoperative conditions of the starter or flywheel. Important: Some flywheel wear is normal; broken or missing teeth and/or cracks, are not normal. Parts Information Parts are currently available from GMSPO. Warranty Information: For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 00-06-04-014 > Apr > 00 > Engine - No/Hard/Slow Start/Backfire/Kickback Crankshaft Position Sensor: All Technical Service Bulletins Engine - No/Hard/Slow Start/Backfire/Kickback File In Section: 06 - Engine/Propulsion System Bulletin No.: 00-06-04-014 Date: April, 2000 TECHNICAL Subject: No, Hard, or Slow Start, Backfire or "Kickback" During Crank/Start, "Grinding" or Unusual Noises During Crank, DTC P0338 (Replace Crankshaft Position Sensor) Models: 1999-2000 Cadillac Escalade 1995-2000 Chevrolet and GMC SIT Models 1996-2000 Chevrolet and GMC C/K, M/L, G, P Models 1996-2000 Oldsmobile Bravada with 4.3 L, 5.0 L, 5.7 L or 7.4 L Engine (VINs W, X, M, R, J RPOs L35, LF6, L30, L31, L29) Condition: Some customers may comment on one or more of the following conditions: ^ Backfire during crank/start ^ "Kickback" during crank/start ^ "No" start ^ "Slow" or "hard" start/crank ^ "Grinding" or unusual noises during crank/start ^ Cracked or broken engine block at the starter boss ^ Broken starter drive housing ^ Broken starter ring gear on flywheel ^ Any combination of the above Cause: A condition may exist that allows the crankshaft position sensor to command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an inoperative condition to the starter drive housing, the engine flywheel starter ring gear, or the engine block at the outside edge of the starter boss. Correction: Inspect for a stored powertrain DTC code P0338. This DTC will NOT illuminate the "Service Engine Soon" light. If this code is stored, the Crankshaft Position Sensor, P/N 10456607, MUST be replaced and the remaining components inspected for damage (engine block at the starter boss, the starter drive housing, and the engine flywheel starter ring gear). Notice: When DTC code P0338 is set, failure to replace the Crankshaft Position Sensor could result in repeated inoperative conditions of the starter or flywheel. Important: Some flywheel wear is normal; broken or missing teeth and/or cracks, are not normal. Parts Information Parts are currently available from GMSPO. Warranty Information: For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Crankshaft Position Sensor: All Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6973 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6974 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6975 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6976 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6977 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6978 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6979 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis Crankshaft Position Sensor: All Technical Service Bulletins Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis File In Section: 6E - Engine Fuel & Emission Bulletin No.: 61-65-60A Date: March, 1998 SERVICE MANUAL UPDATE Subject: Section 6E - Engine Controls - Revised Diagnostic Trouble Code (DTC) P1345 Models: 1996-97 Chevrolet and GMC S/T, M/L, C/K, G, P3 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, M, R, J - RPOs L35, L30, L31, L29) This bulletin is being revised to add the M/L and S/T models and also include page numbers in the 1996 and 1997 Service Manuals. Please discard Corporate Bulletin Number 61-65-60 (Section 6E Engine Fuel & Emission). This bulletin revises the Diagnostic Trouble Code (DTC) P1345. When diagnosing this DTC, the technician is instructed to use this revised DTC P1345 table and supporting text, One diagnostic is to be used for the 4.3L V-6 engines. One diagnostic is to be used for the 5.0L, 5.7L and 7.4L V-6 engine. Camshaft Retard Offset Adjustment procedure for the V-8 engine only. The Service Manuals and the appropriate page numbers are listed as shown: 1996 ^ Pages 6E-270 and 271 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L, 5.7L, 7.4L ^ Pages 6E-269 and 270 - C/K Truck 4.3L ^ Pages 6E-748 and 749 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-261 and 262 - M/L Van 4.3L ^ Pages 3B-268 and 269 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6E-638 and 639 - S/T Truck 4.3L 1997 ^ Pages 6E-271 and 272 - G Van 4.3L ^ Pages 6E-735 and 736 - G Van 5.0L. 5.7L, 7.4L ^ Pages 6E-295 and 296 - C/K Truck 4.3L ^ Pages 6E-799 and 800 - C/K Truck 5.0L, 5.7L, 7.4L ^ Pages 6E-278 and 279 - M/L Van 4.3L ^ Pages 3B-286 and 289 - P3 Truck 4.3L, 5.7L, 7.4L ^ Pages 6-1094 and 1095 - S/T Truck 4.3L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6985 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6986 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6987 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6988 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6989 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6990 DTC P1345 CKP/CMP CORRELATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Crankshaft Position Sensor: > 61-65-60A > Mar > 98 > Engine Controls - Revised DTC P1345 (CKP/CMP) Diagnosis > Page 6991 REPAIR INSTRUCTIONS CAMSHAFT RETARD OFFSET ADJUSTMENT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Page 6992 Crankshaft Position Sensor: Specifications Crankshaft Position Sensor mounting bolts ................................................................................................................................................. 8 Nm (71 lb. In.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Technical Service Bulletins > Page 6993 Engine Side, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions Crankshaft Position Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6996 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6997 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6998 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 6999 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7000 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7001 Crankshaft Position Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7002 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7003 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7004 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7005 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7006 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7007 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7008 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7009 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7010 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7011 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7012 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7013 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7014 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7015 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7016 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7017 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7018 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7019 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7020 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7021 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7022 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7023 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7024 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7025 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7026 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7027 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Page 7028 Crankshaft Position Sensor: Description and Operation DESCRIPTION The Crankshaft Position (CKP) Sensor is located in the front engine cover and is perpendicular to the crankshaft target wheel. The air gap between the sensor and the wheel is preset and not adjustable. The target wheel has three slots 60° apart and is keyed to the crankshaft. As the target wheel rotates, the slots passing by the sensor create a change in the magnetic field of the sensor which results in an induced voltage pulse. One revolution of the crankshaft results in three pulses (3x signal). Based on these pulses, the VCM is able to determine crankshaft position and engine speed. The VCM then activates the fuel injector and provides a spark to the Distributor. The relation between the crankshaft position sensor and the target wheel is crucial. The sensor must be exactly perpendicular to the target wheel with the correct air gap. OPERATION The crankshaft position sensor provides the VCM with crankshaft speed and crankshaft position. The VCM utilizes this information to determine if an engine Misfire is present. The VCM monitors the Crankshaft Position Sensor (CKP) sensor for momentarily drop in crankshaft speed to determine if a misfire is occurring. When the VCM detects a misfire, a Diagnostic Trouble Code (DTC) P0300 will set. The VCM also monitors the CKP sensor signal circuit for malfunctions. The VCM monitors CKP signal and the High and Low resolution signals. The VCM calculates these signals to determine a ratio. When the VCM detects that the ratio is out of normal operating range, the VCM will set a Diagnostic Trouble Code (DTC) P0337 or a DTC P0338. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Page 7029 Crankshaft Position Sensor: Service and Repair REMOVAL PROCEDURE 1. Remove the electrical connector. 2. Remove the sensor hold down bolt. 3. Remove the sensor from the timing cover. NOTE: When installing or removing a crankshaft position (CKP) sensor make sure the sensor is fully seated and held stationary in the front cover before torquing the hold down bolt into the front cover. A sensor which is not seated may result in erratic operation and lead to the setting of false codes. 4. Inspect the sensor O-ring for wear, cracks or leakage. Replace if necessary. Lube the new O-ring with clean engine oil before installing. INSTALLATION PROCEDURE NOTE: Make certain that the Crankshaft Position (CKP) sensor mounting surfaces are clean and free of burrs before installing the CKP sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Crankshaft Position Sensor > Component Information > Diagrams > Page 7030 1. Install the sensor into the timing cover. 2. Install the sensor hold down bolt. Tighten ^ Tighten the hold down bolt to 8 Nm (71 lb. in.). 3. Install the electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Hall Effect Sensor, Ignition > Component Information > Description and Operation Hall Effect Sensor: Description and Operation Description The hall effect switch connects to the VCM through the primary engine harness and provides cylinder identification information. The hall effect switch is located under the distributor cap. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder Technical Service Bulletin # 73-01-09 Date: 971001 Starting - Revised Procedures for Inop Ignition Cylinder File In Section: 0 - General Information Bulletin No.: 73-01-09 Date: October, 1997 INFORMATION Subject: New Tumblers for Cylinder Recoding, Revised Repair Procedures for Inoperative Ignition Cylinders (Seized/Won't Rotate), Labor Operation/Time Allowances Models: 1995-97 Buick Skylark, Riviera 1995-97 Chevrolet Cavalier 1997 Chevrolet Corvette, Malibu, Venture 1995-97 Oldsmobile Achieva 1997 Oldsmobile Aurora, Cutlass, Silhouette 1995-97 Pontiac Grand Am, Sunfire 1997 Pontiac Grand Prix, Trans Sport 1995-97 Chevrolet and GMC C/K, S/T Models 1996-97 Chevrolet and GMC G, M/L Vans 1996-97 Oldsmobile Bravada The information in this bulletin concerns new designed tumblers for recoding lock cylinders that use double sided reversible keys, revised procedures for servicing ignition lock cylinders that are seized or not able to rotate and revised labor time guide information and allowances. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 7043 The existing labor operation (E7200) has been changed to include "Add" conditions for cylinders that will not rotate. New Tumblers New tumblers are available from GMSPO for recoding lock cylinders that use double-sided reversible keys. These new tumblers should be used immediately and information about the disposition of original tumblers will be provided by GMSPO. Figure 1 shows the new tumbler profile. The shaded area was part of the original tumbler profile, and is removed on the new tumblers. The new part numbers for the tumblers are as follows: Part No. 2852732 = Tumbler # 1 Part No. 2852733 = Tumbler # 2 Part No. 2852734 = Tumbler # 3 Part No. 2852735 = Tumbler # 4 Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. New Procedures For Seized/Won't Rotate Column Mounted Ign. CYL. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 7044 A. On G, J and N Models: DO NOT REMOVE THE STEERING COLUMN as indicated in the Service Manual procedure. 1. Remove the tilt lever, upper and lower column covers. 2. Drill hole in module housing as indicated in the illustration using a short drill bit (1/8" followed by 9/32") and 90 degree drill motor or go degree drill attachment to break or access the retaining spring for the lock cylinder button, see Figure 2. 3. Using a pick or needle nose pliers, remove the retaining spring from the hole. 4. Using pliers, grasp and remove the retaining button for the cylinder. 5. Remove the cylinder from the housing. 6. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 7. Install the new cylinder and reinstall the steering column components. B. On U, W, and light duty trucks, follow the Service Manual procedure for keys missing, or cylinders won't rotate. Procedure: Instrument Panel Mounted Switches Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 7045 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder Technical Service Bulletin # 73-01-09 Date: 971001 Starting - Revised Procedures for Inop Ignition Cylinder File In Section: 0 - General Information Bulletin No.: 73-01-09 Date: October, 1997 INFORMATION Subject: New Tumblers for Cylinder Recoding, Revised Repair Procedures for Inoperative Ignition Cylinders (Seized/Won't Rotate), Labor Operation/Time Allowances Models: 1995-97 Buick Skylark, Riviera 1995-97 Chevrolet Cavalier 1997 Chevrolet Corvette, Malibu, Venture 1995-97 Oldsmobile Achieva 1997 Oldsmobile Aurora, Cutlass, Silhouette 1995-97 Pontiac Grand Am, Sunfire 1997 Pontiac Grand Prix, Trans Sport 1995-97 Chevrolet and GMC C/K, S/T Models 1996-97 Chevrolet and GMC G, M/L Vans 1996-97 Oldsmobile Bravada The information in this bulletin concerns new designed tumblers for recoding lock cylinders that use double sided reversible keys, revised procedures for servicing ignition lock cylinders that are seized or not able to rotate and revised labor time guide information and allowances. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 7051 The existing labor operation (E7200) has been changed to include "Add" conditions for cylinders that will not rotate. New Tumblers New tumblers are available from GMSPO for recoding lock cylinders that use double-sided reversible keys. These new tumblers should be used immediately and information about the disposition of original tumblers will be provided by GMSPO. Figure 1 shows the new tumbler profile. The shaded area was part of the original tumbler profile, and is removed on the new tumblers. The new part numbers for the tumblers are as follows: Part No. 2852732 = Tumbler # 1 Part No. 2852733 = Tumbler # 2 Part No. 2852734 = Tumbler # 3 Part No. 2852735 = Tumbler # 4 Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. New Procedures For Seized/Won't Rotate Column Mounted Ign. CYL. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 7052 A. On G, J and N Models: DO NOT REMOVE THE STEERING COLUMN as indicated in the Service Manual procedure. 1. Remove the tilt lever, upper and lower column covers. 2. Drill hole in module housing as indicated in the illustration using a short drill bit (1/8" followed by 9/32") and 90 degree drill motor or go degree drill attachment to break or access the retaining spring for the lock cylinder button, see Figure 2. 3. Using a pick or needle nose pliers, remove the retaining spring from the hole. 4. Using pliers, grasp and remove the retaining button for the cylinder. 5. Remove the cylinder from the housing. 6. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 7. Install the new cylinder and reinstall the steering column components. B. On U, W, and light duty trucks, follow the Service Manual procedure for keys missing, or cylinders won't rotate. Procedure: Instrument Panel Mounted Switches Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 7053 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Page 7054 Ignition Switch Lock Cylinder: Service and Repair The procedure has been updated by TSB# 73-01-09 Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Specifications Knock Sensor: Specifications Knock sensor ....................................................................................................................................... ....................................................... 19 Nm (14 lb. ft.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Specifications > Page 7058 Knock Sensor: Locations Engine View, Rear LH side of Engine Block, below Exhaust Manifold, forward of Starter Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions Knock Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7061 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7062 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7063 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7064 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7065 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7066 Knock Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7067 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7068 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7069 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7070 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7071 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7072 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7073 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7074 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7075 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7076 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7077 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7078 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7079 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7080 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7081 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7082 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7083 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7084 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7085 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7086 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7087 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7088 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7089 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7090 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7091 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7092 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Diagram Information and Instructions > Page 7093 Knock Sensor Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Page 7094 Knock Sensor: Description and Operation Description The Knock Sensor (KS) system is used to detect engine detonation The VCM will retard the spark timing based on the signals from the KS module. The Knock Sensor(s) produce an AC voltage that is sent to the KS module. The amount of AC voltage produced is proportional to the amount of knock. Operation An operating engine produces a normal amount of engine mechanical vibration (Noise). The knock sensor(s) will produce an AC voltage signal from this Noise. When an engine is operating, the VCM will learn the minimum and maximum frequency of the noise the engine produces. When the VCM determines that this frequency is less than or greater than the expected amount, a knock sensor DTC will set. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Sensors and Switches - Ignition System > Knock Sensor > Component Information > Diagrams > Page 7095 Knock Sensor: Service and Repair Diagram Removal Procedure NOTE: The knock sensor is located in areas of the cylinder head. On most applications, the knock sensors are installed in a hole which is exposed to engine coolant. Care should be exercised when servicing these sensors. 1. Disconnect the negative battery cable. Important: On knock sensors which are mounted in the end of the cylinder head draining the cooling system will not be necessary. 2. Drain the cooling system. Refer to Draining and Filling Cooling System. 3. Remove the wiring harness connector from knock sensor. 4. Remove the knock sensor from cylinder head. Installation Procedure Important: Do not use silicon tape as this will insulate the sensor from the engine block. 2. After applying a water base caulk to the sensor threads, install the knock sensor into the cylinder head. Tighten ^ Tighten to 19 Nm (14 lb. ft.). 2. Connect the negative battery cable. 3. Refill cooling system if required. Refer to Draining and Filling Cooling System. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Spark Plug > Component Information > Specifications Spark Plug: Specifications Spark plug type .................................................................................................................................... ....................................................................... 41-932 Spark plug gap ................................................ ....................................................................................................................................................... 0.060 inch Spark plugs (new cylinder head) ........................................................................................ ........................................................................ 30 Nm (22 lb. ft.) Spark plugs (used cylinder head) ... ............................................................................................................................................................ 20 Nm (14 lb. ft.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Spark Plug > Component Information > Specifications > Page 7099 Spark Plug: Description and Operation DESCRIPTION Resistor-type. tapered-seat spark plugs are used. No gasket is used on these plugs. These spark plugs are a High Efficiency (HE) spark plug that has a fine wire electrode, nickel plated shell and a platinum pad across from the electrode. These features give the HE spark plug long life durability. Refer to Specifications or to the Vehicle Emissions Control Information label on the fan shroud for correct gap information. See: Specifications CONSTRUCTION If the spark plug shell hex is not fully engaged in the spark plug socket wrench, the socket may cock at an angle and cause insulator cracking and/or breakage during plug installation or removal. OPERATION Normal or average service is assumed to be a mixture of idling, low speed, and high speed operation with some of each making up the daily total driving. Occasional or intermittent high-speed driving is essential to good spark plug performance. It provides increased and sustained combustion heat that burns away any excess deposits of carbon or oxide that may have accumulated from frequent idling or continual stop-and-go or slow-speed driving. Spark plugs are protected by an insulating boot made of special heat-resistant material that covers the spark plug terminal and extends downward over a portion of the plug insulation These boots prevent flash-over with resultant missing of the engine, even though a film is allowed to accumulate on the exposed portion of plug porcelains. Do not mistake corona discharge for flash-over or a shorted insulator. Corona discharge is a steady blue light appearing around the insulator. just above the shell crimp It is the visible evidence of a high-tension field, and has no effect on ignition performance. Usually it can be detected only in darkness. This discharge may repel dust particles, leaving a clear ring on the insulator just above the shell. This ring is sometimes mistakenly regarded as evidence that combustion gases have blown out between the shell and insulator. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Spark Plug > Component Information > Specifications > Page 7100 Spark Plug Diagnosis Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Ignition System > Spark Plug > Component Information > Specifications > Page 7101 Spark Plug: Service and Repair CAUTION ^ Allow the engine to cool before removing the spark plugs. Attempting to remove the plugs from a hot engine may cause the plug to seize, causing damage to the cylinder head threads. ^ Clean the spark plug recess area before removing the plug. Failure to do so can result in engine damage due to dirt or foreign material entering the cylinder head or contamination of the cylinder head threads. Contaminated threads may prevent proper seating of a new plug. ^ Do not install plugs that are either hotter or colder than the heat range specified. Using plugs of the wrong heat range can severely damage the engine. REMOVE OR DISCONNECT ^ Make sure the ignition switch is OFF. CAUTION: Twist the spark plug boot one-half turn to release it. Pull on the spark plug boot only. Do not pull on the wire or the spark plug lead may be damaged. 1. Spark plug wires and boots. ^ Label the plug wires. CAUTION: Be sure to use J 39358 or equivalent spark plug socket Failure to do so could cause cracking of the insulator and arcing inside the plug, resulting in engine misfire. 2. Spark plugs using J 39358 or equivalent. Inspect ^ Each spark plug for wear and gap. ^ Spark plugs should be gapped to 0.060 inch. INSTALL OR CONNECT CAUTION: Make sure each sparkplug threads smoothly into the cylinder head and is fully seated. Cross-threading or falling to fully seat spark plugs can cause overheating of the plugs, exhaust blow-by, or thread damage. 1. Spark plugs. Tighten ^ Spark plugs to 30 Nm (22 lb. ft.) in a new cylinder head and 20 Nm (14 lb. ft.) in a used head. 2. Wire and boot assemblies. Refer to Spark Plug Wiring and Boots for precautions. See: Spark Plug Wire/Service Precautions Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Interlock Solenoid > Component Information > Locations Shift Interlock Solenoid: Locations RH side of steering column, under Support bracket. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling Shift Solenoid: Customer Interest A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling File In Section: 7 Transmission Bulletin No.: 77-71-77 Date: December, 1997 Subject: Loss of 4th Gear, Slipping in 4th Gear, Busy 3-4 Shifting or TCC Cycling (Replace Shift Solenoids) Models: 1996-97 Chevrolet and GMC C/K, G, P Models with HYDRA-MATIC 4L8OE Transmission (RPO MT1) Condition Some owners may comment about a loss of 4th gear, slipping in 4th gear, busy 3-4 shifting or Torque Converter Clutch (TCC) cycling and no DTC's are setting. Cause Shift solenoid leaking hydraulically. Correction If normal diagnosis does not provide a correction, follow the solenoid test procedure listed. Replace the shift solenoid if it fails the test. Also verify that the transmission cooling system is operating properly. Service Information (figure 1) Starting June 23, 1997 (Julian date 174) all HYDRA-MATIC 4L80-E transmissions are being built with the new solenoid assemblies. The new solenoids will service all 1991 through 1997 4L80-E applications. The above listed conditions occur mainly on high duty cycle applications and/or when the transmission is operated under high temperature conditions. Each solenoid may be tested for leaking using the following test: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling > Page 7116 1. Remove the solenoid from the control valve body. Refer to the Service Manual for the proper procedure. 2. Clamp a piece of 1/2 inch I.D. rubber hose over the fluid inlet end of the solenoid. 3. Connect a wire from one of the solenoid terminals to the negative terminal (ground) of a battery. 4. Apply compressed air to the rubber hose. Do not use air pressure in excess of 120 psi. Excessive pressure will not allow the check ball to seat properly. 5. Connect a wire from the other solenoid to the positive terminal (12 volts) of the battery. 6. Observe the air flow through the solenoid. Replace the solenoid if there is an air leak when the solenoid is energized. Parts Information New Part Number Description 10478140 1-2 & 3-4 Shift Solenoid (black) 10478141 2-3 Shift Solenoid (white) Parts are currently available through GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift Shift Solenoid: Customer Interest A/T - Engine Speed Flare During Part Throttle Downshift File In Section: 7 - Transmission Bulletin No.: 67-71-47 Date: July, 1996 Subject: 3-2 Part Throttle Downshift Flare (Replace 3-2 Solenoid) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1996 Chevrolet Camaro, Caprice, Corvette 1996 Pontiac Firebird 1996 Chevrolet and GMC C/K, M/L, S/T, G Models 1996 Oldsmobile Bravada with HYDRA-MATIC 4L60-E (RPO M30) Condition (Figures 1 and 2) Some owners of the above models with a HYDRA-MATIC 4L60-E transmission (built before May 24, 1996/Julian Date 6145) may experience an engine speed flare of 1000-2000 RPM, during a part throttle downshift at 19-31 mph. This condition will not set any DTC's (Diagnostic Trouble Codes). Cause Exhaust seat on the 3-2 control solenoid backing out. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift > Page 7121 Correction (Figure 3) Replace the 3-2 control solenoid. Julian Date on the solenoid will be May 13, 1996 (6134) or later. Parts Information New Part Number Description 24209121 Solenoid, 3-2 Control Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time K6559 Replace 3-2 Use published labor Control Solenoid operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling Shift Solenoid: All Technical Service Bulletins A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling File In Section: 7 Transmission Bulletin No.: 77-71-77 Date: December, 1997 Subject: Loss of 4th Gear, Slipping in 4th Gear, Busy 3-4 Shifting or TCC Cycling (Replace Shift Solenoids) Models: 1996-97 Chevrolet and GMC C/K, G, P Models with HYDRA-MATIC 4L8OE Transmission (RPO MT1) Condition Some owners may comment about a loss of 4th gear, slipping in 4th gear, busy 3-4 shifting or Torque Converter Clutch (TCC) cycling and no DTC's are setting. Cause Shift solenoid leaking hydraulically. Correction If normal diagnosis does not provide a correction, follow the solenoid test procedure listed. Replace the shift solenoid if it fails the test. Also verify that the transmission cooling system is operating properly. Service Information (figure 1) Starting June 23, 1997 (Julian date 174) all HYDRA-MATIC 4L80-E transmissions are being built with the new solenoid assemblies. The new solenoids will service all 1991 through 1997 4L80-E applications. The above listed conditions occur mainly on high duty cycle applications and/or when the transmission is operated under high temperature conditions. Each solenoid may be tested for leaking using the following test: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling > Page 7127 1. Remove the solenoid from the control valve body. Refer to the Service Manual for the proper procedure. 2. Clamp a piece of 1/2 inch I.D. rubber hose over the fluid inlet end of the solenoid. 3. Connect a wire from one of the solenoid terminals to the negative terminal (ground) of a battery. 4. Apply compressed air to the rubber hose. Do not use air pressure in excess of 120 psi. Excessive pressure will not allow the check ball to seat properly. 5. Connect a wire from the other solenoid to the positive terminal (12 volts) of the battery. 6. Observe the air flow through the solenoid. Replace the solenoid if there is an air leak when the solenoid is energized. Parts Information New Part Number Description 10478140 1-2 & 3-4 Shift Solenoid (black) 10478141 2-3 Shift Solenoid (white) Parts are currently available through GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 377148A > Nov > 96 > A/T - Shift Solenoid Update Shift Solenoid: All Technical Service Bulletins A/T - Shift Solenoid Update File In Section: 7 Transmission Bulletin No.: 37-71-48A Date: November, 1996 INFORMATION Subject: Transmission Product Updates (New Shift Solenoids) Models: 1991-97 Chevrolet and GMC C/K, P, G Models 1991 Chevrolet and GMC R/V Models with HYDRA-MATIC 4L8O-E Transmission (RPO MT1) This bulletin is being revised to update the part numbers and to include 1995-97 model years. Please discard Corporate Bulletin Number 377148 (Section 7 - Transmission). Service Information Starting August 14, 1996 (Julian date 226) all HYDRA-MATIC 4L80-E transmissions are being built with the new solenoid assemblies. The new solenoids are serviced for all 1991 through 1997 4L80-E applications. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 377148A > Nov > 96 > A/T - Shift Solenoid Update > Page 7132 Parts Information Previous Part New Part Description 10478125 10478132 Valve assembly, 1-2 Shift Solenoid (Black) 10478126 10478133 Valve assembly, 2-3 Shift Solenoid (White) Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift Shift Solenoid: All Technical Service Bulletins A/T - Engine Speed Flare During Part Throttle Downshift File In Section: 7 - Transmission Bulletin No.: 67-71-47 Date: July, 1996 Subject: 3-2 Part Throttle Downshift Flare (Replace 3-2 Solenoid) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1996 Chevrolet Camaro, Caprice, Corvette 1996 Pontiac Firebird 1996 Chevrolet and GMC C/K, M/L, S/T, G Models 1996 Oldsmobile Bravada with HYDRA-MATIC 4L60-E (RPO M30) Condition (Figures 1 and 2) Some owners of the above models with a HYDRA-MATIC 4L60-E transmission (built before May 24, 1996/Julian Date 6145) may experience an engine speed flare of 1000-2000 RPM, during a part throttle downshift at 19-31 mph. This condition will not set any DTC's (Diagnostic Trouble Codes). Cause Exhaust seat on the 3-2 control solenoid backing out. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift > Page 7137 Correction (Figure 3) Replace the 3-2 control solenoid. Julian Date on the solenoid will be May 13, 1996 (6134) or later. Parts Information New Part Number Description 24209121 Solenoid, 3-2 Control Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time K6559 Replace 3-2 Use published labor Control Solenoid operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Shift Solenoid: > 83-90-12 > Aug > 98 > Tools - Keyless Entry Transmitter Tester Keyless Entry Transmitter: All Technical Service Bulletins Tools - Keyless Entry Transmitter Tester File In Section: 9 - Accessories Bulletin No.: 83-90-12 Date: August, 1998 INFORMATION Subject: Essential Tool J 43241 Remote Keyless Entry and Passive Keyless Entry Transmitter Tester Models: 1990-99 Passenger Cars and Trucks with Remote Keyless Entry or Passive Keyless Entry Systems A new essential tool, J 43241 Remote Keyless Entry Transmitter Tester, has been sent to all GM Dealers. This tester can be used on all RKE and PKE systems, on past as well as current models. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Shift Solenoid: > 83-90-12 > Aug > 98 > Tools - Keyless Entry Transmitter Tester > Page 7143 Important: Before using the tester and the diagnostic chart, the following two steps must be performed. 1. Verify that the keyless entry transmitter is the correct model for the vehicle remote system. An incorrect model transmitter may pass this test, but may not activate the vehicle remote system. The correct transmitter can usually be identified by part number. 2. Ensure that the transmitter is synchronized with the vehicle (if applicable). Refer to Transmitter Synchronization in the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Shift Solenoid: > 66-90-03 > Jun > 97 > Keyless Entry - Unintended Release of Rear Hatch Keyless Entry Transmitter: All Technical Service Bulletins Keyless Entry - Unintended Release of Rear Hatch File In Section: 9 - Accessories Bulletin No.: 66-90-03 Date: June, 1997 Subject: Unintended Release of Rear Hatch (Replace Transmitter Cover) Models: 1994-96 Chevrolet and GMC C/K, S/T, M/L, G Models 1994 Oldsmobile Bravada 1996 Oldsmobile Bravada Condition An owner may report that the Rear Hatch Releases without their being aware of it. Cause The Keyless Entry Transmitter Button is unintentionally bumped activating the hatch release. Correction Replace the Keyless Entry Transmitter Cover. The revised cover has a deeper recess around the release button making it less prone to inadvertent bumping. Parts Information P/N Description Qty 15740707 Bezel, Transmitter Cover 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time R4490 Control Assembly 0.3 hr Cover - Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Shift Solenoid: > 83-90-12 > Aug > 98 > Tools - Keyless Entry Transmitter Tester > Page 7153 Important: Before using the tester and the diagnostic chart, the following two steps must be performed. 1. Verify that the keyless entry transmitter is the correct model for the vehicle remote system. An incorrect model transmitter may pass this test, but may not activate the vehicle remote system. The correct transmitter can usually be identified by part number. 2. Ensure that the transmitter is synchronized with the vehicle (if applicable). Refer to Transmitter Synchronization in the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Specifications > 4L60-E Automatic Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Specifications > 4L60-E Automatic Transmission > Page 7160 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Locations > 4L60-E Automatic Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Locations > 4L60-E Automatic Transmission > Page 7163 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission Shift Solenoid: Service and Repair 4L60-E Automatic Transmission Pan and Filter Assembly PAN AND FILTER ASSEMBLY Pan, Filter And Seal Removal CLEAN - Exposed ends of bottom pan screws and spray with penetrating oil. REMOVE OR DISCONNECT 1. Screws (76), oil pan (75) and gasket (73). 2. Oil filter (72) and filter seal (71). - Filter seal may be stuck in the pump. INSPECT - Filter (72), open filter by prying the metal crimping away from the top of the filter (black) and pull apart. The filter may contain evidence for root cause diagnosis. Clutch material. - Bronze slivers indicating bushing wear. - Steel particles. Valve Body and Wiring Harness VALVE BODY AND WIRING HARNESS Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7166 Valve Body Bolt Location Control Valve And Pressure Switch Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7167 Manual Valve Link Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7168 Valve Body Checkballs Case Checkballs And Filters REMOVE OR DISCONNECT 1. Electrical connections from components. 2. TCC PWM Solenoid Retainer Clip (379) and Solenoid (396). 3. TCC Solenoid bolts (68) and solenoid assembly (66) with O-ring seal (65) and wiring harness. 4. Pressure switch assembly bolts (70) and pressure switch assembly (69). 5. Accumulator cover bolts (58 and 59) and 1-2 accumulator cover and pin assembly (57). 6. 1-2 accumulator piston (56) and seal (55). 7. Spring (54). 8. Dipstick stop bracket (93). REMOVE OR DISCONNECT 1. Bolt (64) and manual detent spring assembly (63). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7169 2. Wiring harness retaining bolts. REMOVE OR DISCONNECT 1. Remaining valve body bolts (62). 2. Manual valve link (89). 3. Control valve assembly (60). 4. Bolts (58 and 59), accumulator cover (57), piston (56, spring (54) and spring (54A). 5. Bolts (77) and plate (53). 6. Spacer plate (48) and spacer plate gaskets (47 and 52). 7. Spring (46), piston (44), and pin (43). - Seven checkballs are located under the valve body and one is located in the case. The large copper flash colored ball is # 1A checkball (91). Valve Body and Associated Parts VALVE BODY AND ASSOCIATED PARTS Accumulator Assembly, Spacer Plate And Gaskets Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7170 Case Checkballs And Filters TOOL REQUIRED: - J 25025-5 Guide Pins NOTICE: The use of a honing stone, fine sandpaper or crocus cloth is not recommended for servicing stuck valves. All valve lands have sharply machined corners that are necessary for "cleaning" the bore. If these corners are rounded, foreign material could wedge between the valve and bore causing the valve to stick. If it is found necessary to clean a valve, "micro fine" lapping compound 900 grit or finer should be used. Too much "lapping" of a valve will cause excessive clearances and increase the chance of a valve not operating. INSTALL OR CONNECT 1. The wiring harness pass-thru connector into the case. 2. The 3-4 accumulator pin (43) into the case. 3. The 3-4 accumulator piston seal (45) onto the 3-4 accumulator piston. 4. The 3-4 accumulator piston (44) onto the pin. - The end with three legs must face the valve body. 5. The 3-4 accumulator piston spring (46). INSTALL OR CONNECT 1. Checkball (91) into case as shown. - Retain with Transjel TM J 36850 or equivalent. 2. J 25025-5 into the case. 3. Screens onto spacer plate as shown. 4. Spacer plate to case gasket (47) and spacer plate to valve body gasket (52) onto the spacer plate (48). - Gasket (47) identified by a "C". Gasket (52) identified by a "V". - Retain with Transjel TM J 36850 or equivalent. 5. Spacer plate and gaskets onto the case. IMPORTANT - Be careful not to damage screens when installing the spacer plate and gaskets. 6. Spacer plate support (53) and bolts (77). TIGHTEN - Bolts to 11 Nm (8 lb. ft.) Control Valve Body CONTROL VALVE BODY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7171 Case Checkballs And Filters Filter Screen - Locations Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7172 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7173 Control Valve Assembly - Legend Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7174 Valve Body Checkball Locations Valve Body Bolt Locations Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7175 Manual Valve Link Outside Electrical Connector CLEAN - Control valve assembly thoroughly in clean solvent. A. Move the valves with a pick or small screwdriver to dislodge any dirt or debris that may have accumulated. B. Air dry. REMOVE OR DISCONNECT IMPORTANT - Some valves are under pressure - cover the bores while removing roll pins and retainer clips. - Valves, springs and bushings must be laid out on a clean surface in the exact sequence they are removed. 1. Pressure control solenoid retainer bolt (364) retainer (378) and solenoid. 2. Bore plug retainer clip (395), bore plug (376) and valve train (374 and 375). 3. 2-3 shift solenoid retainer (379), solenoid (367) and valve train (368 and 369). 4. 1-2 shift solenoid retainer (379), solenoid (367) and valve train (365 and 366). 5. Accumulator valve train retainer pin (360), bore plug (373) and valve train (370 and 371). 6. Forward accumulator cover bolts (364) and cover (363). 7. Forward accumulator spring (356), piston (354) and pin (355). 8. Lo overrun valve spring (362) and valve (361). 9. Retainer pin (360), bore plug (359) and forward abuse valve train (357 and 358). 10. Manual valve (340). 11. 3-2 control solenoid retainer clip (379) and solenoid (394). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7176 12. Bore plug retainer (395), bore plug (381) and 3-2 control valve train (391 - 393). 13. 3-2 downshift bore plug retainer (395), bore plug (381) and valve train (389 - 390). 14. Reverse abuse bore plug retainer pin (360), bore plug (359) and valve train (387 - 388). 15. 3-4 shift valve bore plug retainer (395), bore plug (381) and valve train (385 - 386). 16. 3-4 relay bore plug retainer (395), bore plug (381) and valve train (382 - 384). 17. Torque converter clutch signal valve bore plug retainer (395), bore plug (381) and valve (380). CLEAN - All valves, springs, bushings and control valve body in clean solvent. - Dry using compressed air. INSPECT - All valves and bushings for: Porosity - Scoring - Nicks - Scratches - Springs for damaged or distorted coils. - Valve body casting for: Porosity - Cracks - Inter connected oil passages - Damaged machined surfaces ASSEMBLE - Control valve assembly (350) exactly as shown. Notice the position of the valve lands and bushing passages. - Position the pressure control solenoid so the connector tabs face outward. NOTICE: TCC PWM solenoid (396) cannot be installed until TCC solenoid has been installed and torqued to proper specifications. INSTALL OR CONNECT 1. Checkballs into the valve body assembly (350). - Retain with Transjell TM J 36850 or equivalent. 2. Valve body assembly (350). - Connect the manual valve link (89) to the inside detent lever (88). - Be careful not to damage screens when installing the valve body assembly. 3. Wiring harness (66), manual spring assembly (63), pressure switch assembly(69), dipstick, stop bracket (93) and all remaining valve body bolts. NOTICE: Torque valve body bolts in a spiral pattern starting from the center. If bolts are torqued at random, valve bores may be distorted and inhibit valve operation. 4. TCC solenoid (66) and bolts (68). TIGHTEN - Bolts to 11 Nm (8 lb. ft.). 5. TCC PWM solenoid (396), and retainer clip (379). INSTALL OR CONNECT - Wiring harness connections to electrical components. - To correctly hook up the wires, see the wiring diagrams. - The pressure control solenoid (377) has two different colored connectors. The black connector should be installed on the tab farthest from the valve body. INSTALL OR CONNECT 1. Parking bracket (86). TIGHTEN - Bolts to 31 Nm (23 lb. ft.). 2. The 1-2 accumulator piston seal (55) onto the 1-2 accumulator piston (56). 3. The 1-2 accumulator spring (54) and 1-2 accumulator inner spring (54A) onto the piston (56). 4. The 1-2 accumulator piston (56) into the 1-2 accumulator cover and pin assembly (57). - The three legs on the piston must face away from the case when installed. 5. The 1-2 accumulator cover and pin assembly (57) onto the case. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7177 TIGHTEN - Torque to 11 Nm (8 lb. ft.). Pan and Filter Assembly PAN AND FILTER ASSEMBLY Case, Pan And Filter Assembly INSTALL OR CONNECT 1. Filter seal (71) into the pump. 2. Oil filter (72). 3. Oil pan gasket (73). 4. Chip magnet (74) onto oil pan (75). 5. Oil pan (75) and bolts (76). TIGHTEN - Torque to 12 Nm (9 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7178 Shift Solenoid: Service and Repair 4L80-E Automatic Transmission Pan and Filter Assembly PAN AND FILTER ASSEMBLY Pan, Filter And Seal Removal REMOVE OR DISCONNECT 1. Drain the transmission fluid Out case extension by rotating transmission to a vertical position. 2. Seventeen bolts (27), using 10 mm socket, drain transmission fluid. 3. Pan (28), seal (29) and magnet (30). IMPORTANT - Seal (29) is reusable. 4. Filter assembly (31). INSPECT - Filter neck seal (32), replace if necessary. Wire Harness Assembly WIRE HARNESS ASSEMBLY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7179 Pan, Filter And Seal Removal REMOVE OR DISCONNECT 1. Wire harness connectors from electrical components. NOTICE: Excessive force on the case pass through connector may damage the connector. IMPORTANT - If the wire harness assembly does not need servicing, it is not necessary to remove it from the case. 2. Wire harness assembly (34) from case using a 1-5/16" 12 point socket to release the connector retaining clips. Control Valve Assembly CONTROL VALVE ASSEMBLY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7180 REMOVE OR DISCONNECT 1. Rotate transmission bottom pan surface up and lock in place. 2. Wire harness assembly (34) connectors from components. IMPORTANT - If the wire harness assembly does not need servicing, it is not necessary to remove it from the case. - Use a cap to cover electrical pin at case connection. 3. Six bolts (76) using 8 mm socket, and transmission fluid pressure switch assembly (40). NOTICE: Be sure five O-rings are attached to transmission fluid pressure switch assembly. 4. Twenty-one bolts (35) using 10 mm socket, from valve body assembly, manual detent spring and roller assembly (41). 5. Three wiring clamps (33), fluid level indicator stop (43), one bolt (36) using 10 mm socket, lube pipe (39), lube pipe retainer (37) and clamp (38). 6. Control valve assembly (44) including the accumulator housing assembly (51), valve body gaskets (45 and 48), spacer plate (46) and accumulator gasket (47). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7181 7. Manual valve (319) from control valve assembly (44) to prevent any damage. 8. Checkballs (54) from case passages. NOTICE: Do not use a magnet. It could cause checkball(s) to be magnetized causing metal particles to stick to the ball. 9. Pulse Width Modulated (PWM) solenoid screen (75). INSPECT - Screen PWM solenoid (75), replace if necessary. DISASSEMBLE Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7182 - Control valve assembly. A. Position as shown on a clean surface. B. Remove blind hole retainer pins with a drill bit. CAUTION: Some valves are under pressure - cover the bores while removing the retaining pins or personal injury could result. C. Remove valve trains, shift solenoids (311 and 313), PCS (320), PWM solenoid (323), PCS screen (302) and shift solenoid filter (317). D. Valves, springs, bushings and pistons must be laid out on a clean surface. CLEAN - All valves, springs, bushings, pistons, control valve body and accumulator housing in clean solvent. - Dry using compressed air. INSPECT 1. All valves, pistons and bushings for: - Porosity. - Scoring. - Nicks. - Scratches. 2. Pistons for: - Seal damage. 3. Springs for: - Damaged or distorted coils. 4. Valve body casting and accumulator housing for: - Porosity. - Cracks. - Interconnected passages. - Damaged machined surfaces. 5. Solenoid connectors and filter (317). 6. PCS (Pressure Control Solenoid) screen (302). Control Valve Assembly/Accumulator Housing CONTROL VALVE ASSEMBLY/ACCUMULATOR HOUSING Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7183 Control Valve Assembly/Accumulator Housing Accumulator Housing Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7184 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7185 Torque Sequence And Guide Pin Location Fig. 11 Check Ball Location. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7186 Fig. 10 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7187 Torque Sequence, Control Valve And Switch Assembly NOTICE: The use of a honing stone, fine sandpaper or crocus cloth is not recommended for servicing stuck valves. All valve lands have sharply machined comers that are necessary for cleaning the bore. If these corners are rounded, foreign material could wedge between the valve and the bore causing the valve to stick. If it is found necessary to clean a valve, micro fine lapping compound 900 grit (J 38459) or finer should be used. Too much lapping of the valve will cause excessive clearances and increase the chance of a valve not operating. CLEAN - Control valve assembly and accumulator housing (51) thoroughly in clean solvent. - Air dry. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7188 Accumulator Housing Assembly ACCUMULATOR HOUSING ASSEMBLY Control Valve Assembly/Accumulator Housing Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7189 Accumulator Housing Assembly DISASSEMBLE 1. Six bolts (53), using 8 mm socket. 2. Accumulator housing assembly. 3. Gasket accumulator housing (47). 4. Spacer plate (46). 5. Gasket (45) valve body spacer. 6. Snap ring (402) from outside housing, pin (408), snap ring (402), piston (407) and spring (49). 7. 3rd clutch piston (405) and spring (50). 8. Seals (404 and 406). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7190 CLEAN - All components. INSPECT - All valves, pistons, springs and seals for: - Porosity. - Scoring. - Nicks. - Scratches. Accumulator Housing Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7191 ASSEMBLE - Accumulator housing assembly components exactly as shown. Notice the positions of the pistons. Control Valve Assembly CONTROL VALVE ASSEMBLY Control Valve Assembly ASSEMBLE - Control valve assembly components exactly as shown. Notice the position of the valve lands and bushing passages. Control Valve Assembly/Accumulator Housing Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7192 CONTROL VALVE ASSEMBLY AND ACCUMULATOR HOUSING Control Valve Assembly/Accumulator Housing Torque Sequence And Guide Pin Location TOOL REQUIRED: - Guide Pin J 25025-5 ASSEMBLE 1. Guide pin J 25025-5 into valve body. Located at back bolt hole of detent spring and roller assembly bolt bole. 2. Gasket (45) valve body to spacer plate. 3. Spacer plate (46). 4. Gasket (47) accumulator housing to spacer plate. 5. Accumulator housing assembly (51) onto valve body assembly (44). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7193 6. Six bolts (53) using (8 mm) socket through accumulator housing into valve body assembly. Torque Sequence And Guide Pin Location NOTE: Start accumulator housing bolts finger tight and work towards opposite end. TIGHTEN - Bolt (53) to 11 Nm (97 lb. in.). 7. Remove guide pin J 25025-5. Fig. 11 Check Ball Location. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7194 Fig. 10 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7195 Torque Sequence, Control Valve And Switch Assembly INSTALL OR CONNECT 1. Install checkballs (54) in proper location into case fluid passages. Use TRANSJEL TM J 36850 or equivalent to hold in place. NOTICE: Do not use any type of grease to retain parts during assembly of this unit. Greases other than the recommended assembly lube will change transmission fluid characteristics and cause undesirable shift conditions and/or filter clogging. - # 2 checkball is used only on RCP RDP, ZJP and ZLP models. 2. PWM solenoid screen (75). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7196 3. Gasket (48) spacer plate to case. 4. Manual valve (319) into valve body. 5. Complete valve body assembly (44) onto case (7). Use 1 25025-5 guide pin set. IMPORTANT - Attach manual valve to detent lever. 6. Transmission fluid pressure switch assembly (40) onto valve body assembly (44). 7. Spring and roller assembly (41) into place. 8. Three wiring clamps (33), fluid indicator stop (43) and lube pipe clamp (38). 9. Twenty-one bolts (35). Using 10 mm socket. 10. Six bolts (76) using 8 mm socket into transmission fluid pressure switch assembly (40). 11. Lube pipe (39) long end into case, short end into valve body. 12. Lube pipe retainer (37) with short bolt (36). TIGHTEN - Bolts (35, 36 and 76) to 11 Nm (97 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7197 Torque Sequence, Control Valve And Switch Assembly NOTICE: Torque valve body bolts in a spiral pattern starting from the center. If bolts are torqued at random, valve bores may be distorted and inhibit valve operation. 13. Attach wiring harness (34) to 5 connectors. - Put large end into case first, pressure switch hook up, 1-2 shift solenoid (purple) and 2-3 shift solenoid (tan), PWM (Pulse Width Modulated) solenoid and PCS (Pressure Control Solenoid). Pan and Filter Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7198 PAN AND FILTER ASSEMBLY Installing Pan And Filter INSTALL OR CONNECT 1. Seal (32) inside of case (7). 2. Filter assembly (31). 3. Bottom pan seal (29). 4. Magnet (30) into bottom pan. 5. Pan (29). 6. Seventeen bolts (27) using 10 mm socket. TIGHTEN - Bolts (27) to 24 Nm (18 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON Torque Converter Clutch Solenoid: Customer Interest A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-023B Date: March, 2002 TECHNICAL Subject: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1999-2000 Cadillac Escalade 1996-2000 Chevrolet Camaro, Corvette 1996-2000 Pontiac Firebird 1996-2000 Chevrolet and GMC Light Duty Truck Models 1996-2000 Oldsmobile Bravada with 4L60-E Automatic Transmission (RPO M30) Built Prior to January 15, 2000 (Julian Date 0015) This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 Transmission/Transaxle). Condition Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated. Diagnosis Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs. The scan tool may show a DTC P1870 set as a history code. A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93° C (200°F). Cause The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply. Important: ^ DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code. ^ When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result. ^ This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle). ^ When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code. ^ When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL). Correction Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 7207 regulator and isolator valves. Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body. ^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears). ^ The torque converter is not blue or overheated. ^ The transmission fluid is not burned or has no burned odor ^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 7208 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON Torque Converter Clutch Solenoid: All Technical Service Bulletins A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-023B Date: March, 2002 TECHNICAL Subject: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1999-2000 Cadillac Escalade 1996-2000 Chevrolet Camaro, Corvette 1996-2000 Pontiac Firebird 1996-2000 Chevrolet and GMC Light Duty Truck Models 1996-2000 Oldsmobile Bravada with 4L60-E Automatic Transmission (RPO M30) Built Prior to January 15, 2000 (Julian Date 0015) This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 Transmission/Transaxle). Condition Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated. Diagnosis Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs. The scan tool may show a DTC P1870 set as a history code. A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93° C (200°F). Cause The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply. Important: ^ DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code. ^ When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result. ^ This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle). ^ When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code. ^ When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL). Correction Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 7214 regulator and isolator valves. Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body. ^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears). ^ The torque converter is not blue or overheated. ^ The transmission fluid is not burned or has no burned odor ^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 7215 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Relays and Modules Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder Control Module: Customer Interest A/T - Upshift Flare/No 3rd or 4th/Launch Shudder File In Section: 07 - Transmission/Transaxle Bulletin No.: 00-07-30-026 Date: December 2000 TECHNICAL Subject: Automatic Transmission 1-2 and/or 2-3 Upshift Slip/Flare, No 3rd or 4th gear, Launch Shudder (Revise VCM Wiring) Models: 1996 Chevrolet and GMC C/K, S/T, M/L, G1, G2, P3 Models 1996 Oldsmobile Bravada with VCM and 4L60-E (M30) or 4L80-E (MT1) Automatic Transmission This bulletin is being reissued to ensure that correct procedures are followed for this condition. Please discard Corporate Bulletin Number 66-71-03A (Section 7 - Automatic Transmission). When performing a transmission replacement labor operation K7000 on these vehicles with a 4L60-E or 4L80-E, you must include front chassis wire repair labor operation N6112. Inspect the VCM to verify the latest part number revision (16244210). Condition Some owners may comment that the automatic transmission has either a slip or flare on the 1-2 and/or 2-3 upshift, or no 3rd or 4th gear, or launch shudder. Upon investigation, the technician may find a DTC P1870 stored in the VCM. Cause A poor internal ground between the two circuit boards of the VCM may cause the VCM to command erratic line pressure at the pressure control (PC) solenoid valve. Correction Using harness jumper wire and instruction kit, P/N 12167310, revise the wiring harness at the VCM connector. Corrections were made to the VCM beginning 2/14/96. The corrected VCMs are identified with service number 16244210 on the VCM identification label. Procedure The following is a summary of the instructions included with the service kit: 1. Remove the negative terminal from the battery. 2. Move the wire located at connector J3 (WHITE/GREY/CLEAR), pin 18 to connector J1 (BLUE), pin 23. 3. Install the jumper wire between connector J2 (RED), pin 26 and connector J3 (WHITE/GREY/CLEAR), pin 18. 4. Install the tag included in the kit around the. VCM wiring harness. This tag notes that the wiring harness has been modified. 5. Reconnect the negative battery terminal. Road test to verify that the condition has been corrected. If any of the following conditions are noted, the transmission should be repaired or replaced using the most cost effective method. Canadian dealers should repair the transmission. ^ Transmission fluid oxidation or excessive sediment. ^ Transmission slip or flare after this service fix is performed. ^ DTC P1870 is stored on a 4L60-E (M30). The following tools are available from Kent-Moore (1-800-345-2233) for use in removing and relocating the VCM wires: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Relays and Modules Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder > Page 7226 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Relays and Modules Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder Control Module: All Technical Service Bulletins A/T - Upshift Flare/No 3rd or 4th/Launch Shudder File In Section: 07 - Transmission/Transaxle Bulletin No.: 00-07-30-026 Date: December 2000 TECHNICAL Subject: Automatic Transmission 1-2 and/or 2-3 Upshift Slip/Flare, No 3rd or 4th gear, Launch Shudder (Revise VCM Wiring) Models: 1996 Chevrolet and GMC C/K, S/T, M/L, G1, G2, P3 Models 1996 Oldsmobile Bravada with VCM and 4L60-E (M30) or 4L80-E (MT1) Automatic Transmission This bulletin is being reissued to ensure that correct procedures are followed for this condition. Please discard Corporate Bulletin Number 66-71-03A (Section 7 - Automatic Transmission). When performing a transmission replacement labor operation K7000 on these vehicles with a 4L60-E or 4L80-E, you must include front chassis wire repair labor operation N6112. Inspect the VCM to verify the latest part number revision (16244210). Condition Some owners may comment that the automatic transmission has either a slip or flare on the 1-2 and/or 2-3 upshift, or no 3rd or 4th gear, or launch shudder. Upon investigation, the technician may find a DTC P1870 stored in the VCM. Cause A poor internal ground between the two circuit boards of the VCM may cause the VCM to command erratic line pressure at the pressure control (PC) solenoid valve. Correction Using harness jumper wire and instruction kit, P/N 12167310, revise the wiring harness at the VCM connector. Corrections were made to the VCM beginning 2/14/96. The corrected VCMs are identified with service number 16244210 on the VCM identification label. Procedure The following is a summary of the instructions included with the service kit: 1. Remove the negative terminal from the battery. 2. Move the wire located at connector J3 (WHITE/GREY/CLEAR), pin 18 to connector J1 (BLUE), pin 23. 3. Install the jumper wire between connector J2 (RED), pin 26 and connector J3 (WHITE/GREY/CLEAR), pin 18. 4. Install the tag included in the kit around the. VCM wiring harness. This tag notes that the wiring harness has been modified. 5. Reconnect the negative battery terminal. Road test to verify that the condition has been corrected. If any of the following conditions are noted, the transmission should be repaired or replaced using the most cost effective method. Canadian dealers should repair the transmission. ^ Transmission fluid oxidation or excessive sediment. ^ Transmission slip or flare after this service fix is performed. ^ DTC P1870 is stored on a 4L60-E (M30). The following tools are available from Kent-Moore (1-800-345-2233) for use in removing and relocating the VCM wires: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Relays and Modules Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder > Page 7232 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Relays and Modules Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Control Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules Relay Module: All Technical Service Bulletins Electrical - MIL ON/DTC's Set By Various Control Modules TECHNICAL Bulletin No.: 09-06-03-004D Date: December 08, 2010 Subject: Intermittent No Crank/No Start, No Module Communication, MIL, Warning Lights, Vehicle Messages or DTCs Set by Various Control Modules - Diagnosing and Repairing Fretting Corrosion (Disconnect Affected Connector and Apply Dielectric Lubricant) Models: 2011 and Prior GM Passenger Cars and Trucks Attention: This repair can be applied to ANY electrical connection including, but not limited to: lighting, body electrical, in-line connections, powertrain control sensors, etc. DO NOT over apply lubricant to the point where it prevents the full engagement of sealed connectors. A light coating on the terminal surfaces is sufficient to correct the condition. Supercede: This bulletin is being revised to update the Attention statement and add the 2011 model year. Please discard Corporate Bulletin Number 09-06-03-004C (Section 06 Engine/Propulsion System). Condition Some customers may comment on any of the following conditions: - An intermittent no crank/no start - Intermittent malfunction indicator lamp (MIL) illumination - Intermittent service lamp illumination - Intermittent service message(s) being displayed The technician may determine that he is unable to duplicate the intermittent condition. Cause This condition may be caused by a buildup of nonconductive insulating oxidized debris known as fretting corrosion, occurring between two electrical contact surfaces of the connection or connector. This may be caused by any of the following conditions: - Vibration - Thermal cycling - Poor connection/terminal retention - Micro motion - A connector, component or wiring harness not properly secured resulting in movement On low current signal circuits this condition may cause high resistance, resulting in intermittent connections. On high current power circuits this condition may cause permanent increases in the resistance and may cause a device to become inoperative. Representative List of Control Modules and Components The following is only a representative list of control modules and components that may be affected by this connection or connector condition and DOES NOT include every possible module or component for every vehicle. - Blower Control Module - Body Control Module (BCM) - Communication Interface Module (CIM) - Cooling Fan Control Module - Electronic Brake Control Module (EBCM) - Electronic Brake and Traction Control Module (EBTCM) - Electronic Suspension Control (ESC) Module - Engine Control Module (ECM) - Heating, Ventilation and Air Conditioning (HVAC) Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Relays and Modules Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Control Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 7238 - HVAC Actuator - Inflatable Restraint Sensing and Diagnostic Module (SDM) - Any AIR BAG module - Seatbelt Lap Anchor Pretensioner - Seatbelt Retractor Pretensioner - An SIR system connection or connector condition resulting in the following DTCs being set: B0015, B0016, B0019, B0020, B0022, or B0023 - Powertrain Control Module (PCM) - Remote Control Door Lock Receiver (RCDLR) - Transmission Control Module (TCM) Correction Important DO NOT replace the control module, wiring or component for the following conditions: - The condition is intermittent and cannot be duplicated. - The condition is present and by disconnecting and reconnecting the connector the condition can no longer be duplicated. Use the following procedure to correct the conditions listed above. 1. Install a scan tool and perform the Diagnostic System Check - Vehicle. Retrieve and record any existing history or current DTCs from all of the control modules (refer to SI). ‹› If any DTC(s) are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). ‹› If DTCs are not set, refer to Symptoms - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). 2. When identified, use the appropriate DTC Diagnostics, Symptoms, Schematics, Component Connector End Views and Component Locator documents to locate and disconnect the affected harness connector(s) which are causing the condition. Note Fretting corrosion looks like little dark smudges on electrical terminals and appear where the actual electrical contact is being made. In less severe cases it may be unable to be seen or identified without the use of a magnifying glass. Important DO NOT apply an excessive amount of dielectric lubricant to the connectors as shown, as hydrolock may result when attempting to mate the connectors. Use ONLY a clean nylon brush that is dedicated to the repair of the conditions in this bulletin. 3. With a one-inch nylon bristle brush, apply dielectric lubricant to both the module/component side and the harness side of the affected connector(s). 4. Reconnect the affected connector(s) and wipe away any excess lubricant that may be present. 5. Attempt to duplicate the condition by using the following information: - DTC Diagnostic Procedure - Circuit/System Description - Conditions for Running the DTC - Conditions for Setting the DTC - Diagnostic Aids - Circuit/System Verification ‹› If the condition cannot be duplicated, the repair is complete. ‹› If the condition can be duplicated, then follow the appropriate DTC, Symptom or Circuit/System Testing procedure (refer to SI). Repair Order Documentation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Relays and Modules Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Control Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 7239 Important The following information MUST be documented on the repair order. Failure to do so may result in a chargeback. - Customer vehicle condition. - Was a Service Lamp or Service Message illuminated? If yes, specify which Service Lamp or Service Message. - Was a DTC(s) set? If yes, specify which DTC(s) were set. - After following the procedure contained within this bulletin, could the condition be duplicated? ‹› If the condition was not duplicated, then document the affected module/component connector name and number on the repair order. - If the condition was duplicated after the procedure contained within this bulletin was followed, and additional diagnosis led to the replacement of a module or component, the SI Document ID Number MUST be written on the repair order. Parts Information Alternate Distributor For All of North America Note NyoGel(R) 760G Lubricant* is equivalent to GMSPO P/N 12377900, and P/N 10953529 (Canada), specified for use to correct the condition in this bulletin. *We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for, or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Relays and Modules Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Control Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 7240 For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to refer to the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Relays and Modules Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Control Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 7246 - HVAC Actuator - Inflatable Restraint Sensing and Diagnostic Module (SDM) - Any AIR BAG module - Seatbelt Lap Anchor Pretensioner - Seatbelt Retractor Pretensioner - An SIR system connection or connector condition resulting in the following DTCs being set: B0015, B0016, B0019, B0020, B0022, or B0023 - Powertrain Control Module (PCM) - Remote Control Door Lock Receiver (RCDLR) - Transmission Control Module (TCM) Correction Important DO NOT replace the control module, wiring or component for the following conditions: - The condition is intermittent and cannot be duplicated. - The condition is present and by disconnecting and reconnecting the connector the condition can no longer be duplicated. Use the following procedure to correct the conditions listed above. 1. Install a scan tool and perform the Diagnostic System Check - Vehicle. Retrieve and record any existing history or current DTCs from all of the control modules (refer to SI). ‹› If any DTC(s) are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). ‹› If DTCs are not set, refer to Symptoms - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). 2. When identified, use the appropriate DTC Diagnostics, Symptoms, Schematics, Component Connector End Views and Component Locator documents to locate and disconnect the affected harness connector(s) which are causing the condition. Note Fretting corrosion looks like little dark smudges on electrical terminals and appear where the actual electrical contact is being made. In less severe cases it may be unable to be seen or identified without the use of a magnifying glass. Important DO NOT apply an excessive amount of dielectric lubricant to the connectors as shown, as hydrolock may result when attempting to mate the connectors. Use ONLY a clean nylon brush that is dedicated to the repair of the conditions in this bulletin. 3. With a one-inch nylon bristle brush, apply dielectric lubricant to both the module/component side and the harness side of the affected connector(s). 4. Reconnect the affected connector(s) and wipe away any excess lubricant that may be present. 5. Attempt to duplicate the condition by using the following information: - DTC Diagnostic Procedure - Circuit/System Description - Conditions for Running the DTC - Conditions for Setting the DTC - Diagnostic Aids - Circuit/System Verification ‹› If the condition cannot be duplicated, the repair is complete. ‹› If the condition can be duplicated, then follow the appropriate DTC, Symptom or Circuit/System Testing procedure (refer to SI). Repair Order Documentation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Relays and Modules Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Control Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 7247 Important The following information MUST be documented on the repair order. Failure to do so may result in a chargeback. - Customer vehicle condition. - Was a Service Lamp or Service Message illuminated? If yes, specify which Service Lamp or Service Message. - Was a DTC(s) set? If yes, specify which DTC(s) were set. - After following the procedure contained within this bulletin, could the condition be duplicated? ‹› If the condition was not duplicated, then document the affected module/component connector name and number on the repair order. - If the condition was duplicated after the procedure contained within this bulletin was followed, and additional diagnosis led to the replacement of a module or component, the SI Document ID Number MUST be written on the repair order. Parts Information Alternate Distributor For All of North America Note NyoGel(R) 760G Lubricant* is equivalent to GMSPO P/N 12377900, and P/N 10953529 (Canada), specified for use to correct the condition in this bulletin. *We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for, or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Relays and Modules Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Control Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 7248 For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to refer to the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Technical Service Bulletins > A/T - Park/Neutral Switch Connector Cannot Be Removed Transmission Position Switch/Sensor: Technical Service Bulletins A/T - Park/Neutral Switch Connector Cannot Be Removed File In Section: 7 - Transmission Bulletin No.: 83-71-10 Date: May, 1998 Subject: Park (Neutral Position Switch Connector Cannot be Removed (Replace Switch and Connectors) Models: 1997-98 Chevrolet Corvette 1995-98 Chevrolet and GMC S/T Models 1996-98 Chevrolet and GMC M/L, P Models 1996-99 Chevrolet and GMC C/K, G Models 1996-98 Oldsmobile Bravada Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer conditions, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to insure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to insure water-tight connections. Parts Information P/N Description 12450016 Switch 15305925 4-Way Connector Assembly 15305887 7-Way Connector Assembly Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 7257 Transmission Position Switch/Sensor: Locations Park/Neutral Position Switch Electronic 4-Speed Automatic Overdrive Transmission Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 7258 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions Transmission Position Switch/Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7261 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7262 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7263 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7264 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7265 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7266 Transmission Position Switch/Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7267 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7268 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7269 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7270 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7271 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7272 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7273 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7274 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7275 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7276 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7277 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7278 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7279 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7280 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7281 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7282 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7283 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7284 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7285 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7286 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7287 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7288 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7289 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7290 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7291 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7292 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7293 Transmission Position Switch/Sensor: Connector Views C1: Transmission Range Switch C2: Transmission Range Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7294 Transmission Position Switch/Sensor: Electrical Diagrams Electronic PRNDL Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7295 Starter And Charging (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 7296 Transmission Position Switch/Sensor: Testing and Inspection Pressure Switch Assembly Resistance Check (1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 7297 Pressure Switch Assembly Resistance Check (2 Of 2) Tools Required - J 39775 4L60E Jumper Harness - J 39200 Digital Multimeter - J 35616 Connector Test Adapter Kit Important: Whenever the transmission 20-way connector is disconnected and the engine is running, multiple DTCs will set. Be sure to clear these codes when you are finished with this procedure Important: This procedure tests the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) circuits and the Automatic Transmission Fluid Temperature (TFT) Sensor circuit. Do not use this procedure to test other Automatic Transmission circuits, refer to 4L60-E Automatic Transmission Internal Wiring Harness check. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 7298 Transmission Position Switch/Sensor: Adjustments PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 7299 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 7300 Transmission Position Switch/Sensor: Service and Repair PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 7301 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Speed Sensor, A/T > Component Information > Locations > Transmission Output Speed Sensor, 4L80E Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Speed Sensor, A/T > Component Information > Locations > Transmission Output Speed Sensor, 4L80E > Page 7306 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > Customer Interest: > 77-71-53 > Apr > 97 > A/T - Chuggle/Surge on TCC Apply/No DTC's PROM - Programmable Read Only Memory: Customer Interest A/T - Chuggle/Surge on TCC Apply/No DTC's File In Section: 7 - Transmission Bulletin No.: 77-71-53 Date: April, 1997 Subject: Chuggle/Surge on TCC Apply/No DTC's (Reflash PCM) Models: 1996-97 Chevrolet and GMC C/K, G Models with 5.7L Engine (VIN R - RPO L31) and HYDRA-MATIC 4L60-E Transmission (RPO M30) Condition Some owners of the above models may experience a chuggle/surge when TCC is applied under light throttle acceleration. Cause Engine inputs (Combustion events) exciting the vehicle platform/driveline or tire balance may be a contributing factor. Correction First ensure the most recent engine, not transmission calibration has been installed (Corp. # 76-65-04) and check tire balance. A new transmission calibration to correct chuggle/surge is available for use on vehicles with persistent concerns only. Important: This calibration will raise TCC engagement approximately 7-10 mph depending on application. This calibration should not be installed until the engine calibration listed above has been installed. Installation of this calibration may lead to decreased fuel economy due to TCC engagement at higher speeds. Reflash the Powertrain Control Module with the appropriate part numbers below. Refer to your Service Manual for proper procedure. Parts Information This new calibration will be available starting with the 1997 Disc 4 update. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J6355 Reflash Control Module Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > Customer Interest: > 76-65-04 > Mar > 97 > Engine Controls Driveability/Starting Issues/DTC's/MIL PROM - Programmable Read Only Memory: Customer Interest Engine Controls Driveability/Starting Issues/DTC's/MIL MALFUNCTION INDICATOR LIGHT (MIL) ON, POOR DRIVEABILITY # 76-65-04 - (Mar 3, 1997) SUBJECT: MALFUNCTION INDICATOR LIGHT (MIL) ON, POOR DRIVEABILITY CONDITIONS (PERFORM FLASH CALIBRATION) MODELS: 1996-97 CHEVROLET AND GMC LIGHT DUTY TRUCKS 1996-97 CHEVROLET TILTMASTER AND GMC FORWARD W4 MODELS 1996-97 OLDSMOBILE BRAVADA WITH 4.3L, 5.0L, 5.7L ENGINES (VINS X, W, M, R - RPOS LF6, L35, L30, L31) CONDITION: AN OWNER MAY REPORT THAT THE MALFUNCTION INDICATOR LIGHT (MW) IS ON AND/OR THE VEHICLE HAS ONE OR MORE OF THE FOLLOWING DRIVEABILITY CONDITIONS. 1. 5.7L (L31) ONLY: SURGE OR CHUGGLE AT SPEEDS OF 42 TO 65 MPH WHILE AT STEADY SPEED OR UNDER LIGHT TO MODERATE ACCELERATION WITH THE TCC APPLIED. 2. MIL ON WITH DTC P0172 OR P0175 STORED BUT NO REPORTED DRIVEABILITY SYMPTOMS. 3. MIL ON WITH DTC P1406 STORED AND ROUGH ENGINE OR POOR DRIVEABILITY SYMPTOMS. 4. WHEN OPERATING AT ALTITUDES ABOVE 5,000 FEET, AN AUDIBLE SPARK KNOCK NOISE IS HEARD. 5. HESITATION AND/OR MISFIRE DURING LIGHT CRUISE CONDITIONS DUE TO IGNITION CROSS-FIRE WITH NO DTC STORED. THIS WILL ONLY OCCUR ON V-6 ENGINES WITH CAM RETARD OFFSET IN EXCESS OF 26 DEGREES AND V-8'S WITH CAM RETARD OFFSET IN EXCESS OF 15 DEGREES. 6. THE MIL MAY BE ON AND A DTC STORED FOR AN ENGINE MISFIRE BUT NO MISFIRE OCCURRED. 7. ENGINE EXHIBITS AN IDLE SPEED SURGE OR ROLL. 1996 MODELS ONLY 8. MIL ON WITH DTC P0102 STORED BUT NO REPORTED DRIVEABILITY SYMPTOMS. 9. 5.0L (L30) + 5.7L (L31) ONLY: DIFFICULT STARTING IN EXTREME COLD (BELOW 0 DEGREES F) CONDITIONS. 10. 5.7L (L31) ONLY: POORER THAN EXPECTED FUEL ECONOMY WHEN HEAVILY LOADED. 1997 MODELS ONLY 11. MIL ON WITH DTC P0121 STORED BUT NO REPORTED DRIVEABILITY SYMPTOMS. 12. C/K + S/T MODELS WITH EITHER V-6 ENGINE AND MANUAL TRANSMISSION: AN EXHAUST BACKFIRE MAY OCCUR WHILE SHIFTING WITH MODERATE THROTTLE AT ENGINE SPEEDS ABOVE 3500 RPM. 13. EITHER V-6 ENGINE AND MANUAL TRANSMISSION: AN ENGINE FLARE BETWEEN SHIFTS MAY BE NOTED WHEN THE ENGINE IS COLD. 14. C/K, S/T AND MIL MODELS EQUIPPED WITH L35 V-6 ENGINE, AN IMPROVEMENT TO THE VAPOR CANISTER PURGE DIAGNOSTICS IS INCORPORATED INTO THE NEW CALIBRATIONS SO THAT THE TECH II CAN TURN ON CANISTER PURGE AT IDLE SPEED. CORRECTION: FOLLOW THE STRATEGY BASED DIAGNOSTIC STEPS FOR THE CUSTOMER'S REPORTED SYMPTOMS. IF DIAGNOSIS DOES NOT REVEAL A CAUSE, REFER TO THE TABLES BELOW FOR THE APPLICABLE CALIBRATION CHANGE. PERFORM PROGRAMMING PER THE LATEST TECHLINE INFORMATION FOR PROGRAMMING PROCEDURES. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > Customer Interest: > 76-65-04 > Mar > 97 > Engine Controls Driveability/Starting Issues/DTC's/MIL > Page 7319 IMPORTANT: THE CALIBRATIONS LISTED ARE FLASH CALIBRATIONS AND ARE NOT AVAILABLE FROM GMSPO. THEY ARE AVAILABLE ON 1997 TECHLINE CD DISC 5 AND LATER. WARRANTY INFORMATION: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > Customer Interest: > 76-65-04 > Mar > 97 > Engine Controls Driveability/Starting Issues/DTC's/MIL > Page 7320 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > Customer Interest: > 76-65-04 > Mar > 97 > Engine Controls Driveability/Starting Issues/DTC's/MIL > Page 7321 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > Customer Interest: > 76-65-04 > Mar > 97 > Engine Controls Driveability/Starting Issues/DTC's/MIL > Page 7322 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > Customer Interest: > 76-65-04 > Mar > 97 > Engine Controls Driveability/Starting Issues/DTC's/MIL > Page 7323 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > Customer Interest: > 76-65-04 > Mar > 97 > Engine Controls Driveability/Starting Issues/DTC's/MIL > Page 7324 FOR VEHICLES REPAIRED UNDER WARRANTY, USE THE TABLE. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > Customer Interest: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition PROM - Programmable Read Only Memory: Customer Interest PROM - MIL ON, Poor Driveability Condition File In Section: 6E - Engine Fuel & Emission Bulletin No.: 76-65-04 Date: March, 1997 Subject: Malfunction Indicator Light (MIL) On, Poor Driveability Conditions (Perform Flash Calibration) Models: 1996-97 Chevrolet and GMC Light Duty Trucks 1996-97 Chevrolet Tiltmaster and GMC Forward W4 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L Engines (VINs X, W, M, R RPOs LF6, L35, L3O, L31) Condition An owner of the above mentioned vehicles may report that the Malfunction Indicator Light (MIL) is on and/or the vehicle has one or more of the following driveability conditions. 1. 5.7L (L31) only: Surge or chuggle at speeds of 42 to 65 MPH while at steady speed or under light to moderate acceleration with the TCC applied. 2. MIL on with DTC P0172 or P0175 stored but no reported driveability symptoms. 3. MIL on with TDC P1406 stored and rough engine or poor driveability symptoms. 4. When operating at altitudes above 5,000 feet, an audible spark knock noise is heard. 5. Hesitation and/or misfire during light cruise conditions due to ignition cross-fire with no DTC stored. This will only occur on V-6 engines with cam retard offset in excess of 26° and V-8's with cam retard offset in excess of 15°. 6. The MIL may be on and a DTC stored for an engine misfire but no misfire occurred. 7. Engine exhibits an idle speed surge or roll. 1996 Models Only 8. MIL on with DTC P0102 stored but no reported driveability symptoms. 9. 5.0L (L30) & 5.7L (L31) only: Difficult starting in extreme cold (below 0° F) conditions. 10. 5.7L (L31) only: Poorer than expected fuel economy when heavily loaded. 1997 Models Only 11. MIL on with DTC P0121 stored but no reported driveability symptoms. 12. C/K & S/T Models with either V-6 engine and manual transmission: An engine flare between shifts may be noted when the engine is cold. 13. Either V-6 engine and manual transmission: An engine flare between shifts may be noted when the engine is cold. 14. C/K, S/T and M/L Models equipped with L35 V-6 engine, an improvement to the vapor canister purge diagnostics is incorporated into the new calibrations so that the Tech II can turn on canister purge at idle speed. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > Customer Interest: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7329 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > Customer Interest: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7330 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > Customer Interest: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7331 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > Customer Interest: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7332 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > Customer Interest: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7333 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > Customer Interest: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7334 Follow the Strategy Based Diagnostic Steps for the customer's reported symptoms. If diagnosis does not reveal a cause, refer to the tables below for the applicable calibration change. Perform programming per the latest Techline information for programming procedures. Important The calibrations listed are FLASH calibrations and are not available from GMSPO. They are available on 1997 Techline CD Disc 5 and later. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J-6355 Use Published Labor Operation Time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 99-06-04-053 > Nov > 99 > PROM - Powertrain Control Module Reprogramming PROM - Programmable Read Only Memory: All Technical Service Bulletins PROM - Powertrain Control Module Reprogramming File In Section: 06 - Engine/Propulsion System Bulletin No.: 99-06-04-053 Date: November, 1999 INFORMATION Subject: Powertrain Control Module (PCM) Reprogramming (Do Not Reprogram Using the Same Download Files as Those Already Present in The Control Module) Models: 1990-2000 Passenger Cars and Trucks with Reprogrammable PCM It is strongly recommended to NOT reinstall the same software and/or calibration download file(s) into the powertrain control module as those that are already present in the PCM. There is no technical reason that the download files inside the PCM would ever become corrupted after the control module had previously been successfully programmed. A P0601 (Control Module Read Only Memory) Diagnostic Trouble Code would set in memory and the MIL would be illuminated if the controller memory became corrupted. The Techline Information System 2000 (TIS 2000) PC, combined with vehicle information gained through the Tech 2, can determine when an attempt to reprogram a PCM using the same download files (as those already in the control module) is being requested. If this is attempted, the TIS 2000 PC currently displays the following message: Notice: THE CALIBRATION SELECTED IS THE CURRENT CALIBRATION IN THE CONTROL MODULE. PROGRAMMING WITH THE SAME DOWNLOAD FILES IS NOT AN EFFECTIVE REPAIR. SELECT ( YES ) TO CONTINUE PROGRAMMING THE CONTROL MODULE,OR ( NO ) TO CANCEL. Effective in the first quarter of 2000, the TIS 2000 PC will indicate: Important: THE CALIBRATION SELECTED IS ALREADY THE CURRENT CALIBRATION IN THE CONTROL MODULE. REPROGRAMMING WITH THE SAME DOWNLOAD FILE IS NOT ALLOWED. Certain learned values, such as: (but not limited to) ^ fuel trim (previously known as block learn memory), ^ IAC learned position in various park/neutral and air conditioning on/off combinations, ^ certain OBDII diagnostic thresholds, ^ automatic transmission shift adapts will revert back to their unlearned starting point values after a reprogramming event occurs. It is feasible that the engine or transmission might temporarily operate differently after a reprogramming event, until these values are re-learned. Relearning occurs while operating the vehicle through normal driving routines. If the same download files are simply reinstalled, any changes noticed in engine operation will likely disappear in a short amount of time and/or driving distance. Reprogramming the control module with the same download files that already exist in the module will only accomplish a warranty claim for a non-effective repair, and a likely comeback. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 77-71-53 > Apr > 97 > A/T - Chuggle/Surge on TCC Apply/No DTC's PROM - Programmable Read Only Memory: All Technical Service Bulletins A/T - Chuggle/Surge on TCC Apply/No DTC's File In Section: 7 - Transmission Bulletin No.: 77-71-53 Date: April, 1997 Subject: Chuggle/Surge on TCC Apply/No DTC's (Reflash PCM) Models: 1996-97 Chevrolet and GMC C/K, G Models with 5.7L Engine (VIN R - RPO L31) and HYDRA-MATIC 4L60-E Transmission (RPO M30) Condition Some owners of the above models may experience a chuggle/surge when TCC is applied under light throttle acceleration. Cause Engine inputs (Combustion events) exciting the vehicle platform/driveline or tire balance may be a contributing factor. Correction First ensure the most recent engine, not transmission calibration has been installed (Corp. # 76-65-04) and check tire balance. A new transmission calibration to correct chuggle/surge is available for use on vehicles with persistent concerns only. Important: This calibration will raise TCC engagement approximately 7-10 mph depending on application. This calibration should not be installed until the engine calibration listed above has been installed. Installation of this calibration may lead to decreased fuel economy due to TCC engagement at higher speeds. Reflash the Powertrain Control Module with the appropriate part numbers below. Refer to your Service Manual for proper procedure. Parts Information This new calibration will be available starting with the 1997 Disc 4 update. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J6355 Reflash Control Module Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 76-65-04 > Mar > 97 > Engine Controls - Driveability/Starting Issues/DTC's/MIL PROM - Programmable Read Only Memory: All Technical Service Bulletins Engine Controls Driveability/Starting Issues/DTC's/MIL MALFUNCTION INDICATOR LIGHT (MIL) ON, POOR DRIVEABILITY # 76-65-04 - (Mar 3, 1997) SUBJECT: MALFUNCTION INDICATOR LIGHT (MIL) ON, POOR DRIVEABILITY CONDITIONS (PERFORM FLASH CALIBRATION) MODELS: 1996-97 CHEVROLET AND GMC LIGHT DUTY TRUCKS 1996-97 CHEVROLET TILTMASTER AND GMC FORWARD W4 MODELS 1996-97 OLDSMOBILE BRAVADA WITH 4.3L, 5.0L, 5.7L ENGINES (VINS X, W, M, R - RPOS LF6, L35, L30, L31) CONDITION: AN OWNER MAY REPORT THAT THE MALFUNCTION INDICATOR LIGHT (MW) IS ON AND/OR THE VEHICLE HAS ONE OR MORE OF THE FOLLOWING DRIVEABILITY CONDITIONS. 1. 5.7L (L31) ONLY: SURGE OR CHUGGLE AT SPEEDS OF 42 TO 65 MPH WHILE AT STEADY SPEED OR UNDER LIGHT TO MODERATE ACCELERATION WITH THE TCC APPLIED. 2. MIL ON WITH DTC P0172 OR P0175 STORED BUT NO REPORTED DRIVEABILITY SYMPTOMS. 3. MIL ON WITH DTC P1406 STORED AND ROUGH ENGINE OR POOR DRIVEABILITY SYMPTOMS. 4. WHEN OPERATING AT ALTITUDES ABOVE 5,000 FEET, AN AUDIBLE SPARK KNOCK NOISE IS HEARD. 5. HESITATION AND/OR MISFIRE DURING LIGHT CRUISE CONDITIONS DUE TO IGNITION CROSS-FIRE WITH NO DTC STORED. THIS WILL ONLY OCCUR ON V-6 ENGINES WITH CAM RETARD OFFSET IN EXCESS OF 26 DEGREES AND V-8'S WITH CAM RETARD OFFSET IN EXCESS OF 15 DEGREES. 6. THE MIL MAY BE ON AND A DTC STORED FOR AN ENGINE MISFIRE BUT NO MISFIRE OCCURRED. 7. ENGINE EXHIBITS AN IDLE SPEED SURGE OR ROLL. 1996 MODELS ONLY 8. MIL ON WITH DTC P0102 STORED BUT NO REPORTED DRIVEABILITY SYMPTOMS. 9. 5.0L (L30) + 5.7L (L31) ONLY: DIFFICULT STARTING IN EXTREME COLD (BELOW 0 DEGREES F) CONDITIONS. 10. 5.7L (L31) ONLY: POORER THAN EXPECTED FUEL ECONOMY WHEN HEAVILY LOADED. 1997 MODELS ONLY 11. MIL ON WITH DTC P0121 STORED BUT NO REPORTED DRIVEABILITY SYMPTOMS. 12. C/K + S/T MODELS WITH EITHER V-6 ENGINE AND MANUAL TRANSMISSION: AN EXHAUST BACKFIRE MAY OCCUR WHILE SHIFTING WITH MODERATE THROTTLE AT ENGINE SPEEDS ABOVE 3500 RPM. 13. EITHER V-6 ENGINE AND MANUAL TRANSMISSION: AN ENGINE FLARE BETWEEN SHIFTS MAY BE NOTED WHEN THE ENGINE IS COLD. 14. C/K, S/T AND MIL MODELS EQUIPPED WITH L35 V-6 ENGINE, AN IMPROVEMENT TO THE VAPOR CANISTER PURGE DIAGNOSTICS IS INCORPORATED INTO THE NEW CALIBRATIONS SO THAT THE TECH II CAN TURN ON CANISTER PURGE AT IDLE SPEED. CORRECTION: FOLLOW THE STRATEGY BASED DIAGNOSTIC STEPS FOR THE CUSTOMER'S REPORTED SYMPTOMS. IF DIAGNOSIS DOES NOT REVEAL A CAUSE, REFER TO THE TABLES BELOW FOR THE APPLICABLE CALIBRATION CHANGE. PERFORM PROGRAMMING PER THE LATEST TECHLINE INFORMATION FOR PROGRAMMING PROCEDURES. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 76-65-04 > Mar > 97 > Engine Controls - Driveability/Starting Issues/DTC's/MIL > Page 7348 IMPORTANT: THE CALIBRATIONS LISTED ARE FLASH CALIBRATIONS AND ARE NOT AVAILABLE FROM GMSPO. THEY ARE AVAILABLE ON 1997 TECHLINE CD DISC 5 AND LATER. WARRANTY INFORMATION: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 76-65-04 > Mar > 97 > Engine Controls - Driveability/Starting Issues/DTC's/MIL > Page 7349 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 76-65-04 > Mar > 97 > Engine Controls - Driveability/Starting Issues/DTC's/MIL > Page 7350 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 76-65-04 > Mar > 97 > Engine Controls - Driveability/Starting Issues/DTC's/MIL > Page 7351 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 76-65-04 > Mar > 97 > Engine Controls - Driveability/Starting Issues/DTC's/MIL > Page 7352 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 76-65-04 > Mar > 97 > Engine Controls - Driveability/Starting Issues/DTC's/MIL > Page 7353 FOR VEHICLES REPAIRED UNDER WARRANTY, USE THE TABLE. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter PROM - Programmable Read Only Memory: All Technical Service Bulletins PROM - Reprogram Using Off Board Program Adapter File In Section: 6E - Engine Fuel & Emission Bulletin No.: 73-65-13 Date: March, 1997 INFORMATION Subject: Reprogramming Capability using the Off Board Programming Adapter Models: 1993-97 Passenger Cars and Trucks (Applicable Reprogrammable Vehicles) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 7358 The General Motors vehicles contain Electronically Reprogrammable Devices (i.e. PCM, VCM, ECM). These vehicles cannot be programmed through PROM replacement, however service programming capability is available through the Tech 1/1A, Tech 2 and Techline terminals via direct or remote programming. The Environmental Protection Agency (EPA) has requested that all new vehicle manufacturers ensure their dealers/retailers are aware that they are responsible for providing customers access to reprogramming services at a reasonable cost and in a timely manner. Although programming of controllers has become a common service practice at GM dealers/retailers, the EPA has received reports from consumers and the aftermarket repair industry that they were unable to purchase a new (programmed) Electronically Reprogrammable Device (ERD) over-the-counter. As a result, on August 1, 1995, the Federal Government issued a regulation requiring all manufacturers to make available reprogramming to the independent aftermarket by December 1, 1997. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 7359 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 7360 Today, the Off Board Programming Adapter (OBPA) is used to reprogram ERD's sold over-the-counter. For all practical purposes, the OBPA takes the place of the vehicle when the vehicle is not available. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 7361 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 7362 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 7363 The list of dealerships/retailers currently own the OBPA (see Attachments 1 - 3). These locations are equipped to provide over-the-counter preprogrammed ERD's. The hardware required to perform reprogramming in addition to the OBPA is a Techline terminal, Tech 1/1A and associated cables and adapters. THE TECH 2 SHOULD NOT BE USED WITH THE OBPA AT THIS TIME BECAUSE OF INADEQUATE OBPA GROUNDING. The current OBPA can support reprogramming on all late model General Motor's vehicles except: ^ Premium V-8's ^ 1996 Diesel Truck ^ Cadillac Catera Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 7364 ^ All 1997 programmable vehicles (requires use of the Tech 2) A modification to the OBPA is being offered by Kent-Moore to support these additional vehicles and to allow reprogramming using the Tech 2. The revisions to the OBPA for the Tech 2 is very important as the Tech 2 is the only tool used for service programming for 1997 and future vehicles. To have the modifications performed, contact Kent-Moore at (800) 345-2233. The revisions (part number J 41207 REV-C) are free of charge for GM dealerships/retailers. A dealership/retailer can purchase the OBPA by contacting Kent-Moore (part number J 41207-C). Support on how to use the OBPA is provided by the Techline Customer Support Center (TCSC) at (800) 828-6860 (English) or (800) 503-3222 (French). If you need to purchase an OBPA and/or cable, contact Kent-Moore at (800) 345-2233. The OBPA retails for $695.00 (includes all revisions 1-4) under part number J 41207-C. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition PROM - Programmable Read Only Memory: All Technical Service Bulletins PROM - MIL ON, Poor Driveability Condition File In Section: 6E - Engine Fuel & Emission Bulletin No.: 76-65-04 Date: March, 1997 Subject: Malfunction Indicator Light (MIL) On, Poor Driveability Conditions (Perform Flash Calibration) Models: 1996-97 Chevrolet and GMC Light Duty Trucks 1996-97 Chevrolet Tiltmaster and GMC Forward W4 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L Engines (VINs X, W, M, R RPOs LF6, L35, L3O, L31) Condition An owner of the above mentioned vehicles may report that the Malfunction Indicator Light (MIL) is on and/or the vehicle has one or more of the following driveability conditions. 1. 5.7L (L31) only: Surge or chuggle at speeds of 42 to 65 MPH while at steady speed or under light to moderate acceleration with the TCC applied. 2. MIL on with DTC P0172 or P0175 stored but no reported driveability symptoms. 3. MIL on with TDC P1406 stored and rough engine or poor driveability symptoms. 4. When operating at altitudes above 5,000 feet, an audible spark knock noise is heard. 5. Hesitation and/or misfire during light cruise conditions due to ignition cross-fire with no DTC stored. This will only occur on V-6 engines with cam retard offset in excess of 26° and V-8's with cam retard offset in excess of 15°. 6. The MIL may be on and a DTC stored for an engine misfire but no misfire occurred. 7. Engine exhibits an idle speed surge or roll. 1996 Models Only 8. MIL on with DTC P0102 stored but no reported driveability symptoms. 9. 5.0L (L30) & 5.7L (L31) only: Difficult starting in extreme cold (below 0° F) conditions. 10. 5.7L (L31) only: Poorer than expected fuel economy when heavily loaded. 1997 Models Only 11. MIL on with DTC P0121 stored but no reported driveability symptoms. 12. C/K & S/T Models with either V-6 engine and manual transmission: An engine flare between shifts may be noted when the engine is cold. 13. Either V-6 engine and manual transmission: An engine flare between shifts may be noted when the engine is cold. 14. C/K, S/T and M/L Models equipped with L35 V-6 engine, an improvement to the vapor canister purge diagnostics is incorporated into the new calibrations so that the Tech II can turn on canister purge at idle speed. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7369 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7370 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7371 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7372 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7373 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7374 Follow the Strategy Based Diagnostic Steps for the customer's reported symptoms. If diagnosis does not reveal a cause, refer to the tables below for the applicable calibration change. Perform programming per the latest Techline information for programming procedures. Important The calibrations listed are FLASH calibrations and are not available from GMSPO. They are available on 1997 Techline CD Disc 5 and later. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J-6355 Use Published Labor Operation Time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 536508 > Jan > 96 > SPS/FLASH EPROM - Programming PROM - Programmable Read Only Memory: All Technical Service Bulletins SPS/FLASH EPROM Programming File In Section: 6E - Engine Fuel & Emission Bulletin No.: 53-65-08 Date: January, 1996 INFORMATION Subject: SPS/FLASH EPROM Programming Models: 1993-96 Passenger Cars and Trucks Applicable Reprogrammable Vehicles This bulletin is being issued to assist technicians in reprogramming vehicles and should be used in conjunction with instructions provided on your Techline Terminal and in your Techline Terminal User's Manual. THE TECHLINE TERMINAL (T-20, T-50, T-60) HAS BEEN ABLE TO DO 1996 VEHICLE PROGRAMMING THROUGH THE DIRECT METHOD SINCE 1996 VEHICLES HAVE BEEN AVAILABLE IN THE DEALERSHIPS/RETAIL FACILITIES. THE TECHLINE CD-ROM TITLED DISC 13 CONTAINS THE SOFTWARE NEEDED TO PROGRAM ALL 1996 VEHICLES WITH A TECH 1 (REMOTE PROGRAMMING METHOD). SPS Tips 1. BATTERY VOLTAGE SHOULD BE CHECKED. A FULLY CHARGED BATTERY IS NECESSARY BEFORE REPROGRAMMING TAKES PLACE. THE VEHICLE BATTERY SHOULD NOT BE CONNECTED TO A BATTERY CHARGER DURING A PROGRAMMING EVENT INCORRECT VOLTAGE COULD CAUSE PROGRAMMING AND/OR CONTROL MODULE FAILURE. During programming, the control module depends on the battery as its sole source of power. Also during programming, the vehicle's components (i.e. blower motor) are set to a default mode which may be turned on, placing additional draw on the vehicle's battery. If the voltage goes outside the specified range (11 to 14 volts) the controllers and the Techline equipment will stop communicating. If this happens, it could cause the control module to become inoperable and require replacement. 2. CHECK THE INTEGRITY OF THE TECH 1 CABLES, MAKE SURE THEY ARE NOT FRAYED, BROKEN OR TWISTED. Loss of communication for any reason will require additional time in completing the reprogramming event. 3. IF USING A TECH 1, YOUR MASS STORAGE CARTRIDGE (MSC) MUST BE UPDATED TO REFLECT THE MOST CURRENT UPDATE OFFERED ON THE TECHLINE CD-ROM. DISC 13, 1995 WAS THE FIRST CD-ROM THAT HAD REMOTE PROGRAMMING SUPPORT If your MSC is not updated to reflect the current software version on the Techline Terminal, in some situations the software will not be capable of interpreting the information that is requested from the vehicle. 4. T-100 TERMINALS (CAMS) ARE NOT CAPABLE OF PROGRAMMING OBD II VEHICLES THROUGH THE DIRECT METHOD. A TECH 1 MUST BE USED (REMOTE METHOD) WHEN REPROGRAMMING WITH A T-100. The T-100 terminals communicate with vehicles through a DLC (ALDL) card and cable found within the T-100's computer. The DLC (ALDL) card is not capable of communicating at the new baud rate used with OBD II. 5. PROGRAMMING IS NOT NEEDED IF THE CURRENT CALIBRATION IS THE SAME AS THE SELECTED CALIBRATION. 6. IF PROGRAMMING A NEW CONTROL MODULE, YOU MUST REQUEST INFORMATION FROM THE NEW CONTROL MODULE. The security information that is needed for a control module to be programmed is stored in the new control module. The security information must be requested from the control module to be programmed. At that point, the control module can be successfully programmed. This requesting of security information takes place in both the direct and remote methods. The request is automatic when using the direct method. Looking at the calibration stored in the old controller may be helpful in selecting the calibration from the CD-ROM for the new controller. 7. WHEN PROGRAMMING OBD II VEHICLES WITH A TECH 1 (REMOTE PROGRAMMING METHOD), A VEHICLE INTERFACE MODULE (VIM) IS REQUIRED. The VIM allows the Tech 1 to communicate with the OBD II vehicles. The VIM is necessary for all other Tech 1 diagnostics on OBD II vehicles. VIMs are no longer on backorder. If you are interested in obtaining additional VIMs, call 1-800-GM-TOOLS and ask for VIM kit part number 7000041. 8. DISCONNECT THE TECH I AND VIM FROM THE VEHICLE BETWEEN RETRIEVING DATA AND PROGRAMMING THE VEHICLE. If the VIM remains powered up after data is requested, a communication problem may result when the reprogramming function is performed. 9. WHEN CONNECTING THE TECH 1 TO A TECHLINE TERMINAL (EXCEPT T-100 CAMS), ALWAYS CONNECT THE FLAT GRAY R5232 CABLE FIRST AND THEN THE POWER ADAPTER. FAILURE TO DO SO COULD RESULT IN A LOSS OF INFORMATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 536508 > Jan > 96 > SPS/FLASH EPROM - Programming > Page 7379 STORED ON THE TECH 1. When power is turned on to the Tech 1, it looks for the RS232 connection. If it does not see the connection, the Tech 1 in some cases, will erase the information stored for download. 10. DO NOT DISCONTINUE OR INTERRUPT THE PROGRAM LOADING PROCESS TO THE VEHICLE. This will result in a programming error and could prevent the Electronic Control Module (ECM) from functioning properly. 11. AFTER PROGRAMMING IS COMPLETE, PRESS "EXIT". MAKE SURE THE KEY IS CYCLED OFF FOR APPROXIMATELY 10 SECONDS THEN BACK ON. Some vehicles will lose component settings (PMC/IAC Valve). Cycling the key off two times (Off for 30 seconds, On for 10 then repeat a second time) will allow for resetting of the components. Start the vehicle to ensure programming was successful. FOR CADILLAC VEHICLES ONLY a. DUE TO OTHER MODULES ON THE DATA LINE TRYING TO COMMUNICATE WITH THE ECM DURING PROGRAMMING, SOME COMMUNICATION CODES MAY BE SET After programming is complete, clear any codes and verify they do not reset. b. TO HELP MINIMIZE BATTERY DRAW DURING ECM PROGRAMMING, DISCONNECT THE BLOWER MOTOR (AT THE CONNECTOR, NOT THE FUSE) PRIOR TO PROGRAMMING. When programming is complete, reconnect the blower motor. 12. 1997 VEHICLES REQUIRE REPROGRAMMING BE DONE USING A TECH 2. OBD II vehicle calibration size and complexity will require more memory than the Tech 1 has available. Tech 2 will be an essential tool in the first quarter of 1996 containing limited 1996 applications and updates. 13. STG HAS ISSUED BULLETINS (# 53-65-04 and # 53-65-05 - (SEE CHART EXCERPTED FROM 53-65-05 FOR USE AS A QUICK REFERENCE GUIDE), DEVELOPED QUICK REFERENCE GUIDES (P/N SPSCARD-1 AVAILABLE THROUGH YOUR LOCAL GM TRAINING CENTER), PRODUCED CPT VIDEOS (CPT # 56010.00-B), HAD PULSAT BROADCASTS, AND OFFERS GM TRAINING CENTER CLASSROOM COURSES. As you work through reprogramming, keep the above-mentioned material in mind as resources to assist you if difficulty is encountered. As always, the Techline Customer Support Center (1-800-828-6860 English, 1-800-503-3222 French) is always available to assist the technician with any situation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 536508 > Jan > 96 > SPS/FLASH EPROM - Programming > Page 7380 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 536508 > Jan > 96 > SPS/FLASH EPROM - Programming > Page 7381 SPS/EEPROM Programming 1993 to current Reprogrammable Vehicles Note: If programming a new control module you must request info from the new control module first. Battery voltage should be checked and at full charge before reprogramming takes place. System to be programmed should NOT be connected to a battery charger. Incorrect voltage could cause programming and/or control module failure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 536505 > Oct > 95 > SPS/EEPROM - Programming Chart PROM - Programmable Read Only Memory: All Technical Service Bulletins SPS/EEPROM Programming Chart File In Section: 6E - Engine Fuel & Emission Bulletin No.: 53-65-05 Date: October, 1995 Subject: Chart to Assist Technician with SPS/EEPROM Programming Models: 1995-96 Passenger Cars and Trucks This bulletin is being issued to assist technicians with the reprogramming of vehicles. The following chart was developed to be used by technicians that are familiar with the Techline terminals, Tech 1 and all of its adapters: IMPORTANT If programming a new control module, you must request information from the new control module first. Battery voltage must be between 11 and 14 volts. System to be programmed should NOT be connected to a battery charger. Incorrect voltage could cause programming and/or control module failure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 536505 > Oct > 95 > SPS/EEPROM - Programming Chart > Page 7386 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Technical Service Bulletins for PROM - Programmable Read Only Memory: > 536505 > Oct > 95 > SPS/EEPROM - Programming Chart > Page 7387 Programming Chart Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Other Service Bulletins for PROM - Programmable Read Only Memory: > 99-06-04-053 > Nov > 99 > PROM - Powertrain Control Module Reprogramming PROM - Programmable Read Only Memory: All Technical Service Bulletins PROM - Powertrain Control Module Reprogramming File In Section: 06 - Engine/Propulsion System Bulletin No.: 99-06-04-053 Date: November, 1999 INFORMATION Subject: Powertrain Control Module (PCM) Reprogramming (Do Not Reprogram Using the Same Download Files as Those Already Present in The Control Module) Models: 1990-2000 Passenger Cars and Trucks with Reprogrammable PCM It is strongly recommended to NOT reinstall the same software and/or calibration download file(s) into the powertrain control module as those that are already present in the PCM. There is no technical reason that the download files inside the PCM would ever become corrupted after the control module had previously been successfully programmed. A P0601 (Control Module Read Only Memory) Diagnostic Trouble Code would set in memory and the MIL would be illuminated if the controller memory became corrupted. The Techline Information System 2000 (TIS 2000) PC, combined with vehicle information gained through the Tech 2, can determine when an attempt to reprogram a PCM using the same download files (as those already in the control module) is being requested. If this is attempted, the TIS 2000 PC currently displays the following message: Notice: THE CALIBRATION SELECTED IS THE CURRENT CALIBRATION IN THE CONTROL MODULE. PROGRAMMING WITH THE SAME DOWNLOAD FILES IS NOT AN EFFECTIVE REPAIR. SELECT ( YES ) TO CONTINUE PROGRAMMING THE CONTROL MODULE,OR ( NO ) TO CANCEL. Effective in the first quarter of 2000, the TIS 2000 PC will indicate: Important: THE CALIBRATION SELECTED IS ALREADY THE CURRENT CALIBRATION IN THE CONTROL MODULE. REPROGRAMMING WITH THE SAME DOWNLOAD FILE IS NOT ALLOWED. Certain learned values, such as: (but not limited to) ^ fuel trim (previously known as block learn memory), ^ IAC learned position in various park/neutral and air conditioning on/off combinations, ^ certain OBDII diagnostic thresholds, ^ automatic transmission shift adapts will revert back to their unlearned starting point values after a reprogramming event occurs. It is feasible that the engine or transmission might temporarily operate differently after a reprogramming event, until these values are re-learned. Relearning occurs while operating the vehicle through normal driving routines. If the same download files are simply reinstalled, any changes noticed in engine operation will likely disappear in a short amount of time and/or driving distance. Reprogramming the control module with the same download files that already exist in the module will only accomplish a warranty claim for a non-effective repair, and a likely comeback. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Other Service Bulletins for PROM - Programmable Read Only Memory: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter PROM - Programmable Read Only Memory: All Technical Service Bulletins PROM - Reprogram Using Off Board Program Adapter File In Section: 6E - Engine Fuel & Emission Bulletin No.: 73-65-13 Date: March, 1997 INFORMATION Subject: Reprogramming Capability using the Off Board Programming Adapter Models: 1993-97 Passenger Cars and Trucks (Applicable Reprogrammable Vehicles) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Other Service Bulletins for PROM - Programmable Read Only Memory: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 7397 The General Motors vehicles contain Electronically Reprogrammable Devices (i.e. PCM, VCM, ECM). These vehicles cannot be programmed through PROM replacement, however service programming capability is available through the Tech 1/1A, Tech 2 and Techline terminals via direct or remote programming. The Environmental Protection Agency (EPA) has requested that all new vehicle manufacturers ensure their dealers/retailers are aware that they are responsible for providing customers access to reprogramming services at a reasonable cost and in a timely manner. Although programming of controllers has become a common service practice at GM dealers/retailers, the EPA has received reports from consumers and the aftermarket repair industry that they were unable to purchase a new (programmed) Electronically Reprogrammable Device (ERD) over-the-counter. As a result, on August 1, 1995, the Federal Government issued a regulation requiring all manufacturers to make available reprogramming to the independent aftermarket by December 1, 1997. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Other Service Bulletins for PROM - Programmable Read Only Memory: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 7398 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Other Service Bulletins for PROM - Programmable Read Only Memory: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 7399 Today, the Off Board Programming Adapter (OBPA) is used to reprogram ERD's sold over-the-counter. For all practical purposes, the OBPA takes the place of the vehicle when the vehicle is not available. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Other Service Bulletins for PROM - Programmable Read Only Memory: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 7400 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Other Service Bulletins for PROM - Programmable Read Only Memory: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 7401 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Other Service Bulletins for PROM - Programmable Read Only Memory: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 7402 The list of dealerships/retailers currently own the OBPA (see Attachments 1 - 3). These locations are equipped to provide over-the-counter preprogrammed ERD's. The hardware required to perform reprogramming in addition to the OBPA is a Techline terminal, Tech 1/1A and associated cables and adapters. THE TECH 2 SHOULD NOT BE USED WITH THE OBPA AT THIS TIME BECAUSE OF INADEQUATE OBPA GROUNDING. The current OBPA can support reprogramming on all late model General Motor's vehicles except: ^ Premium V-8's ^ 1996 Diesel Truck ^ Cadillac Catera Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Other Service Bulletins for PROM - Programmable Read Only Memory: > 736513 > Mar > 97 > PROM - Reprogram Using Off Board Program Adapter > Page 7403 ^ All 1997 programmable vehicles (requires use of the Tech 2) A modification to the OBPA is being offered by Kent-Moore to support these additional vehicles and to allow reprogramming using the Tech 2. The revisions to the OBPA for the Tech 2 is very important as the Tech 2 is the only tool used for service programming for 1997 and future vehicles. To have the modifications performed, contact Kent-Moore at (800) 345-2233. The revisions (part number J 41207 REV-C) are free of charge for GM dealerships/retailers. A dealership/retailer can purchase the OBPA by contacting Kent-Moore (part number J 41207-C). Support on how to use the OBPA is provided by the Techline Customer Support Center (TCSC) at (800) 828-6860 (English) or (800) 503-3222 (French). If you need to purchase an OBPA and/or cable, contact Kent-Moore at (800) 345-2233. The OBPA retails for $695.00 (includes all revisions 1-4) under part number J 41207-C. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Other Service Bulletins for PROM - Programmable Read Only Memory: > 536508 > Jan > 96 > SPS/FLASH EPROM - Programming PROM - Programmable Read Only Memory: All Technical Service Bulletins SPS/FLASH EPROM Programming File In Section: 6E - Engine Fuel & Emission Bulletin No.: 53-65-08 Date: January, 1996 INFORMATION Subject: SPS/FLASH EPROM Programming Models: 1993-96 Passenger Cars and Trucks Applicable Reprogrammable Vehicles This bulletin is being issued to assist technicians in reprogramming vehicles and should be used in conjunction with instructions provided on your Techline Terminal and in your Techline Terminal User's Manual. THE TECHLINE TERMINAL (T-20, T-50, T-60) HAS BEEN ABLE TO DO 1996 VEHICLE PROGRAMMING THROUGH THE DIRECT METHOD SINCE 1996 VEHICLES HAVE BEEN AVAILABLE IN THE DEALERSHIPS/RETAIL FACILITIES. THE TECHLINE CD-ROM TITLED DISC 13 CONTAINS THE SOFTWARE NEEDED TO PROGRAM ALL 1996 VEHICLES WITH A TECH 1 (REMOTE PROGRAMMING METHOD). SPS Tips 1. BATTERY VOLTAGE SHOULD BE CHECKED. A FULLY CHARGED BATTERY IS NECESSARY BEFORE REPROGRAMMING TAKES PLACE. THE VEHICLE BATTERY SHOULD NOT BE CONNECTED TO A BATTERY CHARGER DURING A PROGRAMMING EVENT INCORRECT VOLTAGE COULD CAUSE PROGRAMMING AND/OR CONTROL MODULE FAILURE. During programming, the control module depends on the battery as its sole source of power. Also during programming, the vehicle's components (i.e. blower motor) are set to a default mode which may be turned on, placing additional draw on the vehicle's battery. If the voltage goes outside the specified range (11 to 14 volts) the controllers and the Techline equipment will stop communicating. If this happens, it could cause the control module to become inoperable and require replacement. 2. CHECK THE INTEGRITY OF THE TECH 1 CABLES, MAKE SURE THEY ARE NOT FRAYED, BROKEN OR TWISTED. Loss of communication for any reason will require additional time in completing the reprogramming event. 3. IF USING A TECH 1, YOUR MASS STORAGE CARTRIDGE (MSC) MUST BE UPDATED TO REFLECT THE MOST CURRENT UPDATE OFFERED ON THE TECHLINE CD-ROM. DISC 13, 1995 WAS THE FIRST CD-ROM THAT HAD REMOTE PROGRAMMING SUPPORT If your MSC is not updated to reflect the current software version on the Techline Terminal, in some situations the software will not be capable of interpreting the information that is requested from the vehicle. 4. T-100 TERMINALS (CAMS) ARE NOT CAPABLE OF PROGRAMMING OBD II VEHICLES THROUGH THE DIRECT METHOD. A TECH 1 MUST BE USED (REMOTE METHOD) WHEN REPROGRAMMING WITH A T-100. The T-100 terminals communicate with vehicles through a DLC (ALDL) card and cable found within the T-100's computer. The DLC (ALDL) card is not capable of communicating at the new baud rate used with OBD II. 5. PROGRAMMING IS NOT NEEDED IF THE CURRENT CALIBRATION IS THE SAME AS THE SELECTED CALIBRATION. 6. IF PROGRAMMING A NEW CONTROL MODULE, YOU MUST REQUEST INFORMATION FROM THE NEW CONTROL MODULE. The security information that is needed for a control module to be programmed is stored in the new control module. The security information must be requested from the control module to be programmed. At that point, the control module can be successfully programmed. This requesting of security information takes place in both the direct and remote methods. The request is automatic when using the direct method. Looking at the calibration stored in the old controller may be helpful in selecting the calibration from the CD-ROM for the new controller. 7. WHEN PROGRAMMING OBD II VEHICLES WITH A TECH 1 (REMOTE PROGRAMMING METHOD), A VEHICLE INTERFACE MODULE (VIM) IS REQUIRED. The VIM allows the Tech 1 to communicate with the OBD II vehicles. The VIM is necessary for all other Tech 1 diagnostics on OBD II vehicles. VIMs are no longer on backorder. If you are interested in obtaining additional VIMs, call 1-800-GM-TOOLS and ask for VIM kit part number 7000041. 8. DISCONNECT THE TECH I AND VIM FROM THE VEHICLE BETWEEN RETRIEVING DATA AND PROGRAMMING THE VEHICLE. If the VIM remains powered up after data is requested, a communication problem may result when the reprogramming function is performed. 9. WHEN CONNECTING THE TECH 1 TO A TECHLINE TERMINAL (EXCEPT T-100 CAMS), ALWAYS CONNECT THE FLAT GRAY R5232 CABLE FIRST AND THEN THE POWER ADAPTER. FAILURE TO DO SO COULD RESULT IN A LOSS OF INFORMATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Other Service Bulletins for PROM - Programmable Read Only Memory: > 536508 > Jan > 96 > SPS/FLASH EPROM - Programming > Page 7408 STORED ON THE TECH 1. When power is turned on to the Tech 1, it looks for the RS232 connection. If it does not see the connection, the Tech 1 in some cases, will erase the information stored for download. 10. DO NOT DISCONTINUE OR INTERRUPT THE PROGRAM LOADING PROCESS TO THE VEHICLE. This will result in a programming error and could prevent the Electronic Control Module (ECM) from functioning properly. 11. AFTER PROGRAMMING IS COMPLETE, PRESS "EXIT". MAKE SURE THE KEY IS CYCLED OFF FOR APPROXIMATELY 10 SECONDS THEN BACK ON. Some vehicles will lose component settings (PMC/IAC Valve). Cycling the key off two times (Off for 30 seconds, On for 10 then repeat a second time) will allow for resetting of the components. Start the vehicle to ensure programming was successful. FOR CADILLAC VEHICLES ONLY a. DUE TO OTHER MODULES ON THE DATA LINE TRYING TO COMMUNICATE WITH THE ECM DURING PROGRAMMING, SOME COMMUNICATION CODES MAY BE SET After programming is complete, clear any codes and verify they do not reset. b. TO HELP MINIMIZE BATTERY DRAW DURING ECM PROGRAMMING, DISCONNECT THE BLOWER MOTOR (AT THE CONNECTOR, NOT THE FUSE) PRIOR TO PROGRAMMING. When programming is complete, reconnect the blower motor. 12. 1997 VEHICLES REQUIRE REPROGRAMMING BE DONE USING A TECH 2. OBD II vehicle calibration size and complexity will require more memory than the Tech 1 has available. Tech 2 will be an essential tool in the first quarter of 1996 containing limited 1996 applications and updates. 13. STG HAS ISSUED BULLETINS (# 53-65-04 and # 53-65-05 - (SEE CHART EXCERPTED FROM 53-65-05 FOR USE AS A QUICK REFERENCE GUIDE), DEVELOPED QUICK REFERENCE GUIDES (P/N SPSCARD-1 AVAILABLE THROUGH YOUR LOCAL GM TRAINING CENTER), PRODUCED CPT VIDEOS (CPT # 56010.00-B), HAD PULSAT BROADCASTS, AND OFFERS GM TRAINING CENTER CLASSROOM COURSES. As you work through reprogramming, keep the above-mentioned material in mind as resources to assist you if difficulty is encountered. As always, the Techline Customer Support Center (1-800-828-6860 English, 1-800-503-3222 French) is always available to assist the technician with any situation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Other Service Bulletins for PROM - Programmable Read Only Memory: > 536508 > Jan > 96 > SPS/FLASH EPROM - Programming > Page 7409 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Other Service Bulletins for PROM - Programmable Read Only Memory: > 536508 > Jan > 96 > SPS/FLASH EPROM - Programming > Page 7410 SPS/EEPROM Programming 1993 to current Reprogrammable Vehicles Note: If programming a new control module you must request info from the new control module first. Battery voltage should be checked and at full charge before reprogramming takes place. System to be programmed should NOT be connected to a battery charger. Incorrect voltage could cause programming and/or control module failure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Other Service Bulletins for PROM - Programmable Read Only Memory: > 536505 > Oct > 95 > SPS/EEPROM - Programming Chart PROM - Programmable Read Only Memory: All Technical Service Bulletins SPS/EEPROM Programming Chart File In Section: 6E - Engine Fuel & Emission Bulletin No.: 53-65-05 Date: October, 1995 Subject: Chart to Assist Technician with SPS/EEPROM Programming Models: 1995-96 Passenger Cars and Trucks This bulletin is being issued to assist technicians with the reprogramming of vehicles. The following chart was developed to be used by technicians that are familiar with the Techline terminals, Tech 1 and all of its adapters: IMPORTANT If programming a new control module, you must request information from the new control module first. Battery voltage must be between 11 and 14 volts. System to be programmed should NOT be connected to a battery charger. Incorrect voltage could cause programming and/or control module failure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Other Service Bulletins for PROM - Programmable Read Only Memory: > 536505 > Oct > 95 > SPS/EEPROM - Programming Chart > Page 7415 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Powertrain Management > PROM - Programmable Read Only Memory > Component Information > Technical Service Bulletins > All Other Service Bulletins for PROM - Programmable Read Only Memory: > 536505 > Oct > 95 > SPS/EEPROM - Programming Chart > Page 7416 Programming Chart Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Interlock Solenoid > Component Information > Locations Shift Interlock Solenoid: Locations RH side of steering column, under Support bracket. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling Shift Solenoid: Customer Interest A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling File In Section: 7 Transmission Bulletin No.: 77-71-77 Date: December, 1997 Subject: Loss of 4th Gear, Slipping in 4th Gear, Busy 3-4 Shifting or TCC Cycling (Replace Shift Solenoids) Models: 1996-97 Chevrolet and GMC C/K, G, P Models with HYDRA-MATIC 4L8OE Transmission (RPO MT1) Condition Some owners may comment about a loss of 4th gear, slipping in 4th gear, busy 3-4 shifting or Torque Converter Clutch (TCC) cycling and no DTC's are setting. Cause Shift solenoid leaking hydraulically. Correction If normal diagnosis does not provide a correction, follow the solenoid test procedure listed. Replace the shift solenoid if it fails the test. Also verify that the transmission cooling system is operating properly. Service Information (figure 1) Starting June 23, 1997 (Julian date 174) all HYDRA-MATIC 4L80-E transmissions are being built with the new solenoid assemblies. The new solenoids will service all 1991 through 1997 4L80-E applications. The above listed conditions occur mainly on high duty cycle applications and/or when the transmission is operated under high temperature conditions. Each solenoid may be tested for leaking using the following test: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling > Page 7431 1. Remove the solenoid from the control valve body. Refer to the Service Manual for the proper procedure. 2. Clamp a piece of 1/2 inch I.D. rubber hose over the fluid inlet end of the solenoid. 3. Connect a wire from one of the solenoid terminals to the negative terminal (ground) of a battery. 4. Apply compressed air to the rubber hose. Do not use air pressure in excess of 120 psi. Excessive pressure will not allow the check ball to seat properly. 5. Connect a wire from the other solenoid to the positive terminal (12 volts) of the battery. 6. Observe the air flow through the solenoid. Replace the solenoid if there is an air leak when the solenoid is energized. Parts Information New Part Number Description 10478140 1-2 & 3-4 Shift Solenoid (black) 10478141 2-3 Shift Solenoid (white) Parts are currently available through GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift Shift Solenoid: Customer Interest A/T - Engine Speed Flare During Part Throttle Downshift File In Section: 7 - Transmission Bulletin No.: 67-71-47 Date: July, 1996 Subject: 3-2 Part Throttle Downshift Flare (Replace 3-2 Solenoid) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1996 Chevrolet Camaro, Caprice, Corvette 1996 Pontiac Firebird 1996 Chevrolet and GMC C/K, M/L, S/T, G Models 1996 Oldsmobile Bravada with HYDRA-MATIC 4L60-E (RPO M30) Condition (Figures 1 and 2) Some owners of the above models with a HYDRA-MATIC 4L60-E transmission (built before May 24, 1996/Julian Date 6145) may experience an engine speed flare of 1000-2000 RPM, during a part throttle downshift at 19-31 mph. This condition will not set any DTC's (Diagnostic Trouble Codes). Cause Exhaust seat on the 3-2 control solenoid backing out. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift > Page 7436 Correction (Figure 3) Replace the 3-2 control solenoid. Julian Date on the solenoid will be May 13, 1996 (6134) or later. Parts Information New Part Number Description 24209121 Solenoid, 3-2 Control Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time K6559 Replace 3-2 Use published labor Control Solenoid operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling Shift Solenoid: All Technical Service Bulletins A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling File In Section: 7 Transmission Bulletin No.: 77-71-77 Date: December, 1997 Subject: Loss of 4th Gear, Slipping in 4th Gear, Busy 3-4 Shifting or TCC Cycling (Replace Shift Solenoids) Models: 1996-97 Chevrolet and GMC C/K, G, P Models with HYDRA-MATIC 4L8OE Transmission (RPO MT1) Condition Some owners may comment about a loss of 4th gear, slipping in 4th gear, busy 3-4 shifting or Torque Converter Clutch (TCC) cycling and no DTC's are setting. Cause Shift solenoid leaking hydraulically. Correction If normal diagnosis does not provide a correction, follow the solenoid test procedure listed. Replace the shift solenoid if it fails the test. Also verify that the transmission cooling system is operating properly. Service Information (figure 1) Starting June 23, 1997 (Julian date 174) all HYDRA-MATIC 4L80-E transmissions are being built with the new solenoid assemblies. The new solenoids will service all 1991 through 1997 4L80-E applications. The above listed conditions occur mainly on high duty cycle applications and/or when the transmission is operated under high temperature conditions. Each solenoid may be tested for leaking using the following test: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling > Page 7442 1. Remove the solenoid from the control valve body. Refer to the Service Manual for the proper procedure. 2. Clamp a piece of 1/2 inch I.D. rubber hose over the fluid inlet end of the solenoid. 3. Connect a wire from one of the solenoid terminals to the negative terminal (ground) of a battery. 4. Apply compressed air to the rubber hose. Do not use air pressure in excess of 120 psi. Excessive pressure will not allow the check ball to seat properly. 5. Connect a wire from the other solenoid to the positive terminal (12 volts) of the battery. 6. Observe the air flow through the solenoid. Replace the solenoid if there is an air leak when the solenoid is energized. Parts Information New Part Number Description 10478140 1-2 & 3-4 Shift Solenoid (black) 10478141 2-3 Shift Solenoid (white) Parts are currently available through GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 377148A > Nov > 96 > A/T - Shift Solenoid Update Shift Solenoid: All Technical Service Bulletins A/T - Shift Solenoid Update File In Section: 7 Transmission Bulletin No.: 37-71-48A Date: November, 1996 INFORMATION Subject: Transmission Product Updates (New Shift Solenoids) Models: 1991-97 Chevrolet and GMC C/K, P, G Models 1991 Chevrolet and GMC R/V Models with HYDRA-MATIC 4L8O-E Transmission (RPO MT1) This bulletin is being revised to update the part numbers and to include 1995-97 model years. Please discard Corporate Bulletin Number 377148 (Section 7 - Transmission). Service Information Starting August 14, 1996 (Julian date 226) all HYDRA-MATIC 4L80-E transmissions are being built with the new solenoid assemblies. The new solenoids are serviced for all 1991 through 1997 4L80-E applications. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 377148A > Nov > 96 > A/T - Shift Solenoid Update > Page 7447 Parts Information Previous Part New Part Description 10478125 10478132 Valve assembly, 1-2 Shift Solenoid (Black) 10478126 10478133 Valve assembly, 2-3 Shift Solenoid (White) Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift Shift Solenoid: All Technical Service Bulletins A/T - Engine Speed Flare During Part Throttle Downshift File In Section: 7 - Transmission Bulletin No.: 67-71-47 Date: July, 1996 Subject: 3-2 Part Throttle Downshift Flare (Replace 3-2 Solenoid) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1996 Chevrolet Camaro, Caprice, Corvette 1996 Pontiac Firebird 1996 Chevrolet and GMC C/K, M/L, S/T, G Models 1996 Oldsmobile Bravada with HYDRA-MATIC 4L60-E (RPO M30) Condition (Figures 1 and 2) Some owners of the above models with a HYDRA-MATIC 4L60-E transmission (built before May 24, 1996/Julian Date 6145) may experience an engine speed flare of 1000-2000 RPM, during a part throttle downshift at 19-31 mph. This condition will not set any DTC's (Diagnostic Trouble Codes). Cause Exhaust seat on the 3-2 control solenoid backing out. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift > Page 7452 Correction (Figure 3) Replace the 3-2 control solenoid. Julian Date on the solenoid will be May 13, 1996 (6134) or later. Parts Information New Part Number Description 24209121 Solenoid, 3-2 Control Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time K6559 Replace 3-2 Use published labor Control Solenoid operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Shift Solenoid: > NHTSA97V096000 > Jun > 97 > Recall 97V096000: Outboard Seat Belt Replacement Seat Belt: All Technical Service Bulletins Recall 97V096000: Outboard Seat Belt Replacement Vehicle Description: Extended cab pickup trucks equipped with 60/40 front bench seats and extended cab pickup trucks and 2-door utility vehicles equipped with manual locking recliner bucket seats. The outboard safety belt webbing on the driver's and/or passenger's seat can separate during a frontal impact. If a separation occurred and there were secondary crash events or vehicle rollover, there would be no belt restraint of the occupant and increased injuries could occur. Dealers will replace these safety belts. Owner Notification: Owner notification will begin during September 1997. Owners who take their vehicles to an authorized dealer on an agreed upon service date and do not receive the free remedy within a reasonable time should contact Chevrolet at 1-800-222-1020 or GMC at 1-800-462-8782. Also contact the National Highway Traffic Safety Administration's Auto Safety Hotline at 1-800-424-9393. 1994 CHEVROLET TRUCK S10 1994 GMC S15 1995 CHEVROLET TRUCK S10 1995 GMC S15 1996 CHEVROLET TRUCK BLAZER 1996 CHEVROLET TRUCK S10 1996 GMC JIMMY 1996 GMC S15 1997 CHEVROLET TRUCK BLAZER 1997 CHEVROLET TRUCK S10 1997 GMC JIMMY 1997 GMC S15 1997 ISUZU TRUCK HOMBRE Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Specifications > 4L60-E Automatic Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Specifications > 4L60-E Automatic Transmission > Page 7465 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Locations > 4L60-E Automatic Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Locations > 4L60-E Automatic Transmission > Page 7468 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission Shift Solenoid: Service and Repair 4L60-E Automatic Transmission Pan and Filter Assembly PAN AND FILTER ASSEMBLY Pan, Filter And Seal Removal CLEAN - Exposed ends of bottom pan screws and spray with penetrating oil. REMOVE OR DISCONNECT 1. Screws (76), oil pan (75) and gasket (73). 2. Oil filter (72) and filter seal (71). - Filter seal may be stuck in the pump. INSPECT - Filter (72), open filter by prying the metal crimping away from the top of the filter (black) and pull apart. The filter may contain evidence for root cause diagnosis. Clutch material. - Bronze slivers indicating bushing wear. - Steel particles. Valve Body and Wiring Harness VALVE BODY AND WIRING HARNESS Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7471 Valve Body Bolt Location Control Valve And Pressure Switch Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7472 Manual Valve Link Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7473 Valve Body Checkballs Case Checkballs And Filters REMOVE OR DISCONNECT 1. Electrical connections from components. 2. TCC PWM Solenoid Retainer Clip (379) and Solenoid (396). 3. TCC Solenoid bolts (68) and solenoid assembly (66) with O-ring seal (65) and wiring harness. 4. Pressure switch assembly bolts (70) and pressure switch assembly (69). 5. Accumulator cover bolts (58 and 59) and 1-2 accumulator cover and pin assembly (57). 6. 1-2 accumulator piston (56) and seal (55). 7. Spring (54). 8. Dipstick stop bracket (93). REMOVE OR DISCONNECT 1. Bolt (64) and manual detent spring assembly (63). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7474 2. Wiring harness retaining bolts. REMOVE OR DISCONNECT 1. Remaining valve body bolts (62). 2. Manual valve link (89). 3. Control valve assembly (60). 4. Bolts (58 and 59), accumulator cover (57), piston (56, spring (54) and spring (54A). 5. Bolts (77) and plate (53). 6. Spacer plate (48) and spacer plate gaskets (47 and 52). 7. Spring (46), piston (44), and pin (43). - Seven checkballs are located under the valve body and one is located in the case. The large copper flash colored ball is # 1A checkball (91). Valve Body and Associated Parts VALVE BODY AND ASSOCIATED PARTS Accumulator Assembly, Spacer Plate And Gaskets Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7475 Case Checkballs And Filters TOOL REQUIRED: - J 25025-5 Guide Pins NOTICE: The use of a honing stone, fine sandpaper or crocus cloth is not recommended for servicing stuck valves. All valve lands have sharply machined corners that are necessary for "cleaning" the bore. If these corners are rounded, foreign material could wedge between the valve and bore causing the valve to stick. If it is found necessary to clean a valve, "micro fine" lapping compound 900 grit or finer should be used. Too much "lapping" of a valve will cause excessive clearances and increase the chance of a valve not operating. INSTALL OR CONNECT 1. The wiring harness pass-thru connector into the case. 2. The 3-4 accumulator pin (43) into the case. 3. The 3-4 accumulator piston seal (45) onto the 3-4 accumulator piston. 4. The 3-4 accumulator piston (44) onto the pin. - The end with three legs must face the valve body. 5. The 3-4 accumulator piston spring (46). INSTALL OR CONNECT 1. Checkball (91) into case as shown. - Retain with Transjel TM J 36850 or equivalent. 2. J 25025-5 into the case. 3. Screens onto spacer plate as shown. 4. Spacer plate to case gasket (47) and spacer plate to valve body gasket (52) onto the spacer plate (48). - Gasket (47) identified by a "C". Gasket (52) identified by a "V". - Retain with Transjel TM J 36850 or equivalent. 5. Spacer plate and gaskets onto the case. IMPORTANT - Be careful not to damage screens when installing the spacer plate and gaskets. 6. Spacer plate support (53) and bolts (77). TIGHTEN - Bolts to 11 Nm (8 lb. ft.) Control Valve Body CONTROL VALVE BODY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7476 Case Checkballs And Filters Filter Screen - Locations Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7477 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7478 Control Valve Assembly - Legend Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7479 Valve Body Checkball Locations Valve Body Bolt Locations Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7480 Manual Valve Link Outside Electrical Connector CLEAN - Control valve assembly thoroughly in clean solvent. A. Move the valves with a pick or small screwdriver to dislodge any dirt or debris that may have accumulated. B. Air dry. REMOVE OR DISCONNECT IMPORTANT - Some valves are under pressure - cover the bores while removing roll pins and retainer clips. - Valves, springs and bushings must be laid out on a clean surface in the exact sequence they are removed. 1. Pressure control solenoid retainer bolt (364) retainer (378) and solenoid. 2. Bore plug retainer clip (395), bore plug (376) and valve train (374 and 375). 3. 2-3 shift solenoid retainer (379), solenoid (367) and valve train (368 and 369). 4. 1-2 shift solenoid retainer (379), solenoid (367) and valve train (365 and 366). 5. Accumulator valve train retainer pin (360), bore plug (373) and valve train (370 and 371). 6. Forward accumulator cover bolts (364) and cover (363). 7. Forward accumulator spring (356), piston (354) and pin (355). 8. Lo overrun valve spring (362) and valve (361). 9. Retainer pin (360), bore plug (359) and forward abuse valve train (357 and 358). 10. Manual valve (340). 11. 3-2 control solenoid retainer clip (379) and solenoid (394). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7481 12. Bore plug retainer (395), bore plug (381) and 3-2 control valve train (391 - 393). 13. 3-2 downshift bore plug retainer (395), bore plug (381) and valve train (389 - 390). 14. Reverse abuse bore plug retainer pin (360), bore plug (359) and valve train (387 - 388). 15. 3-4 shift valve bore plug retainer (395), bore plug (381) and valve train (385 - 386). 16. 3-4 relay bore plug retainer (395), bore plug (381) and valve train (382 - 384). 17. Torque converter clutch signal valve bore plug retainer (395), bore plug (381) and valve (380). CLEAN - All valves, springs, bushings and control valve body in clean solvent. - Dry using compressed air. INSPECT - All valves and bushings for: Porosity - Scoring - Nicks - Scratches - Springs for damaged or distorted coils. - Valve body casting for: Porosity - Cracks - Inter connected oil passages - Damaged machined surfaces ASSEMBLE - Control valve assembly (350) exactly as shown. Notice the position of the valve lands and bushing passages. - Position the pressure control solenoid so the connector tabs face outward. NOTICE: TCC PWM solenoid (396) cannot be installed until TCC solenoid has been installed and torqued to proper specifications. INSTALL OR CONNECT 1. Checkballs into the valve body assembly (350). - Retain with Transjell TM J 36850 or equivalent. 2. Valve body assembly (350). - Connect the manual valve link (89) to the inside detent lever (88). - Be careful not to damage screens when installing the valve body assembly. 3. Wiring harness (66), manual spring assembly (63), pressure switch assembly(69), dipstick, stop bracket (93) and all remaining valve body bolts. NOTICE: Torque valve body bolts in a spiral pattern starting from the center. If bolts are torqued at random, valve bores may be distorted and inhibit valve operation. 4. TCC solenoid (66) and bolts (68). TIGHTEN - Bolts to 11 Nm (8 lb. ft.). 5. TCC PWM solenoid (396), and retainer clip (379). INSTALL OR CONNECT - Wiring harness connections to electrical components. - To correctly hook up the wires, see the wiring diagrams. - The pressure control solenoid (377) has two different colored connectors. The black connector should be installed on the tab farthest from the valve body. INSTALL OR CONNECT 1. Parking bracket (86). TIGHTEN - Bolts to 31 Nm (23 lb. ft.). 2. The 1-2 accumulator piston seal (55) onto the 1-2 accumulator piston (56). 3. The 1-2 accumulator spring (54) and 1-2 accumulator inner spring (54A) onto the piston (56). 4. The 1-2 accumulator piston (56) into the 1-2 accumulator cover and pin assembly (57). - The three legs on the piston must face away from the case when installed. 5. The 1-2 accumulator cover and pin assembly (57) onto the case. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7482 TIGHTEN - Torque to 11 Nm (8 lb. ft.). Pan and Filter Assembly PAN AND FILTER ASSEMBLY Case, Pan And Filter Assembly INSTALL OR CONNECT 1. Filter seal (71) into the pump. 2. Oil filter (72). 3. Oil pan gasket (73). 4. Chip magnet (74) onto oil pan (75). 5. Oil pan (75) and bolts (76). TIGHTEN - Torque to 12 Nm (9 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7483 Shift Solenoid: Service and Repair 4L80-E Automatic Transmission Pan and Filter Assembly PAN AND FILTER ASSEMBLY Pan, Filter And Seal Removal REMOVE OR DISCONNECT 1. Drain the transmission fluid Out case extension by rotating transmission to a vertical position. 2. Seventeen bolts (27), using 10 mm socket, drain transmission fluid. 3. Pan (28), seal (29) and magnet (30). IMPORTANT - Seal (29) is reusable. 4. Filter assembly (31). INSPECT - Filter neck seal (32), replace if necessary. Wire Harness Assembly WIRE HARNESS ASSEMBLY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7484 Pan, Filter And Seal Removal REMOVE OR DISCONNECT 1. Wire harness connectors from electrical components. NOTICE: Excessive force on the case pass through connector may damage the connector. IMPORTANT - If the wire harness assembly does not need servicing, it is not necessary to remove it from the case. 2. Wire harness assembly (34) from case using a 1-5/16" 12 point socket to release the connector retaining clips. Control Valve Assembly CONTROL VALVE ASSEMBLY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7485 REMOVE OR DISCONNECT 1. Rotate transmission bottom pan surface up and lock in place. 2. Wire harness assembly (34) connectors from components. IMPORTANT - If the wire harness assembly does not need servicing, it is not necessary to remove it from the case. - Use a cap to cover electrical pin at case connection. 3. Six bolts (76) using 8 mm socket, and transmission fluid pressure switch assembly (40). NOTICE: Be sure five O-rings are attached to transmission fluid pressure switch assembly. 4. Twenty-one bolts (35) using 10 mm socket, from valve body assembly, manual detent spring and roller assembly (41). 5. Three wiring clamps (33), fluid level indicator stop (43), one bolt (36) using 10 mm socket, lube pipe (39), lube pipe retainer (37) and clamp (38). 6. Control valve assembly (44) including the accumulator housing assembly (51), valve body gaskets (45 and 48), spacer plate (46) and accumulator gasket (47). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7486 7. Manual valve (319) from control valve assembly (44) to prevent any damage. 8. Checkballs (54) from case passages. NOTICE: Do not use a magnet. It could cause checkball(s) to be magnetized causing metal particles to stick to the ball. 9. Pulse Width Modulated (PWM) solenoid screen (75). INSPECT - Screen PWM solenoid (75), replace if necessary. DISASSEMBLE Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7487 - Control valve assembly. A. Position as shown on a clean surface. B. Remove blind hole retainer pins with a drill bit. CAUTION: Some valves are under pressure - cover the bores while removing the retaining pins or personal injury could result. C. Remove valve trains, shift solenoids (311 and 313), PCS (320), PWM solenoid (323), PCS screen (302) and shift solenoid filter (317). D. Valves, springs, bushings and pistons must be laid out on a clean surface. CLEAN - All valves, springs, bushings, pistons, control valve body and accumulator housing in clean solvent. - Dry using compressed air. INSPECT 1. All valves, pistons and bushings for: - Porosity. - Scoring. - Nicks. - Scratches. 2. Pistons for: - Seal damage. 3. Springs for: - Damaged or distorted coils. 4. Valve body casting and accumulator housing for: - Porosity. - Cracks. - Interconnected passages. - Damaged machined surfaces. 5. Solenoid connectors and filter (317). 6. PCS (Pressure Control Solenoid) screen (302). Control Valve Assembly/Accumulator Housing CONTROL VALVE ASSEMBLY/ACCUMULATOR HOUSING Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7488 Control Valve Assembly/Accumulator Housing Accumulator Housing Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7489 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7490 Torque Sequence And Guide Pin Location Fig. 11 Check Ball Location. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7491 Fig. 10 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7492 Torque Sequence, Control Valve And Switch Assembly NOTICE: The use of a honing stone, fine sandpaper or crocus cloth is not recommended for servicing stuck valves. All valve lands have sharply machined comers that are necessary for cleaning the bore. If these corners are rounded, foreign material could wedge between the valve and the bore causing the valve to stick. If it is found necessary to clean a valve, micro fine lapping compound 900 grit (J 38459) or finer should be used. Too much lapping of the valve will cause excessive clearances and increase the chance of a valve not operating. CLEAN - Control valve assembly and accumulator housing (51) thoroughly in clean solvent. - Air dry. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7493 Accumulator Housing Assembly ACCUMULATOR HOUSING ASSEMBLY Control Valve Assembly/Accumulator Housing Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7494 Accumulator Housing Assembly DISASSEMBLE 1. Six bolts (53), using 8 mm socket. 2. Accumulator housing assembly. 3. Gasket accumulator housing (47). 4. Spacer plate (46). 5. Gasket (45) valve body spacer. 6. Snap ring (402) from outside housing, pin (408), snap ring (402), piston (407) and spring (49). 7. 3rd clutch piston (405) and spring (50). 8. Seals (404 and 406). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7495 CLEAN - All components. INSPECT - All valves, pistons, springs and seals for: - Porosity. - Scoring. - Nicks. - Scratches. Accumulator Housing Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7496 ASSEMBLE - Accumulator housing assembly components exactly as shown. Notice the positions of the pistons. Control Valve Assembly CONTROL VALVE ASSEMBLY Control Valve Assembly ASSEMBLE - Control valve assembly components exactly as shown. Notice the position of the valve lands and bushing passages. Control Valve Assembly/Accumulator Housing Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7497 CONTROL VALVE ASSEMBLY AND ACCUMULATOR HOUSING Control Valve Assembly/Accumulator Housing Torque Sequence And Guide Pin Location TOOL REQUIRED: - Guide Pin J 25025-5 ASSEMBLE 1. Guide pin J 25025-5 into valve body. Located at back bolt hole of detent spring and roller assembly bolt bole. 2. Gasket (45) valve body to spacer plate. 3. Spacer plate (46). 4. Gasket (47) accumulator housing to spacer plate. 5. Accumulator housing assembly (51) onto valve body assembly (44). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7498 6. Six bolts (53) using (8 mm) socket through accumulator housing into valve body assembly. Torque Sequence And Guide Pin Location NOTE: Start accumulator housing bolts finger tight and work towards opposite end. TIGHTEN - Bolt (53) to 11 Nm (97 lb. in.). 7. Remove guide pin J 25025-5. Fig. 11 Check Ball Location. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7499 Fig. 10 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7500 Torque Sequence, Control Valve And Switch Assembly INSTALL OR CONNECT 1. Install checkballs (54) in proper location into case fluid passages. Use TRANSJEL TM J 36850 or equivalent to hold in place. NOTICE: Do not use any type of grease to retain parts during assembly of this unit. Greases other than the recommended assembly lube will change transmission fluid characteristics and cause undesirable shift conditions and/or filter clogging. - # 2 checkball is used only on RCP RDP, ZJP and ZLP models. 2. PWM solenoid screen (75). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7501 3. Gasket (48) spacer plate to case. 4. Manual valve (319) into valve body. 5. Complete valve body assembly (44) onto case (7). Use 1 25025-5 guide pin set. IMPORTANT - Attach manual valve to detent lever. 6. Transmission fluid pressure switch assembly (40) onto valve body assembly (44). 7. Spring and roller assembly (41) into place. 8. Three wiring clamps (33), fluid indicator stop (43) and lube pipe clamp (38). 9. Twenty-one bolts (35). Using 10 mm socket. 10. Six bolts (76) using 8 mm socket into transmission fluid pressure switch assembly (40). 11. Lube pipe (39) long end into case, short end into valve body. 12. Lube pipe retainer (37) with short bolt (36). TIGHTEN - Bolts (35, 36 and 76) to 11 Nm (97 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7502 Torque Sequence, Control Valve And Switch Assembly NOTICE: Torque valve body bolts in a spiral pattern starting from the center. If bolts are torqued at random, valve bores may be distorted and inhibit valve operation. 13. Attach wiring harness (34) to 5 connectors. - Put large end into case first, pressure switch hook up, 1-2 shift solenoid (purple) and 2-3 shift solenoid (tan), PWM (Pulse Width Modulated) solenoid and PCS (Pressure Control Solenoid). Pan and Filter Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7503 PAN AND FILTER ASSEMBLY Installing Pan And Filter INSTALL OR CONNECT 1. Seal (32) inside of case (7). 2. Filter assembly (31). 3. Bottom pan seal (29). 4. Magnet (30) into bottom pan. 5. Pan (29). 6. Seventeen bolts (27) using 10 mm socket. TIGHTEN - Bolts (27) to 24 Nm (18 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON Torque Converter Clutch Solenoid: Customer Interest A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-023B Date: March, 2002 TECHNICAL Subject: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1999-2000 Cadillac Escalade 1996-2000 Chevrolet Camaro, Corvette 1996-2000 Pontiac Firebird 1996-2000 Chevrolet and GMC Light Duty Truck Models 1996-2000 Oldsmobile Bravada with 4L60-E Automatic Transmission (RPO M30) Built Prior to January 15, 2000 (Julian Date 0015) This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 Transmission/Transaxle). Condition Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated. Diagnosis Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs. The scan tool may show a DTC P1870 set as a history code. A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93° C (200°F). Cause The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply. Important: ^ DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code. ^ When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result. ^ This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle). ^ When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code. ^ When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL). Correction Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 7512 regulator and isolator valves. Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body. ^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears). ^ The torque converter is not blue or overheated. ^ The transmission fluid is not burned or has no burned odor ^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 7513 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON Torque Converter Clutch Solenoid: All Technical Service Bulletins A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-023B Date: March, 2002 TECHNICAL Subject: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1999-2000 Cadillac Escalade 1996-2000 Chevrolet Camaro, Corvette 1996-2000 Pontiac Firebird 1996-2000 Chevrolet and GMC Light Duty Truck Models 1996-2000 Oldsmobile Bravada with 4L60-E Automatic Transmission (RPO M30) Built Prior to January 15, 2000 (Julian Date 0015) This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 Transmission/Transaxle). Condition Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated. Diagnosis Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs. The scan tool may show a DTC P1870 set as a history code. A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93° C (200°F). Cause The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply. Important: ^ DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code. ^ When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result. ^ This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle). ^ When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code. ^ When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL). Correction Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 7519 regulator and isolator valves. Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body. ^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears). ^ The torque converter is not blue or overheated. ^ The transmission fluid is not burned or has no burned odor ^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Actuators and Solenoids - Transmission and Drivetrain > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 7520 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Interlock Solenoid > Component Information > Locations Shift Interlock Solenoid: Locations RH side of steering column, under Support bracket. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling Shift Solenoid: Customer Interest A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling File In Section: 7 Transmission Bulletin No.: 77-71-77 Date: December, 1997 Subject: Loss of 4th Gear, Slipping in 4th Gear, Busy 3-4 Shifting or TCC Cycling (Replace Shift Solenoids) Models: 1996-97 Chevrolet and GMC C/K, G, P Models with HYDRA-MATIC 4L8OE Transmission (RPO MT1) Condition Some owners may comment about a loss of 4th gear, slipping in 4th gear, busy 3-4 shifting or Torque Converter Clutch (TCC) cycling and no DTC's are setting. Cause Shift solenoid leaking hydraulically. Correction If normal diagnosis does not provide a correction, follow the solenoid test procedure listed. Replace the shift solenoid if it fails the test. Also verify that the transmission cooling system is operating properly. Service Information (figure 1) Starting June 23, 1997 (Julian date 174) all HYDRA-MATIC 4L80-E transmissions are being built with the new solenoid assemblies. The new solenoids will service all 1991 through 1997 4L80-E applications. The above listed conditions occur mainly on high duty cycle applications and/or when the transmission is operated under high temperature conditions. Each solenoid may be tested for leaking using the following test: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling > Page 7534 1. Remove the solenoid from the control valve body. Refer to the Service Manual for the proper procedure. 2. Clamp a piece of 1/2 inch I.D. rubber hose over the fluid inlet end of the solenoid. 3. Connect a wire from one of the solenoid terminals to the negative terminal (ground) of a battery. 4. Apply compressed air to the rubber hose. Do not use air pressure in excess of 120 psi. Excessive pressure will not allow the check ball to seat properly. 5. Connect a wire from the other solenoid to the positive terminal (12 volts) of the battery. 6. Observe the air flow through the solenoid. Replace the solenoid if there is an air leak when the solenoid is energized. Parts Information New Part Number Description 10478140 1-2 & 3-4 Shift Solenoid (black) 10478141 2-3 Shift Solenoid (white) Parts are currently available through GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift Shift Solenoid: Customer Interest A/T - Engine Speed Flare During Part Throttle Downshift File In Section: 7 - Transmission Bulletin No.: 67-71-47 Date: July, 1996 Subject: 3-2 Part Throttle Downshift Flare (Replace 3-2 Solenoid) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1996 Chevrolet Camaro, Caprice, Corvette 1996 Pontiac Firebird 1996 Chevrolet and GMC C/K, M/L, S/T, G Models 1996 Oldsmobile Bravada with HYDRA-MATIC 4L60-E (RPO M30) Condition (Figures 1 and 2) Some owners of the above models with a HYDRA-MATIC 4L60-E transmission (built before May 24, 1996/Julian Date 6145) may experience an engine speed flare of 1000-2000 RPM, during a part throttle downshift at 19-31 mph. This condition will not set any DTC's (Diagnostic Trouble Codes). Cause Exhaust seat on the 3-2 control solenoid backing out. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift > Page 7539 Correction (Figure 3) Replace the 3-2 control solenoid. Julian Date on the solenoid will be May 13, 1996 (6134) or later. Parts Information New Part Number Description 24209121 Solenoid, 3-2 Control Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time K6559 Replace 3-2 Use published labor Control Solenoid operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling Shift Solenoid: All Technical Service Bulletins A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling File In Section: 7 Transmission Bulletin No.: 77-71-77 Date: December, 1997 Subject: Loss of 4th Gear, Slipping in 4th Gear, Busy 3-4 Shifting or TCC Cycling (Replace Shift Solenoids) Models: 1996-97 Chevrolet and GMC C/K, G, P Models with HYDRA-MATIC 4L8OE Transmission (RPO MT1) Condition Some owners may comment about a loss of 4th gear, slipping in 4th gear, busy 3-4 shifting or Torque Converter Clutch (TCC) cycling and no DTC's are setting. Cause Shift solenoid leaking hydraulically. Correction If normal diagnosis does not provide a correction, follow the solenoid test procedure listed. Replace the shift solenoid if it fails the test. Also verify that the transmission cooling system is operating properly. Service Information (figure 1) Starting June 23, 1997 (Julian date 174) all HYDRA-MATIC 4L80-E transmissions are being built with the new solenoid assemblies. The new solenoids will service all 1991 through 1997 4L80-E applications. The above listed conditions occur mainly on high duty cycle applications and/or when the transmission is operated under high temperature conditions. Each solenoid may be tested for leaking using the following test: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling > Page 7545 1. Remove the solenoid from the control valve body. Refer to the Service Manual for the proper procedure. 2. Clamp a piece of 1/2 inch I.D. rubber hose over the fluid inlet end of the solenoid. 3. Connect a wire from one of the solenoid terminals to the negative terminal (ground) of a battery. 4. Apply compressed air to the rubber hose. Do not use air pressure in excess of 120 psi. Excessive pressure will not allow the check ball to seat properly. 5. Connect a wire from the other solenoid to the positive terminal (12 volts) of the battery. 6. Observe the air flow through the solenoid. Replace the solenoid if there is an air leak when the solenoid is energized. Parts Information New Part Number Description 10478140 1-2 & 3-4 Shift Solenoid (black) 10478141 2-3 Shift Solenoid (white) Parts are currently available through GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 377148A > Nov > 96 > A/T - Shift Solenoid Update Shift Solenoid: All Technical Service Bulletins A/T - Shift Solenoid Update File In Section: 7 Transmission Bulletin No.: 37-71-48A Date: November, 1996 INFORMATION Subject: Transmission Product Updates (New Shift Solenoids) Models: 1991-97 Chevrolet and GMC C/K, P, G Models 1991 Chevrolet and GMC R/V Models with HYDRA-MATIC 4L8O-E Transmission (RPO MT1) This bulletin is being revised to update the part numbers and to include 1995-97 model years. Please discard Corporate Bulletin Number 377148 (Section 7 - Transmission). Service Information Starting August 14, 1996 (Julian date 226) all HYDRA-MATIC 4L80-E transmissions are being built with the new solenoid assemblies. The new solenoids are serviced for all 1991 through 1997 4L80-E applications. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 377148A > Nov > 96 > A/T - Shift Solenoid Update > Page 7550 Parts Information Previous Part New Part Description 10478125 10478132 Valve assembly, 1-2 Shift Solenoid (Black) 10478126 10478133 Valve assembly, 2-3 Shift Solenoid (White) Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift Shift Solenoid: All Technical Service Bulletins A/T - Engine Speed Flare During Part Throttle Downshift File In Section: 7 - Transmission Bulletin No.: 67-71-47 Date: July, 1996 Subject: 3-2 Part Throttle Downshift Flare (Replace 3-2 Solenoid) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1996 Chevrolet Camaro, Caprice, Corvette 1996 Pontiac Firebird 1996 Chevrolet and GMC C/K, M/L, S/T, G Models 1996 Oldsmobile Bravada with HYDRA-MATIC 4L60-E (RPO M30) Condition (Figures 1 and 2) Some owners of the above models with a HYDRA-MATIC 4L60-E transmission (built before May 24, 1996/Julian Date 6145) may experience an engine speed flare of 1000-2000 RPM, during a part throttle downshift at 19-31 mph. This condition will not set any DTC's (Diagnostic Trouble Codes). Cause Exhaust seat on the 3-2 control solenoid backing out. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift > Page 7555 Correction (Figure 3) Replace the 3-2 control solenoid. Julian Date on the solenoid will be May 13, 1996 (6134) or later. Parts Information New Part Number Description 24209121 Solenoid, 3-2 Control Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time K6559 Replace 3-2 Use published labor Control Solenoid operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Shift Solenoid: > 564203A > Nov > 96 > Rear Axle - Vent Leak Differential Case: All Technical Service Bulletins Rear Axle - Vent Leak File In Section: 4 - Drive Axle Bulletin No.: 56-42-03A Date: November, 1996 Subject: Rear Axle Vent Leak (Relocate Rear Axle Vent Tube) Models: 1993-96 Chevrolet and GMC C/K 2, 3 Models with 10.5" Rear Axles This bulletin is being revised to add the 1996 model year. Please discard Corporate Bulletin Number 56-42-03 (Section 4 - Drive Axle) Condition Some owners may comment about an oil soaked load floor or oil leaking from the rear axle vent. Correction Following the instructions given below, relocate the rear axle vent tube to the axle tube. Service Procedure 1. Raise the vehicle and support with suitable safety stands. 2. Disconnect the vent hose from the vent tube and remove the vent tube. 3. Plug the existing vent hole with weld bond epoxy such as J.B. Weld or equivalent following the manufacturer's instructions. 4. Remove the driver's side axle shaft following the procedure in Section 4B1 of the appropriate year Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Shift Solenoid: > 564203A > Nov > 96 > Rear Axle - Vent Leak > Page 7561 5. Locate the shock mount bracket on the driver's side axle tube (Figure 1). At the top of the axle tube, parallel to the center of the shock bracket, drill a 3/8" hole in the axle tube. Notice: Precaution should be taken to ensure that no metal fragments enter the axle tube. Use a magnet when drilling to lift and catch the metal filings. Apply wheel bearing grease to the drill bit before breaking through the axle tube. 6. Using a 12 mm socket, drive a new vent tube (P/N 14072930) into the axle tube at the location drilled in step 5. Seal the base of the vent tube with RTV sealant (P/N 12345739). 7. Use an extendable magnet tool to capture any metal fragments that may have fallen into the axle tube and then re-install the driver's side axle shaft following the procedure in Section 4B1 of the appropriate year Service Manual. 8. Cut approximately 8.5" (216 mm) off the existing vent hose and discard after verifying that enough vent hose will remain to allow for axle movement. Clamp the remaining hose onto the new axle vent tube installed in step 7. 9. Check the rear axle fluid level. Add fluid if necessary (P/N 1052271 80W-90 GL-5). 10. Lower the vehicle and test drive. Parts Information P/N Description Qty 14072930 Vent Tube 1 12345739 RTV Sealant As Required 1052271 Rear Axle As Required Lubricating Oil Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Shift Solenoid: > 564203A > Nov > 96 > Rear Axle - Vent Leak > Page 7562 Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time F3270 Rear Vent Replace Use Published Labor Operation Time F1531 Left Axle Shaft R&R; Use Published Labor Operation Time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Shift Solenoid: > 564203A > Nov > 96 > Rear Axle - Vent Leak > Page 7568 5. Locate the shock mount bracket on the driver's side axle tube (Figure 1). At the top of the axle tube, parallel to the center of the shock bracket, drill a 3/8" hole in the axle tube. Notice: Precaution should be taken to ensure that no metal fragments enter the axle tube. Use a magnet when drilling to lift and catch the metal filings. Apply wheel bearing grease to the drill bit before breaking through the axle tube. 6. Using a 12 mm socket, drive a new vent tube (P/N 14072930) into the axle tube at the location drilled in step 5. Seal the base of the vent tube with RTV sealant (P/N 12345739). 7. Use an extendable magnet tool to capture any metal fragments that may have fallen into the axle tube and then re-install the driver's side axle shaft following the procedure in Section 4B1 of the appropriate year Service Manual. 8. Cut approximately 8.5" (216 mm) off the existing vent hose and discard after verifying that enough vent hose will remain to allow for axle movement. Clamp the remaining hose onto the new axle vent tube installed in step 7. 9. Check the rear axle fluid level. Add fluid if necessary (P/N 1052271 80W-90 GL-5). 10. Lower the vehicle and test drive. Parts Information P/N Description Qty 14072930 Vent Tube 1 12345739 RTV Sealant As Required 1052271 Rear Axle As Required Lubricating Oil Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Shift Solenoid: > 564203A > Nov > 96 > Rear Axle - Vent Leak > Page 7569 Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time F3270 Rear Vent Replace Use Published Labor Operation Time F1531 Left Axle Shaft R&R; Use Published Labor Operation Time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Specifications > 4L60-E Automatic Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Specifications > 4L60-E Automatic Transmission > Page 7572 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Locations > 4L60-E Automatic Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Locations > 4L60-E Automatic Transmission > Page 7575 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission Shift Solenoid: Service and Repair 4L60-E Automatic Transmission Pan and Filter Assembly PAN AND FILTER ASSEMBLY Pan, Filter And Seal Removal CLEAN - Exposed ends of bottom pan screws and spray with penetrating oil. REMOVE OR DISCONNECT 1. Screws (76), oil pan (75) and gasket (73). 2. Oil filter (72) and filter seal (71). - Filter seal may be stuck in the pump. INSPECT - Filter (72), open filter by prying the metal crimping away from the top of the filter (black) and pull apart. The filter may contain evidence for root cause diagnosis. Clutch material. - Bronze slivers indicating bushing wear. - Steel particles. Valve Body and Wiring Harness VALVE BODY AND WIRING HARNESS Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7578 Valve Body Bolt Location Control Valve And Pressure Switch Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7579 Manual Valve Link Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7580 Valve Body Checkballs Case Checkballs And Filters REMOVE OR DISCONNECT 1. Electrical connections from components. 2. TCC PWM Solenoid Retainer Clip (379) and Solenoid (396). 3. TCC Solenoid bolts (68) and solenoid assembly (66) with O-ring seal (65) and wiring harness. 4. Pressure switch assembly bolts (70) and pressure switch assembly (69). 5. Accumulator cover bolts (58 and 59) and 1-2 accumulator cover and pin assembly (57). 6. 1-2 accumulator piston (56) and seal (55). 7. Spring (54). 8. Dipstick stop bracket (93). REMOVE OR DISCONNECT 1. Bolt (64) and manual detent spring assembly (63). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7581 2. Wiring harness retaining bolts. REMOVE OR DISCONNECT 1. Remaining valve body bolts (62). 2. Manual valve link (89). 3. Control valve assembly (60). 4. Bolts (58 and 59), accumulator cover (57), piston (56, spring (54) and spring (54A). 5. Bolts (77) and plate (53). 6. Spacer plate (48) and spacer plate gaskets (47 and 52). 7. Spring (46), piston (44), and pin (43). - Seven checkballs are located under the valve body and one is located in the case. The large copper flash colored ball is # 1A checkball (91). Valve Body and Associated Parts VALVE BODY AND ASSOCIATED PARTS Accumulator Assembly, Spacer Plate And Gaskets Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7582 Case Checkballs And Filters TOOL REQUIRED: - J 25025-5 Guide Pins NOTICE: The use of a honing stone, fine sandpaper or crocus cloth is not recommended for servicing stuck valves. All valve lands have sharply machined corners that are necessary for "cleaning" the bore. If these corners are rounded, foreign material could wedge between the valve and bore causing the valve to stick. If it is found necessary to clean a valve, "micro fine" lapping compound 900 grit or finer should be used. Too much "lapping" of a valve will cause excessive clearances and increase the chance of a valve not operating. INSTALL OR CONNECT 1. The wiring harness pass-thru connector into the case. 2. The 3-4 accumulator pin (43) into the case. 3. The 3-4 accumulator piston seal (45) onto the 3-4 accumulator piston. 4. The 3-4 accumulator piston (44) onto the pin. - The end with three legs must face the valve body. 5. The 3-4 accumulator piston spring (46). INSTALL OR CONNECT 1. Checkball (91) into case as shown. - Retain with Transjel TM J 36850 or equivalent. 2. J 25025-5 into the case. 3. Screens onto spacer plate as shown. 4. Spacer plate to case gasket (47) and spacer plate to valve body gasket (52) onto the spacer plate (48). - Gasket (47) identified by a "C". Gasket (52) identified by a "V". - Retain with Transjel TM J 36850 or equivalent. 5. Spacer plate and gaskets onto the case. IMPORTANT - Be careful not to damage screens when installing the spacer plate and gaskets. 6. Spacer plate support (53) and bolts (77). TIGHTEN - Bolts to 11 Nm (8 lb. ft.) Control Valve Body CONTROL VALVE BODY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7583 Case Checkballs And Filters Filter Screen - Locations Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7584 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7585 Control Valve Assembly - Legend Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7586 Valve Body Checkball Locations Valve Body Bolt Locations Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7587 Manual Valve Link Outside Electrical Connector CLEAN - Control valve assembly thoroughly in clean solvent. A. Move the valves with a pick or small screwdriver to dislodge any dirt or debris that may have accumulated. B. Air dry. REMOVE OR DISCONNECT IMPORTANT - Some valves are under pressure - cover the bores while removing roll pins and retainer clips. - Valves, springs and bushings must be laid out on a clean surface in the exact sequence they are removed. 1. Pressure control solenoid retainer bolt (364) retainer (378) and solenoid. 2. Bore plug retainer clip (395), bore plug (376) and valve train (374 and 375). 3. 2-3 shift solenoid retainer (379), solenoid (367) and valve train (368 and 369). 4. 1-2 shift solenoid retainer (379), solenoid (367) and valve train (365 and 366). 5. Accumulator valve train retainer pin (360), bore plug (373) and valve train (370 and 371). 6. Forward accumulator cover bolts (364) and cover (363). 7. Forward accumulator spring (356), piston (354) and pin (355). 8. Lo overrun valve spring (362) and valve (361). 9. Retainer pin (360), bore plug (359) and forward abuse valve train (357 and 358). 10. Manual valve (340). 11. 3-2 control solenoid retainer clip (379) and solenoid (394). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7588 12. Bore plug retainer (395), bore plug (381) and 3-2 control valve train (391 - 393). 13. 3-2 downshift bore plug retainer (395), bore plug (381) and valve train (389 - 390). 14. Reverse abuse bore plug retainer pin (360), bore plug (359) and valve train (387 - 388). 15. 3-4 shift valve bore plug retainer (395), bore plug (381) and valve train (385 - 386). 16. 3-4 relay bore plug retainer (395), bore plug (381) and valve train (382 - 384). 17. Torque converter clutch signal valve bore plug retainer (395), bore plug (381) and valve (380). CLEAN - All valves, springs, bushings and control valve body in clean solvent. - Dry using compressed air. INSPECT - All valves and bushings for: Porosity - Scoring - Nicks - Scratches - Springs for damaged or distorted coils. - Valve body casting for: Porosity - Cracks - Inter connected oil passages - Damaged machined surfaces ASSEMBLE - Control valve assembly (350) exactly as shown. Notice the position of the valve lands and bushing passages. - Position the pressure control solenoid so the connector tabs face outward. NOTICE: TCC PWM solenoid (396) cannot be installed until TCC solenoid has been installed and torqued to proper specifications. INSTALL OR CONNECT 1. Checkballs into the valve body assembly (350). - Retain with Transjell TM J 36850 or equivalent. 2. Valve body assembly (350). - Connect the manual valve link (89) to the inside detent lever (88). - Be careful not to damage screens when installing the valve body assembly. 3. Wiring harness (66), manual spring assembly (63), pressure switch assembly(69), dipstick, stop bracket (93) and all remaining valve body bolts. NOTICE: Torque valve body bolts in a spiral pattern starting from the center. If bolts are torqued at random, valve bores may be distorted and inhibit valve operation. 4. TCC solenoid (66) and bolts (68). TIGHTEN - Bolts to 11 Nm (8 lb. ft.). 5. TCC PWM solenoid (396), and retainer clip (379). INSTALL OR CONNECT - Wiring harness connections to electrical components. - To correctly hook up the wires, see the wiring diagrams. - The pressure control solenoid (377) has two different colored connectors. The black connector should be installed on the tab farthest from the valve body. INSTALL OR CONNECT 1. Parking bracket (86). TIGHTEN - Bolts to 31 Nm (23 lb. ft.). 2. The 1-2 accumulator piston seal (55) onto the 1-2 accumulator piston (56). 3. The 1-2 accumulator spring (54) and 1-2 accumulator inner spring (54A) onto the piston (56). 4. The 1-2 accumulator piston (56) into the 1-2 accumulator cover and pin assembly (57). - The three legs on the piston must face away from the case when installed. 5. The 1-2 accumulator cover and pin assembly (57) onto the case. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7589 TIGHTEN - Torque to 11 Nm (8 lb. ft.). Pan and Filter Assembly PAN AND FILTER ASSEMBLY Case, Pan And Filter Assembly INSTALL OR CONNECT 1. Filter seal (71) into the pump. 2. Oil filter (72). 3. Oil pan gasket (73). 4. Chip magnet (74) onto oil pan (75). 5. Oil pan (75) and bolts (76). TIGHTEN - Torque to 12 Nm (9 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7590 Shift Solenoid: Service and Repair 4L80-E Automatic Transmission Pan and Filter Assembly PAN AND FILTER ASSEMBLY Pan, Filter And Seal Removal REMOVE OR DISCONNECT 1. Drain the transmission fluid Out case extension by rotating transmission to a vertical position. 2. Seventeen bolts (27), using 10 mm socket, drain transmission fluid. 3. Pan (28), seal (29) and magnet (30). IMPORTANT - Seal (29) is reusable. 4. Filter assembly (31). INSPECT - Filter neck seal (32), replace if necessary. Wire Harness Assembly WIRE HARNESS ASSEMBLY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7591 Pan, Filter And Seal Removal REMOVE OR DISCONNECT 1. Wire harness connectors from electrical components. NOTICE: Excessive force on the case pass through connector may damage the connector. IMPORTANT - If the wire harness assembly does not need servicing, it is not necessary to remove it from the case. 2. Wire harness assembly (34) from case using a 1-5/16" 12 point socket to release the connector retaining clips. Control Valve Assembly CONTROL VALVE ASSEMBLY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7592 REMOVE OR DISCONNECT 1. Rotate transmission bottom pan surface up and lock in place. 2. Wire harness assembly (34) connectors from components. IMPORTANT - If the wire harness assembly does not need servicing, it is not necessary to remove it from the case. - Use a cap to cover electrical pin at case connection. 3. Six bolts (76) using 8 mm socket, and transmission fluid pressure switch assembly (40). NOTICE: Be sure five O-rings are attached to transmission fluid pressure switch assembly. 4. Twenty-one bolts (35) using 10 mm socket, from valve body assembly, manual detent spring and roller assembly (41). 5. Three wiring clamps (33), fluid level indicator stop (43), one bolt (36) using 10 mm socket, lube pipe (39), lube pipe retainer (37) and clamp (38). 6. Control valve assembly (44) including the accumulator housing assembly (51), valve body gaskets (45 and 48), spacer plate (46) and accumulator gasket (47). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7593 7. Manual valve (319) from control valve assembly (44) to prevent any damage. 8. Checkballs (54) from case passages. NOTICE: Do not use a magnet. It could cause checkball(s) to be magnetized causing metal particles to stick to the ball. 9. Pulse Width Modulated (PWM) solenoid screen (75). INSPECT - Screen PWM solenoid (75), replace if necessary. DISASSEMBLE Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7594 - Control valve assembly. A. Position as shown on a clean surface. B. Remove blind hole retainer pins with a drill bit. CAUTION: Some valves are under pressure - cover the bores while removing the retaining pins or personal injury could result. C. Remove valve trains, shift solenoids (311 and 313), PCS (320), PWM solenoid (323), PCS screen (302) and shift solenoid filter (317). D. Valves, springs, bushings and pistons must be laid out on a clean surface. CLEAN - All valves, springs, bushings, pistons, control valve body and accumulator housing in clean solvent. - Dry using compressed air. INSPECT 1. All valves, pistons and bushings for: - Porosity. - Scoring. - Nicks. - Scratches. 2. Pistons for: - Seal damage. 3. Springs for: - Damaged or distorted coils. 4. Valve body casting and accumulator housing for: - Porosity. - Cracks. - Interconnected passages. - Damaged machined surfaces. 5. Solenoid connectors and filter (317). 6. PCS (Pressure Control Solenoid) screen (302). Control Valve Assembly/Accumulator Housing CONTROL VALVE ASSEMBLY/ACCUMULATOR HOUSING Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7595 Control Valve Assembly/Accumulator Housing Accumulator Housing Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7596 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7597 Torque Sequence And Guide Pin Location Fig. 11 Check Ball Location. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7598 Fig. 10 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7599 Torque Sequence, Control Valve And Switch Assembly NOTICE: The use of a honing stone, fine sandpaper or crocus cloth is not recommended for servicing stuck valves. All valve lands have sharply machined comers that are necessary for cleaning the bore. If these corners are rounded, foreign material could wedge between the valve and the bore causing the valve to stick. If it is found necessary to clean a valve, micro fine lapping compound 900 grit (J 38459) or finer should be used. Too much lapping of the valve will cause excessive clearances and increase the chance of a valve not operating. CLEAN - Control valve assembly and accumulator housing (51) thoroughly in clean solvent. - Air dry. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7600 Accumulator Housing Assembly ACCUMULATOR HOUSING ASSEMBLY Control Valve Assembly/Accumulator Housing Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7601 Accumulator Housing Assembly DISASSEMBLE 1. Six bolts (53), using 8 mm socket. 2. Accumulator housing assembly. 3. Gasket accumulator housing (47). 4. Spacer plate (46). 5. Gasket (45) valve body spacer. 6. Snap ring (402) from outside housing, pin (408), snap ring (402), piston (407) and spring (49). 7. 3rd clutch piston (405) and spring (50). 8. Seals (404 and 406). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7602 CLEAN - All components. INSPECT - All valves, pistons, springs and seals for: - Porosity. - Scoring. - Nicks. - Scratches. Accumulator Housing Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7603 ASSEMBLE - Accumulator housing assembly components exactly as shown. Notice the positions of the pistons. Control Valve Assembly CONTROL VALVE ASSEMBLY Control Valve Assembly ASSEMBLE - Control valve assembly components exactly as shown. Notice the position of the valve lands and bushing passages. Control Valve Assembly/Accumulator Housing Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7604 CONTROL VALVE ASSEMBLY AND ACCUMULATOR HOUSING Control Valve Assembly/Accumulator Housing Torque Sequence And Guide Pin Location TOOL REQUIRED: - Guide Pin J 25025-5 ASSEMBLE 1. Guide pin J 25025-5 into valve body. Located at back bolt hole of detent spring and roller assembly bolt bole. 2. Gasket (45) valve body to spacer plate. 3. Spacer plate (46). 4. Gasket (47) accumulator housing to spacer plate. 5. Accumulator housing assembly (51) onto valve body assembly (44). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7605 6. Six bolts (53) using (8 mm) socket through accumulator housing into valve body assembly. Torque Sequence And Guide Pin Location NOTE: Start accumulator housing bolts finger tight and work towards opposite end. TIGHTEN - Bolt (53) to 11 Nm (97 lb. in.). 7. Remove guide pin J 25025-5. Fig. 11 Check Ball Location. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7606 Fig. 10 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7607 Torque Sequence, Control Valve And Switch Assembly INSTALL OR CONNECT 1. Install checkballs (54) in proper location into case fluid passages. Use TRANSJEL TM J 36850 or equivalent to hold in place. NOTICE: Do not use any type of grease to retain parts during assembly of this unit. Greases other than the recommended assembly lube will change transmission fluid characteristics and cause undesirable shift conditions and/or filter clogging. - # 2 checkball is used only on RCP RDP, ZJP and ZLP models. 2. PWM solenoid screen (75). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7608 3. Gasket (48) spacer plate to case. 4. Manual valve (319) into valve body. 5. Complete valve body assembly (44) onto case (7). Use 1 25025-5 guide pin set. IMPORTANT - Attach manual valve to detent lever. 6. Transmission fluid pressure switch assembly (40) onto valve body assembly (44). 7. Spring and roller assembly (41) into place. 8. Three wiring clamps (33), fluid indicator stop (43) and lube pipe clamp (38). 9. Twenty-one bolts (35). Using 10 mm socket. 10. Six bolts (76) using 8 mm socket into transmission fluid pressure switch assembly (40). 11. Lube pipe (39) long end into case, short end into valve body. 12. Lube pipe retainer (37) with short bolt (36). TIGHTEN - Bolts (35, 36 and 76) to 11 Nm (97 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7609 Torque Sequence, Control Valve And Switch Assembly NOTICE: Torque valve body bolts in a spiral pattern starting from the center. If bolts are torqued at random, valve bores may be distorted and inhibit valve operation. 13. Attach wiring harness (34) to 5 connectors. - Put large end into case first, pressure switch hook up, 1-2 shift solenoid (purple) and 2-3 shift solenoid (tan), PWM (Pulse Width Modulated) solenoid and PCS (Pressure Control Solenoid). Pan and Filter Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7610 PAN AND FILTER ASSEMBLY Installing Pan And Filter INSTALL OR CONNECT 1. Seal (32) inside of case (7). 2. Filter assembly (31). 3. Bottom pan seal (29). 4. Magnet (30) into bottom pan. 5. Pan (29). 6. Seventeen bolts (27) using 10 mm socket. TIGHTEN - Bolts (27) to 24 Nm (18 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON Torque Converter Clutch Solenoid: Customer Interest A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-023B Date: March, 2002 TECHNICAL Subject: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1999-2000 Cadillac Escalade 1996-2000 Chevrolet Camaro, Corvette 1996-2000 Pontiac Firebird 1996-2000 Chevrolet and GMC Light Duty Truck Models 1996-2000 Oldsmobile Bravada with 4L60-E Automatic Transmission (RPO M30) Built Prior to January 15, 2000 (Julian Date 0015) This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 Transmission/Transaxle). Condition Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated. Diagnosis Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs. The scan tool may show a DTC P1870 set as a history code. A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93° C (200°F). Cause The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply. Important: ^ DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code. ^ When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result. ^ This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle). ^ When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code. ^ When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL). Correction Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 7619 regulator and isolator valves. Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body. ^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears). ^ The torque converter is not blue or overheated. ^ The transmission fluid is not burned or has no burned odor ^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 7620 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON Torque Converter Clutch Solenoid: All Technical Service Bulletins A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-023B Date: March, 2002 TECHNICAL Subject: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1999-2000 Cadillac Escalade 1996-2000 Chevrolet Camaro, Corvette 1996-2000 Pontiac Firebird 1996-2000 Chevrolet and GMC Light Duty Truck Models 1996-2000 Oldsmobile Bravada with 4L60-E Automatic Transmission (RPO M30) Built Prior to January 15, 2000 (Julian Date 0015) This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 Transmission/Transaxle). Condition Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated. Diagnosis Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs. The scan tool may show a DTC P1870 set as a history code. A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93° C (200°F). Cause The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply. Important: ^ DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code. ^ When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result. ^ This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle). ^ When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code. ^ When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL). Correction Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 7626 regulator and isolator valves. Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body. ^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears). ^ The torque converter is not blue or overheated. ^ The transmission fluid is not burned or has no burned odor ^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 7627 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Accumulator, A/T > Component Information > Technical Service Bulletins > A/T - 1-2 Accumulator Piston/Outer Spring Replacement Accumulator: Technical Service Bulletins A/T - 1-2 Accumulator Piston/Outer Spring Replacement File In Section: 7 - Transmission Bulletin No.: 87-71-74 Date: November, 1998 INFORMATION Subject: 1-2 Accumulator Piston and Outer Spring Replacement Models: 1982-96 Buick Roadmaster 1982-96 Cadillac Brougham, Fleetwood, DeVille 1982-86 Chevrolet Caprice 1982-99 Chevrolet Camaro, Corvette 1982-99 Pontiac Firebird with HYDRA-MATIC 4L60, 4L60-E Transmission (RPOs MD8, M30) 1982-99 Chevrolet and GMC C/K, M/L, S/T, G Models 1991-99 Oldsmobile Bravada with HYDRA-MATIC 4L60, 4L60-E Transmission (RPOs MD8, M30) Transmissions built from 1982 through 1999 were built with one of two styles of 1-2 accumulator pistons and outer springs. Important: The 1-2 accumulator pistons and outer springs are not interchangeable. For replacement of the 1-2 accumulator piston and outer spring, remove the 1-2 accumulator assembly and inspect the interior for the presence of either an aluminum or composite (plastic) 1-2 accumulator piston. Design 1 1-2 accumulator assemblies with an aluminum piston and a round wire outer spring, use service package P/N 24204495 (1982-1993) or P/N 24204496 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Accumulator, A/T > Component Information > Technical Service Bulletins > A/T - 1-2 Accumulator Piston/Outer Spring Replacement > Page 7632 (1994-1997). Design 2 1-2 accumulator assemblies with a composite (plastic) piston and an ovate wire outer spring, started May 11, 1998 (Julian Date 131), use service package P/N 24214343 (1998-1999). Notice: Failure to follow the above instructions may result in transmission distress. Parts Information Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Accumulator, A/T > Component Information > Technical Service Bulletins > Page 7633 Accumulator: Service and Repair 1. Drain and remove oil pan, then filter and gasket. 2. Remove retaining bolts. 3. Remove accumulator housing assembly, gaskets and spacer plate. 4. Reverse procedure to install. Fill transmission with proper fluid. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Band Apply Servo, A/T > Component Information > Service and Repair > Turbo Hydra-Matic 4L80-E & 4L80-EHD Band Apply Servo: Service and Repair Turbo Hydra-Matic 4L80-E & 4L80-EHD Front 1. Drain and remove oil pan, then filter and gasket. 2. Remove control valve assembly as described under "Control Valve Assembly, Replace." Fig.12 Front Servo Assembly 3. Remove front servo piston, piston pin, washer, spring retainer and piston spring, Fig. 12. 4. Reverse procedure to install. Rear 1. Drain and remove oil pan, then filter and gasket. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Band Apply Servo, A/T > Component Information > Service and Repair > Turbo Hydra-Matic 4L80-E & 4L80-EHD > Page 7638 Fig. 13 Rear Servo Assembly 2. Remove servo cover to case bolts, servo cover, gasket and retaining clip, Fig. 13. 3. Remove retaining clip, rear servo piston, reverse servo piston seal and accumulator piston. 4. Remove inner and outer piston seals, washer, rear servo spring and retainer. 5. Remove rear band apply pin and rear accumulator spring. 6. Check and measure the apply pin as follows: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Band Apply Servo, A/T > Component Information > Service and Repair > Turbo Hydra-Matic 4L80-E & 4L80-EHD > Page 7639 Fig. 14 Servo Pin Gauge Installation. a. Place gauge pin part No. J-21370-10 in servo bore, Fig. 14. b. Position band apply pin checking tool No. J-38737 or equivalent over the bore with hex nut facing parking pawl linkage. c. Secure with two rear cover bolts, then tighten to specifications. d. Ensure gauge pin moves freely in tool and pin bore. e. Determine correct pin length by torquing to 25 ft. lbs. the nut on gauge. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Band Apply Servo, A/T > Component Information > Service and Repair > Turbo Hydra-Matic 4L80-E & 4L80-EHD > Page 7640 Fig. 15 Band Apply Pin Selection Chart. f. Refer to Fig. 15 for proper pin selection. 7. Reverse procedure to install. Tighten retaining bolts to specifications. 8. Install filter and pan. 9. Fill transmission with proper fluid. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Band Apply Servo, A/T > Component Information > Service and Repair > Turbo Hydra-Matic 4L80-E & 4L80-EHD > Page 7641 Band Apply Servo: Service and Repair Turbo Hydra-Matic 4L60-E 1. Raise and support vehicle. 2. Remove two oil pan bolts from below servo cover. 3. Install servo cover compressor tool No. J-29714 or equivalent on oil pan flange and depress servo cover. 4. Remove servo cover retaining ring. 5. Remove servo cover and seal ring. 6. Remove servo piston and bore-apply pin assembly. 7. Reverse procedure to install. Whenever any servo parts are replaced, apply-pin length must be checked. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Case, A/T > Component Information > Technical Service Bulletins > A/T - Cracked Case Diagnosis Case: Technical Service Bulletins A/T - Cracked Case Diagnosis Bulletin No.: 02-07-30-024B Date: August 18, 2005 INFORMATION Subject: Diagnosis of Cracked or Broken Transmission Case Models: 2006 and Prior Cars and Light Duty Trucks 2006 and Prior HUMMER H2 2006 HUMMER H3 2005-2006 Saab 9-7X with 4L60/4L60-E/4L65-E or 4L80-E/4L85-E or Allison(R) Series 1000 Automatic Transmission Supercede: This bulletin is being revised to add models and model years. Please discard Corporate Bulletin Number 02-07-30-024A (Section 07 - Transmission/Transaxle). Diagnosing the cause of a cracked or broken transmission case requires additional diagnosis and repair or a repeat failure will occur. A cracked or broken transmission case is most often the result of abnormal external torsional forces acting on the transmission case. If none of the conditions listed below are apparent, an internal transmission component inspection may be required. Repairs of this type may be the result of external damage or abuse for which General Motors is not responsible. They are not the result of defects in materials or workmanship. If in doubt, contact your General Motors Service Representative. The following items should be considered: ^ It is important to inspect the vehicle for signs of an out of line condition, impact damage or foreign material to the following components: - The transmission - The engine mounts - The transmission rear mount and crossmember - Vehicle frame damage that alters the front to rear alignment of the driveshaft - The driveshafts (both front and rear) - The wheels (caked with mud, concrete, etc.) - The tires (roundness, lack of cupping, excessive balance weights) - The transfer case (if the vehicle is 4WD) ^ A worn or damaged driveshaft U-Joint has shown to be a frequent cause of transmission case cracking, especially on vehicles that see extended periods of highway driving. Always inspect the U-joint condition when diagnosing this condition. ^ For driveshaft damage or imbalance, Inspect the driveshafts (both front and rear) for dents, straightness/runout or signs of missing balance weights. Also, inspect for foreign material such as undercoat sprayed on the driveshaft. ^ The driveshaft working angles may be excessive or non-canceling, especially if the vehicle carrying height has been altered (lifted or lowered) or if the frame has been extended or modified. ^ Damaged or worn upper or lower rear control arms or bushings. ^ A rear axle that is not seated in the rear spring properly (leaf spring vehicles). ^ Broken rear springs and or worn leaf spring bushings. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Case, A/T > Component Information > Technical Service Bulletins > A/T - Cracked Case Diagnosis > Page 7646 In some cases, the customer may not comment about a vibration but it is important to test drive the vehicle while using the electronic vibration analysis tool in an attempt to locate the cause of the torsional vibration. Refer to the Vibration Diagnosis and Correction sub-section of the appropriate Service Manual for more details on diagnosing and correcting vibrations. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Channel Plate, A/T > Component Information > Technical Service Bulletins > A/T Control - DTC P0756 Diagnostic Tips Channel Plate: Technical Service Bulletins A/T Control - DTC P0756 Diagnostic Tips INFORMATION Bulletin No.: 01-07-30-036H Date: January 29, 2009 Subject: Diagnostic Tips for Automatic Transmission DTC P0756, Second, Third, Fourth Gear Start Models: 2009 and Prior GM Passenger Cars and Light Duty Trucks 2009 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X with 4L60-E, 4L65-E or 4L70E Automatic Transmission (RPOs M30, M32 or M70) Supercede: This bulletin is being revised to add the 2009 model year and add details regarding spacer plates. Please discard Corporate Bulletin Number 01-07-30-036G (Section 07 - Transmission/Transaxle). Some dealership technicians may have difficulty diagnosing DTC P0756, 2-3 Shift Valve Performance on 4L60-E, 4L65-E or 4L70E automatic transmissions. As detailed in the Service Manual, when the PCM detects a 4-3-3-4 shift pattern, DTC P0756 will set. Some customers may also describe a condition of a second, third or fourth gear start that may have the same causes but has not set this DTC yet. Below are some tips when diagnosing this DTC: ^ This is a performance code. This means that a mechanical malfunction exists. ^ This code is not set by electrical issues such as a damaged wiring harness or poor electrical connections. Electrical problems would cause a DTC P0758, P0787 or P0788 to set. ^ The most likely cause is chips/debris plugging the filtered AFL oil at orifice # 29 on the top of the spacer plate (48). This is a very small hole and is easily plugged by a small amount of debris. It is important to remove the spacer plate and inspect orifice # 29 and the immediate area for the presence of chips/debris. Also, the transmission case passage directly above this orifice and the valve body passage directly below should be inspected and cleaned of any chips/debris. For 2003 and newer vehicles the spacer plate should be replaced. The service replacement spacer plate is a bonded style with gaskets and solenoid filter screens bonded to the spacer plate. These screens can help to prevent plugging of orifice # 29 caused by small debris or chips. ^ This code could be set if the 2-3 shift valve (368) were stuck or hung-up in its bore. Inspect the 2-3 shift valve (368) and the 2-3 shuttle valve (369) for free movement or damage and clean the valves, the bore and the valve body passages. ^ This code could be set by a 2-3 shift solenoid (367b) if it were cracked, broken or leaking. Refer to Shift Solenoid Leak Test in the appropriate Service Manual for the leak test procedure. Based on parts return findings, a damaged or leaking shift solenoid is the least likely cause of this condition. Simply replacing a shift solenoid will not correct this condition unless the solenoid has been found to be cracked, broken or leaking. It is important to also refer to the appropriate Service Manual or Service Information (SI) for further possible causes of this condition. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Clutch, A/T > Component Information > Technical Service Bulletins > Customer Interest for Clutch: > 08-07-30-027 > Jun > 08 > A/T - No Movement in Drive or 3rd Gear Clutch: Customer Interest A/T - No Movement in Drive or 3rd Gear TECHNICAL Bulletin No.: 08-07-30-027 Date: June 04, 2008 Subject: No Movement When Transmission is Shifted to Drive or Third - Normal Operation When Shifted to Second, First or Reverse (Replace Forward Sprag Assembly) Models: 1982 - 2005 GM Passenger Cars and Light Duty Trucks 2006 - 2007 Buick Rainier 2006 Cadillac Escalade, Escalade ESV, Escalade EXT 2006 Chevrolet SSR 2006 - 2008 Chevrolet Avalanche, Colorado, Express, Silverado Classic, Silverado, Suburban, Tahoe, TrailBlazer 2006 GMC Yukon Denali, Yukon Denali XL 2006 - 2008 GMC Canyon, Envoy, Savana, Sierra Classic, Sierra, Yukon, Yukon XL 2006 Pontiac GTO 2006 - 2007 HUMMER H2 2006 - 2008 HUMMER H3 2006 - 2008 Saab 9-7X with 4L60, 4L60E, 4L65E or 4L70E Automatic Transmission (RPOs MD8, M30, M32, M33 or M70) Condition Some customers may comment that the vehicle has no movement when the transmission is shifted to DRIVE or THIRD position, but there is normal operation when it is shifted to SECOND, FIRST or REVERSE position. Cause This condition may be caused by a damaged forward sprag assembly (642). Correction When inspecting the sprag, it is important to test the sprag for proper operation by holding the outer race (644) with one hand while rotating the input sun gear (640) with the other hand. The sun gear should rotate only in the counterclockwise direction with the input sun gear facing upward. If the sprag rotates in both directions or will not rotate in either direction, the sprag elements should be inspected by removing one of the sprag assembly retaining rings (643). Refer to SI Unit Repair section for forward clutch sprag disassembly procedures. If the sprag is found to be damaged, make repairs to the transmission as necessary. A new forward roller clutch sprag assembly is now available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Clutch, A/T > Component Information > Technical Service Bulletins > Customer Interest for Clutch: > 08-07-30-027 > Jun > 08 > A/T - No Movement in Drive or 3rd Gear > Page 7659 If clutch debris is found, it is also very important to inspect the Pressure Control (PC) solenoid valve (377) fluid screens. Clean or replace the PC solenoid (377) as necessary. It is also important to flush and flow check the transmission oil cooler using J45096. Refer to SI Automatic Transmission Oil Cooler Flushing and Flow Test for the procedure. The notches above each sprag must point up as shown when assembled into the outer race. Bearing Assembly, Input Sun Gear Snap Ring, Overrun Clutch Hub Retaining Hub, Overrun Clutch Wear Plate, Sprag Assembly Retainer and Race Assembly, Sprag Forward Sprag Assembly Retainer Rings, Sprag Assembly Outer Race, Forward Clutch Washer, Thrust (Input Carrier to Race) The following information applies when this sprag is used in 1982-86 transmissions. The new design sprag can be used on models 1982 through 1986, by replacing the entire assembly (637 - 644). Individual components are NOT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Clutch, A/T > Component Information > Technical Service Bulletins > Customer Interest for Clutch: > 08-07-30-027 > Jun > 08 > A/T - No Movement in Drive or 3rd Gear > Page 7660 interchangeable. Important: The wear plate (640) and input thrust washer (660) are not required with the new sprag. Use of the thrust washer and wear plate with the new sprag assembly will cause a misbuild (correct end play cannot be obtained). Parts Information Warranty Information For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Clutch, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Clutch: > 08-07-30-027 > Jun > 08 > A/T - No Movement in Drive or 3rd Gear Clutch: All Technical Service Bulletins A/T - No Movement in Drive or 3rd Gear TECHNICAL Bulletin No.: 08-07-30-027 Date: June 04, 2008 Subject: No Movement When Transmission is Shifted to Drive or Third - Normal Operation When Shifted to Second, First or Reverse (Replace Forward Sprag Assembly) Models: 1982 - 2005 GM Passenger Cars and Light Duty Trucks 2006 - 2007 Buick Rainier 2006 Cadillac Escalade, Escalade ESV, Escalade EXT 2006 Chevrolet SSR 2006 - 2008 Chevrolet Avalanche, Colorado, Express, Silverado Classic, Silverado, Suburban, Tahoe, TrailBlazer 2006 GMC Yukon Denali, Yukon Denali XL 2006 - 2008 GMC Canyon, Envoy, Savana, Sierra Classic, Sierra, Yukon, Yukon XL 2006 Pontiac GTO 2006 - 2007 HUMMER H2 2006 - 2008 HUMMER H3 2006 - 2008 Saab 9-7X with 4L60, 4L60E, 4L65E or 4L70E Automatic Transmission (RPOs MD8, M30, M32, M33 or M70) Condition Some customers may comment that the vehicle has no movement when the transmission is shifted to DRIVE or THIRD position, but there is normal operation when it is shifted to SECOND, FIRST or REVERSE position. Cause This condition may be caused by a damaged forward sprag assembly (642). Correction When inspecting the sprag, it is important to test the sprag for proper operation by holding the outer race (644) with one hand while rotating the input sun gear (640) with the other hand. The sun gear should rotate only in the counterclockwise direction with the input sun gear facing upward. If the sprag rotates in both directions or will not rotate in either direction, the sprag elements should be inspected by removing one of the sprag assembly retaining rings (643). Refer to SI Unit Repair section for forward clutch sprag disassembly procedures. If the sprag is found to be damaged, make repairs to the transmission as necessary. A new forward roller clutch sprag assembly is now available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Clutch, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Clutch: > 08-07-30-027 > Jun > 08 > A/T - No Movement in Drive or 3rd Gear > Page 7666 If clutch debris is found, it is also very important to inspect the Pressure Control (PC) solenoid valve (377) fluid screens. Clean or replace the PC solenoid (377) as necessary. It is also important to flush and flow check the transmission oil cooler using J45096. Refer to SI Automatic Transmission Oil Cooler Flushing and Flow Test for the procedure. The notches above each sprag must point up as shown when assembled into the outer race. Bearing Assembly, Input Sun Gear Snap Ring, Overrun Clutch Hub Retaining Hub, Overrun Clutch Wear Plate, Sprag Assembly Retainer and Race Assembly, Sprag Forward Sprag Assembly Retainer Rings, Sprag Assembly Outer Race, Forward Clutch Washer, Thrust (Input Carrier to Race) The following information applies when this sprag is used in 1982-86 transmissions. The new design sprag can be used on models 1982 through 1986, by replacing the entire assembly (637 - 644). Individual components are NOT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Clutch, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Clutch: > 08-07-30-027 > Jun > 08 > A/T - No Movement in Drive or 3rd Gear > Page 7667 interchangeable. Important: The wear plate (640) and input thrust washer (660) are not required with the new sprag. Use of the thrust washer and wear plate with the new sprag assembly will cause a misbuild (correct end play cannot be obtained). Parts Information Warranty Information For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Control Module, A/T > Component Information > Technical Service Bulletins > Customer Interest for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder Control Module: Customer Interest A/T - Upshift Flare/No 3rd or 4th/Launch Shudder File In Section: 07 - Transmission/Transaxle Bulletin No.: 00-07-30-026 Date: December 2000 TECHNICAL Subject: Automatic Transmission 1-2 and/or 2-3 Upshift Slip/Flare, No 3rd or 4th gear, Launch Shudder (Revise VCM Wiring) Models: 1996 Chevrolet and GMC C/K, S/T, M/L, G1, G2, P3 Models 1996 Oldsmobile Bravada with VCM and 4L60-E (M30) or 4L80-E (MT1) Automatic Transmission This bulletin is being reissued to ensure that correct procedures are followed for this condition. Please discard Corporate Bulletin Number 66-71-03A (Section 7 - Automatic Transmission). When performing a transmission replacement labor operation K7000 on these vehicles with a 4L60-E or 4L80-E, you must include front chassis wire repair labor operation N6112. Inspect the VCM to verify the latest part number revision (16244210). Condition Some owners may comment that the automatic transmission has either a slip or flare on the 1-2 and/or 2-3 upshift, or no 3rd or 4th gear, or launch shudder. Upon investigation, the technician may find a DTC P1870 stored in the VCM. Cause A poor internal ground between the two circuit boards of the VCM may cause the VCM to command erratic line pressure at the pressure control (PC) solenoid valve. Correction Using harness jumper wire and instruction kit, P/N 12167310, revise the wiring harness at the VCM connector. Corrections were made to the VCM beginning 2/14/96. The corrected VCMs are identified with service number 16244210 on the VCM identification label. Procedure The following is a summary of the instructions included with the service kit: 1. Remove the negative terminal from the battery. 2. Move the wire located at connector J3 (WHITE/GREY/CLEAR), pin 18 to connector J1 (BLUE), pin 23. 3. Install the jumper wire between connector J2 (RED), pin 26 and connector J3 (WHITE/GREY/CLEAR), pin 18. 4. Install the tag included in the kit around the. VCM wiring harness. This tag notes that the wiring harness has been modified. 5. Reconnect the negative battery terminal. Road test to verify that the condition has been corrected. If any of the following conditions are noted, the transmission should be repaired or replaced using the most cost effective method. Canadian dealers should repair the transmission. ^ Transmission fluid oxidation or excessive sediment. ^ Transmission slip or flare after this service fix is performed. ^ DTC P1870 is stored on a 4L60-E (M30). The following tools are available from Kent-Moore (1-800-345-2233) for use in removing and relocating the VCM wires: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Control Module, A/T > Component Information > Technical Service Bulletins > Customer Interest for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder > Page 7676 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Control Module, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder Control Module: All Technical Service Bulletins A/T - Upshift Flare/No 3rd or 4th/Launch Shudder File In Section: 07 - Transmission/Transaxle Bulletin No.: 00-07-30-026 Date: December 2000 TECHNICAL Subject: Automatic Transmission 1-2 and/or 2-3 Upshift Slip/Flare, No 3rd or 4th gear, Launch Shudder (Revise VCM Wiring) Models: 1996 Chevrolet and GMC C/K, S/T, M/L, G1, G2, P3 Models 1996 Oldsmobile Bravada with VCM and 4L60-E (M30) or 4L80-E (MT1) Automatic Transmission This bulletin is being reissued to ensure that correct procedures are followed for this condition. Please discard Corporate Bulletin Number 66-71-03A (Section 7 - Automatic Transmission). When performing a transmission replacement labor operation K7000 on these vehicles with a 4L60-E or 4L80-E, you must include front chassis wire repair labor operation N6112. Inspect the VCM to verify the latest part number revision (16244210). Condition Some owners may comment that the automatic transmission has either a slip or flare on the 1-2 and/or 2-3 upshift, or no 3rd or 4th gear, or launch shudder. Upon investigation, the technician may find a DTC P1870 stored in the VCM. Cause A poor internal ground between the two circuit boards of the VCM may cause the VCM to command erratic line pressure at the pressure control (PC) solenoid valve. Correction Using harness jumper wire and instruction kit, P/N 12167310, revise the wiring harness at the VCM connector. Corrections were made to the VCM beginning 2/14/96. The corrected VCMs are identified with service number 16244210 on the VCM identification label. Procedure The following is a summary of the instructions included with the service kit: 1. Remove the negative terminal from the battery. 2. Move the wire located at connector J3 (WHITE/GREY/CLEAR), pin 18 to connector J1 (BLUE), pin 23. 3. Install the jumper wire between connector J2 (RED), pin 26 and connector J3 (WHITE/GREY/CLEAR), pin 18. 4. Install the tag included in the kit around the. VCM wiring harness. This tag notes that the wiring harness has been modified. 5. Reconnect the negative battery terminal. Road test to verify that the condition has been corrected. If any of the following conditions are noted, the transmission should be repaired or replaced using the most cost effective method. Canadian dealers should repair the transmission. ^ Transmission fluid oxidation or excessive sediment. ^ Transmission slip or flare after this service fix is performed. ^ DTC P1870 is stored on a 4L60-E (M30). The following tools are available from Kent-Moore (1-800-345-2233) for use in removing and relocating the VCM wires: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Control Module, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder > Page 7682 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid - A/T > Component Information > Technical Service Bulletins > A/T - DEXRON(R)-VI Fluid Information Fluid - A/T: Technical Service Bulletins A/T - DEXRON(R)-VI Fluid Information INFORMATION Bulletin No.: 04-07-30-037E Date: April 07, 2011 Subject: Release of DEXRON(R)-VI Automatic Transmission Fluid (ATF) Models: 2008 and Prior GM Passenger Cars and Light Duty Trucks 2003-2008 HUMMER H2 2006-2008 HUMMER H3 2005-2007 Saturn Relay 2005 and Prior Saturn L-Series 2005-2007 Saturn ION 2005-2008 Saturn VUE with 4T45-E 2005-2008 Saab 9-7X Except 2008 and Prior Chevrolet Aveo, Equinox Except 2006 and Prior Chevrolet Epica Except 2007 and Prior Chevrolet Optra Except 2008 and Prior Pontiac Torrent, Vibe, Wave Except 2003-2005 Saturn ION with CVT or AF23 Only Except 1991-2002 Saturn S-Series Except 2008 and Prior Saturn VUE with CVT, AF33 or 5AT (MJ7/MJ8) Transmission Only Except 2008 Saturn Astra Attention: DEXRON(R)-VI Automatic Transmission Fluid (ATF) is the only approved fluid for warranty repairs for General Motors transmissions/transaxles requiring DEXRON(R)-III and/or prior DEXRON(R) transmission fluids. Supercede: This bulletin is being revised to update information. Please discard Corporate Bulletin Number 04-07-30-037D (Section 07 - Transmission/Transaxle). MANUAL TRANSMISSIONS / TRANSFER CASES and POWER STEERING The content of this bulletin does not apply to manual transmissions or transfer cases. Any vehicle that previously required DEXRON(R)-III for a manual transmission or transfer case should now use P/N 88861800. This fluid is labeled Manual Transmission and Transfer Case Fluid. Some manual transmissions and transfer cases require a different fluid. Appropriate references should be checked when servicing any of these components. Power Steering Systems should now use P/N 9985010 labeled Power Steering Fluid. Consult the Parts Catalog, Owner's Manual, or Service Information (SI) for fluid recommendations. Some of our customers and/or General Motors dealerships/Saturn Retailers may have some concerns with DEXRON(R)-VI and DEXRON(R)-III Automatic Transmission Fluid (ATF) and transmission warranty claims. DEXRON(R)-VI is the only approved fluid for warranty repairs for General Motors transmissions/transaxles requiring DEXRON(R)-III and/or prior DEXRON(R) transmission fluids (except as noted above). Please remember that the clean oil reservoirs of the J-45096 - Flushing and Flow Tester machine should be purged of DEXRON(R)-III and filled with DEXRON(R)-VI for testing, flushing or filling General Motors transmissions/transaxles (except as noted above). DEXRON(R)-VI can be used in any proportion in past model vehicles equipped with an automatic transmission/transaxle in place of DEXRON(R)-III (i.e. topping off the fluid in the event of a repair or fluid change). DEXRON(R)-VI is also compatible with any former version of DEXRON(R) for use in automatic transmissions/transaxles. DEXRON(R)-VI ATF General Motors Powertrain has upgraded to DEXRON(R)-VI ATF with the start of 2006 vehicle production. Current and prior automatic transmission models that had used DEXRON(R)-III must now only use DEXRON(R)-VI. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid - A/T > Component Information > Technical Service Bulletins > A/T - DEXRON(R)-VI Fluid Information > Page 7687 All 2006 and future model transmissions that use DEXRON(R)-VI are to be serviced ONLY with DEXRON(R)-VI fluid. DEXRON(R)-VI is an improvement over DEXRON(R)-III in the following areas: * These ATF change intervals remain the same as DEXRON(R)-III for the time being. 2006-2008 Transmission Fill and Cooler Flushing Some new applications of the 6L80 six speed transmission will require the use of the J 45096 Flushing and Flow Tester to accomplish transmission fluid fill. The clean oil reservoir of the machine should be purged of DEXRON(R)-III and filled with DEXRON(R)-VI. Parts Information Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid - A/T > Component Information > Technical Service Bulletins > A/T - DEXRON(R)-VI Fluid Information > Page 7688 Fluid - A/T: Technical Service Bulletins A/T - Water Or Coolant Contamination Information INFORMATION Bulletin No.: 08-07-30-035B Date: November 01, 2010 Subject: Information on Water or Ethylene Glycol in Transmission Fluid Models: 2011 and Prior GM Passenger Cars and Light Duty Trucks with Automatic Transmission Supercede: This bulletin is being revised to update model years. Please discard Corporate Bulletin Number 08-07-30-035A (Section 07 - Transmission/Transaxle). Water or ethylene glycol in automatic transmission fluid (ATF) is harmful to internal transmission components and will have a negative effect on reliability and durability of these parts. Water or ethylene glycol in ATF will also change the friction of the clutches, frequently resulting in shudder during engagement or gear changes, especially during torque converter clutch engagement. Indications of water in the ATF may include: - ATF blowing out of the transmission vent tube. - ATF may appear cloudy or, in cases of extreme contamination, have the appearance of a strawberry milkshake. - Visible water in the oil pan. - A milky white substance inside the pan area. - Spacer plate gaskets that appear to be glued to the valve body face or case. - Spacer plate gaskets that appear to be swollen or wrinkled in areas where they are not compressed. - Rust on internal transmission iron/steel components. If water in the ATF has been found and the source of the water entry has not been identified, or if a leaking in-radiator transmission oil cooler is suspected (with no evidence of cross-contamination in the coolant recovery reservoir), a simple and quick test kit is available that detects the presence of ethylene glycol in ATF. The "Gly-Tek" test kit, available from the Nelco Company, should be obtained and the ATF tested to make an accurate decision on the need for radiator replacement. This can help to prevent customer comebacks if the in-radiator transmission oil cooler is leaking and reduce repair expenses by avoiding radiator replacement if the cooler is not leaking. These test kits can be obtained from: Nelco Company Test kits can be ordered by phone or through the website listed above. Orders are shipped standard delivery time but can be shipped on a next day delivery basis for an extra charge. One test kit will complete 10 individual fluid sample tests. For vehicles repaired under warranty, the cost of the complete test kit plus shipping charges should be divided by 10 and submitted on the warranty claim as a net item. The transmission should be repaired or replaced based on the normal cost comparison procedure. Important If water or coolant is found in the transmission, the following components MUST be replaced. - Replace all of the rubber-type seals. - Replace all of the composition-faced clutch plates and/or bands. - Replace all of the nylon parts. - Replace the torque converter. - Thoroughly clean and rebuild the transmission, using new gaskets and oil filter. Important The following steps must be completed when repairing or replacing. Flush and flow check the transmission oil cooler using J 45096. Refer to Corporate Bulletin Number 02-07-30-052F- Automatic Transmission Oil Cooler Flush and Flow Test Essential Tool J 45096 TransFlow. - Thoroughly inspect the engine cooling system and hoses and clean/repair as necessary. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid - A/T > Component Information > Technical Service Bulletins > A/T - DEXRON(R)-VI Fluid Information > Page 7689 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid - A/T > Component Information > Specifications > Capacity Specifications Fluid - A/T: Capacity Specifications 4L60-E TRANSMISSION Pan removal ............................................................................................... ................................................................................................................. 5.0 qts. Overhaul ............... .............................................................................................................................................................. ...................................... 11.0 qts. 4L80-E TRANSMISSION Pan removal ............................................................................................... ................................................................................................................. 7.7 qts. Overhaul ............... .............................................................................................................................................................. ...................................... 13.5 qts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid - A/T > Component Information > Specifications > Capacity Specifications > Page 7692 Fluid - A/T: Fluid Type Specifications DEXRON-III Automatic Transmission Fluid (or equivalent). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid - A/T > Component Information > Testing and Inspection > Turbo Hydra-Matic 4L60-E Fluid - A/T: Testing and Inspection Turbo Hydra-Matic 4L60-E Fluid level should be checked at every engine oil change. Frequency of change for transmission fluid is dependent on the type of driving conditions in which the vehicle is used. If the transmission is subjected to severe service such as: use in heavy city traffic when the outside temperature regularly reaches 90°F, use in very hilly or mountainous areas, commercial use such as taxi or delivery service, the fluid should be changed every 15,000 miles when using Dexron II and 50,000 miles when using Dexron III or equivalent. Otherwise, change the fluid every 100,000 miles, using Dexron II, III or equivalent automatic transmission fluid. When checking fluid, ensure vehicle is at operating temperature (190°-200°F), which can be obtained by 15 miles of highway-type driving. After transmission fluid is at operating temperature, use the following procedure to check fluid level: 1. Ensure vehicle is on a level surface, then move gear selector to the Park position. 2. Apply parking brake and block wheels, then allow engine to run at idle speed for three minutes with accessories off. 3. Check fluid level, color and condition. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid - A/T > Component Information > Testing and Inspection > Turbo Hydra-Matic 4L60-E > Page 7695 Fluid - A/T: Testing and Inspection Turbo Hydra-Matic 4L80-E & 4L80-EHD Check fluid at regular intervals. Noticing a change in color, odor or fluid level can serve as a warning of possible transmission problems. To check fluid level, bring fluid to operating temperature of 200°F. With vehicle on a level surface, engine idling in park and parking brake applied, the level on the dipstick should be at the Full mark. To bring the fluid level from the Add mark to the Full mark requires one pint of fluid. If additional fluid is required, use only Dexron II automatic transmission fluid. When adding fluid, do not overfill, as foaming and loss of fluid through the vent may occur as the fluid heats up. Also, If fluid level is too low, complete loss of drive may occur especially when cold, which can cause transmission failure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid - A/T > Component Information > Service and Repair > Turbo Hydra-Matic 4L80-E & 4L80-EHD Fluid - A/T: Service and Repair Turbo Hydra-Matic 4L80-E & 4L80-EHD The normal schedule is 30,000 miles for vehicles under 8600 lbs. GVWR OR 24,000 for vehicles over 8600 lbs. GVWR. If vehicle is driven in heavy city traffic where outside temperature regularly reaches 90°F or higher, in hilly or mountain terrain, is used for frequent trailer pulling or is used in taxi, police, delivery or other commercial service, maintenance schedule for drain and refill is 15,000 miles for all vehicles under 8600 lbs. GVWR or 12,000 miles for vehicles over 8600 lbs. GVWR. Change fluid and filter as follows: 1. Raise vehicle and position drain pan under transmission pan. 2. Remove front and side attaching bolts from the oil pan. 3. Loosen rear attaching bolts approximately four turns. 4. Carefully pry transmission pan loose and allow fluid to drain. 5. Remove rear attaching bolts, pan and pan gasket. 6. Drain remaining fluid from pan, then clean pan and gasket surfaces with solvent and dry with compressed air. 7. Remove transmission screen. Remove seal from intake pipe or case bore. 8. Replace screen if applicable, or thoroughly clean screen assembly with solvent and dry with compressed air. 9. Install seal on intake pipe, then install screen assembly. 10. Install gasket on pan, then install pan and tighten to specifications. 11. Lower vehicle and add approximately 9 pts. of Dexron II type transmission fluid through filler tube. 12. Start engine and let run at idle, then with brakes applied move selector lever through each gear range. 13. Place transmission in Park position and check fluid level. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid - A/T > Component Information > Service and Repair > Turbo Hydra-Matic 4L80-E & 4L80-EHD > Page 7698 Fluid - A/T: Service and Repair Turbo Hydra-Matic 4L60-E Changing Fluid 1. Raise and support vehicle. 2. Loosen two bolts attaching right side of transmission support to frame rail. 3. Remove two bolts attaching left side transmission support to frame rail. 4. Using suitable transmission jack, support and slightly raise transmission. 5. Slide transmission support rearward enough to access rear oil pan attaching bolts. 6. Place drain pan under transmission oil pan, loosen pan bolts on front of pan, pry carefully with screwdriver to loosen oil pan, and allow fluid to drain. 7. Remove remaining oil pan bolts, oil pan, and gasket. 8. Drain fluid from pan, then clean pan and dry thoroughly with compressed air. 9. Remove oil filter to valve body bolt, then remove filter and gasket, replace with new filter and gasket. 10. Install new gasket on oil pan, then oil pan and attaching bolts. Tighten attaching bolts to specification. 11. Lower vehicle and add five quarts of automatic transmission fluid through filler tube. 12. With selector lever in Park and parking brake applied, start engine and let idle. Do not race engine. 13. Move selector lever through each gear range, then return lever to park. 14. Check fluid, then add additional fluid to bring level between dimples on dipstick. Adding Fluid to A Dry Transmission 1. Add transmission fluid through filler tube until oil level is between the "ADD" and "HOT" marks on dipstick. 2. Place selector lever in park, depress accelerator to place carburetor on fast idle cam, and move selector lever through each range. Do not race engine. 3. With selector lever in park, engine running at idle (1-3 minutes), and vehicle on level surface, check fluid level and add additional fluid to bring level between dimples on dipstick. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pan, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission Fluid Pan: Service and Repair 4L60-E Automatic Transmission Removal PAN AND FILTER ASSEMBLY Pan, Filter And Seal Removal CLEAN - Exposed ends of bottom pan screws and spray with penetrating oil. REMOVE OR DISCONNECT 1. Screws (76), oil pan (75) and gasket (73). 2. Oil filter (72) and filter seal (71). - Filter seal may be stuck in the pump. INSPECT - Filter (72), open filter by prying the metal crimping away from the top of the filter (black) and pull apart. The filter may contain evidence for root cause diagnosis. Clutch material. - Bronze slivers indicating bushing wear. - Steel particles. Installation PAN AND FILTER ASSEMBLY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pan, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7703 Case, Pan And Filter Assembly INSTALL OR CONNECT 1. Filter seal (71) into the pump. 2. Oil filter (72). 3. Oil pan gasket (73). 4. Chip magnet (74) onto oil pan (75). 5. Oil pan (75) and bolts (76). TIGHTEN - Torque to 12 Nm (9 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pan, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7704 Fluid Pan: Service and Repair 4L80-E Automatic Transmission Removal PAN AND FILTER ASSEMBLY Pan, Filter And Seal Removal REMOVE OR DISCONNECT 1. Drain the transmission fluid Out case extension by rotating transmission to a vertical position. 2. Seventeen bolts (27), using 10 mm socket, drain transmission fluid. 3. Pan (28), seal (29) and magnet (30). IMPORTANT - Seal (29) is reusable. 4. Filter assembly (31). INSPECT - Filter neck seal (32), replace if necessary. Installation PAN AND FILTER ASSEMBLY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pan, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7705 Installing Pan And Filter INSTALL OR CONNECT 1. Seal (32) inside of case (7). 2. Filter assembly (31). 3. Bottom pan seal (29). 4. Magnet (30) into bottom pan. 5. Pan (29). 6. Seventeen bolts (27) using 10 mm socket. TIGHTEN - Bolts (27) to 24 Nm (18 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pump, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 577126B > Apr > 97 > A/T - Transmission Fluid Leak From Pump Body Fluid Pump: Customer Interest A/T - Transmission Fluid Leak From Pump Body File In Section: 7 - Transmission Bulletin No.: 57-71-26B Date: April, 1997 Subject: Transmission Fluid Leak from Pump Body (Replace Bushing) Models: 1995-96 Buick Road master 1995-96 Cadillac Fleetwood 1995-96 Chevrolet Caprice, Camaro, Corvette 1995-96 Pontiac Firebird 1995-96 Chevrolet and GMC Truck C/K, M/L, S/T, G Models 1996 Oldsmobile Bravada with HYDRA-MATIC 4L60-E Transmission (RPO M30) This bulletin is being revised to remove the Warrant Statement under correction to GMC dealers. Please discard Corporate Bulletin number 57-71-26A (Section 7 - Transmission). Condition (Figure 1) Some owners may experience a pump fluid leak. Starting September 11, 1995 (Julian Date 254) all units are built using a revised design body bushing. Cause The pump bushing is spinning or walking out of the body. Correction Replace the pump body bushing using Kent-Moore tool J 41778. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pump, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 577126B > Apr > 97 > A/T - Transmission Fluid Leak From Pump Body > Page 7714 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pump, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 577126B > Apr > 97 > A/T - Transmission Fluid Leak From Pump Body > Page 7715 Removal and Replacement Procedure (Figures 2-5) 1. Remove the front helix retainer (244). 2. Remove the oil seal assembly (243). 3. Remove the pump body bushing (242) using tool J 41778-1. 4. Install new bushing using J 41778-2 as a positive stop and an Arbor Press with J 41778-1. Refer to your service manual for proper pump assembly removal and replacement procedures. Parts Information Part # Description * 24206030 Bushing-Pump Body * This part will service all 4L60 and 4L60-E applications from 1982-1996. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time Use published labor K7121 operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pump, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 677148 > Jul > 96 > A/T - Engagement Delay When Vehicle Unused for 48 Hours Fluid Pump: Customer Interest A/T - Engagement Delay When Vehicle Unused for 48 Hours File In Section: 7 - Transmission Bulletin No.: 67-71-48 Date: July, 1996 Subject: Delayed Engagement (Replace Pump Cover Assembly) Models: 1995-96 Buick Roadmaster 1995-96 Cadillac Fleetwood 1995-96 Chevrolet Caprice, Camaro, Corvette 1995-96 Pontiac Firebird 1995-96 Chevrolet and GMC C/K, M/L, S/T, G Models 1996 Oldsmobile Bravada with HYDRA-MATIC 4L60-E (RPO M30) Important: GMC Truck dealers should NOT utilize this bulletin for in-warranty repairs. If this condition is experienced, a Goodwrench Transmission Assembly should be used. Refer to Bulletin 367106A, Automatic Transmission Service Procedure Changes, published September, 1995 for in-warranty repairs. Out of warranty repairs may utilize this bulletin. Important: Canadian dealers should repair transmissions following established repair practices. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pump, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 677148 > Jul > 96 > A/T - Engagement Delay When Vehicle Unused for 48 Hours > Page 7720 Condition (Figures 1 and 2) Some owners of the above models, with a HYDRA-MATIC 4L60-E transmission (Built before April 29, 1996/Julian Date 6120), may experience some delayed engagement when vehicle is not used for more than 48 hours. Cause Torque converter fluid level low due to fluid drain down. Correction (Figure 3) Replace pump cover assembly with the new TCC signal valve assembly. Parts Information Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pump, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 677148 > Jul > 96 > A/T - Engagement Delay When Vehicle Unused for 48 Hours > Page 7721 Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time K7121 Replace Pump Use published labor Cover Assembly operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pump, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fluid Pump: > 04-07-30-006 > Feb > 04 > A/T - 4L65E, 4L60E, 4L60, 200-4R Oil Pump Spring Fluid Pump: All Technical Service Bulletins A/T - 4L65E, 4L60E, 4L60, 200-4R Oil Pump Spring Bulletin No.: 04-07-30-006 Date: February 11, 2004 INFORMATION Subject: 4L65-E, 4L60-E, 4L60 and 200-4R Automatic Transmission Oil Pump Spring First and Second Design Identification Models: 2004 and Prior Passenger Cars and Light Duty Trucks 2003-2004 HUMMER H2 with 4L65-E, 4L60-E, 4L60 or 200-4R Automatic Transmission The purpose of this bulletin is to identify the oil pump spring usage for the two different pump designs. Manufacturing of the first design oil pump springs ended December 15, 2003. Manufacturing of the second design oil pump spring began December 16, 2003 The first design oil pump springs (206) and (207) DO NOT have any identification markings. The first design springs (206) and (207) use an inner and outer spring, two springs. The second design oil pump spring (245) is identified with tapered ends on the spring (245) as shown above. The second design spring (245) is a single spring. When servicing either (first design or second design) oil pump body, use the new single oil pump spring (245) with tapered ends. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pump, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fluid Pump: > 04-07-30-006 > Feb > 04 > A/T - 4L65E, 4L60E, 4L60, 200-4R Oil Pump Spring > Page 7727 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pump, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fluid Pump: > 577126B > Apr > 97 > A/T - Transmission Fluid Leak From Pump Body Fluid Pump: All Technical Service Bulletins A/T - Transmission Fluid Leak From Pump Body File In Section: 7 - Transmission Bulletin No.: 57-71-26B Date: April, 1997 Subject: Transmission Fluid Leak from Pump Body (Replace Bushing) Models: 1995-96 Buick Road master 1995-96 Cadillac Fleetwood 1995-96 Chevrolet Caprice, Camaro, Corvette 1995-96 Pontiac Firebird 1995-96 Chevrolet and GMC Truck C/K, M/L, S/T, G Models 1996 Oldsmobile Bravada with HYDRA-MATIC 4L60-E Transmission (RPO M30) This bulletin is being revised to remove the Warrant Statement under correction to GMC dealers. Please discard Corporate Bulletin number 57-71-26A (Section 7 - Transmission). Condition (Figure 1) Some owners may experience a pump fluid leak. Starting September 11, 1995 (Julian Date 254) all units are built using a revised design body bushing. Cause The pump bushing is spinning or walking out of the body. Correction Replace the pump body bushing using Kent-Moore tool J 41778. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pump, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fluid Pump: > 577126B > Apr > 97 > A/T - Transmission Fluid Leak From Pump Body > Page 7732 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pump, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fluid Pump: > 577126B > Apr > 97 > A/T - Transmission Fluid Leak From Pump Body > Page 7733 Removal and Replacement Procedure (Figures 2-5) 1. Remove the front helix retainer (244). 2. Remove the oil seal assembly (243). 3. Remove the pump body bushing (242) using tool J 41778-1. 4. Install new bushing using J 41778-2 as a positive stop and an Arbor Press with J 41778-1. Refer to your service manual for proper pump assembly removal and replacement procedures. Parts Information Part # Description * 24206030 Bushing-Pump Body * This part will service all 4L60 and 4L60-E applications from 1982-1996. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time Use published labor K7121 operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pump, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fluid Pump: > 677148 > Jul > 96 > A/T - Engagement Delay When Vehicle Unused for 48 Hours Fluid Pump: All Technical Service Bulletins A/T - Engagement Delay When Vehicle Unused for 48 Hours File In Section: 7 - Transmission Bulletin No.: 67-71-48 Date: July, 1996 Subject: Delayed Engagement (Replace Pump Cover Assembly) Models: 1995-96 Buick Roadmaster 1995-96 Cadillac Fleetwood 1995-96 Chevrolet Caprice, Camaro, Corvette 1995-96 Pontiac Firebird 1995-96 Chevrolet and GMC C/K, M/L, S/T, G Models 1996 Oldsmobile Bravada with HYDRA-MATIC 4L60-E (RPO M30) Important: GMC Truck dealers should NOT utilize this bulletin for in-warranty repairs. If this condition is experienced, a Goodwrench Transmission Assembly should be used. Refer to Bulletin 367106A, Automatic Transmission Service Procedure Changes, published September, 1995 for in-warranty repairs. Out of warranty repairs may utilize this bulletin. Important: Canadian dealers should repair transmissions following established repair practices. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pump, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fluid Pump: > 677148 > Jul > 96 > A/T - Engagement Delay When Vehicle Unused for 48 Hours > Page 7738 Condition (Figures 1 and 2) Some owners of the above models, with a HYDRA-MATIC 4L60-E transmission (Built before April 29, 1996/Julian Date 6120), may experience some delayed engagement when vehicle is not used for more than 48 hours. Cause Torque converter fluid level low due to fluid drain down. Correction (Figure 3) Replace pump cover assembly with the new TCC signal valve assembly. Parts Information Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pump, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fluid Pump: > 677148 > Jul > 96 > A/T - Engagement Delay When Vehicle Unused for 48 Hours > Page 7739 Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time K7121 Replace Pump Use published labor Cover Assembly operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pump, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fluid Pump: > 04-07-30-006 > Feb > 04 > A/T - 4L65E, 4L60E, 4L60, 200-4R Oil Pump Spring Fluid Pump: All Technical Service Bulletins A/T - 4L65E, 4L60E, 4L60, 200-4R Oil Pump Spring Bulletin No.: 04-07-30-006 Date: February 11, 2004 INFORMATION Subject: 4L65-E, 4L60-E, 4L60 and 200-4R Automatic Transmission Oil Pump Spring First and Second Design Identification Models: 2004 and Prior Passenger Cars and Light Duty Trucks 2003-2004 HUMMER H2 with 4L65-E, 4L60-E, 4L60 or 200-4R Automatic Transmission The purpose of this bulletin is to identify the oil pump spring usage for the two different pump designs. Manufacturing of the first design oil pump springs ended December 15, 2003. Manufacturing of the second design oil pump spring began December 16, 2003 The first design oil pump springs (206) and (207) DO NOT have any identification markings. The first design springs (206) and (207) use an inner and outer spring, two springs. The second design oil pump spring (245) is identified with tapered ends on the spring (245) as shown above. The second design spring (245) is a single spring. When servicing either (first design or second design) oil pump body, use the new single oil pump spring (245) with tapered ends. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Fluid Pump, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Fluid Pump: > 04-07-30-006 > Feb > 04 > A/T - 4L65E, 4L60E, 4L60, 200-4R Oil Pump Spring > Page 7745 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Governor, A/T > Component Information > Service and Repair Governor: Service and Repair 1. Raise and support vehicle 2. Remove governor cover from case using extreme care not to damage cover. If cover is damaged, it should be replaced. 3. Remove governor. 4. Reverse procedure to install and check fluid level. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Output Shaft, A/T > Component Information > Technical Service Bulletins > A/T - 2-3 Upshift or 3-2 Downshift Clunk Noise Output Shaft: Technical Service Bulletins A/T - 2-3 Upshift or 3-2 Downshift Clunk Noise INFORMATION Bulletin No.: 01-07-30-042F Date: February 05, 2010 Subject: Information on 2-3 Upshift or 3-2 Downshift Clunk Noise Models: 2010 and Prior GM Passenger Cars and Light Duty Trucks 2010 and Prior HUMMER H2, H3 2005-2009 Saab 9-7X with 4L60-E, 4L65-E or 4L70-E Automatic Transmission (RPOs M30, M32, M70) Supercede: This bulletin is being revised to add the 2010 model year and 4L70E transmission. Please discard Corporate Bulletin Number 01-07-30-042E (Section 07 - Transmission/Transaxle). Important For 2005 model year fullsize utilities and pickups, refer to Corporate Bulletin 05-07-30-012. Some vehicles may exhibit a clunk noise that can be heard on a 2-3 upshift or a 3-2 downshift. During a 2-3 upshift, the 2-4 band is released and the 3-4 clutch is applied. The timing of this shift can cause a momentary torque reversal of the output shaft that results in a clunk noise. This same torque reversal can also occur on a 3-2 downshift when the 3-4 clutch is released and the 2-4 band applied. This condition may be worse on a 4-wheel drive vehicle due to the additional tolerances in the transfer case. This is a normal condition. No repairs should be attempted. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Parking Pawl, A/T > Component Information > Service and Repair Parking Pawl: Service and Repair REMOVAL 1. Drain and remove oil pan, then filter and gasket. Fig. 16 Park Lock Assembly. 2. Remove lever retaining nut, then pin Fig. 16. 3. Remove detent lever and actuator assembly. 4. Remove parking pawl bracket, spring and pawl return spring plug. 5. Remove parking pawl shaft hole plug, retainer, shaft and pawl. 6. Remove manual shift shaft seal assembly and shaft. 7. Remove speed sensors. INSTALLATION 1. Install pawl shaft and parking pawl. 2. Install parking lock pawl plug with Loctite using a 7/16 inch rod. 3. Install retainer, stud and pawl return spring. 4. Install detent lever to actuator assembly. 5. Install actuator assembly over parking pawl. 6. Install manual shaft and seal. 7. Install lever nut on shaft. 8. Install roll pin, then parking lock bracket. Tighten bolts to specifications. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Relays and Modules A/T > Control Module, A/T > Component Information > Technical Service Bulletins > Customer Interest for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder Control Module: Customer Interest A/T - Upshift Flare/No 3rd or 4th/Launch Shudder File In Section: 07 - Transmission/Transaxle Bulletin No.: 00-07-30-026 Date: December 2000 TECHNICAL Subject: Automatic Transmission 1-2 and/or 2-3 Upshift Slip/Flare, No 3rd or 4th gear, Launch Shudder (Revise VCM Wiring) Models: 1996 Chevrolet and GMC C/K, S/T, M/L, G1, G2, P3 Models 1996 Oldsmobile Bravada with VCM and 4L60-E (M30) or 4L80-E (MT1) Automatic Transmission This bulletin is being reissued to ensure that correct procedures are followed for this condition. Please discard Corporate Bulletin Number 66-71-03A (Section 7 - Automatic Transmission). When performing a transmission replacement labor operation K7000 on these vehicles with a 4L60-E or 4L80-E, you must include front chassis wire repair labor operation N6112. Inspect the VCM to verify the latest part number revision (16244210). Condition Some owners may comment that the automatic transmission has either a slip or flare on the 1-2 and/or 2-3 upshift, or no 3rd or 4th gear, or launch shudder. Upon investigation, the technician may find a DTC P1870 stored in the VCM. Cause A poor internal ground between the two circuit boards of the VCM may cause the VCM to command erratic line pressure at the pressure control (PC) solenoid valve. Correction Using harness jumper wire and instruction kit, P/N 12167310, revise the wiring harness at the VCM connector. Corrections were made to the VCM beginning 2/14/96. The corrected VCMs are identified with service number 16244210 on the VCM identification label. Procedure The following is a summary of the instructions included with the service kit: 1. Remove the negative terminal from the battery. 2. Move the wire located at connector J3 (WHITE/GREY/CLEAR), pin 18 to connector J1 (BLUE), pin 23. 3. Install the jumper wire between connector J2 (RED), pin 26 and connector J3 (WHITE/GREY/CLEAR), pin 18. 4. Install the tag included in the kit around the. VCM wiring harness. This tag notes that the wiring harness has been modified. 5. Reconnect the negative battery terminal. Road test to verify that the condition has been corrected. If any of the following conditions are noted, the transmission should be repaired or replaced using the most cost effective method. Canadian dealers should repair the transmission. ^ Transmission fluid oxidation or excessive sediment. ^ Transmission slip or flare after this service fix is performed. ^ DTC P1870 is stored on a 4L60-E (M30). The following tools are available from Kent-Moore (1-800-345-2233) for use in removing and relocating the VCM wires: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Relays and Modules A/T > Control Module, A/T > Component Information > Technical Service Bulletins > Customer Interest for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder > Page 7765 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Relays and Modules A/T > Control Module, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder Control Module: All Technical Service Bulletins A/T - Upshift Flare/No 3rd or 4th/Launch Shudder File In Section: 07 - Transmission/Transaxle Bulletin No.: 00-07-30-026 Date: December 2000 TECHNICAL Subject: Automatic Transmission 1-2 and/or 2-3 Upshift Slip/Flare, No 3rd or 4th gear, Launch Shudder (Revise VCM Wiring) Models: 1996 Chevrolet and GMC C/K, S/T, M/L, G1, G2, P3 Models 1996 Oldsmobile Bravada with VCM and 4L60-E (M30) or 4L80-E (MT1) Automatic Transmission This bulletin is being reissued to ensure that correct procedures are followed for this condition. Please discard Corporate Bulletin Number 66-71-03A (Section 7 - Automatic Transmission). When performing a transmission replacement labor operation K7000 on these vehicles with a 4L60-E or 4L80-E, you must include front chassis wire repair labor operation N6112. Inspect the VCM to verify the latest part number revision (16244210). Condition Some owners may comment that the automatic transmission has either a slip or flare on the 1-2 and/or 2-3 upshift, or no 3rd or 4th gear, or launch shudder. Upon investigation, the technician may find a DTC P1870 stored in the VCM. Cause A poor internal ground between the two circuit boards of the VCM may cause the VCM to command erratic line pressure at the pressure control (PC) solenoid valve. Correction Using harness jumper wire and instruction kit, P/N 12167310, revise the wiring harness at the VCM connector. Corrections were made to the VCM beginning 2/14/96. The corrected VCMs are identified with service number 16244210 on the VCM identification label. Procedure The following is a summary of the instructions included with the service kit: 1. Remove the negative terminal from the battery. 2. Move the wire located at connector J3 (WHITE/GREY/CLEAR), pin 18 to connector J1 (BLUE), pin 23. 3. Install the jumper wire between connector J2 (RED), pin 26 and connector J3 (WHITE/GREY/CLEAR), pin 18. 4. Install the tag included in the kit around the. VCM wiring harness. This tag notes that the wiring harness has been modified. 5. Reconnect the negative battery terminal. Road test to verify that the condition has been corrected. If any of the following conditions are noted, the transmission should be repaired or replaced using the most cost effective method. Canadian dealers should repair the transmission. ^ Transmission fluid oxidation or excessive sediment. ^ Transmission slip or flare after this service fix is performed. ^ DTC P1870 is stored on a 4L60-E (M30). The following tools are available from Kent-Moore (1-800-345-2233) for use in removing and relocating the VCM wires: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Relays and Modules A/T > Control Module, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder > Page 7771 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Seals and Gaskets, A/T > System Information > Service and Repair > Turbo Hydra-Matic 4L60-E Automatic Transaxle Seals and Gaskets: Service and Repair Turbo Hydra-Matic 4L60-E Automatic Transaxle 1. Remove driveshaft, and tunnel strap, if equipped. 2. Using suitable tool, pry out lip oil seal. 3. Coat outer casting of new oil seal with suitable sealer and drive into place with seal installer tool No. J-21426 or equivalent. 4. Install tunnel strap if used, then install driveshaft. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Seals and Gaskets, A/T > System Information > Service and Repair > Turbo Hydra-Matic 4L60-E Automatic Transaxle > Page 7776 Seals and Gaskets: Service and Repair Turbo Hydra-Matic 4L80-E & 4L80-EHD 1. Remove driveshaft, and tunnel strap, as equipped. 2. Using suitable tool, pry out lip oil seal. 3. Coat outer casting of new oil seal with suitable sealer and drive into place with installer tool Nos. J-38694 or J-38869 or equivalents. 4. Install driveshaft. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Technical Service Bulletins > A/T Park/Neutral Switch Connector Cannot Be Removed Transmission Position Switch/Sensor: Technical Service Bulletins A/T - Park/Neutral Switch Connector Cannot Be Removed File In Section: 7 - Transmission Bulletin No.: 83-71-10 Date: May, 1998 Subject: Park (Neutral Position Switch Connector Cannot be Removed (Replace Switch and Connectors) Models: 1997-98 Chevrolet Corvette 1995-98 Chevrolet and GMC S/T Models 1996-98 Chevrolet and GMC M/L, P Models 1996-99 Chevrolet and GMC C/K, G Models 1996-98 Oldsmobile Bravada Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer conditions, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to insure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to insure water-tight connections. Parts Information P/N Description 12450016 Switch 15305925 4-Way Connector Assembly 15305887 7-Way Connector Assembly Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 7784 Transmission Position Switch/Sensor: Locations Park/Neutral Position Switch Electronic 4-Speed Automatic Overdrive Transmission Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 7785 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions Transmission Position Switch/Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7788 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7789 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7790 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7791 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7792 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7793 Transmission Position Switch/Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7794 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7795 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7796 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7797 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7798 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7799 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7800 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7801 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7802 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7803 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7804 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7805 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7806 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7807 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7808 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7809 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7810 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7811 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7812 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7813 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7814 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7815 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7816 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7817 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7818 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7819 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7820 Transmission Position Switch/Sensor: Connector Views C1: Transmission Range Switch C2: Transmission Range Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7821 Transmission Position Switch/Sensor: Electrical Diagrams Electronic PRNDL Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 7822 Starter And Charging (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 7823 Transmission Position Switch/Sensor: Testing and Inspection Pressure Switch Assembly Resistance Check (1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 7824 Pressure Switch Assembly Resistance Check (2 Of 2) Tools Required - J 39775 4L60E Jumper Harness - J 39200 Digital Multimeter - J 35616 Connector Test Adapter Kit Important: Whenever the transmission 20-way connector is disconnected and the engine is running, multiple DTCs will set. Be sure to clear these codes when you are finished with this procedure Important: This procedure tests the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) circuits and the Automatic Transmission Fluid Temperature (TFT) Sensor circuit. Do not use this procedure to test other Automatic Transmission circuits, refer to 4L60-E Automatic Transmission Internal Wiring Harness check. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 7825 Transmission Position Switch/Sensor: Adjustments PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 7826 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 7827 Transmission Position Switch/Sensor: Service and Repair PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 7828 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Speed Sensor, A/T > Component Information > Locations > Transmission Output Speed Sensor, 4L80E Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sensors and Switches A/T > Transmission Speed Sensor, A/T > Component Information > Locations > Transmission Output Speed Sensor, 4L80E > Page 7833 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Interlock, A/T > Shift Interlock Solenoid > Component Information > Locations Shift Interlock Solenoid: Locations RH side of steering column, under Support bracket. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling Shift Solenoid: Customer Interest A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling File In Section: 7 Transmission Bulletin No.: 77-71-77 Date: December, 1997 Subject: Loss of 4th Gear, Slipping in 4th Gear, Busy 3-4 Shifting or TCC Cycling (Replace Shift Solenoids) Models: 1996-97 Chevrolet and GMC C/K, G, P Models with HYDRA-MATIC 4L8OE Transmission (RPO MT1) Condition Some owners may comment about a loss of 4th gear, slipping in 4th gear, busy 3-4 shifting or Torque Converter Clutch (TCC) cycling and no DTC's are setting. Cause Shift solenoid leaking hydraulically. Correction If normal diagnosis does not provide a correction, follow the solenoid test procedure listed. Replace the shift solenoid if it fails the test. Also verify that the transmission cooling system is operating properly. Service Information (figure 1) Starting June 23, 1997 (Julian date 174) all HYDRA-MATIC 4L80-E transmissions are being built with the new solenoid assemblies. The new solenoids will service all 1991 through 1997 4L80-E applications. The above listed conditions occur mainly on high duty cycle applications and/or when the transmission is operated under high temperature conditions. Each solenoid may be tested for leaking using the following test: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling > Page 7846 1. Remove the solenoid from the control valve body. Refer to the Service Manual for the proper procedure. 2. Clamp a piece of 1/2 inch I.D. rubber hose over the fluid inlet end of the solenoid. 3. Connect a wire from one of the solenoid terminals to the negative terminal (ground) of a battery. 4. Apply compressed air to the rubber hose. Do not use air pressure in excess of 120 psi. Excessive pressure will not allow the check ball to seat properly. 5. Connect a wire from the other solenoid to the positive terminal (12 volts) of the battery. 6. Observe the air flow through the solenoid. Replace the solenoid if there is an air leak when the solenoid is energized. Parts Information New Part Number Description 10478140 1-2 & 3-4 Shift Solenoid (black) 10478141 2-3 Shift Solenoid (white) Parts are currently available through GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift Shift Solenoid: Customer Interest A/T - Engine Speed Flare During Part Throttle Downshift File In Section: 7 - Transmission Bulletin No.: 67-71-47 Date: July, 1996 Subject: 3-2 Part Throttle Downshift Flare (Replace 3-2 Solenoid) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1996 Chevrolet Camaro, Caprice, Corvette 1996 Pontiac Firebird 1996 Chevrolet and GMC C/K, M/L, S/T, G Models 1996 Oldsmobile Bravada with HYDRA-MATIC 4L60-E (RPO M30) Condition (Figures 1 and 2) Some owners of the above models with a HYDRA-MATIC 4L60-E transmission (built before May 24, 1996/Julian Date 6145) may experience an engine speed flare of 1000-2000 RPM, during a part throttle downshift at 19-31 mph. This condition will not set any DTC's (Diagnostic Trouble Codes). Cause Exhaust seat on the 3-2 control solenoid backing out. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift > Page 7851 Correction (Figure 3) Replace the 3-2 control solenoid. Julian Date on the solenoid will be May 13, 1996 (6134) or later. Parts Information New Part Number Description 24209121 Solenoid, 3-2 Control Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time K6559 Replace 3-2 Use published labor Control Solenoid operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling Shift Solenoid: All Technical Service Bulletins A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling File In Section: 7 Transmission Bulletin No.: 77-71-77 Date: December, 1997 Subject: Loss of 4th Gear, Slipping in 4th Gear, Busy 3-4 Shifting or TCC Cycling (Replace Shift Solenoids) Models: 1996-97 Chevrolet and GMC C/K, G, P Models with HYDRA-MATIC 4L8OE Transmission (RPO MT1) Condition Some owners may comment about a loss of 4th gear, slipping in 4th gear, busy 3-4 shifting or Torque Converter Clutch (TCC) cycling and no DTC's are setting. Cause Shift solenoid leaking hydraulically. Correction If normal diagnosis does not provide a correction, follow the solenoid test procedure listed. Replace the shift solenoid if it fails the test. Also verify that the transmission cooling system is operating properly. Service Information (figure 1) Starting June 23, 1997 (Julian date 174) all HYDRA-MATIC 4L80-E transmissions are being built with the new solenoid assemblies. The new solenoids will service all 1991 through 1997 4L80-E applications. The above listed conditions occur mainly on high duty cycle applications and/or when the transmission is operated under high temperature conditions. Each solenoid may be tested for leaking using the following test: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling > Page 7857 1. Remove the solenoid from the control valve body. Refer to the Service Manual for the proper procedure. 2. Clamp a piece of 1/2 inch I.D. rubber hose over the fluid inlet end of the solenoid. 3. Connect a wire from one of the solenoid terminals to the negative terminal (ground) of a battery. 4. Apply compressed air to the rubber hose. Do not use air pressure in excess of 120 psi. Excessive pressure will not allow the check ball to seat properly. 5. Connect a wire from the other solenoid to the positive terminal (12 volts) of the battery. 6. Observe the air flow through the solenoid. Replace the solenoid if there is an air leak when the solenoid is energized. Parts Information New Part Number Description 10478140 1-2 & 3-4 Shift Solenoid (black) 10478141 2-3 Shift Solenoid (white) Parts are currently available through GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 377148A > Nov > 96 > A/T - Shift Solenoid Update Shift Solenoid: All Technical Service Bulletins A/T - Shift Solenoid Update File In Section: 7 Transmission Bulletin No.: 37-71-48A Date: November, 1996 INFORMATION Subject: Transmission Product Updates (New Shift Solenoids) Models: 1991-97 Chevrolet and GMC C/K, P, G Models 1991 Chevrolet and GMC R/V Models with HYDRA-MATIC 4L8O-E Transmission (RPO MT1) This bulletin is being revised to update the part numbers and to include 1995-97 model years. Please discard Corporate Bulletin Number 377148 (Section 7 - Transmission). Service Information Starting August 14, 1996 (Julian date 226) all HYDRA-MATIC 4L80-E transmissions are being built with the new solenoid assemblies. The new solenoids are serviced for all 1991 through 1997 4L80-E applications. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 377148A > Nov > 96 > A/T - Shift Solenoid Update > Page 7862 Parts Information Previous Part New Part Description 10478125 10478132 Valve assembly, 1-2 Shift Solenoid (Black) 10478126 10478133 Valve assembly, 2-3 Shift Solenoid (White) Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift Shift Solenoid: All Technical Service Bulletins A/T - Engine Speed Flare During Part Throttle Downshift File In Section: 7 - Transmission Bulletin No.: 67-71-47 Date: July, 1996 Subject: 3-2 Part Throttle Downshift Flare (Replace 3-2 Solenoid) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1996 Chevrolet Camaro, Caprice, Corvette 1996 Pontiac Firebird 1996 Chevrolet and GMC C/K, M/L, S/T, G Models 1996 Oldsmobile Bravada with HYDRA-MATIC 4L60-E (RPO M30) Condition (Figures 1 and 2) Some owners of the above models with a HYDRA-MATIC 4L60-E transmission (built before May 24, 1996/Julian Date 6145) may experience an engine speed flare of 1000-2000 RPM, during a part throttle downshift at 19-31 mph. This condition will not set any DTC's (Diagnostic Trouble Codes). Cause Exhaust seat on the 3-2 control solenoid backing out. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift > Page 7867 Correction (Figure 3) Replace the 3-2 control solenoid. Julian Date on the solenoid will be May 13, 1996 (6134) or later. Parts Information New Part Number Description 24209121 Solenoid, 3-2 Control Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time K6559 Replace 3-2 Use published labor Control Solenoid operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Shift Solenoid: > 66-90-03 > Jun > 97 > Keyless Entry - Unintended Release of Rear Hatch Power Trunk / Liftgate Lock Actuator: All Technical Service Bulletins Keyless Entry - Unintended Release of Rear Hatch File In Section: 9 - Accessories Bulletin No.: 66-90-03 Date: June, 1997 Subject: Unintended Release of Rear Hatch (Replace Transmitter Cover) Models: 1994-96 Chevrolet and GMC C/K, S/T, M/L, G Models 1994 Oldsmobile Bravada 1996 Oldsmobile Bravada Condition An owner may report that the Rear Hatch Releases without their being aware of it. Cause The Keyless Entry Transmitter Button is unintentionally bumped activating the hatch release. Correction Replace the Keyless Entry Transmitter Cover. The revised cover has a deeper recess around the release button making it less prone to inadvertent bumping. Parts Information P/N Description Qty 15740707 Bezel, Transmitter Cover 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time R4490 Control Assembly 0.3 hr Cover - Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Specifications > 4L60-E Automatic Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Specifications > 4L60-E Automatic Transmission > Page 7880 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Locations > 4L60-E Automatic Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Locations > 4L60-E Automatic Transmission > Page 7883 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission Shift Solenoid: Service and Repair 4L60-E Automatic Transmission Pan and Filter Assembly PAN AND FILTER ASSEMBLY Pan, Filter And Seal Removal CLEAN - Exposed ends of bottom pan screws and spray with penetrating oil. REMOVE OR DISCONNECT 1. Screws (76), oil pan (75) and gasket (73). 2. Oil filter (72) and filter seal (71). - Filter seal may be stuck in the pump. INSPECT - Filter (72), open filter by prying the metal crimping away from the top of the filter (black) and pull apart. The filter may contain evidence for root cause diagnosis. Clutch material. - Bronze slivers indicating bushing wear. - Steel particles. Valve Body and Wiring Harness VALVE BODY AND WIRING HARNESS Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7886 Valve Body Bolt Location Control Valve And Pressure Switch Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7887 Manual Valve Link Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7888 Valve Body Checkballs Case Checkballs And Filters REMOVE OR DISCONNECT 1. Electrical connections from components. 2. TCC PWM Solenoid Retainer Clip (379) and Solenoid (396). 3. TCC Solenoid bolts (68) and solenoid assembly (66) with O-ring seal (65) and wiring harness. 4. Pressure switch assembly bolts (70) and pressure switch assembly (69). 5. Accumulator cover bolts (58 and 59) and 1-2 accumulator cover and pin assembly (57). 6. 1-2 accumulator piston (56) and seal (55). 7. Spring (54). 8. Dipstick stop bracket (93). REMOVE OR DISCONNECT 1. Bolt (64) and manual detent spring assembly (63). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7889 2. Wiring harness retaining bolts. REMOVE OR DISCONNECT 1. Remaining valve body bolts (62). 2. Manual valve link (89). 3. Control valve assembly (60). 4. Bolts (58 and 59), accumulator cover (57), piston (56, spring (54) and spring (54A). 5. Bolts (77) and plate (53). 6. Spacer plate (48) and spacer plate gaskets (47 and 52). 7. Spring (46), piston (44), and pin (43). - Seven checkballs are located under the valve body and one is located in the case. The large copper flash colored ball is # 1A checkball (91). Valve Body and Associated Parts VALVE BODY AND ASSOCIATED PARTS Accumulator Assembly, Spacer Plate And Gaskets Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7890 Case Checkballs And Filters TOOL REQUIRED: - J 25025-5 Guide Pins NOTICE: The use of a honing stone, fine sandpaper or crocus cloth is not recommended for servicing stuck valves. All valve lands have sharply machined corners that are necessary for "cleaning" the bore. If these corners are rounded, foreign material could wedge between the valve and bore causing the valve to stick. If it is found necessary to clean a valve, "micro fine" lapping compound 900 grit or finer should be used. Too much "lapping" of a valve will cause excessive clearances and increase the chance of a valve not operating. INSTALL OR CONNECT 1. The wiring harness pass-thru connector into the case. 2. The 3-4 accumulator pin (43) into the case. 3. The 3-4 accumulator piston seal (45) onto the 3-4 accumulator piston. 4. The 3-4 accumulator piston (44) onto the pin. - The end with three legs must face the valve body. 5. The 3-4 accumulator piston spring (46). INSTALL OR CONNECT 1. Checkball (91) into case as shown. - Retain with Transjel TM J 36850 or equivalent. 2. J 25025-5 into the case. 3. Screens onto spacer plate as shown. 4. Spacer plate to case gasket (47) and spacer plate to valve body gasket (52) onto the spacer plate (48). - Gasket (47) identified by a "C". Gasket (52) identified by a "V". - Retain with Transjel TM J 36850 or equivalent. 5. Spacer plate and gaskets onto the case. IMPORTANT - Be careful not to damage screens when installing the spacer plate and gaskets. 6. Spacer plate support (53) and bolts (77). TIGHTEN - Bolts to 11 Nm (8 lb. ft.) Control Valve Body CONTROL VALVE BODY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7891 Case Checkballs And Filters Filter Screen - Locations Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7892 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7893 Control Valve Assembly - Legend Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7894 Valve Body Checkball Locations Valve Body Bolt Locations Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7895 Manual Valve Link Outside Electrical Connector CLEAN - Control valve assembly thoroughly in clean solvent. A. Move the valves with a pick or small screwdriver to dislodge any dirt or debris that may have accumulated. B. Air dry. REMOVE OR DISCONNECT IMPORTANT - Some valves are under pressure - cover the bores while removing roll pins and retainer clips. - Valves, springs and bushings must be laid out on a clean surface in the exact sequence they are removed. 1. Pressure control solenoid retainer bolt (364) retainer (378) and solenoid. 2. Bore plug retainer clip (395), bore plug (376) and valve train (374 and 375). 3. 2-3 shift solenoid retainer (379), solenoid (367) and valve train (368 and 369). 4. 1-2 shift solenoid retainer (379), solenoid (367) and valve train (365 and 366). 5. Accumulator valve train retainer pin (360), bore plug (373) and valve train (370 and 371). 6. Forward accumulator cover bolts (364) and cover (363). 7. Forward accumulator spring (356), piston (354) and pin (355). 8. Lo overrun valve spring (362) and valve (361). 9. Retainer pin (360), bore plug (359) and forward abuse valve train (357 and 358). 10. Manual valve (340). 11. 3-2 control solenoid retainer clip (379) and solenoid (394). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7896 12. Bore plug retainer (395), bore plug (381) and 3-2 control valve train (391 - 393). 13. 3-2 downshift bore plug retainer (395), bore plug (381) and valve train (389 - 390). 14. Reverse abuse bore plug retainer pin (360), bore plug (359) and valve train (387 - 388). 15. 3-4 shift valve bore plug retainer (395), bore plug (381) and valve train (385 - 386). 16. 3-4 relay bore plug retainer (395), bore plug (381) and valve train (382 - 384). 17. Torque converter clutch signal valve bore plug retainer (395), bore plug (381) and valve (380). CLEAN - All valves, springs, bushings and control valve body in clean solvent. - Dry using compressed air. INSPECT - All valves and bushings for: Porosity - Scoring - Nicks - Scratches - Springs for damaged or distorted coils. - Valve body casting for: Porosity - Cracks - Inter connected oil passages - Damaged machined surfaces ASSEMBLE - Control valve assembly (350) exactly as shown. Notice the position of the valve lands and bushing passages. - Position the pressure control solenoid so the connector tabs face outward. NOTICE: TCC PWM solenoid (396) cannot be installed until TCC solenoid has been installed and torqued to proper specifications. INSTALL OR CONNECT 1. Checkballs into the valve body assembly (350). - Retain with Transjell TM J 36850 or equivalent. 2. Valve body assembly (350). - Connect the manual valve link (89) to the inside detent lever (88). - Be careful not to damage screens when installing the valve body assembly. 3. Wiring harness (66), manual spring assembly (63), pressure switch assembly(69), dipstick, stop bracket (93) and all remaining valve body bolts. NOTICE: Torque valve body bolts in a spiral pattern starting from the center. If bolts are torqued at random, valve bores may be distorted and inhibit valve operation. 4. TCC solenoid (66) and bolts (68). TIGHTEN - Bolts to 11 Nm (8 lb. ft.). 5. TCC PWM solenoid (396), and retainer clip (379). INSTALL OR CONNECT - Wiring harness connections to electrical components. - To correctly hook up the wires, see the wiring diagrams. - The pressure control solenoid (377) has two different colored connectors. The black connector should be installed on the tab farthest from the valve body. INSTALL OR CONNECT 1. Parking bracket (86). TIGHTEN - Bolts to 31 Nm (23 lb. ft.). 2. The 1-2 accumulator piston seal (55) onto the 1-2 accumulator piston (56). 3. The 1-2 accumulator spring (54) and 1-2 accumulator inner spring (54A) onto the piston (56). 4. The 1-2 accumulator piston (56) into the 1-2 accumulator cover and pin assembly (57). - The three legs on the piston must face away from the case when installed. 5. The 1-2 accumulator cover and pin assembly (57) onto the case. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7897 TIGHTEN - Torque to 11 Nm (8 lb. ft.). Pan and Filter Assembly PAN AND FILTER ASSEMBLY Case, Pan And Filter Assembly INSTALL OR CONNECT 1. Filter seal (71) into the pump. 2. Oil filter (72). 3. Oil pan gasket (73). 4. Chip magnet (74) onto oil pan (75). 5. Oil pan (75) and bolts (76). TIGHTEN - Torque to 12 Nm (9 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7898 Shift Solenoid: Service and Repair 4L80-E Automatic Transmission Pan and Filter Assembly PAN AND FILTER ASSEMBLY Pan, Filter And Seal Removal REMOVE OR DISCONNECT 1. Drain the transmission fluid Out case extension by rotating transmission to a vertical position. 2. Seventeen bolts (27), using 10 mm socket, drain transmission fluid. 3. Pan (28), seal (29) and magnet (30). IMPORTANT - Seal (29) is reusable. 4. Filter assembly (31). INSPECT - Filter neck seal (32), replace if necessary. Wire Harness Assembly WIRE HARNESS ASSEMBLY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7899 Pan, Filter And Seal Removal REMOVE OR DISCONNECT 1. Wire harness connectors from electrical components. NOTICE: Excessive force on the case pass through connector may damage the connector. IMPORTANT - If the wire harness assembly does not need servicing, it is not necessary to remove it from the case. 2. Wire harness assembly (34) from case using a 1-5/16" 12 point socket to release the connector retaining clips. Control Valve Assembly CONTROL VALVE ASSEMBLY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7900 REMOVE OR DISCONNECT 1. Rotate transmission bottom pan surface up and lock in place. 2. Wire harness assembly (34) connectors from components. IMPORTANT - If the wire harness assembly does not need servicing, it is not necessary to remove it from the case. - Use a cap to cover electrical pin at case connection. 3. Six bolts (76) using 8 mm socket, and transmission fluid pressure switch assembly (40). NOTICE: Be sure five O-rings are attached to transmission fluid pressure switch assembly. 4. Twenty-one bolts (35) using 10 mm socket, from valve body assembly, manual detent spring and roller assembly (41). 5. Three wiring clamps (33), fluid level indicator stop (43), one bolt (36) using 10 mm socket, lube pipe (39), lube pipe retainer (37) and clamp (38). 6. Control valve assembly (44) including the accumulator housing assembly (51), valve body gaskets (45 and 48), spacer plate (46) and accumulator gasket (47). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7901 7. Manual valve (319) from control valve assembly (44) to prevent any damage. 8. Checkballs (54) from case passages. NOTICE: Do not use a magnet. It could cause checkball(s) to be magnetized causing metal particles to stick to the ball. 9. Pulse Width Modulated (PWM) solenoid screen (75). INSPECT - Screen PWM solenoid (75), replace if necessary. DISASSEMBLE Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7902 - Control valve assembly. A. Position as shown on a clean surface. B. Remove blind hole retainer pins with a drill bit. CAUTION: Some valves are under pressure - cover the bores while removing the retaining pins or personal injury could result. C. Remove valve trains, shift solenoids (311 and 313), PCS (320), PWM solenoid (323), PCS screen (302) and shift solenoid filter (317). D. Valves, springs, bushings and pistons must be laid out on a clean surface. CLEAN - All valves, springs, bushings, pistons, control valve body and accumulator housing in clean solvent. - Dry using compressed air. INSPECT 1. All valves, pistons and bushings for: - Porosity. - Scoring. - Nicks. - Scratches. 2. Pistons for: - Seal damage. 3. Springs for: - Damaged or distorted coils. 4. Valve body casting and accumulator housing for: - Porosity. - Cracks. - Interconnected passages. - Damaged machined surfaces. 5. Solenoid connectors and filter (317). 6. PCS (Pressure Control Solenoid) screen (302). Control Valve Assembly/Accumulator Housing CONTROL VALVE ASSEMBLY/ACCUMULATOR HOUSING Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7903 Control Valve Assembly/Accumulator Housing Accumulator Housing Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7904 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7905 Torque Sequence And Guide Pin Location Fig. 11 Check Ball Location. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7906 Fig. 10 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7907 Torque Sequence, Control Valve And Switch Assembly NOTICE: The use of a honing stone, fine sandpaper or crocus cloth is not recommended for servicing stuck valves. All valve lands have sharply machined comers that are necessary for cleaning the bore. If these corners are rounded, foreign material could wedge between the valve and the bore causing the valve to stick. If it is found necessary to clean a valve, micro fine lapping compound 900 grit (J 38459) or finer should be used. Too much lapping of the valve will cause excessive clearances and increase the chance of a valve not operating. CLEAN - Control valve assembly and accumulator housing (51) thoroughly in clean solvent. - Air dry. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7908 Accumulator Housing Assembly ACCUMULATOR HOUSING ASSEMBLY Control Valve Assembly/Accumulator Housing Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7909 Accumulator Housing Assembly DISASSEMBLE 1. Six bolts (53), using 8 mm socket. 2. Accumulator housing assembly. 3. Gasket accumulator housing (47). 4. Spacer plate (46). 5. Gasket (45) valve body spacer. 6. Snap ring (402) from outside housing, pin (408), snap ring (402), piston (407) and spring (49). 7. 3rd clutch piston (405) and spring (50). 8. Seals (404 and 406). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7910 CLEAN - All components. INSPECT - All valves, pistons, springs and seals for: - Porosity. - Scoring. - Nicks. - Scratches. Accumulator Housing Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7911 ASSEMBLE - Accumulator housing assembly components exactly as shown. Notice the positions of the pistons. Control Valve Assembly CONTROL VALVE ASSEMBLY Control Valve Assembly ASSEMBLE - Control valve assembly components exactly as shown. Notice the position of the valve lands and bushing passages. Control Valve Assembly/Accumulator Housing Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7912 CONTROL VALVE ASSEMBLY AND ACCUMULATOR HOUSING Control Valve Assembly/Accumulator Housing Torque Sequence And Guide Pin Location TOOL REQUIRED: - Guide Pin J 25025-5 ASSEMBLE 1. Guide pin J 25025-5 into valve body. Located at back bolt hole of detent spring and roller assembly bolt bole. 2. Gasket (45) valve body to spacer plate. 3. Spacer plate (46). 4. Gasket (47) accumulator housing to spacer plate. 5. Accumulator housing assembly (51) onto valve body assembly (44). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7913 6. Six bolts (53) using (8 mm) socket through accumulator housing into valve body assembly. Torque Sequence And Guide Pin Location NOTE: Start accumulator housing bolts finger tight and work towards opposite end. TIGHTEN - Bolt (53) to 11 Nm (97 lb. in.). 7. Remove guide pin J 25025-5. Fig. 11 Check Ball Location. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7914 Fig. 10 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7915 Torque Sequence, Control Valve And Switch Assembly INSTALL OR CONNECT 1. Install checkballs (54) in proper location into case fluid passages. Use TRANSJEL TM J 36850 or equivalent to hold in place. NOTICE: Do not use any type of grease to retain parts during assembly of this unit. Greases other than the recommended assembly lube will change transmission fluid characteristics and cause undesirable shift conditions and/or filter clogging. - # 2 checkball is used only on RCP RDP, ZJP and ZLP models. 2. PWM solenoid screen (75). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7916 3. Gasket (48) spacer plate to case. 4. Manual valve (319) into valve body. 5. Complete valve body assembly (44) onto case (7). Use 1 25025-5 guide pin set. IMPORTANT - Attach manual valve to detent lever. 6. Transmission fluid pressure switch assembly (40) onto valve body assembly (44). 7. Spring and roller assembly (41) into place. 8. Three wiring clamps (33), fluid indicator stop (43) and lube pipe clamp (38). 9. Twenty-one bolts (35). Using 10 mm socket. 10. Six bolts (76) using 8 mm socket into transmission fluid pressure switch assembly (40). 11. Lube pipe (39) long end into case, short end into valve body. 12. Lube pipe retainer (37) with short bolt (36). TIGHTEN - Bolts (35, 36 and 76) to 11 Nm (97 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7917 Torque Sequence, Control Valve And Switch Assembly NOTICE: Torque valve body bolts in a spiral pattern starting from the center. If bolts are torqued at random, valve bores may be distorted and inhibit valve operation. 13. Attach wiring harness (34) to 5 connectors. - Put large end into case first, pressure switch hook up, 1-2 shift solenoid (purple) and 2-3 shift solenoid (tan), PWM (Pulse Width Modulated) solenoid and PCS (Pressure Control Solenoid). Pan and Filter Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 7918 PAN AND FILTER ASSEMBLY Installing Pan And Filter INSTALL OR CONNECT 1. Seal (32) inside of case (7). 2. Filter assembly (31). 3. Bottom pan seal (29). 4. Magnet (30) into bottom pan. 5. Pan (29). 6. Seventeen bolts (27) using 10 mm socket. TIGHTEN - Bolts (27) to 24 Nm (18 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Linkage, A/T > Shift Cable, A/T > Component Information > Service and Repair > 4L60-E (M30) Transmission Shift Cable: Service and Repair 4L60-E (M30) Transmission REMOVE OR DISCONNECT - Apply the parking brake - Position the steering column shift lever to park. - Raise and support the vehicle. 1. Front seat. 2. Door sill trim plate. 3. Hinge pillar trim panel. 4. Carpet and carpet retainers on the driver's side to expose the shift cable. 5. Steering column filler panel from the steering column. 6. Shift cable from the steering column shift control. - Prior to removing the shift cable from the vehicle, ensure that the transmission is in the mechanical park position. The transmission control lever can be positioned to mechanical park by rotating the control lever clockwise until it reaches its full clockwise stop position. 7. Shift cable from clip and/or tape on floor pan. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Linkage, A/T > Shift Cable, A/T > Component Information > Service and Repair > 4L60-E (M30) Transmission > Page 7924 8. Retaining clip securing the shift cable to the transmission shift cable bracket. - Squeeze the retainers while pulling the cable towards the rear of the vehicle. 9. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 10. Shift cable from under the fuel line and from the rear transmission bracket. - Note the routing of shift cable on the vehicle prior to removing the shift cable from the vehicle. 11. Shift cable grommet from the floor panel. 12. Shift cable from the vehicle. INSTALL OR CONNECT - Prior to installing the shift cable to the vehicle, ensure that the column shift lever and the transmission control lever are in the mechanical park position. The transmission control lever can be positioned to mechanical park by rotating the control lever clockwise until it reaches its full clockwise stop position. 1. Shift cable to the vehicle. - Route the shift cable as noted during removal. 2. Shift cable grommet to floor panel. 3. Shift cable to the clip and/or tape on the floor pan. 4. Shift cable end to the steering column shift control. 5. Steering column filler panel to the steering column. 6. Carpet and carpet retainers on the driver's side. 7. Door sill trim plate. 8. Hinge pillar trim panel. 9. Front seat. 10. Ensure that the shift lever is in park. - Raise the vehicle. 11. Route shift cable under fuel lines and connect to rear transmission bracket. 12. Attach the shift cable to transmission shift cable bracket and secure with retaining clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Linkage, A/T > Shift Cable, A/T > Component Information > Service and Repair > 4L60-E (M30) Transmission > Page 7925 13. Remove the black shipping clip and discard. 14. Shift cable end to the transmission shift control lever by pushing the cable end onto the transmission shift control lever stud ball. 15. Adjust the shift cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Linkage, A/T > Shift Cable, A/T > Component Information > Service and Repair > 4L60-E (M30) Transmission > Page 7926 Shift Cable: Service and Repair 4L80-E (MT1) Transmission REMOVE OR DISCONNECT - Apply the parking brake - Position the steering column shift lever to park. - Raise and support the vehicle. 1. Front seat. 2. Door sill trim plate. 3. Hinge pillar trim panel. 4. Carpet and carpet retainers on the driver's side to expose the shift cable. 5. Steering column filler panel from the steering column. 6. Shift cable from the steering column shift control. - Prior to removing the shift cable from the vehicle, ensure that the transmission is in the mechanical park position. The transmission control lever can be positioned to mechanical park by rotating the control lever clockwise until it reaches its full clockwise stop position. 7. Shift cable from clip and/or tape on floor pan. 8. Retaining clip securing the shift cable to the transmission shift cable bracket. - Squeeze the retainers while pulling the cable towards the rear of the vehicle. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Shift Linkage, A/T > Shift Cable, A/T > Component Information > Service and Repair > 4L60-E (M30) Transmission > Page 7927 9. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 10. Shift cable from under the fuel line and from the rear transmission bracket. - Note the routing of shift cable on the vehicle prior to removing the shift cable from the vehicle. 11. Shift cable grommet from the floor panel. 12. Shift cable from the vehicle. INSTALL OR CONNECT - Prior to installing the shift cable to the vehicle, ensure that the column shift lever and the transmission control lever are in the mechanical park position. The transmission control lever can be positioned to mechanical park by rotating the control lever clockwise until it reaches its full clockwise stop position. 1. Shift cable to the vehicle. - Route the shift cable as noted during removal. 2. Shift cable grommet to floor panel. 3. Shift cable to the clip and/or tape on the floor pan. 4. Shift cable end to the steering column shift control. 5. Steering column filler panel to the steering column. 6. Carpet and carpet retainers on the driver's side. 7. Door sill trim plate. 8. Hinge pillar trim panel. 9. Front seat. 10. Ensure that the shift lever is in park. - Raise the vehicle. 11. Route shift cable under fuel lines and connect to rear transmission bracket. 12. Attach the shift cable to transmission shift cable bracket and secure with retaining clip. 13. Remove the black shipping clip and discard. 14. Shift cable end to the transmission shift control lever by pushing the cable end onto the transmission shift control lever stud ball. 15. Adjust the shift cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Speedometer Gear, A/T > Component Information > Service and Repair Speedometer Gear, A/T: Service and Repair 1. Disconnect speedometer cable or P.M. generator electrical connector at transmission. 2. Remove retainer bolt, retainer, P.M. generator if equipped, speedometer driven gear and O-ring seal. 3. Reverse procedure to install, using new O-ring and adding fluid as necessary. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sun Gear > Component Information > Technical Service Bulletins > Customer Interest: > 00-07-30-022D > Jun > 08 > A/T - 4L60/65E, No Reverse/2nd or 4th Gear Sun Gear: Customer Interest A/T - 4L60/65E, No Reverse/2nd or 4th Gear TECHNICAL Bulletin No.: 00-07-30-022D Date: June 10, 2008 Subject: No Reverse, Second Gear or Fourth Gear (Replace Reaction Sun Shell with More Robust Heat Treated Parts) Models: 1993 - 2005 GM Passenger Cars and Light Duty Trucks 2003 - 2005 HUMMER H2 with 4L60/65-E Automatic Transmission (RPOs M30 or M32) Supercede: This bulletin is being revised to add 2005 model year to the parts information. Please discard Corporate Bulletin Number 00-07-30-022C (Section 07 - Transmission/Transaxle). Condition Some customers may comment on a no reverse, no second or no fourth gear condition. First and third gears will operate properly. Cause The reaction sun gear (673) may not hold inside the reaction sun shell (670). Correction Important: There are FOUR distinct groups of vehicles and repair procedures involved. Vehicles built in the 2001 model year and prior that make use of a reaction shaft to shell thrust washer: ^ The sun shell can be identified by four square holes used to retain the thrust washer. Use reaction sun shell P/N 24228345, reaction carrier to shell thrust washer (699B) P/N 8642202 and reaction sun gear shell thrust washer (674) P/N 8642331er (674) P/N 8642331along with the appropriate seals and washers listed below. ^ Vehicles built in the 2001 model year and prior that have had previous service to the reaction sun shell: It is possible that some 2001 and prior model year vehicles have had previous service to the reaction sun shell. At the time of service, these vehicles may have been updated with a Reaction Sun Shell Kit (Refer to Service Bulletin 020730003) without four square holes to retain the thrust washer. If it is found in a 2001 model year and prior vehicles that the reaction sun shell DOES NOT have four square holes to retain the thrust washer, these vehicles must be serviced with P/Ns 24229825 (674), 24217328 and 8642331 along with the appropriate seals and washers listed below. ^ Vehicles built in the 2001 model year and later that make use of a reaction shaft to shell thrust bearing: The sun shell can be identified by no holes to retain the thrust washer. Use reaction sun shell, P/N 24229825, reaction carrier shaft to shell thrust bearing (669A), P/N 24217328 and reaction sun gear shell thrust washer (674), P/N 8642331 along with the appropriate seals and washers listed below. ^ Vehicles built from November, 2001 through June, 2002: These vehicles should have the reaction carrier shaft replaced when the sun shell is replaced. Use shell kit P/N 24229853, which contains a sun shell (670), a reaction carrier shaft (666), a reaction carrier shaft to shell thrust bearing (669A) and a reaction sun gear shell thrust washer (674). The appropriate seals and washers listed below should also be used. When servicing the transmission as a result of this condition, the transmission oil cooler and lines MUST be flushed. Refer to Corporate Bulletin Number 02-07-30-052. Follow the service procedure below for diagnosis and correction of the no reverse, no second, no forth condition. Important: If metallic debris is found on the transmission magnet, the transmission must be completely disassembled and cleaned. Metallic debris is defined as broken parts and pieces of internal transmission components. This should not be confused with typical "normal" fine particles found on all transmission magnets. Failure to properly clean the transmission case and internal components may lead to additional repeat repairs. 1. Remove the transmission oil pan and inspect the magnet in the bottom of the pan for metal debris. Refer to SI Document ID # 825141. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sun Gear > Component Information > Technical Service Bulletins > Customer Interest: > 00-07-30-022D > Jun > 08 > A/T - 4L60/65E, No Reverse/2nd or 4th Gear > Page 7939 2. Remove the transmission from the vehicle. Refer to the appropriate SI document. Important: ^ Inspect all the transmission components for damage or wear. Replace all damaged or worn components. The parts shown above should be sufficient to correct this concern. ^ This condition does not normally require replacement of the transmission completely. Components such as clutches, valve body, pump and torque converters will NOT require replacement to correct this condition. Disassemble the transmission and replace the appropriate parts listed below. Refer to the Unit Repair Manual - Repair Instructions. 3. Reinstall the transmission in the vehicle. Refer to appropriate service information. When servicing the transmission as a result of this condition, the transmission oil cooler and lines MUST be flushed. Refer to Corporate Bulletin Number 02-07-30-052. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sun Gear > Component Information > Technical Service Bulletins > Customer Interest: > 00-07-30-022D > Jun > 08 > A/T - 4L60/65E, No Reverse/2nd or 4th Gear > Page 7940 Parts Information Warranty Information For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sun Gear > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 00-07-30-022D > Jun > 08 > A/T - 4L60/65E, No Reverse/2nd or 4th Gear Sun Gear: All Technical Service Bulletins A/T - 4L60/65E, No Reverse/2nd or 4th Gear TECHNICAL Bulletin No.: 00-07-30-022D Date: June 10, 2008 Subject: No Reverse, Second Gear or Fourth Gear (Replace Reaction Sun Shell with More Robust Heat Treated Parts) Models: 1993 - 2005 GM Passenger Cars and Light Duty Trucks 2003 - 2005 HUMMER H2 with 4L60/65-E Automatic Transmission (RPOs M30 or M32) Supercede: This bulletin is being revised to add 2005 model year to the parts information. Please discard Corporate Bulletin Number 00-07-30-022C (Section 07 - Transmission/Transaxle). Condition Some customers may comment on a no reverse, no second or no fourth gear condition. First and third gears will operate properly. Cause The reaction sun gear (673) may not hold inside the reaction sun shell (670). Correction Important: There are FOUR distinct groups of vehicles and repair procedures involved. Vehicles built in the 2001 model year and prior that make use of a reaction shaft to shell thrust washer: ^ The sun shell can be identified by four square holes used to retain the thrust washer. Use reaction sun shell P/N 24228345, reaction carrier to shell thrust washer (699B) P/N 8642202 and reaction sun gear shell thrust washer (674) P/N 8642331er (674) P/N 8642331along with the appropriate seals and washers listed below. ^ Vehicles built in the 2001 model year and prior that have had previous service to the reaction sun shell: It is possible that some 2001 and prior model year vehicles have had previous service to the reaction sun shell. At the time of service, these vehicles may have been updated with a Reaction Sun Shell Kit (Refer to Service Bulletin 020730003) without four square holes to retain the thrust washer. If it is found in a 2001 model year and prior vehicles that the reaction sun shell DOES NOT have four square holes to retain the thrust washer, these vehicles must be serviced with P/Ns 24229825 (674), 24217328 and 8642331 along with the appropriate seals and washers listed below. ^ Vehicles built in the 2001 model year and later that make use of a reaction shaft to shell thrust bearing: The sun shell can be identified by no holes to retain the thrust washer. Use reaction sun shell, P/N 24229825, reaction carrier shaft to shell thrust bearing (669A), P/N 24217328 and reaction sun gear shell thrust washer (674), P/N 8642331 along with the appropriate seals and washers listed below. ^ Vehicles built from November, 2001 through June, 2002: These vehicles should have the reaction carrier shaft replaced when the sun shell is replaced. Use shell kit P/N 24229853, which contains a sun shell (670), a reaction carrier shaft (666), a reaction carrier shaft to shell thrust bearing (669A) and a reaction sun gear shell thrust washer (674). The appropriate seals and washers listed below should also be used. When servicing the transmission as a result of this condition, the transmission oil cooler and lines MUST be flushed. Refer to Corporate Bulletin Number 02-07-30-052. Follow the service procedure below for diagnosis and correction of the no reverse, no second, no forth condition. Important: If metallic debris is found on the transmission magnet, the transmission must be completely disassembled and cleaned. Metallic debris is defined as broken parts and pieces of internal transmission components. This should not be confused with typical "normal" fine particles found on all transmission magnets. Failure to properly clean the transmission case and internal components may lead to additional repeat repairs. 1. Remove the transmission oil pan and inspect the magnet in the bottom of the pan for metal debris. Refer to SI Document ID # 825141. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sun Gear > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 00-07-30-022D > Jun > 08 > A/T - 4L60/65E, No Reverse/2nd or 4th Gear > Page 7946 2. Remove the transmission from the vehicle. Refer to the appropriate SI document. Important: ^ Inspect all the transmission components for damage or wear. Replace all damaged or worn components. The parts shown above should be sufficient to correct this concern. ^ This condition does not normally require replacement of the transmission completely. Components such as clutches, valve body, pump and torque converters will NOT require replacement to correct this condition. Disassemble the transmission and replace the appropriate parts listed below. Refer to the Unit Repair Manual - Repair Instructions. 3. Reinstall the transmission in the vehicle. Refer to appropriate service information. When servicing the transmission as a result of this condition, the transmission oil cooler and lines MUST be flushed. Refer to Corporate Bulletin Number 02-07-30-052. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sun Gear > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 00-07-30-022D > Jun > 08 > A/T - 4L60/65E, No Reverse/2nd or 4th Gear > Page 7947 Parts Information Warranty Information For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sun Gear > Component Information > Technical Service Bulletins > All Other Service Bulletins for Sun Gear: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition Malfunction Indicator Lamp: All Technical Service Bulletins PROM - MIL ON, Poor Driveability Condition File In Section: 6E - Engine Fuel & Emission Bulletin No.: 76-65-04 Date: March, 1997 Subject: Malfunction Indicator Light (MIL) On, Poor Driveability Conditions (Perform Flash Calibration) Models: 1996-97 Chevrolet and GMC Light Duty Trucks 1996-97 Chevrolet Tiltmaster and GMC Forward W4 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L Engines (VINs X, W, M, R RPOs LF6, L35, L3O, L31) Condition An owner of the above mentioned vehicles may report that the Malfunction Indicator Light (MIL) is on and/or the vehicle has one or more of the following driveability conditions. 1. 5.7L (L31) only: Surge or chuggle at speeds of 42 to 65 MPH while at steady speed or under light to moderate acceleration with the TCC applied. 2. MIL on with DTC P0172 or P0175 stored but no reported driveability symptoms. 3. MIL on with TDC P1406 stored and rough engine or poor driveability symptoms. 4. When operating at altitudes above 5,000 feet, an audible spark knock noise is heard. 5. Hesitation and/or misfire during light cruise conditions due to ignition cross-fire with no DTC stored. This will only occur on V-6 engines with cam retard offset in excess of 26° and V-8's with cam retard offset in excess of 15°. 6. The MIL may be on and a DTC stored for an engine misfire but no misfire occurred. 7. Engine exhibits an idle speed surge or roll. 1996 Models Only 8. MIL on with DTC P0102 stored but no reported driveability symptoms. 9. 5.0L (L30) & 5.7L (L31) only: Difficult starting in extreme cold (below 0° F) conditions. 10. 5.7L (L31) only: Poorer than expected fuel economy when heavily loaded. 1997 Models Only 11. MIL on with DTC P0121 stored but no reported driveability symptoms. 12. C/K & S/T Models with either V-6 engine and manual transmission: An engine flare between shifts may be noted when the engine is cold. 13. Either V-6 engine and manual transmission: An engine flare between shifts may be noted when the engine is cold. 14. C/K, S/T and M/L Models equipped with L35 V-6 engine, an improvement to the vapor canister purge diagnostics is incorporated into the new calibrations so that the Tech II can turn on canister purge at idle speed. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sun Gear > Component Information > Technical Service Bulletins > All Other Service Bulletins for Sun Gear: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7953 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sun Gear > Component Information > Technical Service Bulletins > All Other Service Bulletins for Sun Gear: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7954 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sun Gear > Component Information > Technical Service Bulletins > All Other Service Bulletins for Sun Gear: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7955 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sun Gear > Component Information > Technical Service Bulletins > All Other Service Bulletins for Sun Gear: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7956 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sun Gear > Component Information > Technical Service Bulletins > All Other Service Bulletins for Sun Gear: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7957 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sun Gear > Component Information > Technical Service Bulletins > All Other Service Bulletins for Sun Gear: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7958 Follow the Strategy Based Diagnostic Steps for the customer's reported symptoms. If diagnosis does not reveal a cause, refer to the tables below for the applicable calibration change. Perform programming per the latest Techline information for programming procedures. Important The calibrations listed are FLASH calibrations and are not available from GMSPO. They are available on 1997 Techline CD Disc 5 and later. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J-6355 Use Published Labor Operation Time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sun Gear > Component Information > Technical Service Bulletins > All Other Service Bulletins for Sun Gear: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7964 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sun Gear > Component Information > Technical Service Bulletins > All Other Service Bulletins for Sun Gear: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7965 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sun Gear > Component Information > Technical Service Bulletins > All Other Service Bulletins for Sun Gear: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7966 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sun Gear > Component Information > Technical Service Bulletins > All Other Service Bulletins for Sun Gear: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7967 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sun Gear > Component Information > Technical Service Bulletins > All Other Service Bulletins for Sun Gear: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7968 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Sun Gear > Component Information > Technical Service Bulletins > All Other Service Bulletins for Sun Gear: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 7969 Follow the Strategy Based Diagnostic Steps for the customer's reported symptoms. If diagnosis does not reveal a cause, refer to the tables below for the applicable calibration change. Perform programming per the latest Techline information for programming procedures. Important The calibrations listed are FLASH calibrations and are not available from GMSPO. They are available on 1997 Techline CD Disc 5 and later. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J-6355 Use Published Labor Operation Time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Throttle Valve Cable/Linkage, A/T > Component Information > Description and Operation Throttle Valve Cable/Linkage: Description and Operation Fig. 9 TV Cable And Linkage. Fig. 10 Throttle Lever And Bracket Assembly. The throttle cable controls line pressures, shift points, shift feel, part throttle downshifts, and detent downshifts. The function of the cable is similar to the combined functions of a vacuum modulator and detent downshift cable. The cable operates the throttle lever and bracket assembly, Figs. 9 and 10. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Throttle Valve Cable/Linkage, A/T > Component Information > Description and Operation > Page 7973 Throttle Valve Cable/Linkage: Adjustments 1. Stop engine. Fig. 11 TV Cable Adjustment. 2. Depress and hold down readjust tab, Fig. 11, move slider through fitting, away from lever assembly, until slider stops against fitting. 3. Release readjust tab, then open throttle lever to its full throttle position to automatically adjust cable. 4. Release throttle lever and check cable for sticking or binding. The cable may appear to function properly with engine stopped and cold. Recheck cable with engine at normal operating temperature. 5. Road test vehicle. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Thrust Washer/Bearing, A/T > Component Information > Technical Service Bulletins > A/T - New Design Reaction Shell Thrust Washer Thrust Washer/Bearing: Technical Service Bulletins A/T - New Design Reaction Shell Thrust Washer File In Section: 07 - Transmission/Transaxle Bulletin No.: 02-07-30-003 Date: January, 2002 INFORMATION Subject: Engineering Changes to Reaction Shell Thrust Washer and Use of New Service Kit Models: 2001 and Prior Chevrolet Camaro, Corvette 2001 and Prior Pontiac Firebird 2001 and Prior Chevrolet and GMC C/K Models (Silverado, Tahoe, Suburban, Sierra, Yukon, Yukon XL) 2001 and Prior Chevrolet and GMC G, M/L-Van Models (Express, Savana, Astro, Safari) 2001 and Prior Chevrolet and GMC S/T Models (S10, Blazer, Sonoma, Jimmy) 2001 and Prior Oldsmobile Bravada With 4L60/4L65-E Automatic Transmission (RPOs M30 or M32) The reaction shaft to reaction shell thrust washer was changed to a thrust bearing during the 2001 model year. This change required additional changes to the input carrier to reaction shaft thrust bearing, the reaction carrier shaft and the reaction sun shell. Important: Due to the changes in these components, the service kit must be used when servicing any of these components. Do not mix components of the old style with components of the new style. If you mix components, transmission end play will be compromised and transmission shifting may not occur. A service kit is available that will allow these revised components to be used in those transmissions that were built with the previous style components. The new service kit as well as the previous style components are both available through GMSPO. Parts Information The service kit part number is provided for your information. Parts are currently available from GMSPO. DISCLAIMER Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Torque Converter > Component Information > Technical Service Bulletins > A/T - Torque Converter Replacement Information Torque Converter: Technical Service Bulletins A/T - Torque Converter Replacement Information INFORMATION Bulletin No.: 01-07-30-010C Date: May 12, 2008 Subject: Automatic Transmission/Transaxle Torque Converter Replacement Models: 2009 and Prior GM Passenger Cars and Trucks 2009 and Prior HUMMER H2, H3 2009 and Prior Saturn Cars and Light Duty Trucks (Except VTi Equipped Vehicles (RPO M16 and M75) 2009 and Prior Saab 9-7X with ALL Automatic Transmissions and Transaxles Supercede: This bulletin is being revised to add the 2007-2009 model years. Please discard Corporate Bulletin Number 01-07-30-010B (Section 07 - Transmission/Transaxle). The purpose of this bulletin is to help technicians determine when a torque converter should be replaced. Below is a list of general guidelines to follow. The converter should NOT be replaced if the following apply: ^ DTC P0742 - TCC stuck on is set. This code is almost always the result of a controls condition (i.e. stuck TCC solenoid/valve). Experience has shown that this code rarely indicates a mechanical concern within the torque converter. ^ The fluid has an odor or is discolored but no evidence of metal contamination. ^ Fine metal particles (traces of metal flakes/gray color to fluid ) are found in the converter. This is not harmful to the torque converter. ^ The vehicle has been exposed to high mileage. ^ A small amount of wear appears on the hub where the oil pump drive gear mates to the converter (RWD only). A certain amount of such wear is normal for both the hub and oil pump gear. Neither the converter nor the front pump assembly should be replaced. The torque converter should be replaced under any of the following conditions: ^ The vehicle has TCC shudder and/or no TCC apply. First complete all electrical and hydraulic diagnosis and check for proper engine operation. The converter clutch may be damaged. Also the converter bushing and/or internal 0-ring may be damaged. ^ Evidence of damage to the oil pump assembly pump shaft turbine shaft drive sprocket support and bearing or metal chips/debris in the converter. ^ Metal chips/debris are found in the converter or when flushing the cooler and the cooler lines. ^ External leaks in the hub weld area lug weld or closure weld. ^ Converter pilot is broken damaged or fits poorly into the crankshaft. ^ The converter hub is scored or damaged. ^ The transmission oil is contaminated with engine coolant engine oil or water. ^ If excessive end play is found after measuring the converter for proper end play (refer to Service Manual). ^ If metal chips/debris are found in the fluid filter or on the magnet and no internal parts in the unit are worn or damaged. This indicates that the material came from the converter. ^ The converter has an unbalanced condition that results in a vibration that cannot be corrected by following Converter Vibration Procedures. ^ Blue converter or dark circular ring between lugs. This condition will also require a complete cleaning of the cooler and a check for adequate flow Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Torque Converter > Component Information > Technical Service Bulletins > A/T - Torque Converter Replacement Information > Page 7982 through the cooler. ^ Converter bearing noise determined by noise from the bell housing area in Drive or Reverse at idle. The noise is gone in Neutral and Park. ^ If silicon from the viscous clutch is found in the lower pan (4T80-E ONLY). Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Torque Converter Clutch, A/T > Component Information > Technical Service Bulletins > Customer Interest for Torque Converter Clutch: > 77-71-53 > Apr > 97 > A/T - Chuggle/Surge on TCC Apply/No DTC's Torque Converter Clutch: Customer Interest A/T - Chuggle/Surge on TCC Apply/No DTC's File In Section: 7 - Transmission Bulletin No.: 77-71-53 Date: April, 1997 Subject: Chuggle/Surge on TCC Apply/No DTC's (Reflash PCM) Models: 1996-97 Chevrolet and GMC C/K, G Models with 5.7L Engine (VIN R - RPO L31) and HYDRA-MATIC 4L60-E Transmission (RPO M30) Condition Some owners of the above models may experience a chuggle/surge when TCC is applied under light throttle acceleration. Cause Engine inputs (Combustion events) exciting the vehicle platform/driveline or tire balance may be a contributing factor. Correction First ensure the most recent engine, not transmission calibration has been installed (Corp. # 76-65-04) and check tire balance. A new transmission calibration to correct chuggle/surge is available for use on vehicles with persistent concerns only. Important: This calibration will raise TCC engagement approximately 7-10 mph depending on application. This calibration should not be installed until the engine calibration listed above has been installed. Installation of this calibration may lead to decreased fuel economy due to TCC engagement at higher speeds. Reflash the Powertrain Control Module with the appropriate part numbers below. Refer to your Service Manual for proper procedure. Parts Information This new calibration will be available starting with the 1997 Disc 4 update. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J6355 Reflash Control Module Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Torque Converter Clutch, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Torque Converter Clutch: > 77-71-53 > Apr > 97 > A/T - Chuggle/Surge on TCC Apply/No DTC's Torque Converter Clutch: All Technical Service Bulletins A/T - Chuggle/Surge on TCC Apply/No DTC's File In Section: 7 - Transmission Bulletin No.: 77-71-53 Date: April, 1997 Subject: Chuggle/Surge on TCC Apply/No DTC's (Reflash PCM) Models: 1996-97 Chevrolet and GMC C/K, G Models with 5.7L Engine (VIN R - RPO L31) and HYDRA-MATIC 4L60-E Transmission (RPO M30) Condition Some owners of the above models may experience a chuggle/surge when TCC is applied under light throttle acceleration. Cause Engine inputs (Combustion events) exciting the vehicle platform/driveline or tire balance may be a contributing factor. Correction First ensure the most recent engine, not transmission calibration has been installed (Corp. # 76-65-04) and check tire balance. A new transmission calibration to correct chuggle/surge is available for use on vehicles with persistent concerns only. Important: This calibration will raise TCC engagement approximately 7-10 mph depending on application. This calibration should not be installed until the engine calibration listed above has been installed. Installation of this calibration may lead to decreased fuel economy due to TCC engagement at higher speeds. Reflash the Powertrain Control Module with the appropriate part numbers below. Refer to your Service Manual for proper procedure. Parts Information This new calibration will be available starting with the 1997 Disc 4 update. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J6355 Reflash Control Module Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON Torque Converter Clutch Solenoid: Customer Interest A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-023B Date: March, 2002 TECHNICAL Subject: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1999-2000 Cadillac Escalade 1996-2000 Chevrolet Camaro, Corvette 1996-2000 Pontiac Firebird 1996-2000 Chevrolet and GMC Light Duty Truck Models 1996-2000 Oldsmobile Bravada with 4L60-E Automatic Transmission (RPO M30) Built Prior to January 15, 2000 (Julian Date 0015) This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 Transmission/Transaxle). Condition Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated. Diagnosis Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs. The scan tool may show a DTC P1870 set as a history code. A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93° C (200°F). Cause The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply. Important: ^ DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code. ^ When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result. ^ This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle). ^ When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code. ^ When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL). Correction Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 8004 regulator and isolator valves. Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body. ^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears). ^ The torque converter is not blue or overheated. ^ The transmission fluid is not burned or has no burned odor ^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 8005 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON Torque Converter Clutch Solenoid: All Technical Service Bulletins A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-023B Date: March, 2002 TECHNICAL Subject: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1999-2000 Cadillac Escalade 1996-2000 Chevrolet Camaro, Corvette 1996-2000 Pontiac Firebird 1996-2000 Chevrolet and GMC Light Duty Truck Models 1996-2000 Oldsmobile Bravada with 4L60-E Automatic Transmission (RPO M30) Built Prior to January 15, 2000 (Julian Date 0015) This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 Transmission/Transaxle). Condition Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated. Diagnosis Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs. The scan tool may show a DTC P1870 set as a history code. A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93° C (200°F). Cause The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply. Important: ^ DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code. ^ When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result. ^ This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle). ^ When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code. ^ When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL). Correction Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 8011 regulator and isolator valves. Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body. ^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears). ^ The torque converter is not blue or overheated. ^ The transmission fluid is not burned or has no burned odor ^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 8012 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > A/T - Fluid Oil Cooler Flush Transmission Cooler: Technical Service Bulletins A/T - Fluid Oil Cooler Flush INFORMATION Bulletin No.: 02-07-30-052G Date: March 02, 2011 Subject: Automatic Transmission Oil Cooler Flush and Flow Test Essential Tool J 45096 TransFlow(R) Models: 2011 and Prior Passenger Cars and Light Duty Trucks 2003-2010 HUMMER H2 2006-2010 HUMMER H3 with Automatic Transmission/Transaxle including Allison(R) Transmissions Supercede: This bulletin is being revised to update the model years. Please discard Corporate Bulletin Number 02-07-30-052F (Section 07 - Transmission/Transaxle). Important All labor operations that include removal of the transmission from the vehicle include labor time to flush the transmission oil cooler system. The J 45096 transmission oil cooling system flush and flow test tool replaces current tool J 35944-A. J 45096 is a self-contained unit utilizing a 12-volt flow meter, shop air supply and DEXRON(R) VI automatic transmission fluid (ATF). In the flush mode, transmission fluid is cycled through the transmission oil cooling system. High-pressure air is automatically injected into the fluid stream adding agitation to the ATF oil to enhance the removal of contaminated ATF oil and debris. In the flow mode, an electronic flow meter is used to measure the flow capability of the ATF oil cooling system. A digital display indicates the ATF oil flow rate in gallons per minute (GPM) along with the amount of ATF oil in the supply vessel, supply vessel ATF oil temperature, machine cycles and the operating mode. The supply oil vessel has 30 L (32 qt) capacity and the waste oil vessel has 32 L (34 qt) capacity. The waste oil vessel is constructed of a translucent composite material that allows the user to easily identify the oil level. The waste oil vessel can accommodate vacuum evacuation and gravity draining. In the code mode, a random, encrypted code is generated that can be used for verification of flow test results. Current essential cooler line adapters are used to connect the J 45096 to the automatic transmission oil cooler lines that allows J 45096 to adapt to General Motors passenger cars and light duty trucks, current and past models (except the Pontiac Vibe, Wave and Chevrolet Aveo). The tool may be adapted for use on the Pontiac Vibe, Wave and Chevrolet Aveo by dealership personnel with a barbed hose connector and rubber hose obtained locally. The Vibe's/Wave's/Aveo's transmission has a transmission oil requirement which is slightly different than DEXRON(R) VI ATF. However, flushing the cooler with DEXRON(R) VI automatic transmission fluid is an acceptable service procedure. Very little fluid remains in the cooler after the flush procedure and the residual DEXRON(R) VI ATF in the cooler is compatible with the Vibe's/Wave's/Aveo's transmission fluid. Notice Insufficient oil flow through the ATF oil cooling system will cause premature transmission failure. The required minimum ATF oil flow rate reading is directly related to the supply oil temperature. Refer to the flow rate reference chart for the oil flow rate specification based on the temperature of the ATF in the supply vessel. Helpful Hints for Maintaining the Temperature at or above 18°C (65°F) Important - The temperature of the supply vessel oil must be 18°C (65°F) or greater for J 45096 to operate. It is recommended to store the J 45096 in an area of the dealership where the room temperature remains at or above 18°C (65°F) when not in use. - Do not attempt to increase the fluid temperature in the Transflow(R) machine with an engine oil dipstick, or any other immersion type heater. The Transflow(R) machine has a check valve in the supply reservoir. Inserting a heater will damage the check valve and the subsequent repair expense would be the dealer's responsibility. - A heater blanket, P/N J-45096-10, is available for the Transflow(R) transmission cooling system flushing tool. This heater fastens around the Transflow(R) internal supply vessel and runs on 110 volts AC. The heater will warm the ATF in the supply vessel to at least 18°C (65° F) and has a thermostat to hold a constant temperature. Store the Transmission Cooling System Service Tool, J 45096, Transflow(R) machine in a room where the temperature is maintained at or above 18°C (65°F). Keep the ATF level in the reservoir low when the Transmission Cooling System Service Tool, J 45096, Transflow(R), is not in use. Store several gallons of oil in an area where the temperature is maintained at or above 18°C (65°F). Fill the reservoir of the J 45096 as needed before using the machine on Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > A/T - Fluid Oil Cooler Flush > Page 8017 each repair. With the ATF in a tightly sealed container, place the container in a tub of hot water for a period of time. Then pour the ATF into the reservoir. This method works best with a low fluid level in the reservoir. Place the Transflow(R) machine in the direct sunlight with the cabinet door open to expose the reservoir to the rays of the warm sun. Flush / Flow Test Procedure Important All labor operations that include removal of the transmission from the vehicle and require the transmission oil pan or transmission side cover to be removed include labor time to flush the transmission oil cooler system. Refer to SI for Automatic Transmission Oil Cooler Flushing and Flow Test J 45096 for the appropriate procedure. Important The J 45096 can be used to flush the transmission oil cooler system on an Allison equipped vehicle, but the flow meter should not be utilized. Refer to SI for Automatic Transmission Oil Cooler Flushing and Flow Test J 45096 for the appropriate flow check procedure. Machine Displays After completion of the flush and flow test, the following information is to be recorded on the repair order. This information is displayed on the Transmission Cooling System Service Tool, J 45096, Transflow(R) machine when the dial is in the code position. - Tested flow rate (displayed in Gallons Per Minute (GPM) - Temperature (displayed is degrees Fahrenheit) - Cycle number (a number) - Seven digit Alpha/Numeric flow code (i.e. A10DFB2) Warranty Information Important All labor operations that include removal of the transmission from the vehicle include labor time to flush the transmission oil cooler system. Performing a transmission oil cooling system flush and flow test will use between 4.7-7.5 L (5-8 qts) of DEXRON(R)VI transmission fluid. The amount Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > A/T - Fluid Oil Cooler Flush > Page 8018 of transmission fluid (ATF), (DEXRON(R)VI) (fluid) that is to be charged for the flush portion of the repair should not exceed the allowable charge for 7.5 L (2 gal) of fluid. This expense should be shown in the Parts Section of the warranty claim document. The Seven digit Alpha/Numeric flow code, i.e. A10DFB2, "MUST" be written on the job card and placed in the comments section of the warranty claim. Any repair that requires the technician to contact the Product Quality Center (PQC) must also include the seven digit flow code. The agent will request the seven digit flow code and add the information to the PQC case prior to providing authorization for the warranty claim. The Seven digit Alpha/Numeric flow code, i.e. A10DFB2, "MUST" be written on the job card, entered in the warranty claim labor operation Flush Code additional field (when available) and placed in the comments section of the warranty claim. Any repair that requires the technician to contact the Product Quality Center (PQC) must also include the seven digit flow code. The agent will request the seven digit flow code and add the information to the PQC case prior to providing authorization for the warranty claim. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > 02-07-30-052G > Mar > 11 > A/T - Fluid Oil Cooler Flush Transmission Cooler: Technical Service Bulletins A/T - Fluid Oil Cooler Flush INFORMATION Bulletin No.: 02-07-30-052G Date: March 02, 2011 Subject: Automatic Transmission Oil Cooler Flush and Flow Test Essential Tool J 45096 TransFlow(R) Models: 2011 and Prior Passenger Cars and Light Duty Trucks 2003-2010 HUMMER H2 2006-2010 HUMMER H3 with Automatic Transmission/Transaxle including Allison(R) Transmissions Supercede: This bulletin is being revised to update the model years. Please discard Corporate Bulletin Number 02-07-30-052F (Section 07 - Transmission/Transaxle). Important All labor operations that include removal of the transmission from the vehicle include labor time to flush the transmission oil cooler system. The J 45096 transmission oil cooling system flush and flow test tool replaces current tool J 35944-A. J 45096 is a self-contained unit utilizing a 12-volt flow meter, shop air supply and DEXRON(R) VI automatic transmission fluid (ATF). In the flush mode, transmission fluid is cycled through the transmission oil cooling system. High-pressure air is automatically injected into the fluid stream adding agitation to the ATF oil to enhance the removal of contaminated ATF oil and debris. In the flow mode, an electronic flow meter is used to measure the flow capability of the ATF oil cooling system. A digital display indicates the ATF oil flow rate in gallons per minute (GPM) along with the amount of ATF oil in the supply vessel, supply vessel ATF oil temperature, machine cycles and the operating mode. The supply oil vessel has 30 L (32 qt) capacity and the waste oil vessel has 32 L (34 qt) capacity. The waste oil vessel is constructed of a translucent composite material that allows the user to easily identify the oil level. The waste oil vessel can accommodate vacuum evacuation and gravity draining. In the code mode, a random, encrypted code is generated that can be used for verification of flow test results. Current essential cooler line adapters are used to connect the J 45096 to the automatic transmission oil cooler lines that allows J 45096 to adapt to General Motors passenger cars and light duty trucks, current and past models (except the Pontiac Vibe, Wave and Chevrolet Aveo). The tool may be adapted for use on the Pontiac Vibe, Wave and Chevrolet Aveo by dealership personnel with a barbed hose connector and rubber hose obtained locally. The Vibe's/Wave's/Aveo's transmission has a transmission oil requirement which is slightly different than DEXRON(R) VI ATF. However, flushing the cooler with DEXRON(R) VI automatic transmission fluid is an acceptable service procedure. Very little fluid remains in the cooler after the flush procedure and the residual DEXRON(R) VI ATF in the cooler is compatible with the Vibe's/Wave's/Aveo's transmission fluid. Notice Insufficient oil flow through the ATF oil cooling system will cause premature transmission failure. The required minimum ATF oil flow rate reading is directly related to the supply oil temperature. Refer to the flow rate reference chart for the oil flow rate specification based on the temperature of the ATF in the supply vessel. Helpful Hints for Maintaining the Temperature at or above 18°C (65°F) Important - The temperature of the supply vessel oil must be 18°C (65°F) or greater for J 45096 to operate. It is recommended to store the J 45096 in an area of the dealership where the room temperature remains at or above 18°C (65°F) when not in use. - Do not attempt to increase the fluid temperature in the Transflow(R) machine with an engine oil dipstick, or any other immersion type heater. The Transflow(R) machine has a check valve in the supply reservoir. Inserting a heater will damage the check valve and the subsequent repair expense would be the dealer's responsibility. - A heater blanket, P/N J-45096-10, is available for the Transflow(R) transmission cooling system flushing tool. This heater fastens around the Transflow(R) internal supply vessel and runs on 110 volts AC. The heater will warm the ATF in the supply vessel to at least 18°C (65° F) and has a thermostat to hold a constant temperature. Store the Transmission Cooling System Service Tool, J 45096, Transflow(R) machine in a room where the temperature is maintained at or above 18°C (65°F). Keep the ATF level in the reservoir low when the Transmission Cooling System Service Tool, J 45096, Transflow(R), is not in use. Store several gallons of oil in an area where the temperature is maintained at or above 18°C (65°F). Fill the reservoir of the J 45096 as needed before using the machine on Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > 02-07-30-052G > Mar > 11 > A/T - Fluid Oil Cooler Flush > Page 8024 each repair. With the ATF in a tightly sealed container, place the container in a tub of hot water for a period of time. Then pour the ATF into the reservoir. This method works best with a low fluid level in the reservoir. Place the Transflow(R) machine in the direct sunlight with the cabinet door open to expose the reservoir to the rays of the warm sun. Flush / Flow Test Procedure Important All labor operations that include removal of the transmission from the vehicle and require the transmission oil pan or transmission side cover to be removed include labor time to flush the transmission oil cooler system. Refer to SI for Automatic Transmission Oil Cooler Flushing and Flow Test J 45096 for the appropriate procedure. Important The J 45096 can be used to flush the transmission oil cooler system on an Allison equipped vehicle, but the flow meter should not be utilized. Refer to SI for Automatic Transmission Oil Cooler Flushing and Flow Test J 45096 for the appropriate flow check procedure. Machine Displays After completion of the flush and flow test, the following information is to be recorded on the repair order. This information is displayed on the Transmission Cooling System Service Tool, J 45096, Transflow(R) machine when the dial is in the code position. - Tested flow rate (displayed in Gallons Per Minute (GPM) - Temperature (displayed is degrees Fahrenheit) - Cycle number (a number) - Seven digit Alpha/Numeric flow code (i.e. A10DFB2) Warranty Information Important All labor operations that include removal of the transmission from the vehicle include labor time to flush the transmission oil cooler system. Performing a transmission oil cooling system flush and flow test will use between 4.7-7.5 L (5-8 qts) of DEXRON(R)VI transmission fluid. The amount Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > 02-07-30-052G > Mar > 11 > A/T - Fluid Oil Cooler Flush > Page 8025 of transmission fluid (ATF), (DEXRON(R)VI) (fluid) that is to be charged for the flush portion of the repair should not exceed the allowable charge for 7.5 L (2 gal) of fluid. This expense should be shown in the Parts Section of the warranty claim document. The Seven digit Alpha/Numeric flow code, i.e. A10DFB2, "MUST" be written on the job card and placed in the comments section of the warranty claim. Any repair that requires the technician to contact the Product Quality Center (PQC) must also include the seven digit flow code. The agent will request the seven digit flow code and add the information to the PQC case prior to providing authorization for the warranty claim. The Seven digit Alpha/Numeric flow code, i.e. A10DFB2, "MUST" be written on the job card, entered in the warranty claim labor operation Flush Code additional field (when available) and placed in the comments section of the warranty claim. Any repair that requires the technician to contact the Product Quality Center (PQC) must also include the seven digit flow code. The agent will request the seven digit flow code and add the information to the PQC case prior to providing authorization for the warranty claim. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > 08-07-30-035B > Nov > 10 > A/T - Water Or Coolant Contamination Information Transmission Cooler: Technical Service Bulletins A/T - Water Or Coolant Contamination Information INFORMATION Bulletin No.: 08-07-30-035B Date: November 01, 2010 Subject: Information on Water or Ethylene Glycol in Transmission Fluid Models: 2011 and Prior GM Passenger Cars and Light Duty Trucks with Automatic Transmission Supercede: This bulletin is being revised to update model years. Please discard Corporate Bulletin Number 08-07-30-035A (Section 07 - Transmission/Transaxle). Water or ethylene glycol in automatic transmission fluid (ATF) is harmful to internal transmission components and will have a negative effect on reliability and durability of these parts. Water or ethylene glycol in ATF will also change the friction of the clutches, frequently resulting in shudder during engagement or gear changes, especially during torque converter clutch engagement. Indications of water in the ATF may include: - ATF blowing out of the transmission vent tube. - ATF may appear cloudy or, in cases of extreme contamination, have the appearance of a strawberry milkshake. - Visible water in the oil pan. - A milky white substance inside the pan area. - Spacer plate gaskets that appear to be glued to the valve body face or case. - Spacer plate gaskets that appear to be swollen or wrinkled in areas where they are not compressed. - Rust on internal transmission iron/steel components. If water in the ATF has been found and the source of the water entry has not been identified, or if a leaking in-radiator transmission oil cooler is suspected (with no evidence of cross-contamination in the coolant recovery reservoir), a simple and quick test kit is available that detects the presence of ethylene glycol in ATF. The "Gly-Tek" test kit, available from the Nelco Company, should be obtained and the ATF tested to make an accurate decision on the need for radiator replacement. This can help to prevent customer comebacks if the in-radiator transmission oil cooler is leaking and reduce repair expenses by avoiding radiator replacement if the cooler is not leaking. These test kits can be obtained from: Nelco Company Test kits can be ordered by phone or through the website listed above. Orders are shipped standard delivery time but can be shipped on a next day delivery basis for an extra charge. One test kit will complete 10 individual fluid sample tests. For vehicles repaired under warranty, the cost of the complete test kit plus shipping charges should be divided by 10 and submitted on the warranty claim as a net item. The transmission should be repaired or replaced based on the normal cost comparison procedure. Important If water or coolant is found in the transmission, the following components MUST be replaced. - Replace all of the rubber-type seals. - Replace all of the composition-faced clutch plates and/or bands. - Replace all of the nylon parts. - Replace the torque converter. - Thoroughly clean and rebuild the transmission, using new gaskets and oil filter. Important The following steps must be completed when repairing or replacing. Flush and flow check the transmission oil cooler using J 45096. Refer to Corporate Bulletin Number 02-07-30-052F- Automatic Transmission Oil Cooler Flush and Flow Test Essential Tool J 45096 TransFlow. - Thoroughly inspect the engine cooling system and hoses and clean/repair as necessary. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > 08-07-30-035B > Nov > 10 > A/T - Water Or Coolant Contamination Information > Page 8030 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > 03-07-30-027 > Jun > 03 > A/T - Oil Cooler Flushing Frequently Asked Questions Transmission Cooler: Technical Service Bulletins A/T - Oil Cooler Flushing Frequently Asked Questions File In Section: 07 - Transmission/Transaxle Bulletin No.: 03-07-30-027 Date: June, 2003 INFORMATION Subject: Most Frequently Asked Questions and Answers for J 45096 TransFlow Transmission Oil Cooling System Flushing Machine Models: 2004 and Prior Passenger Cars and Light Duty Trucks with Automatic Transmission/Transaxle 2004 and Prior HUMMER H2 This bulletin is issued to help answer the most frequently asked questions and concerns about essential tool J 45096. Q: Why doesn't the machine work below 18°C (65°F)? A: The flow characteristics of ATF at temperatures below 18°C (65°F) does not provide accurate flow test results with the electronics used in the J 45096. Q: Why didn't the unit come with a tank heater? A: The vast majority of dealerships do not require a heater to keep the ATF above 18°C (65°F). As a result, the heater was deleted as a cost-savings measure. A tank heater, J 45096-10, is currently available from Kent-Moore if your dealership requires it. Refer to Corporate Bulletin Number 03-07-30-002A for suggestions on warming the ATF without using a heater blanket. Q: Why does the machine fail new oil coolers? A: Several reasons have been found. The most likely reason is the air pressure at the air hose connected to the J 45096 is less than 586 kPa (85 psi). Other reasons include a twisted hose inside the J 45096 at the bulkhead as a result of the nut turning when the waste or supply hose was installed, the internal pressure regulator was improperly set at the factory or a problem with the cooler lines on the vehicle. Perform the J 45096 self-test as described on pages 9 and 10 of the Operation Manual. If a problem is still detected, refer to Troubleshooting on page 19 of the Operation Manual. If a problem still persists, contact Kent-Moore Customer Service at 1-800-345-2233. Q: What is the difference between steel and aluminum oil coolers? A: The aluminum oil cooler tube is slightly thinner in construction than the steel oil cooler tube, which affects the oil flow rate. The fitting that is protruding out of the radiator tank easily identifies the aluminum oil cooler. Refer to the Quick Reference card provided with the J 45096 in order to identify the proper flow rate for the aluminum oil cooler. Q: Why can't I use TransFlow for Allison transmission cooling Systems? A: Validation of TransFlow is currently under development for light duty trucks equipped with the Allison automatic transmission. TransFlow is based on the existing MINIMUM flow rate specification through the transmission oil cooling system. The Allison transmission oil cooling system only has MAXIMUM oil flow rates specified and J 45096 does not have the capability to test the transmission oil cooling system at the maximum oil flow rate specification. Q: Why doesn't GM publish a specification for auxiliary transmission oil coolers? A: The auxiliary oil cooler used with GM vehicles does not contain an internal turbulator plate like the radiator tank oil cooler does. Therefore, there is no internal restriction that would affect the flow rate through the oil cooling system so a specification for auxiliary oil cooler is not required. Keep in mind, kinks and damage to the auxiliary cooler and lines can affect the flow rate through the system. Q: Why did GM drop the labor time for transmission repairs? A: The labor for flushing and flow testing the transmission oil cooling system is included with the R&R; labor of the "K" labor operations that require transmission removal. The time required to use the J 45096 to perform the flush and flow test is much less than that of the J 35944-A. The warranty labor savings allowed GM to provide the J 45096 at no cost to dealerships. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > 03-07-30-027 > Jun > 03 > A/T - Oil Cooler Flushing Frequently Asked Questions > Page 8035 Q: Why didn't the machine come with the adapters to hook up to the car? A: The J 45096 was designed to use the previously released essential cooler line adapters for the J 35944-A. All adapters are listed on page 17 of the Operation Manual and can be ordered from Kent-Moore at 1-800-345-2233. Q: How do I connect the J 45096 to a Catera, Prizm or a Vibe? A: These vehicles, along with many other models, only require barbed fittings to connect to the rubber cooler hose. These fittings are commercially available and already found in many shops. Q: Why didn't I receive an Operation Manual with the machine? A: The Operation Manual was packaged in the upper portion of the shipping carton. If the shipping carton was lifted off the base without opening the top of the carton, the Operation Manual could have been discarded with the carton. Replacement Operation Manual packages can be obtained from Kent-Moore Customer Service at 1-800-345-2233. Q: Why can't I re-use the transmission fluid I use for flushing? A: The very fine metal and clutch material debris from the transmission failure in the ATF causes failures with the hall effect speed sensors that are used to measure the flow rate. To avoid costly repairs, expensive filters, regular maintenance and problems caused by a partially restricted filter, the filter was not included. Q: What do I do if I need service on my machine? A: Call Kent-Moore Customer Service at 1-800-345-2233. The J 45096 has a one-year warranty. Q: Can I flush and flow engine oil coolers? A: The engine oil cooler flow rates, the appropriate adapters and an acceptable procedure are currently under development. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > 36-71-03A > Jun > 98 > A/T - External Oil Cooler Kits Transmission Cooler: Technical Service Bulletins A/T - External Oil Cooler Kits File In Section: 7 - Transmission Bulletin No.: 36-71-03A Date: June, 1998 INFORMATION Subject: Automatic Transmission (AT) External Oil Coolers Models: 1988-98 Chevrolet and GMC C/K Models This bulletin is being revised to add the 1994-1998 model years and add two new cooler part numbers for 1996-1998 4L60-E equipped models. Please discard Corporate Bulletin Number 36-71-03 (Section 7 - Transmission). GMC/Chevrolet Truck has available to owners a high efficiency automatic transmission oil cooler. This cooler is also available as RPO KNP for many models in the C/K line. This new air to oil cooler offers excellent cooling ability. Because the high efficiency offered by this cooler exceeds many aftermarket coolers, we are offering this cooler in kit form for dealer installation. This cooler may be installed on both new and used vehicles that are in applications which create higher transmission operating temperatures. These applications typically include high frontal areas (either on the truck or trailer), or heavy loads where vehicles are operated at higher road speeds. The transmission oil coolers listed have been thoroughly tested and will provide the extra transmission oil cooling that trucks used in these applications may need. These kits can be installed in approximately 1.2 hours and include the following components: - Cooler - Mounting Brackets - Clamps - Flexible Lines - Fasteners - Installation Instructions Important: The installation of any auxiliary transmission oil cooler which is located ahead of the A/C condenser and radiator will reduce air flow through these components. A slight increase in engine operating temperatures, more frequent fan clutch engagement and a small decrease in A/C performance should be considered normal. Vehicles equipped with an external cooler and operated in cold climates should use DEXRON(R) III in their transmission. This fluid offers improved low temperature viscosity and high temperature oxidation stability. Parts Information Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > 77-71-68 > Oct > 97 > A/T - Cooler Flush Adapter Tools Transmission Cooler: Technical Service Bulletins A/T - Cooler Flush Adapter Tools File In Section: 7 - Transmission Bulletin No.: 77-71-68 Date: October, 1997 INFORMATION Subject: Cooler Flush Adapter Tools for HYDRA-MATIC 4T40-E Transaxle and 4L60-E Transmission Models: 1995-98 Chevrolet Cavalier 1997-98 Chevrolet Malibu 1997-98 Oldsmobile Cutlass 1995-98 Pontiac Sunfire with HYDRA-MATIC 4T40-E Transaxle (RPO MN4) and with 2.2L, 2.4L or 3.1 L Engine (VINs 4, T, M - RPOs LN2, LD9, L82) 1998 Chevrolet Camaro 1998 Oldsmobile Bravada 1998 Pontiac Firebird 1996-98 Chevrolet and GMC C/K, G Models 1998 Chevrolet and GMC M/L, S/T Models with HYDRA-MATIC 4L60-E Transmission (RPO M30) and with 2.2L, 3.8L, 4.3L, 5.0L or 5.7L Engine (VINs 4, G, K, W, X, M, R - RPOs LN2, LS1, L36, L35, LF6, L30, L31, L05) This bulletin contains information regarding new service tools which are now available from Kent-Moore. These tools will aid in oil cooler flushing and flow checking procedures. 4T40-E (Figure 1) A new cooler flush adapter tool J 35944-440 is available from Kent-Moore to aid in attaching the 4T40-E cooler lines to the existing Kent-Moore cooler flushing tool J 35944-A. A new cooler flow adapter tool J 42776 is available from Kent-Moore to aid in capturing return oil from the radiator during oil flow checking procedures. Disconnect the return cooler line at the radiator and install the cooler flow adapter tool J 42776 to the radiator to aid in capturing the transmission oil. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > 77-71-68 > Oct > 97 > A/T - Cooler Flush Adapter Tools > Page 8044 4L60-E (Figure 2) A new cooler flush adapter tool J 35944-200 is available from Kent-Moore to aid in attaching the 4L60-E quick connect cooler lines to the existing Kent-Moore cooler flushing tool J 35944-A. Cooler Flushing The transmission oil cooler must be flushed whenever a transmission is removed from the vehicle for service or if fluid contamination is suspected. Use the Kent-Moore tool J 35944-A and solvent J 35944-22 to flush the cooler. Instructions for using the cooler flushing tool and performing fluid flow check may be found in the On-Vehicle Service Section of the service manual or may be found on a Corporate Service Bulletin 77-71-59. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > 667102 > Mar > 96 > Engine & Transmission - Oil Cooler Quick Connect Fitting Transmission Cooler: Technical Service Bulletins Engine & Transmission - Oil Cooler Quick Connect Fitting File In Section: 7 - Transmission Bulletin No.: 65-71-02 Date: March, 1996 SERVICE MANUAL UPDATE Subject: Sections 7A14D and 7A17D, Automatic Transmission On-Vehicle Service - Enhanced Engine and Transmission Oil Cooler Line Quick Connect Fitting Procedures Models: 1996 Chevrolet and GMC C/K, S/T, M/L, G Models 1996 Oldsmobile Bravada with 4L60-E, 4L80-E Transmissions This bulletin has been created to enhance the support of the removal and installation of oil cooler lines from and to quick connect fittings on engines and transmissions. The content of this bulletin replaces any existing cooler line quick connect fitting procedures found in the 1996 S/T and C/K Truck and M/L and G Van Service Manuals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > 667102 > Mar > 96 > Engine & Transmission - Oil Cooler Quick Connect Fitting > Page 8049 OIL COOLER LINE QUICK CONNECT FITTINGS 1 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > 667102 > Mar > 96 > Engine & Transmission - Oil Cooler Quick Connect Fitting > Page 8050 OIL COOLER LINE QUICK CONNECT FITTINGS 2 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > 667102 > Mar > 96 > Engine & Transmission - Oil Cooler Quick Connect Fitting > Page 8051 OIL COOLER LINE QUICK CONNECT FITTINGS 3 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > 667102 > Mar > 96 > Engine & Transmission - Oil Cooler Quick Connect Fitting > Page 8052 OIL COOLER LINE QUICK CONNECT FITTINGS 4 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > Page 8053 Transmission Cooler: Technical Service Bulletins A/T - Water Or Coolant Contamination Information INFORMATION Bulletin No.: 08-07-30-035B Date: November 01, 2010 Subject: Information on Water or Ethylene Glycol in Transmission Fluid Models: 2011 and Prior GM Passenger Cars and Light Duty Trucks with Automatic Transmission Supercede: This bulletin is being revised to update model years. Please discard Corporate Bulletin Number 08-07-30-035A (Section 07 - Transmission/Transaxle). Water or ethylene glycol in automatic transmission fluid (ATF) is harmful to internal transmission components and will have a negative effect on reliability and durability of these parts. Water or ethylene glycol in ATF will also change the friction of the clutches, frequently resulting in shudder during engagement or gear changes, especially during torque converter clutch engagement. Indications of water in the ATF may include: - ATF blowing out of the transmission vent tube. - ATF may appear cloudy or, in cases of extreme contamination, have the appearance of a strawberry milkshake. - Visible water in the oil pan. - A milky white substance inside the pan area. - Spacer plate gaskets that appear to be glued to the valve body face or case. - Spacer plate gaskets that appear to be swollen or wrinkled in areas where they are not compressed. - Rust on internal transmission iron/steel components. If water in the ATF has been found and the source of the water entry has not been identified, or if a leaking in-radiator transmission oil cooler is suspected (with no evidence of cross-contamination in the coolant recovery reservoir), a simple and quick test kit is available that detects the presence of ethylene glycol in ATF. The "Gly-Tek" test kit, available from the Nelco Company, should be obtained and the ATF tested to make an accurate decision on the need for radiator replacement. This can help to prevent customer comebacks if the in-radiator transmission oil cooler is leaking and reduce repair expenses by avoiding radiator replacement if the cooler is not leaking. These test kits can be obtained from: Nelco Company Test kits can be ordered by phone or through the website listed above. Orders are shipped standard delivery time but can be shipped on a next day delivery basis for an extra charge. One test kit will complete 10 individual fluid sample tests. For vehicles repaired under warranty, the cost of the complete test kit plus shipping charges should be divided by 10 and submitted on the warranty claim as a net item. The transmission should be repaired or replaced based on the normal cost comparison procedure. Important If water or coolant is found in the transmission, the following components MUST be replaced. - Replace all of the rubber-type seals. - Replace all of the composition-faced clutch plates and/or bands. - Replace all of the nylon parts. - Replace the torque converter. - Thoroughly clean and rebuild the transmission, using new gaskets and oil filter. Important The following steps must be completed when repairing or replacing. Flush and flow check the transmission oil cooler using J 45096. Refer to Corporate Bulletin Number 02-07-30-052F- Automatic Transmission Oil Cooler Flush and Flow Test Essential Tool J 45096 TransFlow. - Thoroughly inspect the engine cooling system and hoses and clean/repair as necessary. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > Page 8054 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > Page 8055 Transmission Cooler: Technical Service Bulletins A/T - Oil Cooler Flushing Frequently Asked Questions File In Section: 07 - Transmission/Transaxle Bulletin No.: 03-07-30-027 Date: June, 2003 INFORMATION Subject: Most Frequently Asked Questions and Answers for J 45096 TransFlow Transmission Oil Cooling System Flushing Machine Models: 2004 and Prior Passenger Cars and Light Duty Trucks with Automatic Transmission/Transaxle 2004 and Prior HUMMER H2 This bulletin is issued to help answer the most frequently asked questions and concerns about essential tool J 45096. Q: Why doesn't the machine work below 18°C (65°F)? A: The flow characteristics of ATF at temperatures below 18°C (65°F) does not provide accurate flow test results with the electronics used in the J 45096. Q: Why didn't the unit come with a tank heater? A: The vast majority of dealerships do not require a heater to keep the ATF above 18°C (65°F). As a result, the heater was deleted as a cost-savings measure. A tank heater, J 45096-10, is currently available from Kent-Moore if your dealership requires it. Refer to Corporate Bulletin Number 03-07-30-002A for suggestions on warming the ATF without using a heater blanket. Q: Why does the machine fail new oil coolers? A: Several reasons have been found. The most likely reason is the air pressure at the air hose connected to the J 45096 is less than 586 kPa (85 psi). Other reasons include a twisted hose inside the J 45096 at the bulkhead as a result of the nut turning when the waste or supply hose was installed, the internal pressure regulator was improperly set at the factory or a problem with the cooler lines on the vehicle. Perform the J 45096 self-test as described on pages 9 and 10 of the Operation Manual. If a problem is still detected, refer to Troubleshooting on page 19 of the Operation Manual. If a problem still persists, contact Kent-Moore Customer Service at 1-800-345-2233. Q: What is the difference between steel and aluminum oil coolers? A: The aluminum oil cooler tube is slightly thinner in construction than the steel oil cooler tube, which affects the oil flow rate. The fitting that is protruding out of the radiator tank easily identifies the aluminum oil cooler. Refer to the Quick Reference card provided with the J 45096 in order to identify the proper flow rate for the aluminum oil cooler. Q: Why can't I use TransFlow for Allison transmission cooling Systems? A: Validation of TransFlow is currently under development for light duty trucks equipped with the Allison automatic transmission. TransFlow is based on the existing MINIMUM flow rate specification through the transmission oil cooling system. The Allison transmission oil cooling system only has MAXIMUM oil flow rates specified and J 45096 does not have the capability to test the transmission oil cooling system at the maximum oil flow rate specification. Q: Why doesn't GM publish a specification for auxiliary transmission oil coolers? A: The auxiliary oil cooler used with GM vehicles does not contain an internal turbulator plate like the radiator tank oil cooler does. Therefore, there is no internal restriction that would affect the flow rate through the oil cooling system so a specification for auxiliary oil cooler is not required. Keep in mind, kinks and damage to the auxiliary cooler and lines can affect the flow rate through the system. Q: Why did GM drop the labor time for transmission repairs? A: The labor for flushing and flow testing the transmission oil cooling system is included with the R&R; labor of the "K" labor operations that require transmission removal. The time required to use the J 45096 to perform the flush and flow test is much less than that of the J 35944-A. The warranty labor savings allowed GM to provide the J 45096 at no cost to dealerships. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > Page 8056 Q: Why didn't the machine come with the adapters to hook up to the car? A: The J 45096 was designed to use the previously released essential cooler line adapters for the J 35944-A. All adapters are listed on page 17 of the Operation Manual and can be ordered from Kent-Moore at 1-800-345-2233. Q: How do I connect the J 45096 to a Catera, Prizm or a Vibe? A: These vehicles, along with many other models, only require barbed fittings to connect to the rubber cooler hose. These fittings are commercially available and already found in many shops. Q: Why didn't I receive an Operation Manual with the machine? A: The Operation Manual was packaged in the upper portion of the shipping carton. If the shipping carton was lifted off the base without opening the top of the carton, the Operation Manual could have been discarded with the carton. Replacement Operation Manual packages can be obtained from Kent-Moore Customer Service at 1-800-345-2233. Q: Why can't I re-use the transmission fluid I use for flushing? A: The very fine metal and clutch material debris from the transmission failure in the ATF causes failures with the hall effect speed sensors that are used to measure the flow rate. To avoid costly repairs, expensive filters, regular maintenance and problems caused by a partially restricted filter, the filter was not included. Q: What do I do if I need service on my machine? A: Call Kent-Moore Customer Service at 1-800-345-2233. The J 45096 has a one-year warranty. Q: Can I flush and flow engine oil coolers? A: The engine oil cooler flow rates, the appropriate adapters and an acceptable procedure are currently under development. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Cooler, A/T > Component Information > Technical Service Bulletins > Technical Service Bulletins for Transmission Cooler: > Page 8057 Transmission Cooler: Technical Service Bulletins A/T - External Oil Cooler Kits File In Section: 7 - Transmission Bulletin No.: 36-71-03A Date: June, 1998 INFORMATION Subject: Automatic Transmission (AT) External Oil Coolers Models: 1988-98 Chevrolet and GMC C/K Models This bulletin is being revised to add the 1994-1998 model years and add two new cooler part numbers for 1996-1998 4L60-E equipped models. Please discard Corporate Bulletin Number 36-71-03 (Section 7 - Transmission). GMC/Chevrolet Truck has available to owners a high efficiency automatic transmission oil cooler. This cooler is also available as RPO KNP for many models in the C/K line. This new air to oil cooler offers excellent cooling ability. Because the high efficiency offered by this cooler exceeds many aftermarket coolers, we are offering this cooler in kit form for dealer installation. This cooler may be installed on both new and used vehicles that are in applications which create higher transmission operating temperatures. These applications typically include high frontal areas (either on the truck or trailer), or heavy loads where vehicles are operated at higher road speeds. The transmission oil coolers listed have been thoroughly tested and will provide the extra transmission oil cooling that trucks used in these applications may need. These kits can be installed in approximately 1.2 hours and include the following components: - Cooler - Mounting Brackets - Clamps - Flexible Lines - Fasteners - Installation Instructions Important: The installation of any auxiliary transmission oil cooler which is located ahead of the A/C condenser and radiator will reduce air flow through these components. A slight increase in engine operating temperatures, more frequent fan clutch engagement and a small decrease in A/C performance should be considered normal. Vehicles equipped with an external cooler and operated in cold climates should use DEXRON(R) III in their transmission. This fluid offers improved low temperature viscosity and high temperature oxidation stability. Parts Information Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Technical Service Bulletins > A/T - Park/Neutral Switch Connector Cannot Be Removed Transmission Position Switch/Sensor: Technical Service Bulletins A/T - Park/Neutral Switch Connector Cannot Be Removed File In Section: 7 - Transmission Bulletin No.: 83-71-10 Date: May, 1998 Subject: Park (Neutral Position Switch Connector Cannot be Removed (Replace Switch and Connectors) Models: 1997-98 Chevrolet Corvette 1995-98 Chevrolet and GMC S/T Models 1996-98 Chevrolet and GMC M/L, P Models 1996-99 Chevrolet and GMC C/K, G Models 1996-98 Oldsmobile Bravada Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer conditions, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to insure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to insure water-tight connections. Parts Information P/N Description 12450016 Switch 15305925 4-Way Connector Assembly 15305887 7-Way Connector Assembly Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 8064 Transmission Position Switch/Sensor: Locations Park/Neutral Position Switch Electronic 4-Speed Automatic Overdrive Transmission Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 8065 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions Transmission Position Switch/Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8068 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8069 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8070 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8071 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8072 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8073 Transmission Position Switch/Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8074 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8075 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8076 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8077 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8078 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8079 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8080 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8081 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8082 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8083 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8084 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8085 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8086 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8087 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8088 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8089 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8090 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8091 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8092 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8093 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8094 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8095 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8096 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8097 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8098 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8099 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8100 Transmission Position Switch/Sensor: Connector Views C1: Transmission Range Switch C2: Transmission Range Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8101 Transmission Position Switch/Sensor: Electrical Diagrams Electronic PRNDL Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8102 Starter And Charging (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 8103 Transmission Position Switch/Sensor: Testing and Inspection Pressure Switch Assembly Resistance Check (1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 8104 Pressure Switch Assembly Resistance Check (2 Of 2) Tools Required - J 39775 4L60E Jumper Harness - J 39200 Digital Multimeter - J 35616 Connector Test Adapter Kit Important: Whenever the transmission 20-way connector is disconnected and the engine is running, multiple DTCs will set. Be sure to clear these codes when you are finished with this procedure Important: This procedure tests the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) circuits and the Automatic Transmission Fluid Temperature (TFT) Sensor circuit. Do not use this procedure to test other Automatic Transmission circuits, refer to 4L60-E Automatic Transmission Internal Wiring Harness check. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 8105 Transmission Position Switch/Sensor: Adjustments PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 8106 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 8107 Transmission Position Switch/Sensor: Service and Repair PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 8108 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Pressure Test Port, A/T > Component Information > Specifications Line Pressure Specifications Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Pressure Test Port, A/T > Component Information > Locations > 4L60/4L60E Transmissions Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Pressure Test Port, A/T > Component Information > Locations > 4L60/4L60E Transmissions > Page 8114 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Speed Sensor, A/T > Component Information > Locations > Transmission Output Speed Sensor, 4L80E Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Transmission Speed Sensor, A/T > Component Information > Locations > Transmission Output Speed Sensor, 4L80E > Page 8119 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 01-07-30-038D > Sep > 06 > A/T - Poor Performance/MIL ON/DTC P0757 Valve Body: Customer Interest A/T - Poor Performance/MIL ON/DTC P0757 Bulletin No.: 01-07-30-038D Date: September 12, 2006 TECHNICAL Subject: Diagnostic Trouble Code (DTC) P0757 Set, Malfunction Indicator Lamp (MIL) Illuminated, Poor Performance of Transmission, Transmission Slipping (Clean Transmission Valve Body and Case Oil Passages of Debris) Models: 2007 and Prior GM Passenger Cars and Light Duty Trucks 2003-2007 HUMMER H2 2006-2007 HUMMER H3 2005-2007 Saab 9-7X with 4L60-E/4L65-E/4L70-E Automatic Transmission (RPOs M30/M32/M70) Supercede: This bulletin is being revised to add the 2007 model year and the 4L70-E transmission. Also, information has been added to Condition, Cause and Correction. Please discard Corporate Bulletin Number 01-07-30-038C (Section 07 - Transmission/Transaxle). Condition Some customers may comment on any of the following conditions: An illuminated MIL where DTC P0757 is found as a history code in the PCM or TCM. No 3rd and 4th gear. The transmission does not shift correctly. The transmission feels like it shifts to Neutral or a loss of drive occurs. The vehicle free wheels above 48 km/h (30 mph). High RPM needed to overcome the free wheeling. Cause This condition may be caused by any of the following: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 01-07-30-038D > Sep > 06 > A/T - Poor Performance/MIL ON/DTC P0757 > Page 8128 Chips or debris plugging the bleed orifice of the 2-3 shift solenoid (367). This will cause the transmission to stay in 2nd gear when 3rd gear is commanded and return to 1st gear when 4th gear is commanded. A 2-3 shift valve (368) or 2-3 shuttle valve (369) that is stuck, restricted and/or hung-up in its bore. This condition may also be an indication of a damaged 2-4 band or 3-4 clutches. This clutch damage may generate debris causing the 2-3 shift valve line-up to stick in the valve body bore and set DTC P0757. Correction Inspect the condition of the transmission fluid for signs of overheat or a burnt odor. If either is noted, the transmission should be disassembled for further investigation and repaired as needed. Inspect the inside of the oil pan for signs of clutch friction material. A small amount of friction material in the bottom of the pan is normal. If a large amount of clutch material is noted in the fluid or bottom pan, the transmission should be disassembled for further investigation and repaired as needed. Inspect and clean the 2-3 shift valve (368), the 2-3 shuttle valve (369) and the valve bore of debris/metal chips. Inspect and clean the 2-3 shift solenoid (367B) opening of debris/metal chips. While inspecting the 2-3 shift solenoid (367B), look for a screen over the solenoid opening. If the solenoid DOES NOT have a screen, replace the solenoid. All current GMSPO stock shift solenoids have a screen over the solenoid opening. If clutch debris is found, it is also very important to inspect the pressure control (PC) solenoid valve fluid screens. Clean or replace the PC solenoid as necessary. It is also important to flush and flow check the transmission oil cooler using J 45096. Refer to SI "Automatic Transmission Oil Cooler Flushing and Flow Test" for the procedure. Refer to the appropriate Service Manual for additional diagnostic information and service procedures. Warranty Information For repairs performed under warranty, use the applicable published labor code and information. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON Valve Body: Customer Interest A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-023B Date: March, 2002 TECHNICAL Subject: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1999-2000 Cadillac Escalade 1996-2000 Chevrolet Camaro, Corvette 1996-2000 Pontiac Firebird 1996-2000 Chevrolet and GMC Light Duty Truck Models 1996-2000 Oldsmobile Bravada with 4L60-E Automatic Transmission (RPO M30) Built Prior to January 15, 2000 (Julian Date 0015) This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 Transmission/Transaxle). Condition Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated. Diagnosis Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs. The scan tool may show a DTC P1870 set as a history code. A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93° C (200°F). Cause The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply. Important: ^ DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code. ^ When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result. ^ This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle). ^ When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code. ^ When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL). Correction Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 8133 regulator and isolator valves. Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body. ^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears). ^ The torque converter is not blue or overheated. ^ The transmission fluid is not burned or has no burned odor ^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 8134 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Valve Body: > 01-07-30-036H > Jan > 09 > A/T Control - DTC P0756 Diagnostic Tips Valve Body: All Technical Service Bulletins A/T Control - DTC P0756 Diagnostic Tips INFORMATION Bulletin No.: 01-07-30-036H Date: January 29, 2009 Subject: Diagnostic Tips for Automatic Transmission DTC P0756, Second, Third, Fourth Gear Start Models: 2009 and Prior GM Passenger Cars and Light Duty Trucks 2009 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X with 4L60-E, 4L65-E or 4L70E Automatic Transmission (RPOs M30, M32 or M70) Supercede: This bulletin is being revised to add the 2009 model year and add details regarding spacer plates. Please discard Corporate Bulletin Number 01-07-30-036G (Section 07 - Transmission/Transaxle). Some dealership technicians may have difficulty diagnosing DTC P0756, 2-3 Shift Valve Performance on 4L60-E, 4L65-E or 4L70E automatic transmissions. As detailed in the Service Manual, when the PCM detects a 4-3-3-4 shift pattern, DTC P0756 will set. Some customers may also describe a condition of a second, third or fourth gear start that may have the same causes but has not set this DTC yet. Below are some tips when diagnosing this DTC: ^ This is a performance code. This means that a mechanical malfunction exists. ^ This code is not set by electrical issues such as a damaged wiring harness or poor electrical connections. Electrical problems would cause a DTC P0758, P0787 or P0788 to set. ^ The most likely cause is chips/debris plugging the filtered AFL oil at orifice # 29 on the top of the spacer plate (48). This is a very small hole and is easily plugged by a small amount of debris. It is important to remove the spacer plate and inspect orifice # 29 and the immediate area for the presence of chips/debris. Also, the transmission case passage directly above this orifice and the valve body passage directly below should be inspected and cleaned of any chips/debris. For 2003 and newer vehicles the spacer plate should be replaced. The service replacement spacer plate is a bonded style with gaskets and solenoid filter screens bonded to the spacer plate. These screens can help to prevent plugging of orifice # 29 caused by small debris or chips. ^ This code could be set if the 2-3 shift valve (368) were stuck or hung-up in its bore. Inspect the 2-3 shift valve (368) and the 2-3 shuttle valve (369) for free movement or damage and clean the valves, the bore and the valve body passages. ^ This code could be set by a 2-3 shift solenoid (367b) if it were cracked, broken or leaking. Refer to Shift Solenoid Leak Test in the appropriate Service Manual for the leak test procedure. Based on parts return findings, a damaged or leaking shift solenoid is the least likely cause of this condition. Simply replacing a shift solenoid will not correct this condition unless the solenoid has been found to be cracked, broken or leaking. It is important to also refer to the appropriate Service Manual or Service Information (SI) for further possible causes of this condition. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Valve Body: > 01-07-30-038D > Sep > 06 > A/T - Poor Performance/MIL ON/DTC P0757 Valve Body: All Technical Service Bulletins A/T - Poor Performance/MIL ON/DTC P0757 Bulletin No.: 01-07-30-038D Date: September 12, 2006 TECHNICAL Subject: Diagnostic Trouble Code (DTC) P0757 Set, Malfunction Indicator Lamp (MIL) Illuminated, Poor Performance of Transmission, Transmission Slipping (Clean Transmission Valve Body and Case Oil Passages of Debris) Models: 2007 and Prior GM Passenger Cars and Light Duty Trucks 2003-2007 HUMMER H2 2006-2007 HUMMER H3 2005-2007 Saab 9-7X with 4L60-E/4L65-E/4L70-E Automatic Transmission (RPOs M30/M32/M70) Supercede: This bulletin is being revised to add the 2007 model year and the 4L70-E transmission. Also, information has been added to Condition, Cause and Correction. Please discard Corporate Bulletin Number 01-07-30-038C (Section 07 - Transmission/Transaxle). Condition Some customers may comment on any of the following conditions: An illuminated MIL where DTC P0757 is found as a history code in the PCM or TCM. No 3rd and 4th gear. The transmission does not shift correctly. The transmission feels like it shifts to Neutral or a loss of drive occurs. The vehicle free wheels above 48 km/h (30 mph). High RPM needed to overcome the free wheeling. Cause This condition may be caused by any of the following: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Valve Body: > 01-07-30-038D > Sep > 06 > A/T - Poor Performance/MIL ON/DTC P0757 > Page 8144 Chips or debris plugging the bleed orifice of the 2-3 shift solenoid (367). This will cause the transmission to stay in 2nd gear when 3rd gear is commanded and return to 1st gear when 4th gear is commanded. A 2-3 shift valve (368) or 2-3 shuttle valve (369) that is stuck, restricted and/or hung-up in its bore. This condition may also be an indication of a damaged 2-4 band or 3-4 clutches. This clutch damage may generate debris causing the 2-3 shift valve line-up to stick in the valve body bore and set DTC P0757. Correction Inspect the condition of the transmission fluid for signs of overheat or a burnt odor. If either is noted, the transmission should be disassembled for further investigation and repaired as needed. Inspect the inside of the oil pan for signs of clutch friction material. A small amount of friction material in the bottom of the pan is normal. If a large amount of clutch material is noted in the fluid or bottom pan, the transmission should be disassembled for further investigation and repaired as needed. Inspect and clean the 2-3 shift valve (368), the 2-3 shuttle valve (369) and the valve bore of debris/metal chips. Inspect and clean the 2-3 shift solenoid (367B) opening of debris/metal chips. While inspecting the 2-3 shift solenoid (367B), look for a screen over the solenoid opening. If the solenoid DOES NOT have a screen, replace the solenoid. All current GMSPO stock shift solenoids have a screen over the solenoid opening. If clutch debris is found, it is also very important to inspect the pressure control (PC) solenoid valve fluid screens. Clean or replace the PC solenoid as necessary. It is also important to flush and flow check the transmission oil cooler using J 45096. Refer to SI "Automatic Transmission Oil Cooler Flushing and Flow Test" for the procedure. Refer to the appropriate Service Manual for additional diagnostic information and service procedures. Warranty Information For repairs performed under warranty, use the applicable published labor code and information. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Valve Body: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON Valve Body: All Technical Service Bulletins A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-023B Date: March, 2002 TECHNICAL Subject: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1999-2000 Cadillac Escalade 1996-2000 Chevrolet Camaro, Corvette 1996-2000 Pontiac Firebird 1996-2000 Chevrolet and GMC Light Duty Truck Models 1996-2000 Oldsmobile Bravada with 4L60-E Automatic Transmission (RPO M30) Built Prior to January 15, 2000 (Julian Date 0015) This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 Transmission/Transaxle). Condition Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated. Diagnosis Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs. The scan tool may show a DTC P1870 set as a history code. A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93° C (200°F). Cause The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply. Important: ^ DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code. ^ When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result. ^ This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle). ^ When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code. ^ When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL). Correction Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Valve Body: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 8149 regulator and isolator valves. Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body. ^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears). ^ The torque converter is not blue or overheated. ^ The transmission fluid is not burned or has no burned odor ^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Valve Body: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 8150 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Valve Body: > 01-07-30-036H > Jan > 09 > A/T Control - DTC P0756 Diagnostic Tips Valve Body: All Technical Service Bulletins A/T Control - DTC P0756 Diagnostic Tips INFORMATION Bulletin No.: 01-07-30-036H Date: January 29, 2009 Subject: Diagnostic Tips for Automatic Transmission DTC P0756, Second, Third, Fourth Gear Start Models: 2009 and Prior GM Passenger Cars and Light Duty Trucks 2009 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X with 4L60-E, 4L65-E or 4L70E Automatic Transmission (RPOs M30, M32 or M70) Supercede: This bulletin is being revised to add the 2009 model year and add details regarding spacer plates. Please discard Corporate Bulletin Number 01-07-30-036G (Section 07 - Transmission/Transaxle). Some dealership technicians may have difficulty diagnosing DTC P0756, 2-3 Shift Valve Performance on 4L60-E, 4L65-E or 4L70E automatic transmissions. As detailed in the Service Manual, when the PCM detects a 4-3-3-4 shift pattern, DTC P0756 will set. Some customers may also describe a condition of a second, third or fourth gear start that may have the same causes but has not set this DTC yet. Below are some tips when diagnosing this DTC: ^ This is a performance code. This means that a mechanical malfunction exists. ^ This code is not set by electrical issues such as a damaged wiring harness or poor electrical connections. Electrical problems would cause a DTC P0758, P0787 or P0788 to set. ^ The most likely cause is chips/debris plugging the filtered AFL oil at orifice # 29 on the top of the spacer plate (48). This is a very small hole and is easily plugged by a small amount of debris. It is important to remove the spacer plate and inspect orifice # 29 and the immediate area for the presence of chips/debris. Also, the transmission case passage directly above this orifice and the valve body passage directly below should be inspected and cleaned of any chips/debris. For 2003 and newer vehicles the spacer plate should be replaced. The service replacement spacer plate is a bonded style with gaskets and solenoid filter screens bonded to the spacer plate. These screens can help to prevent plugging of orifice # 29 caused by small debris or chips. ^ This code could be set if the 2-3 shift valve (368) were stuck or hung-up in its bore. Inspect the 2-3 shift valve (368) and the 2-3 shuttle valve (369) for free movement or damage and clean the valves, the bore and the valve body passages. ^ This code could be set by a 2-3 shift solenoid (367b) if it were cracked, broken or leaking. Refer to Shift Solenoid Leak Test in the appropriate Service Manual for the leak test procedure. Based on parts return findings, a damaged or leaking shift solenoid is the least likely cause of this condition. Simply replacing a shift solenoid will not correct this condition unless the solenoid has been found to be cracked, broken or leaking. It is important to also refer to the appropriate Service Manual or Service Information (SI) for further possible causes of this condition. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Specifications > 4L60-E Automatic Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Specifications > 4L60-E Automatic Transmission > Page 8158 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Locations > Checkball Locations Valve Body: Locations Checkball Locations Case Checkballs and Filters Locations Case Checkball Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Locations > Checkball Locations > Page 8161 Control Valve Body Checkball Locations Fig. 11 Check Ball Location. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Locations > Checkball Locations > Page 8162 Valve Body: Locations Shift Solenoids Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Locations > Checkball Locations > Page 8163 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service Valve Body: Service and Repair In-Vehicle Service Control Valve Assembly 1. Disconnect battery ground cable. 2. Disconnect TV cable at throttle lever, then raise and support vehicle. 3. Drain transmission fluid, then remove transmission oil pan, filter and gasket. Fig.12 Auxiliary Valve Body Replacement 4. Remove two bolts that attach auxiliary accumulator valve tube to control valve assembly and accumulator valve body assembly, Fig. 12. 5. Remove two tube clamps, gently pry tube loose from oil pump assembly, then the auxiliary accumulator valve body assembly. 6. Disconnect electrical connectors at valve body. 7. Remove detent spring and roller assembly from valve body and remove valve body to case bolts. 8. Remove valve body assembly while disconnecting manual control valve link from range selector inner lever and removing throttle lever bracket from TV link. 9. Reverse procedure to install. Auxiliary Valve Body 1. Raise and support vehicle, then drain transmission fluid. 2. Remove transmission oil pan and filter. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8166 Fig.12 Auxiliary Valve Body Replacement 3. Remove two bolts that attach auxiliary accumulator valve tube to control valve assembly and accumulator valve body assembly, Fig. 12. 4. Remove two tube clamps, gently pry tube loose from oil pump assembly and auxiliary accumulator valve body assembly. 5. Remove three auxiliary accumulator valve body to transmission case attaching bolts. 6. Remove auxiliary valve body and check ball. 7. Reverse procedure to install. 4L80-E Automatic Transmission REMOVAL 1. Drain and remove oil pan, then filter and gasket. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8167 Fig.9 Transmission Wiring And Electrical Connectors. 2. Disconnect electrical connectors at valve body, Fig. 9. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8168 Fig. 10 Control Valve Assembly 3. Remove bolts from valve body assembly, manual detent spring and roller assembly, Fig. 10. Ensure five O-rings are attached to pressure manifold assembly. 4. Remove pressure manifold assembly. 5. Remove wiring clips, fluid level indicator stop, lube pipe, lube pipe retainer and clamps. 6. Remove control valve assembly including accumulator housing assembly, valve body gaskets, spacer plate and accumulator gasket. 7. Remove eight check balls from case passages. 8. Remove two speed sensors, bracket assemblies and PWM solenoid screen. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8169 INSTALLATION Fig. 11 Check Ball Location. 1. Install eight check balls as shown in Fig. 11 2. Install gasket spacer plate to case. 3. Install complete valve body assembly onto case using guide pin set tool No. J-25025-B or equivalent. 4. Install pressure manifold onto valve body assembly with spring and roller assembly in place. 5. Install wiring clip, then the fluid indicator stop. 6. Install control valve body assembly retaining bolts. 7. Connect wiring harness to connectors. Install large end into case first. 8. Install long end of lube pipe into case. 9. Install lube pipe clip with short bolt, tighten to specification. 10. Tighten valve body bolts to specification. 11. Install filter, then the pan and refill fluid. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8170 Valve Body: Service and Repair Unit Repair Pan and Filter Assembly PAN AND FILTER ASSEMBLY Pan, Filter And Seal Removal CLEAN - Exposed ends of bottom pan screws and spray with penetrating oil. REMOVE OR DISCONNECT 1. Screws (76), oil pan (75) and gasket (73). 2. Oil filter (72) and filter seal (71). - Filter seal may be stuck in the pump. INSPECT - Filter (72), open filter by prying the metal crimping away from the top of the filter (black) and pull apart. The filter may contain evidence for root cause diagnosis. Clutch material. - Bronze slivers indicating bushing wear. - Steel particles. Valve Body and Wiring Harness VALVE BODY AND WIRING HARNESS Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8171 Valve Body Bolt Location Control Valve And Pressure Switch Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8172 Manual Valve Link Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8173 Valve Body Checkballs Case Checkballs And Filters REMOVE OR DISCONNECT 1. Electrical connections from components. 2. TCC PWM Solenoid Retainer Clip (379) and Solenoid (396). 3. TCC Solenoid bolts (68) and solenoid assembly (66) with O-ring seal (65) and wiring harness. 4. Pressure switch assembly bolts (70) and pressure switch assembly (69). 5. Accumulator cover bolts (58 and 59) and 1-2 accumulator cover and pin assembly (57). 6. 1-2 accumulator piston (56) and seal (55). 7. Spring (54). 8. Dipstick stop bracket (93). REMOVE OR DISCONNECT 1. Bolt (64) and manual detent spring assembly (63). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8174 2. Wiring harness retaining bolts. REMOVE OR DISCONNECT 1. Remaining valve body bolts (62). 2. Manual valve link (89). 3. Control valve assembly (60). 4. Bolts (58 and 59), accumulator cover (57), piston (56, spring (54) and spring (54A). 5. Bolts (77) and plate (53). 6. Spacer plate (48) and spacer plate gaskets (47 and 52). 7. Spring (46), piston (44), and pin (43). - Seven checkballs are located under the valve body and one is located in the case. The large copper flash colored ball is # 1A checkball (91). Valve Body and Associated Parts VALVE BODY AND ASSOCIATED PARTS Accumulator Assembly, Spacer Plate And Gaskets Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8175 Case Checkballs And Filters TOOL REQUIRED: - J 25025-5 Guide Pins NOTICE: The use of a honing stone, fine sandpaper or crocus cloth is not recommended for servicing stuck valves. All valve lands have sharply machined corners that are necessary for "cleaning" the bore. If these corners are rounded, foreign material could wedge between the valve and bore causing the valve to stick. If it is found necessary to clean a valve, "micro fine" lapping compound 900 grit or finer should be used. Too much "lapping" of a valve will cause excessive clearances and increase the chance of a valve not operating. INSTALL OR CONNECT 1. The wiring harness pass-thru connector into the case. 2. The 3-4 accumulator pin (43) into the case. 3. The 3-4 accumulator piston seal (45) onto the 3-4 accumulator piston. 4. The 3-4 accumulator piston (44) onto the pin. - The end with three legs must face the valve body. 5. The 3-4 accumulator piston spring (46). INSTALL OR CONNECT 1. Checkball (91) into case as shown. - Retain with Transjel TM J 36850 or equivalent. 2. J 25025-5 into the case. 3. Screens onto spacer plate as shown. 4. Spacer plate to case gasket (47) and spacer plate to valve body gasket (52) onto the spacer plate (48). - Gasket (47) identified by a "C". Gasket (52) identified by a "V". - Retain with Transjel TM J 36850 or equivalent. 5. Spacer plate and gaskets onto the case. IMPORTANT - Be careful not to damage screens when installing the spacer plate and gaskets. 6. Spacer plate support (53) and bolts (77). TIGHTEN - Bolts to 11 Nm (8 lb. ft.) Control Valve Body CONTROL VALVE BODY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8176 Case Checkballs And Filters Filter Screen - Locations Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8177 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8178 Control Valve Assembly - Legend Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8179 Valve Body Checkball Locations Valve Body Bolt Locations Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8180 Manual Valve Link Outside Electrical Connector CLEAN - Control valve assembly thoroughly in clean solvent. A. Move the valves with a pick or small screwdriver to dislodge any dirt or debris that may have accumulated. B. Air dry. REMOVE OR DISCONNECT IMPORTANT - Some valves are under pressure - cover the bores while removing roll pins and retainer clips. - Valves, springs and bushings must be laid out on a clean surface in the exact sequence they are removed. 1. Pressure control solenoid retainer bolt (364) retainer (378) and solenoid. 2. Bore plug retainer clip (395), bore plug (376) and valve train (374 and 375). 3. 2-3 shift solenoid retainer (379), solenoid (367) and valve train (368 and 369). 4. 1-2 shift solenoid retainer (379), solenoid (367) and valve train (365 and 366). 5. Accumulator valve train retainer pin (360), bore plug (373) and valve train (370 and 371). 6. Forward accumulator cover bolts (364) and cover (363). 7. Forward accumulator spring (356), piston (354) and pin (355). 8. Lo overrun valve spring (362) and valve (361). 9. Retainer pin (360), bore plug (359) and forward abuse valve train (357 and 358). 10. Manual valve (340). 11. 3-2 control solenoid retainer clip (379) and solenoid (394). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8181 12. Bore plug retainer (395), bore plug (381) and 3-2 control valve train (391 - 393). 13. 3-2 downshift bore plug retainer (395), bore plug (381) and valve train (389 - 390). 14. Reverse abuse bore plug retainer pin (360), bore plug (359) and valve train (387 - 388). 15. 3-4 shift valve bore plug retainer (395), bore plug (381) and valve train (385 - 386). 16. 3-4 relay bore plug retainer (395), bore plug (381) and valve train (382 - 384). 17. Torque converter clutch signal valve bore plug retainer (395), bore plug (381) and valve (380). CLEAN - All valves, springs, bushings and control valve body in clean solvent. - Dry using compressed air. INSPECT - All valves and bushings for: Porosity - Scoring - Nicks - Scratches - Springs for damaged or distorted coils. - Valve body casting for: Porosity - Cracks - Inter connected oil passages - Damaged machined surfaces ASSEMBLE - Control valve assembly (350) exactly as shown. Notice the position of the valve lands and bushing passages. - Position the pressure control solenoid so the connector tabs face outward. NOTICE: TCC PWM solenoid (396) cannot be installed until TCC solenoid has been installed and torqued to proper specifications. INSTALL OR CONNECT 1. Checkballs into the valve body assembly (350). - Retain with Transjell TM J 36850 or equivalent. 2. Valve body assembly (350). - Connect the manual valve link (89) to the inside detent lever (88). - Be careful not to damage screens when installing the valve body assembly. 3. Wiring harness (66), manual spring assembly (63), pressure switch assembly(69), dipstick, stop bracket (93) and all remaining valve body bolts. NOTICE: Torque valve body bolts in a spiral pattern starting from the center. If bolts are torqued at random, valve bores may be distorted and inhibit valve operation. 4. TCC solenoid (66) and bolts (68). TIGHTEN - Bolts to 11 Nm (8 lb. ft.). 5. TCC PWM solenoid (396), and retainer clip (379). INSTALL OR CONNECT - Wiring harness connections to electrical components. - To correctly hook up the wires, see the wiring diagrams. - The pressure control solenoid (377) has two different colored connectors. The black connector should be installed on the tab farthest from the valve body. INSTALL OR CONNECT 1. Parking bracket (86). TIGHTEN - Bolts to 31 Nm (23 lb. ft.). 2. The 1-2 accumulator piston seal (55) onto the 1-2 accumulator piston (56). 3. The 1-2 accumulator spring (54) and 1-2 accumulator inner spring (54A) onto the piston (56). 4. The 1-2 accumulator piston (56) into the 1-2 accumulator cover and pin assembly (57). - The three legs on the piston must face away from the case when installed. 5. The 1-2 accumulator cover and pin assembly (57) onto the case. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8182 TIGHTEN - Torque to 11 Nm (8 lb. ft.). Pan and Filter Assembly PAN AND FILTER ASSEMBLY Case, Pan And Filter Assembly INSTALL OR CONNECT 1. Filter seal (71) into the pump. 2. Oil filter (72). 3. Oil pan gasket (73). 4. Chip magnet (74) onto oil pan (75). 5. Oil pan (75) and bolts (76). TIGHTEN - Torque to 12 Nm (9 lb. ft.). Pan and Filter Assembly PAN AND FILTER ASSEMBLY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8183 Pan, Filter And Seal Removal REMOVE OR DISCONNECT 1. Drain the transmission fluid Out case extension by rotating transmission to a vertical position. 2. Seventeen bolts (27), using 10 mm socket, drain transmission fluid. 3. Pan (28), seal (29) and magnet (30). IMPORTANT - Seal (29) is reusable. 4. Filter assembly (31). INSPECT - Filter neck seal (32), replace if necessary. Wire Harness Assembly WIRE HARNESS ASSEMBLY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8184 Pan, Filter And Seal Removal REMOVE OR DISCONNECT 1. Wire harness connectors from electrical components. NOTICE: Excessive force on the case pass through connector may damage the connector. IMPORTANT - If the wire harness assembly does not need servicing, it is not necessary to remove it from the case. 2. Wire harness assembly (34) from case using a 1-5/16" 12 point socket to release the connector retaining clips. Control Valve Assembly CONTROL VALVE ASSEMBLY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8185 REMOVE OR DISCONNECT 1. Rotate transmission bottom pan surface up and lock in place. 2. Wire harness assembly (34) connectors from components. IMPORTANT - If the wire harness assembly does not need servicing, it is not necessary to remove it from the case. - Use a cap to cover electrical pin at case connection. 3. Six bolts (76) using 8 mm socket, and transmission fluid pressure switch assembly (40). NOTICE: Be sure five O-rings are attached to transmission fluid pressure switch assembly. 4. Twenty-one bolts (35) using 10 mm socket, from valve body assembly, manual detent spring and roller assembly (41). 5. Three wiring clamps (33), fluid level indicator stop (43), one bolt (36) using 10 mm socket, lube pipe (39), lube pipe retainer (37) and clamp (38). 6. Control valve assembly (44) including the accumulator housing assembly (51), valve body gaskets (45 and 48), spacer plate (46) and accumulator gasket (47). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8186 7. Manual valve (319) from control valve assembly (44) to prevent any damage. 8. Checkballs (54) from case passages. NOTICE: Do not use a magnet. It could cause checkball(s) to be magnetized causing metal particles to stick to the ball. 9. Pulse Width Modulated (PWM) solenoid screen (75). INSPECT - Screen PWM solenoid (75), replace if necessary. DISASSEMBLE Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8187 - Control valve assembly. A. Position as shown on a clean surface. B. Remove blind hole retainer pins with a drill bit. CAUTION: Some valves are under pressure - cover the bores while removing the retaining pins or personal injury could result. C. Remove valve trains, shift solenoids (311 and 313), PCS (320), PWM solenoid (323), PCS screen (302) and shift solenoid filter (317). D. Valves, springs, bushings and pistons must be laid out on a clean surface. CLEAN - All valves, springs, bushings, pistons, control valve body and accumulator housing in clean solvent. - Dry using compressed air. INSPECT 1. All valves, pistons and bushings for: - Porosity. - Scoring. - Nicks. - Scratches. 2. Pistons for: - Seal damage. 3. Springs for: - Damaged or distorted coils. 4. Valve body casting and accumulator housing for: - Porosity. - Cracks. - Interconnected passages. - Damaged machined surfaces. 5. Solenoid connectors and filter (317). 6. PCS (Pressure Control Solenoid) screen (302). Control Valve Assembly/Accumulator Housing CONTROL VALVE ASSEMBLY/ACCUMULATOR HOUSING Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8188 Control Valve Assembly/Accumulator Housing Accumulator Housing Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8189 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8190 Torque Sequence And Guide Pin Location Fig. 11 Check Ball Location. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8191 Fig. 10 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8192 Torque Sequence, Control Valve And Switch Assembly NOTICE: The use of a honing stone, fine sandpaper or crocus cloth is not recommended for servicing stuck valves. All valve lands have sharply machined comers that are necessary for cleaning the bore. If these corners are rounded, foreign material could wedge between the valve and the bore causing the valve to stick. If it is found necessary to clean a valve, micro fine lapping compound 900 grit (J 38459) or finer should be used. Too much lapping of the valve will cause excessive clearances and increase the chance of a valve not operating. CLEAN - Control valve assembly and accumulator housing (51) thoroughly in clean solvent. - Air dry. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8193 Accumulator Housing Assembly ACCUMULATOR HOUSING ASSEMBLY Control Valve Assembly/Accumulator Housing Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8194 Accumulator Housing Assembly DISASSEMBLE 1. Six bolts (53), using 8 mm socket. 2. Accumulator housing assembly. 3. Gasket accumulator housing (47). 4. Spacer plate (46). 5. Gasket (45) valve body spacer. 6. Snap ring (402) from outside housing, pin (408), snap ring (402), piston (407) and spring (49). 7. 3rd clutch piston (405) and spring (50). 8. Seals (404 and 406). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8195 CLEAN - All components. INSPECT - All valves, pistons, springs and seals for: - Porosity. - Scoring. - Nicks. - Scratches. Accumulator Housing Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8196 ASSEMBLE - Accumulator housing assembly components exactly as shown. Notice the positions of the pistons. Control Valve Assembly CONTROL VALVE ASSEMBLY Control Valve Assembly ASSEMBLE - Control valve assembly components exactly as shown. Notice the position of the valve lands and bushing passages. Control Valve Assembly/Accumulator Housing Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8197 CONTROL VALVE ASSEMBLY AND ACCUMULATOR HOUSING Control Valve Assembly/Accumulator Housing Torque Sequence And Guide Pin Location TOOL REQUIRED: - Guide Pin J 25025-5 ASSEMBLE 1. Guide pin J 25025-5 into valve body. Located at back bolt hole of detent spring and roller assembly bolt bole. 2. Gasket (45) valve body to spacer plate. 3. Spacer plate (46). 4. Gasket (47) accumulator housing to spacer plate. 5. Accumulator housing assembly (51) onto valve body assembly (44). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8198 6. Six bolts (53) using (8 mm) socket through accumulator housing into valve body assembly. Torque Sequence And Guide Pin Location NOTE: Start accumulator housing bolts finger tight and work towards opposite end. TIGHTEN - Bolt (53) to 11 Nm (97 lb. in.). 7. Remove guide pin J 25025-5. Fig. 11 Check Ball Location. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8199 Fig. 10 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8200 Torque Sequence, Control Valve And Switch Assembly INSTALL OR CONNECT 1. Install checkballs (54) in proper location into case fluid passages. Use TRANSJEL TM J 36850 or equivalent to hold in place. NOTICE: Do not use any type of grease to retain parts during assembly of this unit. Greases other than the recommended assembly lube will change transmission fluid characteristics and cause undesirable shift conditions and/or filter clogging. - # 2 checkball is used only on RCP RDP, ZJP and ZLP models. 2. PWM solenoid screen (75). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8201 3. Gasket (48) spacer plate to case. 4. Manual valve (319) into valve body. 5. Complete valve body assembly (44) onto case (7). Use 1 25025-5 guide pin set. IMPORTANT - Attach manual valve to detent lever. 6. Transmission fluid pressure switch assembly (40) onto valve body assembly (44). 7. Spring and roller assembly (41) into place. 8. Three wiring clamps (33), fluid indicator stop (43) and lube pipe clamp (38). 9. Twenty-one bolts (35). Using 10 mm socket. 10. Six bolts (76) using 8 mm socket into transmission fluid pressure switch assembly (40). 11. Lube pipe (39) long end into case, short end into valve body. 12. Lube pipe retainer (37) with short bolt (36). TIGHTEN - Bolts (35, 36 and 76) to 11 Nm (97 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8202 Torque Sequence, Control Valve And Switch Assembly NOTICE: Torque valve body bolts in a spiral pattern starting from the center. If bolts are torqued at random, valve bores may be distorted and inhibit valve operation. 13. Attach wiring harness (34) to 5 connectors. - Put large end into case first, pressure switch hook up, 1-2 shift solenoid (purple) and 2-3 shift solenoid (tan), PWM (Pulse Width Modulated) solenoid and PCS (Pressure Control Solenoid). Pan and Filter Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Valve Body, A/T > Component Information > Service and Repair > In-Vehicle Service > Page 8203 PAN AND FILTER ASSEMBLY Installing Pan And Filter INSTALL OR CONNECT 1. Seal (32) inside of case (7). 2. Filter assembly (31). 3. Bottom pan seal (29). 4. Magnet (30) into bottom pan. 5. Pan (29). 6. Seventeen bolts (27) using 10 mm socket. TIGHTEN - Bolts (27) to 24 Nm (18 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Wiring Harness, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder Wiring Harness: Customer Interest A/T - Upshift Flare/No 3rd or 4th/Launch Shudder File In Section: 07 - Transmission/Transaxle Bulletin No.: 00-07-30-026 Date: December 2000 TECHNICAL Subject: Automatic Transmission 1-2 and/or 2-3 Upshift Slip/Flare, No 3rd or 4th gear, Launch Shudder (Revise VCM Wiring) Models: 1996 Chevrolet and GMC C/K, S/T, M/L, G1, G2, P3 Models 1996 Oldsmobile Bravada with VCM and 4L60-E (M30) or 4L80-E (MT1) Automatic Transmission This bulletin is being reissued to ensure that correct procedures are followed for this condition. Please discard Corporate Bulletin Number 66-71-03A (Section 7 - Automatic Transmission). When performing a transmission replacement labor operation K7000 on these vehicles with a 4L60-E or 4L80-E, you must include front chassis wire repair labor operation N6112. Inspect the VCM to verify the latest part number revision (16244210). Condition Some owners may comment that the automatic transmission has either a slip or flare on the 1-2 and/or 2-3 upshift, or no 3rd or 4th gear, or launch shudder. Upon investigation, the technician may find a DTC P1870 stored in the VCM. Cause A poor internal ground between the two circuit boards of the VCM may cause the VCM to command erratic line pressure at the pressure control (PC) solenoid valve. Correction Using harness jumper wire and instruction kit, P/N 12167310, revise the wiring harness at the VCM connector. Corrections were made to the VCM beginning 2/14/96. The corrected VCMs are identified with service number 16244210 on the VCM identification label. Procedure The following is a summary of the instructions included with the service kit: 1. Remove the negative terminal from the battery. 2. Move the wire located at connector J3 (WHITE/GREY/CLEAR), pin 18 to connector J1 (BLUE), pin 23. 3. Install the jumper wire between connector J2 (RED), pin 26 and connector J3 (WHITE/GREY/CLEAR), pin 18. 4. Install the tag included in the kit around the. VCM wiring harness. This tag notes that the wiring harness has been modified. 5. Reconnect the negative battery terminal. Road test to verify that the condition has been corrected. If any of the following conditions are noted, the transmission should be repaired or replaced using the most cost effective method. Canadian dealers should repair the transmission. ^ Transmission fluid oxidation or excessive sediment. ^ Transmission slip or flare after this service fix is performed. ^ DTC P1870 is stored on a 4L60-E (M30). The following tools are available from Kent-Moore (1-800-345-2233) for use in removing and relocating the VCM wires: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Wiring Harness, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder > Page 8212 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Wiring Harness, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 00-07-30-026 > Dec > 00 > A/T Upshift Flare/No 3rd or 4th/Launch Shudder Wiring Harness: All Technical Service Bulletins A/T - Upshift Flare/No 3rd or 4th/Launch Shudder File In Section: 07 - Transmission/Transaxle Bulletin No.: 00-07-30-026 Date: December 2000 TECHNICAL Subject: Automatic Transmission 1-2 and/or 2-3 Upshift Slip/Flare, No 3rd or 4th gear, Launch Shudder (Revise VCM Wiring) Models: 1996 Chevrolet and GMC C/K, S/T, M/L, G1, G2, P3 Models 1996 Oldsmobile Bravada with VCM and 4L60-E (M30) or 4L80-E (MT1) Automatic Transmission This bulletin is being reissued to ensure that correct procedures are followed for this condition. Please discard Corporate Bulletin Number 66-71-03A (Section 7 - Automatic Transmission). When performing a transmission replacement labor operation K7000 on these vehicles with a 4L60-E or 4L80-E, you must include front chassis wire repair labor operation N6112. Inspect the VCM to verify the latest part number revision (16244210). Condition Some owners may comment that the automatic transmission has either a slip or flare on the 1-2 and/or 2-3 upshift, or no 3rd or 4th gear, or launch shudder. Upon investigation, the technician may find a DTC P1870 stored in the VCM. Cause A poor internal ground between the two circuit boards of the VCM may cause the VCM to command erratic line pressure at the pressure control (PC) solenoid valve. Correction Using harness jumper wire and instruction kit, P/N 12167310, revise the wiring harness at the VCM connector. Corrections were made to the VCM beginning 2/14/96. The corrected VCMs are identified with service number 16244210 on the VCM identification label. Procedure The following is a summary of the instructions included with the service kit: 1. Remove the negative terminal from the battery. 2. Move the wire located at connector J3 (WHITE/GREY/CLEAR), pin 18 to connector J1 (BLUE), pin 23. 3. Install the jumper wire between connector J2 (RED), pin 26 and connector J3 (WHITE/GREY/CLEAR), pin 18. 4. Install the tag included in the kit around the. VCM wiring harness. This tag notes that the wiring harness has been modified. 5. Reconnect the negative battery terminal. Road test to verify that the condition has been corrected. If any of the following conditions are noted, the transmission should be repaired or replaced using the most cost effective method. Canadian dealers should repair the transmission. ^ Transmission fluid oxidation or excessive sediment. ^ Transmission slip or flare after this service fix is performed. ^ DTC P1870 is stored on a 4L60-E (M30). The following tools are available from Kent-Moore (1-800-345-2233) for use in removing and relocating the VCM wires: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Wiring Harness, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 00-07-30-026 > Dec > 00 > A/T Upshift Flare/No 3rd or 4th/Launch Shudder > Page 8218 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Wiring Harness, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wiring Harness: > 56-32-02B > Sep > 97 > Steering Column - Intermittent Click Noise/Snap Steering Column Bearing: All Technical Service Bulletins Steering Column - Intermittent Click Noise/Snap File In Section: 3 - Steering/Suspension Bulletin No.: 56-32-02B Date: September, 1997 Subject: Intermittent Steering Column Snap or Click Noise when Turning (Install New Upper Bearing Spring) Models: 1994-96 Buick Century, LaSabre, Park Avenue, Regal, Roadmaster 1995-96 Buick Riviera 1994-96 Cadillac Concours, DeVille, Eldorado, Fleetwood, Seville 1994-96 Chevrolet Camaro, Caprice, Corvette, Lumina, Lumina APV 1995-96 Chevrolet Monte Carlo 1994-96 Oldsmobile Cutlass Ciera, Cutlass Supreme, Eighty Eight, Ninety Eight, Silhouette 1995-96 Oldsmobile Aurora 1994-96 Pontiac Bonneville, Firebird, Grand Prix, Trans Sport with Tilt Steering Columns 1995-96 Chevrolet and GMC C/K, S/T Trucks 1994-96 Chevrolet and GMC M/L, G Vans with Tilt Steering Columns This bulletin is being revised to correct the truck models and part number descriptions. Please discard Corporate Bulletin Number 56-32-02A, dated April, 1996 (Section 3 Steering/Suspension). Condition Some owners may comment on an intermittent steering column snap or click noise while turning. The snapping or clicking may also be felt in the steering wheel. Cause The upper bearing race seat may, under some turning conditions, move in an axial direction along the upper steering shaft. The noise is a result of the inner race seat hanging up on the shaft and then suddenly releasing causing a snapping or clicking noise. Correction A new upper bearing spring with increased stiffness has been developed and should- be installed in the steering column. The new spring will increase the preload between the upper bearing inner race seat and the upper steering shaft. To accommodate the new spring with increased stiffness, the cancel cam will also need to be replaced. The new spring and cancel cam, along with a retainer ring and an upper bearing inner race seat are included in the parts kit listed below. Service Procedure Follow the instructions given in Section 3F5 of the appropriate Service Manual and those contained in kit. Be sure to use all parts supplied in the service kit. Parts Information Part Number Description 26059701 1994-96 A/B/C/D/E/F/H/K/U/W 26059701 1994-95 M/L/G Vans 26059702 1995-96 Buick "G" 26059703 1995-96 Oldsmobile "G" 26059704 1995-96 C/K, S/T Truck 26059704 1996 MIL/G Vans (both styles of G Van) 26059705 1994-96 "Y" Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Wiring Harness, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wiring Harness: > 56-32-02B > Sep > 97 > Steering Column - Intermittent Click Noise/Snap > Page 8224 Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Automatic Transmission/Transaxle > Wiring Harness, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wiring Harness: > 56-32-02B > Sep > 97 > Steering Column - Intermittent Click Noise/Snap > Page 8230 Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Clutch, M/T > Clutch Hydraulic System > Clutch Master Cylinder > Component Information > Service and Repair Clutch Master Cylinder: Service and Repair Fig. 2 Clutch Master Cylinder Removal. Clutch Slave Cylinder - Bleed Screw and Quick Connect Coupling NOTE: If servicing a vehicle that requires master cylinder, reservoir or tubing replacement a complete pre-filled, pre-bled unit must be installed. SPECIAL TOOL REQUIRED (or equivalent) - J-36221, Quick connect coupling disengagement tool. REMOVE OR DISCONNECT 1. Push rod from clutch pedal. 2. Clutch line from the concentric slave cylinder quick connect coupling using one of the following methods: - Use two small flat head screw drivers at 180° from each other to depress the white plastic sleeve on the quick connect coupling to separate the clutch line from the concentric slave cylinder. - Use tool J-36221 to depress the white plastic sleeve on the quick connect coupling to separate the clutch line from the concentric slave cylinder. 3. Tubes and clips from wiring harness bracket and sheet metal. 4. Master cylinder from cowl panel, rotating 45° clockwise. INSTALL OR CONNECT 1. Master cylinder to cowl panel by holding master cylinder at 45° angle and rotating counterclockwise. Use care not to over rotate master cylinder or damage may occur. 2. Clutch line to the concentric slave cylinder quick connect coupling. 3. Tubes and clips to wiring harness bracket and sheet metal. 4. Push rod to the clutch pedal. 5. Fill reservoir with GM Delco Supreme No. II(R) Brake Fluid or equivalent, (if required). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Clutch, M/T > Clutch Hydraulic System > Clutch Slave Cylinder > Component Information > Service and Repair Clutch Slave Cylinder: Service and Repair Concentric Slave Cylinder REMOVE OR DISCONNECT 1. Transmission, refer to Manual Transmission/Transaxle / Service and Repair. 2. Bolts securing the concentric slave cylinder to the clutch housing shaft. 3. Slave cylinder from the transmission input shaft. 4. Bearing from slave cylinder. INSTALL OR CONNECT 1. Bearing to slave cylinder. 2. Slave cylinder to the transmission input shaft. Ensure that the bleed screw and coupling are positioned with the transmission ports. 3. Two bolts securing the concentric slave cylinder to the clutch housing shaft and tighten to 8 Nm (71 lb in). 4. Transmission. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Clutch, M/T > Clutch Linkage > Component Information > Description and Operation Clutch Linkage: Description and Operation The clutch control system consists of a clutch master cylinder, slave cylinder and a connecting hose. The clutch master cylinder is operated directly by the clutch pedal. When the clutch pedal is pressed down, hydraulic fluid under pressure from the clutch master cylinder flows into the actuator. The actuator piston engages the clutch fork which moves the release bearing into contact with the diaphragm spring fingers to disengage the clutch. The hydraulic clutch system locates the clutch pedal height and provides automatic clutch adjustment. No adjustment of clutch linkage or pedal position is required. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Clutch, M/T > Clutch Linkage > Component Information > Description and Operation > Page 8242 Clutch Linkage: Testing and Inspection 1. Inspect slave cylinder and clutch pedal travel. 2. Clutch pedal travel should be approximately 8.3 inches, and slave cylinder rod should have a minimum of 1 inch travel, measured at the clutch fork. 3. Inspect pedal bushings for binding and excessive wear, and the fork for damage, wear and proper lubrication. Replace components that are damaged or worn. 4. With engine running at normal operating temperature, hold clutch pedal approximately 1/2 from floor mat, wait approximately nine seconds and move shift lever between First and Reverse several times. 5. If shift is not smooth, bleed system and recheck operation. 6. If shift is still not smooth, inspect clutch components and repair or replace as needed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Clutch, M/T > Clutch Linkage > Component Information > Description and Operation > Page 8243 Clutch Linkage: Adjustments These vehicles are equipped with a self-adjusting hydraulic clutch unit. There is no provision for adjustment. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Clutch, M/T > Clutch Linkage > Component Information > Description and Operation > Page 8244 Clutch Linkage: Service and Repair 1. Fill master cylinder, as needed with new brake fluid conforming to DOT 3 specification. 2. Raise and support vehicle and remove slave cylinder attaching bolts. 3. Hold slave cylinder at approximately 45 degrees angle with bleed valve at highest point. 4. Fully depress clutch pedal, then open bleed valve. 5. Close bleed valve, then release clutch pedal. Do not release clutch pedal with bleed valve open as air will be drawn into hydraulic system. 6. Repeat Steps 4 and 5 until all air is evacuated from system. Check and refill master cylinder at regular intervals during procedure to prevent air from being drawn into system through master cylinder. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Clutch, M/T > Clutch Pedal Assembly > Component Information > Service and Repair Clutch Pedal Assembly: Service and Repair Push Rod REMOVE OR DISCONNECT 1. Push rod from the clutch pedal. 2. Clutch pedal by pushing in the two spring loaded bushings. INSTALL OR CONNECT 1. Depress both spring loaded bushings and position into support. Bushings will spring (pop) out and hold pedal in place. 2. Push rod from the clutch pedal. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Continuously Variable Transmission/Transaxle, CVT > Shift Interlock, CVT > Component Information > Technical Service Bulletins > A/T - Shift Lock Control Feature Function Shift Interlock: Technical Service Bulletins A/T - Shift Lock Control Feature Function Bulletin No.: 03-07-30-043A Date: May 25, 2006 INFORMATION Subject: Information Regarding Automatic Transmission Shift Lock Control Function Models: 2007 and Prior Passenger Cars and Trucks (Including Saturn) 2007 and Prior HUMMER H2, H3 2005-2007 Saab 9-7X with Automatic Transmission Supercede: This bulletin is being revised to add models and model years. Please discard Corporate Bulletin Number 03-07-30-043 (Section 07 - Transmission/Transaxle). This bulletin is being issued to better explain how the Automatic Transmission Shift Lock Control (formerly known as Brake Transmission Shift Interlock (BTSI)) feature is intended to operate. Revised wording regarding the shift lock control system began appearing in the Owner Manuals beginning with the 2004 model year. The shift lock control feature was intended to prevent drivers from shifting out of Park with the vehicle running without the brakes applied. However, if the ignition switch is in the Accessory (ACC) position, it may be possible on some vehicles to move the shift lever out of Park WITHOUT first activating the brake. The shift lock control system is ONLY active when the ignition switch is in the RUN or ON position. This means that when the ignition switch is in the RUN or ON position, the shift lever cannot be moved out of the Park position without activating the brake. Some owners may feel that the shift lock control system prevents an unattended child from moving the vehicle. Please stress to owners, as stated in the Owner Manual, that children should NEVER be left unattended in a vehicle, even if the ignition key has been removed from the vehicle. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Adjustments > Dana/Spicer Full Floating Axle Differential Carrier: Adjustments Dana/Spicer Full Floating Axle Fig. 3 Spreading differential carrier Fig. 19 Gear tooth contact inspection 9-3/4 INCH RING GEAR AXLE 1. Place differential assembly with pinion into housing. 2. Install bearing caps in proper position and tighten just enough to retain in place. 3. Install dial indicator on carrier with indicator button contacting back of ring gear. 4. Position two screwdrivers between bearing cup and housing on ring gear side of case and pry ring gear into mesh with pinion gear as far as possible. 5. Set dial indicator to ``0'' with force still applied to gears. 6. Reposition screwdrivers on opposite side of ring gear, then pry ring gear as far as possible and note indicator reading. Repeat sequence several times until same reading is obtained. This reading indicates amount of shims necessary between differential case and differential bearing on ring gear side. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8258 7. Remove differential bearing from ring gear side, then install proper amount of shims and reassemble bearing. 8. Remove differential bearing from opposite side of ring gear. Subtract size of shim pack installed on ring gear side of case from reading obtained in step 11 of ``Differential Overhaul'' procedure. Add an additional .015 inch to this figure to compensate for preload and backlash. 9. Assemble proper amount of shims as indicated in step 8, then install side bearing. 10. Spread differential carrier, Fig. 3, then install differential bearing outer races and position differential case into carrier. 11. Install differential bearing caps and tighten cap screws finger tight. 12. Rotate differential assembly and tap case with a soft-faced hammer to seat case in carrier. 13. Remove spreader tool and torque cap bolts to 85 ft. lbs. 14. Install dial indicator and check ring gear backlash at four equidistant points on the ring gear. Backlash must measure .004-.009 inch and must not vary more than .002 inch between checking points. If backlash is not within specifications, adjust differential bearing shim pack as necessary. 15. Ensure ring gear teeth are clean and free from oil, then coat drive and coast face of each tooth with suitable marking compound. 16. Apply braking force to ring gear, then turn pinion to rotate ring gear one complete revolution in each direction. Accurate contact pattern cannot be obtained unless gears are ``loaded'' when rotated. 17. Examine gear tooth contact pattern, referring to Fig. 6, and correct assembly adjustments as needed. 18. Install housing covers, using a new gasket, and torque attaching bolts to 35 ft. lbs. 19. Install rear universal joint, on rear drive axles, then the axle shafts. 20. Fill axle with specified lubricant. 10-1/2 INCH RING GEAR AXLE 1. Install differential case, with side bearings and cups in position, into carrier. 2. Place the smallest of original shims between bearing cup and carrier on ring gear side of case. This shim will act as a ``gauging'' shim. 3. Install bearing caps in proper position and tighten just enough to retain in place. 4. Install a dial indicator on ring gear side of carrier with indicator button contacting back of ring gear. 5. Position two screwdrivers between bearing cup and housing on side opposite ring gear. 6. Apply force to screwdrivers to move differential case as far as possible toward the indicator. 7. Set dial indicator to ``0'' with force still applied to screwdrivers. 8. Reposition screwdrivers on ring gear side of case, then force ring gear into mesh with drive pinion and note dial indicator reading. Repeat sequence several times until same reading is obtained. Add this reading to ``gauging'' shim thickness to determine shim required on ring gear side of case. 9. Remove ``gauging'' shim and install correct thickness shim between bearing cup and carrier on ring gear side of case. 10. To determine correct dimension for remaining shim, subtract size of shim already installed from reading obtained in step 10 of ``Differential Overhaul'' procedure. Add an additional .006 inch to this figure to compensate for preload and backlash. 11. Spread differential carrier, Fig. 3, then install shim between bearing cup and carrier. 12. Remove spreader tool and dial indicator, then install bearing caps and torque cap bolts to 85 ft. lbs. 13. Install dial indicator and check ring gear backlash at four equidistant points on the ring gear. Backlash must measure .004-.009 inch and must not vary more than .002 inch between checking points. If backlash is not within specifications, adjust differential bearing shim pack as necessary. If backlash is less than specifications, decrease shim on ring gear side and increase shim on opposite side an equal amount. If backlash exceeds specifications, increase shim on ring gear side and decrease shim on opposite side an equal amount. 14. Ensure ring gear teeth are clean and free from oil, then coat drive and coast face of each tooth with suitable marking compound. 15. Apply braking force to ring gear, then turn pinion to rotate ring gear one complete revolution in each direction. Accurate contact pattern cannot be obtained unless gears are ``loaded'' when rotated. 16. Examine gear tooth contact pattern, referring to Fig. 6, and correct assembly adjustments as needed. 17. Install housing cover, using a new gasket, and torque attaching bolts to 35 ft. lbs. 18. Install rear universal joint, then the axle shafts. 19. Fill axle with specified lubricant. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8259 Differential Carrier: Adjustments Timken/Rockwell - 12 Inch Ring Gear Final Assembly & Adjustment DRIVE PINION INSTALLATION 1. Using micrometer or vernier gauge, measure and record thickness of original shim pack. 2. Check P.C. number on original pinion. If number is positive, subtract it from original shim pack thickness. If number is negative, add it to original shim pack thickness. Record resulting value. 3. Check P.C. number on new pinion. If number is positive, add it to value obtained in step 2. If number is negative, subtract it from value obtained in step 2. 4. Figure obtained in step 3 indicates thickness of new shim pack to be used. 5. Position correct shim pack between pinion cage and carrier. Use a minimum of 3 shims per pack. If pack is made up from various thicknesses of shims, place thinnest shims on either side of pack. 6. Install pinion and cage assembly with shims into carrier and tap into position with soft mallet. 7. Install pinion cage cap screws, torquing to 35 ft. lbs. DIFFERENTIAL CASE INSTALLATION 1. Temporarily install bearing cups, threaded adjusting rings if used, and bearing caps, torquing cap screws to 115-140 ft. lbs. 2. If bearing cups are not of a hand push fit in bores, bores must be reworked with a scraper or emery cloth until a hand push fit is obtained. Use a blued bearing cup as a gauge and check the fits as work progresses. When cups fit properly, remove bearing caps. 3. After checking related parts, coat differential bearing cones and caps with rear axle lubricant. 4. Place cups over assembled bearing cones and position differential assembly in carrier. 5. Insert bearing adjusting nuts and turn hand-tight against bearing cups. 6. Install bearing caps in correct location as marked and tap lightly in position. If bearing caps cannot be properly seated bearing adjusters may be cross-threaded. Remove bearing caps and reposition adjusting nuts as needed. Do not force bearing caps into position as carrier, caps and adjusting nuts will be damaged. 7. Install bearing cap bolts or nuts and washers, if used, then torque fasteners to 115-140 ft. lbs. Fig. 8 Side Bearing Preload Adjustment Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8260 Fig. 9 Ring Gear & Pinion Backlash Adjustment SIDE BEARING PRELOAD & BACKLASH ADJUSTMENT 1. Using dial indicator at back face of ring gear, Fig. 7, loosen bearing adjusting nut on side opposite gear only enough to notice endplay on dial indicator. 2. Tighten same adjusting nut only enough to obtain zero endplay. 3. Check gear for runout. If runout exceeds .008 inch, remove differential and check for cause. 4. Tighten adjusting nuts one notch each from zero endplay to preload differential bearings. 5. Mount dial indicator with plunger contact bearing against ring gear tooth, Fig. 8. 6. Hold pinion and rock ring gear, reading backlash from dial indicator. 7. If backlash is not within specifications, adjust as follows. If ring gear and pinion are reused, lash should be adjusted to value measured prior to disassembly. a. If backlash is greater than specified, loosen nut in ring gear tooth side and tighten opposite nut an equal amount. b. If backlash is less than specified, loosen nut on back side of ring gear and tighten nut on gear face side an equal amount. Adjusting nuts must be rotated equally, in opposite directions, in order to maintain proper side bearing preload. 8. Install adjuster locks to secure adjustment. Fig. 10 Gear Tooth Contact Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8261 GEAR TOOTH CONTACT INSPECTION 1. Ensure that ring gear is clean and free from oil, then coat coast and drive face of each ring gear tooth with suitable marking compound. 2. Brake ring gear to ``load'' gears, then turn pinion in order to rotate ring gear one full revolution in each direction. Satisfactory contact pattern cannot be obtained unless gears are ``loaded.'' Excessive rotation of gears is not recommended. 3. Inspect tooth contact pattern referring to Fig. 9, and correct assembly adjustments, as needed to obtain correct pattern. 4. Clean marking compound from gears. THRUST SCREW INSTALLATION & ADJUSTMENT 1. Remove carrier from stand and position with back face of hypoid or spiral bevel gear upward. 2. Remove thrust screw and locknut. 3. Install thrust screw and locknut and tighten thrust screw enough to locate thrust block firmly against back face of hypoid gear. 4. Loosen thrust screw 1/4 turn and lock securely with nut. 5. Check to ensure minimum clearance of .10 inch during full rotation of bevel gear. DIFFERENTIAL CARRIER, INSTALLATION 1. Ensure that housing is clean and free from dirt and foreign material. 2. Inspect housing for damage and distortion, and repair or replace as needed. Remove burrs from machined surfaces using suitable stone or file. 3. Install new gasket over housing studs. If RTV sealer is used, ensure that both mating surfaces are clean and free from oil, then apply a continuous bead of sealer, 1/8 inch wide, completely around one mating surface, circling all bolt holes or studs. 4. Raise carrier assembly with suitable jack, roll assembly onto studs, then install 4 evenly spaced flat washers and nuts to hold assembly. 5. Install nuts and lock washers on any studs shrouded by housing webs, then evenly tighten 4 evenly spaced nuts to draw carrier into housing. Do not drive carrier into housing by tapping flange as flange will be distorted. 6. Install lock washers under all retaining nuts, then evenly tighten all nuts. 7. Install axle shafts and connect driveshaft to companion flange. 8. Fill housing with specified lubricant. Side Bearing Preload & Backlash Fig. 8 Side Bearing Preload Adjustment Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8262 Fig. 9 Ring Gear & Pinion Backlash Adjustment 1. Using dial indicator at back face of ring gear, Fig. 8, loosen bearing adjusting nut on side opposite gear only enough to notice endplay on dial indicator. 2. Tighten same adjusting nut only enough to obtain zero endplay. 3. Check gear for runout. If runout exceeds .008 inch, remove differential and check for cause. 4. Tighten adjusting nuts one notch each from zero endplay to preload differential bearings. 5. Mount dial indicator with plunger contact bearing against ring gear tooth, Fig. 9. 6. Hold pinion and rock ring gear, reading backlash from dial indicator. 7. If backlash is not within specifications, adjust as follows. If ring gear and pinion are reused, lash should be adjusted to value measured prior to disassembly. a. If backlash is greater than specified, loosen nut in ring gear tooth side and tighten opposite nut an equal amount. b. If backlash is less than specified, loosen nut on back side of ring gear and tighten nut on gear face side an equal amount. Adjusting nuts must be rotated equally, in opposite directions, in order to maintain proper side bearing preload. 8. Install adjuster locks to secure adjustment. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8263 Differential Carrier: Adjustments Corporate and Eaton Final Assembly and Adjustment Fig. 19 Gear tooth contact inspection 1. Ensure that pinion depth and bearing preload are properly adjusted. 2. Install differential case assembly and selected side bearing shims. Refer to Side Bearing Preload & Backlash. See: 7 1/2 & 7 5/8 Inch Ring Gear/Side Bearing Preload & Backlash 3. Install bearing caps in proper position and torque cap bolts to 55 ft. lbs. 4. Rotate assembly to ensure that bearings are properly seated. 5. Mount dial indicator on housing with plunger bearing against tooth on ring gear, Fig. 18. Use small contact button on indicator plunger so that contact can be made at heel end of tooth and position dial indicator with plunger in line with gear rotation and perpendicular to gear tooth. 6. Hold pinion stationary and rock ring gear back and forth while reading backlash on indicator. 7. Check backlash at 3 evenly spaced positions around ring gear and record readings. If backlash varies by more than .002 inch at any position, check ring gear installation and runout, and correct as needed. 8. If backlash is not within specifications, remove differential case assembly and bearing shims keeping shims in order. If ring gear and pinion are Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8264 being reused, backlash should be adjusted as close as possible to value measured prior to disassembly. 9. Backlash is adjusted by increasing thickness of one shim while decreasing thickness of opposite side shim by the same amount in order to maintain proper side bearing preload. Select shims to adjust backlash as follows: a. If backlash is excessive, decrease thickness of shim on gear tooth side and increase thickness of shim on opposite side by the same amount. b. If backlash is less than specified, increase thickness of shim on gear tooth side while decreasing thickness of opposite shim by the same amount. On models with 7-1/2 & 7-5/8 inch ring gear, each .002 inch change in shim thickness alters backlash by .001 inch. On models with 8-1/2 and 8-5/8 inch ring gear, each .003 inch change in shim thickness alters backlash by .002 inch. 10. Reinstall differential assembly, shims and bearing caps, torque bearing cap bolts to 55 ft. lbs., then recheck backlash and adjust as needed. 11. If side bearing preload was set to zero during side bearing preload adjustment, proceed as follows: a. Remove both bearing caps and shim packs, keeping shim packs in respective left or right positions. b. Select shim .004 inch thicker than one removed from left side, insert shim between left bearing race and spacer, then install left bearing cap with bolts hand tight. c. Select shim .004 inch thicker than one removed from right side and install shim between right bearing race and spacer using suitable driver. d. Install right bearing cap and torque all cap bolts to 55 ft. lbs. 12. Ensure that ring gear teeth are clean and free from oil, then coat both drive and coast side of each tooth with suitable marking compound. 13. Apply braking force to ``load'' ring gear, then rotate driveshaft yoke with wrench so that ring gear rotates one full revolution in each direction. Test made without ``loading'' gears will not yield satisfactory pattern, and excessive rotating of gears is not recommended. 14. Compare gear tooth pattern with Fig. 19, and correct assembly adjustments as needed. 15. When proper gear tooth contact pattern has been obtained, clean marking compound from gears, install cover and new gasket and fill housing with specified lubricant. Side Bearing Preload & Backlash On these models, side bearing preload should be set before pinion is installed. If pinion is installed, remove ring gear. 1. Ensure bearing bores in housing and bearing caps are clean and free from burrs. 2. Measure production shims or service spacer and shim packs removed during disassembling to determine approximate thickness of shims needed for installation. Do not reuse cast iron production shims as they may break during installation. If service spacers and shims were previously installed, they can be reused. Fig. 12 Side Bearing Shim Selection Chart. Models W/7 1/2 & 7 5/8 Inch Ring Gear. 3. In addition to 0.170 inch service spacers for each side, refer to chart, Fig. 12, and select service shim thickness required based on measurements made in step 2. 4. Place outer races over side bearings, mount differential assembly in housing and insert service spacer between each bearing race and housing with chamfered edge against housing. 5. Install left bearing cap to retain case assembly and tighten bolts hand tight so that case can be moved while checking adjustments. A bearing cap bolt can be installed in lower right bearing cap hole to prevent case from dropping while performing shim adjustments. 6. Select one or two shims totaling thickness calculated in step 3 and insert shims between right bearing cap and service spacer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8265 Fig. 13 Side Bearing Clearance Inspection. 7. Insert progressively larger feeler gauges between shim and service spacer until noticeable increase in drag can be felt, pushing gauge down until it contacts housing bore to obtain proper reading, Fig. 13. Rotate case while inserting gauges to ensure even readings. 8. The gauge used just before additional drag is felt is correct thickness to obtain zero preload. By starting with a thin gauge a sense of feel can be obtained for the original light drag caused by the weight of the case, allowing the drag caused by the beginning of preload to be recognized. It will be necessary to work case in and out and to the left in order to insert feeler gauges. Insert feeler gauges as shown in Fig. 13, to ensure accurate measurement. 9. When the proper gauge thickness has been determined to obtain zero preload, remove bearing cap, case assembly service spacers and shim pack. 10. Select two service shims of approximate equal thickness whose total thickness is equal to the thickness of the shims installed in step 6 plus the thickness of the feeler gauge used to obtain zero preload. 11. Shims selected during this procedure allow differential assembly to be installed at zero preload, the equivalent of a slip-fit in case, during backlash adjustment. Final preload is not added until backlash has been adjusted. Final Assembly and Adjustment Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8266 Fig. 19 Gear tooth contact inspection 1. Ensure that pinion depth and bearing preload are properly adjusted. 2. Install differential case assembly and selected side bearing shims. Refer to Side Bearing Preload & Backlash. See: 7 1/2 & 7 5/8 Inch Ring Gear/Side Bearing Preload & Backlash 3. Install bearing caps in proper position and torque cap bolts to 55 ft. lbs. 4. Rotate assembly to ensure that bearings are properly seated. 5. Mount dial indicator on housing with plunger bearing against tooth on ring gear, Fig. 18. Use small contact button on indicator plunger so that contact can be made at heel end of tooth and position dial indicator with plunger in line with gear rotation and perpendicular to gear tooth. 6. Hold pinion stationary and rock ring gear back and forth while reading backlash on indicator. 7. Check backlash at 3 evenly spaced positions around ring gear and record readings. If backlash varies by more than .002 inch at any position, check ring gear installation and runout, and correct as needed. 8. If backlash is not within specifications, remove differential case assembly and bearing shims keeping shims in order. If ring gear and pinion are being reused, backlash should be adjusted as close as possible to value measured prior to disassembly. 9. Backlash is adjusted by increasing thickness of one shim while decreasing thickness of opposite side shim by the same amount in order to maintain proper side bearing preload. Select shims to adjust backlash as follows: a. If backlash is excessive, decrease thickness of shim on gear tooth side and increase thickness of shim on opposite side by the same amount. b. If backlash is less than specified, increase thickness of shim on gear tooth side while decreasing thickness of opposite shim by the same amount. On models with 7-1/2 & 7-5/8 inch ring gear, each .002 inch change in shim thickness alters backlash by .001 inch. On models with 8-1/2 and 8-5/8 inch ring gear, each .003 inch change in shim thickness alters backlash by .002 inch. 10. Reinstall differential assembly, shims and bearing caps, torque bearing cap bolts to 55 ft. lbs., then recheck backlash and adjust as needed. 11. If side bearing preload was set to zero during side bearing preload adjustment, proceed as follows: a. Remove both bearing caps and shim packs, keeping shim packs in respective left or right positions. b. Select shim .004 inch thicker than one removed from left side, insert shim between left bearing race and spacer, then install left bearing cap with bolts hand tight. c. Select shim .004 inch thicker than one removed from right side and install shim between right bearing race and spacer using suitable driver. d. Install right bearing cap and torque all cap bolts to 55 ft. lbs. 12. Ensure that ring gear teeth are clean and free from oil, then coat both drive and coast side of each tooth with suitable marking compound. 13. Apply braking force to ``load'' ring gear, then rotate driveshaft yoke with wrench so that ring gear rotates one full revolution in each direction. Test made without ``loading'' gears will not yield satisfactory pattern, and excessive rotating of gears is not recommended. 14. Compare gear tooth pattern with Fig. 19, and correct assembly adjustments as needed. 15. When proper gear tooth contact pattern has been obtained, clean marking compound from gears, install cover and new gasket and fill housing with specified lubricant. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8267 Side Bearing Preload & Backlash This procedure is performed after pinion assembly has been installed, and requires use of gauging tool No. J-22779 or equivalent. If gauging tool is not available, side bearing shim thicknesses can be determined by using procedure for 7 1/2 inch ring gears. 1. Ensure bearing bores and caps are clean and free of burrs. 2. Lightly lubricate differential case bearings, install outer races on proper bearings, install differential in housing and support to prevent falling. 3. Install retaining strap over left bearing cap, secure strap with cap bolts and evenly tighten bolts to obtain snug fit. Fig. 14 Side Bearing Preload Adjustment. 4. With ring gear tight against pinion (zero to 0.001 inch backlash), insert gauging tool No. J-22779, or equivalent, between left bearing race and housing, Fig. 14. 5. While oscillating tool, turn adjusting nut clockwise to force ring gear toward pinion until noticeable drag on tool can be felt, then tighten lock bolt on side of tool. 6. Insert a 0.170 inch service spacer between right bearing cap and housing, then select and install service shim that will easily slip between spacer and housing. Do not reuse cast iron production shims as they may crack during installation. If service spacers and shims were previously installed, they can be reused. 7. Insert progressively thicker feeler gauges between housing and service shim until slight drag can be felt when inserting gauge. Thickness of feeler gauge used to produce slight drag will be dimension C used in Fig. 14, to determine shim thickness. 8. Remove service spacer and shim, and gauge tool, without disturbing adjustment of tool. 9. Measure thickness of gauging tool at a minimum of three positions, average measurements and record average. 10. Add thicknesses of service spacer (A), shim (B) and feeler gauge (C), Fig. 14, and record sum. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8268 11. Apply dimensions obtained in steps 9 and 10 calculation shown in Fig. 14, to determine proper left and right shim thicknesses. 12. Install shim selected for left side first, then wedge right shim between bearing race and service spacer. Position shims so that chamfer is toward outside. If chamfer in right shim is not sufficient to allow installation without damaging spacer, grind or file chamfer prior to installation. If difficulty is encountered installing right shim, partially remove case, insert shim, slide shim and case into position, then seat shim using soft-faced hammer while rotating differential case. 13. Install bearing caps and tighten bolts to specifications, then check and adjust backlash as needed. Final Assembly and Adjustment 1. Lubricate side bearings, place outer races over bearings, then install differential assembly into housing. 2. Insert spacer/shim packs removed during disassembly between respective bearing race and housing or threaded adjuster. Fig. 10 Side Bearing Preload Adjustment 3. Push case away from adjuster, then tighten adjuster, Fig. 10, while rotating pinion and supporting case to seat bearings. 4. Back off adjuster and loosely install bearing caps. 5. Tighten adjuster against side bearing until no clearance exists, then tighten adjuster 3 additional notches to set preload. 6. Torque bearing cap bolts to 70 ft. lbs., install adjuster locks and tighten lock bolt hand tight. At this point, differential bearing preload is properly adjusted. If any further adjustments are required, ensure that proper preload remains established. Fig. 11 Ring gear & pinion backlash measurement 7. Mount suitable dial indicator on housing with plunger contact bearing against heel of ring gear tooth and plunger parallel to gear, Fig. 11. 8. Hold pinion and rock ring gear back and forth, observing backlash on dial indicator. 9. If backlash is not within specifications, adjust as follows: a. If backlash is excessive, replace shim on ring gear tooth side with one of less thickness while increasing thickness of opposite shim by an equal amount. b. If backlash is less than specified, increase thickness of shim on ring gear tooth side while reducing opposite shim by an equal amount. 10. After adjusting backlash, ensure that preload is properly established, then tighten adjuster lock bolt. 11. Ensure that ring gear teeth are clean and free from oil, then coat drive and coat face of each tooth with suitable marking compound. 12. Apply braking force to ring gear, then turn pinion to rotate ring gear one revolution in each direction. Accurate contact pattern cannot be obtained unless gears are ``loaded'' when rotated. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8269 Fig. 10 Gear Tooth Contact Inspection 13. Examine gear tooth contact pattern, referring to Fig. 12, and correct assembly adjustments as needed. 14. When proper gear tooth contact pattern has been established, install axle shafts, then torque pinion shaft lock screw to 20 ft. lbs. 15. Install rear cover and new gasket and fill axle with specified lubricant. Side Bearing Preload & Backlash PINION DEPTH ADJUSTMENT Fig. 9 Pinion Depth Gauge Installation If original ring gear and pinion assembly and rear pinion bearing are to be reused, original depth adjusting shim can be used. However, if ring gear and pinion or rear pinion bearing requires replacement, pinion depth must be adjusted using following procedures. 1. Install pinion bearing races to be used in housing using suitable driver. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8270 2. Lubricate pinion bearings and install bearings in races. 3. Mount depth gauging jig in housing noting the following. Use gauge assembly tool No. J-21777-01, Fig. 9, or suitable equivalent. Follow all tool manufacturer's recommendations when installing gauge assembly. a. Assemble gauge plate on preload stud. b. Hold pinion bearings in position, insert stud through rear bearing and pilot, then front bearing and pilot, install retaining nut and tighten nut hand tight. c. Rotate tool to ensure that bearings are properly seated. d. Hold preload stud and tighten nut until 20 inch lbs. torque is required to rotate stud. Tighten nut in small increments, checking rotating torque after each adjustment using suitable torque wrench. e. Mount side bearing discs on arbor, using step that corresponds to base of housing. f. Mount arbor and plunger assembly in housing ensuring that side bearing discs are properly seated, install bearing caps and tighten cap bolts to prevent bearing discs from moving. 4. Mount suitable dial indicator on arbor stud with indicator contact button bearing against top of arbor plunger. 5. Preload indicator 1/2 revolution, then secure to arbor stud in this position. 6. Place arbor plunger on gauge plate, rotate plate as needed so that plunger rests directly on button corresponding to ring gear size. 7. Slowly rock plunger rod back and forth across button while observing dial indicator. 8. At point on button where indicator registers greatest deflection, zero dial indicator. Perform steps 7 and 8 several times to ensure correct setting. 9. Once verified zero setting is obtained, swing plunger aside until it is clear of gauge plate button and record dial indicator reading. Indicator will now read required pinion depth shim thickness for ``nominal'' pinion. 10. Inspect rear face of drive pinion to be installed for a pinion code number. This number indicates in thousandths of an inch necessary modification of pinion shim thickness obtained in step 9. 11. Select pinion depth adjusting shim as follows: a. If pinion is stamped with a plus (+) number, add that number of thousandths to dimension obtained in step 9. b. If pinion is stamped with a minus (-) number, subtract that many thousandths from dimension obtained in step 9. c. If pinion is not stamped with plus or minus number, dimension obtained in step 9 is correct shim thickness. 12. Remove gauging tool and pinion bearings from housing. DRIVE PINION INSTALLATION 1. Install pinion bearing races in housing, if not previously installed, using suitable drivers to ensure that races are squarely seated. 2. Install selected shim on pinion shaft, lubricate rear pinion bearing with specified axle lubricant, then press rear bearing onto pinion using suitable spacers. 3. Install new collapsible spacer on pinion and insert pinion assembly into housing. 4. Lubricate front pinion bearing, install bearing in housing and tap bearing onto pinion shaft while assistant holds pinion in place. Old pinion nut and large washer can be used to draw front bearing onto pinion, but care must be taken not to collapse spacer if this method is used. 5. Install new pinion seal in housing, coat seal lips with grease, then mount driveshaft flange on pinion shaft, lightly tapping flange until several pinion shaft threads protrude. 6. Coat rear of pinion washer with suitable sealer, then install washer and new pinion nut and adjust preload to specifications. PINION BEARING PRELOAD ADJUSTMENT 1. Ensure that pinion and bearings are properly installed, as outlined. 2. Hold driveshaft companion flange with suitable tool, then alternately tighten pinion nut and rotate pinion until endplay is reduced to zero. 3. When endplay is reduced to zero, check pinion bearing preload by rotating pinion with suitable torque wrench. 4. Continue tightening pinion nut in small increments until specified bearing preload is obtained, rotating pinion and checking preload after each adjustment. Exceeding preload specification will compress collapsible spacer too far, requiring replacement of spacer. If preload specification is exceeded, spacer must be replaced and adjustment procedure must be repeated. Do not loosen pinion nut to reduce preload. 10 1/2 Inch Ring Gear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8271 Fig. 11 Pinion Depth shim Selection Chart Fig. 12 Side Bearing Preload Adjustment 1. Inspect head of drive pinion for pinion depth code number. Pinion may be stamped with either plus (+) or minus (-) number, indicating necessary modification of shim thickness to ensure proper engagement. 2. Compare depth code number with number on original pinion and use chart, Fig. 11, to select proper shim thickness for preliminary pinion depth adjustment as follows: a. Refer to thickness of shims removed during disassembly and add or subtract the value shown in chart. b. If original pinion, housing and rear bearing is to be reused, install shims of original thickness. 3. Position selected shim on axle housing, ensure that bolt holes are aligned, then install pinion assembly and torque retaining bolts to 65 ft. lbs. in crossing pattern. 4. Place outer races over differential case bearings, mount differential assembly in housing and install bearing caps, and tighten cap bolts snug. 5. Loosen right bearing adjusting nut and tighten left nut using suitable tool, Fig. 12, until ring gear contacts pinion. Do not force gears into contact. Tighten left nut just enough to obtain zero backlash without binding gears. 6. Loosen left adjusting nut approximately two notches, then install adjusting nut lock. 7. Firmly tighten right adjusting nut to force case against left nut, then loosen nut until clearance exists between right nut and bearing race. 8. Tighten right adjusting nut until it just contacts bearing race (zero preload), then tighten nut an additional two slots for used bearings or three slots for new bearings and secure position with locking retainer. At this point differential bearing preload is properly set. If any additional adjustments are required, ensure that preload remains as established. If one adjusting nut is loosened, the other nut must be tightened an equal amount in order to maintain preload. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8272 Fig. 13 Ring Gear & Pinion Backlash Measurement Fig. 14 Ring Gear & Pinion Tooth Contact Inspection 9. Mount suitable dial indicator on housing with plunger contact bearing against ring gear tooth, Fig. 13. 10. Hold pinion and rock ring gear back and forth, reading backlash from dial indicator. 11. Backlash should be .003-.012 inch, with .005-.008 inch the preferred setting. If original ring gear and pinion are used, set backlash to amount measured during disassembly to avoid changing gear contact pattern. 12. If backlash is not within specifications, proceed as follows: a. If backlash is greater than .012 inch, loosen right adjusting nut one notch and tighten left nut one notch. b. If backlash is less than .003 inch, loosen left adjusting nut one notch, then tighten right nut 1 notch. Always rotate adjusting nuts equal amounts in opposite directions to maintain differential bearing preload. c. Recheck backlash after each adjustment and correct as needed. d. When proper backlash has been obtained, install adjusting nut locks to secure adjustment. 13. Torque side bearing cap bolts to 135 ft. lbs., then check gear tooth contact pattern as follows. Gear tooth contact pattern must be checked to verify the correct relationship between ring gear and pinion in order to ensure that pinion depth is set properly. a. Ensure that ring gear is clean and free from oil. b. Apply suitable marking compound to coat drive and coast face of each ring gear tooth. c. Apply braking force to differential case in order to load gears, then turn pinion to rotate ring gear one full revolution in each direction. If Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8273 check is made without loading gears, a satisfactory pattern cannot be obtained. Excessive rotation of ring gear is not recommended. d. Inspect contact pattern on ring gear and correct differential adjustments, if necessary, as shown in Fig. 14. e. Clean marking compound from gears. 14. Install axle shafts, rear cover and gasket. 15. Install axle assembly in vehicle, then fill with specified lubricant. 12 1/4 Inch Ring Gear ASSEMBLY 1. Place new pinion bearing retainer gasket on retainer and install pinion assembly in carrier. Pinion assembly should be pressed into carrier to prevent damage to shims. 2. Install pinion bearing retainer bolts and lockwashers, torquing bolts to 165 ft. lbs. 3. Lubricate differential bearing rollers with engine oil and place outer races over bearings. 4. Install differential assembly in carrier and install adjusting nuts. Carefully slide adjusting nuts alongside bearings so that threads on nuts fit into threads in carrier. 5. Install differential bearing caps, ensuring that marks made during disassembly are aligned. 6. Install bearing cap bolts and lock washers and tighten until lockwashers just flatten out. BACKLASH & PRELOAD ADJUSTMENT 1. Loosen differential bearing cap bolts just enough so that bearing adjustment nuts may be turned with tool J-0972 or equivalent, then remove all lash between ring gear and pinion. 2. Back off lefthand adjusting nut one to two notches to a locking position. 3. Tighten righthand adjusting nut firmly to force differential into solid contact with lefthand adjusting nut. 4. Back off righthand adjusting nut until free of bearing, then retighten snugly against bearing. 5. Tighten righthand nut one to two additional notches to locking position. 6. Mount dial indicator on carrier and check backlash between ring gear and pinion. 7. If backlash exceeds .012 inch, loosen righthand adjusting nut one notch and tighten lefthand adjusting nut one notch. If backlash is less than .003 inch, loosen lefthand adjusting nut one notch and tighten righthand adjusting nut one notch. 8. Torque bearing cap bolts to 205 ft. lbs. 9. Install side bearing adjusting nut locks and torque to 15 ft. lbs. RING GEAR THRUST PAD ADJUSTMENT 1. Inspect bronze tip of thrust pad for wear, replacing as necessary. 2. Install thrust pad and tighten screw until bronze tip engages back face of ring gear while rotating gear. 3. Back off screw 1/12 turn and torque locknut to 135 ft. lbs. Ensure that screw does not turn during locking process CASE & DRIVE PINION INSTALLATION 1. Clean out axle housing and cover and install new gasket on axle housing. 2. Assemble differential carrier to axle housing, then install lockwashers and bolts, torquing bolts to 85 ft. lbs. 3. Install axle housing inspection cover, if removed, with new gasket. 4. Assemble rear universal joint. 5. Install axle shafts. Refer to individual truck chapters. 6. Fill axle to bottom of filler hole with suitable lubricant. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner Differential Carrier: Service and Repair Borg Warner 1. If removing ring gear, clamp case in a vise so jaws are 90° to pinion shaft holes and remove ten ring gear retaining bolts. 2. Partially install two bolts on opposite sides of ring gear. 3. Remove ring gear from case by alternately tapping on bolts. Do not pry between case and ring gear. Fig. 4 Exploded View Of Cone Type (Borg-Warner) Locking Differential. 4. Remove differential case half attaching bolts, Fig. 4. 5. Lift cap half of case from flange half. Remove clutch cone/side gears, spring blocks, preload springs, pinion gears and shaft. Mark each clutch cone/side gear and pinion gear so they can be reinstalled in their original position. 6. Clean and inspect all parts and replace as necessary. Slight grooves or scratches, indicating passage of foreign material, are permissible and normal. If case or clutch cone/side gear are damaged, it is necessary to replace case assembly. All others parts are serviceable. 7. Install proper cone/gear assembly into position in cap half of case. 8. Place one spring block in position over gear face, in alignment with pinion gear shaft grooves. Install pinion shaft, pinion gears and thrust washers into cap half or differential case in such a manner that pinion shaft retaining dowel can be inserted through pinion gear shaft into differential case. Be certain that pinon gears are installed in their original location. 9. Insert five springs into spring block that is already installed in case, then place second spring block over springs. 10. Install second cone/gear assembly face down on spring block so that gear will mesh with pinion gears. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8276 Fig. 5 Differential Case Bolt Torque Sequence. 11. Install flange half of differential case over cone, insert case bolts finger tight. Tighten bolts one turn at a time in sequence shown in Fig. 5. Then torque case bolts to 30 ft. lbs. 12. If ring gear was removed, position it so that holes line up with case holes. 13. Lubricate new attaching bolts with clean engine oil and install. 14. Tighten bolts evenly and alternately around the case. When all bolts are snug, torque evenly and alternately to 120 ft. lbs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8277 Differential Carrier: Service and Repair Corporate and Eaton Disassembly Axle can be disassembled either in or out of vehicle. If axle is disassembled in vehicle, it may be necessary to remove spare tire and/or disconnect shock absorbers to provide clearance for differential case removal. If axle assembly is allowed to hang, care must be taken not to damage or stretch flexible brake hose between axle and frame mounted lines. 1. Loosen rear cover bolts, break cover loose at bottom and drain lubricant, then remove cover and gasket. 2. Mount suitable dial indicator on bearing cap, and measure and record ring gear and pinion backlash. 3. Remove axles. Refer to Drive Axles, Bearings and Joints / Axle Shaft, Conventional Fixed/Floating / Service and Repair. See: Drive Axles, Bearings and Joints/Axle Shaft Assembly 4. Remove outer wheel bearings and seals, then pinion shaft lock screw and pinion shaft. 5. Roll pinion gears out of case with pinion thrust washers, then remove side gears and side gear thrust washers. Mark gears and differential case as left and right. 6. Remove differential bearing cap bolts, then bearing caps. Mark caps and housing as left and right. Fig. 1 Differential Case Assembly Removal. 7. Pry differential case assembly from axle housing, taking care not to damage cover gasket surface. Remove differential carrier by prying case from axle housing at differential window, Fig. 1. 8. Remove bearing outer races, shims and spacers. Mark races and bearings as left and right, then place them with cages. 9. Remove differential side bearings using tool No. J-8107-2 and tool No. J-22888 or their equivalents. 10. Remove ring gear bolts, then ring gear. Ring gear bolts are left handed threads. Do not pry ring gear from case as damage to gear and case will result. Drive ring gear off with a brass drift, if necessary. 11. Check drive pinion preload using suitable torque wrench and record reading. Inspect pinion assembly for looseness by moving it back and forth, looseness will indicate excessive bearing wear. 12. Hold driveshaft yoke with suitable tool and remove pinion nut and washer. 13. Remove driveshaft yoke with suitable puller. 14. Thread pinion nut halfway onto pinion, temporarily install rear cover, then tap pinion from bearings using large hammer and soft drift. 15. Remove pinion seal and front pinion bearing from housing. 16. Remove rear cover, then the drive pinion and rear bearing assembly from housing. 17. Discard collapsible preload spacer, press rear bearing from pinion, then remove depth adjusting shim and retain for assembly adjustment. 18. Remove bearing cups from axle housing using a hammer and punch in slots provided. Work cups out of housing evenly by moving punch back and forth between sides of cup. 19. Inspect components. Refer to Cleaning and Inspection. See: 7 1/2 - 8 5/8 Inch Ring Gear/Cleaning & Inspection Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8278 Fig. 19 Gear tooth contact inspection 1. Ensure that pinion depth and bearing preload are properly adjusted. 2. Install differential case assembly and selected side bearing shims. Refer to Side Bearing Preload & Backlash. See: Adjustments 3. Install bearing caps in proper position and torque cap bolts to 55 ft. lbs. 4. Rotate assembly to ensure that bearings are properly seated. 5. Mount dial indicator on housing with plunger bearing against tooth on ring gear, Fig. 18. Use small contact button on indicator plunger so that contact can be made at heel end of tooth and position dial indicator with plunger in line with gear rotation and perpendicular to gear tooth. 6. Hold pinion stationary and rock ring gear back and forth while reading backlash on indicator. 7. Check backlash at 3 evenly spaced positions around ring gear and record readings. If backlash varies by more than .002 inch at any position, check ring gear installation and runout, and correct as needed. 8. If backlash is not within specifications, remove differential case assembly and bearing shims keeping shims in order. If ring gear and pinion are being reused, backlash should be adjusted as close as possible to value measured prior to disassembly. 9. Backlash is adjusted by increasing thickness of one shim while decreasing thickness of opposite side shim by the same amount in order to maintain proper side bearing preload. Select shims to adjust backlash as follows: a. If backlash is excessive, decrease thickness of shim on gear tooth side and increase thickness of shim on opposite side by the same amount. b. If backlash is less than specified, increase thickness of shim on gear tooth side while decreasing thickness of opposite shim by the same amount. On models with 7-1/2 & 7-5/8 inch ring gear, each .002 inch change in shim thickness alters backlash by .001 inch. On models with 8 1/2 and 8 5/8 inch ring gear, each .003 inch change in shim thickness alters backlash by .002 inch. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8279 10. Reinstall differential assembly, shims and bearing caps, torque bearing cap bolts to 55 ft. lbs., then recheck backlash and adjust as needed. 11. If side bearing preload was set to zero during side bearing preload adjustment, proceed as follows: a. Remove both bearing caps and shim packs, keeping shim packs in respective left or right positions. b. Select shim .004 inch thicker than one removed from left side, insert shim between left bearing race and spacer, then install left bearing cap with bolts hand tight. c. Select shim .004 inch thicker than one removed from right side and install shim between right bearing race and spacer using suitable driver. d. Install right bearing cap and torque all cap bolts to 55 ft. lbs. 12. Ensure that ring gear teeth are clean and free from oil, then coat both drive and coast side of each tooth with suitable marking compound. 13. Apply braking force to ``load'' ring gear, then rotate driveshaft yoke with wrench so that ring gear rotates one full revolution in each direction. Test made without ``loading'' gears will not yield satisfactory pattern, and excessive rotating of gears is not recommended. 14. Compare gear tooth pattern with Fig. 19, and correct assembly adjustments as needed. 15. When proper gear tooth contact pattern has been obtained, clean marking compound from gears, install cover and new gasket and fill housing with specified lubricant. Cleaning & Inspection 1. Clean components in suitable solvent and blow dry with compressed air, noting the following: a. Do not use brush when cleaning bearings. b. Do not ``spin dry'' bearings, as bearings will be damaged. c. Lightly lubricate components after cleaning to retard corrosion. d. Keep all components in order to ensure proper assembly. 2. Inspect gears for cracks, chipped teeth, wear and scoring, and damaged bearing or mounting surfaces. Replace gears that are damaged or excessively worn. Ring gear and pinion must be replaced as an assembly. 3. Inspect differential case for cracks, damage, worn side gear bores and scored bearing surfaces and replace as needed. 4. Inspect housing for scored bearing mount surfaces, cracks and distortion, and replace as needed. 5. Inspect bearing rollers and races for pitting, scoring, overheating and damage. 6. Mate bearing with race and check operation. 7. Replace any bearing that is damaged, excessively worn or that fails to operate smoothly. 8. Mount differential case along with side bearings and ring gear in housing, and check runout with side bearings adjusted for zero preload and suitable dial indicator positioned against machined edge of ring gear. 9. If runout exceeds .003 inch, and gear cannot be repositioned to eliminate runout, ring gear and/or case should be replaced. Standard Fig. 2 Standard differential assembly exploded view 1. If side carrier bearings are to be replaced, remove bearings using suitable puller. 2. Remove differential pinion shaft lock bolt and the pinion shaft, Fig. 2. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8280 3. Remove differential pinions and thrust washers, side gears and side gear thrust washers, noting installation position for assembly. Keep thrust washers with respective gears. 4. Remove ring gear bolts, then the ring gear, driving ring gear from case using suitable drift and hammer. Ring gear bolts have lefthand threads. Do not pry between ring gear and case, as mating surfaces will be damaged. 5. Inspect components. Refer to Cleaning and Inspection. See: 7 1/2 - 8 5/8 Inch Ring Gear/Cleaning & Inspection 6. Install thrust washers on side gears and mount side gears in case. Lubricate all components with specified gear lubricant prior to assembly. 7. Position one differential pinion (less thrust washer) between side gears and rotate gears until pinion is directly opposite case loading opening. 8. Install other pinion with pinion shaft holes aligned, then rotate side gears and ensure that pinions align with shaft openings in case. 9. When pinions are properly aligned, rotate pinions toward loading opening just enough to allow thrust washer installation and install washers. 10. Align pinions with shaft opening in case, insert pinion shaft through case, install new lock bolt and torque bolt to 20 ft. lbs. 11. Ensure that ring gear and case mating surfaces are clean and free from burrs, mount gear on case, install 2 new retaining bolts at opposite sides of gear and alternately tighten bolts to draw gear on case. 12. Install remaining ring gear bolts hand tight and ensure that gear is squarely seated on case. Always use new bolts of proper type when installing ring gear. Do not reuse old bolts. 13. Alternately torque ring gear bolts to 80-95 ft. lbs. on models with 7 1/2 inch ring gear, 80 ft. lbs. on models with 8 1/2 inch ring gear or 60 ft. lbs. on models with 8 5/8 inch ring gear. 14. Press side bearings onto case. If old bearings are reused, ensure that bearings are installed in original position. Limited Slip Fig. 3 Chevrolet disc type limited slip differential exploded view 1. Remove ring gear and side bearings, then remove pinion shaft, Fig. 3. 2. Using a brass drift drive the preload spring from the case. 3. Support an axle shaft in a vise, and slide the case into the shaft, then turn the case to remove both pinions and thrust washers. 4. Remove the case from the axle shaft, then remove both side gears, clutch packs and shims. Mark the gears, clutch packs and shims for reinstallation in same position. 5. Inspect gears, bearings and case. Refer to Cleaning and Inspection. See: 7 1/2 - 8 5/8 Inch Ring Gear/Cleaning & Inspection 6. Inspect clutch plates and spacers, and replace if worn or overheated. 7. Replace preload spring if force required to compress spring to height of 1 5/16 inches is not 270-330 lbs. 8. Lubricate the clutch discs and plates with limited slip lubricant. 9. Alternately position clutch plates and discs on a side gear, beginning and ending with a clutch plate, Fig. 3. 10. Position the side gear, clutch pack and original shim into the case. 11. Install both pinion gears and thrust washers into the case, and install the pinion shaft. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8281 12. Install the case onto an axle shaft supported in a vise. 13. Insert a screwdriver between the pinion shaft and the face of the side gear. Force the screwdriver in until the clutch pack is compressed. 14. Check the backlash between the side gear and pinion gears. If backlash does not fall into the range of .005 inch to .008 inch, adjust the shim dimension as required. Increasing shim thickness will decrease backlash; decreasing shim thickness will increase backlash. Service shims are available from .070 inch to .122 inch in increments of .004 inch. 15. Remove the pinion shaft, pinion gears, side gear, clutch pack and shim from the case. 16. Install the opposite gear, clutch pack and original shim into the opposite side of the case. Place both pinion gears and thrust washers into place, and install the pinion shaft. 17. Follow the procedure in steps 12, 13, and 14 to determine the proper shim dimension. 18. When proper shim dimensions have been determined, remove pinion gears and pinion shaft and install both side gears, shims and clutch packs into case. 19. Mount the case onto the axle shaft locked in a vise. Place both pinions and thrust washers into position 180° apart and carefully ``roll in'' by turning the case on the shaft. A large ``C'' clamp may be used to apply slight compression against pinion gears to aid the ``rolling in'' procedure. 20. Tap the preload spring into place with a hammer. 21. Install the pinion shaft and lock screw. 22. Install the side bearings and ring gear using the procedure outlined for conventional units. 23. Place the differential unit in the carrier and adjust ring gear and pinion backlash, and gear tooth pattern. Limited Slip Fig. 6 Eaton limited slip differential exploded view 1. Remove pinion shaft lock screw and pull pinion shaft from case, Fig. 6. 2. Remove preload spring retainer and springs. 3. Rotate side gears until pinions are in open area of case and pick out pinions and thrust washers. 4. Remove a side gear, clutch pack and shims, noting shim location in case to aid in reassembly. Remove side gear clutch pack and shims from opposite side. If side gear or clutch pack cannot be removed readily, drive it out with a brass drift. 5. Remove clutch plate guides and separate shims and clutch plates from side gears. Keep clutch plates in their original location in clutch pack. 6. If pinion shaft, pinions or side gears are excessively scored, pitted or worn, replace parts affected. 7. Inspect clutch plates for scored, worn, cracked or distorted condition. If any of these conditions exist, new clutch plates must be installed. 8. Alternately position nine clutch plates on side gear, starting and ending with a plate with external lugs, Fig. 6. 9. Install two clutch guides over clutch plate lugs. 10. Install same shims which were removed or an equal amount on clutch plate. 11. Repeat above steps on other clutch pack. 12. Install one side gear with clutch pack and shims in case. 13. Position two pinion gears and thrust washers on side gear and install pinion shaft. 14. Compress clutch pack by inserting a screwdriver or wedge between side gear and pinion shaft. 15. Install a suitable dial indicator with contact button against pinion gear. 16. Rotate pinion gear. Clearance should be .001 inch to .006 inch. 17. If clearance is more than .006 inch, add shims between clutch pack and case. If clearance is less than .001 inch, remove shims. A .002 inch shim will change clearance about .001 inch. Recheck clearance after adding or subtracting shims. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8282 18. Remove side gear and repeat procedure with remaining clutch pack on opposite side of case. 19. Remove pinion shaft, pinions and thrust washers. 20. Install remaining side gear and clutch pack with correct shims in case. 21. Place pinion gears on side gears and rotate into correct position. 22. Compress preload springs and drive preload retainer and springs between side gears. 23. Insert thrust washers behind pinion gears. 24. Install pinion shaft and retain with lock bolt, tightening lock bolt to 15-25 ft. lbs. 25. Check side gear splined hole to be certain it is in line with hole in preload spring retainer. Spring retainer can be moved slightly to correct alignment. Case Disassembly 1. Note position of governor and latching bracket for assembling, then remove side bearings and ring gear as outlined for standard differentials. Fig. 7 Governor & Latch Bracket Bushing Removal. 2. Remove governor assembly and latching bracket by pulling retaining bushings from case, Fig. 7. Pull latching bracket spring aside when removing bushings to prevent damage. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8283 Fig. 8 Exploded View Of Eaton Locking Differential. 3. Remove lock screw and pinion shaft, Fig. 8, then roll differential pinions to access window by turning side gears and remove pinions. 4. Remove pinion thrust washers and thrust block, keeping all components in order for assembling. 5. Remove right side gear, disc pack and shim assembly, and guide clips. 6. Remove left cam gear and disc pack assembly along with shim and guide clips. 7. Clean and inspect all components, keeping components in order for assembling. 8. Replace components that are damaged, deformed or excessively worn. Due to critical tolerances required for proper operation, the differential case cannot be serviced separately. If case is defective, the entire differential assembly must be replaced. In addition, internal clearances are such that shims, thrust block or gears should not be replaced unnecessarily, even if slight wear patterns are evident. If shims, thrust block or side gears must be replaced, measurement and replacement procedures must be performed as outlined in order to maintain critical assembly clearances. Cam Gear Clutch Service Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8284 Fig. 8 Exploded View Of Eaton Locking Differential. 1. Remove retaining ring from end of cam gear, Fig. 8. 2. Remove discs and cam plate from gear, keeping all components in order. 3. Clean and inspect components, and replace any that are damaged, distorted or excessively worn. If cam gear must be replaced, refer to Shim Selection for shim selection procedures prior to case assembling. Refer to Shim Selection. See: 7 1/2 - 8 5/8 Inch Ring Gear/Overhaul/Eaton/Locking/Shim Selection 4. Position gear on flat surface with hub end up, and assemble cam plate onto gear with cam form down to mate with cam form on gear. 5. Assemble two eared discs, one splined disc and one wave washer on cam gear, starting with eared disc as shown in Fig. 8. 6. Alternately assemble three eared discs and two splined discs on cam gear hub, starting with eared discs. 7. Install retaining ring, ensuring that retainer is fully seated. Side Gear (RH) Clutch Service 1. Remove disc pack and shim from side gear, keeping components in order. 2. Clean and inspect components, and replace any that are damaged, deformed or excessively worn. If side gear must be replaced. refer to Shim Selection for shim selection prior to case assembly. If side gear hub is scored or worn, inspect bore in case and replace assembly if bore is damaged or worn. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8285 Fig. 8 Exploded View Of Eaton Locking Differential. 3. Alternately assemble eared discs and splined discs on side gear hub, starting with eared disc as shown in Fig. 8. 4. Install original shim or replacement shim of same thickness if original side gear is being used. Shim Selection Cam Gear Shim Selection 1. Install cam gear assembly in case using original thrust washer or washer of equal thickness. 2. Mount differential pinions and thrust washers in proper installed position in case, manually depress cam gear into bore and insert pinion shaft through case and pinion assemblies, and secure shaft with lockscrew. If pinion shaft cannot be inserted, it will be necessary to replace cam gear shim with one of less thickness. 3. Index one tooth of pinion gear nearest shaft lock-screw so that tooth points downward, perpendicular to case flange. 4. Wedge large tapered screwdriver between cam gear and pinion shaft to hold gear compressed in bore. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8286 Fig. 9 Differential Pinion Backlash Inspection. 5. Mount suitable dial indicator on case with pointer bearing against indexed differential pinion tooth, Fig. 9. 6. Ensure pinion is firmly pulled back in seat, then rock pinion back and forth, read backlash clearance from dial indicator and note reading. 7. Index tooth of opposite differential pinion as outlined in step 3, then repeat steps 5 and 6. 8. Replace cam gear assembly shim as needed to obtain differential pinion backlash of 0.010-0.018 inch. If cam gear is replaced, perform Thrust Block Selection procedure during case assembly to ensure proper case assembly clearances. Refer to Thrust Block Selection. See: 7 1/2 - 8 5/8 Inch Ring Gear/Overhaul/Eaton/Locking/Thrust Block Selection Side Gear Shim Selection When side gear is replaced, or if side gear shim is damaged and proper thickness must be determined, select proper side gear shim thickness by measuring backlash between side gear and differential pinions. Follow procedure outlined for "Cam Gear Shim Selection, using fully assembled side gear properly installed in case and select a shim that will provide 0.002-0.010 inch backlash between side gear and differential pinions. Thrust Block Selection If cam gear and/or side gear have been replaced, or if it is necessary to replace thrust block and original dimension cannot be determined, use the following procedure during differential case assembling to determine proper thrust block dimension. 1. Install cam gear and side gear assemblies in respective positions in case, insert differential pinion shaft through case bores and secure with lock screw. 2. Wedge large tapered screwdrivers or equivalent tools between cam gear and pinion shaft and side gear and pinion shaft to seat gears in case. Fig. 10 Side Gear Spread Inspection. 3. Using suitable gauge, measure distance between face of cam gear and face of side gear, Fig. 10, and record reading. Ensure gauge ends rest on gear faces, not gear teeth when measuring side gear spread. 4. Measure thickness of original thrust block at outer corner and record dimension. 5. Select thrust block with thickness zero to 0.006 inch less than side gear spread measured in step 3. If original thrust block is serviceable, but Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8287 does not provide the specified zero to 0.006 inch clearance, RH side gear can be shimmed to provide proper thrust block clearance as long as side gear backlash is maintained within the specified 0.002-0.010 inch. Differential Case Assembly 1. Install four clutch pack guide clips on cam gear clutch pack, using heavy grease to retain clips. Fig. 8 Exploded View Of Eaton Locking Differential. 2. Install cam gear assembly along with shim in flange end of case, Fig. 8. If cam gear has been replaced, perform shim selection procedure prior to installation. 3. Install four guide clips on assembled side gear clutch pack using grease to retain clips. 4. Install side gear assembly in case along with shim. If side gear has been replaced, perform shim selection procedure prior to installation. 5. Lock axle shaft in vise with sufficient portion of spline protruding from vise to engage side gear, then mount case assembly on axle and engage axle with side gear. 6. Install thrust washers on back of differential pinions using grease to adhere washers. 7. Install one pinion assembly through small case opening while simultaneously installing remaining pinion and thrust block through large opening. 8. Rotate assembly approximately 90° to position open side of thrust block toward small opening in case and pinions in proper installed position. If side gears and/or thrust block have been replaced, refer to Thrust Block Selection Procedure to ensure proper assembly clearances. Refer to Thrust Block Selection. See: 7 1/2 - 8 5/8 Inch Ring Gear/Overhaul/Eaton/Locking/Thrust Block Selection 9. Insert pinion shaft ensuring that pinion thrust washers are properly positioned, then install new lock screw and torque screw to 20 ft. lbs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8288 Fig. 11 Governor & Latching Bracket Installation. 10. Insert governor assembly and latching bracket into case, Fig. 11, positioning straight end of latching bracket spring over and to the outside of the engagement shaft to preload bracket against governor. 11. Press governor assembly bushing into case to a depth which will allow .004-0.020 inch shaft endplay. 12. Press latching bracket bushing into case to a depth which will provide zero to 0.003 inch shaft endplay. 13. Install ring gear and bearings as outlined for standard differentials. Always use new bolts of proper type when installing ring gear. Do not reuse old bolts. Disassembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8289 Fig. 1 Chevrolet 9-1/2 inch semi-floating drive axle w/standard differential exploded view. Full floating models similar Axle can be disassembled either in or out of vehicle. If axle is disassembled in vehicle it may be necessary to disconnect shock absorbers and lower housing to provide clearance for differential case removal. If housing is lowered care must be taken not to damage flexible brake hose between housing and frame. 1. Loosen rear cover bolts, break gasket seal and drain lubricant, then remove rear cover, Fig. 1. 2. Remove axle shafts. Refer to Drive Axles, Bearings and Joints / Axle Shaft, Conventional Fixed/Floating / Service and Repair. See: Drive Axles, Bearings and Joints/Axle Shaft Assembly/Service and Repair 3. On models with standard differential, rotate case and remove differential pinions and thrust washers, noting position for assembly. Keep all components in order so that any component reused can be installed in original position. 4. On all models, measure and record ring gear and pinion backlash to aid assembly. 5. Remove bolt securing threaded preload adjuster lock, lock, side bearing cap bolts and the side bearing caps. 6. Pry differential case assembly from housing taking care not to mar machined surfaces, then remove case, bearing races and shims. Place bearing races and shim packs with respective bearing caps. 7. Measure pinion rotating torque with suitable torque wrench. If no preload is present and play can be felt, pinion bearings may be defective. 8. Hold driveshaft companion flange with suitable tool and remove pinion nut and washer. 9. Remove companion flange with suitable puller. 10. Thread pinion nut half-way onto pinion, temporarily install rear cover, then tap pinion from front bearing using soft drift and hammer. 11. Pry pinion seal from housing, then remove front pinion bearing, cover, and pinion and rear bearing assembly. 12. Discard collapsible spacer, press rear bearing from pinion, remove depth adjusting shim and retain shim for assembly. 13. Drive pinion bearing races from housing, positioning suitable drift in recesses in case to prevent damage. Keep races with respective bearings and keep components in order for assembly. 14. Inspect components. Refer to Cleaning and Inspection and replace as needed. See: 9 1/2 Inch Ring Gear/Cleaning & Inspection Assembly 1. Lubricate side bearings, place outer races over bearings, then install differential assembly into housing. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8290 2. Insert spacer/shim packs removed during disassembly between respective bearing race and housing or threaded adjuster. Fig. 10 Side Bearing Preload Adjustment 3. Push case away from adjuster, then tighten adjuster, Fig. 10, while rotating pinion and supporting case to seat bearings. 4. Back off adjuster and loosely install bearing caps. 5. Tighten adjuster against side bearing until no clearance exists, then tighten adjuster three additional notches to set preload. 6. Torque bearing cap bolts to 60 ft. lbs., install adjuster locks and tighten lock bolt hand tight. At this point, differential bearing preload is properly adjusted. If any further adjustments are required, ensure that proper preload remains established. Fig. 11 Ring Gear & Pinion Backlash Measurement 7. Mount suitable dial indicator on housing with plunger contact bearing against heel of ring gear tooth and plunger parallel to gear, Fig. 11. 8. Hold pinion and rock ring gear back and forth, observing backlash on dial indicator. 9. If backlash is not within specifications, adjust as follows: a. If backlash is excessive, replace shim on ring gear tooth side with one of less thickness while increasing thickness of opposite shim by an equal amount. b. If backlash is less than specified, increase thickness of shim on ring gear tooth side while reducing opposite shim by an equal amount. 10. After adjusting backlash, ensure that preload is properly established, then tighten adjuster lock bolt. 11. Ensure that ring gear teeth are clean and free from oil, then coat drive and coat face of each tooth with suitable marking compound. 12. Apply braking force to ring gear, then turn pinion to rotate ring gear one revolution in each direction. Accurate contact pattern cannot be obtained unless gears are ``loaded'' when rotated. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8291 Fig. 12 Gear Tooth Contact Inspection 13. Examine gear tooth contact pattern, referring to Fig. 12, and correct assembly adjustments as needed. 14. When proper gear tooth contact pattern has been established, install axle shafts, then torque pinion shaft lock screw to 20 ft. lbs. 15. Install rear cover and new gasket and fill axle with specified lubricant. Cleaning & Inspection 1. Clean components in suitable solvent and blow dry with compressed air, noting the following: a. Do not use brush when cleaning bearings. b. Do not ``spin dry'' bearings as bearings will be damaged. c. Lightly lubricate components after cleaning to retard corrosion. d. Keep all components in order to ensure proper assembly. 2. Inspect gears for cracks, chipped or broken teeth, wear and scoring. Replace gears that are damaged or excessively worn. Ring gear and pinion must be replaced as an assembly. 3. Inspect differential case for cracks, damage, distortion, worn side gear bores and scored bearing surfaces, and replace as needed. 4. Inspect housing for scored bearing mount surfaces, cracks and distortion, and replace as needed. Ensure that housing is clean and free from foreign material. 5. Inspect bearing rollers and races for pitting, scoring, overheating and damage. 6. Mate each bearing with race and check operation. 7. Replace any bearing assembly that is damaged, excessively worn, or that fails to operate smoothly. 8. Mount differential case along with side bearings and ring gear in housing, adjust side bearings to zero preload and check ring gear runout with dial indicator bearing against machined edge of gear. 9. If ring gear runout exceeds .003 inch and gear cannot be repositioned to reduce runout, replace ring gear and/or differential case. Corporate - Standard 1. If case side bearings are to be replaced, remove bearings using suitable puller, ensuring that puller is properly seated in recesses in case. 2. Remove ring gear retaining bolts, then tap gear from case using suitable drift. Do not pry gear from case as machined surfaces will be damaged. 3. Remove side gears and thrust washers from case noting position for assembly. 4. Inspect components. Refer to Cleaning and Inspection. See: 9 1/2 Inch Ring Gear/Cleaning & Inspection Coat all components with specified axle lubricant prior to assembly. If components are to be reused, they must be installed in original position. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8292 Fig. 1 Chevrolet 9-1/2 inch semi-floating drive axle w/standard differential exploded view. Full floating models similar 5. Install side gears and thrust washers in case, Fig. 1. 6. Install thrust washers on differential pinions, using grease to adhere washers. 7. Position differential pinions in case 180° apart in mesh with side gears, then rotate side gears to roll pinions into position. 8. When pinions are aligned with shaft openings in case, install pinion shaft and temporarily secure shaft with new lock bolt. Do not torque lock bolt to specifications until axle shafts have been installed. Fig. 2 Ring gear installation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8293 9. Align ring gear with bolt holes in case and press on adapter plug J-8107-04 or equivalent, Fig. 2, to start gear on case pilot. 10. Install new ring gear bolts and tighten bolts alternately and evenly to draw gear onto case. New ring gear bolts must be used during assembly. Do not reuse ring gear bolts. 11. Ensure that ring gear is fully seated, then torque retaining bolts to 105 ft. lbs. 12. Position side bearings on case and seat bearings using suitable driver. When installing second bearing, support case with suitable pilot to prevent damaging cage of bearing already installed. Case Disassembly Fig. 3 Governor & latching bracket installation. Eaton locking differential Fig. 4 Governor & latching bracket bushing removal. Eaton locking differential Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8294 Fig. 5 Eaton locking differential exploded view 1. Note position of governor and latching bracket, Fig. 3, then remove side bearings and ring gear as outlined for standard differential. 2. Remove governor and latching bracket bushings using J-26252 or equivalent, Fig. 4, then the governor and latching bracket. Position latching bracket spring aside when removing governor bushing to prevent damage. 3. Drive stop pin from case using suitable drift, Fig. 5. 4. Remove differential pinion shaft lock bolt and the pinion shaft. 5. Roll out differential pinions and remove pinions and thrust washers, keeping components in order for assembly. 6. Remove right side gear, disc pack and shim, and guide clips. 7. Remove left cam gear, disc pack assembly, shim and guide clips. 8. Clean and inspect all components, keeping components in order for assembly, and replace components that are damaged, distorted or excessively worn. Due to critical tolerances required for proper operation, the differential case cannot be serviced separately. If case is defective, the entire differential assembly must be replaced. In addition, internal clearances are such that shims, thrust block or gears should not be replaced unnecessarily, even if slight wear patterns are evident. If shims, thrust block, cam gear thrust ring or side gears must be replaced, measurement and replacement procedures must be followed as outlined in order to maintain critical assembly clearances. Cam Gear Clutch Service 1. Measure and record overall length of cam gear assembly from front face of gear to back side of thrust ring, including shim. Fig. 6 Cam Gear Thrust Ring Removal. Eaton Locking Differential 2. With gear hub facing up, compress disc pack and insert jaws of suitable split ring bearing puller between thrust ring and top eared disc with bevel side of puller facing thrust ring, Fig. 6. 3. Support bearing remover in press and press cam gear from thrust ring using 1 3/4 inch diameter spacer. Keep all component in order as cam gear is removed. 4. Remove disc pack and cam plate from gear, clean and inspect components, and replace any that are damaged or excessively worn. Do not replace thrust ring and/or cam gear unless necessary. If ring or gear is excessively worn or scored, inspect bore in case. If case bore is scored, entire assembly must be replaced. If cam gear or thrust ring are replaced, shim thickness must be selected to provide original assembly dimension and proper differential pinion backlash. 5. Position cam gear on flat surface with hub end up and install cam plate with cam form down to mate with form on gear. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8295 Fig. 5 Eaton locking differential exploded view 6. Assemble 2 eared discs, 1 splined disc and wave spring onto cam plate as shown in Fig. 5. If components are reused, they must be installed in original position. 7. Alternately assemble 3 splined and 4 eared discs on cam gear hub, as shown in Fig. 5. 8. Mount cam gear assembly in press and position thrust ring over gear hub. 9. Compress disc pack to prevent splined disc from being trapped, then press thrust ring onto gear until seated against shoulder of gear. 10. Inspect assembly to ensure that discs are properly assembled and that first splined disc (large spline) is properly located on cam plate. Side Gear (RH) Clutch Service 1. Remove shim and disc pack from gear keeping components in order. 2. Inspect discs and guide clips and replace as needed. 3. Inspect side gear and shim. If either component is scored or excessively worn, inspect case and replace entire assembly if case is defective. If either side gear or shim must be replaced, shim thickness must be determined. Refer to Shim Selection. See: 9 1/2 Inch Ring Gear/Overhaul/Eaton Locking/Shim Selection Fig. 5 Eaton locking differential exploded view 4. Alternately assemble splined and eared discs on side gear hub as shown in Fig. 5. If components are reused, they must be installed in original position. 5. Install original shim or new shim of equal thickness. Shim Selection CAM GEAR SHIM SELECTION If cam gear is replaced, or if original cam gear shim thickness cannot be determined, shim must be selected to maintain proper backlash with differential pinions using following procedure. 1. Install disc pack guide clips, then mount cam gear assembly in differential case using original shim. 2. Install differential pinions and thrust washers in installed position in case, then insert pinion shaft and retain shaft with lock screw. If pinion shaft cannot be inserted, replace cam gear shim with one of less thickness. 3. Index one tooth of pinion closest to lockscrew so that it points downward, perpendicular to case flange. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8296 4. Wedge large screwdriver or similar tool between pinion shaft and face of cam gear to compress gear assembly into case. 5. Mount suitable dial indicator on case with plunger button bearing against pinion tooth indexed in step 3, Fig. 7. 6. Pull pinion gear against case, rotate pinion back and forth against cam gear and read backlash from indicator. 7. Repeat steps 3 through 6 with remaining differential pinion. 8. Select a cam gear shim which will provide .010-.018 backlash between cam gear and differential pinions. When cam gear and/or shim is replaced, thrust block must be measured and selected to maintain proper clearance during assembly. SIDE GEAR (R.H.) SHIM SELECTION If side gear is replaced, or if original shim thickness cannot be determined, select proper side gear shim thickness by measuring backlash between side gear and differential pinions. Follow procedure outlined for ``Cam Gear Shim Selection,'' using fully assembled side gear properly installed in case. Select a shim that will provide .002-.010 inch backlash between side gear and differential pinions. If side gear and/or shim is replaced, refer to Thrust Block Selection during case assembly in order to install thrust block that will maintain proper assembly clearances. See: 9 1/2 Inch Ring Gear/Overhaul/Eaton Locking/Thrust Block Selection Thrust Block Selection If cam gear, side gear, and/or shims have been replaced, or if it is necessary to replace thrust block and original dimension cannot be determined, use following procedure during differential case assembly to determine proper thrust block side. 1. Install fully assembled cam and side gears in case along with selected shims. 2. Install differential pinion shaft and secure with lock screw. 3. Wedge large screwdrivers or similar tools between pinion shaft and cam and side gears. Fig. 8 Side gear spread measurement. Eaton locking differential 4. Measure distance between cam gear face and side gear face (side gear spread) using suitable gauge, Fig. 8, and record dimension. Ensure that gauge is ``square'' in case and that gauge bears against faces of gears, not gear teeth. 5. Select thrust block of a thickness zero to .006 inch less than dimension measured in step 4. Original thrust block can be reused if it is undamaged and will provide the specified zero to .006 inch clearance. Right side gear can also be reshimmed to obtain specified thrust Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8297 block clearance, as long as specified .002-.010 inch backlash between side gear and differential pinions is maintained. Differential Case Assembly 1. Install 4 guide clips on cam gear clutch ears, using grease for retention. 2. Install cam gear assembly along with selected shim into case noting the following: a. If cam gear was replaced, select shim. Refer to Shim Selection. See: 9 1/2 Inch Ring Gear/Overhaul/Eaton Locking/Shim Selection b. If cam gear thrust ring was replaced, measure length of entire cam gear assembly, including shim. c. If measurement varies more than .003 inch from length measured during disassembly, select and install shim that will return assembly to original length. Incorrect shimming will result in differential malfunction and may cause premature failure. 3. Mount axle shaft in vise with spline protruding enough to engage cam gear, then mount case assembly over shaft engaging shaft in gear. 4. Install 4 small guide clips on ears of side gear clutch pack, using grease to retain clips. 5. Install thrust washers on differential pinions, using grease to adhere washers. 6. Install side gear assembly along with selected shim in case, insert one pinion through small opening in case while simultaneously installing remaining pinion and thrust block through large opening, then rotate case assembly on axle shaft to position pinions in line with shaft opening and thrust block with open side toward small opening in case. Thrust block clearance is critical to proper differential operation. If either side gear, shims or cam gear thrust ring have been replaced, check side gear spread as outlined in Thrust Block Selection, and select thrust block which will provide zero to .006 inch clearance. Refer to Thrust Block Selection. See: 9 1/2 Inch Ring Gear/Overhaul/Eaton Locking/Thrust Block Selection 7. Ensure that pinions and thrust washers are properly positioned, then install pinion shaft and secure with lock screw. Do not torque lock screw until axle shafts have been installed. Fig. 3 Governor & latching bracket installation. Eaton locking differential 8. Insert governor assembly and latching bracket into case, placing straight end of latching bracket spring over and to outside of engagement shaft to preload bracket against governor, Fig. 3. 9. Press governor and latching bracket bushings into case as follows: a. Press governor bushing in to a depth that will provide .004-.020 inch endplay. b. Press bracket bushing in to a depth that will just eliminate endplay. c. Press stop pin in until flush with top of case. 10. Install ring gear and side bearings. Refer to Corporate - Standard. See: 9 1/2 Inch Ring Gear/Overhaul/Corporate - Standard Disassembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8298 Fig. 1 Chevrolet 10-1/2 inch drive axle exploded view 1. Mount axle assembly in suitable holding fixture, remove rear cover and gasket, Fig. 1, and drain lubricant. 2. Remove axle shafts. 3. Measure ring gear and pinion backlash using suitable dial indicator and record reading to aid assembly. 4. Remove adjusting nut lock retainers, then mark installation position of side bearing caps. Keep all components in order during disassembly so that any component to be reused can be installed in original position. 5. Remove side bearing caps, then loosen bearing adjusters using J-24429 or equivalent and lift differential assembly from housing. 6. Remove side bearing outer races and place with respective bearing caps. 7. Measure pinion rotating torque using suitable torque wrench. If no bearing preload is present, or if endplay is evident, pinion bearings may require replacement. 8. Remove pinion bearing retainer bolts, then the pinion assembly, tapping on pilot end of pinion to free assembly from housing. 9. Measure and record thickness of shim installed between pinion bearing retainer and housing and retain shims for assembly. 10. Inspect components. Refer to Cleaning and Inspection, and replace as needed. See: 10 1/2 Inch Ring Gear/Cleaning & Inspection Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8299 Fig. 11 Pinion Depth shim Selection Chart Fig. 12 Side Bearing Preload Adjustment 1. Inspect head of drive pinion for pinion depth code number. Pinion may be stamped with either plus (+) or minus (-) number, indicating necessary modification of shim thickness to ensure proper engagement. 2. Compare depth code number with number on original pinion and use chart, Fig. 11, to select proper shim thickness for preliminary pinion depth adjustment as follows: a. Refer to thickness of shims removed during disassembly and add or subtract the value shown in chart. b. If original pinion, housing and rear bearing is to be reused, install shims of original thickness. 3. Position selected shim on axle housing, ensure that bolt holes are aligned, then install pinion assembly and torque retaining bolts to 65 ft. lbs. in crossing pattern. 4. Place outer races over differential case bearings, mount differential assembly in housing and install bearing caps, and tighten cap bolts snug. 5. Loosen right bearing adjusting nut and tighten left nut using suitable tool, Fig. 12, until ring gear contacts pinion. Do not force gears into contact. Tighten left nut just enough to obtain zero backlash without binding gears. 6. Loosen left adjusting nut approximately two notches, then install adjusting nut lock. 7. Firmly tighten right adjusting nut to force case against left nut, then loosen nut until clearance exists between right nut and bearing race. 8. Tighten right adjusting nut until it just contacts bearing race (zero preload), then tighten nut an additional two slots for used bearings or three slots for new bearings and secure position with locking retainer. At this point differential bearing preload is properly set. If any additional adjustments are required, ensure that preload remains as established. If one adjusting nut is loosened, the other nut must be tightened an equal amount in order to maintain preload. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8300 Fig. 13 Ring Gear & Pinion Backlash Measurement Fig. 14 Ring Gear & Pinion Tooth Contact Inspection 9. Mount suitable dial indicator on housing with plunger contact bearing against ring gear tooth, Fig. 13. 10. Hold pinion and rock ring gear back and forth, reading backlash from dial indicator. 11. Backlash should be .003-.012 inch, with .005-.008 inch the preferred setting. If original ring gear and pinion are used, set backlash to amount measured during disassembly to avoid changing gear contact pattern. 12. If backlash is not within specifications, proceed as follows: a. If backlash is greater than .012 inch, loosen right adjusting nut one notch and tighten left nut one notch. b. If backlash is less than .003 inch, loosen left adjusting nut one notch, then tighten right nut 1 notch. Always rotate adjusting nuts equal amounts in opposite directions to maintain differential bearing preload. c. Recheck backlash after each adjustment and correct as needed. d. When proper backlash has been obtained, install adjusting nut locks to secure adjustment. 13. Torque side bearing cap bolts to 135 ft. lbs., then check gear tooth contact pattern as follows. Gear tooth contact pattern must be checked to verify the correct relationship between ring gear and pinion in order to ensure that pinion depth is set properly. a. Ensure that ring gear is clean and free from oil. b. Apply suitable marking compound to coat drive and coast face of each ring gear tooth. c. Apply braking force to differential case in order to load gears, then turn pinion to rotate ring gear one full revolution in each direction. If Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8301 check is made without loading gears, a satisfactory pattern cannot be obtained. Excessive rotation of ring gear is not recommended. d. Inspect contact pattern on ring gear and correct differential adjustments, if necessary, as shown in Fig. 14. e. Clean marking compound from gears. 14. Install axle shafts, rear cover and gasket. 15. Install axle assembly in vehicle, then fill with specified lubricant. Cleaning & Inspection 1. Clean components in suitable solvent and blow dry with compressed air, noting the following: a. Do not use brush when cleaning bearings. b. Do not ``spin dry'' bearings as they will be damaged. c. Lightly lubricate components after cleaning to retard corrosion. d. Keep all components in order to ensure proper assembly. 2. Inspect gears for cracks, chipped or broken teeth, wear and scoring. Replace gears that are damaged or excessively worn. Ring gear and pinion must be replaced as an assembly. 3. Inspect differential case for cracks, damage, distortion, and worn or scored side gear bores and bearing surfaces. Replace case if damaged or scored. 4. Inspect axle and pinion housings for scored bearing mount surfaces, cracks and distortion, and replace as needed. Ensure that housing is clean and free from foreign material. 5. Inspect bearing rollers and races for pitting, scoring, overheating and damage. 6. Mate each bearing with race and check operation. 7. Replace any bearing assembly that is damaged, excessively worn, or that fails to operate smoothly. 8. Mount differential case along with ring gear and side bearings in housing, adjust side bearings to zero preload and check ring gear runout with dial indicator bearing against machined edge of gear. 9. If ring gear runout exceeds .003 inch and gear cannot be repositioned to reduce runout, replace ring gear and/or case assembly. Corporate - Standard 1. If side bearings are to be replaced, remove bearings using suitable puller, ensuring that puller jaws are seated in case notches and pulling against side bearing inner race. 2. Remove ring gear retaining bolts and lockwashers, then the ring gear, using soft faced hammer to tap gear from case. Do not pry gear from case as machined surfaces will be damaged. 3. Scribe matching mark between differential case halves, then separate cover from case. 4. Remove differential pinion, pinion yoke, side gears and thrust washers from case, noting installation position for assembly. 5. Inspect components. Refer to Cleaning and Inspection, and replace as needed. See: 10 1/2 Inch Ring Gear/Cleaning & Inspection If components are to be reused, they must be installed in original position. Coat all components with specified lubricant prior to installation. 6. Install differential pinions and thrust washers on yoke. 7. Install side gears and thrust washers in case halves, then position yoke and pinion assembly on flanged case half. 8. Hold side gear into case cover and join case halves, ensuring that matching marks are aligned and that gears are properly meshed. 9. Install ring gear, retaining bolts and lock washers, then evenly torque ring gear bolts to 110 ft. lbs. 10. Install case side bearings, using suitable driver to seat bearings. Support case on suitable pilot when installing second side bearing to prevent damaging bearing already installed. Case Disassembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8302 Fig. 2 Eaton locking differential exploded view 1. Remove side bearings and ring gear as outlined for standard differential. 2. Remove 3 case retaining screws from ring gear mounting flange, then set unit on right case half, Fig. 2. 3. Carefully pry case apart at yoke opening, hold side gear assembly in case, then remove left case half. 4. Note installation position, then remove governor and latching bracket. 5. Remove thrust blocks, yoke and differential pinions, noting installation position for assembly. 6. Remove cam gear and disc assembly, shim and guide clips from right case half. 7. Remove side gear, disc pack and shim, and guide clips from left case half. 8. Clean and inspect all components, keeping components in order for proper assembly. Replace any components that are damaged, distorted or excessively worn. Due to critical tolerances required for proper operation, the differential case cannot be serviced separately. If case is defective, the entire differential assembly must be replaced. In addition, internal clearances are such that shims, thrust blocks, side gears or cam gear thrust ring should not be replaced unnecessarily, even if slight wear patterns are evident. If shims, thrust blocks, side gears or thrust ring must be replaced, measurement and replacement procedures must be performed as outlined in order to maintain critical assembly clearances. Cam Gear Clutch Service 1. Measure and record overall length of cam gear assembly from front face of gear to back face of thrust ring, including shim. 2. Compress disc pack and insert jaws of bearing separator J-22912 or equivalent between thrust ring and top clutch disc with chamfer of separator facing thrust ring. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8303 Fig. 6 Cam Gear Thrust Ring Removal. Eaton Locking Differential 3. Support separator in press and press cam gear from thrust ring using suitable spacer, Fig. 3, keeping components in order as cam gear is removed. Fig. 4 Cam gear assembly exploded view. Eaton locking differential 4. Remove discs, spring and cam plate from gear, Fig. 4, clean and inspect components and replace any that are damaged or excessively worn. Do not replace cam gear and/or thrust ring unless necessary. If ring or gear is excessively worn or scored, inspect bore in case. If case bore is scored, differential assembly must be replaced. If cam gear or thrust ring is replaced, shim thickness must be selected to provide original assembly dimension and proper differential pinion backlash. 5. Position cam gear with hub facing up and install cam plate with cam form down to mesh with form on gear. 6. Assemble 2 eared discs and 1 disc with large splines on cam plate, starting with eared disc as shown in Fig. 4, then install wave spring. If components are reused, they must be installed in original position. 7. Assemble 4 eared discs and 3 splined discs on cam gear, starting with eared disc as shown in Fig. 4. 8. Position cam gear assembly in press and install thrust ring on hub of gear, ensuring that ring is square with hub. 9. Compress disc pack to prevent disc from being trapped, then press thrust ring onto cam gear until ring is seated against shoulder of gear. 10. Inspect assembly and ensure that components are properly installed. Side Gear (LH) Clutch Service 1. Remove guide clips and clutch discs from gear keeping components in order. 2. Clean and inspect components, and replace as needed. If side gear shim is defective, it must be replaced with one of equal thickness. If side gear is replaced, and/or if side gear shim thickness cannot be determined, perform Side Gear Shim Selection procedure. Refer to Side Gear Shim Selection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8304 Fig. 2 Eaton locking differential exploded view 3. Install eared and splined clutch discs on side gear, starting with eared disc as shown in Fig. 2. If components are reused, they must be installed in original position. 4. Install selected shim on side gear. Cam Gear Shim Selection If cam gear is replaced, or if original cam gear shim thickness cannot be determined, shim must be selected to maintain proper backlash with differential pinions using following procedure. 1. Install 6 guide clips on cam gear clutch ears, then insert cam gear assembly into right case half. Fig. 5 Cam/side gear installation for assembly clearance measurement. Eaton locking differential 2. Clamp cam gear assembly securely in case pocket using suitable bolt, nut and washers as shown in Fig. 5. 3. Install all 3 differential pinions and thrust washers on yoke and firmly seat pinion and yoke assembly in case, tapping assembly with suitable hammer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8305 4. Slightly loosen bolt clamping cam gear into case and index one pinion gear tooth so that it points downward, perpendicular to parting line of case, then retighten cam gear clamping bolt. 5. Mount suitable dial indicator on case with plunger contact bearing against tooth indexed in step 4. 6. Firmly hold pinion into seat, rock pinion back and forth against cam gear and record backlash reading from dial indicator, Fig. 6. 7. Repeat steps 4 through 6 with each remaining pinion, then select cam gear shim that will provide .010-.018 inch backlash between all pinions and cam gear. When cam gear and/or shim is replaced, thrust blocks must be measured and selected to maintain proper clearance during assembly. Side Gear Shim Selection If side gear is replaced, or if original shim thickness cannot be measured, select proper side gear shim thickness by measuring backlash between side gear and differential pinions. Follow procedure for Cam Gear Shim Selection, using fully assembled side gear installed in left case half. Refer to Cam Gear Shim Selection. See: 10 1/2 Inch Ring Gear/Overhaul/Eaton Locking/Cam Gear Shim Selection Select a shim that will provide .002-.010 inch backlash between side gear and differential pinions. If side gear and/or shim is replaced, refer to ``Thrust Block Selection'' during case assembly in order to install thrust block that will maintain proper assembly clearances. Thrust Block Selection If cam gear, side gear and/or shims are replaced, or if thrust blocks must be replaced and original dimension cannot be determined, use following procedure during case assembly to determine proper thrust block size. 1. Secure fully assembled cam gear and side gear assemblies into respective case halves as outlined in shim selection procedure. Refer to Cam Gear Shim Selection. See: 10 1/2 Inch Ring Gear/Overhaul/Eaton Locking/Cam Gear Shim Selection 2. Using suitable gauge block and depth gauge, measure distance from each gear face to case mounting surface, Fig. 7, and record dimension. 3. Add together cam gear and side gear depth measurements to obtain side gear spread. When adding dimensions measured in step 2, be sure to subtract thickness of gauge block from each measurement. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8306 4. Select 2 thrust blocks with the combined thickness of zero to .006 inch less than side gear spread measurement, measuring thrust blocks as shown, Fig. 8. Original thrust blocks can be used if they are undamaged and will provide the specified zero to .006 inch clearance. In addition, left side gear can be reshimmed to provide proper thrust block clearance as long as specified .002-.006 inch backlash is maintained between side gear and differential pinions. Differential Case Assembly Coat components with specified axle lubricant during assembly. If components are reused, they should be installed in original position. 1. Install 6 guide clips on ears of cam gear disc pack, using grease to retain clips. 2. Install cam gear assembly along with selected shim into right case half. If cam gear thrust ring was replaced, measure length of assembly from front face of cam gear to rear face of thrust ring, including shim. Select a shim that will provide a measurement as close to measurement made during disassembly as possible. 3. Install selected right side thrust block on cam gear face with button side of block facing up. If cam or side gears or thrust block was replaced, select thrust block thickness. Refer to Thrust Block Selection. Improper thrust block clearance will result in differential malfunction. 4. Assemble differential pinions and thrust washers on yoke, index yoke to proper position, then install yoke in right side of case. 5. Ensure that yoke is centered over thrust block button and seat yoke in housing by tapping lightly with hammer. 6. Install left side thrust block, ensuring that thrust block button is seated in yoke. Ensure that thrust block is of proper thickness. Refer to Thrust Block Selection. See: 10 1/2 Inch Ring Gear/Overhaul/Eaton Locking/Thrust Block Selection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8307 Fig. 2 Eaton locking differential exploded view 7. Install governor and latching bracket in respective positions, Fig. 2, and position straight end of latching bracket spring over and to the outside of governor shaft to preload bracket against governor. 8. Install 6 guide clips on ears of side gear disc pack using grease to retain clips. 9. Install selected shim in left case half. 10. Carefully remove disc pack from side gear and lower assembly into right case half, ensuring that guide clips are properly positioned. 11. Insert side gear through disc pack into left case half, rotating gear as needed to align splines. 12. Hold side gear into case, then lower left case assembly onto right case half, ensuring that bores for governor and latching bracket shafts are properly aligned. 13. Invert assembly taking care not to dislodge internal components, then install 3 retaining screws. 14. Mount axle shaft in vise with spline protruding enough to engage side gear. 15. Install case assembly over axle shaft and rotate case to check operation. Assembly should rotate smoothly, without binding or locking-up. 16. Install ring gear and side bearings as outlined for standard differential. Refer to Corporate Standard. See: 10 1/2 Inch Ring Gear/Overhaul/Corporate - Standard Axle Disassembly 1. Drain lubricant from axle housing and remove axle shafts. 2. Disconnect propeller shaft from companion flange, tape bearing caps to universal joint spider and secure shaft aside. 3. Remove bolts securing carrier to axle housing and the lockwashers, support carrier and remove carrier assembly from axle housing. 4. Mount carrier assembly in suitable holding fixture. 5. Loosen ring gear thrust pad locknut and remove thrust pad. 6. Remove side bearing adjuster locks, bearing cap bolts and lock washers. 7. Mark position of bearing caps for assembly, then remove bearing caps by tapping cap bosses with soft faced hammer. Do not pry caps from carrier as they may be damaged. Keep all components in order to aid assembly. 8. Remove differential case assembly from case, along with side bearing outer races, and place races with respective bearing caps. 9. Remove bolts securing pinion bearing housing to carrier, then separate pinion housing from carrier by tapping with soft faced hammer. 10. Inspect components as outlined and replace as needed. Keep all components in order so that any component to be reused can be installed in original position. Differential Service DIFFERENTIAL, DISASSEMBLE Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8308 1. Mark differential case halves for proper assembly. 2. Remove bolts holding case and cover together. Ring gear is mounted on case. 3. Separate cover from case and remove differential side gears and thrust washers, pinion gears and thrust washers, and differential spider. INSPECTION 1. Thoroughly wash all parts in suitable solvent. 2. Inspect ring gear for chipped, scored, or worn teeth. 3. Check radial clearance between differential side gears and differential case and the fit of differential pinions on spider. 4. Inspect spider arms for wear or distortion. 5. Inspect teeth and splines of differential pinions and side gears for chipping or excessive wear. 6. Check thrust washers for wear, replacing if any signs of wear are evident. 7. Check differential side bearings and cups for broken races, discoloration, or roughness. 8. Inspect differential case for cracks or distortion. RING GEAR, REPLACE 1. Remove ring gear from case by tapping rear of gear with soft faced hammer. 2. Inspect ring gear pilot case flange and rear of ring gear for dirt or burrs. 3. Fabricate two guide pins by cutting heads off of suitable cap screws and slotting ends. 4. Install guide pins to new gear diametrically opposite each other. 5. Start guide pins through case flange and tap ring gear onto case. DIFFERENTIAL BEARING, REPLACE 1. Install tool J-8107 or equivalent, ensuring that tool legs are securely fitted in notches in case, and tighten retaining yokes. 2. Tighten puller screw to remove bearing. 3. Position new bearing on hub with thick side of inner race facing case and install bearing using tool J-1488 or equivalent. Side bearing tool is counterbored and has pilot to assure proper installation and seating of bearing. DIFFERENTIAL, ASSEMBLE 1. Lubricate differential side gears, pinions, and thrust washers with suitable lubricant. 2. Place differential pinions and thrust washers on spider. 3. Assemble side gears, pinions, and thrust washers to left half of differential case. 4. Assemble case halves, ensuring that marks made during disassembly are aligned. 5. Install differential to ring bolts and lockwashers and tighten evenly until ring gear is flush with case flange. 6. Remove two guide pins and install remaining bolts, then torque all bolts alternately and evenly to 105 ft. lbs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8309 Differential Carrier: Service and Repair Dana/Spicer Full Floating Axle Disassembly Fig. 1 Exploded View Of Dana Rear Drive Axle w/10 1/2 Inch Ring Gear. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8310 Fig. 2 Exploded View Of Dana Front & Rear Drive Axle w/9 3/4 Inch Ring Gear. 1. Remove axle shafts. Refer to Axle Shaft, Conventional Fixed/Floating / Service and Repair. See: Drive Axles, Bearings and Joints/Axle Shaft Assembly/Service and Repair 2. Remove plug and drain lubricant from carrier. 3. Remove carrier cover attaching screws, then the cover and gasket, Figs. 1 and 2. 4. Mark one side of carrier and matching bearing cap for assembly reference, then remove the bearing caps. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8311 Fig. 3 Differential Carrier Spreading. 5. Spread carrier a maximum of 0.015 inch using differential carrier spreader tool No. J-24385 or equivalent and a suitable dial indicator, Fig. 3. 6. Remove dial indicator, then lift differential case from carrier using a suitable prybar. Measure and record dimensions and note location of side bearing shims for assembly reference, then remove spreader tool. 7. Measure pinion rotating torque with suitable torque wrench. If no preload is present, shake companion flange to check for looseness of pinion assembly. If pinion assembly is loose, the bearing must be replaced. Fig. 4 Companion Flange Removal. 8. Install holder tool No. J-8614-11 or equivalent on flange using two bolts and flat washers. Position tool with four notches toward flange, then remove and discard pinion nut and washer. 9. Remove companion flange using tools shown in Fig. 4. 10. Remove drive pinion from carrier, tapping with a soft-faced hammer, if necessary. 11. Tap on inner race of outer pinion bearing, using a long drift, and remove pinion oil seal, slinger, gasket, outer pinion cone and roller and shim pack. Mark and retain shim pack for assembly. 12. If necessary, drive pinion bearing cups out of carrier, then remove shims and oil slinger from behind inner bearing cup. Mark shims and retain for assembling. 13. Inspect components. Refer to Cleaning & Inspection and replace as necessary. See: Cleaning & Inspection 9 3/4 Inch Ring Gear 1. Place differential assembly with pinion into housing. 2. Install bearing caps in proper position and tighten just enough to retain in place. 3. Install dial indicator on carrier with indicator button contacting back of ring gear. 4. Position two screwdrivers between bearing cup and housing on ring gear side of case and pry ring gear into mesh with pinion gear as far as possible. 5. Set dial indicator to 0 with force still applied to gears. 6. Reposition screwdrivers on opposite side of ring gear, then pry ring gear as far as possible and note indicator reading. Repeat sequence several times until same reading is obtained. This reading indicates amount of shims necessary between differential case and differential bearing on ring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8312 gear side. 7. Remove differential bearing from ring gear side, then install proper amount of shims and reassemble bearing. 8. Remove differential bearing from opposite side of ring gear. Subtract size of shim pack installed on ring gear side of case from reading obtained in step 11 of Overhaul procedure. Refer to Overhaul. See: Overhaul Add an additional 0.015 inch to this figure to compensate for preload and backlash. 9. Assemble proper amount of shims as indicated in step 8, then install side bearing. Fig. 3 Differential Carrier Spreading. 10. Spread differential carrier, Fig. 3, then install differential bearing outer races and position differential case into carrier. 11. Install differential bearing caps and tighten cap screws finger tight. 12. Rotate differential assembly and tap case with a soft-faced hammer to seat case in carrier. 13. Remove spreader tool and torque cap bolts to 85 ft. lbs. 14. Install dial indicator and check ring gear backlash at four equidistant points on the ring gear. Backlash must measure 0.004-0.009 inch and must not vary more than 0.002 inch between checking points. If backlash is not within specifications, adjust differential bearing shim pack as necessary. 15. Ensure ring gear teeth are clean and free from oil, then coat drive and coast face of each tooth with suitable marking compound. 16. Apply braking force to ring gear, then turn pinion to rotate ring gear one complete revolution in each direction. Accurate contact pattern cannot be obtained unless gears are "loaded" when rotated. Fig. 6 Gear Tooth Contact Pattern Check. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8313 17. Examine gear tooth contact pattern, referring to Fig. 6, and correct assembly adjustments as needed. 18. Install housing covers, using a new gasket, and torque attaching bolts to 35 ft. lbs. 19. Install rear universal joint, on rear drive axles, then the axle shafts. 20. Fill axle with specified lubricant. 10 1/2 and 11 Inch Ring Gear 1. Install differential case with side bearings and cups in position, into carrier. 2. Place the smallest of original shims between bearing cup and carrier on ring gear side of case. This shim will act as a gauging shim. 3. Install bearing caps in proper position and tighten just enough to retain in place. 4. Install a dial indicator on ring gear side of carrier with indicator button contacting back of ring gear. 5. Position two screwdrivers between bearing cup and housing on side opposite ring gear. 6. Apply force to screwdrivers to move differential case as far as possible toward the indicator. 7. Set dial indicator to 0 with force still applied to screwdrivers. 8. Reposition screwdrivers on ring gear side of case, then force ring gear into mesh with drive pinion and note dial indicator reading. Repeat sequence several times until same reading is obtained. Add this reading to "gauging" shim thickness to determine shim required on ring gear side of case. 9. Remove "gauging shim and install correct thickness shim between bearing cup and carrier on ring gear side of case. 10. To determine correct dimension for remaining shim, subtract size of shim already installed from reading obtained in step 10 of Overhaul procedure. Refer to Overhaul. See: Overhaul On 10 1/2 inch axles, add an 0.006 inch to this figure to compensate for preload and backlash, on 11 inch, add 0.010 inch. Fig. 3 Differential Carrier Spreading. 11. Spread differential carrier, Fig. 3, then install shim between bearing cup and carrier. 12. Remove spreader tool and dial indicator, then install bearing caps and torque cap bolts to 85 ft. lbs. 13. Install dial indicator and check ring gear backlash at four equidistant points on the ring gear. Backlash must measure 0.004-0.009 inch and must not vary more than 0.002 inch between checking points. If backlash is not within specifications, adjust differential bearing shim pack as necessary. If backlash is less than specifications, decrease shim on ring gear side and increase shim on opposite side an equal amount. If backlash exceeds specifications, increase shim on ring gear side and decrease shim on opposite side an equal amount. 14. Ensure ring gear teeth are clean and free from oil, then coat drive and coast face of each tooth with suitable marking compound. 15. Apply braking force to ring gear, then turn pinion to rotate ring gear one complete revolution in each direction. Accurate contact pattern cannot be obtained unless gears are "loaded when rotated. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8314 Fig. 6 Gear Tooth Contact Pattern Check. 16. Examine gear tooth contact pattern, referring to Fig. 6, and correct assembly adjustments as needed. 17. Install housing cover, using a new gasket, and torque attaching bolts to 35 ft. lbs. 18. Install rear universal joint, then the axle shafts. 19. Fill axle with specified lubricant. Cleaning & Inspection 1. Clean components in suitable solvent and blow dry with compressed air, noting the following: a. Do not use brush when cleaning bearings. b. Do not ``spin dry'' bearings as bearings will be damaged. c. Lightly lubricate components after cleaning to retard corrosion. d. Keep all components in order to ensure proper assembly. 2. Inspect gears for cracks, chipped or broken teeth, wear and scoring. Replace gears that are damaged or excessively worn. 3. Inspect differential case for cracks, damage, distortion, worn side gear bores and scored bearing surfaces, and replace as needed. 4. Inspect housing for scored bearing mount surfaces, cracks and distortion, and replace as needed. Ensure that housing is clean and free from foreign material. 5. Inspect bearing rollers and races for pitting, scoring, overheating and damage. 6. Mate each bearing with race and check operation. 7. Replace any bearing assembly that is damaged, excessively worn, or that fails to operate smoothly. 8. Mount differential case along with side bearings and ring gear in housing, adjust side bearings to zero preload and check ring gear runout with dial indicator bearing against machined edge of gear. 9 3/4 Inch Ring Gear 1. Remove differential bearing cups and tag for assembly reference. 2. Secure differential in a suitable vise and drive out pinion shaft lockpin. 3. Remove differential bearing cone and roller using a suitable puller and plug tool No. J-8107-3 or equivalent. Tag cone and rollers for assembly reference. 4. Remove spacer, pinion shaft, pinions, side gears and thrust washers from differential case. 5. Remove ring gear attaching bolts and the ring gear. 6. Position differential side gears and new thrust washers in differential case. 7. Position differential pinions and new thrust washers in differential case. 8. Install pinion shaft in case, then align hole in shaft with hole in case and drive lockpin into position. Peen hole to prevent pin from falling from case. 9. Install ring gear and torque bolts alternately and evenly to 110 ft. lbs. 10. Position side bearings onto case and seat bearings using a suitable driver. 11. Determine total amount of shims needed to set backlash as follows: a. Place differential case in carrier and install bearing caps in original position. Tighten caps just enough to retain in place. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8315 b. Install dial indicator on carrier with indicator button contacting back surface of ring gear. c. Rotate differential case and note runout. If runout exceeds 0.002 inch, remove differential case and the ring gear from case. d. Reinstall case and check runout at case flange. If runout exceeds 0.002 inch, the bearing or differential case is defective and corrections should be made before proceeding. e. Position two screwdrivers between bearing cup and ring gear on opposite side of ring gear. Apply force to screwdrivers to move differential case as far as possible toward dial indicator. Rock the ring gear to seat bearings and, with force still applied, set dial indicator to "0". f. Reposition screwdrivers between bearing cup and carrier on ring gear side. Apply force to screwdrivers to move differential case as far as possible toward center of carrier and note indicator readings. g. Remove differential case from carrier. 10 1/2 and 11 Inch Ring Gear 1. Remove differential side bearings using a suitable puller or press. 2. Remove ring gear attaching bolts and the ring gear. 3. Scribe an alignment mark on both case halves, then remove bolts holding case halves together. 4. Tap top half of case loose from bottom, then remove top half and all internal components. 5. Position new washers on side gears, using a small amount of lubricant on side gear hubs. 6. Install pinion gears and new washers onto cross shaft. 7. Assemble top half of case to bottom half, using alignment marks made during disassembly. Tighten bolts alternately and evenly. 8. Install ring gear and torque bolts alternately in stages to 110 ft. lbs on 10-1/2 inch axles, 220 ft. lbs. on 11 inch. 9. Position side bearings onto case and seat bearings using a suitable driver. When installing second bearing, support case with suitable pilot to prevent damaging case of opposite bearing. 10. Determine side bearing shim requirements as follows: a. Place bearing cups over side bearings and install differential case into carrier, with pinion removed from carrier. b. Position original shim in ring gear side, then install bearing caps and tighten just enough to retain in place. c. Install a dial indicator on carrier with indicator button contacting back surface of ring gear. d. Position two screwdrivers between bearing shim and carrier on ring gear side of case. Apply force to screwdrivers to move differential case as far as possible away from dial indicator. With force still applied, set dial indicator to 0. e. Reposition screwdrivers on opposite side of differential case and force differential case back toward dial indicator. Repeat sequence several times until same reading is obtained. f. Add thickness of shim to dial indicator reading and record the result. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8316 Differential Carrier: Service and Repair Timken/Rockwell - 12 Inch Ring Gear Disassembly 1. Drain lubricant from axle housing and remove axle shaft retaining nuts and lockwashers. 2. Rap each axle shaft sharply in center of flange, remove tapered dowels, then withdraw axle shafts. Do not pry axle shaft from hub. Rapping flange sharply should release tapered dowels locating flange and allow axle to be removed. 3. Disconnect propeller shaft from companion flange and secure shaft aside. 4. Remove all nuts securing carrier to housing except top two, loosen top two nuts and break carrier free from housing by tapping with soft faced hammer. 5. Support carrier with suitable jack, remove top two retaining nuts and withdraw carrier assembly from housing. Small pry bar may be used to aid carrier removal, but end of bar must be suitably rounded to prevent damage to mounting flange. 6. Mount carrier assembly in suitable holding fixture and check ring gear and pinion backlash to aid assembly. If original ring gear and pinion are to be reused, backlash should be set to clearance measured in step 6 to maintain tooth contact pattern. 7. Loosen jam nut and back-off ring gear thrust adjusting screw. 8. Center punch one carrier leg, bearing cap and side bearing race to identify component location for assembly. Keep all components in order during disassembly. Components that are to be reused must be installed in original position. Fig. 1 Exploded View Of Timken/Rockwell Drive Axle With 12 inch Ring Gear 9. Remove differential bearing adjusting nut locks, bearing caps and adjusting nuts, Fig. 1. 10. Lift differential case assembly from carrier. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8317 11. Hold companion flange with suitable tool, then remove pinion nut and washer. 12. Remove companion flange using suitable puller. Fig. 2 Pinion, Cage & Bearing Assembly Removal 13. Remove pinion cage and bearing assembly, along with shims, using suitable puller bolts to free assembly from housing, Fig. 2, and retain shim pack to aid assembly. 14. Clean and inspect components. Refer to Cleaning and Inspection and replace as needed. See: Cleaning and Inspection Drive Pinion Installation 1. Using micrometer or vernier gauge, measure and record thickness of original shim pack. 2. Check P.C. number on original pinion. If number is positive, subtract it from original shim pack thickness. If number is negative, add it to original shim pack thickness. Record resulting value. 3. Check P.C. number on new pinion. If number is positive, add it to value obtained in step 2. If number is negative, subtract it from value obtained in step 2. 4. Figure obtained in step 3 indicates thickness of new shim pack to be used. 5. Position correct shim pack between pinion cage and carrier. Use a minimum of three shims per pack. If pack is made up from various thicknesses of shims, place thinnest shims on either side of pack. 6. Install pinion and cage assembly with shims into carrier and tap into position with soft mallet. 7. Install pinion cage cap screws, torquing to 35 ft. lbs. Differential Case Installation 1. Temporarily install bearing cups, threaded adjusting rings if used, and bearing caps, torquing cap screws to 115-140 ft. lbs. 2. If bearing cups are not of a hand push fit in bores, bores must be reworked with a scraper or emery cloth until a hand push fit is obtained. Use a blued bearing cup as a gauge and check the fits as work progresses. When cups fit properly, remove bearing caps. 3. After checking related parts, coat differential bearing cones and caps with rear axle lubricant. 4. Place cups over assembled bearing cones and position differential assembly in carrier. 5. Insert bearing adjusting nuts and turn hand-tight against bearing cups. 6. Install bearing caps in correct location as marked and tap lightly in position. If bearing caps cannot be properly seated bearing adjusters may be cross-threaded. Remove bearing caps and reposition adjusting nuts as needed. Do not force bearing caps into position as carrier, caps and adjusting nuts will be damaged. 7. Install bearing cap bolts or nuts and washers, if used, then torque fasteners to 115-140 ft. lbs. Side Bearing Preload & Backlash Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8318 Fig. 8 Side Bearing Preload Adjustment Fig. 9 Ring Gear & Pinion Backlash Adjustment 1. Using dial indicator at back face of ring gear, Fig. 8, loosen bearing adjusting nut on side opposite gear only enough to notice endplay on dial indicator. 2. Tighten same adjusting nut only enough to obtain zero endplay. 3. Check gear for runout. If runout exceeds .008 inch, remove differential and check for cause. 4. Tighten adjusting nuts one notch each from zero endplay to preload differential bearings. 5. Mount dial indicator with plunger contact bearing against ring gear tooth, Fig. 9. 6. Hold pinion and rock ring gear, reading backlash from dial indicator. 7. If backlash is not within specifications, adjust as follows. If ring gear and pinion are reused, lash should be adjusted to value measured prior to disassembly. a. If backlash is greater than specified, loosen nut in ring gear tooth side and tighten opposite nut an equal amount. b. If backlash is less than specified, loosen nut on back side of ring gear and tighten nut on gear face side an equal amount. Adjusting nuts must be rotated equally, in opposite directions, in order to maintain proper side bearing preload. 8. Install adjuster locks to secure adjustment. Gear Tooth Contact Inspection Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8319 Fig. 10 Gear Tooth Contact Inspection 1. Ensure that ring gear is clean and free from oil, then coat coast and drive face of each ring gear tooth with suitable marking compound. 2. Brake ring gear to load gears, then turn pinion in order to rotate ring gear one full revolution in each direction. Satisfactory contact pattern cannot be obtained unless gears are loaded. Excessive rotation of gears is not recommended. 3. Inspect tooth contact pattern referring to Fig. 10, and correct assembly adjustments, as needed to obtain correct pattern. 4. Clean marking compound from gears. Thrust Screw 1. Remove carrier from stand and position with back face of hypoid or spiral bevel gear upward. 2. Remove thrust screw and locknut. 3. Install thrust screw and locknut and tighten thrust screw enough to locate thrust block firmly against back face of hypoid gear. 4. Loosen thrust screw 1/4 turn and lock securely with nut. 5. Check to ensure minimum clearance of .10 inch during full rotation of bevel gear. Carrier Installation 1. Ensure that housing is clean and free from dirt and foreign material. 2. Inspect housing for damage and distortion, and repair or replace as needed. Remove burrs from machined surfaces using suitable stone or file. 3. Install new gasket over housing studs. If RTV sealer is used, ensure that both mating surfaces are clean and free from oil, then apply a continuous bead of sealer, 1/8 inch wide, completely around one mating surface, circling all bolt holes or studs. 4. Raise carrier assembly with suitable jack, roll assembly onto studs, then install four evenly spaced flat washers and nuts to hold assembly. 5. Install nuts and lock washers on any studs shrouded by housing webs, then evenly tighten 4 evenly spaced nuts to draw carrier into housing. Do not drive carrier into housing by tapping flange as flange will be distorted. 6. Install lock washers under all retaining nuts, then evenly tighten all nuts. 7. Install axle shafts and connect driveshaft to companion flange. 8. Fill housing with specified lubricant. Cleaning and Inspection Steam cleaning assembled drive units after they have been removed from housing is not recommended. It is necessary to completely disassemble drive unit for proper cleaning. Clean all components in suitable solvent and dry immediately afterward. Use soft, clean, lintless paper towels or wiping rags free of abrasive material. Bearings should never be dried by spinning with compressed air. Inspect all bearings, cups, and cones, including those not removed from parts of drive unit, and replace if rollers or cups are worn, pitted, or damaged Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8320 in any way. Remove parts needing replacement with suitable puller or in a press with sleeves. Avoid the use of drifts and hammers as they may easily mutilate or distort component parts. Ring gear and pinion are a matched set and must be replaced as an assembly. Both ring gear and pinion in a replacement set have a matching mark such as ``M29'' or a similar letter/number combination. On the ring gear, matching numbers can be found on the front face of the gear or on the machined outer diameter. On the pinion, matching marks are usually found on the pinion face. However, on pinions with parallel sided splines, the number may be marked on the top flat or one of the splines. Do not install a ring gear and pinion assembly if the matching marks are not the same. Fig. 6 Pinion Code & Matching Mark Identification Fig. 7 Pinion Shim Pack Thickness Chart In addition, each pinion has a Pinion Code (P.C.) Variation Number which indicates variations in thousandths of an inch from the nominal pinion depth setting. This number must be used to modify the Nominal Pinion Gauging Number when calculating shim pack thickness to set pinion depth. This variation number is stamped as either a plus (+) or minus (-) value, and is located adjacent to the matching number, Fig. 6. When a new pinion is installed, shim pack thickness can be determined using the pinion code numbers and chart, Fig. 7. Overhaul DISASSEMBLE 1. If original matching marks are not clear, scribe matching marks between differential case halves to aid assembling. 2. Remove differential case bolts, noting position for assembling, then separate case halves. 3. Remove differential pinion spider, along with pinions and thrust washers, keeping components in order. 4. Remove side gear and thrust washer from each case half. 5. Remove case side bearings, as needed, using suitable puller. 6. If ring gear is to be replaced, proceed as follows: a. Carefully center punch center of each rivet head. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8321 Fig. 3 Ring Rear Removal. b. Using drill 1/32 inch smaller than body of rivet, drill completely through each rivet securing ring gear, Fig. 3. c. Press out rivets and remove ring gear. 7. Inspect components as outlined and replace as needed. ASSEMBLE 1. Install ring gear as follows: a. Immerse ring gear in water heated to 160-180°F. for approximately 10 minutes. b. Align gear over case pilot and install ring gear on differential case. Gear should not be driven or pressed onto case as metal particles may become lodged between gear and case causing excessive runout. c. Install new ring gear retaining bolts from service package and torque bolts to 85-115 ft. lbs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8322 Fig. 1 Exploded View Of Timken/Rockwell Drive Axle With 12 inch Ring Gear 2. Install side gear and thrust washer in ring gear half of case, Fig. 1. Coat all components with specified axle lubricant during assembling. Components that are reused must be installed in original position. 3. Mount differential pinions and thrust washers on spider and install assembly in ring half of case, ensuring that spider is fully seated. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Carrier > Component Information > Service and Repair > Borg Warner > Page 8323 Fig. 4 Differential Case Assembly. 4. Position side gear and thrust washer on pinion assembly, align matching marks, then install remaining case half, Fig. 4. 5. Install 4 case retaining bolts, evenly spaced, and draw case halves together by tightening bolts evenly and alternately. 6. Install remaining case bolts and torque all bolts to 45 ft. lbs. 7. Press side bearings onto case using suitable spacer and pilot. 8. Check rolling resistance of side gear and pinion assemblies as follows: Fig. 5 Differential Rolling Resistance Check. a. Fabricate checking tool by cutting splines from axle shaft and welding nut onto non-splined end, Fig. 5. b. Mount case assembly inside taking care not to damage components. c. Insert stub axle into side gear and rotate assembly with suitable torque wrench. d. If rolling resistance exceeds 50 ft. lbs. when rotating one side gear, recheck differential assembly and correct as needed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Case > Component Information > Technical Service Bulletins > Customer Interest for Differential Case: > 564203A > Nov > 96 > Rear Axle Vent Leak Differential Case: Customer Interest Rear Axle - Vent Leak File In Section: 4 - Drive Axle Bulletin No.: 56-42-03A Date: November, 1996 Subject: Rear Axle Vent Leak (Relocate Rear Axle Vent Tube) Models: 1993-96 Chevrolet and GMC C/K 2, 3 Models with 10.5" Rear Axles This bulletin is being revised to add the 1996 model year. Please discard Corporate Bulletin Number 56-42-03 (Section 4 - Drive Axle) Condition Some owners may comment about an oil soaked load floor or oil leaking from the rear axle vent. Correction Following the instructions given below, relocate the rear axle vent tube to the axle tube. Service Procedure 1. Raise the vehicle and support with suitable safety stands. 2. Disconnect the vent hose from the vent tube and remove the vent tube. 3. Plug the existing vent hole with weld bond epoxy such as J.B. Weld or equivalent following the manufacturer's instructions. 4. Remove the driver's side axle shaft following the procedure in Section 4B1 of the appropriate year Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Case > Component Information > Technical Service Bulletins > Customer Interest for Differential Case: > 564203A > Nov > 96 > Rear Axle Vent Leak > Page 8332 5. Locate the shock mount bracket on the driver's side axle tube (Figure 1). At the top of the axle tube, parallel to the center of the shock bracket, drill a 3/8" hole in the axle tube. Notice: Precaution should be taken to ensure that no metal fragments enter the axle tube. Use a magnet when drilling to lift and catch the metal filings. Apply wheel bearing grease to the drill bit before breaking through the axle tube. 6. Using a 12 mm socket, drive a new vent tube (P/N 14072930) into the axle tube at the location drilled in step 5. Seal the base of the vent tube with RTV sealant (P/N 12345739). 7. Use an extendable magnet tool to capture any metal fragments that may have fallen into the axle tube and then re-install the driver's side axle shaft following the procedure in Section 4B1 of the appropriate year Service Manual. 8. Cut approximately 8.5" (216 mm) off the existing vent hose and discard after verifying that enough vent hose will remain to allow for axle movement. Clamp the remaining hose onto the new axle vent tube installed in step 7. 9. Check the rear axle fluid level. Add fluid if necessary (P/N 1052271 80W-90 GL-5). 10. Lower the vehicle and test drive. Parts Information P/N Description Qty 14072930 Vent Tube 1 12345739 RTV Sealant As Required 1052271 Rear Axle As Required Lubricating Oil Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Case > Component Information > Technical Service Bulletins > Customer Interest for Differential Case: > 564203A > Nov > 96 > Rear Axle Vent Leak > Page 8333 Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time F3270 Rear Vent Replace Use Published Labor Operation Time F1531 Left Axle Shaft R&R; Use Published Labor Operation Time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Case > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Differential Case: > 564203A > Nov > 96 > Rear Axle - Vent Leak Differential Case: All Technical Service Bulletins Rear Axle - Vent Leak File In Section: 4 - Drive Axle Bulletin No.: 56-42-03A Date: November, 1996 Subject: Rear Axle Vent Leak (Relocate Rear Axle Vent Tube) Models: 1993-96 Chevrolet and GMC C/K 2, 3 Models with 10.5" Rear Axles This bulletin is being revised to add the 1996 model year. Please discard Corporate Bulletin Number 56-42-03 (Section 4 - Drive Axle) Condition Some owners may comment about an oil soaked load floor or oil leaking from the rear axle vent. Correction Following the instructions given below, relocate the rear axle vent tube to the axle tube. Service Procedure 1. Raise the vehicle and support with suitable safety stands. 2. Disconnect the vent hose from the vent tube and remove the vent tube. 3. Plug the existing vent hole with weld bond epoxy such as J.B. Weld or equivalent following the manufacturer's instructions. 4. Remove the driver's side axle shaft following the procedure in Section 4B1 of the appropriate year Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Case > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Differential Case: > 564203A > Nov > 96 > Rear Axle - Vent Leak > Page 8339 5. Locate the shock mount bracket on the driver's side axle tube (Figure 1). At the top of the axle tube, parallel to the center of the shock bracket, drill a 3/8" hole in the axle tube. Notice: Precaution should be taken to ensure that no metal fragments enter the axle tube. Use a magnet when drilling to lift and catch the metal filings. Apply wheel bearing grease to the drill bit before breaking through the axle tube. 6. Using a 12 mm socket, drive a new vent tube (P/N 14072930) into the axle tube at the location drilled in step 5. Seal the base of the vent tube with RTV sealant (P/N 12345739). 7. Use an extendable magnet tool to capture any metal fragments that may have fallen into the axle tube and then re-install the driver's side axle shaft following the procedure in Section 4B1 of the appropriate year Service Manual. 8. Cut approximately 8.5" (216 mm) off the existing vent hose and discard after verifying that enough vent hose will remain to allow for axle movement. Clamp the remaining hose onto the new axle vent tube installed in step 7. 9. Check the rear axle fluid level. Add fluid if necessary (P/N 1052271 80W-90 GL-5). 10. Lower the vehicle and test drive. Parts Information P/N Description Qty 14072930 Vent Tube 1 12345739 RTV Sealant As Required 1052271 Rear Axle As Required Lubricating Oil Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Case > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Differential Case: > 564203A > Nov > 96 > Rear Axle - Vent Leak > Page 8340 Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time F3270 Rear Vent Replace Use Published Labor Operation Time F1531 Left Axle Shaft R&R; Use Published Labor Operation Time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Differential Axle Housing > Component Information > Service and Repair Differential Axle Housing: Service and Repair Fig. 1 Exploded View Of Axle Shaft & Housing Components In this rear axle, Fig. 1, the rear axle housing and differential carrier are cast into an integral assembly. The drive pinion assembly is mounted in two opposed tapered roller bearings. The pinion bearings are preloaded by a spacer behind the front bearing. The pinion is positioned by a washer between the head of the pinion and the rear bearing. The differential is supported in the carrier by two tapered roller side bearings. These bearings are preloaded by spacers located between the bearings and carrier housing. The differential assembly is positioned for proper ring gear and pinion backlash by varying these spacers. The differential case houses two side gears in mesh with two pinions mounted on a pinion shaft which is held in place by a lockpin. The side gears and pinions are backed by thrust washers. 1. Raise and support vehicle. Using a suitable jack, support rear axle assembly. 2. Drain fluid from axle assembly. 3. Mark driveshaft to flange, then disconnect driveshaft and tie driveshaft to side rail or crossmember. 4. Tape bearing cups to prevent loss of the rollers. 5. Remove wheel and brake drum or hub and drum assembly. 6. Disconnect parking brake cable from lever and brake flange plate. 7. Disconnect and cap hydraulic brake lines from connectors. 8. Remove shock absorbers from axle brackets. 9. Disconnect vent line from vent fitting. 10. Remove height sensing and brake proportional valve brackets. 11. Remove nuts and washers from U-bolts. 12. Carefully remove U-bolts, spring plates and spacers from axle assembly. 13. Lower axle assembly from vehicle. 14. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Fluid - Differential > Component Information > Technical Service Bulletins > Drivetrain - Rear Axle Lubricant Compatibility & Usage Fluid - Differential: Technical Service Bulletins Drivetrain - Rear Axle Lubricant Compatibility & Usage File in Section: 04 - Driveline Axle Bulletin No.: 99-04-20-001 Date: June, 1999 INFORMATION Subject: Rear Axle Lubricant Compatibility and Usage Models: 1999 Cadillac Escalade 1988-99 Chevrolet and GMC C/K, G Van and P1-3 Series Models Built after the VIN Breakpoints (C/K) listed. This bulletin is being revised to add the 1999 Model Year, VIN Breakpoint information, and additional text Please discard Corporate Bulletin Number 86-42-04 (Section 4 - Driveline/Axle). This bulletin is being issued to inform dealers about the compatibility and usage of the new Fuel Efficient SAE 75W-90 Synthetic Axle Lubricant, GM P/N 12378261 (In Canada use P/N 10953455), with current axles, and with the non-synthetic axle lubricant, GM P/N 1052271 (In Canada use P/N 10950849), for the rear axles on the above light-duty trucks. Testing has shown that the new synthetic lubricant will chemically attack the Room Temperature Vulcanizing (RTV) sealant. Use only the non-synthetic lubricant, P/N 1052271, in axles using RTV sealant (See 9.5 and 10.5 information below). American Axle and Manufacturing (A.A.M.) has approved the use of the new Fuel Efficient SAE 75W-90 synthetic axle lubricant for rear axles with the following restrictions: ^ All 8.6 inch axles are compatible as originally built. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Fluid - Differential > Component Information > Technical Service Bulletins > Drivetrain - Rear Axle Lubricant Compatibility & Usage > Page 8348 ^ 9.5 inch axles on vehicles built prior to mid-February 1998 are NOT compatible because RTV sealant is used on the cover pans. On vehicles built after mid-February 1998 and equipped with 9.5 inch rear axles, synthetic lubricant, P/N 12378261, can be used because the RTV was replaced with a gasket. Other mid-February changes to the 9.5 inch rear axles include a new cover pan and cover pan fasteners common to other axles. Important: The new cover pan is not retrofittable to the housing of 9.5 inch axles on vehicles built prior to mid-February 1998. A new retrofit kit is available that will enable the use of synthetic lubricant for vehicles built after mid-February, 1998. ^ All 10.5 inch axles prior to March 3, 1999 are compatible if the axle shaft hub seal (RTV) is replaced with P/N 327739 gasket when changing to synthetic lubricant. As a product improvement, this new lubricant has been released into 1999 current production C/K vehicles built after the above VIN breakpoints (Except HD3SOO models which use 75W-140 synthetic lubricant, P/N 12346140). It is recommended that synthetic lubricant be used when changing rear axle lubricant for the following reasons: ^ Potential fuel economy ^ Lower operating temperature under severe usage conditions Important: ^ You do not need to wash/rinse any non-synthetic lubricant from the axle cavity when changing over to a synthetic lubricant. However, you should remove debris from the magnet and the bottom of the axle cavity whenever the axle fluid is changed. ^ On light-duty trucks equipped with locking differentials, do NOT use a limited-slip additive. Parts Information Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Fluid - Differential > Component Information > Technical Service Bulletins > Drivetrain - Rear Axle Lubricant Compatibility & Usage > Page 8349 Fluid - Differential: Technical Service Bulletins Drivetrain - Recommended Axle Lubricant File In Section: 0 - General Information Bulletin No.: 76-02-02A Date: October, 1998 INFORMATION Subject: Recommended Axle Lubricant Models: 1999 and Prior Rear Wheel Drive Passenger Cars, Light and Medium Duty Trucks, and Four Wheel Drive Vehicles This bulletin is being revised to add the 1998 and 1999 Model Years and add Vehicle Line and Recommended Axle Lubricant Information. Please discard Corporate Bulletin Number 76-02-02 (Section 0 - General Information). The following tables provide the latest information on recommended axle lubricant. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Fluid - Differential > Component Information > Technical Service Bulletins > Drivetrain - Rear Axle Lubricant Compatibility & Usage > Page 8350 Parts Information Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Fluid - Differential > Component Information > Specifications > Capacity Specifications Fluid - Differential: Capacity Specifications Chevrolet 8 1/2 inch ............................................................................................................................. ..................................................................... 4.2 pts. Chevrolet 9 1/2 inch ............................................................................................................................. ..................................................................... 5.5 pts. Dana 9 3/4 & 10 1/2 inch ..................................................................................................................... ..................................................................... 5.5 pts. Chevrolet 10 1/2 inch ........................................................................................................................... ..................................................................... 7.2 pts. Dana 11 inch ....................................................................................................................................... ........................................................................ 8.2 pts. Rockwell 12 inch .................................................................................................................................. .................................................................... 14.0 pts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Fluid - Differential > Component Information > Specifications > Capacity Specifications > Page 8353 Fluid - Differential: Fluid Type Specifications Rear Axle - Locking Differential (G80) This Article has been updated by TSB # 76-02-02A. SAE 80W-90 GL5 Gear Lubricant, GM P/N 1052271. Do not use limited slip additive. Rear Axle - Non-Locking Differential Standard Differential (Non-Locking) SAE 80W-90 GL-5 Gear Lubricant GM P/N 1052271 HD-3500 Dana 11.0 inch Axle SAE 75W-140 Synthetic Gear lubricant GM P/N 12378261 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Bearing, Differential > Component Information > Adjustments > Dana/Spicer Full Floating Axle Pinion Bearing: Adjustments Dana/Spicer Full Floating Axle Fig. 5 Pinion setting chart If original ring gear and pinion assembly are to be reused, measure original shim pack and build a new shim pack to the same dimension. If baffle is in the axle assembly, it is considered part of the shim pack. Ring gears and pinions are supplied in matched sets only. If a new gear is being used, verify numbers on pinion and ring gear before proceeding with assembly. On the button end of the pinion there is a ``+'', `` - '', or ``0'' number which indicates the best running position for each particular gear set. This position is controlled by shims installed behind the inner bearing cup. If baffles or oil slingers are used, they are considered part of the adjusting shim pack. If a new gear set is being installed, note the plus or minus mark on both old and new pinions and adjust thickness of shim pack to compensate for the difference between these two numbers. Refer to chart, Fig. 5, when determining shim size. 1. Install inner shim pack and, on 9-3/4 inch ring gear axle, the oil slinger in inner or rear cup bore, then drive cup into position using suitable tool. 2. Add or remove an equal amount to the outer shim pack as was added to the inner shim pack. 3. Drive outer cup into carrier bore, then press rear pinion bearing onto pinion shaft. 4. Install drive pinion and bearing into differential carrier. 5. Install shims and outer or front pinion bearing. 6. Install companion flange, then the washer and nut on pinion shaft. Torque nut to 250 ft. lbs. with a suitable holding bar in place. 7. Remove holding bar, then measure rotating torque of pinion shaft. Rotating torque should measure 10-20 inch lbs. with original bearings installed, or 20-40 inch lbs. with new bearings installed, discounting torque required to start turning shaft. 8. If rotating torque is not within specifications, adjust shim pack as necessary. Increase outer shim pack to reduce torque, or decrease shim pack to increase torque. 9. Remove nut, washer and companion flange from pinion shaft. 10. Install oil slinger, gasket (if equipped) and oil seal onto pinion shaft. 11. Install companion flange, washer and nut and torque nut to 250 ft. lbs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Bearing, Differential > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8358 Pinion Bearing: Adjustments Timken/Rockwell - 12 Inch Ring Gear Fig. 1 Exploded View Of Timken/Rockwell Drive Axle With 12 inch Ring Gear DISASSEMBLY 1. Tap or press pinion from cage, taking care not to damage shaft threads, then remove outer pinion bearing, Fig. 1. 2. Remove spacer from pinion, then the inner bearing, using suitable separator and press or puller. 3. If straddle bearing must be replaced, remove snap ring and washer, then the bearing, using suitable puller. 4. If bearings are to be replaced, press outer races from bearing cage, taking care not to distort cage. 5. Inspect components as outlined, and replace as needed, keeping components in order for assembly. ASSEMBLY & PRELOAD 1. When installing new cups, press them firmly against pinion bearing cage shoulders. 2. Lubricate bearings and cups with suitable lubricant. 3. Press rear thrust and radial bearings firmly against pinion shoulders, using suitable sleeve that will bear only on bearing inner race. 4. Install radial bearing lock ring, then squeeze ring into pinion shaft groove. 5. Insert pinion and bearing assembly in pinion cage and position spacer or spacer combination over pinion shaft. 6. Press front bearing firmly against spacer. 7. Rotate cage several revolutions to assure normal bearing contact. 8. Press flange or yoke against forward bearing and install washer and pinion shaft nut. 9. Place pinion and cage assembly over carrier studs, hold flange with suitable tool and torque pinion shaft nut to 240 ft. lbs. 10. Check pinion bearing preload torque. If rotating torque is not within 5 to 15 pound inches, disassemble, adjust spacer, reassemble, and recheck preload torque. Use thinner spacer to increase or thicker spacer to decrease preload. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Bearing, Differential > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8359 11. Hold flange with suitable tool and remove pinion shaft nut and flange. 12. Lubricate pinion shaft oil seal and cover outer edge of seal body with non-hardening sealing compound, then press seal against cover shoulder with suitable tool. 13. Install new gasket and bearing cover. 14. Press flange against forward bearing and install washer and pinion shaft nut, torquing nut to 240 ft. lbs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Bearing, Differential > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8360 Pinion Bearing: Adjustments Corporate and Eaton 7 1/2 - 8 5/8 Inch Ring Gear PINION DEPTH ADJUSTMENT If original ring gear and pinion assembly and rear pinion bearing are to be reused, original depth adjusting shim can be used. However, if ring gear and pinion or rear pinion bearing are replaced, pinion depth must be adjusted using following procedures. 1. Install pinion bearing races to be used in housing using suitable driver. 2. Lubricate pinion bearings and install bearings in races. 3. Mount depth gauging jig in housing, noting the following: Fig. 16 Pinion depth gauge tool installation. Models w/7-1/2 inch ring gear a. On models with 7 1/2 & 7 5/8 inch ring gear, use gauge assembly tool No. J-23597-01 or equivalent, Fig. 16. Follow all tool manufacturer's recommendations when installing gauge assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Bearing, Differential > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8361 Fig. 17 Pinion depth gauge tool installation. Models w/8-1/2 & 8-7/8 inch ring gear b. On models with 8 1/2 and 8 5/8 inch ring gear, use gauge assembly tool No. J-21777-01 or equivalent, Fig. 17. Follow all tool manufacturer's recommendations when installing gauge assembly. c. Assemble gauge plate onto preload stud. d. Hold pinion bearings in position, insert stud through rear bearing and pilot and front bearing and pilot, then install retaining nut and tighten nut until snug. e. Rotate tool to ensure bearings are properly seated. f. Hold preload stud and torque nut until 20 inch lbs. is required to rotate stud. Tighten nut in small increments, checking rotating torque after each adjustment, to prevent damaging bearings. g. Mount side bearing discs on arbor, using step for disc that corresponds to base of housing. h. Mount arbor and plunger assembly in housing, ensuring that side bearing discs are properly seated, install bearing caps and tighten cap bolts to prevent bearing discs from moving. 4. Mount suitable dial indicator on arbor stud with indicator contact button bearing against top of arbor plunger. 5. Preload indicator 1/2 revolution and secure to arbor mounting stud in this position. 6. Place arbor plunger on gauge plate, rotating plate as needed so that plunger rests directly on button corresponding to ring gear size. 7. Slowly rock plunger rod back and forth across button while observing dial indicator. 8. At point on button where indicator registers greatest deflection, zero dial indicator. Perform steps 7 and 8 several times to ensure correct setting. 9. Once verified zero reading is obtained, swing plunger aside until it is clear of gauge plate button and record dial indicator reading. Indicator will now read required pinion depth shim thickness for a "nominal" pinion. 10. Inspect rear face of drive pinion to be installed for a pinion code number. This number indicates in thousandths of an inch necessary modification of pinion shim thickness obtained in step 9. 11. Select pinion depth adjusting shim as follows: a. If pinion is stamped with a plus (+) number, add that number of thousandths to dimension obtained in step 9. b. If pinion is stamped with a minus (-) number, subtract that many thousandths from dimension obtained in step 9. c. If pinion is not stamped with plus or minus number, dimension obtained in step 9 is correct shim thickness. 12. Remove gauging tools and pinion bearings from housing, noting installation position of bearings. PINION INSTALLATION 1. Install selected shim onto pinion shaft, lubricate rear pinion bearing with specified axle lubricant, then press rear bearing onto pinion using suitable spacers. 2. Install new collapsible spacer onto pinion shaft, then insert pinion assembly into housing. 3. Lubricate front pinion bearing, install bearing into housing and tap bearing over pinion shaft with suitable drift while assistant holds pinion in place. Old pinion nut and suitable large washer can be used to seat front bearing on pinion, but care must be taken not to collapse spacer if this method is used. 4. Install new pinion seal in housing, coat seal lips with grease, then mount driveshaft yoke on pinion shaft, lightly tapping yoke until several pinion shaft threads protrude from yoke. 5. Coat rear of pinion washer with suitable sealer, then install washer and new pinion nut. 6. Hold driveshaft yoke with suitable tool, then alternately tighten pinion nut and rotate pinion until endplay is reduced to zero. 7. When endplay is reduced to zero, check pinion bearing preload using suitable torque wrench. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Bearing, Differential > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8362 8. Continue tightening pinion nut in small increments until specified pinion bearing preload is obtained, rotating pinion and checking preload after each adjustment. Exceeding preload specification will compress collapsible spacer too far, requiring replacement of spacer. If preload specification is exceeded, spacer must be replaced and adjustment procedure must be repeated. Do not loosen pinion nut to reduce preload. 9 1/2 Inch Ring Gear Fig. 9 Pinion depth gauge installation PINION DEPTH, ADJUST If original ring gear and pinion assembly and rear pinion bearing are to be reused, original depth adjusting shim can be used. However, if ring gear and pinion or rear pinion bearing requires replacement, pinion depth must be adjusted using following procedures. 1. Install pinion bearing races to be used in housing using suitable driver. 2. Lubricate pinion bearings and install bearings in races. 3. Mount depth gauging jig in housing noting the following. Use gauge assembly J-21777-01, Fig. 9, or suitable equivalent. Follow all tool manufacturer's recommendations when installing gauge assembly. a. Assemble gauge plate on preload stud. b. Hold pinion bearings in position, insert stud through rear bearing and pilot, then front bearing and pilot, install retaining nut and tighten nut hand tight. c. Rotate tool to ensure that bearings are properly seated. d. Hold preload stud and tighten nut until 20 inch lbs. torque is required to rotate stud. Tighten nut in small increments, checking rotating torque after each adjustment using suitable torque wrench. e. Mount side bearing discs on arbor, using step that corresponds to base of housing. f. Mount arbor and plunger assembly in housing ensuring that side bearing discs are properly seated, install bearing caps and tighten cap bolts to prevent bearing discs from moving. 4. Mount suitable dial indicator on arbor stud with indicator contact button bearing against top of arbor plunger. 5. Preload indicator 1/2 revolution, then secure to arbor stud in this position. 6. Place arbor plunger on gauge plate, rotate plate as needed so that plunger rests directly on button corresponding to ring gear size. 7. Slowly rock plunger rod back and forth across button while observing dial indicator. 8. At point on button where indicator registers greatest deflection, zero dial indicator. Perform steps 7 and 8 several times to ensure correct setting. 9. Once verified zero setting is obtained, swing plunger aside until it is clear of gauge plate button and record dial indicator reading. Indicator will now read required pinion depth shim thickness for ``nominal'' pinion. 10. Inspect rear face of drive pinion to be installed for a pinion code number. This number indicates in thousandths of an inch necessary modification of pinion shim thickness obtained in step 9. 11. Select pinion depth adjusting shim as follows: a. If pinion is stamped with a plus (+) number, add that number of thousandths to dimension obtained in step 9. b. If pinion is stamped with a minus ( - ) number, subtract that many thousandths from dimension obtained in step 9. c. If pinion is not stamped with plus or minus number, dimension obtained in step 9 is correct shim thickness. 12. Remove gauging tool and pinion bearings from housing. DRIVE PINION, INSTALL 1. Install pinion bearing races in housing, if not previously installed, using suitable drivers to ensure that races are squarely seated. 2. Install selected shim on pinion shaft, lubricate rear pinion bearing with specified axle lubricant, then press rear bearing onto pinion using suitable spacers. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Bearing, Differential > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8363 3. Install new collapsible spacer on pinion and insert pinion assembly into housing. 4. Lubricate front pinion bearing, install bearing in housing and tap bearing onto pinion shaft while assistant holds pinion in place. Old pinion nut and large washer can be used to draw front bearing onto pinion, but care must be taken not to collapse spacer if this method is used. 5. Install new pinion seal in housing, coat seal lips with grease, then mount driveshaft flange on pinion shaft, lightly tapping flange until several pinion shaft threads protrude. 6. Coat rear of pinion washer with suitable sealer, then install washer and new pinion nut and adjust preload to specifications. PINION BEARING PRELOAD ADJUSTMENT 1. Ensure pinion and bearings are properly installed, as outlined. 2. Hold driveshaft companion flange with suitable tool, then alternately tighten pinion nut and rotate pinion until endplay is reduced to zero. 3. Using and inch lb. torque wrench, check pinion preload by rotating pinion with wrench. Preload should be at 20-25 inch lbs. or less on new bearings or 10-15 inch lbs. on used bearings. 4. Continue tightening pinion nut in small increments until specified bearing preload is obtained, rotating pinion and checking preload after each adjustment. Exceeding preload specification will compress collapsible spacer too far, requiring replacement of spacer. If preload specification is exceeded, spacer must be replaced and adjustment procedure must be repeated. Do not loosen pinion nut to reduce preload. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Bearing, Differential > Component Information > Service and Repair > Dana/Spicer Full Floating Axle Pinion Bearing: Service and Repair Dana/Spicer Full Floating Axle 9 3/4 Inch Ring Gear Fig. 5 Pinion Setting Chart If original ring gear and pinion assembly are to be reused, measure original shim pack and build a new shim pack to the same dimension. If baffle is in the axle assembly, it is considered part of the shim pack. Ring gears and pinions are supplied in matched sets only. If a new gear is being used, verify numbers on pinion and ring gear before proceeding with assembly. On the button end of the pinion there is a +, - , or 0 number which indicates the best running position for each particular gear set. This position is controlled by shims installed behind the inner bearing cup. If baffles or oil slingers are used, they are considered part of the adjusting shim pack. If a new gear set is being installed, note the plus or minus mark on both old and new pinions and adjust thickness of shim pack to compensate for the difference between these two numbers. Refer to chart, Fig. 5, when determining shim size. 1. Install inner shim pack and, on 9-3/4 inch ring gear axle, the oil slinger in inner or rear cup bore, then drive cup into position using suitable tool. 2. Add or remove an equal amount to the outer shim pack as was added to the inner shim pack. 3. Drive outer cup into carrier bore, then press rear pinion bearing onto pinion shaft. 4. Install drive pinion and bearing into differential carrier. 5. Install shims and outer or front pinion bearing. 6. Install companion flange, then the washer and nut on pinion shaft. 7. Measure rotating torque of pinion shaft. Rotating torque should measure 10-20 inch lbs. with original bearings installed, or 20-40 inch lbs. with new bearings installed, discounting torque required to start turning shaft. 8. If rotating torque is not within specifications, adjust shim pack as necessary. Increase outer shim pack to reduce torque, or decrease shim pack to increase torque. 9. Remove nut, washer and companion flange from pinion shaft. 10. Install oil slinger, gasket (if equipped) and oil seal onto pinion shaft. 11. Install companion flange, washer and nut and torque as described is step 7. Disassembly Fig. 9 Drive Pinion Removal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Bearing, Differential > Component Information > Service and Repair > Dana/Spicer Full Floating Axle > Page 8366 Fig. 10 Pinion Straddle Bearing Removal 1. Clamp pinion assembly in vise taking care not to damage housing or gear. 2. Hold driveshaft flange with suitable tool, then remove pinion nut and washer. 3. Remove driveshaft flange from pinion shaft using suitable puller. 4. Support housing in press as shown in Fig. 9, and press pinion from housing. Do not allow pinion to drop on floor. 5. Separate pinion flange, oil seal, front bearing and bearing retainer, driving seal from housing with suitable drift. 6. Remove bearing races from housing using suitable drift and place front bearing race with bearing. 7. Press rear bearing from pinion and place bearing with race. 8. Remove straddle bearing from axle housing using suitable drift, Fig. 10. 9. Inspect components keeping all components in order, and replace as needed. Assembly & Preload Coat components with specified lubricant during assembly. If components are reused, they should be installed in original position. 1. Press rear bearing onto pinion using suitable spacers. 2. Install front and rear bearing races in housing, using suitable drivers to ensure that races are properly seated. 3. Install straddle bearing in axle housing using straddle bearing installer tool No. J-23322 or equivalent to ensure that bearing is properly seated. 4. Insert pinion through housing, install new collapsible spacer and front bearing over pinion shaft, support pinion and press front bearing onto shaft. 5. Lubricate lips of new seal with grease and install seal using suitable driver to seat seal against shoulder of housing. 6. Install driveshaft companion flange, washer and new pinion nut. 7. Clamp housing in vise, hold flange with suitable tool and torque pinion nut just until all endplay is removed. 8. Check pinion bearing preload (rotating torque) using suitable torque wrench. 9. Continue tightening pinion nut in small increments until specified preload is obtained, checking preload after each adjustment. Exceeding specified preload will collapse spacer too far to be reused. If preload specification is exceeded, spacer must be replaced and adjustment procedure must be repeated. Do not loosen pinion nut to reduce bearing preload. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Bearing, Differential > Component Information > Service and Repair > Dana/Spicer Full Floating Axle > Page 8367 Pinion Bearing: Service and Repair Timken/Rockwell - 12 Inch Ring Gear Fig. 1 Exploded View Of Timken/Rockwell Drive Axle With 12 inch Ring Gear DISASSEMBLY 1. Tap or press pinion from cage, taking care not to damage shaft threads, then remove outer pinion bearing, Fig. 1. 2. Remove spacer from pinion, then the inner bearing, using suitable separator and press or puller. 3. If straddle bearing must be replaced, remove snap ring and washer, then the bearing, using suitable puller. 4. If bearings are to be replaced, press outer races from bearing cage, taking care not to distort cage. 5. Inspect components as outlined, and replace as needed, keeping components in order for assembly. ASSEMBLY & PRELOAD 1. When installing new cups, press them firmly against pinion bearing cage shoulders. 2. Lubricate bearings and cups with suitable lubricant. 3. Press rear thrust and radial bearings firmly against pinion shoulders, using suitable sleeve that will bear only on bearing inner race. 4. Install radial bearing lock ring, then squeeze ring into pinion shaft groove. 5. Insert pinion and bearing assembly in pinion cage and position spacer or spacer combination over pinion shaft. 6. Press front bearing firmly against spacer. 7. Rotate cage several revolutions to assure normal bearing contact. 8. Press flange or yoke against forward bearing and install washer and pinion shaft nut. 9. Place pinion and cage assembly over carrier studs, hold flange with suitable tool and torque pinion shaft nut to 240 ft. lbs. 10. Check pinion bearing preload torque. If rotating torque is not within 5 to 15 pound inches, disassemble, adjust spacer, reassemble, and recheck preload torque. Use thinner spacer to increase or thicker spacer to decrease preload. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Bearing, Differential > Component Information > Service and Repair > Dana/Spicer Full Floating Axle > Page 8368 11. Hold flange with suitable tool and remove pinion shaft nut and flange. 12. Lubricate pinion shaft oil seal and cover outer edge of seal body with non-hardening sealing compound, then press seal against cover shoulder with suitable tool. 13. Install new gasket and bearing cover. 14. Press flange against forward bearing and install washer and pinion shaft nut, torquing nut to 240 ft. lbs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Bearing, Differential > Component Information > Service and Repair > Dana/Spicer Full Floating Axle > Page 8369 Pinion Bearing: Service and Repair Corporate and Eaton 7 1/2 - 8 5/8 Inch Ring Gear PINION DEPTH ADJUSTMENT If original ring gear and pinion assembly and rear pinion bearing are to be reused, original depth adjusting shim can be used. However, if ring gear and pinion or rear pinion bearing are replaced, pinion depth must be adjusted using following procedures. 1. Install pinion bearing races to be used in housing using suitable driver. 2. Lubricate pinion bearings and install bearings in races. 3. Mount depth gauging jig in housing, noting the following: Fig. 16 Pinion depth gauge tool installation. Models w/7-1/2 inch ring gear a. On models with 7 1/2 & 7 5/8 inch ring gear, use gauge assembly tool No. J-23597-01 or equivalent, Fig. 16. Follow all tool manufacturer's recommendations when installing gauge assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Bearing, Differential > Component Information > Service and Repair > Dana/Spicer Full Floating Axle > Page 8370 Fig. 17 Pinion depth gauge tool installation. Models w/8-1/2 & 8-7/8 inch ring gear b. On models with 8 1/2 and 8 5/8 inch ring gear, use gauge assembly tool No. J-21777-01 or equivalent, Fig. 17. Follow all tool manufacturer's recommendations when installing gauge assembly. c. Assemble gauge plate onto preload stud. d. Hold pinion bearings in position, insert stud through rear bearing and pilot and front bearing and pilot, then install retaining nut and tighten nut until snug. e. Rotate tool to ensure bearings are properly seated. f. Hold preload stud and torque nut until 20 inch lbs. is required to rotate stud. Tighten nut in small increments, checking rotating torque after each adjustment, to prevent damaging bearings. g. Mount side bearing discs on arbor, using step for disc that corresponds to base of housing. h. Mount arbor and plunger assembly in housing, ensuring that side bearing discs are properly seated, install bearing caps and tighten cap bolts to prevent bearing discs from moving. 4. Mount suitable dial indicator on arbor stud with indicator contact button bearing against top of arbor plunger. 5. Preload indicator 1/2 revolution and secure to arbor mounting stud in this position. 6. Place arbor plunger on gauge plate, rotating plate as needed so that plunger rests directly on button corresponding to ring gear size. 7. Slowly rock plunger rod back and forth across button while observing dial indicator. 8. At point on button where indicator registers greatest deflection, zero dial indicator. Perform steps 7 and 8 several times to ensure correct setting. 9. Once verified zero reading is obtained, swing plunger aside until it is clear of gauge plate button and record dial indicator reading. Indicator will now read required pinion depth shim thickness for a "nominal" pinion. 10. Inspect rear face of drive pinion to be installed for a pinion code number. This number indicates in thousandths of an inch necessary modification of pinion shim thickness obtained in step 9. 11. Select pinion depth adjusting shim as follows: a. If pinion is stamped with a plus (+) number, add that number of thousandths to dimension obtained in step 9. b. If pinion is stamped with a minus (-) number, subtract that many thousandths from dimension obtained in step 9. c. If pinion is not stamped with plus or minus number, dimension obtained in step 9 is correct shim thickness. 12. Remove gauging tools and pinion bearings from housing, noting installation position of bearings. PINION INSTALLATION 1. Install selected shim onto pinion shaft, lubricate rear pinion bearing with specified axle lubricant, then press rear bearing onto pinion using suitable spacers. 2. Install new collapsible spacer onto pinion shaft, then insert pinion assembly into housing. 3. Lubricate front pinion bearing, install bearing into housing and tap bearing over pinion shaft with suitable drift while assistant holds pinion in place. Old pinion nut and suitable large washer can be used to seat front bearing on pinion, but care must be taken not to collapse spacer if this method is used. 4. Install new pinion seal in housing, coat seal lips with grease, then mount driveshaft yoke on pinion shaft, lightly tapping yoke until several pinion shaft threads protrude from yoke. 5. Coat rear of pinion washer with suitable sealer, then install washer and new pinion nut. 6. Hold driveshaft yoke with suitable tool, then alternately tighten pinion nut and rotate pinion until endplay is reduced to zero. 7. When endplay is reduced to zero, check pinion bearing preload using suitable torque wrench. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Bearing, Differential > Component Information > Service and Repair > Dana/Spicer Full Floating Axle > Page 8371 8. Continue tightening pinion nut in small increments until specified pinion bearing preload is obtained, rotating pinion and checking preload after each adjustment. Exceeding preload specification will compress collapsible spacer too far, requiring replacement of spacer. If preload specification is exceeded, spacer must be replaced and adjustment procedure must be repeated. Do not loosen pinion nut to reduce preload. 9 1/2 Inch Ring Gear PINION DEPTH ADJUSTMENT Fig. 9 Pinion Depth Gauge Installation If original ring gear and pinion assembly and rear pinion bearing are to be reused, original depth adjusting shim can be used. However, if ring gear and pinion or rear pinion bearing requires replacement, pinion depth must be adjusted using following procedures. 1. Install pinion bearing races to be used in housing using suitable driver. 2. Lubricate pinion bearings and install bearings in races. 3. Mount depth gauging jig in housing noting the following. Use gauge assembly tool No. J-21777-01, Fig. 9, or suitable equivalent. Follow all tool manufacturer's recommendations when installing gauge assembly. a. Assemble gauge plate on preload stud. b. Hold pinion bearings in position, insert stud through rear bearing and pilot, then front bearing and pilot, install retaining nut and tighten nut hand tight. c. Rotate tool to ensure that bearings are properly seated. d. Hold preload stud and tighten nut until 20 inch lbs. torque is required to rotate stud. Tighten nut in small increments, checking rotating torque after each adjustment using suitable torque wrench. e. Mount side bearing discs on arbor, using step that corresponds to base of housing. f. Mount arbor and plunger assembly in housing ensuring that side bearing discs are properly seated, install bearing caps and tighten cap bolts to prevent bearing discs from moving. 4. Mount suitable dial indicator on arbor stud with indicator contact button bearing against top of arbor plunger. 5. Preload indicator 1/2 revolution, then secure to arbor stud in this position. 6. Place arbor plunger on gauge plate, rotate plate as needed so that plunger rests directly on button corresponding to ring gear size. 7. Slowly rock plunger rod back and forth across button while observing dial indicator. 8. At point on button where indicator registers greatest deflection, zero dial indicator. Perform steps 7 and 8 several times to ensure correct setting. 9. Once verified zero setting is obtained, swing plunger aside until it is clear of gauge plate button and record dial indicator reading. Indicator will now read required pinion depth shim thickness for ``nominal'' pinion. 10. Inspect rear face of drive pinion to be installed for a pinion code number. This number indicates in thousandths of an inch necessary modification of pinion shim thickness obtained in step 9. 11. Select pinion depth adjusting shim as follows: a. If pinion is stamped with a plus (+) number, add that number of thousandths to dimension obtained in step 9. b. If pinion is stamped with a minus (-) number, subtract that many thousandths from dimension obtained in step 9. c. If pinion is not stamped with plus or minus number, dimension obtained in step 9 is correct shim thickness. 12. Remove gauging tool and pinion bearings from housing. DRIVE PINION INSTALLATION 1. Install pinion bearing races in housing, if not previously installed, using suitable drivers to ensure that races are squarely seated. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Bearing, Differential > Component Information > Service and Repair > Dana/Spicer Full Floating Axle > Page 8372 2. Install selected shim on pinion shaft, lubricate rear pinion bearing with specified axle lubricant, then press rear bearing onto pinion using suitable spacers. 3. Install new collapsible spacer on pinion and insert pinion assembly into housing. 4. Lubricate front pinion bearing, install bearing in housing and tap bearing onto pinion shaft while assistant holds pinion in place. Old pinion nut and large washer can be used to draw front bearing onto pinion, but care must be taken not to collapse spacer if this method is used. 5. Install new pinion seal in housing, coat seal lips with grease, then mount driveshaft flange on pinion shaft, lightly tapping flange until several pinion shaft threads protrude. 6. Coat rear of pinion washer with suitable sealer, then install washer and new pinion nut and adjust preload to specifications. PINION BEARING PRELOAD ADJUSTMENT 1. Ensure that pinion and bearings are properly installed, as outlined. 2. Hold driveshaft companion flange with suitable tool, then alternately tighten pinion nut and rotate pinion until endplay is reduced to zero. 3. When endplay is reduced to zero, check pinion bearing preload by rotating pinion with suitable torque wrench. 4. Continue tightening pinion nut in small increments until specified bearing preload is obtained, rotating pinion and checking preload after each adjustment. Exceeding preload specification will compress collapsible spacer too far, requiring replacement of spacer. If preload specification is exceeded, spacer must be replaced and adjustment procedure must be repeated. Do not loosen pinion nut to reduce preload. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Gear, Differential > Component Information > Adjustments > Dana/Spicer Full Floating Axle Pinion Gear: Adjustments Dana/Spicer Full Floating Axle Fig. 5 Pinion Depth Setting. If original ring gear and pinion are to be reused, measure original shim pack and build a new shim pack to the same dimension. If baffle is in the axle assembly, it is considered part of the shim pack. Ring gears and pinions are supplied in matched sets only. If a new gear is being used, verify numbers on pinion and ring gear before proceeding with assembling. On the button end of the pinion there is a (+), (-), or "0" number which indicates the best running position for each particular gear set. This position is controlled by shims installed behind the inner bearing cup. If baffles or oil slingers are used, they are considered part of the adjusting shim pack. If a new gear set is being installed, note the plus or minus mark on both old and new pinions and adjust thickness of shim pack to compensate for the difference between these two numbers. Refer to chart, Fig. 5, when determining shim size. 1. Install inner shim pack and, on 9 3/4 inch ring gear axle, the oil slinger in inner or rear cup bore, then drive cup into position using suitable tool. 2. Add or remove an equal amount to the outer shim pack as was added to the inner shim pack. 3. Drive outer cup into carrier bore, then press rear pinion bearing onto pinion shaft. 4. Install drive pinion and bearing into differential carrier. 5. Install shims and outer or front pinion bearing. 6. Install companion flange, then the washer and nut on pinion shaft. 7. Measure rotating torque of pinion shaft. Discounting torque required to start turning shaft, rotating torque should measure 6-8 inch lbs. 8. If rotating torque is not within specifications, adjust shim pack as necessary. Increase outer shim pack to reduce torque, or decrease shim pack to increase torque. 9. Remove nut, washer and companion flange from pinion shaft. 10. Install oil slinger, gasket (if equipped) and oil seal onto pinion shaft. 11. Install companion flange, washer and nut and tighten as described in step 7. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Gear, Differential > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8377 Pinion Gear: Adjustments Timken/Rockwell - 12 Inch Ring Gear Fig. 1 Timken/Rockwell drive axle w/12 inch ring gear exploded view DISASSEMBLY 1. Tap or press pinion from cage, taking care not to damage shaft threads, then remove outer pinion bearing, Fig. 1. 2. Remove spacer from pinion, then the inner bearing, using suitable separator and press or puller. 3. If straddle bearing must be replaced, remove snap ring and washer, then the bearing, using suitable puller. 4. If bearings are to be replaced, press outer races from bearing cage, taking care not to distort cage. 5. Inspect components as outlined, and replace as needed, keeping components in order for assembly. ASSEMBLY & PRELOAD ADJUSTMENT 1. When installing new cups, press them firmly against pinion bearing cage shoulders. 2. Lubricate bearings and cups with suitable lubricant. 3. Press rear thrust and radial bearings firmly against pinion shoulders, using suitable sleeve that will bear only on bearing inner race. 4. Install radial bearing lock ring, then squeeze ring into pinion shaft groove. 5. Insert pinion and bearing assembly in pinion cage and position spacer or spacer combination over pinion shaft. 6. Press front bearing firmly against spacer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Gear, Differential > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8378 7. Rotate cage several revolutions to assure normal bearing contact. 8. Press flange or yoke against forward bearing and install washer and pinion shaft nut. 9. Place pinion and cage assembly over carrier studs, hold flange with suitable tool, and torque pinion shaft nut to 350 ft. lbs. 10. Check pinion bearing preload torque. If rotating torque is not within 5 to 15 pound inches, disassemble, adjust spacer, reassemble, and recheck preload torque. Use thinner spacer to increase or thicker spacer to decrease preload. 11. Hold flange with suitable tool and remove pinion shaft nut and flange. 12. Lubricate pinion shaft oil seal and cover outer edge of seal body with non-hardening sealing compound, then press seal against cover shoulder with suitable tool. 13. Install new gasket and bearing cover. 14. Press flange against forward bearing and install washer and pinion shaft nut, torquing nut to 350 ft. lbs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Gear, Differential > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8379 Pinion Gear: Adjustments Corporate and Eaton 7 1/2 - 8 5/8 Inch Ring Gear PINION DEPTH ADJUSTMENT If original ring gear and pinion assembly and rear pinion bearing are to be reused, original depth adjusting shim can be used. However, if ring gear and pinion or rear pinion bearing are replaced, pinion depth must be adjusted using following procedures. 1. Install pinion bearing races to be used in housing using suitable driver. 2. Lubricate pinion bearings and install bearings in races. 3. Mount depth gauging jig in housing, noting the following: Fig. 16 Pinion depth gauge tool installation. Models w/7-1/2 inch ring gear a. On models with 7 1/2 & 7 5/8 inch ring gear, use gauge assembly tool No. J-23597-01 or equivalent, Fig. 16. Follow all tool manufacturer's recommendations when installing gauge assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Gear, Differential > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8380 Fig. 17 Pinion depth gauge tool installation. Models w/8-1/2 & 8-7/8 inch ring gear b. On models with 8 1/2 and 8 5/8 inch ring gear, use gauge assembly tool No. J-21777-01 or equivalent, Fig. 17. Follow all tool manufacturer's recommendations when installing gauge assembly. c. Assemble gauge plate onto preload stud. d. Hold pinion bearings in position, insert stud through rear bearing and pilot and front bearing and pilot, then install retaining nut and tighten nut until snug. e. Rotate tool to ensure bearings are properly seated. f. Hold preload stud and torque nut until 20 inch lbs. is required to rotate stud. Tighten nut in small increments, checking rotating torque after each adjustment, to prevent damaging bearings. g. Mount side bearing discs on arbor, using step for disc that corresponds to base of housing. h. Mount arbor and plunger assembly in housing, ensuring that side bearing discs are properly seated, install bearing caps and tighten cap bolts to prevent bearing discs from moving. 4. Mount suitable dial indicator on arbor stud with indicator contact button bearing against top of arbor plunger. 5. Preload indicator 1/2 revolution and secure to arbor mounting stud in this position. 6. Place arbor plunger on gauge plate, rotating plate as needed so that plunger rests directly on button corresponding to ring gear size. 7. Slowly rock plunger rod back and forth across button while observing dial indicator. 8. At point on button where indicator registers greatest deflection, zero dial indicator. Perform steps 7 and 8 several times to ensure correct setting. 9. Once verified zero reading is obtained, swing plunger aside until it is clear of gauge plate button and record dial indicator reading. Indicator will now read required pinion depth shim thickness for a "nominal" pinion. 10. Inspect rear face of drive pinion to be installed for a pinion code number. This number indicates in thousandths of an inch necessary modification of pinion shim thickness obtained in step 9. 11. Select pinion depth adjusting shim as follows: a. If pinion is stamped with a plus (+) number, add that number of thousandths to dimension obtained in step 9. b. If pinion is stamped with a minus (-) number, subtract that many thousandths from dimension obtained in step 9. c. If pinion is not stamped with plus or minus number, dimension obtained in step 9 is correct shim thickness. 12. Remove gauging tools and pinion bearings from housing, noting installation position of bearings. PINION INSTALLATION 1. Install selected shim onto pinion shaft, lubricate rear pinion bearing with specified axle lubricant, then press rear bearing onto pinion using suitable spacers. 2. Install new collapsible spacer onto pinion shaft, then insert pinion assembly into housing. 3. Lubricate front pinion bearing, install bearing into housing and tap bearing over pinion shaft with suitable drift while assistant holds pinion in place. Old pinion nut and suitable large washer can be used to seat front bearing on pinion, but care must be taken not to collapse spacer if this method is used. 4. Install new pinion seal in housing, coat seal lips with grease, then mount driveshaft yoke on pinion shaft, lightly tapping yoke until several pinion shaft threads protrude from yoke. 5. Coat rear of pinion washer with suitable sealer, then install washer and new pinion nut. 6. Hold driveshaft yoke with suitable tool, then alternately tighten pinion nut and rotate pinion until endplay is reduced to zero. 7. When endplay is reduced to zero, check pinion bearing preload using suitable torque wrench. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Gear, Differential > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8381 8. Continue tightening pinion nut in small increments until specified pinion bearing preload is obtained, rotating pinion and checking preload after each adjustment. Exceeding preload specification will compress collapsible spacer too far, requiring replacement of spacer. If preload specification is exceeded, spacer must be replaced and adjustment procedure must be repeated. Do not loosen pinion nut to reduce preload. 9 1/2 Inch Ring Gear Fig. 9 Pinion depth gauge installation PINION DEPTH, ADJUST If original ring gear and pinion assembly and rear pinion bearing are to be reused, original depth adjusting shim can be used. However, if ring gear and pinion or rear pinion bearing requires replacement, pinion depth must be adjusted using following procedures. 1. Install pinion bearing races to be used in housing using suitable driver. 2. Lubricate pinion bearings and install bearings in races. 3. Mount depth gauging jig in housing noting the following. Use gauge assembly J-21777-01, Fig. 9, or suitable equivalent. Follow all tool manufacturer's recommendations when installing gauge assembly. a. Assemble gauge plate on preload stud. b. Hold pinion bearings in position, insert stud through rear bearing and pilot, then front bearing and pilot, install retaining nut and tighten nut hand tight. c. Rotate tool to ensure that bearings are properly seated. d. Hold preload stud and tighten nut until 20 inch lbs. torque is required to rotate stud. Tighten nut in small increments, checking rotating torque after each adjustment using suitable torque wrench. e. Mount side bearing discs on arbor, using step that corresponds to base of housing. f. Mount arbor and plunger assembly in housing ensuring that side bearing discs are properly seated, install bearing caps and tighten cap bolts to prevent bearing discs from moving. 4. Mount suitable dial indicator on arbor stud with indicator contact button bearing against top of arbor plunger. 5. Preload indicator 1/2 revolution, then secure to arbor stud in this position. 6. Place arbor plunger on gauge plate, rotate plate as needed so that plunger rests directly on button corresponding to ring gear size. 7. Slowly rock plunger rod back and forth across button while observing dial indicator. 8. At point on button where indicator registers greatest deflection, zero dial indicator. Perform steps 7 and 8 several times to ensure correct setting. 9. Once verified zero setting is obtained, swing plunger aside until it is clear of gauge plate button and record dial indicator reading. Indicator will now read required pinion depth shim thickness for ``nominal'' pinion. 10. Inspect rear face of drive pinion to be installed for a pinion code number. This number indicates in thousandths of an inch necessary modification of pinion shim thickness obtained in step 9. 11. Select pinion depth adjusting shim as follows: a. If pinion is stamped with a plus (+) number, add that number of thousandths to dimension obtained in step 9. b. If pinion is stamped with a minus ( - ) number, subtract that many thousandths from dimension obtained in step 9. c. If pinion is not stamped with plus or minus number, dimension obtained in step 9 is correct shim thickness. 12. Remove gauging tool and pinion bearings from housing. DRIVE PINION, INSTALL 1. Install pinion bearing races in housing, if not previously installed, using suitable drivers to ensure that races are squarely seated. 2. Install selected shim on pinion shaft, lubricate rear pinion bearing with specified axle lubricant, then press rear bearing onto pinion using suitable spacers. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Gear, Differential > Component Information > Adjustments > Dana/Spicer Full Floating Axle > Page 8382 3. Install new collapsible spacer on pinion and insert pinion assembly into housing. 4. Lubricate front pinion bearing, install bearing in housing and tap bearing onto pinion shaft while assistant holds pinion in place. Old pinion nut and large washer can be used to draw front bearing onto pinion, but care must be taken not to collapse spacer if this method is used. 5. Install new pinion seal in housing, coat seal lips with grease, then mount driveshaft flange on pinion shaft, lightly tapping flange until several pinion shaft threads protrude. 6. Coat rear of pinion washer with suitable sealer, then install washer and new pinion nut and adjust preload to specifications. PINION BEARING PRELOAD ADJUSTMENT 1. Ensure pinion and bearings are properly installed, as outlined. 2. Hold driveshaft companion flange with suitable tool, then alternately tighten pinion nut and rotate pinion until endplay is reduced to zero. 3. Using and inch lb. torque wrench, check pinion preload by rotating pinion with wrench. Preload should be at 20-25 inch lbs. or less on new bearings or 10-15 inch lbs. on used bearings. 4. Continue tightening pinion nut in small increments until specified bearing preload is obtained, rotating pinion and checking preload after each adjustment. Exceeding preload specification will compress collapsible spacer too far, requiring replacement of spacer. If preload specification is exceeded, spacer must be replaced and adjustment procedure must be repeated. Do not loosen pinion nut to reduce preload. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Gear, Differential > Component Information > Service and Repair > Corporate and Eaton Pinion Gear: Service and Repair Corporate and Eaton 7 1/2 - 8 5/8 Inch Ring Gear PINION DEPTH ADJUSTMENT If original ring gear and pinion assembly and rear pinion bearing are to be reused, original depth adjusting shim can be used. However, if ring gear and pinion or rear pinion bearing are replaced, pinion depth must be adjusted using following procedures. 1. Install pinion bearing races to be used in housing using suitable driver. 2. Lubricate pinion bearings and install bearings in races. 3. Mount depth gauging jig in housing, noting the following: Fig. 16 Pinion depth gauge tool installation. Models w/7-1/2 inch ring gear a. On models with 7 1/2 & 7 5/8 inch ring gear, use gauge assembly tool No. J-23597-01 or equivalent, Fig. 16. Follow all tool manufacturer's recommendations when installing gauge assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Gear, Differential > Component Information > Service and Repair > Corporate and Eaton > Page 8385 Fig. 17 Pinion depth gauge tool installation. Models w/8-1/2 & 8-7/8 inch ring gear b. On models with 8 1/2 and 8 5/8 inch ring gear, use gauge assembly tool No. J-21777-01 or equivalent, Fig. 17. Follow all tool manufacturer's recommendations when installing gauge assembly. c. Assemble gauge plate onto preload stud. d. Hold pinion bearings in position, insert stud through rear bearing and pilot and front bearing and pilot, then install retaining nut and tighten nut until snug. e. Rotate tool to ensure bearings are properly seated. f. Hold preload stud and torque nut until 20 inch lbs. is required to rotate stud. Tighten nut in small increments, checking rotating torque after each adjustment, to prevent damaging bearings. g. Mount side bearing discs on arbor, using step for disc that corresponds to base of housing. h. Mount arbor and plunger assembly in housing, ensuring that side bearing discs are properly seated, install bearing caps and tighten cap bolts to prevent bearing discs from moving. 4. Mount suitable dial indicator on arbor stud with indicator contact button bearing against top of arbor plunger. 5. Preload indicator 1/2 revolution and secure to arbor mounting stud in this position. 6. Place arbor plunger on gauge plate, rotating plate as needed so that plunger rests directly on button corresponding to ring gear size. 7. Slowly rock plunger rod back and forth across button while observing dial indicator. 8. At point on button where indicator registers greatest deflection, zero dial indicator. Perform steps 7 and 8 several times to ensure correct setting. 9. Once verified zero reading is obtained, swing plunger aside until it is clear of gauge plate button and record dial indicator reading. Indicator will now read required pinion depth shim thickness for a "nominal" pinion. 10. Inspect rear face of drive pinion to be installed for a pinion code number. This number indicates in thousandths of an inch necessary modification of pinion shim thickness obtained in step 9. 11. Select pinion depth adjusting shim as follows: a. If pinion is stamped with a plus (+) number, add that number of thousandths to dimension obtained in step 9. b. If pinion is stamped with a minus (-) number, subtract that many thousandths from dimension obtained in step 9. c. If pinion is not stamped with plus or minus number, dimension obtained in step 9 is correct shim thickness. 12. Remove gauging tools and pinion bearings from housing, noting installation position of bearings. PINION INSTALLATION 1. Install selected shim onto pinion shaft, lubricate rear pinion bearing with specified axle lubricant, then press rear bearing onto pinion using suitable spacers. 2. Install new collapsible spacer onto pinion shaft, then insert pinion assembly into housing. 3. Lubricate front pinion bearing, install bearing into housing and tap bearing over pinion shaft with suitable drift while assistant holds pinion in place. Old pinion nut and suitable large washer can be used to seat front bearing on pinion, but care must be taken not to collapse spacer if this method is used. 4. Install new pinion seal in housing, coat seal lips with grease, then mount driveshaft yoke on pinion shaft, lightly tapping yoke until several pinion shaft threads protrude from yoke. 5. Coat rear of pinion washer with suitable sealer, then install washer and new pinion nut. 6. Hold driveshaft yoke with suitable tool, then alternately tighten pinion nut and rotate pinion until endplay is reduced to zero. 7. When endplay is reduced to zero, check pinion bearing preload using suitable torque wrench. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Gear, Differential > Component Information > Service and Repair > Corporate and Eaton > Page 8386 8. Continue tightening pinion nut in small increments until specified pinion bearing preload is obtained, rotating pinion and checking preload after each adjustment. Exceeding preload specification will compress collapsible spacer too far, requiring replacement of spacer. If preload specification is exceeded, spacer must be replaced and adjustment procedure must be repeated. Do not loosen pinion nut to reduce preload. 9 1/2 Inch Ring Gear PINION DEPTH ADJUSTMENT Fig. 9 Pinion Depth Gauge Installation If original ring gear and pinion assembly and rear pinion bearing are to be reused, original depth adjusting shim can be used. However, if ring gear and pinion or rear pinion bearing requires replacement, pinion depth must be adjusted using following procedures. 1. Install pinion bearing races to be used in housing using suitable driver. 2. Lubricate pinion bearings and install bearings in races. 3. Mount depth gauging jig in housing noting the following. Use gauge assembly tool No. J-21777-01, Fig. 9, or suitable equivalent. Follow all tool manufacturer's recommendations when installing gauge assembly. a. Assemble gauge plate on preload stud. b. Hold pinion bearings in position, insert stud through rear bearing and pilot, then front bearing and pilot, install retaining nut and tighten nut hand tight. c. Rotate tool to ensure that bearings are properly seated. d. Hold preload stud and tighten nut until 20 inch lbs. torque is required to rotate stud. Tighten nut in small increments, checking rotating torque after each adjustment using suitable torque wrench. e. Mount side bearing discs on arbor, using step that corresponds to base of housing. f. Mount arbor and plunger assembly in housing ensuring that side bearing discs are properly seated, install bearing caps and tighten cap bolts to prevent bearing discs from moving. 4. Mount suitable dial indicator on arbor stud with indicator contact button bearing against top of arbor plunger. 5. Preload indicator 1/2 revolution, then secure to arbor stud in this position. 6. Place arbor plunger on gauge plate, rotate plate as needed so that plunger rests directly on button corresponding to ring gear size. 7. Slowly rock plunger rod back and forth across button while observing dial indicator. 8. At point on button where indicator registers greatest deflection, zero dial indicator. Perform steps 7 and 8 several times to ensure correct setting. 9. Once verified zero setting is obtained, swing plunger aside until it is clear of gauge plate button and record dial indicator reading. Indicator will now read required pinion depth shim thickness for ``nominal'' pinion. 10. Inspect rear face of drive pinion to be installed for a pinion code number. This number indicates in thousandths of an inch necessary modification of pinion shim thickness obtained in step 9. 11. Select pinion depth adjusting shim as follows: a. If pinion is stamped with a plus (+) number, add that number of thousandths to dimension obtained in step 9. b. If pinion is stamped with a minus (-) number, subtract that many thousandths from dimension obtained in step 9. c. If pinion is not stamped with plus or minus number, dimension obtained in step 9 is correct shim thickness. 12. Remove gauging tool and pinion bearings from housing. DRIVE PINION INSTALLATION 1. Install pinion bearing races in housing, if not previously installed, using suitable drivers to ensure that races are squarely seated. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Gear, Differential > Component Information > Service and Repair > Corporate and Eaton > Page 8387 2. Install selected shim on pinion shaft, lubricate rear pinion bearing with specified axle lubricant, then press rear bearing onto pinion using suitable spacers. 3. Install new collapsible spacer on pinion and insert pinion assembly into housing. 4. Lubricate front pinion bearing, install bearing in housing and tap bearing onto pinion shaft while assistant holds pinion in place. Old pinion nut and large washer can be used to draw front bearing onto pinion, but care must be taken not to collapse spacer if this method is used. 5. Install new pinion seal in housing, coat seal lips with grease, then mount driveshaft flange on pinion shaft, lightly tapping flange until several pinion shaft threads protrude. 6. Coat rear of pinion washer with suitable sealer, then install washer and new pinion nut and adjust preload to specifications. PINION BEARING PRELOAD ADJUSTMENT 1. Ensure that pinion and bearings are properly installed, as outlined. 2. Hold driveshaft companion flange with suitable tool, then alternately tighten pinion nut and rotate pinion until endplay is reduced to zero. 3. When endplay is reduced to zero, check pinion bearing preload by rotating pinion with suitable torque wrench. 4. Continue tightening pinion nut in small increments until specified bearing preload is obtained, rotating pinion and checking preload after each adjustment. Exceeding preload specification will compress collapsible spacer too far, requiring replacement of spacer. If preload specification is exceeded, spacer must be replaced and adjustment procedure must be repeated. Do not loosen pinion nut to reduce preload. Disassembly Fig. 9 Drive Pinion Removal Fig. 10 Pinion Straddle Bearing Removal 1. Clamp pinion assembly in vise taking care not to damage housing or gear. 2. Hold driveshaft flange with suitable tool, then remove pinion nut and washer. 3. Remove driveshaft flange from pinion shaft using suitable puller. 4. Support housing in press as shown in Fig. 9, and press pinion from housing. Do not allow pinion to drop on floor. 5. Separate pinion flange, oil seal, front bearing and bearing retainer, driving seal from housing with suitable drift. 6. Remove bearing races from housing using suitable drift and place front bearing race with bearing. 7. Press rear bearing from pinion and place bearing with race. 8. Remove straddle bearing from axle housing using suitable drift, Fig. 10. 9. Inspect components keeping all components in order, and replace as needed. Assembly & Preload Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Gear, Differential > Component Information > Service and Repair > Corporate and Eaton > Page 8388 Coat components with specified lubricant during assembly. If components are reused, they should be installed in original position. 1. Press rear bearing onto pinion using suitable spacers. 2. Install front and rear bearing races in housing, using suitable drivers to ensure that races are properly seated. 3. Install straddle bearing in axle housing using straddle bearing installer tool No. J-23322 or equivalent to ensure that bearing is properly seated. 4. Insert pinion through housing, install new collapsible spacer and front bearing over pinion shaft, support pinion and press front bearing onto shaft. 5. Lubricate lips of new seal with grease and install seal using suitable driver to seat seal against shoulder of housing. 6. Install driveshaft companion flange, washer and new pinion nut. 7. Clamp housing in vise, hold flange with suitable tool and torque pinion nut just until all endplay is removed. 8. Check pinion bearing preload (rotating torque) using suitable torque wrench. 9. Continue tightening pinion nut in small increments until specified preload is obtained, checking preload after each adjustment. Exceeding specified preload will collapse spacer too far to be reused. If preload specification is exceeded, spacer must be replaced and adjustment procedure must be repeated. Do not loosen pinion nut to reduce bearing preload. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Gear, Differential > Component Information > Service and Repair > Corporate and Eaton > Page 8389 Pinion Gear: Service and Repair Dana/Spicer Full Floating Axle Fig. 5 Pinion Depth Setting. If original ring gear and pinion are to be reused, measure original shim pack and build a new shim pack to the same dimension. If baffle is in the axle assembly, it is considered part of the shim pack. Ring gears and pinions are supplied in matched sets only. If a new gear is being used, verify numbers on pinion and ring gear before proceeding with assembling. On the button end of the pinion there is a (+), (-), or "0" number which indicates the best running position for each particular gear set. This position is controlled by shims installed behind the inner bearing cup. If baffles or oil slingers are used, they are considered part of the adjusting shim pack. If a new gear set is being installed, note the plus or minus mark on both old and new pinions and adjust thickness of shim pack to compensate for the difference between these two numbers. Refer to chart, Fig. 5, when determining shim size. 1. Install inner shim pack and, on 9 3/4 inch ring gear axle, the oil slinger in inner or rear cup bore, then drive cup into position using suitable tool. 2. Add or remove an equal amount to the outer shim pack as was added to the inner shim pack. 3. Drive outer cup into carrier bore, then press rear pinion bearing onto pinion shaft. 4. Install drive pinion and bearing into differential carrier. 5. Install shims and outer or front pinion bearing. 6. Install companion flange, then the washer and nut on pinion shaft. 7. Measure rotating torque of pinion shaft. Discounting torque required to start turning shaft, rotating torque should measure 6-8 inch lbs. 8. If rotating torque is not within specifications, adjust shim pack as necessary. Increase outer shim pack to reduce torque, or decrease shim pack to increase torque. 9. Remove nut, washer and companion flange from pinion shaft. 10. Install oil slinger, gasket (if equipped) and oil seal onto pinion shaft. 11. Install companion flange, washer and nut and tighten as described in step 7. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Gear, Differential > Component Information > Service and Repair > Corporate and Eaton > Page 8390 Pinion Gear: Service and Repair Timken/Rockwell - 12 Inch Ring Gear Fig. 1 Exploded View Of Timken/Rockwell Drive Axle With 12 inch Ring Gear DISASSEMBLY 1. Tap or press pinion from cage, taking care not to damage shaft threads, then remove outer pinion bearing, Fig. 1. 2. Remove spacer from pinion, then the inner bearing, using suitable separator and press or puller. 3. If straddle bearing must be replaced, remove snap ring and washer, then the bearing, using suitable puller. 4. If bearings are to be replaced, press outer races from bearing cage, taking care not to distort cage. 5. Inspect components as outlined, and replace as needed, keeping components in order for assembly. ASSEMBLY & PRELOAD 1. When installing new cups, press them firmly against pinion bearing cage shoulders. 2. Lubricate bearings and cups with suitable lubricant. 3. Press rear thrust and radial bearings firmly against pinion shoulders, using suitable sleeve that will bear only on bearing inner race. 4. Install radial bearing lock ring, then squeeze ring into pinion shaft groove. 5. Insert pinion and bearing assembly in pinion cage and position spacer or spacer combination over pinion shaft. 6. Press front bearing firmly against spacer. 7. Rotate cage several revolutions to assure normal bearing contact. 8. Press flange or yoke against forward bearing and install washer and pinion shaft nut. 9. Place pinion and cage assembly over carrier studs, hold flange with suitable tool and torque pinion shaft nut to 240 ft. lbs. 10. Check pinion bearing preload torque. If rotating torque is not within 5 to 15 pound inches, disassemble, adjust spacer, reassemble, and recheck preload torque. Use thinner spacer to increase or thicker spacer to decrease preload. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Pinion Gear, Differential > Component Information > Service and Repair > Corporate and Eaton > Page 8391 11. Hold flange with suitable tool and remove pinion shaft nut and flange. 12. Lubricate pinion shaft oil seal and cover outer edge of seal body with non-hardening sealing compound, then press seal against cover shoulder with suitable tool. 13. Install new gasket and bearing cover. 14. Press flange against forward bearing and install washer and pinion shaft nut, torquing nut to 240 ft. lbs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Seals and Gaskets, Differential > System Information > Service and Repair > Semi-Floating Axle 8-1/2, 8-5/8 and 9-1/2 Inch Ring Gear Seals and Gaskets: Service and Repair Semi-Floating Axle 8-1/2, 8-5/8 and 9-1/2 Inch Ring Gear - Tools Required: J 8614-01 Companion Flange Holder: - J 8614-02 Companion Flange Remover - J 24388 Pinion Oil Seal Installer (American Axle 9 1/2 inch ring gear axle) - J 22836 Pinion Oil Seal Installer (American Axle 8 1/2 and 8 5/8 inch ring gear axles) - J 22804 Pinion Oil Seal Spacer - The pinion oil seal and the companion flange may be replaced with the carrier assembly installed in the vehicle. REMOVE OR DISCONNECT - Raise the vehicle on a hoist and support with safety stands. 1. Rear wheels and drums. Important: It is essential that the positions of all driveline components relative to the propeller shaft and axles be observed and accurately reference marked prior to disassembly. These components include the propeller shafts, drive axles, pinion flanges, output shafts, etc. All components must be reassembled in the exact relationship to each other as they were when removed. Specifications and torque values, as well as any measurements made prior to disassembly, must be followed. - Accurately mark the installed position of the rear propeller shaft. 2. Propeller shaft. A. Use a piece of tape to hold the bearing caps. B. Secure the propeller shaft up and out of the way so as not to put unnecessary stress on the universal joints. C. Measure, using an inch-pound torque wrench, the amount of torque required to turn the pinion. Record this measurement for reassembly. This will give combined pinion bearing, seal, carrier bearing, axle bearing and seal preload. D. Make an accurate alignment mark on the pinion stem, pinion flange, and pinion flange nut. Also record the number of exposed threads on the pinion stem for reference. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Seals and Gaskets, Differential > System Information > Service and Repair > Semi-Floating Axle 8-1/2, 8-5/8 and 9-1/2 Inch Ring Gear > Page 8396 3. Pinion flange nut and washer. - Hold the pinion flange with J 8614-01. 4. Pinion flange using J 8614-01. - Use container to catch lubricant. 5. Oil seal. - Pry the oil seal from the bore. Do not damage the machined surfaces. Thoroughly clean foreign material from the contact area. - Replace parts as necessary. INSTALL OR CONNECT NOTICE: Always use the correct fastener in the proper location. When you replace a fastener, use ONLY the exact part number for that application. The manufacturer will call out those fasteners that require a replacement after removal. The manufacturer will also call out the fasteners that require thread lockers or thread sealant. UNLESS OTHERWISE SPECIFIED, do not use supplemental coatings (paints, greases, or other corrosion inhibitors on threaded fasteners or fastener joint interfaces. Generally, such coatings adversely affect the fastener torque and joint clamping force, and may damage the fastener. When you Install fasteners, use the correct tightening sequence and specifications. Following these instructions can help you avoid damage to parts and systems. 1. Oil seal into the bore using J 22804-1 and either J 22388 (9 1/2 inch ring gear) or J 22836 (8 1/2 and 8 5/8 ring gears). Turn J 22804-1 from installed position 180° to ensure proper installation against the pinion flange. Lubricate the cavity between the new seal lips with a high melting point bearing lubricant. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Seals and Gaskets, Differential > System Information > Service and Repair > Semi-Floating Axle 8-1/2, 8-5/8 and 9-1/2 Inch Ring Gear > Page 8397 2. Pinion flange using J 8614-01. - Use scribed marks for installation. Important: Do not attempt to hammer the pinion flange onto the pinion stem. 3. Washer and a new nut. - Tighten: A. The nut on the pinion stem as close to the original marks as possible without going past the mark. Use the reference mark and the thread count as reference. B. The nut a little at a time and turn the pinion flange several times after each tightening to set the rollers. Measure - Using an inch-pound torque wrench, the torque required to rotate the pinion. Compare this with the required rotating torque recorded earlier. Continue tightening and measuring a little at a time until the same preload is achieved. Important: - If the original preload torque value was less than 3 (inch lbs.) then reset the torque specification to 3-5 (inch lbs.). - Align the propeller shaft with the alignment marks made previously. 4. Propeller shaft. 5. Retainers and bolts. - Tighten bolts to 20 Nm (15 ft. lbs.). 6. Rear wheels and drums. 7. Lubricant to the rear axle as necessary. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Seals and Gaskets, Differential > System Information > Service and Repair > Semi-Floating Axle 8-1/2, 8-5/8 and 9-1/2 Inch Ring Gear > Page 8398 Seals and Gaskets: Service and Repair Full-Floating Axle 10-1/2 Inch Ring Gear - Tools Required: - J 8614-01 Companion Flange Holder - J 8614-02 Companion Flange Remover - J 24384 Pinion Oil Seal Installer (American Axle 10 1/2 inch ring gear axle). - The pinion oil seal and the companion flange may be replaced with the carrier assembly installed in the vehicle. REMOVE OR DISCONNECT - Raise the vehicle on a hoist and support with safety stands. 1. Axle shafts. Important: It is essential that the positions of all driveline components relative to the propeller shaft and axles be observed and accurately reference marked prior to disassembly. These components Include the propeller shafts, drive axles, pinion flanges, output shafts, etc. All components must be reassembled in the exact relationship to each other as they were when removed. Specifications and torque values, as well as any measurements made prior to disassembly, must be followed. - Accurately mark the installed position of the rear propeller shaft. 2. Propeller shaft. A. Use a piece of tape to hold the bearing caps. B. Secure the propeller shaft up and out of the way so as not to put unnecessary stress on the universal joints. C. Measure, using an inch-pound torque wrench, the amount of torque required to turn the pinion. Record this measurement for reassembly. This will give combined pinion bearing, seal, and carrier bearing preload. D. Make an accurate alignment mark on the pinion stem, pinion flange, and pinion flange nut. Also record the number of exposed threads on the pinion stem for reference. 3. Pinion flange nut and washer. - Hold the pinion flange with J 8614-01. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Seals and Gaskets, Differential > System Information > Service and Repair > Semi-Floating Axle 8-1/2, 8-5/8 and 9-1/2 Inch Ring Gear > Page 8399 4. Pinion flange using J 8614-01. - Use container to catch lubricant. 5. Oil seal. - Pry the oil seal from the bore. Do not damage the machined surfaces. Thoroughly clean foreign material from the contact area. - Replace parts as necessary. INSTALL OR CONNECT NOTICE: Always use the correct fastener in the proper location. When you replace a fastener, use ONLY the exact part number for that application. The manufacturer will call out those fasteners that require a replacement after removal. The manufacturer will also call out the fasteners that require thread lockers or thread sealant. UNLESS OTHERWISE SPECIFIED, do not use supplemental coatings (paints, greases, or other corrosion inhibitors on threaded fasteners or fastener joint interfaces. Generally, such coatings adversely affect the fastener torque and joint clamping force, and may damage the fastener. When you Install fasteners, use the correct tightening sequence and specifications. Following these instructions can help you avoid damage to parts and systems. 1. Oil seal into the bore using J 24384. - Lubricate the cavity between the new seal lips with a high melting point bearing lubricant. 2. Pinion flange. - Use scribed marks for installation. Important: Do not attempt to hammer the pinion flange onto the pinion stem. 3. Washer and a new nut. - Tighten: A. The nut on the pinion stem as close to the original marks as possible without going past the mark. Use the reference mark and the thread count as reference. B. The nut a little at a time and turn the pinion flange several times after each tightening to set the rollers. Measure - Using an inch-pound torque wrench, the torque required to rotate the pinion. Compare this with the required rotating torque recorded earlier. Continue tightening and measuring a little at a time until the same preload is achieved. Important: If the original preload torque value was less than 3 (inch lbs.) then reset the torque specification to 3-5 (inch lbs.). - Align the propeller shaft with the alignment marks made previously. 4. Propeller shaft. 5. Retainers and bolts. - Tighten bolts to 20 Nm (15 ft. lbs.). 6. Axle shafts. 7. Lubricant to the rear axle as necessary. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Seals and Gaskets, Differential > System Information > Service and Repair > Semi-Floating Axle 8-1/2, 8-5/8 and 9-1/2 Inch Ring Gear > Page 8400 Seals and Gaskets: Service and Repair Full-Floating Axle 11 Inch Ring Gear - Tool Required: J 8614-01 Pinion Flange Holder and Remover - J 24384 Pinion Oil Seal Installer (Dana 11 inch ring gear axle). - The pinion oil seal and the pinion flange may be replaced with the carrier assembly installed in the vehicle. REMOVE OR DISCONNECT - Raise the vehicle. 1. Propeller shaft. Important: Scribe a line on the pinion stem, pinion nut and pinion flange to be used as an installation guide. 2. Nut using J 8614-01. 3. Flange using J 8614-01. 4. Oil seal. - Use the special nut and forcing screw to remove the flange. - Pry the oil seal from the bore. Do not damage the machined surfaces. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Seals and Gaskets, Differential > System Information > Service and Repair > Semi-Floating Axle 8-1/2, 8-5/8 and 9-1/2 Inch Ring Gear > Page 8401 - Thoroughly clean foreign material from the contact area. Inspect - Oil seal mating surfaces for any burrs which may cause seal failure. - Flange deflector for any abnormality such as cracking or distortion. - Replace any part which shows any of the above conditions. INSTALL OR CONNECT NOTICE: Always use the correct fastener in the proper location. When you replace a fastener, use ONLY the exact part number for that application. The manufacturer will call out those fasteners that require a replacement after removal. The manufacturer will also call out the fasteners that require thread lockers or thread sealant. UNLESS OTHERWISE SPECIFIED, do not use supplemental coatings (paints, greases, or other corrosion inhibitors on threaded fasteners or fastener joint interfaces. Generally, such coatings adversely affect the fastener torque and joint clamping force, and may damage the fastener. When you install fasteners, use the correct tightening sequence and specifications. Following these instructions can help you avoid damage to parts and systems. 1. Oil seal into the bore using J 24384. - Lubricate the inside diameter of the new oil seal with extreme pressure lubricant. - Pack the cavity between the pinion stem, pinion flange and pinion nut washer with a non-hardening sealer such as Permatex(R) Type A or equivalent. Do not coat the bearing. 2. Flange using J 8614. - Use marks scribed previously for installation. 3. A new pinion nut, using J 8614-01. - Use marks scribed previously for installation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Differential Assembly > Seals and Gaskets, Differential > System Information > Service and Repair > Semi-Floating Axle 8-1/2, 8-5/8 and 9-1/2 Inch Ring Gear > Page 8402 - Tighten pinion nut to 596 to 678 Nm (440 to 500 ft. lbs.). 4. Propeller shaft. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive Axles, Bearings and Joints > Axle Bearing > Component Information > Service and Repair > Rockwell Full Floating Axle Axle Bearing: Service and Repair Rockwell Full Floating Axle Ensure the brakes are completely released and do not drag. Check wheel bearing play by grasping the tire at the top and pulling and pushing back and forth, or by using a pry bar under the tire. If the wheel bearings are properly adjusted, movement of hub or disc will be barely noticeable. If the movement is excessive, adjust the bearings as follows: 1. Raise and support vehicle. 2. Remove axle shaft. 3. Remove retaining nut and lock washer. 4. Using nut wrench tool No. J-25510, or equivalent, torque adjusting nut, with hub rotating, to 50.0 ft. lbs. Ensure bearing surfaces are in contact, then back adjusting nut off 1/8 turn. 5. Install lock washer, the bend tang over flat of adjusting nut. 6. Install retaining nut and torque to 250 ft. lbs. 7. Install axle shaft. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive Axles, Bearings and Joints > Axle Bearing > Component Information > Service and Repair > Rockwell Full Floating Axle > Page 8408 Axle Bearing: Service and Repair Dana/Spicer Full Floating Axle Wheel Bearing, Adjust Ensure the brakes are completely released and do not drag. Check wheel bearing play by grasping the tire at the top and pulling and pushing back and forth, or by using a pry bar under the tire. If the wheel bearings are properly adjusted, movement of the brake drum in relation to the brake flange plate will be barely noticeable and the wheel will turn freely. If the movement is excessive, adjust the bearings as follows: 1. Back off attaching nut until just loose, but not more than one slot of the lock or the axle spindle using wheel bearing nut wrench tool No. J-2222-C, or equivalent. 2. Align adjusting nut slot with keyway in the axle spindle. Hub & Bearing 1. Raise and support vehicle. 2. Remove axle shaft. 3. Remove hub and drum. 4. Remove oil seal, inner bearing and retaining ring. 5. Remove outer bearing. 6. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive Axles, Bearings and Joints > Axle Shaft Assembly > Component Information > Service and Repair > Rockwell Full Floating Axle Axle Shaft Assembly: Service and Repair Rockwell Full Floating Axle REAR AXLE SHAFT 1. Raise and support vehicle, then remove axle hub cap. 2. Thread slide hammer tool No. J-2619-01, or equivalent, into tapped hole on axle shaft flange. 3. Remove axle from housing. 4. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive Axles, Bearings and Joints > Axle Shaft Assembly > Component Information > Service and Repair > Rockwell Full Floating Axle > Page 8413 Axle Shaft Assembly: Service and Repair Dana/Spicer Full Floating Axle Axle Shaft Replace Full-Floating Axle (10 1/2 Inch Ring Gear) Fig. 3 Axle, Hub & Drum Components. Remove or Disconnect 1. Bolts (55). Rap the axle shaft (53) flange lightly with a soft faced hammer to loosen the shaft. - Grip the rib on the axle shaft (53) flange with a locking plier and twist, to start shaft removal. 2. Axle shaft (52) from the tube. Clean - Axle shaft (53) flange. Remove old RTV or gasket (51). - Outside face of the hub assembly. Inspect - All parts and replace as necessary. Install or Connect 1. Axle shaft (53) with a gasket or RTV applied. Be sure the shaft splines mesh into the differential side gear. - Align the axle shaft holes with the hub holes. 2. Bolts (55). Tighten bolts (55) to 156 Nm (115 ft. lbs.). Wheel Bearing, Adjust REAR WHEEL BEARING Ensure the brakes are completely released and do not drag. Check wheel bearing play by grasping the tire at the top and pulling and pushing back and forth, or by using a pry bar under the tire. If the wheel bearings are properly adjusted, movement of the brake drum in relation to the brake flange plate will be barely noticeable and the wheel will turn freely. If the movement is excessive, adjust the bearings as follows: 1. Back off attaching nut until just loose, but not more than one slot of the lock or the axle spindle using wheel bearing nut wrench tool No. J-2222-C, or equivalent. 2. Align adjusting nut slot with keyway in the axle spindle. Hub & Bearing Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive Axles, Bearings and Joints > Axle Shaft Assembly > Component Information > Service and Repair > Rockwell Full Floating Axle > Page 8414 REAR WHEEL BEARING 1. Raise and support vehicle. 2. Remove axle shaft. 3. Remove hub and drum. 4. Remove oil seal, inner bearing and retaining ring. 5. Remove outer bearing. 6. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive Axles, Bearings and Joints > Axle Shaft Assembly > Component Information > Service and Repair > Rockwell Full Floating Axle > Page 8415 Axle Shaft Assembly: Service and Repair Semi-Floating Axle (8 1/2, 8 5/8 and 9 1/2 Inch Ring Gear) REAR AXLE SHAFT, OIL SEAL, AND BEARING REPLACEMENT - Tools Required: J 2619-01 Slide Hammer with Adapter - J 23689 Axle Shaft Bearing Remover (large shaft 8 1/2 and 8 5/8 inch ring gear). - J 29712 Axle Shaft Bearing Remover (9 1/2 inch ring gear) - J 8092 Driver Handle - J 21128 Axle Shaft and Pinion Oil Seal Installer - J 23690 Axle Shaft Bearing Installer - J 29709 Axle Shaft Bearing Installer (9 1/2 inch ring gear) - J 29713 Axle Shaft Seal Installer (9 1/2 inch ring gear) REMOVE OR DISCONNECT - Raise the vehicle on a hoist. 1. Wheel and tire assembly. 2. Brake drum. - Clean the dirt from around the carrier cover. 3. Carrier cover. - Catch the oil in a drain pan. - Remove gasket material if used. 4. Screw (A). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive Axles, Bearings and Joints > Axle Shaft Assembly > Component Information > Service and Repair > Rockwell Full Floating Axle > Page 8416 5. Pinion shaft (B). - Remove the shaft from the case on vehicles without a locking differential. - With a locking differential, remove the shaft (B) part way, and rotate the case until the pinion shaft touches the housing. - Use a screwdriver or similar tool to enter the case and rotate the lock until it aligns with the thrust block. 6. Lock. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive Axles, Bearings and Joints > Axle Shaft Assembly > Component Information > Service and Repair > Rockwell Full Floating Axle > Page 8417 - Push the flange of the axle shaft towards the differential. Do not force or hammer the shaft to move the axle shaft. - Remove the lock from the button end of the axle shaft. 7. Axle shaft. - Slide the axle shaft out, being careful not to damage the seal. 8. Seal using J 23689. 9. Bearing. A. Use J 23689 for 8 1/2 and 8 5/8 inch ring gear axles or J 29712 for 9 1/2 inch ring gear to pull the bearing from the axle. B. Insert the tool into the axle bore so that it grasps behind the bearing. Tighten the nut and washer against the face of the bearing. Pull the bearing out using J 2619-01. Inspect - All parts. Replace as necessary. INSTALL OR CONNECT NOTICE: Always use the correct fastener in the proper location. When you replace a fastener, use ONLY the exact part number for that application. The manufacturer will call out those fasteners that require a replacement after removal. The manufacturer will also call out the fasteners that require thread lockers or thread sealant. UNLESS OTHERWISE SPECIFIED, do not use supplemental coatings (paints, greases, or other corrosion inhibitors on threaded fasteners or fastener joint interfaces. Generally, such coatings adversely affect the fastener torque and joint clamping force, and may damage the fastener. When you Install fasteners, use the correct tightening sequence and specifications. Following these instructions can help you avoid damage to parts and systems. - Lubricate the axle cavity between the seal lips and the bearing with wheel bearing lubricant. 1. Bearing. - Use J 23690 for the 8 1/2 and 8 5/8 inch gear axle and J 29709 for the 9 1/2 inch ring gear axle. 2. Seal. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive Axles, Bearings and Joints > Axle Shaft Assembly > Component Information > Service and Repair > Rockwell Full Floating Axle > Page 8418 - Bearing into the axle housing until the tool bottoms against the tube. - Use J 21128 for 8 1/2 and 8 5/8 inch ring gear axle and J 29713 for the 9 1/2 inch ring gear axle. - Drive the tool into the bore until the seal bottoms flush with the end of the tube. 3. Axle shaft. - Be careful not to damage the seal when inserting the axle shaft. - Slide the axle shaft into place allowing the splines to engage the differential side gear (F). 4. Lock. - Without locking differential: A. Place the lock on the button end of the axle shaft, then pull the shaft flange outward to seat the lock in the differential side gear. - With locking differential: A. Keep the pinion shaft partially withdrawn. B. Place the lock in the position shown. Pull the shaft flange outward to seat the lock in the differential side gear. 5. Pinion shaft. - Align the hole in the pinion shaft with the screw hole in the differential case. Important: Anytime a differential pinion shaft locking screw is removed, it is important to coat the screw threads with Loctite 242 before reinstalling. These screws are coated with an adhesive which helps to prevent the screw from loosening in the case. When this screw is removed, the adhesive is also removed. 6. Screw (A). - Tighten screw to 34/36 Nm (25/27 ft. lbs.). 7. Carrier cover gasket or RTV (if used). 8. Carrier cover. 9. Bolts and clip. - Bolts in a crosswise pattern to 27/41 Nm (20/30 ft. lbs.). 10. Brake drum. 11. Wheel and tire assembly. - Lower the vehicle. 12. Axle lubricant. Fill to the filler plug hole level. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive Axles, Bearings and Joints > Wheel Bearing > Component Information > Adjustments > Front Wheel Bearing: Adjustments Front FRONT WHEEL BEARINGS ADJUSTMENT Fig. 5 Hub, knuckle & bearing components. REMOVE 1. Raise and support vehicle. 2. Remove wheel cover, if equipped. 3. Remove cap from hub/disc assembly. 4. Remove cotter pin. 5. Tighten nut (12), Fig. 5, to 12 ft lbs, while turning wheel forward by hand. This will seat the bearing. 6. Loosen nut (12) to a just loose position, then back nut off until hole in the spindle aligns with a slot in the nut. Do not back the nut off more than 1/2 flat. INSTALL 1. New cotter pin. With wheel bearing properly adjusted, there will be .001---.005 inch endplay. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive Axles, Bearings and Joints > Wheel Bearing > Component Information > Adjustments > Front > Page 8423 Wheel Bearing: Adjustments Rear Dana/Spicer Full Floating Axle REAR WHEEL BEARINGS ADJUSTMENT Ensure the brakes are completely released and do not drag. Check wheel bearing play by grasping the tire at the top and pulling and pushing back and forth, or by using a pry bar under the tire. If the wheel bearings are properly adjusted, movement of the brake drum in relation to the brake flange plate will be barely noticeable and the wheel will turn freely. If the movement is excessive, adjust the bearings as follows: 1. Back off attaching nut until just loose, but not more than one slot of the lock or the axle spindle using wheel bearing nut wrench tool No. J-2222-C or equivalent. 2. Align adjusting nut slot with keyway in the axle spindle. Rockwell Full Floating Axle REAR WHEEL BEARINGS ADJUSTMENT Ensure the brakes are completely released and do not drag. Check wheel bearing play by grasping the tire at the top and pulling and pushing back and forth, or by using a pry bar under the tire. If the wheel bearings are properly adjusted, movement of hub or disc will be barely noticeable. If the movement is excessive, adjust the bearings as follows: 1. Raise and support vehicle. 2. Remove axle shaft. 3. Remove retaining nut and lock washer. 4. Using nut wrench tool No. J-25510, or equivalent, torque adjusting nut, with hub rotating, to 50.0 ft. lbs. Ensure bearing surfaces are in contact, then back adjusting nut off 1/8 turn. 5. Install lock washer, the bend tang over flat of adjusting nut. 6. Install retaining nut and torque to 250 ft. lbs. 7. Install axle shaft. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive Axles, Bearings and Joints > Wheel Bearing > Component Information > Service and Repair > Front Wheel Bearing: Service and Repair Front FRONT WHEEL BEARINGS AND/OR HUB Fig. 5 Hub, knuckle & bearing components. REMOVE 1. Disconnect battery ground cable. 2. Raise and support vehicle, then remove brake caliper. 3. Remove cap from hub/disc assembly, Fig. 5. 4. Remove cotter pin, nut and washer. 5. Remove hub/disc from spindle. 6. Remove outer bearing, seal, inner bearing and cup. INSTALL 1. Reverse procedure to install. Note the following: a. Clean all components before installing. b. Apply an approved high temperature front wheel bearing grease to the spindle at the inner and outer bearing seat, shoulder and seal seat. Also finger apply a small amount of grease inboard of each bearing cup in the hub/disc assembly. Pressure pack the bearings with a grease machine or hand pack them. Ensure grease is worked thoroughly into the rollers, cone and cage. c. When installing inner bearing, apply an additional quantity of grease outboard of the inner bearing. d. Torque nut (12) 10-12 ft lbs while turning the wheel assembly forward by hand. Apply grease to the outboard side of the outer bearing. Adjust wheel bearings. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive Axles, Bearings and Joints > Wheel Bearing > Component Information > Service and Repair > Front > Page 8426 Wheel Bearing: Service and Repair Rear REAR WHEEL BEARINGS 1. Raise and support vehicle. 2. Remove axle shaft. 3. Remove hub and drum. 4. Remove oil seal, inner bearing and retaining ring. 5. Remove outer bearing. 6. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive Axles, Bearings and Joints > Wheel Hub > Component Information > Service and Repair Wheel Hub: Service and Repair FRONT HUB/BEARING Fig. 5 Hub, knuckle & bearing components. REMOVE 1. Disconnect battery ground cable. 2. Raise and support vehicle, then remove brake caliper. 3. Remove cap from hub/disc assembly, Fig. 5. 4. Remove cotter pin, nut and washer. 5. Remove hub/disc from spindle. 6. Remove outer bearing, seal, inner bearing and cup. INSTALL 1. Reverse procedure to install. Note the following: a. Clean all components before installing. b. Apply an approved high temperature front wheel bearing grease to the spindle at the inner and outer bearing seat, shoulder and seal seat. Also finger apply a small amount of grease inboard of each bearing cup in the hub/disc assembly. Pressure pack the bearings with a grease machine or hand pack them. Ensure grease is worked thoroughly into the rollers, cone and cage. c. When installing inner bearing, apply an additional quantity of grease outboard of the inner bearing. d. Torque nut (12) 10-12 ft lbs while turning the wheel assembly forward by hand. Apply grease to the outboard side of the outer bearing. Adjust wheel bearings. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive Axles, Bearings and Joints > Wheel Seal > Component Information > Service and Repair Wheel Seal: Service and Repair Fig. 5 Hub, knuckle & bearing components. REMOVE 1. Disconnect battery ground cable. 2. Raise and support vehicle, then remove brake caliper. 3. Remove cap from hub/disc assembly, Fig. 5. 4. Remove cotter pin, nut and washer. 5. Remove hub/disc from spindle. 6. Remove outer bearing, seal, inner bearing and cup. INSTALL 1. Reverse procedure to install. Note the following: a. Clean all components before installing. b. Apply an approved high temperature front wheel bearing grease to the spindle at the inner and outer bearing seat, shoulder and seal seat. Also finger apply a small amount of grease inboard of each bearing cup in the hub/disc assembly. Pressure pack the bearings with a grease machine or hand pack them. Ensure grease is worked thoroughly into the rollers, cone and cage. c. When installing inner bearing, apply an additional quantity of grease outboard of the inner bearing. d. Torque nut (12) 10-12 ft lbs while turning the wheel assembly forward by hand. Apply grease to the outboard side of the outer bearing. Adjust wheel bearings. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive/Propeller Shafts, Bearings and Joints > Universal Joint, Drive/Propeller Shaft > Component Information > Description and Operation Universal Joint: Description and Operation The cross and roller type universal joint is a cross-shaped spider joint connecting two Y-shaped yokes. When design angles of more than 3-4° are exceeded, joints wear faster than normal. Original equipment joints are lubricated for life and cannot be lubricated on the vehicle. Never clamp propeller shaft tubing in a vice. Always clamp one of the yokes and support shaft horizontally. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive/Propeller Shafts, Bearings and Joints > Universal Joint, Drive/Propeller Shaft > Component Information > Service and Repair > Service Notes Universal Joint: Service and Repair Service Notes Before disassembling any universal joint, examine the assembly carefully and note the position of the grease fitting (if used). Also, be sure to mark the yokes in relation to the propeller shaft for assembly reference. Failure to observe these precautions may produce rough vehicle operation resulting in rapid wear and parts failure, as well as placing an unbalanced load on transmission, engine and rear axle. When universal joints are disassembled for lubrication or inspection, and the old parts are to be reinstalled, special care must be exercised to avoid damage to universal joint spider or cross and bearing cups. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive/Propeller Shafts, Bearings and Joints > Universal Joint, Drive/Propeller Shaft > Component Information > Service and Repair > Service Notes > Page 8439 Universal Joint: Service and Repair Cross & Roller Type Fig. 1 Production Type Universal Joints Which Use Nylon Injection Rings In Place Of Snap Rings Fig. 2 Service Type Universal Joints (Internal Snap Ring Type) Production universal joints cannot be reassembled because there are no bearing retainer grooves in the production bearing caps, Figs. 2 and 3. DISASSEMBLY 1. Mark shaft for assembly reference. 2. Support shaft in a horizontal line with universal joint bearing separator tool No. J 9522-3, equivalent or suitable vice. Fig. 4 External Snap Ring Universal Joint. 3. On models with external snap rings, remove snap rings, Fig. 4. If ring does not snap out of groove, relieve pressure on ring by tapping lightly on bearing cap. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive/Propeller Shafts, Bearings and Joints > Universal Joint, Drive/Propeller Shaft > Component Information > Service and Repair > Service Notes > Page 8440 4. On all models, place joint in tool No. J 9522-3 or equivalent with lower yoke ear supported by 1 1/8 inch socket, Fig. 5, then press out cap. If cap is not completely removed, insert spacer tool No. J 9522-5 or equivalent and continue to press, Fig. 6. If using a vice in place of special tool, use 1 1/8 inch socket to receive one cap and 5/8 inch socket to push opposite cap. 5. Rotate joint in tool or vice and press opposite cap out, then remove cross from yoke. 6. Inspect and clean retaining ring grooves. 7. Check cap bores for burrs and imperfections. ASSEMBLY 1. Use finger to coat needle bearings with thin layer of grease. Do not fill cups completely or use excessive amounts. Over lubrication may damage seals. 2. Put one bearing cap part way into one side of yoke, then insert cross into cap, Fig. 7. 3. Press cross and cap into yoke until cap is flush with yoke ear. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Drive/Propeller Shafts, Bearings and Joints > Universal Joint, Drive/Propeller Shaft > Component Information > Service and Repair > Service Notes > Page 8441 4. Press opposite cap into yoke, ensuring trunnion alignment, Fig. 8. 5. Continue to press cap into yoke ear while working cross to ensure free, unbinding movement until retainer groove clears inside of yoke. If binding occurs, stop pressing and check for misaligned bearings. 6. Snap retainers into place, Fig. 9. Yoke can be sprung slightly with firm hammer blow if retainer is difficult to seat, Fig. 10. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Manual Transmission/Transaxle > Fluid - M/T > Component Information > Specifications > Capacity Specifications Fluid - M/T: Capacity Specifications 5 SPEED TRANSMISSION OIL 85 mm & 109 mm ................................................................................................................................ ....................................................................... 3.6 pts. New Venture Gear 4500 ...................................................................................................................... ....................................................................... 8.0 pts. New Venture Gear 3500 ...................................................................................................................... ....................................................................... 4.4 pts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Manual Transmission/Transaxle > Fluid - M/T > Component Information > Specifications > Capacity Specifications > Page 8447 Fluid - M/T: Fluid Type Specifications New Venture Gear 3500 Synchromesh Transmission Fluid P/N 9985648 New Venture Gear 4500 Castrol Syntorq LT Transmission Fluid. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Relays and Modules - Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > Customer Interest for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder Control Module: Customer Interest A/T - Upshift Flare/No 3rd or 4th/Launch Shudder File In Section: 07 - Transmission/Transaxle Bulletin No.: 00-07-30-026 Date: December 2000 TECHNICAL Subject: Automatic Transmission 1-2 and/or 2-3 Upshift Slip/Flare, No 3rd or 4th gear, Launch Shudder (Revise VCM Wiring) Models: 1996 Chevrolet and GMC C/K, S/T, M/L, G1, G2, P3 Models 1996 Oldsmobile Bravada with VCM and 4L60-E (M30) or 4L80-E (MT1) Automatic Transmission This bulletin is being reissued to ensure that correct procedures are followed for this condition. Please discard Corporate Bulletin Number 66-71-03A (Section 7 - Automatic Transmission). When performing a transmission replacement labor operation K7000 on these vehicles with a 4L60-E or 4L80-E, you must include front chassis wire repair labor operation N6112. Inspect the VCM to verify the latest part number revision (16244210). Condition Some owners may comment that the automatic transmission has either a slip or flare on the 1-2 and/or 2-3 upshift, or no 3rd or 4th gear, or launch shudder. Upon investigation, the technician may find a DTC P1870 stored in the VCM. Cause A poor internal ground between the two circuit boards of the VCM may cause the VCM to command erratic line pressure at the pressure control (PC) solenoid valve. Correction Using harness jumper wire and instruction kit, P/N 12167310, revise the wiring harness at the VCM connector. Corrections were made to the VCM beginning 2/14/96. The corrected VCMs are identified with service number 16244210 on the VCM identification label. Procedure The following is a summary of the instructions included with the service kit: 1. Remove the negative terminal from the battery. 2. Move the wire located at connector J3 (WHITE/GREY/CLEAR), pin 18 to connector J1 (BLUE), pin 23. 3. Install the jumper wire between connector J2 (RED), pin 26 and connector J3 (WHITE/GREY/CLEAR), pin 18. 4. Install the tag included in the kit around the. VCM wiring harness. This tag notes that the wiring harness has been modified. 5. Reconnect the negative battery terminal. Road test to verify that the condition has been corrected. If any of the following conditions are noted, the transmission should be repaired or replaced using the most cost effective method. Canadian dealers should repair the transmission. ^ Transmission fluid oxidation or excessive sediment. ^ Transmission slip or flare after this service fix is performed. ^ DTC P1870 is stored on a 4L60-E (M30). The following tools are available from Kent-Moore (1-800-345-2233) for use in removing and relocating the VCM wires: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Relays and Modules - Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > Customer Interest for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder > Page 8458 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Relays and Modules - Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder Control Module: All Technical Service Bulletins A/T - Upshift Flare/No 3rd or 4th/Launch Shudder File In Section: 07 - Transmission/Transaxle Bulletin No.: 00-07-30-026 Date: December 2000 TECHNICAL Subject: Automatic Transmission 1-2 and/or 2-3 Upshift Slip/Flare, No 3rd or 4th gear, Launch Shudder (Revise VCM Wiring) Models: 1996 Chevrolet and GMC C/K, S/T, M/L, G1, G2, P3 Models 1996 Oldsmobile Bravada with VCM and 4L60-E (M30) or 4L80-E (MT1) Automatic Transmission This bulletin is being reissued to ensure that correct procedures are followed for this condition. Please discard Corporate Bulletin Number 66-71-03A (Section 7 - Automatic Transmission). When performing a transmission replacement labor operation K7000 on these vehicles with a 4L60-E or 4L80-E, you must include front chassis wire repair labor operation N6112. Inspect the VCM to verify the latest part number revision (16244210). Condition Some owners may comment that the automatic transmission has either a slip or flare on the 1-2 and/or 2-3 upshift, or no 3rd or 4th gear, or launch shudder. Upon investigation, the technician may find a DTC P1870 stored in the VCM. Cause A poor internal ground between the two circuit boards of the VCM may cause the VCM to command erratic line pressure at the pressure control (PC) solenoid valve. Correction Using harness jumper wire and instruction kit, P/N 12167310, revise the wiring harness at the VCM connector. Corrections were made to the VCM beginning 2/14/96. The corrected VCMs are identified with service number 16244210 on the VCM identification label. Procedure The following is a summary of the instructions included with the service kit: 1. Remove the negative terminal from the battery. 2. Move the wire located at connector J3 (WHITE/GREY/CLEAR), pin 18 to connector J1 (BLUE), pin 23. 3. Install the jumper wire between connector J2 (RED), pin 26 and connector J3 (WHITE/GREY/CLEAR), pin 18. 4. Install the tag included in the kit around the. VCM wiring harness. This tag notes that the wiring harness has been modified. 5. Reconnect the negative battery terminal. Road test to verify that the condition has been corrected. If any of the following conditions are noted, the transmission should be repaired or replaced using the most cost effective method. Canadian dealers should repair the transmission. ^ Transmission fluid oxidation or excessive sediment. ^ Transmission slip or flare after this service fix is performed. ^ DTC P1870 is stored on a 4L60-E (M30). The following tools are available from Kent-Moore (1-800-345-2233) for use in removing and relocating the VCM wires: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Relays and Modules - Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder > Page 8464 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Technical Service Bulletins > A/T - Park/Neutral Switch Connector Cannot Be Removed Transmission Position Switch/Sensor: Technical Service Bulletins A/T - Park/Neutral Switch Connector Cannot Be Removed File In Section: 7 - Transmission Bulletin No.: 83-71-10 Date: May, 1998 Subject: Park (Neutral Position Switch Connector Cannot be Removed (Replace Switch and Connectors) Models: 1997-98 Chevrolet Corvette 1995-98 Chevrolet and GMC S/T Models 1996-98 Chevrolet and GMC M/L, P Models 1996-99 Chevrolet and GMC C/K, G Models 1996-98 Oldsmobile Bravada Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer conditions, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to insure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to insure water-tight connections. Parts Information P/N Description 12450016 Switch 15305925 4-Way Connector Assembly 15305887 7-Way Connector Assembly Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 8473 Transmission Position Switch/Sensor: Locations Park/Neutral Position Switch Electronic 4-Speed Automatic Overdrive Transmission Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 8474 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions Transmission Position Switch/Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8477 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8478 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8479 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8480 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8481 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8482 Transmission Position Switch/Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8483 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8484 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8485 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8486 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8487 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8488 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8489 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8490 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8491 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8492 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8493 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8494 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8495 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8496 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8497 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8498 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8499 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8500 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8501 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8502 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8503 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8504 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8505 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8506 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8507 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8508 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8509 Transmission Position Switch/Sensor: Connector Views C1: Transmission Range Switch C2: Transmission Range Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8510 Transmission Position Switch/Sensor: Electrical Diagrams Electronic PRNDL Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8511 Starter And Charging (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 8512 Transmission Position Switch/Sensor: Testing and Inspection Pressure Switch Assembly Resistance Check (1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 8513 Pressure Switch Assembly Resistance Check (2 Of 2) Tools Required - J 39775 4L60E Jumper Harness - J 39200 Digital Multimeter - J 35616 Connector Test Adapter Kit Important: Whenever the transmission 20-way connector is disconnected and the engine is running, multiple DTCs will set. Be sure to clear these codes when you are finished with this procedure Important: This procedure tests the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) circuits and the Automatic Transmission Fluid Temperature (TFT) Sensor circuit. Do not use this procedure to test other Automatic Transmission circuits, refer to 4L60-E Automatic Transmission Internal Wiring Harness check. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 8514 Transmission Position Switch/Sensor: Adjustments PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 8515 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 8516 Transmission Position Switch/Sensor: Service and Repair PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 8517 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Speed Sensor, A/T > Component Information > Locations > Transmission Output Speed Sensor, 4L80E Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Sensors and Switches - Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Speed Sensor, A/T > Component Information > Locations > Transmission Output Speed Sensor, 4L80E > Page 8522 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Interlock Solenoid > Component Information > Locations Shift Interlock Solenoid: Locations RH side of steering column, under Support bracket. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling Shift Solenoid: Customer Interest A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling File In Section: 7 Transmission Bulletin No.: 77-71-77 Date: December, 1997 Subject: Loss of 4th Gear, Slipping in 4th Gear, Busy 3-4 Shifting or TCC Cycling (Replace Shift Solenoids) Models: 1996-97 Chevrolet and GMC C/K, G, P Models with HYDRA-MATIC 4L8OE Transmission (RPO MT1) Condition Some owners may comment about a loss of 4th gear, slipping in 4th gear, busy 3-4 shifting or Torque Converter Clutch (TCC) cycling and no DTC's are setting. Cause Shift solenoid leaking hydraulically. Correction If normal diagnosis does not provide a correction, follow the solenoid test procedure listed. Replace the shift solenoid if it fails the test. Also verify that the transmission cooling system is operating properly. Service Information (figure 1) Starting June 23, 1997 (Julian date 174) all HYDRA-MATIC 4L80-E transmissions are being built with the new solenoid assemblies. The new solenoids will service all 1991 through 1997 4L80-E applications. The above listed conditions occur mainly on high duty cycle applications and/or when the transmission is operated under high temperature conditions. Each solenoid may be tested for leaking using the following test: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling > Page 8537 1. Remove the solenoid from the control valve body. Refer to the Service Manual for the proper procedure. 2. Clamp a piece of 1/2 inch I.D. rubber hose over the fluid inlet end of the solenoid. 3. Connect a wire from one of the solenoid terminals to the negative terminal (ground) of a battery. 4. Apply compressed air to the rubber hose. Do not use air pressure in excess of 120 psi. Excessive pressure will not allow the check ball to seat properly. 5. Connect a wire from the other solenoid to the positive terminal (12 volts) of the battery. 6. Observe the air flow through the solenoid. Replace the solenoid if there is an air leak when the solenoid is energized. Parts Information New Part Number Description 10478140 1-2 & 3-4 Shift Solenoid (black) 10478141 2-3 Shift Solenoid (white) Parts are currently available through GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift Shift Solenoid: Customer Interest A/T - Engine Speed Flare During Part Throttle Downshift File In Section: 7 - Transmission Bulletin No.: 67-71-47 Date: July, 1996 Subject: 3-2 Part Throttle Downshift Flare (Replace 3-2 Solenoid) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1996 Chevrolet Camaro, Caprice, Corvette 1996 Pontiac Firebird 1996 Chevrolet and GMC C/K, M/L, S/T, G Models 1996 Oldsmobile Bravada with HYDRA-MATIC 4L60-E (RPO M30) Condition (Figures 1 and 2) Some owners of the above models with a HYDRA-MATIC 4L60-E transmission (built before May 24, 1996/Julian Date 6145) may experience an engine speed flare of 1000-2000 RPM, during a part throttle downshift at 19-31 mph. This condition will not set any DTC's (Diagnostic Trouble Codes). Cause Exhaust seat on the 3-2 control solenoid backing out. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift > Page 8542 Correction (Figure 3) Replace the 3-2 control solenoid. Julian Date on the solenoid will be May 13, 1996 (6134) or later. Parts Information New Part Number Description 24209121 Solenoid, 3-2 Control Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time K6559 Replace 3-2 Use published labor Control Solenoid operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling Shift Solenoid: All Technical Service Bulletins A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling File In Section: 7 Transmission Bulletin No.: 77-71-77 Date: December, 1997 Subject: Loss of 4th Gear, Slipping in 4th Gear, Busy 3-4 Shifting or TCC Cycling (Replace Shift Solenoids) Models: 1996-97 Chevrolet and GMC C/K, G, P Models with HYDRA-MATIC 4L8OE Transmission (RPO MT1) Condition Some owners may comment about a loss of 4th gear, slipping in 4th gear, busy 3-4 shifting or Torque Converter Clutch (TCC) cycling and no DTC's are setting. Cause Shift solenoid leaking hydraulically. Correction If normal diagnosis does not provide a correction, follow the solenoid test procedure listed. Replace the shift solenoid if it fails the test. Also verify that the transmission cooling system is operating properly. Service Information (figure 1) Starting June 23, 1997 (Julian date 174) all HYDRA-MATIC 4L80-E transmissions are being built with the new solenoid assemblies. The new solenoids will service all 1991 through 1997 4L80-E applications. The above listed conditions occur mainly on high duty cycle applications and/or when the transmission is operated under high temperature conditions. Each solenoid may be tested for leaking using the following test: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 77-71-77 > Dec > 97 > A/T - Loss of 4th Gear/Busy 3-4 Shifting/TCC Cycling > Page 8548 1. Remove the solenoid from the control valve body. Refer to the Service Manual for the proper procedure. 2. Clamp a piece of 1/2 inch I.D. rubber hose over the fluid inlet end of the solenoid. 3. Connect a wire from one of the solenoid terminals to the negative terminal (ground) of a battery. 4. Apply compressed air to the rubber hose. Do not use air pressure in excess of 120 psi. Excessive pressure will not allow the check ball to seat properly. 5. Connect a wire from the other solenoid to the positive terminal (12 volts) of the battery. 6. Observe the air flow through the solenoid. Replace the solenoid if there is an air leak when the solenoid is energized. Parts Information New Part Number Description 10478140 1-2 & 3-4 Shift Solenoid (black) 10478141 2-3 Shift Solenoid (white) Parts are currently available through GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 377148A > Nov > 96 > A/T - Shift Solenoid Update Shift Solenoid: All Technical Service Bulletins A/T - Shift Solenoid Update File In Section: 7 Transmission Bulletin No.: 37-71-48A Date: November, 1996 INFORMATION Subject: Transmission Product Updates (New Shift Solenoids) Models: 1991-97 Chevrolet and GMC C/K, P, G Models 1991 Chevrolet and GMC R/V Models with HYDRA-MATIC 4L8O-E Transmission (RPO MT1) This bulletin is being revised to update the part numbers and to include 1995-97 model years. Please discard Corporate Bulletin Number 377148 (Section 7 - Transmission). Service Information Starting August 14, 1996 (Julian date 226) all HYDRA-MATIC 4L80-E transmissions are being built with the new solenoid assemblies. The new solenoids are serviced for all 1991 through 1997 4L80-E applications. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 377148A > Nov > 96 > A/T - Shift Solenoid Update > Page 8553 Parts Information Previous Part New Part Description 10478125 10478132 Valve assembly, 1-2 Shift Solenoid (Black) 10478126 10478133 Valve assembly, 2-3 Shift Solenoid (White) Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift Shift Solenoid: All Technical Service Bulletins A/T - Engine Speed Flare During Part Throttle Downshift File In Section: 7 - Transmission Bulletin No.: 67-71-47 Date: July, 1996 Subject: 3-2 Part Throttle Downshift Flare (Replace 3-2 Solenoid) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1996 Chevrolet Camaro, Caprice, Corvette 1996 Pontiac Firebird 1996 Chevrolet and GMC C/K, M/L, S/T, G Models 1996 Oldsmobile Bravada with HYDRA-MATIC 4L60-E (RPO M30) Condition (Figures 1 and 2) Some owners of the above models with a HYDRA-MATIC 4L60-E transmission (built before May 24, 1996/Julian Date 6145) may experience an engine speed flare of 1000-2000 RPM, during a part throttle downshift at 19-31 mph. This condition will not set any DTC's (Diagnostic Trouble Codes). Cause Exhaust seat on the 3-2 control solenoid backing out. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 677147 > Jul > 96 > A/T - Engine Speed Flare During Part Throttle Downshift > Page 8558 Correction (Figure 3) Replace the 3-2 control solenoid. Julian Date on the solenoid will be May 13, 1996 (6134) or later. Parts Information New Part Number Description 24209121 Solenoid, 3-2 Control Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time K6559 Replace 3-2 Use published labor Control Solenoid operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Shift Solenoid: > 09-09-40-001A > Feb > 11 > Restraints - Seat Belt Warning Lamp On/Buckling Issues Seat Belt Buckle: All Technical Service Bulletins Restraints - Seat Belt Warning Lamp On/Buckling Issues INFORMATION Bulletin No.: 09-09-40-001A Date: February 02, 2011 Subject: Seat Belt Buckle Latching Issues and/or Seat Belt Warning Lights Illuminated Models: 2011 and Prior GM Passenger Cars and Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7 X Supercede: This bulletin is being revised to add the 2011 model year. Please discard Corporate Bulletin Number 09-09-40-001 (Section 09 - Restraints). This bulletin is being published to advise dealers about seat belt buckles not operating and/or seat belt warning light illumination, as well as difficulty latching and unlatching the buckle or the buckle release button sticking. Analysis of warranty data has determined that this condition may be caused by sticky beverages being spilled onto or into the seat belt buckle assembly. Foreign debris from food, candy wrappers, paper and coins can also contribute to this condition. Important If foreign material (debris) or sticky liquids are the cause of the concern, show the customer the condition of the component (buckle assembly) and explain how it is affecting the function of the restraint system. Strongly recommend that the component be replaced. Point out the fact that this is not a manufacturing defect and is not covered by the new vehicle warranty. If the customer declines to have parts replaced, the service department management must make a notation on the service record that the lack of functionality of seating position with an inoperative buckle was fully explained to the customer. The service department management must advise the customer that having a non-functioning buckle in a seating position voids ability to use that seating position (no one should ride in the seat). Also make the customer aware that it may be against the law to ride in a vehicle without wearing a restraint system. Important Never insert anything other than the seat belt latch plate into the buckle assembly. Do not attempt to dig anything out of a buckle with a tool. Never try to wash out a buckle to remove a spilled liquid as this may damage the buckle. Use the following steps to determine the cause of the concern. 1. Inspect the buckle assembly with a light shining on the latch plate insertion area. Look for any debris or foreign objects in the buckle. 2. If any debris or foreign objects are observed, try to vacuum out the item. After the foreign material is removed, latch and unlatch the seat belt. If the system functions properly, do not replace the seat belt buckle assembly. 3. If the condition has not been corrected, inspect the buckle assembly for any sticky residue. If sticky residue is found, inform the customer that a substance was spilled on the seat belt buckle assembly causing the malfunction. The buckle assembly will need to be replaced at the customer's expense. 4. Refer to SI for seat belt component replacement. Important If foreign material (debris) or sticky liquids are the cause of the concern, show the customer the condition of the component (buckle assembly) and explain how it is affecting the function of the restraint system. Strongly recommend that the component be replaced at the customer's expense. Point out the fact that this is not a manufacturing defect and is not covered by the new vehicle warranty. If the customer declines to have parts replaced, the service department management must make a notation on the service record that the lack of functionality of seating position with an inoperative buckle was fully explained to the customer. The service department management must advise customer that having a non-functioning buckle in a seating position voids ability to use that seating position (no one should ride in the seat). Also make the customer aware that it may be against the law to ride in a vehicle without wearing a restraint system. 5. If further restraint diagnosis is required, refer to Seat Belt System Operational and Functional Checks in SI. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Shift Solenoid: > 09-09-40-001A > Feb > 11 > Restraints - Seat Belt Warning Lamp On/Buckling Issues > Page 8564 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Technical Service Bulletins > All Other Service Bulletins for Shift Solenoid: > 09-09-40-001A > Feb > 11 > Restraints - Seat Belt Warning Lamp On/Buckling Issues > Page 8570 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Specifications > 4L60-E Automatic Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Specifications > 4L60-E Automatic Transmission > Page 8573 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Locations > 4L60-E Automatic Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Locations > 4L60-E Automatic Transmission > Page 8576 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission Shift Solenoid: Service and Repair 4L60-E Automatic Transmission Pan and Filter Assembly PAN AND FILTER ASSEMBLY Pan, Filter And Seal Removal CLEAN - Exposed ends of bottom pan screws and spray with penetrating oil. REMOVE OR DISCONNECT 1. Screws (76), oil pan (75) and gasket (73). 2. Oil filter (72) and filter seal (71). - Filter seal may be stuck in the pump. INSPECT - Filter (72), open filter by prying the metal crimping away from the top of the filter (black) and pull apart. The filter may contain evidence for root cause diagnosis. Clutch material. - Bronze slivers indicating bushing wear. - Steel particles. Valve Body and Wiring Harness VALVE BODY AND WIRING HARNESS Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8579 Valve Body Bolt Location Control Valve And Pressure Switch Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8580 Manual Valve Link Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8581 Valve Body Checkballs Case Checkballs And Filters REMOVE OR DISCONNECT 1. Electrical connections from components. 2. TCC PWM Solenoid Retainer Clip (379) and Solenoid (396). 3. TCC Solenoid bolts (68) and solenoid assembly (66) with O-ring seal (65) and wiring harness. 4. Pressure switch assembly bolts (70) and pressure switch assembly (69). 5. Accumulator cover bolts (58 and 59) and 1-2 accumulator cover and pin assembly (57). 6. 1-2 accumulator piston (56) and seal (55). 7. Spring (54). 8. Dipstick stop bracket (93). REMOVE OR DISCONNECT 1. Bolt (64) and manual detent spring assembly (63). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8582 2. Wiring harness retaining bolts. REMOVE OR DISCONNECT 1. Remaining valve body bolts (62). 2. Manual valve link (89). 3. Control valve assembly (60). 4. Bolts (58 and 59), accumulator cover (57), piston (56, spring (54) and spring (54A). 5. Bolts (77) and plate (53). 6. Spacer plate (48) and spacer plate gaskets (47 and 52). 7. Spring (46), piston (44), and pin (43). - Seven checkballs are located under the valve body and one is located in the case. The large copper flash colored ball is # 1A checkball (91). Valve Body and Associated Parts VALVE BODY AND ASSOCIATED PARTS Accumulator Assembly, Spacer Plate And Gaskets Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8583 Case Checkballs And Filters TOOL REQUIRED: - J 25025-5 Guide Pins NOTICE: The use of a honing stone, fine sandpaper or crocus cloth is not recommended for servicing stuck valves. All valve lands have sharply machined corners that are necessary for "cleaning" the bore. If these corners are rounded, foreign material could wedge between the valve and bore causing the valve to stick. If it is found necessary to clean a valve, "micro fine" lapping compound 900 grit or finer should be used. Too much "lapping" of a valve will cause excessive clearances and increase the chance of a valve not operating. INSTALL OR CONNECT 1. The wiring harness pass-thru connector into the case. 2. The 3-4 accumulator pin (43) into the case. 3. The 3-4 accumulator piston seal (45) onto the 3-4 accumulator piston. 4. The 3-4 accumulator piston (44) onto the pin. - The end with three legs must face the valve body. 5. The 3-4 accumulator piston spring (46). INSTALL OR CONNECT 1. Checkball (91) into case as shown. - Retain with Transjel TM J 36850 or equivalent. 2. J 25025-5 into the case. 3. Screens onto spacer plate as shown. 4. Spacer plate to case gasket (47) and spacer plate to valve body gasket (52) onto the spacer plate (48). - Gasket (47) identified by a "C". Gasket (52) identified by a "V". - Retain with Transjel TM J 36850 or equivalent. 5. Spacer plate and gaskets onto the case. IMPORTANT - Be careful not to damage screens when installing the spacer plate and gaskets. 6. Spacer plate support (53) and bolts (77). TIGHTEN - Bolts to 11 Nm (8 lb. ft.) Control Valve Body CONTROL VALVE BODY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8584 Case Checkballs And Filters Filter Screen - Locations Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8585 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8586 Control Valve Assembly - Legend Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8587 Valve Body Checkball Locations Valve Body Bolt Locations Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8588 Manual Valve Link Outside Electrical Connector CLEAN - Control valve assembly thoroughly in clean solvent. A. Move the valves with a pick or small screwdriver to dislodge any dirt or debris that may have accumulated. B. Air dry. REMOVE OR DISCONNECT IMPORTANT - Some valves are under pressure - cover the bores while removing roll pins and retainer clips. - Valves, springs and bushings must be laid out on a clean surface in the exact sequence they are removed. 1. Pressure control solenoid retainer bolt (364) retainer (378) and solenoid. 2. Bore plug retainer clip (395), bore plug (376) and valve train (374 and 375). 3. 2-3 shift solenoid retainer (379), solenoid (367) and valve train (368 and 369). 4. 1-2 shift solenoid retainer (379), solenoid (367) and valve train (365 and 366). 5. Accumulator valve train retainer pin (360), bore plug (373) and valve train (370 and 371). 6. Forward accumulator cover bolts (364) and cover (363). 7. Forward accumulator spring (356), piston (354) and pin (355). 8. Lo overrun valve spring (362) and valve (361). 9. Retainer pin (360), bore plug (359) and forward abuse valve train (357 and 358). 10. Manual valve (340). 11. 3-2 control solenoid retainer clip (379) and solenoid (394). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8589 12. Bore plug retainer (395), bore plug (381) and 3-2 control valve train (391 - 393). 13. 3-2 downshift bore plug retainer (395), bore plug (381) and valve train (389 - 390). 14. Reverse abuse bore plug retainer pin (360), bore plug (359) and valve train (387 - 388). 15. 3-4 shift valve bore plug retainer (395), bore plug (381) and valve train (385 - 386). 16. 3-4 relay bore plug retainer (395), bore plug (381) and valve train (382 - 384). 17. Torque converter clutch signal valve bore plug retainer (395), bore plug (381) and valve (380). CLEAN - All valves, springs, bushings and control valve body in clean solvent. - Dry using compressed air. INSPECT - All valves and bushings for: Porosity - Scoring - Nicks - Scratches - Springs for damaged or distorted coils. - Valve body casting for: Porosity - Cracks - Inter connected oil passages - Damaged machined surfaces ASSEMBLE - Control valve assembly (350) exactly as shown. Notice the position of the valve lands and bushing passages. - Position the pressure control solenoid so the connector tabs face outward. NOTICE: TCC PWM solenoid (396) cannot be installed until TCC solenoid has been installed and torqued to proper specifications. INSTALL OR CONNECT 1. Checkballs into the valve body assembly (350). - Retain with Transjell TM J 36850 or equivalent. 2. Valve body assembly (350). - Connect the manual valve link (89) to the inside detent lever (88). - Be careful not to damage screens when installing the valve body assembly. 3. Wiring harness (66), manual spring assembly (63), pressure switch assembly(69), dipstick, stop bracket (93) and all remaining valve body bolts. NOTICE: Torque valve body bolts in a spiral pattern starting from the center. If bolts are torqued at random, valve bores may be distorted and inhibit valve operation. 4. TCC solenoid (66) and bolts (68). TIGHTEN - Bolts to 11 Nm (8 lb. ft.). 5. TCC PWM solenoid (396), and retainer clip (379). INSTALL OR CONNECT - Wiring harness connections to electrical components. - To correctly hook up the wires, see the wiring diagrams. - The pressure control solenoid (377) has two different colored connectors. The black connector should be installed on the tab farthest from the valve body. INSTALL OR CONNECT 1. Parking bracket (86). TIGHTEN - Bolts to 31 Nm (23 lb. ft.). 2. The 1-2 accumulator piston seal (55) onto the 1-2 accumulator piston (56). 3. The 1-2 accumulator spring (54) and 1-2 accumulator inner spring (54A) onto the piston (56). 4. The 1-2 accumulator piston (56) into the 1-2 accumulator cover and pin assembly (57). - The three legs on the piston must face away from the case when installed. 5. The 1-2 accumulator cover and pin assembly (57) onto the case. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8590 TIGHTEN - Torque to 11 Nm (8 lb. ft.). Pan and Filter Assembly PAN AND FILTER ASSEMBLY Case, Pan And Filter Assembly INSTALL OR CONNECT 1. Filter seal (71) into the pump. 2. Oil filter (72). 3. Oil pan gasket (73). 4. Chip magnet (74) onto oil pan (75). 5. Oil pan (75) and bolts (76). TIGHTEN - Torque to 12 Nm (9 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8591 Shift Solenoid: Service and Repair 4L80-E Automatic Transmission Pan and Filter Assembly PAN AND FILTER ASSEMBLY Pan, Filter And Seal Removal REMOVE OR DISCONNECT 1. Drain the transmission fluid Out case extension by rotating transmission to a vertical position. 2. Seventeen bolts (27), using 10 mm socket, drain transmission fluid. 3. Pan (28), seal (29) and magnet (30). IMPORTANT - Seal (29) is reusable. 4. Filter assembly (31). INSPECT - Filter neck seal (32), replace if necessary. Wire Harness Assembly WIRE HARNESS ASSEMBLY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8592 Pan, Filter And Seal Removal REMOVE OR DISCONNECT 1. Wire harness connectors from electrical components. NOTICE: Excessive force on the case pass through connector may damage the connector. IMPORTANT - If the wire harness assembly does not need servicing, it is not necessary to remove it from the case. 2. Wire harness assembly (34) from case using a 1-5/16" 12 point socket to release the connector retaining clips. Control Valve Assembly CONTROL VALVE ASSEMBLY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8593 REMOVE OR DISCONNECT 1. Rotate transmission bottom pan surface up and lock in place. 2. Wire harness assembly (34) connectors from components. IMPORTANT - If the wire harness assembly does not need servicing, it is not necessary to remove it from the case. - Use a cap to cover electrical pin at case connection. 3. Six bolts (76) using 8 mm socket, and transmission fluid pressure switch assembly (40). NOTICE: Be sure five O-rings are attached to transmission fluid pressure switch assembly. 4. Twenty-one bolts (35) using 10 mm socket, from valve body assembly, manual detent spring and roller assembly (41). 5. Three wiring clamps (33), fluid level indicator stop (43), one bolt (36) using 10 mm socket, lube pipe (39), lube pipe retainer (37) and clamp (38). 6. Control valve assembly (44) including the accumulator housing assembly (51), valve body gaskets (45 and 48), spacer plate (46) and accumulator gasket (47). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8594 7. Manual valve (319) from control valve assembly (44) to prevent any damage. 8. Checkballs (54) from case passages. NOTICE: Do not use a magnet. It could cause checkball(s) to be magnetized causing metal particles to stick to the ball. 9. Pulse Width Modulated (PWM) solenoid screen (75). INSPECT - Screen PWM solenoid (75), replace if necessary. DISASSEMBLE Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8595 - Control valve assembly. A. Position as shown on a clean surface. B. Remove blind hole retainer pins with a drill bit. CAUTION: Some valves are under pressure - cover the bores while removing the retaining pins or personal injury could result. C. Remove valve trains, shift solenoids (311 and 313), PCS (320), PWM solenoid (323), PCS screen (302) and shift solenoid filter (317). D. Valves, springs, bushings and pistons must be laid out on a clean surface. CLEAN - All valves, springs, bushings, pistons, control valve body and accumulator housing in clean solvent. - Dry using compressed air. INSPECT 1. All valves, pistons and bushings for: - Porosity. - Scoring. - Nicks. - Scratches. 2. Pistons for: - Seal damage. 3. Springs for: - Damaged or distorted coils. 4. Valve body casting and accumulator housing for: - Porosity. - Cracks. - Interconnected passages. - Damaged machined surfaces. 5. Solenoid connectors and filter (317). 6. PCS (Pressure Control Solenoid) screen (302). Control Valve Assembly/Accumulator Housing CONTROL VALVE ASSEMBLY/ACCUMULATOR HOUSING Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8596 Control Valve Assembly/Accumulator Housing Accumulator Housing Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8597 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8598 Torque Sequence And Guide Pin Location Fig. 11 Check Ball Location. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8599 Fig. 10 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8600 Torque Sequence, Control Valve And Switch Assembly NOTICE: The use of a honing stone, fine sandpaper or crocus cloth is not recommended for servicing stuck valves. All valve lands have sharply machined comers that are necessary for cleaning the bore. If these corners are rounded, foreign material could wedge between the valve and the bore causing the valve to stick. If it is found necessary to clean a valve, micro fine lapping compound 900 grit (J 38459) or finer should be used. Too much lapping of the valve will cause excessive clearances and increase the chance of a valve not operating. CLEAN - Control valve assembly and accumulator housing (51) thoroughly in clean solvent. - Air dry. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8601 Accumulator Housing Assembly ACCUMULATOR HOUSING ASSEMBLY Control Valve Assembly/Accumulator Housing Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8602 Accumulator Housing Assembly DISASSEMBLE 1. Six bolts (53), using 8 mm socket. 2. Accumulator housing assembly. 3. Gasket accumulator housing (47). 4. Spacer plate (46). 5. Gasket (45) valve body spacer. 6. Snap ring (402) from outside housing, pin (408), snap ring (402), piston (407) and spring (49). 7. 3rd clutch piston (405) and spring (50). 8. Seals (404 and 406). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8603 CLEAN - All components. INSPECT - All valves, pistons, springs and seals for: - Porosity. - Scoring. - Nicks. - Scratches. Accumulator Housing Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8604 ASSEMBLE - Accumulator housing assembly components exactly as shown. Notice the positions of the pistons. Control Valve Assembly CONTROL VALVE ASSEMBLY Control Valve Assembly ASSEMBLE - Control valve assembly components exactly as shown. Notice the position of the valve lands and bushing passages. Control Valve Assembly/Accumulator Housing Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8605 CONTROL VALVE ASSEMBLY AND ACCUMULATOR HOUSING Control Valve Assembly/Accumulator Housing Torque Sequence And Guide Pin Location TOOL REQUIRED: - Guide Pin J 25025-5 ASSEMBLE 1. Guide pin J 25025-5 into valve body. Located at back bolt hole of detent spring and roller assembly bolt bole. 2. Gasket (45) valve body to spacer plate. 3. Spacer plate (46). 4. Gasket (47) accumulator housing to spacer plate. 5. Accumulator housing assembly (51) onto valve body assembly (44). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8606 6. Six bolts (53) using (8 mm) socket through accumulator housing into valve body assembly. Torque Sequence And Guide Pin Location NOTE: Start accumulator housing bolts finger tight and work towards opposite end. TIGHTEN - Bolt (53) to 11 Nm (97 lb. in.). 7. Remove guide pin J 25025-5. Fig. 11 Check Ball Location. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8607 Fig. 10 Control Valve Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8608 Torque Sequence, Control Valve And Switch Assembly INSTALL OR CONNECT 1. Install checkballs (54) in proper location into case fluid passages. Use TRANSJEL TM J 36850 or equivalent to hold in place. NOTICE: Do not use any type of grease to retain parts during assembly of this unit. Greases other than the recommended assembly lube will change transmission fluid characteristics and cause undesirable shift conditions and/or filter clogging. - # 2 checkball is used only on RCP RDP, ZJP and ZLP models. 2. PWM solenoid screen (75). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8609 3. Gasket (48) spacer plate to case. 4. Manual valve (319) into valve body. 5. Complete valve body assembly (44) onto case (7). Use 1 25025-5 guide pin set. IMPORTANT - Attach manual valve to detent lever. 6. Transmission fluid pressure switch assembly (40) onto valve body assembly (44). 7. Spring and roller assembly (41) into place. 8. Three wiring clamps (33), fluid indicator stop (43) and lube pipe clamp (38). 9. Twenty-one bolts (35). Using 10 mm socket. 10. Six bolts (76) using 8 mm socket into transmission fluid pressure switch assembly (40). 11. Lube pipe (39) long end into case, short end into valve body. 12. Lube pipe retainer (37) with short bolt (36). TIGHTEN - Bolts (35, 36 and 76) to 11 Nm (97 lb. in.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8610 Torque Sequence, Control Valve And Switch Assembly NOTICE: Torque valve body bolts in a spiral pattern starting from the center. If bolts are torqued at random, valve bores may be distorted and inhibit valve operation. 13. Attach wiring harness (34) to 5 connectors. - Put large end into case first, pressure switch hook up, 1-2 shift solenoid (purple) and 2-3 shift solenoid (tan), PWM (Pulse Width Modulated) solenoid and PCS (Pressure Control Solenoid). Pan and Filter Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Shift Solenoid, A/T > Component Information > Service and Repair > 4L60-E Automatic Transmission > Page 8611 PAN AND FILTER ASSEMBLY Installing Pan And Filter INSTALL OR CONNECT 1. Seal (32) inside of case (7). 2. Filter assembly (31). 3. Bottom pan seal (29). 4. Magnet (30) into bottom pan. 5. Pan (29). 6. Seventeen bolts (27) using 10 mm socket. TIGHTEN - Bolts (27) to 24 Nm (18 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON Torque Converter Clutch Solenoid: Customer Interest A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-023B Date: March, 2002 TECHNICAL Subject: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1999-2000 Cadillac Escalade 1996-2000 Chevrolet Camaro, Corvette 1996-2000 Pontiac Firebird 1996-2000 Chevrolet and GMC Light Duty Truck Models 1996-2000 Oldsmobile Bravada with 4L60-E Automatic Transmission (RPO M30) Built Prior to January 15, 2000 (Julian Date 0015) This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 Transmission/Transaxle). Condition Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated. Diagnosis Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs. The scan tool may show a DTC P1870 set as a history code. A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93° C (200°F). Cause The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply. Important: ^ DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code. ^ When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result. ^ This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle). ^ When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code. ^ When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL). Correction Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 8620 regulator and isolator valves. Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body. ^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears). ^ The torque converter is not blue or overheated. ^ The transmission fluid is not burned or has no burned odor ^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > Customer Interest for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 8621 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON Torque Converter Clutch Solenoid: All Technical Service Bulletins A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-023B Date: March, 2002 TECHNICAL Subject: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1999-2000 Cadillac Escalade 1996-2000 Chevrolet Camaro, Corvette 1996-2000 Pontiac Firebird 1996-2000 Chevrolet and GMC Light Duty Truck Models 1996-2000 Oldsmobile Bravada with 4L60-E Automatic Transmission (RPO M30) Built Prior to January 15, 2000 (Julian Date 0015) This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 Transmission/Transaxle). Condition Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated. Diagnosis Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs. The scan tool may show a DTC P1870 set as a history code. A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93° C (200°F). Cause The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply. Important: ^ DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code. ^ When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result. ^ This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle). ^ When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code. ^ When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL). Correction Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 8627 regulator and isolator valves. Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body. ^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears). ^ The torque converter is not blue or overheated. ^ The transmission fluid is not burned or has no burned odor ^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Actuators and Solenoids Transmission and Drivetrain > Actuators and Solenoids - A/T > Torque Converter Clutch Solenoid, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Torque Converter Clutch Solenoid: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 8628 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Relays and Modules Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > Customer Interest for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder Control Module: Customer Interest A/T - Upshift Flare/No 3rd or 4th/Launch Shudder File In Section: 07 - Transmission/Transaxle Bulletin No.: 00-07-30-026 Date: December 2000 TECHNICAL Subject: Automatic Transmission 1-2 and/or 2-3 Upshift Slip/Flare, No 3rd or 4th gear, Launch Shudder (Revise VCM Wiring) Models: 1996 Chevrolet and GMC C/K, S/T, M/L, G1, G2, P3 Models 1996 Oldsmobile Bravada with VCM and 4L60-E (M30) or 4L80-E (MT1) Automatic Transmission This bulletin is being reissued to ensure that correct procedures are followed for this condition. Please discard Corporate Bulletin Number 66-71-03A (Section 7 - Automatic Transmission). When performing a transmission replacement labor operation K7000 on these vehicles with a 4L60-E or 4L80-E, you must include front chassis wire repair labor operation N6112. Inspect the VCM to verify the latest part number revision (16244210). Condition Some owners may comment that the automatic transmission has either a slip or flare on the 1-2 and/or 2-3 upshift, or no 3rd or 4th gear, or launch shudder. Upon investigation, the technician may find a DTC P1870 stored in the VCM. Cause A poor internal ground between the two circuit boards of the VCM may cause the VCM to command erratic line pressure at the pressure control (PC) solenoid valve. Correction Using harness jumper wire and instruction kit, P/N 12167310, revise the wiring harness at the VCM connector. Corrections were made to the VCM beginning 2/14/96. The corrected VCMs are identified with service number 16244210 on the VCM identification label. Procedure The following is a summary of the instructions included with the service kit: 1. Remove the negative terminal from the battery. 2. Move the wire located at connector J3 (WHITE/GREY/CLEAR), pin 18 to connector J1 (BLUE), pin 23. 3. Install the jumper wire between connector J2 (RED), pin 26 and connector J3 (WHITE/GREY/CLEAR), pin 18. 4. Install the tag included in the kit around the. VCM wiring harness. This tag notes that the wiring harness has been modified. 5. Reconnect the negative battery terminal. Road test to verify that the condition has been corrected. If any of the following conditions are noted, the transmission should be repaired or replaced using the most cost effective method. Canadian dealers should repair the transmission. ^ Transmission fluid oxidation or excessive sediment. ^ Transmission slip or flare after this service fix is performed. ^ DTC P1870 is stored on a 4L60-E (M30). The following tools are available from Kent-Moore (1-800-345-2233) for use in removing and relocating the VCM wires: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Relays and Modules Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > Customer Interest for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder > Page 8639 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Relays and Modules Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder Control Module: All Technical Service Bulletins A/T - Upshift Flare/No 3rd or 4th/Launch Shudder File In Section: 07 - Transmission/Transaxle Bulletin No.: 00-07-30-026 Date: December 2000 TECHNICAL Subject: Automatic Transmission 1-2 and/or 2-3 Upshift Slip/Flare, No 3rd or 4th gear, Launch Shudder (Revise VCM Wiring) Models: 1996 Chevrolet and GMC C/K, S/T, M/L, G1, G2, P3 Models 1996 Oldsmobile Bravada with VCM and 4L60-E (M30) or 4L80-E (MT1) Automatic Transmission This bulletin is being reissued to ensure that correct procedures are followed for this condition. Please discard Corporate Bulletin Number 66-71-03A (Section 7 - Automatic Transmission). When performing a transmission replacement labor operation K7000 on these vehicles with a 4L60-E or 4L80-E, you must include front chassis wire repair labor operation N6112. Inspect the VCM to verify the latest part number revision (16244210). Condition Some owners may comment that the automatic transmission has either a slip or flare on the 1-2 and/or 2-3 upshift, or no 3rd or 4th gear, or launch shudder. Upon investigation, the technician may find a DTC P1870 stored in the VCM. Cause A poor internal ground between the two circuit boards of the VCM may cause the VCM to command erratic line pressure at the pressure control (PC) solenoid valve. Correction Using harness jumper wire and instruction kit, P/N 12167310, revise the wiring harness at the VCM connector. Corrections were made to the VCM beginning 2/14/96. The corrected VCMs are identified with service number 16244210 on the VCM identification label. Procedure The following is a summary of the instructions included with the service kit: 1. Remove the negative terminal from the battery. 2. Move the wire located at connector J3 (WHITE/GREY/CLEAR), pin 18 to connector J1 (BLUE), pin 23. 3. Install the jumper wire between connector J2 (RED), pin 26 and connector J3 (WHITE/GREY/CLEAR), pin 18. 4. Install the tag included in the kit around the. VCM wiring harness. This tag notes that the wiring harness has been modified. 5. Reconnect the negative battery terminal. Road test to verify that the condition has been corrected. If any of the following conditions are noted, the transmission should be repaired or replaced using the most cost effective method. Canadian dealers should repair the transmission. ^ Transmission fluid oxidation or excessive sediment. ^ Transmission slip or flare after this service fix is performed. ^ DTC P1870 is stored on a 4L60-E (M30). The following tools are available from Kent-Moore (1-800-345-2233) for use in removing and relocating the VCM wires: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Relays and Modules Transmission and Drivetrain > Relays and Modules - A/T > Control Module, A/T > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Control Module: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder > Page 8645 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Technical Service Bulletins > A/T - Park/Neutral Switch Connector Cannot Be Removed Transmission Position Switch/Sensor: Technical Service Bulletins A/T - Park/Neutral Switch Connector Cannot Be Removed File In Section: 7 - Transmission Bulletin No.: 83-71-10 Date: May, 1998 Subject: Park (Neutral Position Switch Connector Cannot be Removed (Replace Switch and Connectors) Models: 1997-98 Chevrolet Corvette 1995-98 Chevrolet and GMC S/T Models 1996-98 Chevrolet and GMC M/L, P Models 1996-99 Chevrolet and GMC C/K, G Models 1996-98 Oldsmobile Bravada Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer conditions, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to insure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to insure water-tight connections. Parts Information P/N Description 12450016 Switch 15305925 4-Way Connector Assembly 15305887 7-Way Connector Assembly Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 8654 Transmission Position Switch/Sensor: Locations Park/Neutral Position Switch Electronic 4-Speed Automatic Overdrive Transmission Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Locations > Park/Neutral Position and Backup Lamp Switch > Page 8655 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions Transmission Position Switch/Sensor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8658 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8659 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8660 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8661 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8662 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8663 Transmission Position Switch/Sensor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8664 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8665 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8666 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8667 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8668 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8669 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8670 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8671 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8672 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8673 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8674 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8675 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8676 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8677 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8678 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8679 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8680 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8681 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8682 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8683 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8684 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8685 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8686 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8687 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8688 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8689 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8690 Transmission Position Switch/Sensor: Connector Views C1: Transmission Range Switch C2: Transmission Range Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8691 Transmission Position Switch/Sensor: Electrical Diagrams Electronic PRNDL Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Diagram Information and Instructions > Page 8692 Starter And Charging (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 8693 Transmission Position Switch/Sensor: Testing and Inspection Pressure Switch Assembly Resistance Check (1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 8694 Pressure Switch Assembly Resistance Check (2 Of 2) Tools Required - J 39775 4L60E Jumper Harness - J 39200 Digital Multimeter - J 35616 Connector Test Adapter Kit Important: Whenever the transmission 20-way connector is disconnected and the engine is running, multiple DTCs will set. Be sure to clear these codes when you are finished with this procedure Important: This procedure tests the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) circuits and the Automatic Transmission Fluid Temperature (TFT) Sensor circuit. Do not use this procedure to test other Automatic Transmission circuits, refer to 4L60-E Automatic Transmission Internal Wiring Harness check. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 8695 Transmission Position Switch/Sensor: Adjustments PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 8696 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 8697 Transmission Position Switch/Sensor: Service and Repair PARK/NEUTRAL POSITION SWITCH REPLACEMENT/ADJUSTMENT - Tool Required: J 41364-A Neutral Position Adjustment Tool - Apply the parking brake. - Shift the transmission into neutral. REMOVE OR DISCONNECT IMPORTANT: The transmission must be positioned into the mechanical neutral position prior to performing this adjustment procedure. The transmission control lever can be positioned to mechanical neutral position by rotating the control lever clockwise until it reaches it's full stop position, and then moving the shift control lever counter-clockwise two detents. 1. Negative battery cable. 2. Shift cable end from the transmission shift control lever by pulling the cable end from the transmission shift control lever stud ball. 3. Nut securing the transmission shift control lever to the manual shaft. 4. Wiring harness connector from the switch. 5. Two bolts securing the switch to the transmission. 6. Switch from the manual shaft. - If the switch does not slide off of the manual shaft, lightly file the outer edge of the manual shaft to remove any burrs from the shaft. INSTALL OF CONNECT ADJUST 1. Position Tool J 41364-A onto the park/neutral position switch. Ensure that the two slots on the switch(where manual shaft is inserted) are lined up with the lower two tabs on the tool. Rotate the tool until the upper locator pin on the tool is lined up with the slot on the top of the switch 2. Switch to the transmission manual shaft. - Before sliding the switch onto shaft, it may be necessary to lightly file the outer edge of the shaft to remove any burrs from the shaft. - Align the switch hub flats with the manual shaft flats. - Slide the switch onto the transmission manual shaft until the switch mounting bracket contacts the mounting bosses on the transmission. 3. Switch to transmission with two bolts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Position Switch/Sensor, A/T > Component Information > Diagrams > Page 8698 TIGHTEN - Bolts securing the switch to 28 Nm (21 lb. ft.). 4. Remove Tool J 41364 from the switch. 5. Wiring harness connectors to the switch. 6. Transmission control lever to the manual shaft. 7. Transmission control lever to the manual shaft with the nut. TIGHTEN - Control lever nut to 28 Nm (21 lb. ft.). 8. Lower vehicle 9. Negative battery cable. INSPECT 1. Check the switch for proper operation. - The engine must start in the "P" (Park) or "N" (Neutral) positions only. If adjustments is required, loosening the switch retaining bolts and rotate the switch slightly, then tighten the bolts and check the switch for proper operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Speed Sensor, A/T > Component Information > Locations > Transmission Output Speed Sensor, 4L80E Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Transmission and Drivetrain > Transmission Control Systems > Sensors and Switches Transmission and Drivetrain > Sensors and Switches - A/T > Transmission Speed Sensor, A/T > Component Information > Locations > Transmission Output Speed Sensor, 4L80E > Page 8703 Electronic 4-Speed Automatic Overdrive Transmission W/4WD Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > ABS Main Relay > Component Information > Locations ABS Main Relay: Locations The relay is located inside the Brake Pressure Modulator Valve (BPMV) and cannot be serviced. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Brake Fluid Pump > Component Information > Technical Service Bulletins > ABS - Revised DTC Tables 67 and 68 Brake Fluid Pump: Technical Service Bulletins ABS - Revised DTC Tables 67 and 68 File In Section: 5 - Brakes 1 Bulletin No.: 66-50-10 Date: August, 1996 SERVICE MANUAL UPDATE Subject: Section 5E1 - Antilock Brake System (ABS) - Revised DTC Tables 67 and 68 Models: 1996 Chevrolet and GMC M/L, C/K, G, S Models with 2.2L Engine (VIN 4 - RPO LN2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Brake Fluid Pump > Component Information > Technical Service Bulletins > ABS - Revised DTC Tables 67 and 68 > Page 8713 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Brake Fluid Pump > Component Information > Technical Service Bulletins > ABS - Revised DTC Tables 67 and 68 > Page 8714 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Brake Fluid Pump > Component Information > Technical Service Bulletins > ABS - Revised DTC Tables 67 and 68 > Page 8715 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Brake Fluid Pump > Component Information > Technical Service Bulletins > ABS - Revised DTC Tables 67 and 68 > Page 8716 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Brake Fluid Pump > Component Information > Technical Service Bulletins > ABS - Revised DTC Tables 67 and 68 > Page 8717 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Brake Fluid Pump > Component Information > Technical Service Bulletins > ABS - Revised DTC Tables 67 and 68 > Page 8718 This bulletin revises Diagnostic Trouble Code tables 67, "Pump Motor Circuit Open" and 68 "Pump Motor Locked or Pump Motor Circuit Shorted" for Section 5E1. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Braking Sensor/Switch > Component Information > Service and Repair Braking Sensor/Switch: Service and Repair Stop Lamp Switch Remove or Disconnect 1. Negative battery cable. 2. Disable SIR. 3. Retainer from brake pedal pin. Use snap ring pliers. 4. Switch by unsnapping from pushrod. 5. Electrical connector from switch. Install or Connect 1. Electrical connector into switch. 2. Switch by snapping it onto pushrod. 3. Retainer onto brake pedal pin. Use 11mm (7/16 inch) socket to push new clip on pin. 4. Negative battery cable. 5. Enable SIR. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Electronic Brake Control Module > Component Information > Locations Electronic Brake Control Module: Locations The Electronic Brake Control Unit (EBCM) is mounted to the top of the Brake Pressure Modulator Valve (BPMV) and is housed in aluminum with a black plastic top. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Electronic Brake Control Module > Component Information > Locations > Page 8725 Electronic Brake Control Module: Service and Repair Fig. 226 EBCM Replacement. 1. Disconnect battery ground cable, then raise and support vehicle. 2. Remove bolts securing shield (if equipped) and BPMV to EHCU mounting bracket, Fig. 226, then disconnect (EBCM) Electronic Brake Control Module electrical connectors. 3. Remove Torx bolts securing EBCM to BPMV, then separate EBCM from BPMV. Do not pry on components to separate. 4. Reverse procedure to install, noting the following: a. Install a new EBCM gasket and mounting bolts. Do not use any gasket sealant. b. Torque EBCM to BPMV bolts to 39 inch lbs. in a crisscross pattern. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Hydraulic Control Assembly - Antilock Brakes > Component Information > Locations Hydraulic Control Assembly - Antilock Brakes: Locations Underhood Fuse-Relay Center Brake Pressure Modulator Valve Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Hydraulic Control Assembly - Antilock Brakes > Component Information > Locations > Page 8729 Vehicle Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Hydraulic Control Assembly - Antilock Brakes > Component Information > Locations > Page 8730 Hydraulic Control Assembly - Antilock Brakes: Service and Repair The BPMV is not serviceable and must be replaced as a unit. 1. Disconnect battery ground cable, then raise and support vehicle. 2. Disconnect four EBCM electrical connectors. 3. Disconnect combination valve electrical connector and brake pipes. Use shop towels to prevent brake fluid spillage. 4. Disconnect hydraulic lines at BPMV tube adapters, then remove EHCU from vehicle. 5. Remove four Torx bolts from EBCM, then separate BPMV from EBCM. Do not pry on components to separate. 6. Reverse procedure to install, noting the following: a. Install a new EBCM gasket, mounting bolts and transfer tubes. Do not reuse these components. b. Torque combination valve bolts alternately to 6 ft. lbs., then to 12 ft. lbs. c. Torque EBCM Torx bolts to 39 inch lbs. in a crisscross pattern. d. Torque EHCU to base bracket bolts and BPMV bolts to 7 ft. lbs. e. Torque brake pipe fittings to 18 ft. lbs., then bleed brake system. See: Brake Bleeding Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Wheel Speed Sensor > Component Information > Technical Service Bulletins > Customer Interest for Wheel Speed Sensor: > 02-05-25-006B > Jan > 06 > Brakes - Low Speed (Below 5 MPH) ABS Activation Wheel Speed Sensor: Customer Interest Brakes - Low Speed (Below 5 MPH) ABS Activation Bulletin No.: 02-05-25-006B Date: January 05, 2006 TECHNICAL Subject: Antilock Brake (ABS) Activation At Low Speeds (Clean Wheel Speed Sensor Mounting Surface) Models: 1999-2000 Cadillac Escalade 1995-1999 Chevrolet Silverado (Old Style) 1995-2000 Chevrolet Suburban, Tahoe (Old Style) 1995-2003 Chevrolet Astro Van, Blazer, S10 1995-1999 GMC Sierra (Old Style) 1995-2000 GMC Yukon, Yukon XL (Old Style) 1995-2001 GMC Envoy, Jimmy 1995-2003 GMC Safari Van, Sonoma 1995-2001 Oldsmobile Bravada Supercede: This bulletin is being revised to update the correction and warranty information. Please discard Corporate Bulletin Number 02-05-25-006A (Section 05 - Brakes). Condition Some customers may comment on ABS activation at low speeds, usually below 8 km/h (5 mph). Upon investigation, the technician will find no DTCs set. Cause The cause of this condition may be an increased air gap between the wheel speed sensor and the hub reluctor ring due to rust and debris built up on the sensor mounting surface. Correction Measure AC voltage and clean wheel speed sensor mounting surfaces. 1. Raise the vehicle on a hoist. 2. Disconnect both the front wheel speed sensor harness connectors. 3. Place a DVM across the terminals of each sensor connector. 4. Rotate the wheel with hand speed and measure the ACmV's. The reading should be at least 350 ACmV's. 5. If the reading is between 200 and 350 ACmV's, remove the wheel, caliper and rotor in order to gain access to the speed sensor. 6. Remove the wheel speed sensor and plug the hole to prevent debris from falling into the hub during service. 7. Clean the wheel speed sensor mounting surface using a wire brush, sand paper, emery cloth, ScotchBrite(TM) or other suitable material. Be sure to thoroughly clean the wheel speed sensor surface. There should be no rust or corrosion. 8. Check the sensor head to determine if it has been warped/distorted due to the corrosion build up or other causes. Check the mounting surface on the sensor head for flatness by placing it on the edge of a metal machinists scale or other suitable straight edge to measure the flatness. Check the sensor for flatness in multiple (minimum 3) positions/directions. If the sensor head is distorted, replace the sensor. 9. Apply (spray) two thin coats of the specified rust penetrating lubricant (corrosion inhibitor) to the complete sensor mounting surface on the bearing hub. Allow to dry for 3-5 minutes between coats. Use ONLY Rust Penetrating Lubricant, P/N 89022217 (Canadian P/N 89022218). 10. When the corrosion inhibitor is dry to the touch (about 10 minutes), apply a thin layer of bearing grease to the hub surface and sensor 0-ring prior to sensor installation. Use ONLY Wheel Bearing Lubricant, P/N 01051344 (Canadian P/N 993037). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Wheel Speed Sensor > Component Information > Technical Service Bulletins > Customer Interest for Wheel Speed Sensor: > 02-05-25-006B > Jan > 06 > Brakes - Low Speed (Below 5 MPH) ABS Activation > Page 8739 11. Install either the original sensor or a new one in the hub and secure the sensor. Ensure that the sensor is seated flush against the hub. 12. Install the rotor, the caliper and the wheel. 13. Place the DVM across the sensor terminals and recheck the voltage while rotating the wheel by hand. The voltage should now read at least 350 ACmV's. Parts Information Warranty Information For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Wheel Speed Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheel Speed Sensor: > 02-05-25-006B > Jan > 06 > Brakes - Low Speed (Below 5 MPH) ABS Activation Wheel Speed Sensor: All Technical Service Bulletins Brakes - Low Speed (Below 5 MPH) ABS Activation Bulletin No.: 02-05-25-006B Date: January 05, 2006 TECHNICAL Subject: Antilock Brake (ABS) Activation At Low Speeds (Clean Wheel Speed Sensor Mounting Surface) Models: 1999-2000 Cadillac Escalade 1995-1999 Chevrolet Silverado (Old Style) 1995-2000 Chevrolet Suburban, Tahoe (Old Style) 1995-2003 Chevrolet Astro Van, Blazer, S10 1995-1999 GMC Sierra (Old Style) 1995-2000 GMC Yukon, Yukon XL (Old Style) 1995-2001 GMC Envoy, Jimmy 1995-2003 GMC Safari Van, Sonoma 1995-2001 Oldsmobile Bravada Supercede: This bulletin is being revised to update the correction and warranty information. Please discard Corporate Bulletin Number 02-05-25-006A (Section 05 - Brakes). Condition Some customers may comment on ABS activation at low speeds, usually below 8 km/h (5 mph). Upon investigation, the technician will find no DTCs set. Cause The cause of this condition may be an increased air gap between the wheel speed sensor and the hub reluctor ring due to rust and debris built up on the sensor mounting surface. Correction Measure AC voltage and clean wheel speed sensor mounting surfaces. 1. Raise the vehicle on a hoist. 2. Disconnect both the front wheel speed sensor harness connectors. 3. Place a DVM across the terminals of each sensor connector. 4. Rotate the wheel with hand speed and measure the ACmV's. The reading should be at least 350 ACmV's. 5. If the reading is between 200 and 350 ACmV's, remove the wheel, caliper and rotor in order to gain access to the speed sensor. 6. Remove the wheel speed sensor and plug the hole to prevent debris from falling into the hub during service. 7. Clean the wheel speed sensor mounting surface using a wire brush, sand paper, emery cloth, ScotchBrite(TM) or other suitable material. Be sure to thoroughly clean the wheel speed sensor surface. There should be no rust or corrosion. 8. Check the sensor head to determine if it has been warped/distorted due to the corrosion build up or other causes. Check the mounting surface on the sensor head for flatness by placing it on the edge of a metal machinists scale or other suitable straight edge to measure the flatness. Check the sensor for flatness in multiple (minimum 3) positions/directions. If the sensor head is distorted, replace the sensor. 9. Apply (spray) two thin coats of the specified rust penetrating lubricant (corrosion inhibitor) to the complete sensor mounting surface on the bearing hub. Allow to dry for 3-5 minutes between coats. Use ONLY Rust Penetrating Lubricant, P/N 89022217 (Canadian P/N 89022218). 10. When the corrosion inhibitor is dry to the touch (about 10 minutes), apply a thin layer of bearing grease to the hub surface and sensor 0-ring prior to sensor installation. Use ONLY Wheel Bearing Lubricant, P/N 01051344 (Canadian P/N 993037). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Wheel Speed Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheel Speed Sensor: > 02-05-25-006B > Jan > 06 > Brakes - Low Speed (Below 5 MPH) ABS Activation > Page 8745 11. Install either the original sensor or a new one in the hub and secure the sensor. Ensure that the sensor is seated flush against the hub. 12. Install the rotor, the caliper and the wheel. 13. Place the DVM across the sensor terminals and recheck the voltage while rotating the wheel by hand. The voltage should now read at least 350 ACmV's. Parts Information Warranty Information For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Wheel Speed Sensor > Component Information > Technical Service Bulletins > Page 8746 Wheel Speed Sensor: Specifications 2WD Sensor Resistance 1575 to 2420 ohms at -40 to 40 deg F 1980 to 2800 ohms at 41 to 110 deg F 2250 to 3280 ohms at 111 to 200 deg F 2750 to 3850 ohms at 201 to 302 deg F 4WD Sensor Resistance 1900 to 2950 ohms at -40 to 40 deg F 2420 to 3450 ohms at 41 to 110 deg F 2610 to 4100 ohms at 111 to 200 deg F 3320 to 4760 ohms at 201 to 302 deg F Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Wheel Speed Sensor > Component Information > Locations > LH Wheel Speed Sensor: Locations LH front At LH front Wheel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Wheel Speed Sensor > Component Information > Locations > LH > Page 8749 Wheel Speed Sensor: Locations RH front At RH front Wheel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Wheel Speed Sensor > Component Information > Service and Repair > Front Wheel Speed Sensor Wheel Speed Sensor: Service and Repair Front Wheel Speed Sensor 1. Raise and support vehicle, then remove wheel and tire assembly. 2. Disconnect brake caliper assembly and position aside. 3. Remove hub and rotor assembly. 4. Disconnect wheel sensor electrical connector. 5. Remove sensor wire form upper control arm clip. 6. Remove sensor and splash shield assembly attaching bolts, then remove sensor. 7. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Antilock Brakes / Traction Control Systems > Wheel Speed Sensor > Component Information > Service and Repair > Front Wheel Speed Sensor > Page 8752 Wheel Speed Sensor: Service and Repair Rear Wheel Speed Sensor Fig. 58 Rear Wheel Speed Sensor 1. Raise and support vehicle, then remove wheel and tire assembly. 2. Remove brake drum. 3. Remove primary brake shoe. 4. Disconnect sensor electrical connector. 5. Remove sensor wire from rear axle clip. 6. Remove speed sensor attaching bolts, Fig. 58, then remove sensor by pulling wire through hole in backing plate. 7. Reverse procedure to install. Torque speed sensor attaching bolts to 26 ft. lbs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Bleeding > System Information > Service and Repair > Four Wheel Anitlock Brake System Brake Bleeding: Service and Repair Four Wheel Anitlock Brake System Two Person Procedure (Preferred) BLEEDING PROCEDURES Important: Never pump the brake pedal. Fluid cavitation may occur. NOTICE: Gravity and vacuum bleeding are not recommended for this ABS system. Two Person Procedure (Preferred) 1. Raise the vehicle to gain access to the system bleed screws. Install clear tubing on the bleed screws so that air bubbles in the fluid can be seen. 2. Begin by bleeding the system at the right rear wheel, then the left rear, right front and left front. 3. Open one bleed screw at a time 1/2 to 1 full turn. 4. Slowly depress the brake pedal until it reaches its full travel and hold until the bleed screw has been tightened. Release the brake pedal and wait 10-15 seconds for the master cylinder to return to the home position. Important: Repeat steps 1 through 4 until approximately 1 pint of brake fluid has been bled from each wheel. Clean brake fluid should be present at each of the wheel bleed screws. Check the master cylinder fluid level every 4 to 6 strokes of the brake pedal to avoid running the system dry. 5. If any component is replaced which may have caused air to enter the BPMV, use a Scan Tool to run "Function Test" four times while applying the brake pedal firmly. Important: Set the park brake when running the "Function Test." 6. Rebleed all four wheels using steps 1 through 4 to remove the remaining air from the brake system. 7. Evaluate the brake pedal feel before attempting to drive the vehicle and rebleed as many times as necessary to obtain appropriate pedal feel. Pressure Bleeding (Low Pressure) Pressure Bleeding (Low Pressure) 1. Install pressure bleeder per instructions. 2. Install combination valve depressing tool J391 77 if the vehicle is equipped with the metering portion of the combination valve. Remove both dust caps on the combination valve. Install the tool on the end of the combination valve with a brass center pin. 3. Bleed all four wheels beginning at the right rear wheel, then the left rear, right front and left front. Leave the bleed screws open until 1 pint of fluid has been bled out of each wheel. 4. After bleeding all four wheels1 remove the combination valve clip. Use a Scan Tool to run 4 functional tests while applying the brake pedal firmly. 5. Repeat steps 1 through 3 then evaluate the pedal feel. 6. Rebleed the wheels as many times as necessary to obtain good pedal feel before attempting to drive the vehicle. A good bleed will use approximately 2 to 3 quarts of brake fluid. Important: Never reuse brake fluid after it has been bled through a brake system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Bleeding > System Information > Service and Repair > Four Wheel Anitlock Brake System > Page 8757 Brake Bleeding: Service and Repair Master Cylinder Bleeding This procedure can be performed with master cylinder on or off vehicle. 1. Disconnect brake lines at master cylinder, if necessary. 2. Connect suitable lengths of brake lines to master cylinder and immerse other ends of lines in master cylinder reservoirs. 3. Apply master cylinder pushrod or brake pedal with full strokes until air bubbles have disappeared in reservoirs. It may require 20-30 applications to fully eliminate air bubbles. 4. Remove bleeding lines from master cylinder, then install master cylinder on vehicle, if necessary, and connect brake lines. It is not necessary to bleed entire hydraulic system after replacing master cylinder, providing master cylinder has been bled and filled during installation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Bleeding > System Information > Service and Repair > Four Wheel Anitlock Brake System > Page 8758 Brake Bleeding: Service and Repair Bleeding Brake Hydraulic System Pressure Bleeding Pressure Bleeding A diaphragm type pressure bleeder must be used. It must have a rubber diaphragm between the air supply and brake fluid to prevent air, moisture, oil, and other contaminants from entering the hydraulic system. NOTICE: Brake fluid can damage electrical connections and painted surfaces. Use shop cloths, suitable containers, and fender covers to prevent brake fluid from contacting these areas. Always re-seal and wipe off brake fluid containers to prevent spills. Tools Required: Brake Bleeder Adapter J 28434 Wheel Cylinder Bleeder Wrench 1. Fill the pressure tank at least 2,3 full of brake fluid. The bleeder must be bled each time fluid is added. 2. Charge the bleeder to 140 - 170 kPa ( 20-25 psi ). 3. Install the bleeder adapter. 4. If the BPMV of the 4WAL system is replaced or suspected to have air trapped inside, it must be bled next. 5. Bleed each wheel in the following sequence: A. Right rear. B. Left rear. C. Right front. D. Left front. 6. Connect the hose from the bleeder to the adapter at the master cylinder. 7. Open the tank valve. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Bleeding > System Information > Service and Repair > Four Wheel Anitlock Brake System > Page 8759 8. Attach a hose to the bleeder valve. ^ Immerse the opposite end of the hose into a container partially filled with clean brake fluid. 9. Open the bleeder valve at least 3/4 of a turn and allow the fluid to flow until no air is seen in the fluid. 10. Tighten the bleeder valve to 13 Nm ( 110 lb. in. ). 11. Repeat Steps 9 through 11 at all wheels. 12. Check the brake pedal for "sponginess." ^ Repeat the entire bleeding procedure if this condition is found. 13. Disconnect the hose from the bleeder adapter. 14. Remove the bleeder adapter. 15. Fill the master cylinder to the proper level. Manual Bleeding BLEEDING BRAKE HYDRAULIC SYSTEM Bleeding is necessary if air has entered the hydraulic brake system. It may be necessary to bleed the system at all four wheels if a low fluid level allowed the air to enter the system or the brake pipes have been disconnected at the master cylinder or combination valve. If a pipe is disconnected at one wheel, then bleed only that wheel. The time required to bleed the hydraulic system when the master cylinder is removed can be reduced by bench bleeding the master cylinder before installing it on the vehicle. Manual Bleeding If the vehicle is equipped with a vacuum booster, relieve the vacuum reserve by applying the brakes several times with the engine off. NOTICE: Brake fluid will damage electrical connections and painted surfaces. Use shop cloths, suitable containers, and fender covers to prevent the brake fluid from contacting these areas. Always re-seal and wipe off brake fluid containers to prevent spills. Tools Required: J 28434 Wheel Cylinder Bleeder Wrench 1. Fill the master cylinder reservoir with Delco Supreme 11® Hydraulic Brake Fluid GM P/N 1052535 or an equivalent DOT 3 motor vehicle brake fluid. ^ Maintain the fluid level during bleeding. 2. If the master cylinder is suspected to have air in the bore, bleed it before any wheel cylinder or caliper. A. Disconnect the forward brake pipe connection at the master cylinder. B. Allow the brake fluid to flow from the connector port. C. Connect the brake pipe but do not tighten. D. Slowly apply the brake pedal and allow the air to bleed from the loose fitting. E. Tighten the fitting before releasing the pedal. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Bleeding > System Information > Service and Repair > Four Wheel Anitlock Brake System > Page 8760 F. Wait 15 seconds. G. Repeat this sequence, including the 1 5-second wait, until all air is purged from the bore. H. After all air has been removed from the forward connection, repeat this procedure for the rear pipe. 3. If the BPMV of the 4WAL system is replaced or suspected to have air trapped inside, it must be bled next. 4. Bleed each wheel in the following sequence: A. Right rear. B. Left rear. C. Right front D. Left front 5. Attach a hose to the wheel cylinder/caliper bleeder valve. ^ Immerse the opposite end of the hose into a container partially filled with clean brake fluid. 6. Slowly apply the brake pedal one time and hold. 7. Loosen the bleeder valve to purge the air from the wheel cylinder/caliper. 8. Tighten the bleeder valve to 13 Nm ( 110 lb. in. ) and slowly release the pedal. 9. Wait 15 seconds. 10. Repeat this sequence, including the 15-second wait until all air is purged from the wheel cylinder/caliper. 11. Repeat steps 5 through 10 at each wheel until the system is bled. 12. Check the brake pedal for "sponginess" and the brake warning lamp for an indication of unbalanced pressure. Repeat the bleeding procedure to correct either of these conditions. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions Brake Warning Indicator: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8765 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8766 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8767 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8768 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8769 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8770 Brake Warning Indicator: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8771 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8772 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8773 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8774 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8775 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8776 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8777 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8778 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8779 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8780 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8781 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8782 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8783 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8784 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8785 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8786 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8787 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8788 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8789 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8790 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8791 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8792 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8793 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8794 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8795 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8796 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 8797 Brake Warning System Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Diagrams > Page 8798 Brake Warning Indicator: Description and Operation Battery voltage is applied through the GAGES FUSE 4 to the "BRAKE" Indicator when the Ignition Switch is in the RUN, BULB TEST or START positions. The "BRAKE" Indicator can be lit by having ground applied to it from any of three switches or the Antilock Brake Module. The "BRAKE" Indicator will light whenever the Parking Brake is engaged. When the Parking Brake is engaged, ground is supplied through the closed contacts of the Parking Brake Warning Switch to the "BRAKE" Indicator. The "BRAKE" Indicator lights to alert the driver that the Parking Brake is engaged. The "BRAKE" Indicator will light when the Ignition Switch is turned from the "LOCK" to the RUN position. This is when the Antilock Brake Module conducts its initial test which entails lighting the "BRAKE" Indicator and the ABS Indicator. The Antilock Brake Module will also light the "BRAKE" Indicator if there is a malfunction within the Four Wheel Antilock Brake System which is affecting the operation of the base Hydraulic Braking system. The "BRAKE" Indicator will light if there is low Brake fluid pressure in the front or rear Brakes. When the Combination Valve senses low Brake fluid pressure in the front or rear brakes it closes the Brake Pressure Warning Switch. A ground is supplied through the closed contacts of the Brake Pressure Warning Switch to the "BRAKE" Indicator. With both power and ground applied to the "BRAKE" Indication it will light. The "BRAKE" Indicator will also light whenever the Ignition Switch is turned to the BULB TEST position. The Daytime Running Lamps Module senses ground through the Park Brake Warning Switch. When this input is grounded, the Daytime Running Lamps are not energized. Diode D202 prevents Anti-Lock Brake Module or Brake Pressure Warning Switch operation from turning off the Daytime Running Lamps. The "BRAKE" Indicator will also light whenever the Ignition Switch is turned to the BULB TEST Position. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Testing and Inspection > Initial Inspection and Diagnostic Overview Brake Warning Indicator: Initial Inspection and Diagnostic Overview Circuit Operation Battery voltage is applied through the GAGES FUSE 4 to the "BRAKE" Indicator when the Ignition Switch is in the RUN, BULB TEST or START positions. The "BRAKE" Indicator can be lit by having ground applied to it from any of three switches or the Antilock Brake Module. The "BRAKE" Indicator will light whenever the Parking Brake is engaged. When the Parking Brake is engaged, ground is supplied through the closed contacts of the Parking Brake Warning Switch to the "BRAKE" Indicator. The "BRAKE" Indicator lights to alert the driver that the Parking Brake is engaged. The "BRAKE" Indicator will light when the Ignition Switch is turned from the "LOCK" to the RUN position. This is when the Antilock Brake Module conducts its initial test which entails lighting the "BRAKE" Indicator and the ABS Indicator. The Antilock Brake Module will also light the "BRAKE" Indicator if there is a malfunction within the Four Wheel Antilock Brake System which is affecting the operation of the base Hydraulic Braking system. The "BRAKE" Indicator will light if there is low Brake fluid pressure in the front or rear Brakes. When the Combination Valve senses low Brake fluid pressure in the front or rear brakes it closes the Brake Pressure Warning Switch. A ground is supplied through the closed contacts of the Brake Pressure Warning Switch to the "BRAKE" Indicator. With both power and ground applied to the "BRAKE" Indication it will light. The "BRAKE" Indicator will also light whenever the Ignition Switch is turned to the BULB TEST position. The Daytime Running Lamps Module senses ground through the Park Brake Warning Switch. When this input is grounded, the Daytime Running Lamps are not energized. Diode D202 prevents Anti-Lock Brake Module or Brake Pressure Warning Switch operation from turning off the Daytime Running Lamps. The "BRAKE" Indicator will also light whenever the Ignition Switch is turned to the BULB TEST Position. Troubleshooting Hints 1. CHECK condition of GAGES FUSE 4. If Fuse is Open, LOCATE and REPAIR source of overload and REPLACE Fuse. 2. CHECK that Engine Ground G105 is clean and tight. 3. CHECK the "BRAKE" Indicator Bulb for an open filament. 4. CHECK that the Parking Brake is fully released. 5. Make sure that there is an adequate amount of Brake fluid in the reservoir. 6. If any ABS Diagnostic Codes are Set, Refer Antilock Brake System See: Antilock Brakes / Traction Control Systems 7. If the Brake Indicator only lights for the Brake Pressure Warning Switch or for the Anti-Lock Brake Module (Ignition Switch Lock to RUN), then Diode D202 may have opened. 8. If the Brake Indicator only lights for the Ignition Switch in BULB test or for the Park Brake Warning Switch, then Diode 1 in the Underhood Fuse-Relay Center may have opened. ^ CHECK for a broken (or partially broken) wire inside of the insulation which could cause system malfunction but prove "GOOD" in a Continuity/Voltage check with a system disconnected. These Circuits may be intermittent or resistive when loaded, and if possible, should be checked by monitoring for a Voltage drop with the system operational (under load). ^ CHECK for proper installation of aftermarket electronic equipment which may affect the integrity of other systems (Refer "Troubleshooting Procedures"). See: Diagrams/Diagnostic Aids Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Testing and Inspection > Initial Inspection and Diagnostic Overview > Page 8801 Brake Warning Indicator: Symptom Related Diagnostic Procedures Brake Indicator Is Inoperative (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Brake Warning Indicator > Component Information > Testing and Inspection > Initial Inspection and Diagnostic Overview > Page 8802 Brake Indicator Is Inoperative (Part 2 Of 2) Brake Indicator Remains On Continuously Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Specifications > Bendix Single Piston Sliding Caliper Brake Caliper: Specifications Bleeder Valve 9.5 ft.lb Brake Hose To Caliper Bolt 33 ft.lb Caliper Mounting Bolt 28 ft.lb Caliper Support Key Bolt 15 ft.lb Rear Caliper Anchor Plate To Axle 177 ft.lb Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Specifications > Bendix Single Piston Sliding Caliper > Page 8808 Brake Caliper: Specifications Bleeder Valve (Delco) 5 ft.lb Bleeder Valve (Bendix) 9.5 ft.lb Brake Hose To Caliper Bolt 33 ft.lb Caliper Mounting Bolt 38 ft.lb Caliper Support Key Bolt 15 ft.lb Rear Brake Anchor Pin Vehicles w/ gross vehicle weight of 7200 lbs., 147 ft. lbs. Vehicles at or above gross vehicle weight of 8400 lbs., 228 ft. lbs. Rear Caliper Anchor Plate To Axle 177 ft.lb Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Description and Operation > Bendix Single Piston Sliding Caliper Brake Caliper: Description and Operation Bendix Single Piston Sliding Caliper Fig. 1 Disc Brake Assembly The Bendix single piston sliding caliper disc brake is standard equipment on some truck applications, while on other trucks it is used only in Hydro-Boost power brake applications with both front disc brakes and 4 wheel disc brakes. On 4 wheel disc brakes, the front and rear systems are identical. The sliding caliper attaches to and slides on the steering knuckle. The caliper assembly is held in place with a support key and spring Fig. 1. A screw prevents the key from sliding on the steering knuckle. The friction material is bonded with rivets. The inboard and outboard brake pads are not interchangeable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Description and Operation > Bendix Single Piston Sliding Caliper > Page 8811 Brake Caliper: Description and Operation Delco-Moraine Single Piston Caliper With Delco-Moraine 3400 Caliper Fig. 2 Exploded View Of Disc Brake Caliper Assembly. The caliper assembly slides on its mounting surfaces, Fig. 2. Upon brake application, hydraulic pressure against the piston forces the inboard pad against the inboard side of the disc. This action causes the caliper assembly to slide until the outboard pad comes into contact with the disc, which in turn creates a slowing or stopping action. With Delco-Moraine 3486 Caliper Fig. 3 Exploded View Of Disc Brake Caliper Assembly. The caliper assembly slides on its mounting surfaces, Fig. 3. Upon brake application, hydraulic pressure against the piston forces the inboard pad against the inboard side of the disc. This action causes the caliper assembly to slide until the outboard pad comes into contact with the disc, which in turn creates a slowing or stopping action. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Description and Operation > Page 8812 Brake Caliper: Testing and Inspection Should it become necessary to remove the caliper for installation of new parts, clean all parts in denatured alcohol, wipe dry using lint-free cloths. Using compressed air, blow out drilled passages and bores. Check dust boots for punctures or tears. If punctures or tears are evident, new boots should be installed upon reassembly. Inspect piston bores in both housings for scoring or pitting. Bores that show light scratches or corrosion can usually be cleaned with crocus cloth. However, bores that have deep scratches or scoring may be honed, provided the diameter of the bore is not increased more than .002 inch. If the bore does not clean up within this specification, a new caliper housing should be installed (black stains on the bore walls are caused by piston seals and will do no harm). When using a hone, be sure to install the hone baffle before honing bore. The baffle is used to protect the hone stones from damage. Use extreme care in cleaning the caliper after honing. Remove all dust and grit by flushing the caliper with denatured alcohol. Wipe dry with clean lint-free cloth and then clean a second time in the same manner. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper Brake Caliper: Service and Repair Bendix Single Piston Sliding Caliper Removal/Installation REMOVAL Fig. 2 Bottoming Position In Bore Fig. 3 Removing Caliper Support Key Fig. 4 Removing Or Installing Caliper 1. Siphon two-thirds of brake fluid from master cylinder reservoir serving front disc brakes. 2. Raise vehicle, support on jack stands and remove front wheels. 3. Bottom the caliper piston in bore. Insert a screwdriver between inboard shoe and piston, then pry piston back into bore. The piston can also be bottomed in the bore with a large C-clamp, Fig. 2. 4. Remove support key retaining screw. 5. Drive caliper support key and spring from steering knuckle with a suitable drift and hammer, Fig. 3. 6. Lift caliper from anchor plate and off rotor, Fig. 4. Hang caliper from coil spring with wire. Do not allow caliper to hang from brake hose. 7. Remove inboard pad from steering knuckle, then the anti-rattle spring from the pad. 8. Remove outboard pad from caliper. It may be necessary to loosen the pad with a hammer to permit removal. INSTALLATION 1. Clean and lubricate sliding surfaces of caliper and the anchor plate with Delco Silicone Lube, P/N 5459912, or equivalent. 2. Install anti-rattle spring on inboard pad, and ensure looped section of clip is facing away from rotor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8815 3. Install inboard pad in steering knuckle. 4. Install outboard pad in caliper. Ensure pad is seated fully into outboard arms of caliper. It may be necessary to tap the ears and bottom tab with a hammer to seat the pad being careful not to hit the friction material. 5. Place caliper assembly over rotor and position in steering knuckle. Ensure dust boot is not torn or improperly positioned by inboard pad during caliper installation. 6. Align caliper with steering knuckle abutment surfaces, then insert support key and spring between abutment surfaces at the trailing end of caliper and steering knuckle. With a hammer and brass drift, drive caliper support key and spring into position, then install and torque support key retaining screw to 12-18 ft. lbs. 7. Refill master cylinder to within one inch of rim. Press brake pedal several times to seat pads. 8. Install front wheels and lower vehicle. Disassembly/Inspection/Assembly DISASSEMBLY Fig. 5 Removing Caliper Piston Fig. 6 Exploded View Of Disc Brake Caliper Assembly 1. Drain brake fluid from caliper. 2. Position caliper with shop cloths, Fig. 5, and apply compressed air to fluid inlet port to ease piston from bore. Do not attempt to catch piston or to protect it when applying compressed air, since personal injury is possible. 3. Remove dust boot, then the piston seal from bore, Fig. 6. Use wooden or plastic tool to remove piston seal since metal tools may damage piston. 4. Remove bleeder screw INSPECTION Clean all parts in denatured alcohol, wipe dry using lint-free cloths. Using compressed air, blow out drilled passages and bores. Check dust boots for punctures or tears. If punctures or tears are evident, new boots should be installed upon reassembly. Inspect piston bores in both housings for scoring or pitting. Bores that show light scratches or corrosion can usually be cleaned with crocus cloth. However, bores that have deep scratches or scoring may be honed, provided the diameter of the bore is not increased more than .002 inch. If the bore does not clean up within this specification, a new caliper housing should be installed (black stains on the bore walls are caused by piston seals and will do no harm). When using a hone, be sure to install the hone baffle before honing bore. The baffle is used to protect the hone stones from damage. Use extreme care in cleaning the caliper after honing. Remove all dust and grit by flushing the caliper with denatured alcohol. Wipe dry with clean lint-free cloth and then clean a second time in the same manner. ASSEMBLY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8816 Fig. 7 Installing Caliper Piston Boot Fig. 8 Installing Piston In Caliper 1. Coat square cut piston seal with clean brake fluid, then install seal into piston bore. Work seal into groove with clean fingers. 2. Install and torque bleeder screw to specifications. 3. Lubricate boot and installation tool No. J-24548 with clean brake fluid, then place dust seal on tool, allowing 1/4 inch of tool to extend past small lip of boot, Fig. 7. 4. Place dust seal and tool over piston bore, then work large lip of boot into seal groove, Fig. 8. Ensure dust seal is fully seated. 5. Lubricate caliper piston and insert through tool. Center piston in bore and use a hammer handle to apply pressure to install piston halfway into bore, Fig. 8. 6. Remove installation tool No. J-24548 and seat small lip of boot in caliper piston groove, then bottom piston in bore. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8817 Brake Caliper: Service and Repair Delco-Moraine Single Piston Caliper Removal/Installation REMOVAL Fig. 2 Compressing Piston & Pad With C-clamp 1. Siphon enough brake fluid out of the master cylinder to bring fluid level to 1/3 full to avoid fluid overflow when the caliper piston is pushed back into its bore. 2. Raise and support vehicle, remove front wheels. 3. Using a C-clamp, as illustrated in Fig. 2, push piston back into its bore. 4. Remove two mounting bolts and lift caliper away from disc. INSTALLATION 1. Position caliper over disc, lining up mounting holes in caliper with holes in mounting bracket. If brake hose was not disconnected during removal, be sure not to kink it during installation. 2. Start mounting bolts through sleeves in inboard caliper ears and the mounting bracket, making sure ends of bolts pass under ears on inboard shoe. Right and left calipers must not be interchanged. 3. Push mounting bolts through to engage holes in the outboard ears. Then thread mounting bolts into bracket. 4. Torque mounting bolts to specifications. 5. If brake hose was removed, reconnect it and bleed the calipers. 6. Replace front wheels, lower vehicle and add brake fluid to master cylinder to bring level to 1/4 inch from top. Before moving vehicle, pump brake pedal several times to be sure it is firm. Do not move vehicle until a firm pedal is obtained. Disassembly/Inspection/Assembly DISASSEMBLY Fig. 4 Removing Piston From Caliper 1. Disconnect hose from the caliper being careful not to lose copper washers. 2. Remove caliper as outlined above. 3. Drain brake fluid from caliper. 4. Pad caliper interior with clean shop towels and apply compressed air to remove piston, Fig. 4. Use just enough air pressure to ease piston out of Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8818 bore. When applying compressed air do not place fingers in front of piston in an attempt to catch or protect it as this could result in serious injury. 5. Carefully pry dust boot out of bore. 6. Using a small piece of wood or plastic, remove piston seal from bore. Do not use a metal tool of any kind to remove seal as it may damage bore. 7. Remove bleeder valve. INSPECTION Clean all parts in denatured alcohol, wipe dry using lint-free cloths. Using compressed air, blow out drilled passages and bores. Check dust boots for punctures or tears. If punctures or tears are evident, new boots should be installed upon reassembly. Inspect piston bores in both housings for scoring or pitting. Bores that show light scratches or corrosion can usually be cleaned with crocus cloth. However, bores that have deep scratches or scoring may be honed, provided the diameter of the bore is not increased more than .002 inch. If the bore does not clean up within this specification, a new caliper housing should be installed (black stains on the bore walls are caused by piston seals and will do no harm). When using a hone, be sure to install the hone baffle before honing bore. The baffle is used to protect the hone stones from damage. Use extreme care in cleaning the caliper after honing. Remove all dust and grit by flushing the caliper with denatured alcohol. Wipe dry with clean lint-free cloth and then clean a second time in the same manner. ASSEMBLY Fig. 5 Installing Boot To Piston Fig. 6 Installing Boot To Caliper 1. Lubricate caliper piston bore and new piston seal with clean brake fluid. Position seal in bore groove. 2. Lubricate piston with clean brake fluid and assemble a new boot into the groove in the piston so the fold faces the open end of the piston, Fig. 5. 3. Using care not to unseat the seal, insert piston into bore and force the piston to the bottom of the bore. 4. Position dust boot in caliper counterbore and install, Fig. 6. Check the boot installation to be sure the retaining ring molded into the boot is not bent and that the boot is installed below the caliper face and evenly all around. If the boot is not fully installed, dirt and moisture may enter the bore and cause corrosion. 5. If available, use new copper washers discarding the old washers and install the brake hose to the caliper. 6. Install pads and caliper assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8819 Brake Caliper: Service and Repair Removal and Installation Delco CALIPER Remove or Disconnect 1. Two-thirds of the brake fluid from master cylinder. 2. Raise vehicle and support with safety stands. 3. Tire and wheel. ^ On models with composite rotor, reinstall two lug nuts to retain rotor. Compressing Piston Prior To Caliper Removal 4. Compress piston using adjustable pliers over inboard lining (7) tab and caliper housing flange (12). 5. Brake hose from caliper by removing inlet fitting bolt (14). 6. Mounting bolts (2). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8820 7. Bolt boots (1). Suspending The Caliper 8. Caliper (12). Delco Shoe And Lining Assembly (3400) 9. Mounting bolt seals (4), if used. 10. Bushings (3). NOTE: Inspect the mounting bolt and sleeve assemblies for corrosion. Replace if any is found. Do not attempt to polish away corrosion. Inspect bolt boots for nicks, cuts, or corrosion. Replace if any are found. NOTE: Clean the caliper assembly and install a new brake hardware kit anytime it is removed from rotor. Install or Connect CAUTION: Always use the correct fastener in the proper location. When you replace a fastener, use ONLY the exact part number for that application. General Motors will call out those fasteners that require a replacement after removal. General Motors will also call out the fasteners that require thread lockers or thread sealant. Unless otherwise specified, do not use supplemental coatings (paints, greases, or other corrosion inhibitors) on threaded fasteners or fastener joint interfaces. Generally, such coatings adversely affect the fastener torque and joint clamping force, and may damage the fastener. When you install fasteners, use the correct tightening sequence and specifications. Following these instructions can help you avoid damage to parts and systems. NOTE: Any new rotor must have the protective coating removed from the friction surfaces before being placed in service. Use Goodwrench Brake Parts Cleaner (GM PIN 12345754), or equivalent, and wipe the surface clean with clean cloths. Do not use gasoline, kerosene or other oil-based solvents which may leave an oily residue. This residue is damaging to brake linings and flammable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8821 Delco Shoe And Lining Assembly (3400) 1. New bushings (3) and bolt seals (4). Mounting Bolt Lubrication (Delco 3400) 2. Lubricate bushings (3) and mounting bolt seals (4) with GM P/N 18010909 or equivalent. 3. New bolt boots (1). 4. Caliper (12). ^ Fill both housing cavities between bushings (3) with GM P/N 18010909, or equivalent. 5. Mounting bolt and sleeve assemblies (2). ^ Tighten bolt (2) to 51 Nm (38 lb. ft.). The bolt boots (1) must remain secure after tightening bolts. 6. Brake hose to caliper. ^ Tighten brake hose bolt to 45 Nm (33 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8822 Caliper To Bracket Clearance 7. Measure clearance between caliper (12) and bracket stops (16). If necessary, remove caliper and file the ends of bracket (16) to obtain 0.26 to 0.60 mm (0.010 to 0.024 inch) total clearance. Measure the clearances individually and add them together. 8. Tire and wheel. NOTE: Before moving the vehicle, pump the brake pedal several times to make sure it is firm. Do not move the vehicle until a firm pedal is obtained. Check the fluid level in the master cylinder after pumping the brakes. Bendix CALIPER Shoe And Lining Assembly Remove or Disconnect 1. Two-thirds of the brake fluid from master cylinder. 2. Raise vehicle and support with safety stands. 3. Mark relationship of wheel to hub. 4. Tire and wheel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8823 Compressing The Caliper Piston 5. Position a C-clamp and tighten until piston bottoms in bore. 6. C-Clamp. 7. Brake hose. Caliper Mounting 8. Bolt (2). 9. Support key (3) and spring (4). Removing The Caliper Support Key ^ Use a brass punch and a hammer to drive the support key out. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8824 Suspending The Caliper 10. Caliper assembly (1). NOTE: Inspect the inside of the caliper assembly for signs of fluid leakage. Clean: Use a wire brush to remove any corrosion from the machined surfaces of the anchor plate and caliper. Install or Connect CAUTION: Always use the correct fastener in the proper location. When you replace a fastener, use ONLY the exact part number for that application. General Motors will call out those fasteners that require a replacement after removal. General Motors will also call out the fasteners that require thread lockers or thread sealant. Unless otherwise specified, do not use supplemental coatings (paints, greases, or other corrosion inhibitors) on threaded fasteners or fastener joint interfaces. Generally, such coatings adversely affect the fastener torque and joint clamping force, and may damage the fastener. When you install fasteners, use the correct tightening sequence and specifications. Following these instructions can help you avoid damage to parts and systems. NOTE: Any new rotor must have the protective coating removed from the friction surfaces before being placed in service. Use Goodwrench Brake Parts Cleaner (GM PIN 12345754), or equivalent, and wipe the surface clean with clean cloths. Do not use gasoline, kerosene or other oil-based solvents which may leave an oily residue. This residue is damaging to brake linings and flammable. 1. Lubricate caliper and anchor plate sliding surfaces with Shell Aeroshell No. 5, or equivalent. Suspending The Caliper 2. Caliper assembly. CAUTION: Make sure the brake hose Is not twisted or kinked after installation. Damage to the hose could result. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8825 CAUTION: Do not use anti-seize type products on the caliper V-ways and anchor plate guide way surfaces. These products are not lubricants and result in high caliper slide forces, which can cause increased wear of the brake pads. Installing The Caliper Support Key 3. Spring (4) and support key (3). Use a brass punch and hammer to drive the support key in place. 4. Caliper lock mounting bolts. The boss on the bolt must fit into the circular cutout in the key. ^ Tighten bolts to 20 Nm (15 lb. ft.). 5. Brake hose. ^ Tighten brake hose bolt to 45 Nm (33 lb. ft.). 6. Bleed brake system. Refer to Hydraulic System Service and Repair. 7. Tire and wheel. 8. Lower the vehicle. CAUTION: Before moving the vehicle, pump the brake pedal several times to make sure it is firm. Do not move the vehicle until a firm pedal is obtained. Check the brake fluid level in the master cylinder after pumping the brakes. Rear Disc Brakes CALIPER Remove or Disconnect 1. Two-thirds of the brake fluid from master cylinder. 2. Raise vehicle and support with safety stands. 3. Mark relationship of wheel to hub. 4. Tire and wheel. Compressing The Caliper Piston 5. Position a C-clamp and tighten until piston bottoms in bore. 6. C-Clamp. 7. Brake hose. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8826 Disc Brake Assembly 8. Bolt (2). 9. Support key (3) and spring (4). Removing The Caliper Support Key ^ Use a brass punch and a hammer to drive the support key out. Suspending The Caliper 10. Caliper assembly (1). NOTE: Inspect the inside of the caliper assembly for signs of fluid leakage. If any is found, refer to Overhaul. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8827 Clean: Use a wire brush to remove any corrosion from the machined surfaces of the anchor plate and caliper. Install or Connect CAUTION: Always use the correct fastener in the proper location. When you replace a fastener, use ONLY the exact part number for that application. General Motors will call out those fasteners that require a replacement after removal. General Motors will also call out the fasteners that require thread lockers or thread sealant. Unless otherwise specified, do not use supplemental coatings (paints, greases, or other corrosion inhibitors) on threaded fasteners or fastener joint interfaces. Generally, such coatings adversely affect the fastener torque and joint clamping force, and may damage the fastener. When you install fasteners, use the correct tightening sequence and specifications. Following these instructions can help you avoid damage to parts and systems. NOTE: Any new rotor must have the protective coating removed from the friction surfaces before being placed in service. Use Goodwrench Brake Parts Cleaner (GM P/N 12345754), or equivalent, and wipe the surface clean with clean cloths. Do not use gasoline, kerosene or other oil-based solvents which may leave an oily residue. This residue is damaging to brake linings and flammable. 1. Lubricate caliper and anchor plate sliding surfaces with Shell Aeroshell Grade 5 lubricant or equivalent. Suspending The Caliper 2. Caliper assembly. CAUTION: Make sure the brake hose Is not twisted or kinked after installation. Damage to the hose could result. CAUTION: Do not use "never sieze" type products on the caliper V-ways and anchor plate guide way surfaces. These products are not lubricants and result in high caliper slide forces, which can cause increased wear of the brake pads. Installing The Caliper Support Key 3. Spring (4) and support key (3). Use a brass punch and hammer to drive the support key in place. 4. Caliper lock mounting bolts. The boss on the bolt must fit into the circular cutout in the key. ^ Tighten bolts to 20 Nm (15 lb. ft.). 5. Brake hose. ^ Tighten brake hose bolt to 45 Nm (33 lb. ft.). 6. Bleed brake system. Refer to Hydraulic System Service and Repair. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8828 7. Tire and wheel. 8. Lower the vehicle. CAUTION: Before moving the vehicle, pump the brake pedal several times to make sure it is firm. Do not move the vehicle until a firm pedal is obtained. Check the brake fluid level in the master cylinder after pumping the brakes. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Pad > Component Information > Technical Service Bulletins > Customer Interest: > 99-05-24-001A > Sep > 99 > Brakes - Lead/Pull & Front Brake Wear Brake Pad: Customer Interest Brakes - Lead/Pull & Front Brake Wear File In Section: 05 - Brakes Bulletin No.: 99-05-24-001A Date: September, 1999 TECHNICAL Subject: Brake Lead/Pull and Front Brake Wear (Replace Front Brake Pads and/or Rear Brake Shoes) Models: 1992-99 Chevrolet and GMC C/K Cab Chassis, Crew Cab, and Pickup Models with Power Brakes (RPO JB8) 1992-99 Chevrolet and GMC C/K Suburban Models with 8600 # GVW (RPO C6P) 1996-2000 Chevrolet and GMC G Vans with Power Brakes (RPO JD7 & JB8) and GVW's of 7,700 # up to 9,500 # (RPO's C3F, C6P, & E23) This bulletin is being revised to update information in the Models Section and Correction Information. Please discard Corporate Bulletin Number 99-05-24-001 (Section 5 - Brakes). Condition Some owners may comment about the vehicle leading or pulling to either side while applying the brakes, and premature front brake wear, especially vehicles that have been used to tow a heavy load. Cause The condition may be caused by wearing of the front brake material. Improvements to the above conditions can be gained through brake material modifications. On the Suburban models, the best performance from this new brake material can be achieved with replacing the brake combination valve. Correction Replace the rear brake shoes with P/N 18029651. THIS FIX DOES NOT APPLY TO THE 13 x 2-1/2 BRAKE, DURASTOP(TM) P/N 18029650, OR ANY OTHER SIZE. On Suburban models, a brake combination valve must be replaced. ALL OTHER MODELS (C/K, G Van), NO BRAKE COMBINATION VALVE CHANGE IS REQUIRED. Refer to the Drum Brakes or Hydraulic Brakes subsection of the appropriate Service Manual. For G2/G3 Series Vans only (with GVW's of 7,700 # up to 9,500 # - RPOs C3F, C6P, E23) also replace the front brakes pads with P/N 12471685. Refer to the Disc Brake subsection of the appropriate Service Manual. Important: The new front brake pad material has been selected for improved wear characteristics. Some customers may experience increased brake noise from this brake pad and should be advised that some squeal is a characteristic of this particular material. Important: If you encounter disc brakes that are extremely worn on the inboard side, with very little wear to the outboard side, verify the clearance between the caliper and the steering knuckle bracket stops. MEASURE THE CLEARANCES INDIVIDUALLY AND ADD THE CLEARANCES TOGETHER FOR TOTAL CLEARANCE BEFORE REMOVING THE CALIPER. If the caliper (total clearance) to the steering knuckle stops is under 0.26 mm (0.010 in), correct this by filing metal off at the steering knuckle stops in order to obtain a total clearance of 0.26 to 0.60 mm (0.010 to 0.024 in). DO NOT FILE METAL OFF OF THE CALIPER. Refer to the Disc Brake subsection of the appropriate Service Manual for additional information on this procedure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Pad > Component Information > Technical Service Bulletins > Customer Interest: > 99-05-24-001A > Sep > 99 > Brakes - Lead/Pull & Front Brake Wear > Page 8837 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Pad > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 99-05-24-001A > Sep > 99 > Brakes - Lead/Pull & Front Brake Wear Brake Pad: All Technical Service Bulletins Brakes - Lead/Pull & Front Brake Wear File In Section: 05 - Brakes Bulletin No.: 99-05-24-001A Date: September, 1999 TECHNICAL Subject: Brake Lead/Pull and Front Brake Wear (Replace Front Brake Pads and/or Rear Brake Shoes) Models: 1992-99 Chevrolet and GMC C/K Cab Chassis, Crew Cab, and Pickup Models with Power Brakes (RPO JB8) 1992-99 Chevrolet and GMC C/K Suburban Models with 8600 # GVW (RPO C6P) 1996-2000 Chevrolet and GMC G Vans with Power Brakes (RPO JD7 & JB8) and GVW's of 7,700 # up to 9,500 # (RPO's C3F, C6P, & E23) This bulletin is being revised to update information in the Models Section and Correction Information. Please discard Corporate Bulletin Number 99-05-24-001 (Section 5 - Brakes). Condition Some owners may comment about the vehicle leading or pulling to either side while applying the brakes, and premature front brake wear, especially vehicles that have been used to tow a heavy load. Cause The condition may be caused by wearing of the front brake material. Improvements to the above conditions can be gained through brake material modifications. On the Suburban models, the best performance from this new brake material can be achieved with replacing the brake combination valve. Correction Replace the rear brake shoes with P/N 18029651. THIS FIX DOES NOT APPLY TO THE 13 x 2-1/2 BRAKE, DURASTOP(TM) P/N 18029650, OR ANY OTHER SIZE. On Suburban models, a brake combination valve must be replaced. ALL OTHER MODELS (C/K, G Van), NO BRAKE COMBINATION VALVE CHANGE IS REQUIRED. Refer to the Drum Brakes or Hydraulic Brakes subsection of the appropriate Service Manual. For G2/G3 Series Vans only (with GVW's of 7,700 # up to 9,500 # - RPOs C3F, C6P, E23) also replace the front brakes pads with P/N 12471685. Refer to the Disc Brake subsection of the appropriate Service Manual. Important: The new front brake pad material has been selected for improved wear characteristics. Some customers may experience increased brake noise from this brake pad and should be advised that some squeal is a characteristic of this particular material. Important: If you encounter disc brakes that are extremely worn on the inboard side, with very little wear to the outboard side, verify the clearance between the caliper and the steering knuckle bracket stops. MEASURE THE CLEARANCES INDIVIDUALLY AND ADD THE CLEARANCES TOGETHER FOR TOTAL CLEARANCE BEFORE REMOVING THE CALIPER. If the caliper (total clearance) to the steering knuckle stops is under 0.26 mm (0.010 in), correct this by filing metal off at the steering knuckle stops in order to obtain a total clearance of 0.26 to 0.60 mm (0.010 to 0.024 in). DO NOT FILE METAL OFF OF THE CALIPER. Refer to the Disc Brake subsection of the appropriate Service Manual for additional information on this procedure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Pad > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 99-05-24-001A > Sep > 99 > Brakes - Lead/Pull & Front Brake Wear > Page 8843 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Pad > Component Information > Technical Service Bulletins > All Other Service Bulletins for Brake Pad: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder Control Module: All Technical Service Bulletins A/T - Upshift Flare/No 3rd or 4th/Launch Shudder File In Section: 07 - Transmission/Transaxle Bulletin No.: 00-07-30-026 Date: December 2000 TECHNICAL Subject: Automatic Transmission 1-2 and/or 2-3 Upshift Slip/Flare, No 3rd or 4th gear, Launch Shudder (Revise VCM Wiring) Models: 1996 Chevrolet and GMC C/K, S/T, M/L, G1, G2, P3 Models 1996 Oldsmobile Bravada with VCM and 4L60-E (M30) or 4L80-E (MT1) Automatic Transmission This bulletin is being reissued to ensure that correct procedures are followed for this condition. Please discard Corporate Bulletin Number 66-71-03A (Section 7 - Automatic Transmission). When performing a transmission replacement labor operation K7000 on these vehicles with a 4L60-E or 4L80-E, you must include front chassis wire repair labor operation N6112. Inspect the VCM to verify the latest part number revision (16244210). Condition Some owners may comment that the automatic transmission has either a slip or flare on the 1-2 and/or 2-3 upshift, or no 3rd or 4th gear, or launch shudder. Upon investigation, the technician may find a DTC P1870 stored in the VCM. Cause A poor internal ground between the two circuit boards of the VCM may cause the VCM to command erratic line pressure at the pressure control (PC) solenoid valve. Correction Using harness jumper wire and instruction kit, P/N 12167310, revise the wiring harness at the VCM connector. Corrections were made to the VCM beginning 2/14/96. The corrected VCMs are identified with service number 16244210 on the VCM identification label. Procedure The following is a summary of the instructions included with the service kit: 1. Remove the negative terminal from the battery. 2. Move the wire located at connector J3 (WHITE/GREY/CLEAR), pin 18 to connector J1 (BLUE), pin 23. 3. Install the jumper wire between connector J2 (RED), pin 26 and connector J3 (WHITE/GREY/CLEAR), pin 18. 4. Install the tag included in the kit around the. VCM wiring harness. This tag notes that the wiring harness has been modified. 5. Reconnect the negative battery terminal. Road test to verify that the condition has been corrected. If any of the following conditions are noted, the transmission should be repaired or replaced using the most cost effective method. Canadian dealers should repair the transmission. ^ Transmission fluid oxidation or excessive sediment. ^ Transmission slip or flare after this service fix is performed. ^ DTC P1870 is stored on a 4L60-E (M30). The following tools are available from Kent-Moore (1-800-345-2233) for use in removing and relocating the VCM wires: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Pad > Component Information > Technical Service Bulletins > All Other Service Bulletins for Brake Pad: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder > Page 8849 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Pad > Component Information > Technical Service Bulletins > All Other Service Bulletins for Brake Pad: > 00-07-30-026 > Dec > 00 > A/T - Upshift Flare/No 3rd or 4th/Launch Shudder > Page 8855 ^ J 41758 Terminal Tool; used to remove the wire from the VCM connector. ^ J 41759 Punch; used to punch a new hole through the connector seal. Parts Information Part Number Description Qty 12167310 Harness Jumper Wire Kit 1 Parts are currently available from GMSPO. Warranty Information Labor Operation Description Labor Time N6112 Wire Repair, Front Use Published Chassis Labor Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Pad > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper Brake Pad: Service and Repair Bendix Single Piston Sliding Caliper NOTE: It is not necessary to disconnect the brake hose, however, use caution not to twist or kink hose. REMOVAL Fig. 2 Bottoming Position In Bore Fig. 3 Removing Caliper Support Key Fig. 4 Removing Or Installing Caliper 1. Siphon two-thirds of brake fluid from master cylinder reservoir serving front disc brakes. 2. Raise vehicle, support on jack stands and remove front wheels. 3. Bottom the caliper piston in bore. Insert a screwdriver between inboard shoe and piston, then pry piston back into bore. The piston can also be bottomed in the bore with a large C-clamp, Fig. 2. 4. Remove support key retaining screw. 5. Drive caliper support key and spring from steering knuckle with a suitable drift and hammer, Fig. 3. 6. Lift caliper from anchor plate and off rotor, Fig. 4. Hang caliper from coil spring with wire. Do not allow caliper to hang from brake hose. 7. Remove inboard pad from steering knuckle, then the anti-rattle spring from the pad. 8. Remove outboard pad from caliper. It may be necessary to loosen the pad with a hammer to permit removal. INSTALLATION 1. Clean and lubricate sliding surfaces of caliper and the anchor plate with Delco Silicone Lube, P/N 5459912, or equivalent. 2. Install anti-rattle spring on inboard pad, and ensure looped section of clip is facing away from rotor. 3. Install inboard pad in steering knuckle. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Pad > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8858 4. Install outboard pad in caliper. Ensure pad is seated fully into outboard arms of caliper. It may be necessary to tap the ears and bottom tab with a hammer to seat the pad being careful not to hit the friction material. 5. Place caliper assembly over rotor and position in steering knuckle. Ensure dust boot is not torn or improperly positioned by inboard pad during caliper installation. 6. Align caliper with steering knuckle abutment surfaces, then insert support key and spring between abutment surfaces at the trailing end of caliper and steering knuckle. With a hammer and brass drift, drive caliper support key and spring into position, then install and torque support key retaining screw to 12-18 ft. lbs. 7. Refill master cylinder to within one inch of rim. Press brake pedal several times to seat pads. 8. Install front wheels and lower vehicle. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Pad > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8859 Brake Pad: Service and Repair Delco-Moraine Single Piston Caliper REMOVAL 1. Remove caliper assembly as outlined above. 2. Remove inboard pad with retainer spring. Dislodge outboard pad and position caliper on the front suspension so the brake hose will not support the weight of the caliper. 3. Remove two sleeves from inboard ears of the caliper. 4. Remove four rubber bushings from the grooves in each of the caliper ears. INSTALLATION Fig. 3 Fitting Pad To Caliper 1. Lubricate new sleeves, rubber bushings, bushing grooves and mounting bolt ends with Delco Silicone Lube or equivalent. 2. Install new bushings and sleeves in caliper ears. Position the sleeve so that the end toward the pad is flush with the machined surface of the ear. 3. Install retainer spring on back of inboard pad. 4. Position inboard pad with ears up and retainer spring facing the piston then press pad into piston bore until seated. a. Some inboard pads contain a wear sensor, the sensor should be toward the rear of the caliper when installed properly. 5. Position outboard pad to caliper interior with pad ears over caliper ears and tab at bottom of pad seated in caliper cutout. 6. With pads installed, install caliper as described under caliper installation. 7. Seat the outboard pad to the caliper by grasping the ears with channel locks and pressing together firmly, Fig. 3. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Rotor/Disc > Component Information > Technical Service Bulletins > Brakes - Rotor & Hub Flange Cleaning Tool Revision Brake Rotor/Disc: Technical Service Bulletins Brakes - Rotor & Hub Flange Cleaning Tool Revision File In Section: 5 - Brakes Bulletin No.: 73-50-37 Date: January, 1998 INFORMATION Subject: Revision to J 42450 Tool; Proper Brake Rotor and Hub Flange Surface Cleaning Models: 1998 and Prior Passenger Cars and Light Duty Trucks - with Disc Brakes (Rotor and Hub Separate) This bulletin is being revised to update the following text. This bulletin is being issued to inform the dealer about a revision to tool J 42450 and reinforce the need for proper hub flange and brake rotor mating surface cleaning during service. Tool J 42450 is a cleaning pad arbor and pad system that fits over the wheel stud and cleans the portion of the hub surface that is very difficult to reach with normal rotary cleaning pads. Tool J 42450 is being revised to J 42450-A to improve the hook and loop material retention. Any dealer experiencing problems with tool J 42450 should contact Kent-Moore at 1-800-345-2233 for a revised arbor at no charge. Anytime the brake rotor has been separated from the hub bearing flange or if rotor machining is necessary, the rotor and hub should be marked to maintain the original position. Clean the hub flange of all dirt and foreign material using special tool J 42450 or J 42450-A. Clean both sides of the brake rotor hub using an aggressive (80 grit) abrasive sanding pad on a rotary disc. Properly cleaning the rotor surfaces before rotor machining or reassembly ensures that dirt and corrosion will not add lateral runout to the rotor. Proper cleaning of the hub flange will also minimize the stack-up of lateral runout. On reassembly, the rotor should be reinstalled aligning the marks made on disassembly. Always use a torque wrench or the appropriate Torque Socket found in J 39544-KIT on an impact wrench when installing the wheel and tire assembly. Torque all wheel nuts using the correct sequence and torque. Refer to the Tire and Wheel Sub-Section in the applicable Service Manual. Excessive torque or torque variation between wheel nuts may cause distortion of the hub and rotor mating surface. This distortion may cause lateral runout and lead to brake pulsation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Rotor/Disc > Component Information > Specifications > Bendix Single Piston Sliding Caliper Brake Rotor/Disc: Specifications Bendix Single Piston Sliding Caliper Front Rotor, All Models and Engines Front Rotor, All Models and Engines Nominal Thickness 1.25 in Minimum Refinish Thickness 1.23 in Minimum Replacement Thickness 1.215 in Thickness Variation (Parallelism) .0005 in Runout (TIR) .003 in Rear Rotor, Model C/K Rear Rotor, Model C/K Nominal Thickness 1.428 - 1.443 in Minimum Refinish Thickness 1.382 in Minimum Replacement Thickness 1.366 in Thickness Variation (Parallelism) 0.0010 in Runout (TIR) 0.010 in Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Rotor/Disc > Component Information > Specifications > Bendix Single Piston Sliding Caliper > Page 8866 Brake Rotor/Disc: Specifications Front Rotor Front Rotor Nominal Thickness 1.25 in Minimum Refinish Thickness 1.23 in Minimum Replacement Thickness 1.215 in Thickness Variation (Parallelism) .0005 in Runout (TIR) .003 in Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Rotor/Disc > Component Information > Specifications > Page 8867 Brake Rotor/Disc: Testing and Inspection This article has been updated with bulletin No: 00-05-22-002B. BRAKE ROTOR DIAGNOSIS AND SERVICE GUIDELINES IMPORTANT: Certain conditions may apply to individual vehicles regarding specific repairs which differ from those outlined in this bulletin. For information regarding lateral runout correction, refer to Bulletin Number 01-05-23-001A, Brake Align System for Brake Rotor Lateral Runout Correction. For other conditions, refer to those specific repairs in applicable bulletins. Original equipment rotor surfaces are ground to ensure smooth finish and parallelism between mounting and friction surfaces. New rotors SHOULD NOT be resurfaced before installation. When rotor turning is necessary, it is essential that you use a high quality brake lathe. Rotors, when remounted on the hub, should have less than .055 mm (.002 in) lateral runout. Brake rotors should only be turned when one of the following rotor surface conditions exist: 1. Severe scoring - depth in excess of 1.5 mm (0.060 in). 2. Pulsation concerns from: ^ Lateral runout in excess of .055 mm (.002 in). ^ Thickness variation in excess of 0.025 mm (0.001 in). ^ Excessive corrosion on rotor braking surfaces. Rotors are not to be resurfaced in an attempt to correct the following conditions: - Noise/squeal - Cosmetic corrosion - Routine pad replacement - Discoloration/hard spots Explanation of Brake Rotor Warranty Service Procedure ^ Rotor refacing during normal pad replacement is not necessary. ^ Rotor refacing for cosmetic corrosion is unnecessary. Clean up of braking surfaces can be accomplished by 10-15 moderate stops from 62-75 km/h (35-40 mph) with cooling time between stops. ^ Rotor service is ineffective in correcting brake squeal and/or premature lining wear out and should not be used to address these conditions unless specifically directed by a service bulletin. ^ When installing new rotors, DO NOT reface them. If a new rotor has more than .055 mm (.002 in) lateral runout when properly mounted on the hub, it may be machined using an approved on-car lathe or follow correction plate procedure found in Corporate Bulletin Number 01-05-23-001A. ^ Ensure bearing flanges and rotor mounting surfaces are free of corrosion when installing rotors to prevent inducing lateral runout. Use Kent Moore tool J 42450A to clean the corrosion around the wheel studs. ^ Always mark the position of the rotor on the hub before removal and reinstall the rotor in the same position. Rotors with perceived hard spots or discoloration should not be serviced. These conditions are normal. Installation of new rotors does not require pad replacement. Do not replace pads unless their condition requires it. It is not necessary to replace rotors in pairs. Rotors may be replaced individually. However, caution should be exercised, as a variance in surface finish may cause a brake pull condition. A torque limiting socket or torque wrench must be used to insure that the wheel nuts are tightened to specification. This should be done in 3 steps using the star pattern: 1. Hand tighten all 5 lug nuts using the star pattern. 2. Tighten all 5 nuts to approximately 1/2 spec. using the star pattern. 3. Tighten all 5 nuts to full spec. using the star pattern. ^ Never use lubricants or penetrating fluids on wheel studs, nuts or mounting surfaces. Wheel nuts, studs and mounting surfaces must be clean and dry. BRAKE SERVICE TECHNIQUES 1. Clean and lubricate all metal-to-metal contact points (i.e. caliper to knuckle, pad to knuckle, etc). 2. Clean and lubricate slide pins, if applicable. 3. Set correct clearances (i.e. caliper to knuckle, etc.), if applicable. 4. Clean rotor and hub mounting surfaces. Use Kent Moore tool J 42450 to clean around the wheel studs. 5. Verify lateral runout of the rotor with a dial indicator (rotor held on hub with 3 or more wheel nuts and washers). PULSATION IMPORTANT: Brake pulsation is often caused by factors outside customer control. Brake pulsation concerns may result from two basic conditions: ^ Pulsation is caused by brake rotor thickness variation. Thickness variation causes the piston in the brake caliper to "pump" in and out of the caliper housing. This "pumping" effect is transmitted hydraulically to the brake pedal. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Rotor/Disc > Component Information > Specifications > Page 8868 ^ Thickness variation on a new rotor will be virtually undetectable. But if the rotor (as installed on the vehicle) has lateral runout, it is likely that thickness variation will develop. Pulsation caused by thickness variation will develop on new vehicles when the tolerances of the hub and rotor stack up with lateral runout in excess of .055 mm (.002 in). Pulsation that is the result of excessive lateral runout usually develops in 4800-11300 km (3000-7000 mi). ^ Thickness variation can be induced when uneven torque is applied to wheel nuts (lug nuts). Improper wheel tightening after tire rotation, spare tire usage, brake inspection, etc. can be the cause of pulsation. Again, it usually takes 4800-11300 km (3000-7000 mi) after this event for the condition to surface. The owner or driver does not usually make the connection between the service event and the awareness of the pulsation. ^ The proper usage of torque wrenches and/or torque sticks (torque limiting sockets) will greatly reduce or eliminate the pulsation conditions after wheel service events. ^ The improper use of impact wrenches on wheel nuts greatly increases the likelihood of pulsation after wheel service. ^ GM highly recommends the use of on-car brake rotor turning as a method of eliminating the stack up of lateral runout which is a potential source of brake pulsation. GM has identified superior equipment through testing and evaluation. The *Pro-Cut PFM900 or Hunter 0CL360 will consistently deliver machined rotors that meet GM specifications (lateral runout less than .055 mm (.002 in) and are the only on-car brake lathes that are currently recommended by GM. The use of this on-car rotor turning technology has proven to significantly reduce the repeat occurrences of brake pulsation. If on-car brake rotor turning equipment is not available, refer to Corporate Bulletin Number 01-05-23-001A for brake rotor lateral runout correction procedure. * We believe these sources and their equipment to be reliable. There may be additional manufacturers of such equipment. General Motors does not endorse, indicate any preference for or assume any responsibility for the equipment from this firm or for any such items which may be available from other sources. The following are examples of pulsation conditions and reimbursement recommendations: 1. If a customer noticed the condition after 4800-11300 km (3000-7000 mi) and it gradually got worse, normally the repair would be covered. The customer may tolerate the condition until it becomes very apparent. 2. If a customer indicated they had wheel service, ask who performed the service. Then: ^ If a dealer performed the service, consider paying for the repair and then strongly reinforce the use of torque sticks at that dealer. Two common size torque sticks cover 90% of all GM products. Each technician needs to use torque sticks properly every time the wheel nuts are tightened. ^ If the customer had the wheel service done outside of our dealer network, normally GM would not otter any assistance. Customer assistance concerning brake pulsation and brake wear should always take into account the individual circumstances on a case by case basis. The recommendations mentioned previously should only be used as a general guide. REMEMBER THAT CUSTOMER SATISFACTION IS CRITICAL TO GM AND THAT OFTEN IT IS IN GM'S BEST INTEREST TO SATISFY AND EDUCATE THE CUSTOMER CONCERNING FUTURE BRAKE SERVICE. ROTOR GROOVING Excessive grooving can be caused by foreign material in contact with the rotor, but most often rotor grooving is the result of normal brake wear. Do not resurface rotors for light grooving. Resurface rotors only when grooves of 1.5 mm (0.060 in) or deeper are present. A dime may be used to determine disc brake groove depth. Place a dime in the groove, with Roosevelt's head toward the groove. If the dime goes into the groove beyond the top of his head, the groove exceeds 1.5 mm (0.060 in) and the rotor should be serviced. In Canada, if any portion of the letters of "Canada" are covered, the rotor should be serviced. If the groove is too narrow for the dime to be inserted, it is not a cause for concern. HIGH PEDAL EFFORT Follow the Service Manual diagnostic procedures for this condition. Service (replace or resurface) rotors if they have been recently resurfaced. The surface finish may be out-of-specification. LIGHTLY RUSTED ROTORS Light surface rust on rotor braking surfaces is often cosmetic and can be eliminated during a few normal driving stops. Rusting may occur when a vehicle is not driven for extended periods. Rotors with surface rust on unsold new cars can usually be burnished clean by performing 15 moderate stops from 62-75 km/h (35-40 mph) with cooling time between stops. FACTS ABOUT BRAKE NOISE Brake noise is normal and differences in loading, type of driving, or driving style can make a difference in brake wear on the same make and model. Depending on weather conditions, driving patterns and the local environment, brake noise may become more or less apparent. Brake noise is caused by a "slip stick" vibration of brake components. While intermittent brake noise may be normal, performing 3-4 aggressive stops may temporarily reduce or eliminate most brake squeal. If the noise persists, a brake dampening compound may be applied to the back of each pad. Use Permatex Disc Brake Quiet # 126hb, or equivalent. Also, clean and lubricate all metal-to-metal contact areas between pads, pad guides, caliper and knuckles with a thin layer of high temperature silicone grease. This allows parts to slide freely and not vibrate when moving relative to each other. The following noises are characteristic of all braking systems and are unavoidable. They may not indicate improper operation of the brake system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Rotor/Disc > Component Information > Specifications > Page 8869 SQUEAK/SQUEAL NOISE - Occurs with front semi-metallic brake pads at medium speeds when light to medium pressure is applied to the brake pedal. - Occasionally a noise may occur on rear brakes during the first few stops or with cold brakes and/or high humidity. GRINDING NOISE - Common to rear brakes and some front disc brakes during initial stops after the vehicle has been parked overnight. - Caused by trace corrosion on the metal surfaces during vehicle non-use. Usually disappears after a few stops. GROAN NOISE - A small groan may be heard when stopping quickly or moving forward slowly from a complete stop. This is normal. BRAKE WEAR Several factors impact brake lining wear and should be taken into account when reviewing related issues. The following are conditions that may accelerate brake lining wear: - Heavy loads - High temperatures - Towing - Mountainous terrain - City Driving - Aggressive driving - Driver braking characteristics (left foot) The following are conditions that may extend brake lining wear: - Light loads - Highway driving - Conservative driving - Level terrain Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Rotor/Disc > Component Information > Service and Repair > Brake Rotor Diagnosis and Service Guidelines Brake Rotor/Disc: Service and Repair Brake Rotor Diagnosis and Service Guidelines This article has been updated with bulletin No: 00-05-22-002B. BRAKE ROTOR DIAGNOSIS AND SERVICE GUIDELINES IMPORTANT: Certain conditions may apply to individual vehicles regarding specific repairs which differ from those outlined in this bulletin. For information regarding lateral runout correction, refer to Bulletin Number 01-05-23-001A, Brake Align System for Brake Rotor Lateral Runout Correction. For other conditions, refer to those specific repairs in applicable bulletins. Original equipment rotor surfaces are ground to ensure smooth finish and parallelism between mounting and friction surfaces. New rotors SHOULD NOT be resurfaced before installation. When rotor turning is necessary, it is essential that you use a high quality brake lathe. Rotors, when remounted on the hub, should have less than .055 mm (.002 in) lateral runout. Brake rotors should only be turned when one of the following rotor surface conditions exist: 1. Severe scoring - depth in excess of 1.5 mm (0.060 in). 2. Pulsation concerns from: ^ Lateral runout in excess of .055 mm (.002 in). ^ Thickness variation in excess of 0.025 mm (0.001 in). ^ Excessive corrosion on rotor braking surfaces. Rotors are not to be resurfaced in an attempt to correct the following conditions: - Noise/squeal - Cosmetic corrosion - Routine pad replacement - Discoloration/hard spots Explanation of Brake Rotor Warranty Service Procedure ^ Rotor refacing during normal pad replacement is not necessary. ^ Rotor refacing for cosmetic corrosion is unnecessary. Clean up of braking surfaces can be accomplished by 10-15 moderate stops from 62-75 km/h (35-40 mph) with cooling time between stops. ^ Rotor service is ineffective in correcting brake squeal and/or premature lining wear out and should not be used to address these conditions unless specifically directed by a service bulletin. ^ When installing new rotors, DO NOT reface them. If a new rotor has more than .055 mm (.002 in) lateral runout when properly mounted on the hub, it may be machined using an approved on-car lathe or follow correction plate procedure found in Corporate Bulletin Number 01-05-23-001A. ^ Ensure bearing flanges and rotor mounting surfaces are free of corrosion when installing rotors to prevent inducing lateral runout. Use Kent Moore tool J 42450A to clean the corrosion around the wheel studs. ^ Always mark the position of the rotor on the hub before removal and reinstall the rotor in the same position. Rotors with perceived hard spots or discoloration should not be serviced. These conditions are normal. Installation of new rotors does not require pad replacement. Do not replace pads unless their condition requires it. It is not necessary to replace rotors in pairs. Rotors may be replaced individually. However, caution should be exercised, as a variance in surface finish may cause a brake pull condition. A torque limiting socket or torque wrench must be used to insure that the wheel nuts are tightened to specification. This should be done in 3 steps using the star pattern: 1. Hand tighten all 5 lug nuts using the star pattern. 2. Tighten all 5 nuts to approximately 1/2 spec. using the star pattern. 3. Tighten all 5 nuts to full spec. using the star pattern. ^ Never use lubricants or penetrating fluids on wheel studs, nuts or mounting surfaces. Wheel nuts, studs and mounting surfaces must be clean and dry. BRAKE SERVICE TECHNIQUES 1. Clean and lubricate all metal-to-metal contact points (i.e. caliper to knuckle, pad to knuckle, etc). 2. Clean and lubricate slide pins, if applicable. 3. Set correct clearances (i.e. caliper to knuckle, etc.), if applicable. 4. Clean rotor and hub mounting surfaces. Use Kent Moore tool J 42450 to clean around the wheel studs. 5. Verify lateral runout of the rotor with a dial indicator (rotor held on hub with 3 or more wheel nuts and washers). PULSATION IMPORTANT: Brake pulsation is often caused by factors outside customer control. Brake pulsation concerns may result from two basic conditions: ^ Pulsation is caused by brake rotor thickness variation. Thickness variation causes the piston in the brake caliper to "pump" in and out of the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Rotor/Disc > Component Information > Service and Repair > Brake Rotor Diagnosis and Service Guidelines > Page 8872 caliper housing. This "pumping" effect is transmitted hydraulically to the brake pedal. ^ Thickness variation on a new rotor will be virtually undetectable. But if the rotor (as installed on the vehicle) has lateral runout, it is likely that thickness variation will develop. Pulsation caused by thickness variation will develop on new vehicles when the tolerances of the hub and rotor stack up with lateral runout in excess of .055 mm (.002 in). Pulsation that is the result of excessive lateral runout usually develops in 4800-11300 km (3000-7000 mi). ^ Thickness variation can be induced when uneven torque is applied to wheel nuts (lug nuts). Improper wheel tightening after tire rotation, spare tire usage, brake inspection, etc. can be the cause of pulsation. Again, it usually takes 4800-11300 km (3000-7000 mi) after this event for the condition to surface. The owner or driver does not usually make the connection between the service event and the awareness of the pulsation. ^ The proper usage of torque wrenches and/or torque sticks (torque limiting sockets) will greatly reduce or eliminate the pulsation conditions after wheel service events. ^ The improper use of impact wrenches on wheel nuts greatly increases the likelihood of pulsation after wheel service. ^ GM highly recommends the use of on-car brake rotor turning as a method of eliminating the stack up of lateral runout which is a potential source of brake pulsation. GM has identified superior equipment through testing and evaluation. The *Pro-Cut PFM900 or Hunter 0CL360 will consistently deliver machined rotors that meet GM specifications (lateral runout less than .055 mm (.002 in) and are the only on-car brake lathes that are currently recommended by GM. The use of this on-car rotor turning technology has proven to significantly reduce the repeat occurrences of brake pulsation. If on-car brake rotor turning equipment is not available, refer to Corporate Bulletin Number 01-05-23-001A for brake rotor lateral runout correction procedure. * We believe these sources and their equipment to be reliable. There may be additional manufacturers of such equipment. General Motors does not endorse, indicate any preference for or assume any responsibility for the equipment from this firm or for any such items which may be available from other sources. The following are examples of pulsation conditions and reimbursement recommendations: 1. If a customer noticed the condition after 4800-11300 km (3000-7000 mi) and it gradually got worse, normally the repair would be covered. The customer may tolerate the condition until it becomes very apparent. 2. If a customer indicated they had wheel service, ask who performed the service. Then: ^ If a dealer performed the service, consider paying for the repair and then strongly reinforce the use of torque sticks at that dealer. Two common size torque sticks cover 90% of all GM products. Each technician needs to use torque sticks properly every time the wheel nuts are tightened. ^ If the customer had the wheel service done outside of our dealer network, normally GM would not otter any assistance. Customer assistance concerning brake pulsation and brake wear should always take into account the individual circumstances on a case by case basis. The recommendations mentioned previously should only be used as a general guide. REMEMBER THAT CUSTOMER SATISFACTION IS CRITICAL TO GM AND THAT OFTEN IT IS IN GM'S BEST INTEREST TO SATISFY AND EDUCATE THE CUSTOMER CONCERNING FUTURE BRAKE SERVICE. ROTOR GROOVING Excessive grooving can be caused by foreign material in contact with the rotor, but most often rotor grooving is the result of normal brake wear. Do not resurface rotors for light grooving. Resurface rotors only when grooves of 1.5 mm (0.060 in) or deeper are present. A dime may be used to determine disc brake groove depth. Place a dime in the groove, with Roosevelt's head toward the groove. If the dime goes into the groove beyond the top of his head, the groove exceeds 1.5 mm (0.060 in) and the rotor should be serviced. In Canada, if any portion of the letters of "Canada" are covered, the rotor should be serviced. If the groove is too narrow for the dime to be inserted, it is not a cause for concern. HIGH PEDAL EFFORT Follow the Service Manual diagnostic procedures for this condition. Service (replace or resurface) rotors if they have been recently resurfaced. The surface finish may be out-of-specification. LIGHTLY RUSTED ROTORS Light surface rust on rotor braking surfaces is often cosmetic and can be eliminated during a few normal driving stops. Rusting may occur when a vehicle is not driven for extended periods. Rotors with surface rust on unsold new cars can usually be burnished clean by performing 15 moderate stops from 62-75 km/h (35-40 mph) with cooling time between stops. FACTS ABOUT BRAKE NOISE Brake noise is normal and differences in loading, type of driving, or driving style can make a difference in brake wear on the same make and model. Depending on weather conditions, driving patterns and the local environment, brake noise may become more or less apparent. Brake noise is caused by a "slip stick" vibration of brake components. While intermittent brake noise may be normal, performing 3-4 aggressive stops may temporarily reduce or eliminate most brake squeal. If the noise persists, a brake dampening compound may be applied to the back of each pad. Use Permatex Disc Brake Quiet # 126hb, or equivalent. Also, clean and lubricate all metal-to-metal contact areas between pads, pad guides, caliper and knuckles with a thin layer of high temperature silicone grease. This allows parts to slide freely and not vibrate when moving relative to each other. The following noises are characteristic of all braking systems and are unavoidable. They may not indicate improper operation of the brake system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Rotor/Disc > Component Information > Service and Repair > Brake Rotor Diagnosis and Service Guidelines > Page 8873 SQUEAK/SQUEAL NOISE - Occurs with front semi-metallic brake pads at medium speeds when light to medium pressure is applied to the brake pedal. - Occasionally a noise may occur on rear brakes during the first few stops or with cold brakes and/or high humidity. GRINDING NOISE - Common to rear brakes and some front disc brakes during initial stops after the vehicle has been parked overnight. - Caused by trace corrosion on the metal surfaces during vehicle non-use. Usually disappears after a few stops. GROAN NOISE - A small groan may be heard when stopping quickly or moving forward slowly from a complete stop. This is normal. BRAKE WEAR Several factors impact brake lining wear and should be taken into account when reviewing related issues. The following are conditions that may accelerate brake lining wear: - Heavy loads - High temperatures - Towing - Mountainous terrain - City Driving - Aggressive driving - Driver braking characteristics (left foot) The following are conditions that may extend brake lining wear: - Light loads - Highway driving - Conservative driving - Level terrain Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Rotor/Disc > Component Information > Service and Repair > Brake Rotor Diagnosis and Service Guidelines > Page 8874 Brake Rotor/Disc: Service and Repair Service Notes Servicing of disc brakes is extremely critical due to the close tolerances required in machining the brake disc to insure proper brake operation. The maintenance of these close controls on the friction surfaces is necessary to prevent brake roughness. In addition, the surface finish must be non-directional and maintained at a micro-inch finish. This close control of the rubbing surface finish is necessary to avoid pulls and erratic performance and promote long lining life and equal lining wear of both left and right brakes. In light of the foregoing remarks, refinishing of the rubbing surfaces should not be attempted unless precision equipment, capable of measuring in micro-inches is available. To check runout of a disc, mount a dial indicator on a convenient part (steering knuckle, tie rod, disc brake caliper housing) so that the plunger of the dial indicator contacts the disc at a point one inch from the outer edge. If the total indicated runout exceeds specifications, install a new disc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Rotor/Disc > Component Information > Service and Repair > Brake Rotor Diagnosis and Service Guidelines > Page 8875 Brake Rotor/Disc: Service and Repair Front Fig. 5 Hub, knuckle & bearing components. REMOVE 1. Disconnect battery ground cable. 2. Raise and support vehicle, then remove brake caliper. 3. Remove cap from hub/disc assembly, Fig. 5. 4. Remove cotter pin, nut and washer. 5. Remove hub/disc from spindle. 6. Remove outer bearing, seal, inner bearing and cup. INSTALL 1. Reverse procedure to install. Note the following: a. Clean all components before installing. b. Apply an approved high temperature front wheel bearing grease to the spindle at the inner and outer bearing seat, shoulder and seal seat. Also finger apply a small amount of grease inboard of each bearing cup in the hub/disc assembly. Pressure pack the bearings with a grease machine or hand pack them. Ensure grease is worked thoroughly into the rollers, cone and cage. c. When installing inner bearing, apply an additional quantity of grease outboard of the inner bearing. d. Torque nut (12) 10-12 ft lbs while turning the wheel assembly forward by hand. Apply grease to the outboard side of the outer bearing. Adjust wheel bearings. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Disc Brake System > Brake Rotor/Disc > Component Information > Service and Repair > Brake Rotor Diagnosis and Service Guidelines > Page 8876 Brake Rotor/Disc: Service and Repair Rear BENDIX SINGLE PISTON SLIDING CALIPER Fig. 9 Rear Disc Brake Rotor Replacement. 1. Raise and support vehicle. 2. Remove tire and wheel. 3. Remove caliper. 4. Remove axle cap bolts from hub/rotor, then axle shaft. 5. Remove axle outer lock nut using tool No. J-2222-C, or equivalent, then remove washer and adjustor nut. 6. Remove hub/rotor from spindle, being careful not to damage spindle threads or outer bearing, Fig. 9. 7. Reverse procedure to install noting the following: a. Inspect and replace all parts and apply high-temperature wheel bearing grease where necessary. b. Torque inner wheel bearing adjusting nut to 50 ft. lbs. to seat bearings, then back of adjusting nut to 35 ft. lbs. while rotating hub and finally back off 135-150 degrees. Final bearing adjustment is 0.001-0.010 inch. c. Bend one ear of lock washer over inner nut to 30 degrees minimum, then bend one ear of lockwasher over outer nut 60 degrees minimum. d. Torque retaining nut to 65 ft. lbs. while turning wheel assembly forward by hand and making certain the bearing cones are seated and in contact with the spindle shoulder. e. Tighten axle cap nuts to specifications. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Drum Brake System > Backing Plate > Component Information > Testing and Inspection Backing Plate: Testing and Inspection Inspect backing plate shoe contact surface for grooves that may restrict shoe movement and cannot be removed by lightly sanding with emery cloth or other suitable abrasive. If backing plate exhibits above condition, it should be replaced. Also inspect for signs of cracks, warpage and excessive rust, indicating need for replacement. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Drum Brake System > Brake Drum > Component Information > Specifications Brake Drum: Specifications GVW 4300, 6400 lbs. GVW 7200 lbs. GVW 8400 lbs. Model C/K C/K C/K Engine Type All All All Power Assist Type All All All Drum Brake Diameter Original 10 in 11.15 in 13 in Maximum Refinish 10.05 in 11.21 in 13.06 in Discard 10.09 in 11.24 in 13.09 in Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Drum Brake System > Brake Drum > Component Information > Specifications > Page 8884 Brake Drum: Testing and Inspection Any time the brake drums are removed for brake service, the braking surface diameter should be checked with a suitable brake drum micrometer at several points to determine if they are within the safe oversize limit stamped on the brake drum outer surface. If the braking surface diameter exceeds specifications, the drum must be replaced. If the braking surface diameter is within specifications, drums should be cleaned and inspected for cracks, scores, deep grooves, taper, out of round and heat spotting. If drums are cracked or heat spotted, they must be replaced. Grooves and large scores can only be removed by machining with special equipment, as long as the braking surface is within specifications stamped on brake drum outer surface. Any brake drum sufficiently out of round to cause vehicle vibration or noise while braking, or showing taper should also be machined, removing only enough stock to true up the brake drum. After a brake drum is machined, wipe the braking surface diameter with a cloth soaked in denatured alcohol. Brake drums should always be machined in pairs and within allowable side to side specifications to maintain equal braking forces. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Drum Brake System > Brake Shoe > Component Information > Technical Service Bulletins > Customer Interest for Brake Shoe: > 99-05-24-001A > Sep > 99 > Brakes - Lead/Pull & Front Brake Wear Brake Shoe: Customer Interest Brakes - Lead/Pull & Front Brake Wear File In Section: 05 - Brakes Bulletin No.: 99-05-24-001A Date: September, 1999 TECHNICAL Subject: Brake Lead/Pull and Front Brake Wear (Replace Front Brake Pads and/or Rear Brake Shoes) Models: 1992-99 Chevrolet and GMC C/K Cab Chassis, Crew Cab, and Pickup Models with Power Brakes (RPO JB8) 1992-99 Chevrolet and GMC C/K Suburban Models with 8600 # GVW (RPO C6P) 1996-2000 Chevrolet and GMC G Vans with Power Brakes (RPO JD7 & JB8) and GVW's of 7,700 # up to 9,500 # (RPO's C3F, C6P, & E23) This bulletin is being revised to update information in the Models Section and Correction Information. Please discard Corporate Bulletin Number 99-05-24-001 (Section 5 - Brakes). Condition Some owners may comment about the vehicle leading or pulling to either side while applying the brakes, and premature front brake wear, especially vehicles that have been used to tow a heavy load. Cause The condition may be caused by wearing of the front brake material. Improvements to the above conditions can be gained through brake material modifications. On the Suburban models, the best performance from this new brake material can be achieved with replacing the brake combination valve. Correction Replace the rear brake shoes with P/N 18029651. THIS FIX DOES NOT APPLY TO THE 13 x 2-1/2 BRAKE, DURASTOP(TM) P/N 18029650, OR ANY OTHER SIZE. On Suburban models, a brake combination valve must be replaced. ALL OTHER MODELS (C/K, G Van), NO BRAKE COMBINATION VALVE CHANGE IS REQUIRED. Refer to the Drum Brakes or Hydraulic Brakes subsection of the appropriate Service Manual. For G2/G3 Series Vans only (with GVW's of 7,700 # up to 9,500 # - RPOs C3F, C6P, E23) also replace the front brakes pads with P/N 12471685. Refer to the Disc Brake subsection of the appropriate Service Manual. Important: The new front brake pad material has been selected for improved wear characteristics. Some customers may experience increased brake noise from this brake pad and should be advised that some squeal is a characteristic of this particular material. Important: If you encounter disc brakes that are extremely worn on the inboard side, with very little wear to the outboard side, verify the clearance between the caliper and the steering knuckle bracket stops. MEASURE THE CLEARANCES INDIVIDUALLY AND ADD THE CLEARANCES TOGETHER FOR TOTAL CLEARANCE BEFORE REMOVING THE CALIPER. If the caliper (total clearance) to the steering knuckle stops is under 0.26 mm (0.010 in), correct this by filing metal off at the steering knuckle stops in order to obtain a total clearance of 0.26 to 0.60 mm (0.010 to 0.024 in). DO NOT FILE METAL OFF OF THE CALIPER. Refer to the Disc Brake subsection of the appropriate Service Manual for additional information on this procedure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Drum Brake System > Brake Shoe > Component Information > Technical Service Bulletins > Customer Interest for Brake Shoe: > 99-05-24-001A > Sep > 99 > Brakes - Lead/Pull & Front Brake Wear > Page 8893 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Drum Brake System > Brake Shoe > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Brake Shoe: > 99-05-24-001A > Sep > 99 > Brakes Lead/Pull & Front Brake Wear Brake Shoe: All Technical Service Bulletins Brakes - Lead/Pull & Front Brake Wear File In Section: 05 - Brakes Bulletin No.: 99-05-24-001A Date: September, 1999 TECHNICAL Subject: Brake Lead/Pull and Front Brake Wear (Replace Front Brake Pads and/or Rear Brake Shoes) Models: 1992-99 Chevrolet and GMC C/K Cab Chassis, Crew Cab, and Pickup Models with Power Brakes (RPO JB8) 1992-99 Chevrolet and GMC C/K Suburban Models with 8600 # GVW (RPO C6P) 1996-2000 Chevrolet and GMC G Vans with Power Brakes (RPO JD7 & JB8) and GVW's of 7,700 # up to 9,500 # (RPO's C3F, C6P, & E23) This bulletin is being revised to update information in the Models Section and Correction Information. Please discard Corporate Bulletin Number 99-05-24-001 (Section 5 - Brakes). Condition Some owners may comment about the vehicle leading or pulling to either side while applying the brakes, and premature front brake wear, especially vehicles that have been used to tow a heavy load. Cause The condition may be caused by wearing of the front brake material. Improvements to the above conditions can be gained through brake material modifications. On the Suburban models, the best performance from this new brake material can be achieved with replacing the brake combination valve. Correction Replace the rear brake shoes with P/N 18029651. THIS FIX DOES NOT APPLY TO THE 13 x 2-1/2 BRAKE, DURASTOP(TM) P/N 18029650, OR ANY OTHER SIZE. On Suburban models, a brake combination valve must be replaced. ALL OTHER MODELS (C/K, G Van), NO BRAKE COMBINATION VALVE CHANGE IS REQUIRED. Refer to the Drum Brakes or Hydraulic Brakes subsection of the appropriate Service Manual. For G2/G3 Series Vans only (with GVW's of 7,700 # up to 9,500 # - RPOs C3F, C6P, E23) also replace the front brakes pads with P/N 12471685. Refer to the Disc Brake subsection of the appropriate Service Manual. Important: The new front brake pad material has been selected for improved wear characteristics. Some customers may experience increased brake noise from this brake pad and should be advised that some squeal is a characteristic of this particular material. Important: If you encounter disc brakes that are extremely worn on the inboard side, with very little wear to the outboard side, verify the clearance between the caliper and the steering knuckle bracket stops. MEASURE THE CLEARANCES INDIVIDUALLY AND ADD THE CLEARANCES TOGETHER FOR TOTAL CLEARANCE BEFORE REMOVING THE CALIPER. If the caliper (total clearance) to the steering knuckle stops is under 0.26 mm (0.010 in), correct this by filing metal off at the steering knuckle stops in order to obtain a total clearance of 0.26 to 0.60 mm (0.010 to 0.024 in). DO NOT FILE METAL OFF OF THE CALIPER. Refer to the Disc Brake subsection of the appropriate Service Manual for additional information on this procedure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Drum Brake System > Brake Shoe > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Brake Shoe: > 99-05-24-001A > Sep > 99 > Brakes Lead/Pull & Front Brake Wear > Page 8899 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Drum Brake System > Brake Shoe > Component Information > Technical Service Bulletins > Page 8900 Brake Shoe: Testing and Inspection Inspect brake linings for excessive wear, damage, oil, grease or brake fluid contamination. If any of the above conditions exists, brake linings should be replaced. Brake shoes should always be replaced as an axle set to maintain equal braking forces. Examine brake shoe webbing, hold-down and return springs for signs of overheating indicated by a slight blue color. If any component exhibits signs of overheating, replace hold-down and return springs with new ones. Overheated springs lose their pull and could cause brake linings to wear out prematurely. Inspect all springs for sags, bends and external damage, and replace as necessary. Inspect hold-down retainers and pins for bends, rust and corrosion. If any of the above conditions exist, replace retainers and pins. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Drum Brake System > Brake Shoe > Component Information > Technical Service Bulletins > Page 8901 Brake Shoe: Adjustments These brakes have self-adjusting shoe mechanisms that assure correct lining-to-drum clearances at all times. The automatic adjusters operate only when the brakes are applied as the vehicle is moving rearward or when the car comes to an uphill stop. Although the brakes are self-adjusting, an initial adjustment is necessary after the brake shoes have been relined or replaced, or when the length of the adjusting screw has been changed during some other service operation. Refer to COMPONENT REPLACEMENT AND REPAIR/DRUM BRAKES/REMOVAL/INSTALLATION for this procedure. Frequent usage of an automatic transmission forward range to halt reverse vehicle motion may prevent the automatic adjusters from functioning, thereby inducing low pedal heights. Should low pedal heights be encountered, it is recommended that numerous forward and reverse stops be made until satisfactory pedal height is obtained. If a low pedal condition cannot be corrected by making numerous reverse stops (provided the hydraulic system is free of air) it indicates that the self-adjusting mechanism is not functioning. Therefore it will be necessary to remove the brake drum, clean, free up and lubricate the adjusting mechanism. Then adjust the brakes, being sure the parking brake is fully released. 1. Using a suitable punch, knock out lanced area in backing plate or drum. If drum is installed on vehicle when this is done, remove drum and clean brake compartment of all metal. When adjustment is completed, a new hole cover must be installed in the backing plate. 2. Using suitable tool, turn brake adjusting screw to expand brake shoes at each wheel until wheel can just be turned by hand. Drag should be equal on all wheels. 3. Back off adjusting screw at each wheel 30 notches. 4. If shoe still drags slightly on drum, back off adjusting screw an additional one or two notches. 5. When adjusting screw has been backed off approximately 12 notches, brakes should be free of drag. Heavy drag at this point indicates tight parking brake cables. 6. Install adjusting hole cover in brake backing place. 7. Check parking brake for proper adjustment. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Drum Brake System > Wheel Cylinder > Component Information > Technical Service Bulletins > Brakes - Wheel Cylinder Inspection Guidelines Wheel Cylinder: Technical Service Bulletins Brakes - Wheel Cylinder Inspection Guidelines Bulletin No.: 03-05-24-001A Date: March 21, 2005 INFORMATION Subject: Service Information Regarding Rear Brake Drum Wheel Cylinder Inspections Models: 2005 and Prior GM Passenger Cars and Trucks 2005 and Prior Saturn Vehicles with Rear Drum Brakes Supercede: This bulletin is being revised add model years and include all GM vehicles. Please discard Corporate Bulletin Number 03-05-24-001 (Section 03 - Suspension). This bulletin provides information on proper inspection of rear drum brake wheel cylinders. Important: It is not recommended that dust boots be removed during inspection processes as dirt and debris could contaminate the wheel cylinder bore causing premature wear of the wheel cylinder. In addition, most bores should look damp and some lubricant may drip out from under the boot as a result of lubricant being present. All rear drum brake wheel cylinders are assembled with a lubricant to aid in assembly, provide an anti-corrosion coating to the cylinder bore, and lubricate internal rubber components. As a result of this lubrication process, it is not uncommon for some amount of lubricant to accumulate at the ends of the cylinder under the dust boot. Over time, the lubricant may work its way to the outside of the boot and cause an area of the boot to look damp. Evidence of a damp area on the boot does not indicate a leak in the cylinder. However, if there is excessive wetness (i.e. drips) coming from the boot area of the wheel cylinder, it could indicate a brake hydraulic fluid leak requiring wheel cylinder replacement. (Refer to the Wheel Cylinder Replacement procedures in the appropriate Service Manual.) Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Drum Brake System > Wheel Cylinder > Component Information > Technical Service Bulletins > Page 8906 Wheel Cylinder: Service and Repair Disassembled View Of Wheel Cylinder (typical) 1. Raise and support vehicle. 2. Remove wheel, drum and brake shoes. 3. Disconnect hydraulic line at wheel cylinder. 4. Remove wheel cylinder attaching screws, then remove wheel cylinder. 5. Strip cylinder of boots, pistons, springs and seals, Fig. 9. 6. Inspect cylinder bore for scoring and corrosion. Discoloration is a sign that springs have been damaged by heat, replace them if necessary. 7. Clean cylinder bore with crocus cloth. If cleaning does not remove scoring, replace cylinder. 8. Lubricate cylinder bore and seals with brake fluid, then reassemble cylinder. 9. Reverse procedure to install. Bleed system. Refer to Brakes / Service and Repair / Brake System Bleed. See: Service and Repair Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Bleeding > System Information > Service and Repair > Four Wheel Anitlock Brake System Brake Bleeding: Service and Repair Four Wheel Anitlock Brake System Two Person Procedure (Preferred) BLEEDING PROCEDURES Important: Never pump the brake pedal. Fluid cavitation may occur. NOTICE: Gravity and vacuum bleeding are not recommended for this ABS system. Two Person Procedure (Preferred) 1. Raise the vehicle to gain access to the system bleed screws. Install clear tubing on the bleed screws so that air bubbles in the fluid can be seen. 2. Begin by bleeding the system at the right rear wheel, then the left rear, right front and left front. 3. Open one bleed screw at a time 1/2 to 1 full turn. 4. Slowly depress the brake pedal until it reaches its full travel and hold until the bleed screw has been tightened. Release the brake pedal and wait 10-15 seconds for the master cylinder to return to the home position. Important: Repeat steps 1 through 4 until approximately 1 pint of brake fluid has been bled from each wheel. Clean brake fluid should be present at each of the wheel bleed screws. Check the master cylinder fluid level every 4 to 6 strokes of the brake pedal to avoid running the system dry. 5. If any component is replaced which may have caused air to enter the BPMV, use a Scan Tool to run "Function Test" four times while applying the brake pedal firmly. Important: Set the park brake when running the "Function Test." 6. Rebleed all four wheels using steps 1 through 4 to remove the remaining air from the brake system. 7. Evaluate the brake pedal feel before attempting to drive the vehicle and rebleed as many times as necessary to obtain appropriate pedal feel. Pressure Bleeding (Low Pressure) Pressure Bleeding (Low Pressure) 1. Install pressure bleeder per instructions. 2. Install combination valve depressing tool J391 77 if the vehicle is equipped with the metering portion of the combination valve. Remove both dust caps on the combination valve. Install the tool on the end of the combination valve with a brass center pin. 3. Bleed all four wheels beginning at the right rear wheel, then the left rear, right front and left front. Leave the bleed screws open until 1 pint of fluid has been bled out of each wheel. 4. After bleeding all four wheels1 remove the combination valve clip. Use a Scan Tool to run 4 functional tests while applying the brake pedal firmly. 5. Repeat steps 1 through 3 then evaluate the pedal feel. 6. Rebleed the wheels as many times as necessary to obtain good pedal feel before attempting to drive the vehicle. A good bleed will use approximately 2 to 3 quarts of brake fluid. Important: Never reuse brake fluid after it has been bled through a brake system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Bleeding > System Information > Service and Repair > Four Wheel Anitlock Brake System > Page 8912 Brake Bleeding: Service and Repair Master Cylinder Bleeding This procedure can be performed with master cylinder on or off vehicle. 1. Disconnect brake lines at master cylinder, if necessary. 2. Connect suitable lengths of brake lines to master cylinder and immerse other ends of lines in master cylinder reservoirs. 3. Apply master cylinder pushrod or brake pedal with full strokes until air bubbles have disappeared in reservoirs. It may require 20-30 applications to fully eliminate air bubbles. 4. Remove bleeding lines from master cylinder, then install master cylinder on vehicle, if necessary, and connect brake lines. It is not necessary to bleed entire hydraulic system after replacing master cylinder, providing master cylinder has been bled and filled during installation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Bleeding > System Information > Service and Repair > Four Wheel Anitlock Brake System > Page 8913 Brake Bleeding: Service and Repair Bleeding Brake Hydraulic System Pressure Bleeding Pressure Bleeding A diaphragm type pressure bleeder must be used. It must have a rubber diaphragm between the air supply and brake fluid to prevent air, moisture, oil, and other contaminants from entering the hydraulic system. NOTICE: Brake fluid can damage electrical connections and painted surfaces. Use shop cloths, suitable containers, and fender covers to prevent brake fluid from contacting these areas. Always re-seal and wipe off brake fluid containers to prevent spills. Tools Required: Brake Bleeder Adapter J 28434 Wheel Cylinder Bleeder Wrench 1. Fill the pressure tank at least 2,3 full of brake fluid. The bleeder must be bled each time fluid is added. 2. Charge the bleeder to 140 - 170 kPa ( 20-25 psi ). 3. Install the bleeder adapter. 4. If the BPMV of the 4WAL system is replaced or suspected to have air trapped inside, it must be bled next. 5. Bleed each wheel in the following sequence: A. Right rear. B. Left rear. C. Right front. D. Left front. 6. Connect the hose from the bleeder to the adapter at the master cylinder. 7. Open the tank valve. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Bleeding > System Information > Service and Repair > Four Wheel Anitlock Brake System > Page 8914 8. Attach a hose to the bleeder valve. ^ Immerse the opposite end of the hose into a container partially filled with clean brake fluid. 9. Open the bleeder valve at least 3/4 of a turn and allow the fluid to flow until no air is seen in the fluid. 10. Tighten the bleeder valve to 13 Nm ( 110 lb. in. ). 11. Repeat Steps 9 through 11 at all wheels. 12. Check the brake pedal for "sponginess." ^ Repeat the entire bleeding procedure if this condition is found. 13. Disconnect the hose from the bleeder adapter. 14. Remove the bleeder adapter. 15. Fill the master cylinder to the proper level. Manual Bleeding BLEEDING BRAKE HYDRAULIC SYSTEM Bleeding is necessary if air has entered the hydraulic brake system. It may be necessary to bleed the system at all four wheels if a low fluid level allowed the air to enter the system or the brake pipes have been disconnected at the master cylinder or combination valve. If a pipe is disconnected at one wheel, then bleed only that wheel. The time required to bleed the hydraulic system when the master cylinder is removed can be reduced by bench bleeding the master cylinder before installing it on the vehicle. Manual Bleeding If the vehicle is equipped with a vacuum booster, relieve the vacuum reserve by applying the brakes several times with the engine off. NOTICE: Brake fluid will damage electrical connections and painted surfaces. Use shop cloths, suitable containers, and fender covers to prevent the brake fluid from contacting these areas. Always re-seal and wipe off brake fluid containers to prevent spills. Tools Required: J 28434 Wheel Cylinder Bleeder Wrench 1. Fill the master cylinder reservoir with Delco Supreme 11® Hydraulic Brake Fluid GM P/N 1052535 or an equivalent DOT 3 motor vehicle brake fluid. ^ Maintain the fluid level during bleeding. 2. If the master cylinder is suspected to have air in the bore, bleed it before any wheel cylinder or caliper. A. Disconnect the forward brake pipe connection at the master cylinder. B. Allow the brake fluid to flow from the connector port. C. Connect the brake pipe but do not tighten. D. Slowly apply the brake pedal and allow the air to bleed from the loose fitting. E. Tighten the fitting before releasing the pedal. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Bleeding > System Information > Service and Repair > Four Wheel Anitlock Brake System > Page 8915 F. Wait 15 seconds. G. Repeat this sequence, including the 1 5-second wait, until all air is purged from the bore. H. After all air has been removed from the forward connection, repeat this procedure for the rear pipe. 3. If the BPMV of the 4WAL system is replaced or suspected to have air trapped inside, it must be bled next. 4. Bleed each wheel in the following sequence: A. Right rear. B. Left rear. C. Right front D. Left front 5. Attach a hose to the wheel cylinder/caliper bleeder valve. ^ Immerse the opposite end of the hose into a container partially filled with clean brake fluid. 6. Slowly apply the brake pedal one time and hold. 7. Loosen the bleeder valve to purge the air from the wheel cylinder/caliper. 8. Tighten the bleeder valve to 13 Nm ( 110 lb. in. ) and slowly release the pedal. 9. Wait 15 seconds. 10. Repeat this sequence, including the 15-second wait until all air is purged from the wheel cylinder/caliper. 11. Repeat steps 5 through 10 at each wheel until the system is bled. 12. Check the brake pedal for "sponginess" and the brake warning lamp for an indication of unbalanced pressure. Repeat the bleeding procedure to correct either of these conditions. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Specifications > Bendix Single Piston Sliding Caliper Brake Caliper: Specifications Bleeder Valve 9.5 ft.lb Brake Hose To Caliper Bolt 33 ft.lb Caliper Mounting Bolt 28 ft.lb Caliper Support Key Bolt 15 ft.lb Rear Caliper Anchor Plate To Axle 177 ft.lb Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Specifications > Bendix Single Piston Sliding Caliper > Page 8920 Brake Caliper: Specifications Bleeder Valve (Delco) 5 ft.lb Bleeder Valve (Bendix) 9.5 ft.lb Brake Hose To Caliper Bolt 33 ft.lb Caliper Mounting Bolt 38 ft.lb Caliper Support Key Bolt 15 ft.lb Rear Brake Anchor Pin Vehicles w/ gross vehicle weight of 7200 lbs., 147 ft. lbs. Vehicles at or above gross vehicle weight of 8400 lbs., 228 ft. lbs. Rear Caliper Anchor Plate To Axle 177 ft.lb Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Description and Operation > Bendix Single Piston Sliding Caliper Brake Caliper: Description and Operation Bendix Single Piston Sliding Caliper Fig. 1 Disc Brake Assembly The Bendix single piston sliding caliper disc brake is standard equipment on some truck applications, while on other trucks it is used only in Hydro-Boost power brake applications with both front disc brakes and 4 wheel disc brakes. On 4 wheel disc brakes, the front and rear systems are identical. The sliding caliper attaches to and slides on the steering knuckle. The caliper assembly is held in place with a support key and spring Fig. 1. A screw prevents the key from sliding on the steering knuckle. The friction material is bonded with rivets. The inboard and outboard brake pads are not interchangeable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Description and Operation > Bendix Single Piston Sliding Caliper > Page 8923 Brake Caliper: Description and Operation Delco-Moraine Single Piston Caliper With Delco-Moraine 3400 Caliper Fig. 2 Exploded View Of Disc Brake Caliper Assembly. The caliper assembly slides on its mounting surfaces, Fig. 2. Upon brake application, hydraulic pressure against the piston forces the inboard pad against the inboard side of the disc. This action causes the caliper assembly to slide until the outboard pad comes into contact with the disc, which in turn creates a slowing or stopping action. With Delco-Moraine 3486 Caliper Fig. 3 Exploded View Of Disc Brake Caliper Assembly. The caliper assembly slides on its mounting surfaces, Fig. 3. Upon brake application, hydraulic pressure against the piston forces the inboard pad against the inboard side of the disc. This action causes the caliper assembly to slide until the outboard pad comes into contact with the disc, which in turn creates a slowing or stopping action. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Description and Operation > Page 8924 Brake Caliper: Testing and Inspection Should it become necessary to remove the caliper for installation of new parts, clean all parts in denatured alcohol, wipe dry using lint-free cloths. Using compressed air, blow out drilled passages and bores. Check dust boots for punctures or tears. If punctures or tears are evident, new boots should be installed upon reassembly. Inspect piston bores in both housings for scoring or pitting. Bores that show light scratches or corrosion can usually be cleaned with crocus cloth. However, bores that have deep scratches or scoring may be honed, provided the diameter of the bore is not increased more than .002 inch. If the bore does not clean up within this specification, a new caliper housing should be installed (black stains on the bore walls are caused by piston seals and will do no harm). When using a hone, be sure to install the hone baffle before honing bore. The baffle is used to protect the hone stones from damage. Use extreme care in cleaning the caliper after honing. Remove all dust and grit by flushing the caliper with denatured alcohol. Wipe dry with clean lint-free cloth and then clean a second time in the same manner. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper Brake Caliper: Service and Repair Bendix Single Piston Sliding Caliper Removal/Installation REMOVAL Fig. 2 Bottoming Position In Bore Fig. 3 Removing Caliper Support Key Fig. 4 Removing Or Installing Caliper 1. Siphon two-thirds of brake fluid from master cylinder reservoir serving front disc brakes. 2. Raise vehicle, support on jack stands and remove front wheels. 3. Bottom the caliper piston in bore. Insert a screwdriver between inboard shoe and piston, then pry piston back into bore. The piston can also be bottomed in the bore with a large C-clamp, Fig. 2. 4. Remove support key retaining screw. 5. Drive caliper support key and spring from steering knuckle with a suitable drift and hammer, Fig. 3. 6. Lift caliper from anchor plate and off rotor, Fig. 4. Hang caliper from coil spring with wire. Do not allow caliper to hang from brake hose. 7. Remove inboard pad from steering knuckle, then the anti-rattle spring from the pad. 8. Remove outboard pad from caliper. It may be necessary to loosen the pad with a hammer to permit removal. INSTALLATION 1. Clean and lubricate sliding surfaces of caliper and the anchor plate with Delco Silicone Lube, P/N 5459912, or equivalent. 2. Install anti-rattle spring on inboard pad, and ensure looped section of clip is facing away from rotor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8927 3. Install inboard pad in steering knuckle. 4. Install outboard pad in caliper. Ensure pad is seated fully into outboard arms of caliper. It may be necessary to tap the ears and bottom tab with a hammer to seat the pad being careful not to hit the friction material. 5. Place caliper assembly over rotor and position in steering knuckle. Ensure dust boot is not torn or improperly positioned by inboard pad during caliper installation. 6. Align caliper with steering knuckle abutment surfaces, then insert support key and spring between abutment surfaces at the trailing end of caliper and steering knuckle. With a hammer and brass drift, drive caliper support key and spring into position, then install and torque support key retaining screw to 12-18 ft. lbs. 7. Refill master cylinder to within one inch of rim. Press brake pedal several times to seat pads. 8. Install front wheels and lower vehicle. Disassembly/Inspection/Assembly DISASSEMBLY Fig. 5 Removing Caliper Piston Fig. 6 Exploded View Of Disc Brake Caliper Assembly 1. Drain brake fluid from caliper. 2. Position caliper with shop cloths, Fig. 5, and apply compressed air to fluid inlet port to ease piston from bore. Do not attempt to catch piston or to protect it when applying compressed air, since personal injury is possible. 3. Remove dust boot, then the piston seal from bore, Fig. 6. Use wooden or plastic tool to remove piston seal since metal tools may damage piston. 4. Remove bleeder screw INSPECTION Clean all parts in denatured alcohol, wipe dry using lint-free cloths. Using compressed air, blow out drilled passages and bores. Check dust boots for punctures or tears. If punctures or tears are evident, new boots should be installed upon reassembly. Inspect piston bores in both housings for scoring or pitting. Bores that show light scratches or corrosion can usually be cleaned with crocus cloth. However, bores that have deep scratches or scoring may be honed, provided the diameter of the bore is not increased more than .002 inch. If the bore does not clean up within this specification, a new caliper housing should be installed (black stains on the bore walls are caused by piston seals and will do no harm). When using a hone, be sure to install the hone baffle before honing bore. The baffle is used to protect the hone stones from damage. Use extreme care in cleaning the caliper after honing. Remove all dust and grit by flushing the caliper with denatured alcohol. Wipe dry with clean lint-free cloth and then clean a second time in the same manner. ASSEMBLY Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8928 Fig. 7 Installing Caliper Piston Boot Fig. 8 Installing Piston In Caliper 1. Coat square cut piston seal with clean brake fluid, then install seal into piston bore. Work seal into groove with clean fingers. 2. Install and torque bleeder screw to specifications. 3. Lubricate boot and installation tool No. J-24548 with clean brake fluid, then place dust seal on tool, allowing 1/4 inch of tool to extend past small lip of boot, Fig. 7. 4. Place dust seal and tool over piston bore, then work large lip of boot into seal groove, Fig. 8. Ensure dust seal is fully seated. 5. Lubricate caliper piston and insert through tool. Center piston in bore and use a hammer handle to apply pressure to install piston halfway into bore, Fig. 8. 6. Remove installation tool No. J-24548 and seat small lip of boot in caliper piston groove, then bottom piston in bore. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8929 Brake Caliper: Service and Repair Delco-Moraine Single Piston Caliper Removal/Installation REMOVAL Fig. 2 Compressing Piston & Pad With C-clamp 1. Siphon enough brake fluid out of the master cylinder to bring fluid level to 1/3 full to avoid fluid overflow when the caliper piston is pushed back into its bore. 2. Raise and support vehicle, remove front wheels. 3. Using a C-clamp, as illustrated in Fig. 2, push piston back into its bore. 4. Remove two mounting bolts and lift caliper away from disc. INSTALLATION 1. Position caliper over disc, lining up mounting holes in caliper with holes in mounting bracket. If brake hose was not disconnected during removal, be sure not to kink it during installation. 2. Start mounting bolts through sleeves in inboard caliper ears and the mounting bracket, making sure ends of bolts pass under ears on inboard shoe. Right and left calipers must not be interchanged. 3. Push mounting bolts through to engage holes in the outboard ears. Then thread mounting bolts into bracket. 4. Torque mounting bolts to specifications. 5. If brake hose was removed, reconnect it and bleed the calipers. 6. Replace front wheels, lower vehicle and add brake fluid to master cylinder to bring level to 1/4 inch from top. Before moving vehicle, pump brake pedal several times to be sure it is firm. Do not move vehicle until a firm pedal is obtained. Disassembly/Inspection/Assembly DISASSEMBLY Fig. 4 Removing Piston From Caliper 1. Disconnect hose from the caliper being careful not to lose copper washers. 2. Remove caliper as outlined above. 3. Drain brake fluid from caliper. 4. Pad caliper interior with clean shop towels and apply compressed air to remove piston, Fig. 4. Use just enough air pressure to ease piston out of Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8930 bore. When applying compressed air do not place fingers in front of piston in an attempt to catch or protect it as this could result in serious injury. 5. Carefully pry dust boot out of bore. 6. Using a small piece of wood or plastic, remove piston seal from bore. Do not use a metal tool of any kind to remove seal as it may damage bore. 7. Remove bleeder valve. INSPECTION Clean all parts in denatured alcohol, wipe dry using lint-free cloths. Using compressed air, blow out drilled passages and bores. Check dust boots for punctures or tears. If punctures or tears are evident, new boots should be installed upon reassembly. Inspect piston bores in both housings for scoring or pitting. Bores that show light scratches or corrosion can usually be cleaned with crocus cloth. However, bores that have deep scratches or scoring may be honed, provided the diameter of the bore is not increased more than .002 inch. If the bore does not clean up within this specification, a new caliper housing should be installed (black stains on the bore walls are caused by piston seals and will do no harm). When using a hone, be sure to install the hone baffle before honing bore. The baffle is used to protect the hone stones from damage. Use extreme care in cleaning the caliper after honing. Remove all dust and grit by flushing the caliper with denatured alcohol. Wipe dry with clean lint-free cloth and then clean a second time in the same manner. ASSEMBLY Fig. 5 Installing Boot To Piston Fig. 6 Installing Boot To Caliper 1. Lubricate caliper piston bore and new piston seal with clean brake fluid. Position seal in bore groove. 2. Lubricate piston with clean brake fluid and assemble a new boot into the groove in the piston so the fold faces the open end of the piston, Fig. 5. 3. Using care not to unseat the seal, insert piston into bore and force the piston to the bottom of the bore. 4. Position dust boot in caliper counterbore and install, Fig. 6. Check the boot installation to be sure the retaining ring molded into the boot is not bent and that the boot is installed below the caliper face and evenly all around. If the boot is not fully installed, dirt and moisture may enter the bore and cause corrosion. 5. If available, use new copper washers discarding the old washers and install the brake hose to the caliper. 6. Install pads and caliper assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8931 Brake Caliper: Service and Repair Removal and Installation Delco CALIPER Remove or Disconnect 1. Two-thirds of the brake fluid from master cylinder. 2. Raise vehicle and support with safety stands. 3. Tire and wheel. ^ On models with composite rotor, reinstall two lug nuts to retain rotor. Compressing Piston Prior To Caliper Removal 4. Compress piston using adjustable pliers over inboard lining (7) tab and caliper housing flange (12). 5. Brake hose from caliper by removing inlet fitting bolt (14). 6. Mounting bolts (2). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8932 7. Bolt boots (1). Suspending The Caliper 8. Caliper (12). Delco Shoe And Lining Assembly (3400) 9. Mounting bolt seals (4), if used. 10. Bushings (3). NOTE: Inspect the mounting bolt and sleeve assemblies for corrosion. Replace if any is found. Do not attempt to polish away corrosion. Inspect bolt boots for nicks, cuts, or corrosion. Replace if any are found. NOTE: Clean the caliper assembly and install a new brake hardware kit anytime it is removed from rotor. Install or Connect CAUTION: Always use the correct fastener in the proper location. When you replace a fastener, use ONLY the exact part number for that application. General Motors will call out those fasteners that require a replacement after removal. General Motors will also call out the fasteners that require thread lockers or thread sealant. Unless otherwise specified, do not use supplemental coatings (paints, greases, or other corrosion inhibitors) on threaded fasteners or fastener joint interfaces. Generally, such coatings adversely affect the fastener torque and joint clamping force, and may damage the fastener. When you install fasteners, use the correct tightening sequence and specifications. Following these instructions can help you avoid damage to parts and systems. NOTE: Any new rotor must have the protective coating removed from the friction surfaces before being placed in service. Use Goodwrench Brake Parts Cleaner (GM PIN 12345754), or equivalent, and wipe the surface clean with clean cloths. Do not use gasoline, kerosene or other oil-based solvents which may leave an oily residue. This residue is damaging to brake linings and flammable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8933 Delco Shoe And Lining Assembly (3400) 1. New bushings (3) and bolt seals (4). Mounting Bolt Lubrication (Delco 3400) 2. Lubricate bushings (3) and mounting bolt seals (4) with GM P/N 18010909 or equivalent. 3. New bolt boots (1). 4. Caliper (12). ^ Fill both housing cavities between bushings (3) with GM P/N 18010909, or equivalent. 5. Mounting bolt and sleeve assemblies (2). ^ Tighten bolt (2) to 51 Nm (38 lb. ft.). The bolt boots (1) must remain secure after tightening bolts. 6. Brake hose to caliper. ^ Tighten brake hose bolt to 45 Nm (33 lb. ft.). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8934 Caliper To Bracket Clearance 7. Measure clearance between caliper (12) and bracket stops (16). If necessary, remove caliper and file the ends of bracket (16) to obtain 0.26 to 0.60 mm (0.010 to 0.024 inch) total clearance. Measure the clearances individually and add them together. 8. Tire and wheel. NOTE: Before moving the vehicle, pump the brake pedal several times to make sure it is firm. Do not move the vehicle until a firm pedal is obtained. Check the fluid level in the master cylinder after pumping the brakes. Bendix CALIPER Shoe And Lining Assembly Remove or Disconnect 1. Two-thirds of the brake fluid from master cylinder. 2. Raise vehicle and support with safety stands. 3. Mark relationship of wheel to hub. 4. Tire and wheel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8935 Compressing The Caliper Piston 5. Position a C-clamp and tighten until piston bottoms in bore. 6. C-Clamp. 7. Brake hose. Caliper Mounting 8. Bolt (2). 9. Support key (3) and spring (4). Removing The Caliper Support Key ^ Use a brass punch and a hammer to drive the support key out. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8936 Suspending The Caliper 10. Caliper assembly (1). NOTE: Inspect the inside of the caliper assembly for signs of fluid leakage. Clean: Use a wire brush to remove any corrosion from the machined surfaces of the anchor plate and caliper. Install or Connect CAUTION: Always use the correct fastener in the proper location. When you replace a fastener, use ONLY the exact part number for that application. General Motors will call out those fasteners that require a replacement after removal. General Motors will also call out the fasteners that require thread lockers or thread sealant. Unless otherwise specified, do not use supplemental coatings (paints, greases, or other corrosion inhibitors) on threaded fasteners or fastener joint interfaces. Generally, such coatings adversely affect the fastener torque and joint clamping force, and may damage the fastener. When you install fasteners, use the correct tightening sequence and specifications. Following these instructions can help you avoid damage to parts and systems. NOTE: Any new rotor must have the protective coating removed from the friction surfaces before being placed in service. Use Goodwrench Brake Parts Cleaner (GM PIN 12345754), or equivalent, and wipe the surface clean with clean cloths. Do not use gasoline, kerosene or other oil-based solvents which may leave an oily residue. This residue is damaging to brake linings and flammable. 1. Lubricate caliper and anchor plate sliding surfaces with Shell Aeroshell No. 5, or equivalent. Suspending The Caliper 2. Caliper assembly. CAUTION: Make sure the brake hose Is not twisted or kinked after installation. Damage to the hose could result. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8937 CAUTION: Do not use anti-seize type products on the caliper V-ways and anchor plate guide way surfaces. These products are not lubricants and result in high caliper slide forces, which can cause increased wear of the brake pads. Installing The Caliper Support Key 3. Spring (4) and support key (3). Use a brass punch and hammer to drive the support key in place. 4. Caliper lock mounting bolts. The boss on the bolt must fit into the circular cutout in the key. ^ Tighten bolts to 20 Nm (15 lb. ft.). 5. Brake hose. ^ Tighten brake hose bolt to 45 Nm (33 lb. ft.). 6. Bleed brake system. Refer to Hydraulic System Service and Repair. 7. Tire and wheel. 8. Lower the vehicle. CAUTION: Before moving the vehicle, pump the brake pedal several times to make sure it is firm. Do not move the vehicle until a firm pedal is obtained. Check the brake fluid level in the master cylinder after pumping the brakes. Rear Disc Brakes CALIPER Remove or Disconnect 1. Two-thirds of the brake fluid from master cylinder. 2. Raise vehicle and support with safety stands. 3. Mark relationship of wheel to hub. 4. Tire and wheel. Compressing The Caliper Piston 5. Position a C-clamp and tighten until piston bottoms in bore. 6. C-Clamp. 7. Brake hose. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8938 Disc Brake Assembly 8. Bolt (2). 9. Support key (3) and spring (4). Removing The Caliper Support Key ^ Use a brass punch and a hammer to drive the support key out. Suspending The Caliper 10. Caliper assembly (1). NOTE: Inspect the inside of the caliper assembly for signs of fluid leakage. If any is found, refer to Overhaul. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8939 Clean: Use a wire brush to remove any corrosion from the machined surfaces of the anchor plate and caliper. Install or Connect CAUTION: Always use the correct fastener in the proper location. When you replace a fastener, use ONLY the exact part number for that application. General Motors will call out those fasteners that require a replacement after removal. General Motors will also call out the fasteners that require thread lockers or thread sealant. Unless otherwise specified, do not use supplemental coatings (paints, greases, or other corrosion inhibitors) on threaded fasteners or fastener joint interfaces. Generally, such coatings adversely affect the fastener torque and joint clamping force, and may damage the fastener. When you install fasteners, use the correct tightening sequence and specifications. Following these instructions can help you avoid damage to parts and systems. NOTE: Any new rotor must have the protective coating removed from the friction surfaces before being placed in service. Use Goodwrench Brake Parts Cleaner (GM P/N 12345754), or equivalent, and wipe the surface clean with clean cloths. Do not use gasoline, kerosene or other oil-based solvents which may leave an oily residue. This residue is damaging to brake linings and flammable. 1. Lubricate caliper and anchor plate sliding surfaces with Shell Aeroshell Grade 5 lubricant or equivalent. Suspending The Caliper 2. Caliper assembly. CAUTION: Make sure the brake hose Is not twisted or kinked after installation. Damage to the hose could result. CAUTION: Do not use "never sieze" type products on the caliper V-ways and anchor plate guide way surfaces. These products are not lubricants and result in high caliper slide forces, which can cause increased wear of the brake pads. Installing The Caliper Support Key 3. Spring (4) and support key (3). Use a brass punch and hammer to drive the support key in place. 4. Caliper lock mounting bolts. The boss on the bolt must fit into the circular cutout in the key. ^ Tighten bolts to 20 Nm (15 lb. ft.). 5. Brake hose. ^ Tighten brake hose bolt to 45 Nm (33 lb. ft.). 6. Bleed brake system. Refer to Hydraulic System Service and Repair. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Caliper > Component Information > Service and Repair > Bendix Single Piston Sliding Caliper > Page 8940 7. Tire and wheel. 8. Lower the vehicle. CAUTION: Before moving the vehicle, pump the brake pedal several times to make sure it is firm. Do not move the vehicle until a firm pedal is obtained. Check the brake fluid level in the master cylinder after pumping the brakes. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Fluid > Component Information > Technical Service Bulletins > Brake Fluid - Level & Filling Recommendations Brake Fluid: Technical Service Bulletins Brake Fluid - Level & Filling Recommendations File In Section: 05 - Brakes Bulletin No.: 00-05-22-004 Date: May, 2000 INFORMATION Subject: Brake Fluid Level and Filling Recommendations Models: 2001 and Prior Passenger Cars and Trucks Many dealers and after-market repair shops advertise multi-point fluid "top-ups" in conjunction with oil changes or regular maintenance packages. These offers often include adding brake fluid to the master cylinder reservoir. There are only two reasons why the brake fluid level in the brake reservoir might go down. The first is that the brake fluid level goes down an acceptable level during normal brake lining wear. When the linings are replaced, the fluid will return to it's original level. The second possible reason for a low fluid level is that fluid is leaking out of the brake system. If fluid is leaking, the brake system requires repair and adding additional fluid will not correct the leak. If the system was properly filled during delivery of the vehicle, no additional fluid should be required under most circumstances between brake pad and/or shoe replacements. This information can be reinforced with the customer by referring them to the Brake Fluid section of their vehicle's Owner's Manual. Guidelines GM vehicles have incorporated a variety of brake fluid reservoir styles. The following guidelines are restricted to the plastic bodied fluid reservoirs and do not affect the original service recommendations for the older style metal bodied units. You may encounter both black plastic and translucent style reservoirs. You may have reservoirs with: ^ A MAX fill mark only ^ A MIN fill mark only ^ Both MAX and MIN marks The translucent style reservoirs do not have to have the covers removed in order to view the fluid level. It is a good practice not to remove the reservoir cover unless necessary to reduce the possibility of contaminating the system. Use the following guidelines to assist in determining the proper fluid level. Important: When adding brake fluid, use Delco Supreme II(R) Brake Fluid, GM P/N 12377967 or equivalent brand bearing the DOT-3 rating only. Important: At no time should the fluid level be allowed to remain in an overfilled condition. Overfilling the brake reservoir may put unnecessary stress on the seals and cover of the reservoir. Use the following guidelines to properly maintain the fluid level. If the reservoir is overfilled, siphon out the additional fluid to comply with the guidelines below. Important: If under any circumstance the brake fluid level is extremely low in the reservoir or the BRAKE warning indicator is illuminated, the brake system should be checked for leaks and the system repaired in addition to bringing the fluid level up to the recommended guidelines outlined below. A leaking brake system will have reduced braking performance and will eventually not work at all. Important: Some vehicles have reservoirs that are very sensitive to brake fluid levels and may cause the BRAKE indicator to flicker on turns as the fluid approaches the minimum required level. If you encounter a vehicle with this concern, increase the fluid level staying within the guidelines outlined below. ^ If the reservoir has a MAX level indicator, the reservoir should be returned to the MAX marking only at the time new brake pads and/or shoes are installed. If the reservoir fluid level is at the half-way point or above do not attempt to add additional brake fluid during routine fluid checks. ^ If the reservoir has both MAX and MIN indicators, the fluid level should be maintained above the MIN indicator during routine fluid checks and returned to the MAX indication only after new brake pads and/or shoes are installed. ^ For reservoirs with only a MIN indication, the fluid level should be maintained above the MIN indicator during routine fluid checks. Return the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Fluid > Component Information > Technical Service Bulletins > Brake Fluid - Level & Filling Recommendations > Page 8945 reservoir fluid level to full only after installing new brake pads and/or shoes. A full reservoir is indicated on translucent, snap cover reservoirs by a fluid level even with the top level of the view window imprinted into the side of the reservoir. On screw top models in black or translucent plastic, the full level is just below the bottom of the filler neck. Parts Information Part Number Description 12377967 Brake Fluid Parts are currently available from GMSPO. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Fluid > Component Information > Technical Service Bulletins > Page 8946 Brake Fluid: Specifications Brake System DOT 3 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Fluid Pressure Sensor/Switch > Component Information > Locations Brake Fluid Pressure Sensor/Switch: Locations Behind I/P Compartment Box on HVAC Plenum Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Proportioning/Combination Valve > Component Information > Description and Operation Brake Proportioning/Combination Valve: Description and Operation These vehicles use either a two function or three function combination valve. Some vehicles use a height sensitive proportioning valve in addition to the combination valve. The two function combination valve consists of a metering valve and a brake failure warning switch. The hydraulic brake lines are routed through this valve to the wheel cylinders or calipers. The metering portion of this valve assists in providing balanced front to rear braking by delaying full hydraulic fluid pressure to the front disc brakes until the rear drum brakes overcome return spring tension and the linings contact the drums. The brake failure warning switch portion of the valve activates the brake warning lamp when there is a loss of pressure in either the front or the rear braking system. The three function combination valve consists of a metering valve, a brake failure warning switch, and a proportioning valve. The metering valve and brake failure warning switch operate the same as those in the two function combination valve previously described. The proportioning section of the valve proportions outlet pressure to the rear brakes after a certain rear input pressure has been reached, preventing rear wheel lock-up. The height sensitive proportioning valve provides ideal brake balance according to weight at rear axle. This valve is mounted on the frame and responds to changes in vehicle trim height in relation to rear axle load. Mechanical linkage connects the valve to a bracket attached to the rear axle. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Proportioning/Combination Valve > Component Information > Description and Operation > Page 8953 Brake Proportioning/Combination Valve: Adjustments Fig. 9 Height Sensing Proportioning Valve Fig. 10 Adjustment Gauge Installation The height sensing proportioning valve must be adjusted whenever the valve and/or linkage is disassembled or removed for service. In addition, adjustment should be checked if excessive front wheel lock-up is experienced with a lower than desired brake application rate when vehicle is at or near maximum GVWR. 1. Raise and support vehicle leaving wheels on, and allow axle to hang free (no load condition). 2. Remove lever retaining nut and disconnect lever from valve shaft, Fig. 9. 3. Rotate valve shaft to permit installation of correct adjustment gauge, Fig. 10, ensuring that D shaped hole of gauge is properly seated on valve shaft and that gauge tang engages mounting hole in valve. Adjustment gauges vary depending upon vehicle application. Correct gauge must be used to ensure proper operation of braking system. 4. Install lever on valve shaft by pressing plastic bushing and clip assembly over shaft serrations using C-clamp or suitable pliers. Do not press lever onto shaft using retaining nut, as adjustment of valve will be disturbed. 5. Install lever retaining nut and torque to 70-98 inch lbs. 6. Cut tang off adjustment gauge and allow valve to rotate freely. 7. Lower vehicle and test brakes. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Proportioning/Combination Valve > Component Information > Description and Operation > Page 8954 Brake Proportioning/Combination Valve: Service and Repair Fig. 228 Combination Valve Replacement. 1. Disconnect battery ground cable, then raise and support vehicle. 2. Remove bolts securing shield (if equipped) and Brake Pressure Modulator Valve (BPMV) to EHCU bracket. 3. Disconnect combination valve electrical connector, then the front and rear brake pipes. Prevent fluid spillage with clean shop towels. 4. Remove bolts securing combination valve to BPMV, Fig. 228, then separate valve from BPMV. 5. Reverse procedure to install, noting the following: a. Torque combination valve mounting bolts alternately to 6 ft. lbs., then to 12 ft. lbs. b. Torque brake pipe fittings to 18 ft. lbs. c. Bleed brake system. Refer to Brakes / Service and Repair / Bleeding Brakes. See: Service and Repair Ensure combination valve metering rod is depressed during bleeding. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Hydraulic Control Assembly Antilock Brakes > Component Information > Locations Hydraulic Control Assembly - Antilock Brakes: Locations Underhood Fuse-Relay Center Brake Pressure Modulator Valve Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Hydraulic Control Assembly Antilock Brakes > Component Information > Locations > Page 8958 Vehicle Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Hydraulic Control Assembly Antilock Brakes > Component Information > Locations > Page 8959 Hydraulic Control Assembly - Antilock Brakes: Service and Repair The BPMV is not serviceable and must be replaced as a unit. 1. Disconnect battery ground cable, then raise and support vehicle. 2. Disconnect four EBCM electrical connectors. 3. Disconnect combination valve electrical connector and brake pipes. Use shop towels to prevent brake fluid spillage. 4. Disconnect hydraulic lines at BPMV tube adapters, then remove EHCU from vehicle. 5. Remove four Torx bolts from EBCM, then separate BPMV from EBCM. Do not pry on components to separate. 6. Reverse procedure to install, noting the following: a. Install a new EBCM gasket, mounting bolts and transfer tubes. Do not reuse these components. b. Torque combination valve bolts alternately to 6 ft. lbs., then to 12 ft. lbs. c. Torque EBCM Torx bolts to 39 inch lbs. in a crisscross pattern. d. Torque EHCU to base bracket bolts and BPMV bolts to 7 ft. lbs. e. Torque brake pipe fittings to 18 ft. lbs., then bleed brake system. See: Brake Bleeding Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Master Cylinder > Component Information > Description and Operation Brake Master Cylinder: Description and Operation Master Cylinder Some vehicles use a conventional tandem master cylinder with two hydraulic pistons operating in line. The primary piston controls the front brake system and the secondary piston controls the rear brake system. Other models use a master cylinder that operates the same as the conventional master cylinder, but also incorporates a quick take-up feature in the rear chamber to reduce excessive pedal travel which may result from increased fluid displacement required to move the low drag caliper piston out against the rotor. The quick take-up uses a spring-loaded ball check valve to hold pressure in the large diameter rear chamber when the brakes are first applied. At initial application, movement of the rear piston causes fluid to be displaced forward past the primary piston seal into the primary high pressure chamber. At a specified pressure, the ball unseats and fluid from the large rear bore is displaced past the bore into the reservoir. When the brake pedal is released, suction generated in the large bore chamber replenishes its fluid supply by drawing fluid from the reservoir around the quick take-up lip seal and through a small bleed orifice in the ball seat. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Master Cylinder > Component Information > Service and Repair > Bendix Type Master Cylinder Brake Master Cylinder: Service and Repair Bendix Type Master Cylinder Power Brake Systems 1. Disconnect all wire connectors from master cylinder components. 2. Disconnect brake lines from master cylinder. 3 Remove master cylinder mounting nuts, then the master cylinder. 4. Reverse procedure to install. Manual Brake Systems 1. Disconnect master cylinder pushrod from brake pedal. 2. Disconnect all wire connectors from master cylinder components. 3. Disconnect brake lines from master cylinder. 4. Remove master cylinder mounting nuts, then the master cylinder. 5. Reverse procedure to install. Disassembly/Assembly Fig. 6 Exploded View Of Master Cylinder. 1. Remove master cylinder from vehicle. 2. Clean outside of master cylinder, then remove reservoir cover and diaphragm. 3. Drain brake fluid from reservoir, then remove reservoir attaching bolts and reservoir. 4. Remove O-ring, compensating valve seals, valve poppets and springs. 5. Depress primary piston, then remove snap ring. 6. Remove primary piston assembly and piston return spring. 7. Remove secondary piston assembly by applying small amount of air pressure to front compensating valve port. Ensure front port is plugged. 8. Remove secondary spring. 9. Reverse procedure to assemble, noting the following: a. Inspect cylinder bore for scoring and corrosion. Replace master cylinder if necessary. b. Clean all metal parts in denatured alcohol. c. Clean all rubber parts in clean brake fluid. d. Polish discolored or stained cylinder with crocus cloth, then rinse in clean brake fluid. Ensure compensating port is clean. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Master Cylinder > Component Information > Service and Repair > Bendix Type Master Cylinder > Page 8965 Brake Master Cylinder: Service and Repair Delco Moraine Type Power Brake Systems 1. Disconnect all wire connectors from master cylinder components. 2. Disconnect brake lines from master cylinder. 3 Remove master cylinder mounting nuts, then the master cylinder. 4. Reverse procedure to install. Manual Brake Systems 1. Disconnect master cylinder pushrod from brake pedal. 2. Disconnect all wire connectors from master cylinder components. 3. Disconnect brake lines from master cylinder. 4. Remove master cylinder mounting nuts, then the master cylinder. 5. Reverse procedure to install. Composite Type Fig. 2 Exploded View Of Master Cylinder Disassembly 1. Remove master cylinder from vehicle. 2. Remove reservoir cover and diaphragm. Discard old brake fluid in reservoir. 3. Inspect cover and diaphragm. Replace if cut, cracked or deformed. 4. Remove fluid level switch and proportioner valve assembly, if equipped. 5. Depress primary piston and remove lock ring. 6. Plug primary fluid outlet (outlet nearest to cowl when master cylinder is installed), then apply compressed air into secondary fluid outlet to remove primary and secondary pistons. 7. Remove spring retainer and seals from secondary piston. 8. Clamp master cylinder in a vise, then remove reservoir using a pry bar. Remove reservoir grommets. 9. Inspect master cylinder bore for corrosion. Do not use abrasive material on master cylinder bore. Replace if bore is corroded. Assembly Clean all parts not included in repair kit with brake fluid. Do not dry with compressed air. Lubricate all rubber parts with clean brake fluid prior to installation. 1. Lubricate new reservoir grommets with silicone brake lube, then press grommets into master cylinder body. Ensure grommets are properly seated. 2. Lay reservoir upside down on flat, hard surface. Press master cylinder body onto reservoir using rocking motion. 3. Install new seals on secondary piston, then the spring retainer. 4. Install spring and secondary piston assembly into cylinder. 5. Install primary piston. Depress primary piston into cylinder, then install lock ring. 6. Install fluid level switch and proportioner valve assembly, if equipped. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Master Cylinder > Component Information > Service and Repair > Bendix Type Master Cylinder > Page 8966 7. Fit diaphragm into reservoir cover, then install cover onto reservoir. 8. Install master cylinder in vehicle. Cast Iron Type Fig. 4 Exploded View Of Master Cylinder. Fig. 5 Secondary Piston & Seals. Disassembly 1. Remove master cylinder from vehicle. 2. Clean outside of master cylinder, then remove reservoir cover and diaphragm. 3. Turn master cylinder over, then pump pushrod by hand to remove any remaining brake fluid. 4. Clamp master cylinder in a vise, with vise jaws gripping mounting flange and fluid ports pointing up. Do not clamp master cylinder body in vise. 5. Remove lock ring and primary piston assembly from cylinder bore. 6. Apply compressed air to secondary outlet port to remove secondary piston spring and retainer. 7. Using a 13/64 inch drill, enlarge hole in tube fitting insert of fluid outlet holes. Place a heavy washer over outlet hole, then thread a 1/4 X 20 X 3/4 screw into insert. Tighten screw until insert is unseated, then remove insert, screw and washer. 8. Remove primary and secondary seal from secondary piston. Inspection Clean all parts not included in repair kit with brake fluid. Do not dry with compressed air. 1. Inspect cylinder bore for scoring and corrosion. Replace master cylinder if necessary. 2. Polish discolored or stained cylinder with crocus cloth, then rinse in clean brake fluid. Ensure compensating port is clean. Assembly Lubricate all rubber parts with clean brake fluid prior to installation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Brake Master Cylinder > Component Information > Service and Repair > Bendix Type Master Cylinder > Page 8967 1. With master cylinder in a vise, insert brass tube fitting inserts from overhaul kit into outlet holes. 2. Using spare brake line tube, thread tube nut into outlet hole and turn down until tube fitting insert bottoms into outlet hole. Remove tube nut and inspect outlet hole for burrs. 3. Install inner secondary seal into groove in secondary piston. 4. Install primary seal over end of secondary piston, with flat side of seal against flange of piston. 5. Install outer secondary seal into groove in end of secondary piston. 6. Install secondary piston spring retainer into secondary piston spring, then place the retainer and spring over end of secondary piston, with retainer seated inside lip of primary cup. 7. Hold master cylinder with open end down, then place secondary piston assembly into bore, with spring seated against end of bore. 8. Clamp master cylinder in a vise with open end of bore facing up. 9. Insert new primary piston assembly, spring end first, into bore. 10. Hold primary piston down, then install lock ring in groove on inside of bore. 11. Install new reservoir diaphragm into reservoir cover with beaded side out, then secure cover onto cylinder. 12. Install master cylinder in vehicle. Bleed brakes. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Wheel Cylinder > Component Information > Technical Service Bulletins > Brakes - Wheel Cylinder Inspection Guidelines Wheel Cylinder: Technical Service Bulletins Brakes - Wheel Cylinder Inspection Guidelines Bulletin No.: 03-05-24-001A Date: March 21, 2005 INFORMATION Subject: Service Information Regarding Rear Brake Drum Wheel Cylinder Inspections Models: 2005 and Prior GM Passenger Cars and Trucks 2005 and Prior Saturn Vehicles with Rear Drum Brakes Supercede: This bulletin is being revised add model years and include all GM vehicles. Please discard Corporate Bulletin Number 03-05-24-001 (Section 03 - Suspension). This bulletin provides information on proper inspection of rear drum brake wheel cylinders. Important: It is not recommended that dust boots be removed during inspection processes as dirt and debris could contaminate the wheel cylinder bore causing premature wear of the wheel cylinder. In addition, most bores should look damp and some lubricant may drip out from under the boot as a result of lubricant being present. All rear drum brake wheel cylinders are assembled with a lubricant to aid in assembly, provide an anti-corrosion coating to the cylinder bore, and lubricate internal rubber components. As a result of this lubrication process, it is not uncommon for some amount of lubricant to accumulate at the ends of the cylinder under the dust boot. Over time, the lubricant may work its way to the outside of the boot and cause an area of the boot to look damp. Evidence of a damp area on the boot does not indicate a leak in the cylinder. However, if there is excessive wetness (i.e. drips) coming from the boot area of the wheel cylinder, it could indicate a brake hydraulic fluid leak requiring wheel cylinder replacement. (Refer to the Wheel Cylinder Replacement procedures in the appropriate Service Manual.) Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Hydraulic System, Brakes > Wheel Cylinder > Component Information > Technical Service Bulletins > Page 8972 Wheel Cylinder: Service and Repair Disassembled View Of Wheel Cylinder (typical) 1. Raise and support vehicle. 2. Remove wheel, drum and brake shoes. 3. Disconnect hydraulic line at wheel cylinder. 4. Remove wheel cylinder attaching screws, then remove wheel cylinder. 5. Strip cylinder of boots, pistons, springs and seals, Fig. 9. 6. Inspect cylinder bore for scoring and corrosion. Discoloration is a sign that springs have been damaged by heat, replace them if necessary. 7. Clean cylinder bore with crocus cloth. If cleaning does not remove scoring, replace cylinder. 8. Lubricate cylinder bore and seals with brake fluid, then reassemble cylinder. 9. Reverse procedure to install. Bleed system. Refer to Brakes / Service and Repair / Brake System Bleed. See: Service and Repair Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Parking Brake System > Parking Brake Cable > Component Information > Testing and Inspection Parking Brake Cable: Testing and Inspection Inspect parking brake cable end for kinks, fraying and elongation, and replace as necessary. Use a small hose clamp to compress clamp where it enters backing plate to remove. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Hydraulic Brake Booster > Component Information > Description and Operation Hydraulic Brake Booster: Description and Operation Fig. 1 Cross-sectional View Of Bendix Hydro-Boost Unit. In order to properly service power brake systems, a thorough understanding of the power assist system is necessary. These systems provide a mechanical assist, acting to increase the force applied to the master cylinder piston by the driver while decreasing the effort necessary to obtain acceptable stopping performance. Hydraulic assist units incorporate a basic open center spool valve, hydraulic cylinder and an accumulator assembly in a common housing. When the brake pedal is depressed, the hydraulic piston moves forward closing off fluid relief passages, the spool valve applies fluid pressure to the rear of the piston, and pressure applied to the piston is transmitted to the brake master cylinder through a pushrod. When the brake pedal is released, fluid pressure behind the piston is exhausted through the open center of the spool valve to a return line and the pump reservoir, and the spool valve diverts fluid pressure away from the hydraulic piston. The accumulator stores sufficient fluid under pressure to provide two or three power assisted stops in the event that pressure from the pump is interrupted. The design of the hydraulic cylinder allows the brakes to be applied without power assist, however, greater pedal effort is required to apply the brakes manually. The Hydro-Boost system, Fig. 1, provides an additional cylinder in the brake system. This cylinder contains no brake fluid. The Hydro-Boost cylinder is hydraulically operated, by pressurized fluid from the power steering pump, providing power assist to operate a dual master cylinder brake system. The booster is composed of two sections; the linkage section and the power section. The booster is designed so that if a total absence of power assist occurs, the brakes can be applied manually, but somewhat greater pressure on the brake pedal is required. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Hydraulic Brake Booster > Component Information > Testing and Inspection > Slow Brake Pedal Return Hydraulic Brake Booster: Testing and Inspection Slow Brake Pedal Return 1. Excessive seal friction in booster. 2. Faulty spool action. 3. Restriction in return line from booster to pump reservoir. 4. Damaged input rod end. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Hydraulic Brake Booster > Component Information > Testing and Inspection > Slow Brake Pedal Return > Page 8983 Hydraulic Brake Booster: Testing and Inspection Grabby Brakes/ Booster Chatters/ Pedal Vibrates 1. Faulty spool action caused by contamination in system. 2. Power steering pump belts slip. 3. Low fluid level in power steering pump. 4. Faulty spool operation caused by contamination in system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Hydraulic Brake Booster > Component Information > Testing and Inspection > Slow Brake Pedal Return > Page 8984 Hydraulic Brake Booster: Testing and Inspection Accumulator Leak-Down/ System Does Not Hold Charge 1. Contamination in steering Hydro-Boost system. 2. Internal leakage in accumulator system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Hydraulic Brake Booster > Component Information > Service and Repair > General Service Information Hydraulic Brake Booster: Service and Repair General Service Information Certain general service procedures apply, regardless of whether the brakes are vacuum or hydraulically assisted. Only top quality, clean brake fluid should be used. More seals and valves are used with power brake systems than with ordinary brakes, so an inferior brake fluid will do much more damage. For the same reason, be sure all dirt is kept out of the system. Additionally, on models with hydraulic assist brakes, care must be taken not to mix the fluids of the booster hydraulic system and brake hydraulic system as the fluids are not compatible. If the power unit fails, the brakes will still operate, as the conventional brake system is left intact and a power unit is simply added to the existing system. Troubleshooting is then exactly the same up to the power unit. As with conventional hydraulic brakes, a spongy pedal with power brakes is caused by air in the system and grease on the linings will cause the brakes to grab. However, power brakes develop higher line pressure, thus making leaks more critical. Power units do not require adjustment. If there is a problem, the various valves and connections are simply replaced. The only exception is that the power units themselves sometimes have an adjustable connection to the brake pedal or linkage. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Hydraulic Brake Booster > Component Information > Service and Repair > General Service Information > Page 8987 Hydraulic Brake Booster: Service and Repair Bendix Brake Boosters Hydro-Boost Assembly Fig. 2 Removing Accumulator Fig. 3 Typical Hydro-Boost Unit Disassembled DISASSEMBLY 1. Place accumulator compressor tool No. J-26889 or equivalent, around the end of accumulator, and install nut onto stud as shown in Fig. 2, then depress the accumulator with a C-clamp. 2. Remove retainer by using a suitable punch. 3. Release the C-clamp and remove accumulator compressor tool No. J-26889 or equivalent. 4. Remove accumulator, O-ring, retainer, plug and spring as shown in Fig. 3. 5. Remove retainer, output pushrod, baffle, piston return spring and retainer. 6. With a suitable saw, cut off the eyelet of the pedal rod, then remove the boot. 7. Remove nut, bracket and bolts, then separate cover from housing. 8. Remove piston assembly and seals. 9. Remove spool valve, then with a wire hook remove accumulator valve. 10. Remove return line fitting and seal. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Hydraulic Brake Booster > Component Information > Service and Repair > General Service Information > Page 8988 Fig. 4 Spool valve inspection CLEANING/INSPECTION 1. Clean all parts in a suitable solvent being careful to avoid losing small parts. 2. Inspect valve spool and valve spool bore in booster housing for corrosion, nicks, scoring or other damage. Discoloration of the spool or bore, particularly in the grooves, is not harmful. 3. If the valve spool or the spool bore has nicks or scoring that can be felt with a fingernail, particularly on the hands, the spool and housing should be replaced as an assembly, Fig. 4. The clearance between the valve spool and the spool bore of the housing is important. Because of this, the spool and housing make are made as a selective assembly and therefore can only be replaced as an assembly. 4. Inspect the input rod and piston assembly for corrosion, nicks, scoring or excessive wear. If the piston is damaged, the input rod and piston assembly should be replaced. 5. Inspect piston bore in booster housing for corrosion, nicks, scoring or other damage. If the bore is damaged, the valve spool and housing should be replaced as an assembly. ASSEMBLY Lubricate all the seals and metal friction points with power steering fluid. 1. Install return line seal, then the fitting Fig. 3. 2. Install accumulator valve and spool valve into housing. 3. Install seal on piston assembly using seal protector tool No. J-25083 or equivalent. 4. Install seal onto the housing, then install cover and bolts. Torque housing bolts to 22 ft. lbs. 5. Install bracket and nut, then torque to 110 ft. lbs. 6. Install boot, output pushrod, baffle, piston return spring, and retainer using seal protector tool No. 2455l or equivalent. 7. Install retainer, spring, O-ring, and plug, using accumulator compressor tool No. J-26889 or equivalent, and C-clamp. 8. Depress the accumulator, then install the retainer and remove C-clamp. 9. Jam nut from the repair kit onto pedal rod, and install eyelet onto pedal rod. 10. Adjust eyelet to required length. Power Brake Unit, Remove Pump brake pedal several times with engine off to deplete accumulator of fluid. 1. Remove two nuts attaching master cylinder to booster, then move master cylinder away from booster with brake lines attached. 2. Remove hydraulic lines from booster. Plug and cap all lines and outlets. 3. Remove retainer and washer securing booster pushrod to brake pedal arm. 4. Remove nuts attaching booster unit to dash panel. 5. Loosen booster from dash panel and move booster pushrod inboard until it disconnects from brake pedal arm. Remove spring washer from brake pedal arm. 6. Remove booster unit from vehicle. 7. Reverse procedure to install. To fill the Hydro-Boost system, proceed as follows: The power steering fluid and brake fluid cannot be intermixed. If the brake seals contact power steering fluid or steering seals contact brake fluid, seal damage will result. a. Fill power steering pump reservoir to the proper level and allow fluid to remain undisturbed for at least two minutes. b. Start and operate engine momentarily. Add fluid, if necessary. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Hydraulic Brake Booster > Component Information > Service and Repair > General Service Information > Page 8989 c. Repeat filling procedure until fluid level remains constant after operating engine. d. Raise and support front of engine enough so front wheels do not contact floor. e. Turn steering wheel from stop to stop, lightly contacting the stops. Add fluid, if necessary. f. Lower vehicle. g. Start engine and depress brake pedal several times while rotating the steering wheel from stop to stop. h. Switch ignition to OFF position, then pump brake pedal four or five times. i. Check fluid level, add fluid if necessary. j. If fluid is extremely foamy, allow vehicle to stand for a few minutes with the engine not operating. Then, repeat steps g through i. k. Check for presence of air in the oil. Air in the oil will have a milky appearance. Air in the system will also cause the fluid level in the pump to rise when the ignition switch is turned to the OFF position. If the pump will not bleed the air after a few attempts, check power steering system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Hydraulic Brake Booster > Component Information > Service and Repair > General Service Information > Page 8990 Hydraulic Brake Booster: Service and Repair Bleeding Brake Boosters (Bendix Type) 1. Fill oil reservoir to proper level and let stand at least two minutes. 2. Start engine and run momentarily. 3. Add oil as necessary. 4. Repeat above procedure until oil level remains constant after running engine. 5. Raise and support front of vehicle. 6. Turn wheels left and right, lightly contacting stops. 7. Add oil as necessary. 8. Lower vehicle. 9. Start engine and depress brake pedal several times while rotating steering wheel from stop to stop. 10. Turn engine off, then pump brake pedal four or five times to deplete accumulator pressure. 11. Check oil level, filling as necessary. 12. If oil is extremely foamy, allow vehicle to stand several minutes with engine off, then repeat entire procedure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Hydraulic Fluid Accumulator > Component Information > Service and Repair Hydraulic Fluid Accumulator: Service and Repair Fig. 2 Removing Accumulator Do not attempt to repair or apply heat to the accumulator. Before discarding an inoperative accumulator, drill a 1/16 inch diameter hole through the end of the accumulator pan. Do not drill through the piston end. Always wear safety glasses when performing service on the accumulator. 1. Push pedal rod several times to ensure accumulator is depleted. 2. Secure brake booster mounting bracket in a vise with pedal rod facing downward. 3. Place accumulator compressor tool No. J-26889 or equivalent, over master cylinder stud and install retaining nut. 4. Using a C-clamp, depress accumulator can, then insert a punch into hole in housing to unseat retaining ring, Fig. 2. Remove ring from housing using a small screwdriver. If accumulator cannot easily be depressed approximately .10 inch, the accumulator is still charged. This indicates an internal problem with the accumulator valves and the brake booster must be disassembled. 5. Slowly back off C-clamp until tension is relieved, then remove C-clamp, retaining cap and accumulator. 6. Reverse procedure to assemble. Lubricate accumulator can seal with power steering fluid. Ensure accumulator can retaining ring is completely seated in housing groove. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Vacuum Brake Booster > Component Information > Description and Operation > General Description Vacuum Brake Booster: Description and Operation General Description In order to properly service power brake systems, a thorough understanding of the various power assist systems is necessary. These systems provide a mechanical assist, acting to increase the force applied to the master cylinder piston by the driver while decreasing the effort necessary to obtain acceptable stopping performance. Two basic types of power assist mechanisms are used: vacuum assist diaphragm assemblies which use engine vacuum and in some cases vacuum from an external vacuum pump, and hydraulic assist assemblies which use hydraulic pressure developed by an external pump (usually the power steering pump). Vacuum assist units are similar in operation, using vacuum applied to a diaphragm or piston in opposition to atmospheric pressure in order to increase the force applied to the master cylinder piston. However, two types of vacuum assist assemblies are used, the air suspended type and the vacuum suspended type. Air suspended units are under atmospheric pressure until the brakes are applied, then engine vacuum is admitted causing the piston or diaphragm to move and apply force to the master cylinder pushrod. Vacuum suspended types are balanced with engine vacuum until the brake pedal is depressed, allowing atmospheric pressure to unbalance the unit and apply force to the brake system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Vacuum Brake Booster > Component Information > Description and Operation > General Description > Page 8998 Vacuum Brake Booster: Description and Operation Single Diaphragm Type Fig. 1 Exploded View Of Delco-Moraine Single Diaphragm Power Brake Unit Fig. 2 Exploded View Of Delco-Moraine Single Diaphragm Power Piston Assembly DESCRIPTION These power brake units, Figs. 1 and 2, are a combination vacuum-hydraulic brake booster of the vacuum suspended type which use engine intake manifold vacuum and atmospheric pressure for its power. These units consist of a vacuum power section and an hydraulic master cylinder section. The vacuum power section contains a power piston with rolling diaphragm mechanism and power piston return spring. The control valve is made up of an air valve and floating vacuum control valve assembly. The reaction mechanism consists of an hydraulic piston, reaction plate and a series of levers. The valve operating rod, which operates the air valve, projects from the power section and is connected to the brake pedal linkage. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Vacuum Brake Booster > Component Information > Description and Operation > General Description > Page 8999 The hydraulic pushrod operates against the master cylinder piston. A split system (tandem piston) type master cylinder is incorporated into some units. The front half of the master cylinder in the split system operates the rear brakes while the rear half of the master cylinder operates the front brakes. A vacuum check valve, attached to the front vacuum chamber and connected to the intake manifold, traps vacuum in the power unit at the highest level of vacuum. OPERATION As the brakes are applied by the driver, the valve operating rod and control piston move forward in the power piston assembly to compress the valve return spring and bring the poppet valve into contact with the vacuum valve seat in the valve housing to close the vacuum post. Any additional movement of the valve operating rod in the applied direction moves the control valve away from the poppet valve to open the atmospheric port and admit air through the air filter and passages to the chamber at the right of the vacuum power piston assembly. With vacuum on the left side of the diaphragm and atmospheric pressure on the right side of the diaphragm, a force is developed to move the vacuum power piston assembly, hydraulic pushrod, and hydraulic piston to the left to close the compensating port and force hydraulic fluid under pressure through the residual check valve and brake tubes into the brake wheel cylinders. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Vacuum Brake Booster > Component Information > Description and Operation > General Description > Page 9000 Vacuum Brake Booster: Description and Operation Tandem Diaphragm Type Fig. 6 Exploded View Of Delco-Moraine Tandem Power Brake Unit Fig. 7 Exploded View Of Delco-Moraine Tandem Diaphragm Power Piston Assembly DESCRIPTION These units, Figs. 6 and 7, have a vacuum power chamber that consists of a front and rear shell, a housing divider, front and rear diaphragm and plate assemblies, an hydraulic pushrod and a diaphragm return spring. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Vacuum Brake Booster > Component Information > Description and Operation > General Description > Page 9001 OPERATION As the brakes are applied by the driver, the valve operating rod and control piston move forward in the power piston assembly to compress the valve return spring and bring the poppet valve into contact with the vacuum valve seat in the valve housing to close the vacuum post. Any additional movement of the valve operating rod in the applied direction moves the control valve away from the poppet valve to open the atmospheric port and admit air through the air filter and passages to the chamber at the right of the vacuum power piston assembly. With vacuum on the left side of the diaphragm and atmospheric pressure on the right side of the diaphragm, a force is developed to move the vacuum power piston assembly, hydraulic pushrod, and hydraulic piston to the left to close the compensating port and force hydraulic fluid under pressure through the residual check valve and brake tubes into the brake wheel cylinders. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Vacuum Brake Booster > Component Information > Testing and Inspection > Brakes Grab Vacuum Brake Booster: Testing and Inspection Brakes Grab 1. Faulty control valve. 2. Broken or damaged hydraulic brake lines. 3. Faulty master cylinder seals. 4. Cracked master cylinder casting. 5. Air in hydraulic system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Vacuum Brake Booster > Component Information > Testing and Inspection > Brakes Grab > Page 9004 Vacuum Brake Booster: Testing and Inspection Hard Pedal 1. Internal vacuum leak. 2. Faulty control valve. 3. Broken or damaged hydraulic brake lines. 4. Collapsed or damaged vacuum hose. 5. Plugged or loose vacuum fitting. 6. Bad stud welds on front or rear housing on power head. 7. Faulty booster diaphragm. 8. Restricted air filter element. 9. Worn or distorted reaction plate or levers. 10. Cracked or broken power pistons or retainers. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Vacuum Brake Booster > Component Information > Testing and Inspection > Brakes Grab > Page 9005 Vacuum Brake Booster: Testing and Inspection Slow or No Release 1. Faulty pushrod adjustment. 2. Binding linkage. 3. Blocked passage in power piston. 4. Air valve sticking shut. 5. Broken piston return spring or air valve spring. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Vacuum Brake Booster > Component Information > Service and Repair > General Service Information Vacuum Brake Booster: Service and Repair General Service Information Certain general service procedures apply, regardless of whether the brakes are vacuum or hydraulically assisted. Only top quality, clean brake fluid should be used. More seals and valves are used with power brake systems than with ordinary brakes, so an inferior brake fluid will do much more damage. For the same reason, be sure all dirt is kept out of the system. Additionally, on models with hydraulic assist brakes, care must be taken not to mix the fluids of the booster hydraulic system and brake hydraulic system as the fluids are not compatible. If the power unit fails, the brakes will still operate, as the conventional brake system is left intact and a power unit is simply added to the existing system. Troubleshooting is then exactly the same up to the power unit. As with conventional hydraulic brakes, a spongy pedal with power brakes is caused by air in the system and grease on the linings will cause the brakes to grab. However, power brakes develop higher line pressure, thus making leaks more critical. Power units do not require adjustment. If there is a problem, the various valves and connections are simply replaced. The only exception is that the power units themselves sometimes have an adjustable connection to the brake pedal or linkage. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Vacuum Brake Booster > Component Information > Service and Repair > General Service Information > Page 9008 Vacuum Brake Booster: Service and Repair Booster Assembly Single Diaphragm Type Fig. 3 Exploded View Of Delco-Moraine Single Diaphragm Brake Booster Components Fig. 4 Brake Booster Holding Fixture DISASSEMBLY 1. Remove boot, silencer, vacuum check valve, grommet and front housing seal, Fig. 3. 2. Scribe a line across front and rear housing, then mount brake booster to brake mounting fixture tool No. J 23456 or equivalent, Fig. 4. 3. Turn fixture handle counterclockwise to unlock housings. 4. Remove return spring, power piston assembly and power piston bearing from rear housing, Fig. 3. 5. Remove reaction body retainer, piston rod, reaction retainer and filter, Fig. 3. 6. Remove power piston and pushrod assembly as follows: a. While holding the pushrod down against a hard surface, grasp outside edge of diaphragm support and diaphragm, Fig. 3. b. Use a slight force to dislodge diaphragm retainer, Fig. 3. 7. Remove diaphragm from diaphragm support, Fig. 3. 8. Inspect all parts for corrosion, nicks, cracks, cuts, scoring, distortion or excessive wear. Replace as necessary. 9. Clean all parts in denatured alcohol. Dry with clean compressed air. Do not immerse power piston and pushrod assembly in alcohol. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Vacuum Brake Booster > Component Information > Service and Repair > General Service Information > Page 9009 Fig. 5 Brake Booster Lock Tab & Staking Positions ASSEMBLY 1. Lubricate inside diameter of diaphragm lip with a thin layer of silicone grease, then install diaphragm into the diaphragm support, Fig. 3. 2. Install diaphragm and diaphragm support onto power piston and pushrod assembly. 3. Install new diaphragm retainer. Ensure retainer is fully seated. 4. Install filter, reaction retainer, piston rod and reaction body retainer. 5. Apply silicone grease to the power piston bearing and install it into the rear housing, then install return spring. 6. Mount housings to holding fixture and turn fixture handle in a clockwise direction to lock the front and rear housings. 7. Stake housing in locations shown, Fig. 5. Do not stake a tab that has been staked previously. 8. Lubricate inside and outside edges of grommet and front housing seal, then install grommet and seal. 9. Install vacuum check valve, silencer and boot. 10. Ensure piston rod depth is within specifications using gauge tool No. J-37839 or equivalent. Tandem Diaphragm Type Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Vacuum Brake Booster > Component Information > Service and Repair > General Service Information > Page 9010 Fig. 8 Exploded View Of Delco-Moraine Tandem Diaphragm Brake Booster Components Brake Booster Holding Fixture DISASSEMBLE 1. Remove boot, silencer, vacuum check valve, grommet and front housing seal, Fig. 8. 2. Scribe a line across front and rear housing, then install brake booster to brake mounting fixture tool No. J-23456 or equivalent, Fig. 6. 3. Turn fixture handle to unlock housings. 4. Remove return spring, power piston assembly and power piston bearing from rear housing, Fig. 8. 5. Remove piston rod, reaction retainer and power head silencer. 6. Remove power piston and pushrod assembly as follows: a. While holding the pushrod down against a hard surface, grasp outside edge of diaphragm support and diaphragm. b. Use a slight force to dislodge diaphragm retainer. 7. Remove primary diaphragm and primary support plate from housing divider. 8. Remove primary diaphragm from primary support plate. 9. Remove secondary diaphragm and secondary support plate from housing divider. 10. Remove secondary piston bearing from housing divider. 11. Remove secondary diaphragm from secondary support plate. 12. Remove reaction body retainer, reaction body, reaction disc and reaction piston from reaction body. 13. Remove air valve spring and reaction bumper from end of air valve pushrod. 14. Remove retaining ring from air valve pushrod assembly. 15. Remove air valve pushrod assembly by inserting a screwdriver through the pushrod eyelet and pulling pushrod assembly straight out. 16. Remove filter, retainer and O-ring from air valve pushrod assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Vacuum Brake Booster > Component Information > Service and Repair > General Service Information > Page 9011 17. Inspect all parts for corrosion, nicks, cracks, cuts, scoring, distortion or excessive wear. Replace as necessary. 18. Clean all parts in denatured alcohol and dry with clean compressed air. Do not immerse power piston and pushrod assembly in alcohol. Brake Booster Lock Tab & Staking Positions ASSEMBLE 1. Install lubricated O-ring onto air valve pushrod assembly. 2. Install air valve pushrod into the power piston. 3. Install retainer and seat. 4. Install filter over pushrod eyelet and into power piston. 5. Install retaining ring onto air valve pushrod assembly. 6. Install reaction bumper, air valve spring, reaction piston and reaction disc onto reaction body. 7. Install reaction body, then reaction body retainer. 8. Lubricate inside diameter of secondary diaphragm lip, inside diameter of primary diaphragm lip and the secondary piston bearing with a thin layer of silicone grease. 9. Install secondary diaphragm into the secondary support plate, Fig. 8. 10. Install secondary diaphragm and secondary support plate over the power piston and pushrod assembly. 11. Install secondary piston bearing into housing divider with flat surface of bearing on the same side as the six raised lugs on the divider. 12. Install secondary piston bearing and housing divider over power piston assembly and pushrod. 13. Install primary diaphragm into the primary support plate, Fig. 8. 14. Fold primary diaphragm up away from the primary support plate, then install primary diaphragm and support plate over power piston and pushrod assembly. 15. Fold primary diaphragm back into position and pull the outside edge of diaphragm over formed flange of housing divider. 16. Install new diaphragm retainer. Ensure retainer is fully seated. 17. Install silencer, reaction retainer and piston rod. 18. Lubricate inside and outside diameters of primary piston bearings with silicone grease. 19. Install primary piston bearing into rear housing. 20. Install power piston assembly into rear housing, then the return spring. 21. Mount housing to holding fixture and turn fixture handle to lock the front and rear housings, Fig. 6. 22. Stake housing in locations shown, Fig. 7. Do not stake a tab that has been staked previously. 23. Lubricate inside and outside edges of grommet and front housing seal, then install grommet and seal. 24. Install vacuum check valve, silencer and boot. 25. Ensure piston rod depth is within specifications using gauge tool No. J-37839 or equivalent. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Power Brake Assist > Vacuum Brake Booster > Component Information > Service and Repair > General Service Information > Page 9012 Vacuum Brake Booster: Service and Repair Power Brake Unit 1. Remove vacuum hose from check valve and master cylinder retaining nuts. 2. Pull master cylinder forward so it clears mounting studs and move to one side. Support cylinder to avoid stress on hydraulic lines. 3. Remove power unit to dash nuts. 4. Remove brake pedal pushrod retainer and disconnect pushrod from pin. 5. Remove power brake unit from vehicle. 6. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Relays and Modules - Brakes and Traction Control > ABS Main Relay > Component Information > Locations ABS Main Relay: Locations The relay is located inside the Brake Pressure Modulator Valve (BPMV) and cannot be serviced. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Relays and Modules - Brakes and Traction Control > Electronic Brake Control Module > Component Information > Locations Electronic Brake Control Module: Locations The Electronic Brake Control Unit (EBCM) is mounted to the top of the Brake Pressure Modulator Valve (BPMV) and is housed in aluminum with a black plastic top. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Relays and Modules - Brakes and Traction Control > Electronic Brake Control Module > Component Information > Locations > Page 9020 Electronic Brake Control Module: Service and Repair Fig. 226 EBCM Replacement. 1. Disconnect battery ground cable, then raise and support vehicle. 2. Remove bolts securing shield (if equipped) and BPMV to EHCU mounting bracket, Fig. 226, then disconnect (EBCM) Electronic Brake Control Module electrical connectors. 3. Remove Torx bolts securing EBCM to BPMV, then separate EBCM from BPMV. Do not pry on components to separate. 4. Reverse procedure to install, noting the following: a. Install a new EBCM gasket and mounting bolts. Do not use any gasket sealant. b. Torque EBCM to BPMV bolts to 39 inch lbs. in a crisscross pattern. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Sensors and Switches - Brakes and Traction Control > Brake Fluid Pressure Sensor/Switch > Component Information > Locations Brake Fluid Pressure Sensor/Switch: Locations Behind I/P Compartment Box on HVAC Plenum Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Sensors and Switches - Brakes and Traction Control > Braking Sensor/Switch > Component Information > Service and Repair Braking Sensor/Switch: Service and Repair Stop Lamp Switch Remove or Disconnect 1. Negative battery cable. 2. Disable SIR. 3. Retainer from brake pedal pin. Use snap ring pliers. 4. Switch by unsnapping from pushrod. 5. Electrical connector from switch. Install or Connect 1. Electrical connector into switch. 2. Switch by snapping it onto pushrod. 3. Retainer onto brake pedal pin. Use 11mm (7/16 inch) socket to push new clip on pin. 4. Negative battery cable. 5. Enable SIR. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Technical Service Bulletins > Customer Interest: > 02-05-25-006B > Jan > 06 > Brakes - Low Speed (Below 5 MPH) ABS Activation Wheel Speed Sensor: Customer Interest Brakes - Low Speed (Below 5 MPH) ABS Activation Bulletin No.: 02-05-25-006B Date: January 05, 2006 TECHNICAL Subject: Antilock Brake (ABS) Activation At Low Speeds (Clean Wheel Speed Sensor Mounting Surface) Models: 1999-2000 Cadillac Escalade 1995-1999 Chevrolet Silverado (Old Style) 1995-2000 Chevrolet Suburban, Tahoe (Old Style) 1995-2003 Chevrolet Astro Van, Blazer, S10 1995-1999 GMC Sierra (Old Style) 1995-2000 GMC Yukon, Yukon XL (Old Style) 1995-2001 GMC Envoy, Jimmy 1995-2003 GMC Safari Van, Sonoma 1995-2001 Oldsmobile Bravada Supercede: This bulletin is being revised to update the correction and warranty information. Please discard Corporate Bulletin Number 02-05-25-006A (Section 05 - Brakes). Condition Some customers may comment on ABS activation at low speeds, usually below 8 km/h (5 mph). Upon investigation, the technician will find no DTCs set. Cause The cause of this condition may be an increased air gap between the wheel speed sensor and the hub reluctor ring due to rust and debris built up on the sensor mounting surface. Correction Measure AC voltage and clean wheel speed sensor mounting surfaces. 1. Raise the vehicle on a hoist. 2. Disconnect both the front wheel speed sensor harness connectors. 3. Place a DVM across the terminals of each sensor connector. 4. Rotate the wheel with hand speed and measure the ACmV's. The reading should be at least 350 ACmV's. 5. If the reading is between 200 and 350 ACmV's, remove the wheel, caliper and rotor in order to gain access to the speed sensor. 6. Remove the wheel speed sensor and plug the hole to prevent debris from falling into the hub during service. 7. Clean the wheel speed sensor mounting surface using a wire brush, sand paper, emery cloth, ScotchBrite(TM) or other suitable material. Be sure to thoroughly clean the wheel speed sensor surface. There should be no rust or corrosion. 8. Check the sensor head to determine if it has been warped/distorted due to the corrosion build up or other causes. Check the mounting surface on the sensor head for flatness by placing it on the edge of a metal machinists scale or other suitable straight edge to measure the flatness. Check the sensor for flatness in multiple (minimum 3) positions/directions. If the sensor head is distorted, replace the sensor. 9. Apply (spray) two thin coats of the specified rust penetrating lubricant (corrosion inhibitor) to the complete sensor mounting surface on the bearing hub. Allow to dry for 3-5 minutes between coats. Use ONLY Rust Penetrating Lubricant, P/N 89022217 (Canadian P/N 89022218). 10. When the corrosion inhibitor is dry to the touch (about 10 minutes), apply a thin layer of bearing grease to the hub surface and sensor 0-ring prior to sensor installation. Use ONLY Wheel Bearing Lubricant, P/N 01051344 (Canadian P/N 993037). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Technical Service Bulletins > Customer Interest: > 02-05-25-006B > Jan > 06 > Brakes - Low Speed (Below 5 MPH) ABS Activation > Page 9036 11. Install either the original sensor or a new one in the hub and secure the sensor. Ensure that the sensor is seated flush against the hub. 12. Install the rotor, the caliper and the wheel. 13. Place the DVM across the sensor terminals and recheck the voltage while rotating the wheel by hand. The voltage should now read at least 350 ACmV's. Parts Information Warranty Information For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 02-05-25-006B > Jan > 06 > Brakes - Low Speed (Below 5 MPH) ABS Activation Wheel Speed Sensor: All Technical Service Bulletins Brakes - Low Speed (Below 5 MPH) ABS Activation Bulletin No.: 02-05-25-006B Date: January 05, 2006 TECHNICAL Subject: Antilock Brake (ABS) Activation At Low Speeds (Clean Wheel Speed Sensor Mounting Surface) Models: 1999-2000 Cadillac Escalade 1995-1999 Chevrolet Silverado (Old Style) 1995-2000 Chevrolet Suburban, Tahoe (Old Style) 1995-2003 Chevrolet Astro Van, Blazer, S10 1995-1999 GMC Sierra (Old Style) 1995-2000 GMC Yukon, Yukon XL (Old Style) 1995-2001 GMC Envoy, Jimmy 1995-2003 GMC Safari Van, Sonoma 1995-2001 Oldsmobile Bravada Supercede: This bulletin is being revised to update the correction and warranty information. Please discard Corporate Bulletin Number 02-05-25-006A (Section 05 - Brakes). Condition Some customers may comment on ABS activation at low speeds, usually below 8 km/h (5 mph). Upon investigation, the technician will find no DTCs set. Cause The cause of this condition may be an increased air gap between the wheel speed sensor and the hub reluctor ring due to rust and debris built up on the sensor mounting surface. Correction Measure AC voltage and clean wheel speed sensor mounting surfaces. 1. Raise the vehicle on a hoist. 2. Disconnect both the front wheel speed sensor harness connectors. 3. Place a DVM across the terminals of each sensor connector. 4. Rotate the wheel with hand speed and measure the ACmV's. The reading should be at least 350 ACmV's. 5. If the reading is between 200 and 350 ACmV's, remove the wheel, caliper and rotor in order to gain access to the speed sensor. 6. Remove the wheel speed sensor and plug the hole to prevent debris from falling into the hub during service. 7. Clean the wheel speed sensor mounting surface using a wire brush, sand paper, emery cloth, ScotchBrite(TM) or other suitable material. Be sure to thoroughly clean the wheel speed sensor surface. There should be no rust or corrosion. 8. Check the sensor head to determine if it has been warped/distorted due to the corrosion build up or other causes. Check the mounting surface on the sensor head for flatness by placing it on the edge of a metal machinists scale or other suitable straight edge to measure the flatness. Check the sensor for flatness in multiple (minimum 3) positions/directions. If the sensor head is distorted, replace the sensor. 9. Apply (spray) two thin coats of the specified rust penetrating lubricant (corrosion inhibitor) to the complete sensor mounting surface on the bearing hub. Allow to dry for 3-5 minutes between coats. Use ONLY Rust Penetrating Lubricant, P/N 89022217 (Canadian P/N 89022218). 10. When the corrosion inhibitor is dry to the touch (about 10 minutes), apply a thin layer of bearing grease to the hub surface and sensor 0-ring prior to sensor installation. Use ONLY Wheel Bearing Lubricant, P/N 01051344 (Canadian P/N 993037). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 02-05-25-006B > Jan > 06 > Brakes - Low Speed (Below 5 MPH) ABS Activation > Page 9042 11. Install either the original sensor or a new one in the hub and secure the sensor. Ensure that the sensor is seated flush against the hub. 12. Install the rotor, the caliper and the wheel. 13. Place the DVM across the sensor terminals and recheck the voltage while rotating the wheel by hand. The voltage should now read at least 350 ACmV's. Parts Information Warranty Information For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheel Speed Sensor: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not Fuel Gauge Sender: All Technical Service Bulletins Instruments - Fuel Gauge Indicates Empty When Not File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-03A Date: June, 1998 Subject: Fuel Gauge Indicates Empty with 7-8 Gallons (30 Liters) Left in Tank (Replace Fuel Level Sensor Float Arm Assembly) Models: 1995-97 Chevrolet and GMC C/K 4 Door Models Built Prior to VIN Breakpoints: Models VIN Breakpoints Chevrolet VJ355982 GMC VJ724930 This bulletin is being revised to change the labor operation number. Please discard Corporate Bulletin Number 76-83-03 (Section 8 - Chassis/Body Electrical). Condition Some owners may comment that the fuel gauge indicates empty after only going 200 to 250 miles, and they are only able to put approximately 23 gallons or less of fuel in the 30 gallon tank. Cause The Fuel Level Indication System was designed with excessive empty reserve. The Fuel Level Sender will be labeled with Broadcast code "TCB", (see Figure 1). Vehicles built after December 14, 1996, have the revised Float Arm Assembly. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheel Speed Sensor: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not > Page 9048 Following the procedure described in Section 8A of the Service Manual, remove the Sender Assembly and replace the original Float and Arm with P/N 25312833 (see Figure 2). Reinstall the Sender Assembly and Tank. Parts Information P/N Description Qty 25312833 Float Kit, Fuel Level Sensor 1 The part is currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time L1225 Sender Use published Assembly, Fuel Labor Operation (Tank Unit) - Time Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheel Speed Sensor: > 76-83-05 > Sep > 97 > Instruments - Excessive Fuel Gauge Fluctuation Fuel Gauge Sender: All Technical Service Bulletins Instruments - Excessive Fuel Gauge Fluctuation File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-05 Date: September, 1997 Subject: Excessive Fuel Gauge Fluctuation (Install Fuel Level Damper Kit) Models: 1995-97 Chevrolet and GMC C/K 4 Door Utility Models Condition Some owners may comment about excessive fuel gauge needle fluctuation when making turns or braking with less than a half tank of fuel. Correction Install fuel level damper module kit P/N 12167652 following the procedure described on the instruction sheets included with the kit. Parts Information P/N Description Qty 12167652 Module Kit, Fuel Level Damper 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time N4844 Module, Anti-slosh - Install 0.8 hr Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheel Speed Sensor: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not > Page 9058 Following the procedure described in Section 8A of the Service Manual, remove the Sender Assembly and replace the original Float and Arm with P/N 25312833 (see Figure 2). Reinstall the Sender Assembly and Tank. Parts Information P/N Description Qty 25312833 Float Kit, Fuel Level Sensor 1 The part is currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time L1225 Sender Use published Assembly, Fuel Labor Operation (Tank Unit) - Time Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Technical Service Bulletins > Page 9063 Wheel Speed Sensor: Specifications 2WD Sensor Resistance 1575 to 2420 ohms at -40 to 40 deg F 1980 to 2800 ohms at 41 to 110 deg F 2250 to 3280 ohms at 111 to 200 deg F 2750 to 3850 ohms at 201 to 302 deg F 4WD Sensor Resistance 1900 to 2950 ohms at -40 to 40 deg F 2420 to 3450 ohms at 41 to 110 deg F 2610 to 4100 ohms at 111 to 200 deg F 3320 to 4760 ohms at 201 to 302 deg F Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Locations > LH Wheel Speed Sensor: Locations LH front At LH front Wheel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Locations > LH > Page 9066 Wheel Speed Sensor: Locations RH front At RH front Wheel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Service and Repair > Front Wheel Speed Sensor Wheel Speed Sensor: Service and Repair Front Wheel Speed Sensor 1. Raise and support vehicle, then remove wheel and tire assembly. 2. Disconnect brake caliper assembly and position aside. 3. Remove hub and rotor assembly. 4. Disconnect wheel sensor electrical connector. 5. Remove sensor wire form upper control arm clip. 6. Remove sensor and splash shield assembly attaching bolts, then remove sensor. 7. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Brakes and Traction Control > Sensors and Switches - Brakes and Traction Control > Wheel Speed Sensor > Component Information > Service and Repair > Front Wheel Speed Sensor > Page 9069 Wheel Speed Sensor: Service and Repair Rear Wheel Speed Sensor Fig. 58 Rear Wheel Speed Sensor 1. Raise and support vehicle, then remove wheel and tire assembly. 2. Remove brake drum. 3. Remove primary brake shoe. 4. Disconnect sensor electrical connector. 5. Remove sensor wire from rear axle clip. 6. Remove speed sensor attaching bolts, Fig. 58, then remove sensor by pulling wire through hole in backing plate. 7. Reverse procedure to install. Torque speed sensor attaching bolts to 26 ft. lbs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder Technical Service Bulletin # 73-01-09 Date: 971001 Starting - Revised Procedures for Inop Ignition Cylinder File In Section: 0 - General Information Bulletin No.: 73-01-09 Date: October, 1997 INFORMATION Subject: New Tumblers for Cylinder Recoding, Revised Repair Procedures for Inoperative Ignition Cylinders (Seized/Won't Rotate), Labor Operation/Time Allowances Models: 1995-97 Buick Skylark, Riviera 1995-97 Chevrolet Cavalier 1997 Chevrolet Corvette, Malibu, Venture 1995-97 Oldsmobile Achieva 1997 Oldsmobile Aurora, Cutlass, Silhouette 1995-97 Pontiac Grand Am, Sunfire 1997 Pontiac Grand Prix, Trans Sport 1995-97 Chevrolet and GMC C/K, S/T Models 1996-97 Chevrolet and GMC G, M/L Vans 1996-97 Oldsmobile Bravada The information in this bulletin concerns new designed tumblers for recoding lock cylinders that use double sided reversible keys, revised procedures for servicing ignition lock cylinders that are seized or not able to rotate and revised labor time guide information and allowances. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 9081 The existing labor operation (E7200) has been changed to include "Add" conditions for cylinders that will not rotate. New Tumblers New tumblers are available from GMSPO for recoding lock cylinders that use double-sided reversible keys. These new tumblers should be used immediately and information about the disposition of original tumblers will be provided by GMSPO. Figure 1 shows the new tumbler profile. The shaded area was part of the original tumbler profile, and is removed on the new tumblers. The new part numbers for the tumblers are as follows: Part No. 2852732 = Tumbler # 1 Part No. 2852733 = Tumbler # 2 Part No. 2852734 = Tumbler # 3 Part No. 2852735 = Tumbler # 4 Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. New Procedures For Seized/Won't Rotate Column Mounted Ign. CYL. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 9082 A. On G, J and N Models: DO NOT REMOVE THE STEERING COLUMN as indicated in the Service Manual procedure. 1. Remove the tilt lever, upper and lower column covers. 2. Drill hole in module housing as indicated in the illustration using a short drill bit (1/8" followed by 9/32") and 90 degree drill motor or go degree drill attachment to break or access the retaining spring for the lock cylinder button, see Figure 2. 3. Using a pick or needle nose pliers, remove the retaining spring from the hole. 4. Using pliers, grasp and remove the retaining button for the cylinder. 5. Remove the cylinder from the housing. 6. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 7. Install the new cylinder and reinstall the steering column components. B. On U, W, and light duty trucks, follow the Service Manual procedure for keys missing, or cylinders won't rotate. Procedure: Instrument Panel Mounted Switches Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 9083 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder Technical Service Bulletin # 73-01-09 Date: 971001 Starting - Revised Procedures for Inop Ignition Cylinder File In Section: 0 - General Information Bulletin No.: 73-01-09 Date: October, 1997 INFORMATION Subject: New Tumblers for Cylinder Recoding, Revised Repair Procedures for Inoperative Ignition Cylinders (Seized/Won't Rotate), Labor Operation/Time Allowances Models: 1995-97 Buick Skylark, Riviera 1995-97 Chevrolet Cavalier 1997 Chevrolet Corvette, Malibu, Venture 1995-97 Oldsmobile Achieva 1997 Oldsmobile Aurora, Cutlass, Silhouette 1995-97 Pontiac Grand Am, Sunfire 1997 Pontiac Grand Prix, Trans Sport 1995-97 Chevrolet and GMC C/K, S/T Models 1996-97 Chevrolet and GMC G, M/L Vans 1996-97 Oldsmobile Bravada The information in this bulletin concerns new designed tumblers for recoding lock cylinders that use double sided reversible keys, revised procedures for servicing ignition lock cylinders that are seized or not able to rotate and revised labor time guide information and allowances. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 9089 The existing labor operation (E7200) has been changed to include "Add" conditions for cylinders that will not rotate. New Tumblers New tumblers are available from GMSPO for recoding lock cylinders that use double-sided reversible keys. These new tumblers should be used immediately and information about the disposition of original tumblers will be provided by GMSPO. Figure 1 shows the new tumbler profile. The shaded area was part of the original tumbler profile, and is removed on the new tumblers. The new part numbers for the tumblers are as follows: Part No. 2852732 = Tumbler # 1 Part No. 2852733 = Tumbler # 2 Part No. 2852734 = Tumbler # 3 Part No. 2852735 = Tumbler # 4 Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. New Procedures For Seized/Won't Rotate Column Mounted Ign. CYL. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 9090 A. On G, J and N Models: DO NOT REMOVE THE STEERING COLUMN as indicated in the Service Manual procedure. 1. Remove the tilt lever, upper and lower column covers. 2. Drill hole in module housing as indicated in the illustration using a short drill bit (1/8" followed by 9/32") and 90 degree drill motor or go degree drill attachment to break or access the retaining spring for the lock cylinder button, see Figure 2. 3. Using a pick or needle nose pliers, remove the retaining spring from the hole. 4. Using pliers, grasp and remove the retaining button for the cylinder. 5. Remove the cylinder from the housing. 6. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 7. Install the new cylinder and reinstall the steering column components. B. On U, W, and light duty trucks, follow the Service Manual procedure for keys missing, or cylinders won't rotate. Procedure: Instrument Panel Mounted Switches Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 9091 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Page 9092 Ignition Switch Lock Cylinder: Service and Repair The procedure has been updated by TSB# 73-01-09 Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > Customer Interest: > 01-07-30-021 > May > 01 > Park/Neutral Switch - Connector Hard to Remove Neutral Safety Switch: Customer Interest Park/Neutral Switch - Connector Hard to Remove File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-021 Date: May, 2001 TECHNICAL Subject: Park/Neutral Position Switch Connector Cannot Be Removed (Replace Switch and Connectors) Models: 1997-2001 Chevrolet Camaro, Corvette 1997-2001 Pontiac Firebird 1995-2001 Chevrolet and GMC S/T Models 1996-2001 Chevrolet and GMC C/K, M/L, G and P Models 1996-2001 Oldsmobile Bravada with 4L60E (M30), 4L65E (M32), 4LBOE (MT1) or Allison LCT (M74) Automatic Transmission This bulletin is being revised to change a labor operation number, add models, model years and transmission designations. Please discard Corporate Bulletin Number 83-71-10A (Section 7 Transmission). Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer concerns, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to ensure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to ensure water-tight connections. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > Customer Interest: > 01-07-30-021 > May > 01 > Park/Neutral Switch - Connector Hard to Remove > Page 9101 For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Neutral Safety Switch: > 01-07-30-021 > May > 01 > Park/Neutral Switch - Connector Hard to Remove Neutral Safety Switch: All Technical Service Bulletins Park/Neutral Switch - Connector Hard to Remove File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-021 Date: May, 2001 TECHNICAL Subject: Park/Neutral Position Switch Connector Cannot Be Removed (Replace Switch and Connectors) Models: 1997-2001 Chevrolet Camaro, Corvette 1997-2001 Pontiac Firebird 1995-2001 Chevrolet and GMC S/T Models 1996-2001 Chevrolet and GMC C/K, M/L, G and P Models 1996-2001 Oldsmobile Bravada with 4L60E (M30), 4L65E (M32), 4LBOE (MT1) or Allison LCT (M74) Automatic Transmission This bulletin is being revised to change a labor operation number, add models, model years and transmission designations. Please discard Corporate Bulletin Number 83-71-10A (Section 7 Transmission). Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer concerns, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to ensure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to ensure water-tight connections. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Neutral Safety Switch: > 01-07-30-021 > May > 01 > Park/Neutral Switch - Connector Hard to Remove > Page 9107 For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Neutral Safety Switch: > 83-71-10 > May > 98 > A/T - Park/Neutral Switch Connector Cannot Be Removed Neutral Safety Switch: All Technical Service Bulletins A/T - Park/Neutral Switch Connector Cannot Be Removed File In Section: 7 - Transmission Bulletin No.: 83-71-10 Date: May, 1998 Subject: Park (Neutral Position Switch Connector Cannot be Removed (Replace Switch and Connectors) Models: 1997-98 Chevrolet Corvette 1995-98 Chevrolet and GMC S/T Models 1996-98 Chevrolet and GMC M/L, P Models 1996-99 Chevrolet and GMC C/K, G Models 1996-98 Oldsmobile Bravada Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer conditions, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to insure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to insure water-tight connections. Parts Information P/N Description 12450016 Switch 15305925 4-Way Connector Assembly 15305887 7-Way Connector Assembly Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Other Service Bulletins for Neutral Safety Switch: > 83-71-10 > May > 98 > A/T - Park/Neutral Switch Connector Cannot Be Removed Neutral Safety Switch: All Technical Service Bulletins A/T - Park/Neutral Switch Connector Cannot Be Removed File In Section: 7 - Transmission Bulletin No.: 83-71-10 Date: May, 1998 Subject: Park (Neutral Position Switch Connector Cannot be Removed (Replace Switch and Connectors) Models: 1997-98 Chevrolet Corvette 1995-98 Chevrolet and GMC S/T Models 1996-98 Chevrolet and GMC M/L, P Models 1996-99 Chevrolet and GMC C/K, G Models 1996-98 Oldsmobile Bravada Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer conditions, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to insure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to insure water-tight connections. Parts Information P/N Description 12450016 Switch 15305925 4-Way Connector Assembly 15305887 7-Way Connector Assembly Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Locations > With 4L60-E Transmission Electronic 4-speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Locations > With 4L60-E Transmission > Page 9119 Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions Neutral Safety Switch: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9122 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9123 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9124 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9125 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9126 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9127 Neutral Safety Switch: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9128 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9129 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9130 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9131 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9132 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9133 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9134 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9135 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9136 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9137 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9138 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9139 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9140 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9141 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9142 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9143 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9144 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9145 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9146 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9147 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9148 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9149 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9150 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9151 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9152 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Sensors and Switches - Starting and Charging > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9153 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Relays and Modules - Starting and Charging > Starter Relay > Component Information > Locations Starter Relay: Locations In Underhood Fuse - Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions Battery Cable: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9163 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9164 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9165 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9166 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9167 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9168 Battery Cable: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9169 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9170 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9171 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9172 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9173 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9174 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9175 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9176 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9177 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9178 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9179 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9180 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9181 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9182 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9183 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9184 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9185 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9186 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9187 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9188 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9189 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9190 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9191 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9192 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9193 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Battery > Battery Cable > Component Information > Diagrams > Diagram Information and Instructions > Page 9194 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Technical Service Bulletins > Tools - Released for CS Generator Diagnosis Alternator: Technical Service Bulletins Tools - Released for CS Generator Diagnosis File In Section: 6 - Engine Bulletin No.: 83-64-09 Date: March, 1998 INFORMATION Subject: New Tool J 41450-B, Released for CS Generator Diagnosis Models: 1988-98 Passenger Cars and Light Trucks with CS-Series Generators A new CS-Series Generator Tester, J 41450-B, has been sent to all dealers as part of the Essential Tool Package. This tool will work on all CS-Series generators for past model years. The tool is shown in Figure 1. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Technical Service Bulletins > Tools - Released for CS Generator Diagnosis > Page 9200 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Technical Service Bulletins > Tools - Released for CS Generator Diagnosis > Page 9201 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Technical Service Bulletins > Tools - Released for CS Generator Diagnosis > Page 9202 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Technical Service Bulletins > Tools - Released for CS Generator Diagnosis > Page 9203 Generator Not Operating Properly The charts shown can be used in place of the diagnostic procedures in previous Service Manuals when this new tool is used. This information will be included in the 1999 Service Manual. Inspect the following before testing the generator: ^ The battery. Make sure the vehicle battery is in good condition and fully charged. Refer to Battery Load Test. ^ The built in hydrometer in the battery. The green eye must be showing in the hydrometer. ^ The voltage across the battery terminals with all the loads OFF should be above 12 V. Refer to Battery Load Test. ^ Make sure the battery connections are clean and tight. ^ The drive belt for damage or looseness. ^ The wiring harness at the generator. Make sure the harness connector is tight and latched. Make sure the output terminal of the generator is connected to the vehicle battery (positive) generator lead. ^ All the charging system related fuses and electrical connections for damage or looseness. Refer to the starter and charging system schematics. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Technical Service Bulletins > Page 9204 Alternator: Specifications Model ................................................................................................................................................... .................................................................. 10480022 Rated Hot Output, Amps ..................................................................................................................... ............................................................................. 124 Model ................................................................................................................................................... .................................................................. 10480023 Rated Hot Output, Amps ..................................................................................................................... ............................................................................. 145 Model ................................................................................................................................................... .................................................................. 10479959 Rated Hot Output, Amps ..................................................................................................................... ............................................................................. 124 Model ................................................................................................................................................... .................................................................. 10480094 Rated Hot Output, Amps ..................................................................................................................... ............................................................................. 100 Model ................................................................................................................................................... .................................................................. 10480084 Rated Hot Output, Amps ..................................................................................................................... ............................................................................. 105 Model ................................................................................................................................................... .................................................................. 10480086 Rated Hot Output, Amps ..................................................................................................................... ............................................................................. 100 Model ................................................................................................................................................... .................................................................. 10480099 Rated Hot Output, Amps ..................................................................................................................... ............................................................................. 105 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Locations > Component Locations Battery Wiring (Typical) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Locations > Component Locations > Page 9207 Engine Side, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions Alternator: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9210 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9211 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9212 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9213 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9214 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9215 Alternator: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9216 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9217 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9218 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9219 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9220 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9221 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9222 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9223 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9224 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9225 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9226 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9227 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9228 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9229 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9230 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9231 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9232 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9233 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9234 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9235 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9236 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9237 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9238 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9239 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9240 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Diagram Information and Instructions > Page 9241 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Page 9242 Alternator: Application and ID Engine ................................................................................................................................................. .............................................................................. All Alternator Model .............................................. .............................................................................................................................................................. [01] [01] Less auxiliary heat & A/C, CS-130; w/ auxiliary heat & A/C, CS-144. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Charging System > Alternator > Component Information > Diagrams > Page 9243 Alternator: Description and Operation Fig. 1 Delcotron Type CS-130 & CS-144 Alternators. These units feature a high ampere output-to-weight ratio. The Delcotron CS-130 & CS-144 alternators are electrically similar to standard units, however, they do not contain a diode trio. The voltage setting of the integral regulator varies with temperature and limits system voltage by controlling rotor field current. The regulator has four terminals; "P," "L," "I," and "S." The "P" terminal is not used. The "L" terminal may be connected to the instrument cluster for charging indicator and voltmeter. The "I" terminal provides a voltage feed for the heated oxygen sensor, variable throttle control relay, and electronic automatic transmission. The "S" terminal is not used. The alternator is serviceable only by complete replacement only. No periodic maintenance is required. It should not be disassembled for any reason. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder Technical Service Bulletin # 73-01-09 Date: 971001 Starting - Revised Procedures for Inop Ignition Cylinder File In Section: 0 - General Information Bulletin No.: 73-01-09 Date: October, 1997 INFORMATION Subject: New Tumblers for Cylinder Recoding, Revised Repair Procedures for Inoperative Ignition Cylinders (Seized/Won't Rotate), Labor Operation/Time Allowances Models: 1995-97 Buick Skylark, Riviera 1995-97 Chevrolet Cavalier 1997 Chevrolet Corvette, Malibu, Venture 1995-97 Oldsmobile Achieva 1997 Oldsmobile Aurora, Cutlass, Silhouette 1995-97 Pontiac Grand Am, Sunfire 1997 Pontiac Grand Prix, Trans Sport 1995-97 Chevrolet and GMC C/K, S/T Models 1996-97 Chevrolet and GMC G, M/L Vans 1996-97 Oldsmobile Bravada The information in this bulletin concerns new designed tumblers for recoding lock cylinders that use double sided reversible keys, revised procedures for servicing ignition lock cylinders that are seized or not able to rotate and revised labor time guide information and allowances. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 9254 The existing labor operation (E7200) has been changed to include "Add" conditions for cylinders that will not rotate. New Tumblers New tumblers are available from GMSPO for recoding lock cylinders that use double-sided reversible keys. These new tumblers should be used immediately and information about the disposition of original tumblers will be provided by GMSPO. Figure 1 shows the new tumbler profile. The shaded area was part of the original tumbler profile, and is removed on the new tumblers. The new part numbers for the tumblers are as follows: Part No. 2852732 = Tumbler # 1 Part No. 2852733 = Tumbler # 2 Part No. 2852734 = Tumbler # 3 Part No. 2852735 = Tumbler # 4 Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. New Procedures For Seized/Won't Rotate Column Mounted Ign. CYL. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 9255 A. On G, J and N Models: DO NOT REMOVE THE STEERING COLUMN as indicated in the Service Manual procedure. 1. Remove the tilt lever, upper and lower column covers. 2. Drill hole in module housing as indicated in the illustration using a short drill bit (1/8" followed by 9/32") and 90 degree drill motor or go degree drill attachment to break or access the retaining spring for the lock cylinder button, see Figure 2. 3. Using a pick or needle nose pliers, remove the retaining spring from the hole. 4. Using pliers, grasp and remove the retaining button for the cylinder. 5. Remove the cylinder from the housing. 6. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 7. Install the new cylinder and reinstall the steering column components. B. On U, W, and light duty trucks, follow the Service Manual procedure for keys missing, or cylinders won't rotate. Procedure: Instrument Panel Mounted Switches Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Customer Interest for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 9256 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder Technical Service Bulletin # 73-01-09 Date: 971001 Starting - Revised Procedures for Inop Ignition Cylinder File In Section: 0 - General Information Bulletin No.: 73-01-09 Date: October, 1997 INFORMATION Subject: New Tumblers for Cylinder Recoding, Revised Repair Procedures for Inoperative Ignition Cylinders (Seized/Won't Rotate), Labor Operation/Time Allowances Models: 1995-97 Buick Skylark, Riviera 1995-97 Chevrolet Cavalier 1997 Chevrolet Corvette, Malibu, Venture 1995-97 Oldsmobile Achieva 1997 Oldsmobile Aurora, Cutlass, Silhouette 1995-97 Pontiac Grand Am, Sunfire 1997 Pontiac Grand Prix, Trans Sport 1995-97 Chevrolet and GMC C/K, S/T Models 1996-97 Chevrolet and GMC G, M/L Vans 1996-97 Oldsmobile Bravada The information in this bulletin concerns new designed tumblers for recoding lock cylinders that use double sided reversible keys, revised procedures for servicing ignition lock cylinders that are seized or not able to rotate and revised labor time guide information and allowances. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 9262 The existing labor operation (E7200) has been changed to include "Add" conditions for cylinders that will not rotate. New Tumblers New tumblers are available from GMSPO for recoding lock cylinders that use double-sided reversible keys. These new tumblers should be used immediately and information about the disposition of original tumblers will be provided by GMSPO. Figure 1 shows the new tumbler profile. The shaded area was part of the original tumbler profile, and is removed on the new tumblers. The new part numbers for the tumblers are as follows: Part No. 2852732 = Tumbler # 1 Part No. 2852733 = Tumbler # 2 Part No. 2852734 = Tumbler # 3 Part No. 2852735 = Tumbler # 4 Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. New Procedures For Seized/Won't Rotate Column Mounted Ign. CYL. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 9263 A. On G, J and N Models: DO NOT REMOVE THE STEERING COLUMN as indicated in the Service Manual procedure. 1. Remove the tilt lever, upper and lower column covers. 2. Drill hole in module housing as indicated in the illustration using a short drill bit (1/8" followed by 9/32") and 90 degree drill motor or go degree drill attachment to break or access the retaining spring for the lock cylinder button, see Figure 2. 3. Using a pick or needle nose pliers, remove the retaining spring from the hole. 4. Using pliers, grasp and remove the retaining button for the cylinder. 5. Remove the cylinder from the housing. 6. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 7. Install the new cylinder and reinstall the steering column components. B. On U, W, and light duty trucks, follow the Service Manual procedure for keys missing, or cylinders won't rotate. Procedure: Instrument Panel Mounted Switches Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Ignition Switch Lock Cylinder: > 73-01-09 > Oct > 97 > Starting - Revised Procedures for Inop Ignition Cylinder > Page 9264 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Ignition Switch > Ignition Switch Lock Cylinder > Component Information > Technical Service Bulletins > Page 9265 Ignition Switch Lock Cylinder: Service and Repair The procedure has been updated by TSB# 73-01-09 Important: This new procedure involves drilling a hole through the plastic ignition switch and into the lock cylinder slightly to break or access a cylinder release button retaining spring (similar to G, J and N models). The removal of the broken spring and then the release button will allow the switch to be reused. 1. Remove the necessary trim panels to gain access to the instrument panel mounted switch (refer to information in "Body and Accessories Section, Instrument Panel, Gauges and Consoles"). a. On instrument panel mounted N models (Malibu and Cutlass), the switch and cylinder can be accessed after removing the instrument cluster assembly and positioning the switch/cylinder upward in the cavity for the cluster assembly. b. On Corvette models, the switch and cylinder can be accessed after removing the knee bolster from the lower instrument panel area and positioning the switch/cylinder downward from its location on the instrument panel. 2. Loosen switch from instrument panel and disconnect the electrical connections, BUT NOT the cable connection for BTSI (Brake/Transmission Shift Interlock). 3. Protect the immediate work area with a fender cover or other suitable material. 4. Locate the surface for the cylinder release button on the plastic ignition switch housing and center punch a location on the "rib" approximately 3/8" rearward (toward the key entry end) from the cylinder release button, see Figure 3. 5. Using a 1/8" drill bit, carefully drill a pilot hole through the plastic housing only. 6. Using a 9/32" drill bit, carefully drill a larger hole at the pilot location, and slightly into the lock cylinder surface to break the release button retaining spring. 7. Remove portions of the broken spring from the hole using a small pair of needle nose pliers (or other suitable tool) and turn switch over to shake out the release button. 8. Grasp the lock cylinder, remove it from the switch housing. 9. Remove any plastic "flash" from the drilling operations and, using compressed air, blow out the ignition switch assembly. 10. Follow the procedures in the General Information Section of the appropriate vehicle Service Manual when recoding of cylinders is required. 11. Install the new cylinder(s) as required by rotating both the cylinder and ignition switch to the "ON" position and pushing the cylinder into the switch. It may be necessary to depress the release button slightly as it passes by the 9/32" hole previously drilled in the housing. 12. Reassemble the ignition switch and instrument panel components as indicated by the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Key > Component Information > Technical Service Bulletins > Locks - Key Code Security Rules and Information Key: Technical Service Bulletins Locks - Key Code Security Rules and Information INFORMATION Bulletin No.: 10-00-89-010 Date: May 27, 2010 Subject: Key Code Security Rules and Information on GM KeyCode Look-Up Application (Canada Only) Models: 2011 and Prior GM Passenger Cars and Trucks 2010 and Prior HUMMER H2, H3 2009 and Prior Saturn and Saab 2002 and Prior Isuzu Attention: This bulletin has been created to address potential issues and questions regarding KeyCode security. This bulletin should be read by all parties involved in KeyCode activity, including dealer operator, partner security coordinator, sales, service and parts departments. A copy of this bulletin should be printed and maintained in the parts department for use as a reference. Important U.S. dealers should refer to Corporate Bulletin Number 10-00-89-009. Where Are Key Codes Located? General Motors provides access to KeyCodes through three sources when a vehicle is delivered to a dealer. Vehicle KeyCodes are located on the original vehicle invoice to the dealership. There is a small white bar coded tag sent with most new vehicles that also has the key code printed on it. Dealerships should make a practice of comparing the tag's keycode numbers to the keycode listed on the invoice. Any discrepancy should be reported immediately to the GM of Canada Key Code Inquiry Desk. Remember to remove the key tag prior to showing vehicles to potential customers. The third source for Key codes is through the GM KeyCode Look-Up feature within the OEConnection D2DLink application. KeyCode Look-Up currently goes back 17 previous model years from the current model year. When a vehicle is received by the dealership, care should be taken to safeguard the original vehicle invoice and KeyCode tag provided with the vehicle. Potential customers should not have access to the invoice or this KeyCode tag prior to the sale being completed. After a sale has been completed, the KeyCode information belongs to the customer and General Motors. Tip Only the original invoice contains key code information, a re-printed invoice does not. GM KeyCode Look-Up Application for GM of Canada Dealers All dealers should review the General Motors of Canada KeyCode Look-Up Policies and Procedures (Service Policy & Procedures Manual Section 3.1.6 "Replacement of VIN plates & keys"). Please note that the KeyCode Access site is restricted. Only authorized users should be using this application. Please see your Parts Manager for site authorized users. KeyCode Look-Up currently goes back 17 years from current model year. Important notes about security: - Users may not access the system from multiple computers simultaneously. - Users may only request one KeyCode at a time. - KeyCode information will only be available on the screen for 2 minutes. - Each user is personally responsible for maintaining and protecting their password. - Never share your password with others. - User Id's are suspended after 6 consecutive failed attempts. - User Id's are disabled if not used for 90 days. - Processes must be in place for regular dealership reviews. - The Parts Manager (or assigned management) must have processes in place for employee termination or life change events. Upon termination individuals access must be turned off immediately and access should be re-evaluated upon any position changes within the dealership. - If you think your password or ID security has been breached, contact Dealer Systems Support at 1-800-265-0573. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Key > Component Information > Technical Service Bulletins > Locks - Key Code Security Rules and Information > Page 9270 Each user will be required to accept the following agreement each time the KeyCode application is used. Key Code User Agreement - Key codes are proprietary information belonging to General Motors Corporation and to the vehicle owner. - Unauthorized access to, or use of, key code information is unlawful and may subject the user to criminal and civil penalties. - This information should be treated as strictly confidential and should not be disclosed to anyone unless authorized. I will ensure that the following information is obtained prior to releasing any Key Code information: 1. Government issued picture ID (Drivers License) 2. Registration or other proof of ownership. Registration should have normal markings from the Province that issued the registration and possibly the receipt for payment recorded as well. Important - GM takes this agreement seriously. Each user must be certain of vehicle ownership before giving out key codes. - When the ownership of the vehicle is in doubt, dealership personnel should not provide the information. Key code requests should never be received via a fax or the internet and key codes should never be provided to anyone in this manner. A face to face contact with the owner of the vehicle is the expected manner that dealers will use to release a key code or as otherwise stipulated in this bulletin or other materials. - Key codes should NEVER be sent via a fax or the internet. - Each Dealership should create a permanent file to document all KeyCode Look Up transactions. Requests should be filed by VIN and in each folder retain copies of the following: - Government issued picture ID (Drivers License) - Registration or other proof of ownership. - Copy of the paid customer receipt which has the name of the employee who cut and sold the key to the customer. - Do not put yourself or your Dealership in the position of needing to "explain" a KeyCode Look Up to either GM or law enforcement officials. - Dealership Management has the ability to review all KeyCode Look-Up transactions. - Dealership KeyCode documentation must be retained for two years. Frequently Asked Questions (FAQs) for GM of Canada Dealers How do I request a KeyCode for customer owned vehicle that is not registered? Scrapped, salvaged or stored vehicles that do not have a current registration should still have the ownership verified by requesting the vehicle title, current insurance policy and / or current lien holder information from the customers financing source. If you cannot determine if the customer is the owner of the vehicle, do not provide the key code information. In these cases, a short description of the vehicle (scrapped, salvaged, etc.) and the dealership location should be kept on file. Any clarifying explanation should be entered into the comments field. How do I document a KeyCode request for a vehicle that is being repossessed? The repossessor must document ownership of the vehicle by providing a court ordered repossession order and lien-holder documents prior to providing key code information. Copies of the repossessors Drivers License and a business card should be retained by the dealership for documentation. What do I do if the registration information is locked in the vehicle? Every effort should be made to obtain complete information for each request. Each Dealership will have to decide on a case by case basis if enough information is available to verify the customer's ownership of the vehicle. Other forms of documentation include vehicle title, insurance policy, and or current lien information from the customers financing source. Dealership Management must be involved in any request without complete information. If you cannot determine if the customer is the owner of the vehicle, do not provide the key code information. Can I get a print out of the information on the screen? It is important to note that the Key Code Look Up Search Results contain sensitive and/or proprietary information. For this reason GM recommends against printing it. If the Search Results must be printed, store and/or dispose of the printed copy properly to minimize the risk of improper or illegal use. Who in the dealership has access to the KeyCode application? Dealership Parts Manager (or assigned management) will determine, and control, who is authorized to access the KeyCode Look Up application. However, we anticipate that dealership parts and service management will be the primary users of the application. The KeyCode Look Up application automatically tracks each user activity session. Information tracked by the system includes: User name, User ID, all other entered data and the date/time of access. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Key > Component Information > Technical Service Bulletins > Locks - Key Code Security Rules and Information > Page 9271 What if I input the VIN incorrectly? If an incorrect VIN is entered into the system (meaning that the system does not recognize the VIN or that the VIN has been entered incorrectly) the system will return an error message. If I am an authorized user for the KeyCode application, can I access the application from home? Yes. What if I suspect key code misuse? Your dealership should communicate the proper procedures for requesting key codes. Any suspicious activity either within the dealership or externally should be reported to Dealer Systems Support at 1-800-265-0573 or GM of Canada Key Code Inquiry Desk at 1-905-644-4892. Whose key codes can I access through the system? At this time the following Canadian vehicle codes are available through the system: Chevrolet, Cadillac, Buick, Pontiac, GMC, HUMMER (H2 and H3 only), Oldsmobile, Saturn, Saab and Isuzu (up to 2002 model year) for a maximum of 17 model years. What should I do if I enter a valid VIN and the system does not produce any key code information? Occasionally, the KeyCode Look Up application may not produce a key code for a valid VIN. This may be the result of new vehicle information not yet available. In addition, older vehicle information may have been sent to an archive status. If you do not receive a key code returned for valid VIN, you should contact GM of Canada Key Code Inquiry Desk at 1-905-644-4892. How do I access KeyCodes if the KeyCode Look-up system is down? If the KeyCode Look-up system is temporarily unavailable, you can contact the original selling dealer who may have it on file or contact GM of Canada Key Code Inquiry Desk at 1-905-644-4892. If the customer is dealing with an emergency lock-out situation, you need to have the customer contact Roadside assistance, OnStar if subscribed, or 911. What should I do if the KeyCode from the look-up system does not work on the vehicle? On occasion a dealer may encounter a KeyCode that will not work on the vehicle in question. In cases where the KeyCode won't work you will need to verify with the manufacturer of the cutting equipment that the key has been cut correctly. If the key has been cut correctly you may be able to verify the proper KeyCode was given through the original selling dealer. When unable to verify the KeyCode through the original selling dealer contact GM of Canada Key Code Inquiry Desk at 1-905-644-4892. If the key has been cut correctly and the code given does not work, the lock cylinder may have been changed. In these situations following the proper SI document for recoding a key or replacing the lock cylinder may be necessary. How long do I have to keep KeyCode Records? Dealership KeyCode documentation must be retained for two years. Can I get a KeyCode changed in the Look-Up system? Yes, KeyCodes can be changed in the Look-Up system if a lock cylinder has been changed. Contact GM of Canada Key Code Inquiry Desk at 1-905-644-4892. What information do I need before I can provide a driver of a company fleet vehicle Keys or KeyCode information? The dealership should have a copy of the individual's driver's license, proof of employment and registration. If there is any question as to the customer's employment by the fleet company, the dealer should attempt to contact the fleet company for verification. If there is not enough information to determine ownership and employment, this information should not be provided. How do I document a request from an Independent Repair facility for a KeyCode or Key? The independent must provide a copy of their driver's license, proof of employment and signed copy of the repair order for that repair facility. The repair order must include customer's name, address, VIN, city, province and license plate number. Copies of this information must be included in your dealer KeyCode file. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Key > Component Information > Technical Service Bulletins > Locks - Key Code Security Rules and Information > Page 9272 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Technical Service Bulletins > Customer Interest: > 01-07-30-021 > May > 01 > Park/Neutral Switch - Connector Hard to Remove Neutral Safety Switch: Customer Interest Park/Neutral Switch - Connector Hard to Remove File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-021 Date: May, 2001 TECHNICAL Subject: Park/Neutral Position Switch Connector Cannot Be Removed (Replace Switch and Connectors) Models: 1997-2001 Chevrolet Camaro, Corvette 1997-2001 Pontiac Firebird 1995-2001 Chevrolet and GMC S/T Models 1996-2001 Chevrolet and GMC C/K, M/L, G and P Models 1996-2001 Oldsmobile Bravada with 4L60E (M30), 4L65E (M32), 4LBOE (MT1) or Allison LCT (M74) Automatic Transmission This bulletin is being revised to change a labor operation number, add models, model years and transmission designations. Please discard Corporate Bulletin Number 83-71-10A (Section 7 Transmission). Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer concerns, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to ensure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to ensure water-tight connections. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Technical Service Bulletins > Customer Interest: > 01-07-30-021 > May > 01 > Park/Neutral Switch - Connector Hard to Remove > Page 9281 For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Neutral Safety Switch: > 01-07-30-021 > May > 01 > Park/Neutral Switch - Connector Hard to Remove Neutral Safety Switch: All Technical Service Bulletins Park/Neutral Switch - Connector Hard to Remove File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-021 Date: May, 2001 TECHNICAL Subject: Park/Neutral Position Switch Connector Cannot Be Removed (Replace Switch and Connectors) Models: 1997-2001 Chevrolet Camaro, Corvette 1997-2001 Pontiac Firebird 1995-2001 Chevrolet and GMC S/T Models 1996-2001 Chevrolet and GMC C/K, M/L, G and P Models 1996-2001 Oldsmobile Bravada with 4L60E (M30), 4L65E (M32), 4LBOE (MT1) or Allison LCT (M74) Automatic Transmission This bulletin is being revised to change a labor operation number, add models, model years and transmission designations. Please discard Corporate Bulletin Number 83-71-10A (Section 7 Transmission). Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer concerns, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to ensure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to ensure water-tight connections. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Neutral Safety Switch: > 01-07-30-021 > May > 01 > Park/Neutral Switch - Connector Hard to Remove > Page 9287 For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Neutral Safety Switch: > 83-71-10 > May > 98 > A/T Park/Neutral Switch Connector Cannot Be Removed Neutral Safety Switch: All Technical Service Bulletins A/T - Park/Neutral Switch Connector Cannot Be Removed File In Section: 7 - Transmission Bulletin No.: 83-71-10 Date: May, 1998 Subject: Park (Neutral Position Switch Connector Cannot be Removed (Replace Switch and Connectors) Models: 1997-98 Chevrolet Corvette 1995-98 Chevrolet and GMC S/T Models 1996-98 Chevrolet and GMC M/L, P Models 1996-99 Chevrolet and GMC C/K, G Models 1996-98 Oldsmobile Bravada Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer conditions, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to insure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to insure water-tight connections. Parts Information P/N Description 12450016 Switch 15305925 4-Way Connector Assembly 15305887 7-Way Connector Assembly Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Technical Service Bulletins > All Other Service Bulletins for Neutral Safety Switch: > 83-71-10 > May > 98 > A/T Park/Neutral Switch Connector Cannot Be Removed Neutral Safety Switch: All Technical Service Bulletins A/T - Park/Neutral Switch Connector Cannot Be Removed File In Section: 7 - Transmission Bulletin No.: 83-71-10 Date: May, 1998 Subject: Park (Neutral Position Switch Connector Cannot be Removed (Replace Switch and Connectors) Models: 1997-98 Chevrolet Corvette 1995-98 Chevrolet and GMC S/T Models 1996-98 Chevrolet and GMC M/L, P Models 1996-99 Chevrolet and GMC C/K, G Models 1996-98 Oldsmobile Bravada Condition Technicians may experience difficulty in removing the connectors from the Park/Neutral Position Switch, usually when trying to remove the switch during transmission service. In rare cases, customers may also report switch related electrical conditions, such as improper or no shift indication, or no back-up light operation. Cause High ambient heat may cause the sealing compound in the switch to melt and flow into the connectors, sealing the connectors to the switch. This normally causes no customer conditions, but may cause an open circuit in rare cases. Correction In many cases, the switch can be removed and reinstalled without removing the connectors. If the switch is being removed as part of transmission service, and there are no switch related conditions, the switch can simply be reinstalled. Some applications have a mounting bolt behind the connectors. The switch will have to be removed and will probably be damaged in the process. The connector pigtails use wires which are all the same color. Use the old connector as a pattern to insure that the new wires are connected to the harness correctly. Important: This switch is in a wet area. It is very important to solder the wires and use heat-shrink tubing to insure water-tight connections. Parts Information P/N Description 12450016 Switch 15305925 4-Way Connector Assembly 15305887 7-Way Connector Assembly Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Locations > With 4L60-E Transmission Electronic 4-speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Locations > With 4L60-E Transmission > Page 9299 Electronic 4-Speed Automatic Overdrive Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions Neutral Safety Switch: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9302 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9303 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9304 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9305 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9306 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9307 Neutral Safety Switch: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9308 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9309 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9310 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9311 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9312 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9313 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9314 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9315 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9316 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9317 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9318 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9319 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9320 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9321 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9322 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9323 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9324 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9325 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9326 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9327 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9328 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9329 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9330 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9331 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9332 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Neutral Safety Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 9333 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Specifications Starter Motor: Specifications Engine ................................................................................................................................................. .............................................................. 5.7L/V8-350 VIN ....................................................................................................................................................... .............................................................................. R Starter ID No. ....................................................................................................................................... .................................................................. 10455050 Free Speed Test Amps ................................................................................................................................................... ...................................................................... 47-70 Volts ................................................................... ............................................................................................................................................................ 10 RPM................................................................................................................................................. ............................................................... 6500-11,000 Solenoid Hold-In Windings, Amps ...................................................................................................................... .................................................................... 10-20 Pull-In Windings, Amps ........................................ ................................................................................................................................................... 60-85 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Specifications > Page 9337 Starter Motor: Locations Rear of Engine, RH side, lower Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions Starter Motor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9340 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9341 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9342 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9343 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9344 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9345 Starter Motor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9346 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9347 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9348 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9349 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9350 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9351 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9352 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9353 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9354 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9355 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9356 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9357 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9358 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9359 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9360 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9361 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9362 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9363 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9364 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9365 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9366 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9367 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9368 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9369 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9370 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 9371 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Diagrams > Page 9372 Starter Motor: Description and Operation Fig. 3 PG-260 Straight Drive Starter. The Delco-Remy PG-260 starter motor has the solenoid shift lever mechanism and the solenoid plunger enclosed in the drive housing to protect them from exposure to road dirt, icing conditions and splash. They have an extruded field frame and an overrunning clutch type drive. The overrunning clutch is operated by a solenoid switch mounted to a flange on the drive housing. This permanent magnet gear reduction starter achieves gear reduction at a ratio of 5:1 through planetary gears. The solenoid is attached to the drive end housing by two screws. The cover can be removed to inspect the contacts and contact disc, but the switch is serviced as an assembly only. Most motors of this type have graphite and oil impregnated bronze bearings which ordinarily require no added lubrication except at time of overhaul when a few drops of light engine oil should be placed on each bearing before reassembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Testing and Inspection > Free Speed Inspection Starter Motor: Testing and Inspection Free Speed Inspection Fig. 12 Motor Free Speed Inspection. This test is performed during bench testing. With the circuit connected, use a tachometer to measure armature revolutions per minute. Failure of the motor to perform to specifications may be due to light or dry bearings, or high resistance connections. Starter motors do not require lubrication except during overhaul. At this time a couple drops of light oil may be applied to bearings. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Testing and Inspection > Free Speed Inspection > Page 9375 Starter Motor: Testing and Inspection Pinion Clearance Inspection Fig. 13 Pinion Clearance Inspection Connections. Fig. 14 Pinion Clearance Inspection. There is no provision for adjusting pinion clearance on this motor, but clearance should be checked after motor reassembly. When the shift lever is assembled properly, pinion clearance should be 0.010-0.060 inch.When clearance is not within specifications, it may indicate excessive wear of the solenoid linkage or the shift lever yoke buttons. Check pinion clearance as follows: 1. Disconnect motor field coil connector from solenoid motor terminal, then insulate end carefully. 2. Connect one battery lead to solenoid switch terminal, then the other lead to the solenoid frame. 3. Connect a jumper lead to solenoid motor terminal. Momentarily flash lead to solenoid frame. This will shift pinion into cranking position until the battery is disconnected. 4. Push pinion back toward commutator end as far as possible to take up any slack movement, then check clearance with a feeler gauge. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Motor > Component Information > Testing and Inspection > Page 9376 Starter Motor: Service and Repair 1. Disconnect battery ground cable. 2. Remove starter braces or heat shields, if equipped. 3. Disconnect starter solenoid electrical connectors. 4. Raise and support vehicle. 5. Remove attaching bolts, nuts and washers from starter motor. 6. Remove starter motor from engine. 7. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Relay > Component Information > Locations Starter Relay: Locations In Underhood Fuse - Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Locations Starter Solenoid: Locations Battery Wiring (Typical) On Starter Motor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions Starter Solenoid: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9385 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9386 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9387 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9388 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9389 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9390 Starter Solenoid: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9391 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9392 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9393 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9394 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9395 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9396 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9397 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9398 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9399 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9400 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9401 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9402 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9403 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9404 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9405 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9406 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9407 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9408 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9409 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9410 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9411 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9412 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9413 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9414 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9415 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Starting System > Starter Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 9416 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Auxiliary Power Outlet > Component Information > Technical Service Bulletins > Customer Interest for Auxiliary Power Outlet: > 99-08-45-005 > Nov > 99 > Accessory Receptacle/Cigar Lighter - Inoperative Auxiliary Power Outlet: Customer Interest Accessory Receptacle/Cigar Lighter - Inoperative File In Section: 08 - Body and Accessories Bulletin No.: 99-08-45-005 Date: November, 1999 TECHNICAL Subject: Accessory Receptacle/Cigar Lighter is Inoperative (Check Aftermarket Device Plug for Short to Ground) Models: 1995-2000 Passenger Cars and Trucks Condition Some customers may comment that the cigar lighter or the accessory receptacle is inoperative; or that the internal fuse (within the plug on an aftermarket device), blows intermittently. Cause Certain aftermarket devices have a newly designed power plug with an internal mini fuse. The mini fuse may have an external terminal (which may be used to externally check the fuse). If the mini fuse external test terminal is not recessed into the mini fuse body, it may come in contact with the shell of the vehicle receptacle and cause the fuse (of either the vehicle or the aftermarket device), to blow intermittently. Correction Test the aftermarket device plug for short to ground. The following step may be performed at the customer's expense. As this is not a defect in material, design or workmanship of the vehicle, it would be the owner's responsibility. 1. Place a piece of tape over the mini fuse terminal temporarily. 2. Explain to the customer that the fuse for the device must have no exposed terminals, and that finding one would be his responsibility. 3. Refer the customer to the manufacturer of the aftermarket device for a new plug. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Auxiliary Power Outlet > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Auxiliary Power Outlet: > 99-08-45-005 > Nov > 99 > Accessory Receptacle/Cigar Lighter - Inoperative Auxiliary Power Outlet: All Technical Service Bulletins Accessory Receptacle/Cigar Lighter Inoperative File In Section: 08 - Body and Accessories Bulletin No.: 99-08-45-005 Date: November, 1999 TECHNICAL Subject: Accessory Receptacle/Cigar Lighter is Inoperative (Check Aftermarket Device Plug for Short to Ground) Models: 1995-2000 Passenger Cars and Trucks Condition Some customers may comment that the cigar lighter or the accessory receptacle is inoperative; or that the internal fuse (within the plug on an aftermarket device), blows intermittently. Cause Certain aftermarket devices have a newly designed power plug with an internal mini fuse. The mini fuse may have an external terminal (which may be used to externally check the fuse). If the mini fuse external test terminal is not recessed into the mini fuse body, it may come in contact with the shell of the vehicle receptacle and cause the fuse (of either the vehicle or the aftermarket device), to blow intermittently. Correction Test the aftermarket device plug for short to ground. The following step may be performed at the customer's expense. As this is not a defect in material, design or workmanship of the vehicle, it would be the owner's responsibility. 1. Place a piece of tape over the mini fuse terminal temporarily. 2. Explain to the customer that the fuse for the device must have no exposed terminals, and that finding one would be his responsibility. 3. Refer the customer to the manufacturer of the aftermarket device for a new plug. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Auxiliary Power Outlet > Component Information > Locations > Auxiliary Power Connectors Auxiliary Power Outlet: Locations Auxiliary Power Connectors Center of I/P area, in Ash Tray Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Auxiliary Power Outlet > Component Information > Locations > Auxiliary Power Connectors > Page 9433 Auxiliary Power Outlet: Locations Spare Power Source Under LH side of I/P, on Bulkhead Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Fuse > Component Information > Technical Service Bulletins > Electrical - Aftermarket Fuse Warning Fuse: Technical Service Bulletins Electrical - Aftermarket Fuse Warning Bulletin No.: 07-08-45-002 Date: September 05, 2007 ADVANCED SERVICE INFORMATION Subject: Service Alert: Concerns With Aftermarket Fuses in GM Vehicles Models: 2008 and Prior GM Passenger Cars and Light Duty Trucks (including Saturn) 2008 and Prior HUMMER H2, H3 2008 and Prior Saab 9-7X Concerns with Harbor Freight Tools "Storehouse" Branded Blade Type Fuses General Motors has become aware of a fuse recall by Harbor Freight Tools/Storehouse for a variety of aftermarket fuses. In two cases, these fuses have not provided protection for the wiring system of the vehicles they were customer installed in. Upon testing the 15 amp version, it was found that the fuse still would not "open" when shorted directly across the battery terminals. How to Identify These Fuses Packed in a 120 piece set, the fuse has a translucent, hard plastic, blue body with the amperage stamped into the top. There are no white painted numbers on the fuse to indicate amperage. There are no identifying marks on the fuse to tell who is making it. The fuses are known to be distributed by Harbor Freight Tools but there may be other marketers, and packaging of this style of fuse. It would be prudent to replace these fuses if found in a customers vehicle. Likewise, if wiring overheating is found you should check the fuse panel for the presence of this style of fuse. All GM dealers should use genuine GM fuses on the vehicles they service. You should also encourage the use of GM fuses to your customers to assure they are getting the required electrical system protection. GM has no knowledge of any concerns with other aftermarket fuses. If additional information becomes available, this bulletin will be updated. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Fuse > Component Information > Technical Service Bulletins > Page 9438 Instrument Panel Wiring, LH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Fuse > Component Information > Application and ID > I/P Fuse Block Fuse: Application and ID I/P Fuse Block I/P Fuse Block (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Fuse > Component Information > Application and ID > I/P Fuse Block > Page 9441 I/P Fuse Block (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Fuse > Component Information > Application and ID > I/P Fuse Block > Page 9442 Fuse: Application and ID Convenience Center Convenience Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Fuse > Component Information > Application and ID > I/P Fuse Block > Page 9443 Convenience Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Fuse > Component Information > Application and ID > I/P Fuse Block > Page 9444 Fuse: Application and ID Underhood Fuse/Relay Center Underhood Fuse-Relay Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Fuse > Component Information > Application and ID > I/P Fuse Block > Page 9445 Underhood Fuse-Relay Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Fuse Block > Component Information > Locations > Convenience Center Fuse Block: Locations Convenience Center Convenience Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Fuse Block > Component Information > Locations > Convenience Center > Page 9450 Instrument Panel Wiring, LH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Fuse Block > Component Information > Locations > Convenience Center > Page 9451 Underhood Fuse-Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Fuse Block > Component Information > Locations > Page 9452 C210: Cross Body HARN To Convenience Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Fuse Block > Component Information > Application and ID > I/P Fuse Block Fuse Block: Application and ID I/P Fuse Block I/P Fuse Block (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Fuse Block > Component Information > Application and ID > I/P Fuse Block > Page 9455 I/P Fuse Block (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Fuse Block > Component Information > Application and ID > I/P Fuse Block > Page 9456 Fuse Block: Application and ID Underhood Fuse/Relay Center Underhood Fuse-Relay Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Fuse Block > Component Information > Application and ID > I/P Fuse Block > Page 9457 Underhood Fuse-Relay Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Fuse Block > Component Information > Application and ID > I/P Fuse Block > Page 9458 Fuse Block: Application and ID Convenience Center Convenience Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Fuse Block > Component Information > Application and ID > I/P Fuse Block > Page 9459 Convenience Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > Customer Interest: > 66-71-04 > May > 96 > A/T - 1-2 or 2-3 Slip/Flare, Launch Shudder & DTC P1870 Grounding Point: Customer Interest A/T - 1-2 or 2-3 Slip/Flare, Launch Shudder & DTC P1870 66-71-04 CHEVROLET Issued: 05/10/96 SUBJECT: AUTOMATIC TRANSMISSION 1-2 AND/OR 2-3 UPSHIFT SLIP/FLARE, NO 3RD OR 4TH GEAR, LAUNCH SHUDDER, DTC P1870 (REVISE VCM WIRING) MODELS: 1996 CHEVROLET AND GMC C/K, S/T, M/L, G1, G2 AND P3 MODELS 1996 OLDSMOBILE BRAVADA WITH VCM AND 4L60-E (M30) OR 4L80-E (M11) AUTOMATIC TRANSMISSION CONDITION: SOME OWNERS MAY COMMENT THAT THE AUTOMATIC TRANSMISSION HAS EITHER A SLIP OR FLARE ON THE 1-2 AND/OR 2-3 UPSHIFT, OR NO 3RD OR 4TH GEAR, OR LAUNCH SHUDDER. DTC P1870 MAY ALSO BE STORED IN THE VCM. CAUSE: A POOR INTERNAL GROUND BETWEEN THE TWO CIRCUIT BOARDS OF THE VCM CAN CAUSE THE VCM TO COMMAND ERRATIC LINE PRESSURE AT THE PRESSURE CONTROL SOLENOIDS (PCS). CORRECTION: USING HARNESS JUMPER WIRE AND INSTRUCTION KIT, P/N 12167310, REVISE THE WIRING HARNESS AT THE VCM CONNECTOR. CORRECTIONS WERE MADE TO THE VCM BEGINNING 2/14/96. THE CORRECTED VCM'S ARE IDENTIFIED WITH SERVICE NUMBER 16244210 ON THE VCM IDENTIFICATION LABEL. SERVICE PROCEDURE THE FOLLOWING IS A SUMMARY OF THE INSTRUCTIONS INCLUDED WITH THE SERVICE KIT: 1. REMOVE THE NEGATIVE TERMINAL FROM THE BATTERY. 2. MOVE THE WIRE LOCATED AT CONNECTOR J3 (WHITE/GRAY/CLEAR), PIN 18 TO CONNECTOR J1 (BLUE), PIN 23. 3. INSTALL THE JUMPER WIRE BETWEEN CONNECTOR J2 (RED), PIN 26 AND CONNECTOR J3 (WHITE/GREY/CLEAR), PIN 18. 4. INSTALL THE TAG INCLUDED IN THE KIT AROUND THE VCM WIRING HARNESS. THIS TAG NOTES THAT THE WIRING HARNESS HAS BEEN MODIFIED. 5. RECONNECT THE NEGATIVE BATTERY TERMINAL. ROAD TEST TO VERIFY THAT THE CONDITION HAS BEEN CORRECTED. IF ANY OF THE FOLLOWING CONDITIONS ARE NOTED, THE TRANSMISSION SHOULD BE REPLACED, OR FOR CANADIAN DEALERS, REPAIRED. - TRANSMISSION FLUID OXIDATION OR EXCESSIVE SEDIMENT. - TRANSMISSION SLIP OR FLARE AFTER THIS SERVICE FIX IS PERFORMED. - DTC P1870 IS STORED ON A 4L60-E (M30). THE FOLLOWING TOOLS ARE AVAILABLE FROM KENT-MOORE (1-800-345-2233) FOR USE IN REMOVING AND RELATING THE VCM CONNECTOR. - J41759 PUNCH: USED TO PUNCH A NEW HOLE THROUGH THE CONNECTOR SEAL. PARTS INFORMATION P/N DESCRIPTION QTY 12167310 HARNESS JUMPER WIRE KIT 1 PARTS ARE EXPECTED TO BE AVAILABLE ON 5/13/96 FROM GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > Customer Interest: > 66-71-04 > May > 96 > A/T - 1-2 or 2-3 Slip/Flare, Launch Shudder & DTC P1870 > Page 9468 WARRANTY INFORMATION FOR VEHICLES REPAIRED UNDER WARRANTY, USE: LABOR OP DESCRIPTION LABOR TIME N6112 WIRE REPAIR USE PUBLISHED FRONT CHASSIS LABOR OPERATION TIME Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Grounding Point: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair Grounding Point: All Technical Service Bulletins Electrical - Information For Electrical Ground Repair INFORMATION Bulletin No.: 10-08-45-001B Date: October 25, 2010 Subject: Information for Electrical Ground Repair - Use New Replacement Fasteners with Conductive Finish Models: 2011 and Prior GM Passenger Cars and Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add the 2011 model year and update the Warranty Information. Please discard Corporate Bulletin Number 10-08-45-001A (Section 08 - Body and Accessories). Electrical Ground Repair Overview Proper electrical system function relies on secure, stable and corrosion-free electrical ground connections. Loose, stripped, or corroded connections increase the possibility of improper system function and loss of module communication. These conditions may also lead to unnecessary repairs and component replacement. In general, electrical ground connections are accomplished using one, or a combination of the following attachment methods: - Welded M6 stud and nut - Welded M6 nut and bolt - Welded M8 nut and bolt Determine which attachment method is used and perform the appropriate or alternative repair as described in this bulletin. M6 Weld Stud Replacement Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. Select a location adjacent the damaged or missing M6 ground stud having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the M6 conductive rivet stud flange. 2. Using GM approved residue-free solvent or equivalent, remove any grease from the repair site and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 3. Drill a 10 mm (0.40 in) diameter hole through the panel. 4. Remove paint and primer from the area surrounding the 10 mm (0.40 in) hole until bare metal is visible. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Grounding Point: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9474 Important The M6 conductive rivet stud as shown, can accommodate a panel thickness range of 0.7-4.2 mm (0.03-0.17 in). If there are layers of sheet metal, they should be touching without any air gaps to ensure a good ground. 5. Select a M6 conductive rivet stud. Refer to the Parts Information section of this bulletin. Note Use the GE-50317 rivet stud tool kit. 6. Place the M6 conductive rivet stud (1) in the 10 mm (0.40 in) hole. Assemble the rivet stud tool (2) with the groove and flare side facing the rivet stud, then the washer and the M6 nut (3). 7. Using a wrench on the rivet stud tool, and a socket on the M6 nut, secure the M6 conductive rivet stud. 8. Ensure the rivet stud is securely fastened, WITHOUT ANY detectable movement. 9. Completely wrap the threads of the rivet stud with painters tape or equivalent. Note The rivet stud and surrounding panel area MUST BE properly refinished PRIOR to the installation of the ground wire terminal and conductive nut to maintain a secure, stable and corrosion-free electrical ground. 10. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 11. Allow the refinished repair area to cure sufficiently before removing the protective material applied to the rivet stud threads. 12. Remove the painters tape or equivalent from the rivet stud threads. 13. Using GM approved residue-free solvent or equivalent, thoroughly clean the rivet stud threads to remove any adhesive and allow to dry. 14. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive rivet stud. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Grounding Point: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9475 15. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 16. Install the electrical ground wire terminal to the rivet stud. 17. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 18. Install the M6 conductive nut to the rivet stud and: Tighten Tighten to 8 Nm (71 lb in). 19. Verify proper system operation. M6 Weld Nut Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M6 weld nut at the electrical ground location is damaged or stripped, a M7 conductive self-threading bolt may be used to secure the ground wire terminal. 2. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the weld nut and allow to dry. 3. Remove any loose metal particles from the damaged or stripped weld nut with a stiff brush. 4. Select a M7 conductive self-threading bolt. Refer to the Parts Information section of this bulletin 5. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M7 conductive self-threading bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 6. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 7. Install the electrical ground wire terminal to the M7 conductive self-threading bolt. 8. Install the M7 conductive self-threading bolt and: Tighten Tighten to 9 Nm (80 lb in). 9. Verify proper system operation. M6 Weld Nut Alternative Repair Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the electrical ground location is accessible from both sides of the panel, a M6 conductive bolt and a M6 conductive nut may be used to secure the electrical ground wire terminal. Refer to the Parts Information section of this bulletin. 2. Select a location adjacent the damaged M6 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the new electrical ground site. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the ground location and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 8.5 mm (0.33 in) diameter hole through the panel. 5. Remove paint and primer from the area surrounding the 8.5 mm (0.33 in) hole until bare metal is visible. 6. Select a M6 conductive bolt. Refer to the Parts Information section of this bulletin. 7. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 8. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 9. Install the electrical ground wire terminal and the M6 conductive bolt to the ground location. 10. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 11. Install the M6 conductive nut to the bolt and: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Grounding Point: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9476 Tighten Tighten to 8 Nm (71 lb in). Note The repair area MUST BE properly refinished to maintain a secure, stable and corrosion-free electrical ground. 12. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 13. Verify proper system operation. M8 Weld Nut Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M8 weld nut electrical ground location is accessible from both sides of the panel, a M8 conductive bolt and a M8 conductive nut may be used to secure the electrical ground wire terminal. Refer to the Parts Information section of this bulletin. 2. Select a location adjacent the M8 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the new electrical ground site. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the ground location and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 10 mm (0.40 in) diameter hole through the panel. 5. Remove paint and primer from the area surrounding the 10 mm (0.40 in) hole until bare metal is visible. 6. Select a M8 conductive bolt. Refer to the Parts Information section of this bulletin. 7. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M8 conductive bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 8. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 9. Install the electrical ground wire terminal and the M8 conductive bolt to the ground location. 10. Select a M8 conductive nut. Refer to the Parts Information section of this bulletin. 11. Install the M8 conductive nut to the bolt and: Tighten Tighten to 22 Nm (16 lb ft). Note The repair area MUST BE properly refinished to maintain a secure, stable and corrosion-free electrical ground. 12. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 13. Verify proper system operation. M8 Weld Nut Alternative Repair Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M8 weld nut electrical ground location is not accessible from both sides of the panel, a M6 conductive rivet stud and a M6 conductive nut may be used to secure the electrical ground wire terminal. 2. Select a location adjacent the damaged M8 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the M6 conductive rivet stud flange. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the repair site and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 10 mm (0.40 in) diameter hole through the panel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Grounding Point: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9477 5. Remove paint and primer from the area surrounding the 10 mm (0.40 in) until bare metal is visible. Important The M6 conductive rivet stud as shown, can accommodate a panel thickness range of 0.7-4.2 mm (0.03-0.17 in). If there are layers of sheet metal, they should be touching without any air gaps to ensure a good ground. 6. Select a M6 conductive rivet stud. Refer to the Parts Information section of this bulletin. Note Use the GE-50317 rivet stud tool kit. 7. Place the M6 conductive rivet stud (1) in the 10 mm (0.40 in) hole. Assemble the rivet stud tool (2) with the groove and flare side facing the rivet stud, then the washer and the M6 nut (3). 8. Using a wrench on the rivet stud tool, and a socket on the M6 nut, secure the M6 conductive rivet stud. 9. Ensure the new rivet stud is securely fastened, WITHOUT ANY detectable movement. 10. Completely wrap the threads of the rivet stud with painters tape or equivalent. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Grounding Point: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9478 Note The rivet stud and surrounding panel area MUST BE properly refinished PRIOR to the installation of the electrical ground wire terminal and conductive nut to maintain a secure, stable and corrosion-free electrical ground. 11. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 12. Allow the refinished repair area to cure sufficiently before removing the protective material applied to the rivet stud threads. 13. Remove the painters tape or equivalent from the rivet stud threads. 14. Using GM approved residue-free solvent or equivalent, thoroughly clean the rivet stud threads to remove any adhesive and allow to dry. 15. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive rivet stud. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 16. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 17. Install the electrical ground wire terminal to the M6 conductive rivet stud. 18. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 19. Install the M6 conductive nut to the rivet stud and: Tighten Tighten to 8 Nm (71 lb in) 20. Verify proper system operation. Parts Information Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Grounding Point: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9479 For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Grounding Point: > 66-71-04 > May > 96 > A/T - 1-2 or 2-3 Slip/Flare, Launch Shudder & DTC P1870 Grounding Point: All Technical Service Bulletins A/T - 1-2 or 2-3 Slip/Flare, Launch Shudder & DTC P1870 66-71-04 CHEVROLET Issued: 05/10/96 SUBJECT: AUTOMATIC TRANSMISSION 1-2 AND/OR 2-3 UPSHIFT SLIP/FLARE, NO 3RD OR 4TH GEAR, LAUNCH SHUDDER, DTC P1870 (REVISE VCM WIRING) MODELS: 1996 CHEVROLET AND GMC C/K, S/T, M/L, G1, G2 AND P3 MODELS 1996 OLDSMOBILE BRAVADA WITH VCM AND 4L60-E (M30) OR 4L80-E (M11) AUTOMATIC TRANSMISSION CONDITION: SOME OWNERS MAY COMMENT THAT THE AUTOMATIC TRANSMISSION HAS EITHER A SLIP OR FLARE ON THE 1-2 AND/OR 2-3 UPSHIFT, OR NO 3RD OR 4TH GEAR, OR LAUNCH SHUDDER. DTC P1870 MAY ALSO BE STORED IN THE VCM. CAUSE: A POOR INTERNAL GROUND BETWEEN THE TWO CIRCUIT BOARDS OF THE VCM CAN CAUSE THE VCM TO COMMAND ERRATIC LINE PRESSURE AT THE PRESSURE CONTROL SOLENOIDS (PCS). CORRECTION: USING HARNESS JUMPER WIRE AND INSTRUCTION KIT, P/N 12167310, REVISE THE WIRING HARNESS AT THE VCM CONNECTOR. CORRECTIONS WERE MADE TO THE VCM BEGINNING 2/14/96. THE CORRECTED VCM'S ARE IDENTIFIED WITH SERVICE NUMBER 16244210 ON THE VCM IDENTIFICATION LABEL. SERVICE PROCEDURE THE FOLLOWING IS A SUMMARY OF THE INSTRUCTIONS INCLUDED WITH THE SERVICE KIT: 1. REMOVE THE NEGATIVE TERMINAL FROM THE BATTERY. 2. MOVE THE WIRE LOCATED AT CONNECTOR J3 (WHITE/GRAY/CLEAR), PIN 18 TO CONNECTOR J1 (BLUE), PIN 23. 3. INSTALL THE JUMPER WIRE BETWEEN CONNECTOR J2 (RED), PIN 26 AND CONNECTOR J3 (WHITE/GREY/CLEAR), PIN 18. 4. INSTALL THE TAG INCLUDED IN THE KIT AROUND THE VCM WIRING HARNESS. THIS TAG NOTES THAT THE WIRING HARNESS HAS BEEN MODIFIED. 5. RECONNECT THE NEGATIVE BATTERY TERMINAL. ROAD TEST TO VERIFY THAT THE CONDITION HAS BEEN CORRECTED. IF ANY OF THE FOLLOWING CONDITIONS ARE NOTED, THE TRANSMISSION SHOULD BE REPLACED, OR FOR CANADIAN DEALERS, REPAIRED. - TRANSMISSION FLUID OXIDATION OR EXCESSIVE SEDIMENT. - TRANSMISSION SLIP OR FLARE AFTER THIS SERVICE FIX IS PERFORMED. - DTC P1870 IS STORED ON A 4L60-E (M30). THE FOLLOWING TOOLS ARE AVAILABLE FROM KENT-MOORE (1-800-345-2233) FOR USE IN REMOVING AND RELATING THE VCM CONNECTOR. - J41759 PUNCH: USED TO PUNCH A NEW HOLE THROUGH THE CONNECTOR SEAL. PARTS INFORMATION P/N DESCRIPTION QTY 12167310 HARNESS JUMPER WIRE KIT 1 PARTS ARE EXPECTED TO BE AVAILABLE ON 5/13/96 FROM GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Grounding Point: > 66-71-04 > May > 96 > A/T - 1-2 or 2-3 Slip/Flare, Launch Shudder & DTC P1870 > Page 9484 WARRANTY INFORMATION FOR VEHICLES REPAIRED UNDER WARRANTY, USE: LABOR OP DESCRIPTION LABOR TIME N6112 WIRE REPAIR USE PUBLISHED FRONT CHASSIS LABOR OPERATION TIME Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Other Service Bulletins for Grounding Point: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair Grounding Point: All Technical Service Bulletins Electrical - Information For Electrical Ground Repair INFORMATION Bulletin No.: 10-08-45-001B Date: October 25, 2010 Subject: Information for Electrical Ground Repair - Use New Replacement Fasteners with Conductive Finish Models: 2011 and Prior GM Passenger Cars and Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add the 2011 model year and update the Warranty Information. Please discard Corporate Bulletin Number 10-08-45-001A (Section 08 - Body and Accessories). Electrical Ground Repair Overview Proper electrical system function relies on secure, stable and corrosion-free electrical ground connections. Loose, stripped, or corroded connections increase the possibility of improper system function and loss of module communication. These conditions may also lead to unnecessary repairs and component replacement. In general, electrical ground connections are accomplished using one, or a combination of the following attachment methods: - Welded M6 stud and nut - Welded M6 nut and bolt - Welded M8 nut and bolt Determine which attachment method is used and perform the appropriate or alternative repair as described in this bulletin. M6 Weld Stud Replacement Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. Select a location adjacent the damaged or missing M6 ground stud having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the M6 conductive rivet stud flange. 2. Using GM approved residue-free solvent or equivalent, remove any grease from the repair site and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 3. Drill a 10 mm (0.40 in) diameter hole through the panel. 4. Remove paint and primer from the area surrounding the 10 mm (0.40 in) hole until bare metal is visible. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Other Service Bulletins for Grounding Point: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9490 Important The M6 conductive rivet stud as shown, can accommodate a panel thickness range of 0.7-4.2 mm (0.03-0.17 in). If there are layers of sheet metal, they should be touching without any air gaps to ensure a good ground. 5. Select a M6 conductive rivet stud. Refer to the Parts Information section of this bulletin. Note Use the GE-50317 rivet stud tool kit. 6. Place the M6 conductive rivet stud (1) in the 10 mm (0.40 in) hole. Assemble the rivet stud tool (2) with the groove and flare side facing the rivet stud, then the washer and the M6 nut (3). 7. Using a wrench on the rivet stud tool, and a socket on the M6 nut, secure the M6 conductive rivet stud. 8. Ensure the rivet stud is securely fastened, WITHOUT ANY detectable movement. 9. Completely wrap the threads of the rivet stud with painters tape or equivalent. Note The rivet stud and surrounding panel area MUST BE properly refinished PRIOR to the installation of the ground wire terminal and conductive nut to maintain a secure, stable and corrosion-free electrical ground. 10. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 11. Allow the refinished repair area to cure sufficiently before removing the protective material applied to the rivet stud threads. 12. Remove the painters tape or equivalent from the rivet stud threads. 13. Using GM approved residue-free solvent or equivalent, thoroughly clean the rivet stud threads to remove any adhesive and allow to dry. 14. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive rivet stud. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Other Service Bulletins for Grounding Point: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9491 15. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 16. Install the electrical ground wire terminal to the rivet stud. 17. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 18. Install the M6 conductive nut to the rivet stud and: Tighten Tighten to 8 Nm (71 lb in). 19. Verify proper system operation. M6 Weld Nut Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M6 weld nut at the electrical ground location is damaged or stripped, a M7 conductive self-threading bolt may be used to secure the ground wire terminal. 2. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the weld nut and allow to dry. 3. Remove any loose metal particles from the damaged or stripped weld nut with a stiff brush. 4. Select a M7 conductive self-threading bolt. Refer to the Parts Information section of this bulletin 5. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M7 conductive self-threading bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 6. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 7. Install the electrical ground wire terminal to the M7 conductive self-threading bolt. 8. Install the M7 conductive self-threading bolt and: Tighten Tighten to 9 Nm (80 lb in). 9. Verify proper system operation. M6 Weld Nut Alternative Repair Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the electrical ground location is accessible from both sides of the panel, a M6 conductive bolt and a M6 conductive nut may be used to secure the electrical ground wire terminal. Refer to the Parts Information section of this bulletin. 2. Select a location adjacent the damaged M6 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the new electrical ground site. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the ground location and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 8.5 mm (0.33 in) diameter hole through the panel. 5. Remove paint and primer from the area surrounding the 8.5 mm (0.33 in) hole until bare metal is visible. 6. Select a M6 conductive bolt. Refer to the Parts Information section of this bulletin. 7. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 8. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 9. Install the electrical ground wire terminal and the M6 conductive bolt to the ground location. 10. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 11. Install the M6 conductive nut to the bolt and: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Other Service Bulletins for Grounding Point: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9492 Tighten Tighten to 8 Nm (71 lb in). Note The repair area MUST BE properly refinished to maintain a secure, stable and corrosion-free electrical ground. 12. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 13. Verify proper system operation. M8 Weld Nut Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M8 weld nut electrical ground location is accessible from both sides of the panel, a M8 conductive bolt and a M8 conductive nut may be used to secure the electrical ground wire terminal. Refer to the Parts Information section of this bulletin. 2. Select a location adjacent the M8 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the new electrical ground site. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the ground location and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 10 mm (0.40 in) diameter hole through the panel. 5. Remove paint and primer from the area surrounding the 10 mm (0.40 in) hole until bare metal is visible. 6. Select a M8 conductive bolt. Refer to the Parts Information section of this bulletin. 7. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M8 conductive bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 8. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 9. Install the electrical ground wire terminal and the M8 conductive bolt to the ground location. 10. Select a M8 conductive nut. Refer to the Parts Information section of this bulletin. 11. Install the M8 conductive nut to the bolt and: Tighten Tighten to 22 Nm (16 lb ft). Note The repair area MUST BE properly refinished to maintain a secure, stable and corrosion-free electrical ground. 12. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 13. Verify proper system operation. M8 Weld Nut Alternative Repair Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M8 weld nut electrical ground location is not accessible from both sides of the panel, a M6 conductive rivet stud and a M6 conductive nut may be used to secure the electrical ground wire terminal. 2. Select a location adjacent the damaged M8 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the M6 conductive rivet stud flange. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the repair site and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 10 mm (0.40 in) diameter hole through the panel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Other Service Bulletins for Grounding Point: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9493 5. Remove paint and primer from the area surrounding the 10 mm (0.40 in) until bare metal is visible. Important The M6 conductive rivet stud as shown, can accommodate a panel thickness range of 0.7-4.2 mm (0.03-0.17 in). If there are layers of sheet metal, they should be touching without any air gaps to ensure a good ground. 6. Select a M6 conductive rivet stud. Refer to the Parts Information section of this bulletin. Note Use the GE-50317 rivet stud tool kit. 7. Place the M6 conductive rivet stud (1) in the 10 mm (0.40 in) hole. Assemble the rivet stud tool (2) with the groove and flare side facing the rivet stud, then the washer and the M6 nut (3). 8. Using a wrench on the rivet stud tool, and a socket on the M6 nut, secure the M6 conductive rivet stud. 9. Ensure the new rivet stud is securely fastened, WITHOUT ANY detectable movement. 10. Completely wrap the threads of the rivet stud with painters tape or equivalent. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Other Service Bulletins for Grounding Point: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9494 Note The rivet stud and surrounding panel area MUST BE properly refinished PRIOR to the installation of the electrical ground wire terminal and conductive nut to maintain a secure, stable and corrosion-free electrical ground. 11. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 12. Allow the refinished repair area to cure sufficiently before removing the protective material applied to the rivet stud threads. 13. Remove the painters tape or equivalent from the rivet stud threads. 14. Using GM approved residue-free solvent or equivalent, thoroughly clean the rivet stud threads to remove any adhesive and allow to dry. 15. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive rivet stud. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 16. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 17. Install the electrical ground wire terminal to the M6 conductive rivet stud. 18. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 19. Install the M6 conductive nut to the rivet stud and: Tighten Tighten to 8 Nm (71 lb in) 20. Verify proper system operation. Parts Information Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Other Service Bulletins for Grounding Point: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9495 For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Relays and Modules - Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Electrical - Revised Convenience Center Cavity ID Relay Box: Technical Service Bulletins Electrical - Revised Convenience Center Cavity ID File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-82-08 Date: August, 1997 SERVICE MANUAL UPDATE Subject: Section 8A-11 Fuse Block Details Revised Convenience Center Table Models: 1996-98 Chevrolet and GMC C/K models. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Relays and Modules - Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Electrical - Revised Convenience Center Cavity ID > Page 9501 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Relays and Modules - Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Electrical - Revised Convenience Center Cavity ID > Page 9502 This bulletin revises "Convenience Center" table on Page 8A-11-5, 6 in the 1996 C/K Service Manual, Page 8A-11-6, 7 in the 1997 C/K Service Manual, and Page 8A-11-5 in the 1998 C/K Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Relays and Modules - Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Page 9503 Underhood Fuse-Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Relays and Modules - Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Page 9504 Relay Box: Application and ID Underhood Fuse-Relay Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Relays and Modules - Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Page 9505 Underhood Fuse-Relay Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Electrical - Revised Convenience Center Cavity ID Relay Box: Technical Service Bulletins Electrical - Revised Convenience Center Cavity ID File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-82-08 Date: August, 1997 SERVICE MANUAL UPDATE Subject: Section 8A-11 Fuse Block Details Revised Convenience Center Table Models: 1996-98 Chevrolet and GMC C/K models. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Electrical - Revised Convenience Center Cavity ID > Page 9510 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Electrical - Revised Convenience Center Cavity ID > Page 9511 This bulletin revises "Convenience Center" table on Page 8A-11-5, 6 in the 1996 C/K Service Manual, Page 8A-11-6, 7 in the 1997 C/K Service Manual, and Page 8A-11-5 in the 1998 C/K Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Page 9512 Underhood Fuse-Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Page 9513 Relay Box: Application and ID Underhood Fuse-Relay Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Page 9514 Underhood Fuse-Relay Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > Customer Interest: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules Wiring Harness: Customer Interest Electrical - MIL ON/DTC's Set By Various Control Modules TECHNICAL Bulletin No.: 09-06-03-004D Date: December 08, 2010 Subject: Intermittent No Crank/No Start, No Module Communication, MIL, Warning Lights, Vehicle Messages or DTCs Set by Various Control Modules - Diagnosing and Repairing Fretting Corrosion (Disconnect Affected Connector and Apply Dielectric Lubricant) Models: 2011 and Prior GM Passenger Cars and Trucks Attention: This repair can be applied to ANY electrical connection including, but not limited to: lighting, body electrical, in-line connections, powertrain control sensors, etc. DO NOT over apply lubricant to the point where it prevents the full engagement of sealed connectors. A light coating on the terminal surfaces is sufficient to correct the condition. Supercede: This bulletin is being revised to update the Attention statement and add the 2011 model year. Please discard Corporate Bulletin Number 09-06-03-004C (Section 06 Engine/Propulsion System). Condition Some customers may comment on any of the following conditions: - An intermittent no crank/no start - Intermittent malfunction indicator lamp (MIL) illumination - Intermittent service lamp illumination - Intermittent service message(s) being displayed The technician may determine that he is unable to duplicate the intermittent condition. Cause This condition may be caused by a buildup of nonconductive insulating oxidized debris known as fretting corrosion, occurring between two electrical contact surfaces of the connection or connector. This may be caused by any of the following conditions: - Vibration - Thermal cycling - Poor connection/terminal retention - Micro motion - A connector, component or wiring harness not properly secured resulting in movement On low current signal circuits this condition may cause high resistance, resulting in intermittent connections. On high current power circuits this condition may cause permanent increases in the resistance and may cause a device to become inoperative. Representative List of Control Modules and Components The following is only a representative list of control modules and components that may be affected by this connection or connector condition and DOES NOT include every possible module or component for every vehicle. - Blower Control Module - Body Control Module (BCM) - Communication Interface Module (CIM) - Cooling Fan Control Module - Electronic Brake Control Module (EBCM) - Electronic Brake and Traction Control Module (EBTCM) - Electronic Suspension Control (ESC) Module - Engine Control Module (ECM) - Heating, Ventilation and Air Conditioning (HVAC) Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > Customer Interest: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 9523 - HVAC Actuator - Inflatable Restraint Sensing and Diagnostic Module (SDM) - Any AIR BAG module - Seatbelt Lap Anchor Pretensioner - Seatbelt Retractor Pretensioner - An SIR system connection or connector condition resulting in the following DTCs being set: B0015, B0016, B0019, B0020, B0022, or B0023 - Powertrain Control Module (PCM) - Remote Control Door Lock Receiver (RCDLR) - Transmission Control Module (TCM) Correction Important DO NOT replace the control module, wiring or component for the following conditions: - The condition is intermittent and cannot be duplicated. - The condition is present and by disconnecting and reconnecting the connector the condition can no longer be duplicated. Use the following procedure to correct the conditions listed above. 1. Install a scan tool and perform the Diagnostic System Check - Vehicle. Retrieve and record any existing history or current DTCs from all of the control modules (refer to SI). ‹› If any DTC(s) are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). ‹› If DTCs are not set, refer to Symptoms - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). 2. When identified, use the appropriate DTC Diagnostics, Symptoms, Schematics, Component Connector End Views and Component Locator documents to locate and disconnect the affected harness connector(s) which are causing the condition. Note Fretting corrosion looks like little dark smudges on electrical terminals and appear where the actual electrical contact is being made. In less severe cases it may be unable to be seen or identified without the use of a magnifying glass. Important DO NOT apply an excessive amount of dielectric lubricant to the connectors as shown, as hydrolock may result when attempting to mate the connectors. Use ONLY a clean nylon brush that is dedicated to the repair of the conditions in this bulletin. 3. With a one-inch nylon bristle brush, apply dielectric lubricant to both the module/component side and the harness side of the affected connector(s). 4. Reconnect the affected connector(s) and wipe away any excess lubricant that may be present. 5. Attempt to duplicate the condition by using the following information: - DTC Diagnostic Procedure - Circuit/System Description - Conditions for Running the DTC - Conditions for Setting the DTC - Diagnostic Aids - Circuit/System Verification ‹› If the condition cannot be duplicated, the repair is complete. ‹› If the condition can be duplicated, then follow the appropriate DTC, Symptom or Circuit/System Testing procedure (refer to SI). Repair Order Documentation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > Customer Interest: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 9524 Important The following information MUST be documented on the repair order. Failure to do so may result in a chargeback. - Customer vehicle condition. - Was a Service Lamp or Service Message illuminated? If yes, specify which Service Lamp or Service Message. - Was a DTC(s) set? If yes, specify which DTC(s) were set. - After following the procedure contained within this bulletin, could the condition be duplicated? ‹› If the condition was not duplicated, then document the affected module/component connector name and number on the repair order. - If the condition was duplicated after the procedure contained within this bulletin was followed, and additional diagnosis led to the replacement of a module or component, the SI Document ID Number MUST be written on the repair order. Parts Information Alternate Distributor For All of North America Note NyoGel(R) 760G Lubricant* is equivalent to GMSPO P/N 12377900, and P/N 10953529 (Canada), specified for use to correct the condition in this bulletin. *We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for, or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > Customer Interest: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 9525 For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to refer to the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiring Harness: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules Wiring Harness: All Technical Service Bulletins Electrical - MIL ON/DTC's Set By Various Control Modules TECHNICAL Bulletin No.: 09-06-03-004D Date: December 08, 2010 Subject: Intermittent No Crank/No Start, No Module Communication, MIL, Warning Lights, Vehicle Messages or DTCs Set by Various Control Modules - Diagnosing and Repairing Fretting Corrosion (Disconnect Affected Connector and Apply Dielectric Lubricant) Models: 2011 and Prior GM Passenger Cars and Trucks Attention: This repair can be applied to ANY electrical connection including, but not limited to: lighting, body electrical, in-line connections, powertrain control sensors, etc. DO NOT over apply lubricant to the point where it prevents the full engagement of sealed connectors. A light coating on the terminal surfaces is sufficient to correct the condition. Supercede: This bulletin is being revised to update the Attention statement and add the 2011 model year. Please discard Corporate Bulletin Number 09-06-03-004C (Section 06 Engine/Propulsion System). Condition Some customers may comment on any of the following conditions: - An intermittent no crank/no start - Intermittent malfunction indicator lamp (MIL) illumination - Intermittent service lamp illumination - Intermittent service message(s) being displayed The technician may determine that he is unable to duplicate the intermittent condition. Cause This condition may be caused by a buildup of nonconductive insulating oxidized debris known as fretting corrosion, occurring between two electrical contact surfaces of the connection or connector. This may be caused by any of the following conditions: - Vibration - Thermal cycling - Poor connection/terminal retention - Micro motion - A connector, component or wiring harness not properly secured resulting in movement On low current signal circuits this condition may cause high resistance, resulting in intermittent connections. On high current power circuits this condition may cause permanent increases in the resistance and may cause a device to become inoperative. Representative List of Control Modules and Components The following is only a representative list of control modules and components that may be affected by this connection or connector condition and DOES NOT include every possible module or component for every vehicle. - Blower Control Module - Body Control Module (BCM) - Communication Interface Module (CIM) - Cooling Fan Control Module - Electronic Brake Control Module (EBCM) - Electronic Brake and Traction Control Module (EBTCM) - Electronic Suspension Control (ESC) Module - Engine Control Module (ECM) - Heating, Ventilation and Air Conditioning (HVAC) Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiring Harness: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 9531 - HVAC Actuator - Inflatable Restraint Sensing and Diagnostic Module (SDM) - Any AIR BAG module - Seatbelt Lap Anchor Pretensioner - Seatbelt Retractor Pretensioner - An SIR system connection or connector condition resulting in the following DTCs being set: B0015, B0016, B0019, B0020, B0022, or B0023 - Powertrain Control Module (PCM) - Remote Control Door Lock Receiver (RCDLR) - Transmission Control Module (TCM) Correction Important DO NOT replace the control module, wiring or component for the following conditions: - The condition is intermittent and cannot be duplicated. - The condition is present and by disconnecting and reconnecting the connector the condition can no longer be duplicated. Use the following procedure to correct the conditions listed above. 1. Install a scan tool and perform the Diagnostic System Check - Vehicle. Retrieve and record any existing history or current DTCs from all of the control modules (refer to SI). ‹› If any DTC(s) are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). ‹› If DTCs are not set, refer to Symptoms - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). 2. When identified, use the appropriate DTC Diagnostics, Symptoms, Schematics, Component Connector End Views and Component Locator documents to locate and disconnect the affected harness connector(s) which are causing the condition. Note Fretting corrosion looks like little dark smudges on electrical terminals and appear where the actual electrical contact is being made. In less severe cases it may be unable to be seen or identified without the use of a magnifying glass. Important DO NOT apply an excessive amount of dielectric lubricant to the connectors as shown, as hydrolock may result when attempting to mate the connectors. Use ONLY a clean nylon brush that is dedicated to the repair of the conditions in this bulletin. 3. With a one-inch nylon bristle brush, apply dielectric lubricant to both the module/component side and the harness side of the affected connector(s). 4. Reconnect the affected connector(s) and wipe away any excess lubricant that may be present. 5. Attempt to duplicate the condition by using the following information: - DTC Diagnostic Procedure - Circuit/System Description - Conditions for Running the DTC - Conditions for Setting the DTC - Diagnostic Aids - Circuit/System Verification ‹› If the condition cannot be duplicated, the repair is complete. ‹› If the condition can be duplicated, then follow the appropriate DTC, Symptom or Circuit/System Testing procedure (refer to SI). Repair Order Documentation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiring Harness: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 9532 Important The following information MUST be documented on the repair order. Failure to do so may result in a chargeback. - Customer vehicle condition. - Was a Service Lamp or Service Message illuminated? If yes, specify which Service Lamp or Service Message. - Was a DTC(s) set? If yes, specify which DTC(s) were set. - After following the procedure contained within this bulletin, could the condition be duplicated? ‹› If the condition was not duplicated, then document the affected module/component connector name and number on the repair order. - If the condition was duplicated after the procedure contained within this bulletin was followed, and additional diagnosis led to the replacement of a module or component, the SI Document ID Number MUST be written on the repair order. Parts Information Alternate Distributor For All of North America Note NyoGel(R) 760G Lubricant* is equivalent to GMSPO P/N 12377900, and P/N 10953529 (Canada), specified for use to correct the condition in this bulletin. *We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for, or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiring Harness: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 9533 For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to refer to the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiring Harness: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair Wiring Harness: All Technical Service Bulletins Electrical - Information For Electrical Ground Repair INFORMATION Bulletin No.: 10-08-45-001B Date: October 25, 2010 Subject: Information for Electrical Ground Repair - Use New Replacement Fasteners with Conductive Finish Models: 2011 and Prior GM Passenger Cars and Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add the 2011 model year and update the Warranty Information. Please discard Corporate Bulletin Number 10-08-45-001A (Section 08 - Body and Accessories). Electrical Ground Repair Overview Proper electrical system function relies on secure, stable and corrosion-free electrical ground connections. Loose, stripped, or corroded connections increase the possibility of improper system function and loss of module communication. These conditions may also lead to unnecessary repairs and component replacement. In general, electrical ground connections are accomplished using one, or a combination of the following attachment methods: - Welded M6 stud and nut - Welded M6 nut and bolt - Welded M8 nut and bolt Determine which attachment method is used and perform the appropriate or alternative repair as described in this bulletin. M6 Weld Stud Replacement Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. Select a location adjacent the damaged or missing M6 ground stud having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the M6 conductive rivet stud flange. 2. Using GM approved residue-free solvent or equivalent, remove any grease from the repair site and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 3. Drill a 10 mm (0.40 in) diameter hole through the panel. 4. Remove paint and primer from the area surrounding the 10 mm (0.40 in) hole until bare metal is visible. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiring Harness: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9538 Important The M6 conductive rivet stud as shown, can accommodate a panel thickness range of 0.7-4.2 mm (0.03-0.17 in). If there are layers of sheet metal, they should be touching without any air gaps to ensure a good ground. 5. Select a M6 conductive rivet stud. Refer to the Parts Information section of this bulletin. Note Use the GE-50317 rivet stud tool kit. 6. Place the M6 conductive rivet stud (1) in the 10 mm (0.40 in) hole. Assemble the rivet stud tool (2) with the groove and flare side facing the rivet stud, then the washer and the M6 nut (3). 7. Using a wrench on the rivet stud tool, and a socket on the M6 nut, secure the M6 conductive rivet stud. 8. Ensure the rivet stud is securely fastened, WITHOUT ANY detectable movement. 9. Completely wrap the threads of the rivet stud with painters tape or equivalent. Note The rivet stud and surrounding panel area MUST BE properly refinished PRIOR to the installation of the ground wire terminal and conductive nut to maintain a secure, stable and corrosion-free electrical ground. 10. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 11. Allow the refinished repair area to cure sufficiently before removing the protective material applied to the rivet stud threads. 12. Remove the painters tape or equivalent from the rivet stud threads. 13. Using GM approved residue-free solvent or equivalent, thoroughly clean the rivet stud threads to remove any adhesive and allow to dry. 14. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive rivet stud. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiring Harness: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9539 15. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 16. Install the electrical ground wire terminal to the rivet stud. 17. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 18. Install the M6 conductive nut to the rivet stud and: Tighten Tighten to 8 Nm (71 lb in). 19. Verify proper system operation. M6 Weld Nut Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M6 weld nut at the electrical ground location is damaged or stripped, a M7 conductive self-threading bolt may be used to secure the ground wire terminal. 2. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the weld nut and allow to dry. 3. Remove any loose metal particles from the damaged or stripped weld nut with a stiff brush. 4. Select a M7 conductive self-threading bolt. Refer to the Parts Information section of this bulletin 5. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M7 conductive self-threading bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 6. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 7. Install the electrical ground wire terminal to the M7 conductive self-threading bolt. 8. Install the M7 conductive self-threading bolt and: Tighten Tighten to 9 Nm (80 lb in). 9. Verify proper system operation. M6 Weld Nut Alternative Repair Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the electrical ground location is accessible from both sides of the panel, a M6 conductive bolt and a M6 conductive nut may be used to secure the electrical ground wire terminal. Refer to the Parts Information section of this bulletin. 2. Select a location adjacent the damaged M6 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the new electrical ground site. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the ground location and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 8.5 mm (0.33 in) diameter hole through the panel. 5. Remove paint and primer from the area surrounding the 8.5 mm (0.33 in) hole until bare metal is visible. 6. Select a M6 conductive bolt. Refer to the Parts Information section of this bulletin. 7. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 8. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 9. Install the electrical ground wire terminal and the M6 conductive bolt to the ground location. 10. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 11. Install the M6 conductive nut to the bolt and: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiring Harness: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9540 Tighten Tighten to 8 Nm (71 lb in). Note The repair area MUST BE properly refinished to maintain a secure, stable and corrosion-free electrical ground. 12. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 13. Verify proper system operation. M8 Weld Nut Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M8 weld nut electrical ground location is accessible from both sides of the panel, a M8 conductive bolt and a M8 conductive nut may be used to secure the electrical ground wire terminal. Refer to the Parts Information section of this bulletin. 2. Select a location adjacent the M8 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the new electrical ground site. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the ground location and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 10 mm (0.40 in) diameter hole through the panel. 5. Remove paint and primer from the area surrounding the 10 mm (0.40 in) hole until bare metal is visible. 6. Select a M8 conductive bolt. Refer to the Parts Information section of this bulletin. 7. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M8 conductive bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 8. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 9. Install the electrical ground wire terminal and the M8 conductive bolt to the ground location. 10. Select a M8 conductive nut. Refer to the Parts Information section of this bulletin. 11. Install the M8 conductive nut to the bolt and: Tighten Tighten to 22 Nm (16 lb ft). Note The repair area MUST BE properly refinished to maintain a secure, stable and corrosion-free electrical ground. 12. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 13. Verify proper system operation. M8 Weld Nut Alternative Repair Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M8 weld nut electrical ground location is not accessible from both sides of the panel, a M6 conductive rivet stud and a M6 conductive nut may be used to secure the electrical ground wire terminal. 2. Select a location adjacent the damaged M8 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the M6 conductive rivet stud flange. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the repair site and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 10 mm (0.40 in) diameter hole through the panel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiring Harness: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9541 5. Remove paint and primer from the area surrounding the 10 mm (0.40 in) until bare metal is visible. Important The M6 conductive rivet stud as shown, can accommodate a panel thickness range of 0.7-4.2 mm (0.03-0.17 in). If there are layers of sheet metal, they should be touching without any air gaps to ensure a good ground. 6. Select a M6 conductive rivet stud. Refer to the Parts Information section of this bulletin. Note Use the GE-50317 rivet stud tool kit. 7. Place the M6 conductive rivet stud (1) in the 10 mm (0.40 in) hole. Assemble the rivet stud tool (2) with the groove and flare side facing the rivet stud, then the washer and the M6 nut (3). 8. Using a wrench on the rivet stud tool, and a socket on the M6 nut, secure the M6 conductive rivet stud. 9. Ensure the new rivet stud is securely fastened, WITHOUT ANY detectable movement. 10. Completely wrap the threads of the rivet stud with painters tape or equivalent. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiring Harness: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9542 Note The rivet stud and surrounding panel area MUST BE properly refinished PRIOR to the installation of the electrical ground wire terminal and conductive nut to maintain a secure, stable and corrosion-free electrical ground. 11. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 12. Allow the refinished repair area to cure sufficiently before removing the protective material applied to the rivet stud threads. 13. Remove the painters tape or equivalent from the rivet stud threads. 14. Using GM approved residue-free solvent or equivalent, thoroughly clean the rivet stud threads to remove any adhesive and allow to dry. 15. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive rivet stud. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 16. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 17. Install the electrical ground wire terminal to the M6 conductive rivet stud. 18. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 19. Install the M6 conductive nut to the rivet stud and: Tighten Tighten to 8 Nm (71 lb in) 20. Verify proper system operation. Parts Information Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiring Harness: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9543 For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiring Harness: > 06-08-45-004 > May > 06 > Electrical - Instrument Panel & General Wiring Repair Wiring Harness: All Technical Service Bulletins Electrical - Instrument Panel & General Wiring Repair Bulletin No.: 06-08-45-004 Date: May 02, 2006 INFORMATION Subject: Instrument Panel (I/P), Body and General Wiring Harness Repair Models: 2007 and Prior GM Cars and Trucks 2003-2007 HUMMER H2 2006-2007 HUMMER H3 Important: A part restriction has been implemented on all Body and I/P harnesses and is being administered by the PQC. If a body or I/P harness replacement is required, it can take 12-28 weeks for a harness to be built and delivered to a dealer. The dealer technician is expected to repair any harness damage as the first and best choice before replacing a harness. In an effort to standardize repair practices, General Motors is requiring that all wiring harnesses be repaired instead of replaced. If there is a question concerning which connector and/or terminal you are working on, refer to the information in the appropriate Connector End Views in SI. The Instruction Manual J 38125-620, which is sent with each new update of the J 38125 Terminal Repair Kit, also has terminal crimping and terminal remove information. Important: There are some parts in the J 38125 Terminal Repair Kit (i.e. SIR connector CPAs and heat shrink tube (used in high heat area pigtail replacement) and some TPAs that are not available from GMSPO. It is vitally important that each update to the J 38125 Terminal Repair Kit be done as soon as it arrives at the dealer. Utilize the Terminal Repair Kit (J 38125) to achieve an effective wiring repair. The Terminal Repair Kit has been an essential tool for all GM Dealers since 1987. Replacement terminals and tools for this kit are available through SPX/Kent Moore. Refer to Corporate Bulletin Number 06-08-45-001 for more information. The Instruction Manual J 38125-620, which is sent with each new update to the J 38125 Terminal Repair Kit, also has terminal crimping and terminal removal information. U.S. Dealers Only - Training courses (including Tech Assists, Emerging Issues, Web, IDL and Hands-on) are available through the GM Training website. Refer to Resources and then Training Materials for a complete list of available courses. Canadian Dealers Only - Refer to the Training section of GM infoNet for a complete list of available courses and a copy of the J 38125 Terminal Repair Kit Instruction Manual. Wiring repair information is also available in Service Information (SI). The Wiring Repair section contains information for the following types of wiring repairs: - Testing for intermittent conditions and poor conditions - Flat wire repairs - GMLAN wiring repairs - High temperature wiring repairs - Splicing copper wire using splice clips - Splicing copper wire using splice sleeves - Splicing twisted or shielded cable - Splicing inline harness diodes Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiring Harness: > 06-08-45-004 > May > 06 > Electrical - Instrument Panel & General Wiring Repair > Page 9548 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wiring Harness: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair Wiring Harness: All Technical Service Bulletins Electrical - Information For Electrical Ground Repair INFORMATION Bulletin No.: 10-08-45-001B Date: October 25, 2010 Subject: Information for Electrical Ground Repair - Use New Replacement Fasteners with Conductive Finish Models: 2011 and Prior GM Passenger Cars and Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add the 2011 model year and update the Warranty Information. Please discard Corporate Bulletin Number 10-08-45-001A (Section 08 - Body and Accessories). Electrical Ground Repair Overview Proper electrical system function relies on secure, stable and corrosion-free electrical ground connections. Loose, stripped, or corroded connections increase the possibility of improper system function and loss of module communication. These conditions may also lead to unnecessary repairs and component replacement. In general, electrical ground connections are accomplished using one, or a combination of the following attachment methods: - Welded M6 stud and nut - Welded M6 nut and bolt - Welded M8 nut and bolt Determine which attachment method is used and perform the appropriate or alternative repair as described in this bulletin. M6 Weld Stud Replacement Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. Select a location adjacent the damaged or missing M6 ground stud having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the M6 conductive rivet stud flange. 2. Using GM approved residue-free solvent or equivalent, remove any grease from the repair site and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 3. Drill a 10 mm (0.40 in) diameter hole through the panel. 4. Remove paint and primer from the area surrounding the 10 mm (0.40 in) hole until bare metal is visible. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wiring Harness: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9554 Important The M6 conductive rivet stud as shown, can accommodate a panel thickness range of 0.7-4.2 mm (0.03-0.17 in). If there are layers of sheet metal, they should be touching without any air gaps to ensure a good ground. 5. Select a M6 conductive rivet stud. Refer to the Parts Information section of this bulletin. Note Use the GE-50317 rivet stud tool kit. 6. Place the M6 conductive rivet stud (1) in the 10 mm (0.40 in) hole. Assemble the rivet stud tool (2) with the groove and flare side facing the rivet stud, then the washer and the M6 nut (3). 7. Using a wrench on the rivet stud tool, and a socket on the M6 nut, secure the M6 conductive rivet stud. 8. Ensure the rivet stud is securely fastened, WITHOUT ANY detectable movement. 9. Completely wrap the threads of the rivet stud with painters tape or equivalent. Note The rivet stud and surrounding panel area MUST BE properly refinished PRIOR to the installation of the ground wire terminal and conductive nut to maintain a secure, stable and corrosion-free electrical ground. 10. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 11. Allow the refinished repair area to cure sufficiently before removing the protective material applied to the rivet stud threads. 12. Remove the painters tape or equivalent from the rivet stud threads. 13. Using GM approved residue-free solvent or equivalent, thoroughly clean the rivet stud threads to remove any adhesive and allow to dry. 14. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive rivet stud. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wiring Harness: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9555 15. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 16. Install the electrical ground wire terminal to the rivet stud. 17. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 18. Install the M6 conductive nut to the rivet stud and: Tighten Tighten to 8 Nm (71 lb in). 19. Verify proper system operation. M6 Weld Nut Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M6 weld nut at the electrical ground location is damaged or stripped, a M7 conductive self-threading bolt may be used to secure the ground wire terminal. 2. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the weld nut and allow to dry. 3. Remove any loose metal particles from the damaged or stripped weld nut with a stiff brush. 4. Select a M7 conductive self-threading bolt. Refer to the Parts Information section of this bulletin 5. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M7 conductive self-threading bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 6. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 7. Install the electrical ground wire terminal to the M7 conductive self-threading bolt. 8. Install the M7 conductive self-threading bolt and: Tighten Tighten to 9 Nm (80 lb in). 9. Verify proper system operation. M6 Weld Nut Alternative Repair Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the electrical ground location is accessible from both sides of the panel, a M6 conductive bolt and a M6 conductive nut may be used to secure the electrical ground wire terminal. Refer to the Parts Information section of this bulletin. 2. Select a location adjacent the damaged M6 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the new electrical ground site. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the ground location and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 8.5 mm (0.33 in) diameter hole through the panel. 5. Remove paint and primer from the area surrounding the 8.5 mm (0.33 in) hole until bare metal is visible. 6. Select a M6 conductive bolt. Refer to the Parts Information section of this bulletin. 7. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 8. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 9. Install the electrical ground wire terminal and the M6 conductive bolt to the ground location. 10. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 11. Install the M6 conductive nut to the bolt and: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wiring Harness: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9556 Tighten Tighten to 8 Nm (71 lb in). Note The repair area MUST BE properly refinished to maintain a secure, stable and corrosion-free electrical ground. 12. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 13. Verify proper system operation. M8 Weld Nut Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M8 weld nut electrical ground location is accessible from both sides of the panel, a M8 conductive bolt and a M8 conductive nut may be used to secure the electrical ground wire terminal. Refer to the Parts Information section of this bulletin. 2. Select a location adjacent the M8 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the new electrical ground site. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the ground location and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 10 mm (0.40 in) diameter hole through the panel. 5. Remove paint and primer from the area surrounding the 10 mm (0.40 in) hole until bare metal is visible. 6. Select a M8 conductive bolt. Refer to the Parts Information section of this bulletin. 7. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M8 conductive bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 8. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 9. Install the electrical ground wire terminal and the M8 conductive bolt to the ground location. 10. Select a M8 conductive nut. Refer to the Parts Information section of this bulletin. 11. Install the M8 conductive nut to the bolt and: Tighten Tighten to 22 Nm (16 lb ft). Note The repair area MUST BE properly refinished to maintain a secure, stable and corrosion-free electrical ground. 12. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 13. Verify proper system operation. M8 Weld Nut Alternative Repair Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M8 weld nut electrical ground location is not accessible from both sides of the panel, a M6 conductive rivet stud and a M6 conductive nut may be used to secure the electrical ground wire terminal. 2. Select a location adjacent the damaged M8 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the M6 conductive rivet stud flange. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the repair site and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 10 mm (0.40 in) diameter hole through the panel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wiring Harness: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9557 5. Remove paint and primer from the area surrounding the 10 mm (0.40 in) until bare metal is visible. Important The M6 conductive rivet stud as shown, can accommodate a panel thickness range of 0.7-4.2 mm (0.03-0.17 in). If there are layers of sheet metal, they should be touching without any air gaps to ensure a good ground. 6. Select a M6 conductive rivet stud. Refer to the Parts Information section of this bulletin. Note Use the GE-50317 rivet stud tool kit. 7. Place the M6 conductive rivet stud (1) in the 10 mm (0.40 in) hole. Assemble the rivet stud tool (2) with the groove and flare side facing the rivet stud, then the washer and the M6 nut (3). 8. Using a wrench on the rivet stud tool, and a socket on the M6 nut, secure the M6 conductive rivet stud. 9. Ensure the new rivet stud is securely fastened, WITHOUT ANY detectable movement. 10. Completely wrap the threads of the rivet stud with painters tape or equivalent. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wiring Harness: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9558 Note The rivet stud and surrounding panel area MUST BE properly refinished PRIOR to the installation of the electrical ground wire terminal and conductive nut to maintain a secure, stable and corrosion-free electrical ground. 11. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 12. Allow the refinished repair area to cure sufficiently before removing the protective material applied to the rivet stud threads. 13. Remove the painters tape or equivalent from the rivet stud threads. 14. Using GM approved residue-free solvent or equivalent, thoroughly clean the rivet stud threads to remove any adhesive and allow to dry. 15. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive rivet stud. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 16. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 17. Install the electrical ground wire terminal to the M6 conductive rivet stud. 18. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 19. Install the M6 conductive nut to the rivet stud and: Tighten Tighten to 8 Nm (71 lb in) 20. Verify proper system operation. Parts Information Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wiring Harness: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9559 For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wiring Harness: > 06-08-45-004 > May > 06 > Electrical - Instrument Panel & General Wiring Repair Wiring Harness: All Technical Service Bulletins Electrical - Instrument Panel & General Wiring Repair Bulletin No.: 06-08-45-004 Date: May 02, 2006 INFORMATION Subject: Instrument Panel (I/P), Body and General Wiring Harness Repair Models: 2007 and Prior GM Cars and Trucks 2003-2007 HUMMER H2 2006-2007 HUMMER H3 Important: A part restriction has been implemented on all Body and I/P harnesses and is being administered by the PQC. If a body or I/P harness replacement is required, it can take 12-28 weeks for a harness to be built and delivered to a dealer. The dealer technician is expected to repair any harness damage as the first and best choice before replacing a harness. In an effort to standardize repair practices, General Motors is requiring that all wiring harnesses be repaired instead of replaced. If there is a question concerning which connector and/or terminal you are working on, refer to the information in the appropriate Connector End Views in SI. The Instruction Manual J 38125-620, which is sent with each new update of the J 38125 Terminal Repair Kit, also has terminal crimping and terminal remove information. Important: There are some parts in the J 38125 Terminal Repair Kit (i.e. SIR connector CPAs and heat shrink tube (used in high heat area pigtail replacement) and some TPAs that are not available from GMSPO. It is vitally important that each update to the J 38125 Terminal Repair Kit be done as soon as it arrives at the dealer. Utilize the Terminal Repair Kit (J 38125) to achieve an effective wiring repair. The Terminal Repair Kit has been an essential tool for all GM Dealers since 1987. Replacement terminals and tools for this kit are available through SPX/Kent Moore. Refer to Corporate Bulletin Number 06-08-45-001 for more information. The Instruction Manual J 38125-620, which is sent with each new update to the J 38125 Terminal Repair Kit, also has terminal crimping and terminal removal information. U.S. Dealers Only - Training courses (including Tech Assists, Emerging Issues, Web, IDL and Hands-on) are available through the GM Training website. Refer to Resources and then Training Materials for a complete list of available courses. Canadian Dealers Only - Refer to the Training section of GM infoNet for a complete list of available courses and a copy of the J 38125 Terminal Repair Kit Instruction Manual. Wiring repair information is also available in Service Information (SI). The Wiring Repair section contains information for the following types of wiring repairs: - Testing for intermittent conditions and poor conditions - Flat wire repairs - GMLAN wiring repairs - High temperature wiring repairs - Splicing copper wire using splice clips - Splicing copper wire using splice sleeves - Splicing twisted or shielded cable - Splicing inline harness diodes Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Starting and Charging > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wiring Harness: > 06-08-45-004 > May > 06 > Electrical - Instrument Panel & General Wiring Repair > Page 9564 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Auxiliary Power Outlet > Component Information > Technical Service Bulletins > Customer Interest for Auxiliary Power Outlet: > 99-08-45-005 > Nov > 99 > Accessory Receptacle/Cigar Lighter - Inoperative Auxiliary Power Outlet: Customer Interest Accessory Receptacle/Cigar Lighter - Inoperative File In Section: 08 - Body and Accessories Bulletin No.: 99-08-45-005 Date: November, 1999 TECHNICAL Subject: Accessory Receptacle/Cigar Lighter is Inoperative (Check Aftermarket Device Plug for Short to Ground) Models: 1995-2000 Passenger Cars and Trucks Condition Some customers may comment that the cigar lighter or the accessory receptacle is inoperative; or that the internal fuse (within the plug on an aftermarket device), blows intermittently. Cause Certain aftermarket devices have a newly designed power plug with an internal mini fuse. The mini fuse may have an external terminal (which may be used to externally check the fuse). If the mini fuse external test terminal is not recessed into the mini fuse body, it may come in contact with the shell of the vehicle receptacle and cause the fuse (of either the vehicle or the aftermarket device), to blow intermittently. Correction Test the aftermarket device plug for short to ground. The following step may be performed at the customer's expense. As this is not a defect in material, design or workmanship of the vehicle, it would be the owner's responsibility. 1. Place a piece of tape over the mini fuse terminal temporarily. 2. Explain to the customer that the fuse for the device must have no exposed terminals, and that finding one would be his responsibility. 3. Refer the customer to the manufacturer of the aftermarket device for a new plug. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Auxiliary Power Outlet > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Auxiliary Power Outlet: > 99-08-45-005 > Nov > 99 > Accessory Receptacle/Cigar Lighter - Inoperative Auxiliary Power Outlet: All Technical Service Bulletins Accessory Receptacle/Cigar Lighter Inoperative File In Section: 08 - Body and Accessories Bulletin No.: 99-08-45-005 Date: November, 1999 TECHNICAL Subject: Accessory Receptacle/Cigar Lighter is Inoperative (Check Aftermarket Device Plug for Short to Ground) Models: 1995-2000 Passenger Cars and Trucks Condition Some customers may comment that the cigar lighter or the accessory receptacle is inoperative; or that the internal fuse (within the plug on an aftermarket device), blows intermittently. Cause Certain aftermarket devices have a newly designed power plug with an internal mini fuse. The mini fuse may have an external terminal (which may be used to externally check the fuse). If the mini fuse external test terminal is not recessed into the mini fuse body, it may come in contact with the shell of the vehicle receptacle and cause the fuse (of either the vehicle or the aftermarket device), to blow intermittently. Correction Test the aftermarket device plug for short to ground. The following step may be performed at the customer's expense. As this is not a defect in material, design or workmanship of the vehicle, it would be the owner's responsibility. 1. Place a piece of tape over the mini fuse terminal temporarily. 2. Explain to the customer that the fuse for the device must have no exposed terminals, and that finding one would be his responsibility. 3. Refer the customer to the manufacturer of the aftermarket device for a new plug. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Auxiliary Power Outlet > Component Information > Locations > Auxiliary Power Connectors Auxiliary Power Outlet: Locations Auxiliary Power Connectors Center of I/P area, in Ash Tray Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Auxiliary Power Outlet > Component Information > Locations > Auxiliary Power Connectors > Page 9581 Auxiliary Power Outlet: Locations Spare Power Source Under LH side of I/P, on Bulkhead Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Fuse > Component Information > Technical Service Bulletins > Electrical - Aftermarket Fuse Warning Fuse: Technical Service Bulletins Electrical - Aftermarket Fuse Warning Bulletin No.: 07-08-45-002 Date: September 05, 2007 ADVANCED SERVICE INFORMATION Subject: Service Alert: Concerns With Aftermarket Fuses in GM Vehicles Models: 2008 and Prior GM Passenger Cars and Light Duty Trucks (including Saturn) 2008 and Prior HUMMER H2, H3 2008 and Prior Saab 9-7X Concerns with Harbor Freight Tools "Storehouse" Branded Blade Type Fuses General Motors has become aware of a fuse recall by Harbor Freight Tools/Storehouse for a variety of aftermarket fuses. In two cases, these fuses have not provided protection for the wiring system of the vehicles they were customer installed in. Upon testing the 15 amp version, it was found that the fuse still would not "open" when shorted directly across the battery terminals. How to Identify These Fuses Packed in a 120 piece set, the fuse has a translucent, hard plastic, blue body with the amperage stamped into the top. There are no white painted numbers on the fuse to indicate amperage. There are no identifying marks on the fuse to tell who is making it. The fuses are known to be distributed by Harbor Freight Tools but there may be other marketers, and packaging of this style of fuse. It would be prudent to replace these fuses if found in a customers vehicle. Likewise, if wiring overheating is found you should check the fuse panel for the presence of this style of fuse. All GM dealers should use genuine GM fuses on the vehicles they service. You should also encourage the use of GM fuses to your customers to assure they are getting the required electrical system protection. GM has no knowledge of any concerns with other aftermarket fuses. If additional information becomes available, this bulletin will be updated. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Fuse > Component Information > Technical Service Bulletins > Page 9586 Instrument Panel Wiring, LH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Fuse > Component Information > Application and ID > I/P Fuse Block Fuse: Application and ID I/P Fuse Block I/P Fuse Block (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Fuse > Component Information > Application and ID > I/P Fuse Block > Page 9589 I/P Fuse Block (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Fuse > Component Information > Application and ID > I/P Fuse Block > Page 9590 Fuse: Application and ID Convenience Center Convenience Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Fuse > Component Information > Application and ID > I/P Fuse Block > Page 9591 Convenience Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Fuse > Component Information > Application and ID > I/P Fuse Block > Page 9592 Fuse: Application and ID Underhood Fuse/Relay Center Underhood Fuse-Relay Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Fuse > Component Information > Application and ID > I/P Fuse Block > Page 9593 Underhood Fuse-Relay Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Fuse Block > Component Information > Locations > Convenience Center Fuse Block: Locations Convenience Center Convenience Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Fuse Block > Component Information > Locations > Convenience Center > Page 9598 Instrument Panel Wiring, LH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Fuse Block > Component Information > Locations > Convenience Center > Page 9599 Underhood Fuse-Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Fuse Block > Component Information > Locations > Page 9600 C210: Cross Body HARN To Convenience Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Fuse Block > Component Information > Application and ID > I/P Fuse Block Fuse Block: Application and ID I/P Fuse Block I/P Fuse Block (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Fuse Block > Component Information > Application and ID > I/P Fuse Block > Page 9603 I/P Fuse Block (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Fuse Block > Component Information > Application and ID > I/P Fuse Block > Page 9604 Fuse Block: Application and ID Underhood Fuse/Relay Center Underhood Fuse-Relay Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Fuse Block > Component Information > Application and ID > I/P Fuse Block > Page 9605 Underhood Fuse-Relay Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Fuse Block > Component Information > Application and ID > I/P Fuse Block > Page 9606 Fuse Block: Application and ID Convenience Center Convenience Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Fuse Block > Component Information > Application and ID > I/P Fuse Block > Page 9607 Convenience Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > Customer Interest: > 66-71-04 > May > 96 > A/T - 1-2 or 2-3 Slip/Flare, Launch Shudder & DTC P1870 Grounding Point: Customer Interest A/T - 1-2 or 2-3 Slip/Flare, Launch Shudder & DTC P1870 66-71-04 CHEVROLET Issued: 05/10/96 SUBJECT: AUTOMATIC TRANSMISSION 1-2 AND/OR 2-3 UPSHIFT SLIP/FLARE, NO 3RD OR 4TH GEAR, LAUNCH SHUDDER, DTC P1870 (REVISE VCM WIRING) MODELS: 1996 CHEVROLET AND GMC C/K, S/T, M/L, G1, G2 AND P3 MODELS 1996 OLDSMOBILE BRAVADA WITH VCM AND 4L60-E (M30) OR 4L80-E (M11) AUTOMATIC TRANSMISSION CONDITION: SOME OWNERS MAY COMMENT THAT THE AUTOMATIC TRANSMISSION HAS EITHER A SLIP OR FLARE ON THE 1-2 AND/OR 2-3 UPSHIFT, OR NO 3RD OR 4TH GEAR, OR LAUNCH SHUDDER. DTC P1870 MAY ALSO BE STORED IN THE VCM. CAUSE: A POOR INTERNAL GROUND BETWEEN THE TWO CIRCUIT BOARDS OF THE VCM CAN CAUSE THE VCM TO COMMAND ERRATIC LINE PRESSURE AT THE PRESSURE CONTROL SOLENOIDS (PCS). CORRECTION: USING HARNESS JUMPER WIRE AND INSTRUCTION KIT, P/N 12167310, REVISE THE WIRING HARNESS AT THE VCM CONNECTOR. CORRECTIONS WERE MADE TO THE VCM BEGINNING 2/14/96. THE CORRECTED VCM'S ARE IDENTIFIED WITH SERVICE NUMBER 16244210 ON THE VCM IDENTIFICATION LABEL. SERVICE PROCEDURE THE FOLLOWING IS A SUMMARY OF THE INSTRUCTIONS INCLUDED WITH THE SERVICE KIT: 1. REMOVE THE NEGATIVE TERMINAL FROM THE BATTERY. 2. MOVE THE WIRE LOCATED AT CONNECTOR J3 (WHITE/GRAY/CLEAR), PIN 18 TO CONNECTOR J1 (BLUE), PIN 23. 3. INSTALL THE JUMPER WIRE BETWEEN CONNECTOR J2 (RED), PIN 26 AND CONNECTOR J3 (WHITE/GREY/CLEAR), PIN 18. 4. INSTALL THE TAG INCLUDED IN THE KIT AROUND THE VCM WIRING HARNESS. THIS TAG NOTES THAT THE WIRING HARNESS HAS BEEN MODIFIED. 5. RECONNECT THE NEGATIVE BATTERY TERMINAL. ROAD TEST TO VERIFY THAT THE CONDITION HAS BEEN CORRECTED. IF ANY OF THE FOLLOWING CONDITIONS ARE NOTED, THE TRANSMISSION SHOULD BE REPLACED, OR FOR CANADIAN DEALERS, REPAIRED. - TRANSMISSION FLUID OXIDATION OR EXCESSIVE SEDIMENT. - TRANSMISSION SLIP OR FLARE AFTER THIS SERVICE FIX IS PERFORMED. - DTC P1870 IS STORED ON A 4L60-E (M30). THE FOLLOWING TOOLS ARE AVAILABLE FROM KENT-MOORE (1-800-345-2233) FOR USE IN REMOVING AND RELATING THE VCM CONNECTOR. - J41759 PUNCH: USED TO PUNCH A NEW HOLE THROUGH THE CONNECTOR SEAL. PARTS INFORMATION P/N DESCRIPTION QTY 12167310 HARNESS JUMPER WIRE KIT 1 PARTS ARE EXPECTED TO BE AVAILABLE ON 5/13/96 FROM GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > Customer Interest: > 66-71-04 > May > 96 > A/T - 1-2 or 2-3 Slip/Flare, Launch Shudder & DTC P1870 > Page 9616 WARRANTY INFORMATION FOR VEHICLES REPAIRED UNDER WARRANTY, USE: LABOR OP DESCRIPTION LABOR TIME N6112 WIRE REPAIR USE PUBLISHED FRONT CHASSIS LABOR OPERATION TIME Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair Grounding Point: All Technical Service Bulletins Electrical - Information For Electrical Ground Repair INFORMATION Bulletin No.: 10-08-45-001B Date: October 25, 2010 Subject: Information for Electrical Ground Repair - Use New Replacement Fasteners with Conductive Finish Models: 2011 and Prior GM Passenger Cars and Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add the 2011 model year and update the Warranty Information. Please discard Corporate Bulletin Number 10-08-45-001A (Section 08 - Body and Accessories). Electrical Ground Repair Overview Proper electrical system function relies on secure, stable and corrosion-free electrical ground connections. Loose, stripped, or corroded connections increase the possibility of improper system function and loss of module communication. These conditions may also lead to unnecessary repairs and component replacement. In general, electrical ground connections are accomplished using one, or a combination of the following attachment methods: - Welded M6 stud and nut - Welded M6 nut and bolt - Welded M8 nut and bolt Determine which attachment method is used and perform the appropriate or alternative repair as described in this bulletin. M6 Weld Stud Replacement Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. Select a location adjacent the damaged or missing M6 ground stud having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the M6 conductive rivet stud flange. 2. Using GM approved residue-free solvent or equivalent, remove any grease from the repair site and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 3. Drill a 10 mm (0.40 in) diameter hole through the panel. 4. Remove paint and primer from the area surrounding the 10 mm (0.40 in) hole until bare metal is visible. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9622 Important The M6 conductive rivet stud as shown, can accommodate a panel thickness range of 0.7-4.2 mm (0.03-0.17 in). If there are layers of sheet metal, they should be touching without any air gaps to ensure a good ground. 5. Select a M6 conductive rivet stud. Refer to the Parts Information section of this bulletin. Note Use the GE-50317 rivet stud tool kit. 6. Place the M6 conductive rivet stud (1) in the 10 mm (0.40 in) hole. Assemble the rivet stud tool (2) with the groove and flare side facing the rivet stud, then the washer and the M6 nut (3). 7. Using a wrench on the rivet stud tool, and a socket on the M6 nut, secure the M6 conductive rivet stud. 8. Ensure the rivet stud is securely fastened, WITHOUT ANY detectable movement. 9. Completely wrap the threads of the rivet stud with painters tape or equivalent. Note The rivet stud and surrounding panel area MUST BE properly refinished PRIOR to the installation of the ground wire terminal and conductive nut to maintain a secure, stable and corrosion-free electrical ground. 10. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 11. Allow the refinished repair area to cure sufficiently before removing the protective material applied to the rivet stud threads. 12. Remove the painters tape or equivalent from the rivet stud threads. 13. Using GM approved residue-free solvent or equivalent, thoroughly clean the rivet stud threads to remove any adhesive and allow to dry. 14. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive rivet stud. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9623 15. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 16. Install the electrical ground wire terminal to the rivet stud. 17. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 18. Install the M6 conductive nut to the rivet stud and: Tighten Tighten to 8 Nm (71 lb in). 19. Verify proper system operation. M6 Weld Nut Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M6 weld nut at the electrical ground location is damaged or stripped, a M7 conductive self-threading bolt may be used to secure the ground wire terminal. 2. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the weld nut and allow to dry. 3. Remove any loose metal particles from the damaged or stripped weld nut with a stiff brush. 4. Select a M7 conductive self-threading bolt. Refer to the Parts Information section of this bulletin 5. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M7 conductive self-threading bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 6. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 7. Install the electrical ground wire terminal to the M7 conductive self-threading bolt. 8. Install the M7 conductive self-threading bolt and: Tighten Tighten to 9 Nm (80 lb in). 9. Verify proper system operation. M6 Weld Nut Alternative Repair Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the electrical ground location is accessible from both sides of the panel, a M6 conductive bolt and a M6 conductive nut may be used to secure the electrical ground wire terminal. Refer to the Parts Information section of this bulletin. 2. Select a location adjacent the damaged M6 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the new electrical ground site. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the ground location and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 8.5 mm (0.33 in) diameter hole through the panel. 5. Remove paint and primer from the area surrounding the 8.5 mm (0.33 in) hole until bare metal is visible. 6. Select a M6 conductive bolt. Refer to the Parts Information section of this bulletin. 7. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 8. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 9. Install the electrical ground wire terminal and the M6 conductive bolt to the ground location. 10. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 11. Install the M6 conductive nut to the bolt and: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9624 Tighten Tighten to 8 Nm (71 lb in). Note The repair area MUST BE properly refinished to maintain a secure, stable and corrosion-free electrical ground. 12. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 13. Verify proper system operation. M8 Weld Nut Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M8 weld nut electrical ground location is accessible from both sides of the panel, a M8 conductive bolt and a M8 conductive nut may be used to secure the electrical ground wire terminal. Refer to the Parts Information section of this bulletin. 2. Select a location adjacent the M8 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the new electrical ground site. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the ground location and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 10 mm (0.40 in) diameter hole through the panel. 5. Remove paint and primer from the area surrounding the 10 mm (0.40 in) hole until bare metal is visible. 6. Select a M8 conductive bolt. Refer to the Parts Information section of this bulletin. 7. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M8 conductive bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 8. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 9. Install the electrical ground wire terminal and the M8 conductive bolt to the ground location. 10. Select a M8 conductive nut. Refer to the Parts Information section of this bulletin. 11. Install the M8 conductive nut to the bolt and: Tighten Tighten to 22 Nm (16 lb ft). Note The repair area MUST BE properly refinished to maintain a secure, stable and corrosion-free electrical ground. 12. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 13. Verify proper system operation. M8 Weld Nut Alternative Repair Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M8 weld nut electrical ground location is not accessible from both sides of the panel, a M6 conductive rivet stud and a M6 conductive nut may be used to secure the electrical ground wire terminal. 2. Select a location adjacent the damaged M8 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the M6 conductive rivet stud flange. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the repair site and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 10 mm (0.40 in) diameter hole through the panel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9625 5. Remove paint and primer from the area surrounding the 10 mm (0.40 in) until bare metal is visible. Important The M6 conductive rivet stud as shown, can accommodate a panel thickness range of 0.7-4.2 mm (0.03-0.17 in). If there are layers of sheet metal, they should be touching without any air gaps to ensure a good ground. 6. Select a M6 conductive rivet stud. Refer to the Parts Information section of this bulletin. Note Use the GE-50317 rivet stud tool kit. 7. Place the M6 conductive rivet stud (1) in the 10 mm (0.40 in) hole. Assemble the rivet stud tool (2) with the groove and flare side facing the rivet stud, then the washer and the M6 nut (3). 8. Using a wrench on the rivet stud tool, and a socket on the M6 nut, secure the M6 conductive rivet stud. 9. Ensure the new rivet stud is securely fastened, WITHOUT ANY detectable movement. 10. Completely wrap the threads of the rivet stud with painters tape or equivalent. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9626 Note The rivet stud and surrounding panel area MUST BE properly refinished PRIOR to the installation of the electrical ground wire terminal and conductive nut to maintain a secure, stable and corrosion-free electrical ground. 11. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 12. Allow the refinished repair area to cure sufficiently before removing the protective material applied to the rivet stud threads. 13. Remove the painters tape or equivalent from the rivet stud threads. 14. Using GM approved residue-free solvent or equivalent, thoroughly clean the rivet stud threads to remove any adhesive and allow to dry. 15. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive rivet stud. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 16. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 17. Install the electrical ground wire terminal to the M6 conductive rivet stud. 18. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 19. Install the M6 conductive nut to the rivet stud and: Tighten Tighten to 8 Nm (71 lb in) 20. Verify proper system operation. Parts Information Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9627 For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 66-71-04 > May > 96 > A/T - 1-2 or 2-3 Slip/Flare, Launch Shudder & DTC P1870 Grounding Point: All Technical Service Bulletins A/T - 1-2 or 2-3 Slip/Flare, Launch Shudder & DTC P1870 66-71-04 CHEVROLET Issued: 05/10/96 SUBJECT: AUTOMATIC TRANSMISSION 1-2 AND/OR 2-3 UPSHIFT SLIP/FLARE, NO 3RD OR 4TH GEAR, LAUNCH SHUDDER, DTC P1870 (REVISE VCM WIRING) MODELS: 1996 CHEVROLET AND GMC C/K, S/T, M/L, G1, G2 AND P3 MODELS 1996 OLDSMOBILE BRAVADA WITH VCM AND 4L60-E (M30) OR 4L80-E (M11) AUTOMATIC TRANSMISSION CONDITION: SOME OWNERS MAY COMMENT THAT THE AUTOMATIC TRANSMISSION HAS EITHER A SLIP OR FLARE ON THE 1-2 AND/OR 2-3 UPSHIFT, OR NO 3RD OR 4TH GEAR, OR LAUNCH SHUDDER. DTC P1870 MAY ALSO BE STORED IN THE VCM. CAUSE: A POOR INTERNAL GROUND BETWEEN THE TWO CIRCUIT BOARDS OF THE VCM CAN CAUSE THE VCM TO COMMAND ERRATIC LINE PRESSURE AT THE PRESSURE CONTROL SOLENOIDS (PCS). CORRECTION: USING HARNESS JUMPER WIRE AND INSTRUCTION KIT, P/N 12167310, REVISE THE WIRING HARNESS AT THE VCM CONNECTOR. CORRECTIONS WERE MADE TO THE VCM BEGINNING 2/14/96. THE CORRECTED VCM'S ARE IDENTIFIED WITH SERVICE NUMBER 16244210 ON THE VCM IDENTIFICATION LABEL. SERVICE PROCEDURE THE FOLLOWING IS A SUMMARY OF THE INSTRUCTIONS INCLUDED WITH THE SERVICE KIT: 1. REMOVE THE NEGATIVE TERMINAL FROM THE BATTERY. 2. MOVE THE WIRE LOCATED AT CONNECTOR J3 (WHITE/GRAY/CLEAR), PIN 18 TO CONNECTOR J1 (BLUE), PIN 23. 3. INSTALL THE JUMPER WIRE BETWEEN CONNECTOR J2 (RED), PIN 26 AND CONNECTOR J3 (WHITE/GREY/CLEAR), PIN 18. 4. INSTALL THE TAG INCLUDED IN THE KIT AROUND THE VCM WIRING HARNESS. THIS TAG NOTES THAT THE WIRING HARNESS HAS BEEN MODIFIED. 5. RECONNECT THE NEGATIVE BATTERY TERMINAL. ROAD TEST TO VERIFY THAT THE CONDITION HAS BEEN CORRECTED. IF ANY OF THE FOLLOWING CONDITIONS ARE NOTED, THE TRANSMISSION SHOULD BE REPLACED, OR FOR CANADIAN DEALERS, REPAIRED. - TRANSMISSION FLUID OXIDATION OR EXCESSIVE SEDIMENT. - TRANSMISSION SLIP OR FLARE AFTER THIS SERVICE FIX IS PERFORMED. - DTC P1870 IS STORED ON A 4L60-E (M30). THE FOLLOWING TOOLS ARE AVAILABLE FROM KENT-MOORE (1-800-345-2233) FOR USE IN REMOVING AND RELATING THE VCM CONNECTOR. - J41759 PUNCH: USED TO PUNCH A NEW HOLE THROUGH THE CONNECTOR SEAL. PARTS INFORMATION P/N DESCRIPTION QTY 12167310 HARNESS JUMPER WIRE KIT 1 PARTS ARE EXPECTED TO BE AVAILABLE ON 5/13/96 FROM GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 66-71-04 > May > 96 > A/T - 1-2 or 2-3 Slip/Flare, Launch Shudder & DTC P1870 > Page 9632 WARRANTY INFORMATION FOR VEHICLES REPAIRED UNDER WARRANTY, USE: LABOR OP DESCRIPTION LABOR TIME N6112 WIRE REPAIR USE PUBLISHED FRONT CHASSIS LABOR OPERATION TIME Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Other Service Bulletins for Grounding Point: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON Torque Converter Clutch Solenoid: All Technical Service Bulletins A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON File In Section: 07 - Transmission/Transaxle Bulletin No.: 01-07-30-023B Date: March, 2002 TECHNICAL Subject: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) Models: 1996 Buick Roadmaster 1996 Cadillac Fleetwood 1999-2000 Cadillac Escalade 1996-2000 Chevrolet Camaro, Corvette 1996-2000 Pontiac Firebird 1996-2000 Chevrolet and GMC Light Duty Truck Models 1996-2000 Oldsmobile Bravada with 4L60-E Automatic Transmission (RPO M30) Built Prior to January 15, 2000 (Julian Date 0015) This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 Transmission/Transaxle). Condition Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated. Diagnosis Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs. The scan tool may show a DTC P1870 set as a history code. A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93° C (200°F). Cause The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply. Important: ^ DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code. ^ When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result. ^ This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle). ^ When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code. ^ When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL). Correction Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Other Service Bulletins for Grounding Point: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 9638 regulator and isolator valves. Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body. ^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears). ^ The torque converter is not blue or overheated. ^ The transmission fluid is not burned or has no burned odor ^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Other Service Bulletins for Grounding Point: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 9639 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Other Service Bulletins for Grounding Point: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 9645 regulator and isolator valves. Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body. ^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears). ^ The torque converter is not blue or overheated. ^ The transmission fluid is not burned or has no burned odor ^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Grounding Point > Component Information > Technical Service Bulletins > All Other Service Bulletins for Grounding Point: > 01-07-30-023B > Mar > 02 > A/T - 4L60-E Harsh 1-2 Gear Upshift/MIL/SES/CEL ON > Page 9646 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Relays and Modules - Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Electrical - Revised Convenience Center Cavity ID Relay Box: Technical Service Bulletins Electrical - Revised Convenience Center Cavity ID File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-82-08 Date: August, 1997 SERVICE MANUAL UPDATE Subject: Section 8A-11 Fuse Block Details Revised Convenience Center Table Models: 1996-98 Chevrolet and GMC C/K models. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Relays and Modules - Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Electrical - Revised Convenience Center Cavity ID > Page 9652 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Relays and Modules - Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Electrical - Revised Convenience Center Cavity ID > Page 9653 This bulletin revises "Convenience Center" table on Page 8A-11-5, 6 in the 1996 C/K Service Manual, Page 8A-11-6, 7 in the 1997 C/K Service Manual, and Page 8A-11-5 in the 1998 C/K Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Relays and Modules - Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Page 9654 Underhood Fuse-Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Relays and Modules - Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Page 9655 Relay Box: Application and ID Underhood Fuse-Relay Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Relays and Modules - Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Page 9656 Underhood Fuse-Relay Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Electrical - Revised Convenience Center Cavity ID Relay Box: Technical Service Bulletins Electrical - Revised Convenience Center Cavity ID File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-82-08 Date: August, 1997 SERVICE MANUAL UPDATE Subject: Section 8A-11 Fuse Block Details Revised Convenience Center Table Models: 1996-98 Chevrolet and GMC C/K models. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Electrical - Revised Convenience Center Cavity ID > Page 9661 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Electrical - Revised Convenience Center Cavity ID > Page 9662 This bulletin revises "Convenience Center" table on Page 8A-11-5, 6 in the 1996 C/K Service Manual, Page 8A-11-6, 7 in the 1997 C/K Service Manual, and Page 8A-11-5 in the 1998 C/K Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Page 9663 Underhood Fuse-Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Page 9664 Relay Box: Application and ID Underhood Fuse-Relay Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Relay Box > Component Information > Technical Service Bulletins > Page 9665 Underhood Fuse-Relay Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > Customer Interest: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules Wiring Harness: Customer Interest Electrical - MIL ON/DTC's Set By Various Control Modules TECHNICAL Bulletin No.: 09-06-03-004D Date: December 08, 2010 Subject: Intermittent No Crank/No Start, No Module Communication, MIL, Warning Lights, Vehicle Messages or DTCs Set by Various Control Modules - Diagnosing and Repairing Fretting Corrosion (Disconnect Affected Connector and Apply Dielectric Lubricant) Models: 2011 and Prior GM Passenger Cars and Trucks Attention: This repair can be applied to ANY electrical connection including, but not limited to: lighting, body electrical, in-line connections, powertrain control sensors, etc. DO NOT over apply lubricant to the point where it prevents the full engagement of sealed connectors. A light coating on the terminal surfaces is sufficient to correct the condition. Supercede: This bulletin is being revised to update the Attention statement and add the 2011 model year. Please discard Corporate Bulletin Number 09-06-03-004C (Section 06 Engine/Propulsion System). Condition Some customers may comment on any of the following conditions: - An intermittent no crank/no start - Intermittent malfunction indicator lamp (MIL) illumination - Intermittent service lamp illumination - Intermittent service message(s) being displayed The technician may determine that he is unable to duplicate the intermittent condition. Cause This condition may be caused by a buildup of nonconductive insulating oxidized debris known as fretting corrosion, occurring between two electrical contact surfaces of the connection or connector. This may be caused by any of the following conditions: - Vibration - Thermal cycling - Poor connection/terminal retention - Micro motion - A connector, component or wiring harness not properly secured resulting in movement On low current signal circuits this condition may cause high resistance, resulting in intermittent connections. On high current power circuits this condition may cause permanent increases in the resistance and may cause a device to become inoperative. Representative List of Control Modules and Components The following is only a representative list of control modules and components that may be affected by this connection or connector condition and DOES NOT include every possible module or component for every vehicle. - Blower Control Module - Body Control Module (BCM) - Communication Interface Module (CIM) - Cooling Fan Control Module - Electronic Brake Control Module (EBCM) - Electronic Brake and Traction Control Module (EBTCM) - Electronic Suspension Control (ESC) Module - Engine Control Module (ECM) - Heating, Ventilation and Air Conditioning (HVAC) Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > Customer Interest: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 9674 - HVAC Actuator - Inflatable Restraint Sensing and Diagnostic Module (SDM) - Any AIR BAG module - Seatbelt Lap Anchor Pretensioner - Seatbelt Retractor Pretensioner - An SIR system connection or connector condition resulting in the following DTCs being set: B0015, B0016, B0019, B0020, B0022, or B0023 - Powertrain Control Module (PCM) - Remote Control Door Lock Receiver (RCDLR) - Transmission Control Module (TCM) Correction Important DO NOT replace the control module, wiring or component for the following conditions: - The condition is intermittent and cannot be duplicated. - The condition is present and by disconnecting and reconnecting the connector the condition can no longer be duplicated. Use the following procedure to correct the conditions listed above. 1. Install a scan tool and perform the Diagnostic System Check - Vehicle. Retrieve and record any existing history or current DTCs from all of the control modules (refer to SI). ‹› If any DTC(s) are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). ‹› If DTCs are not set, refer to Symptoms - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). 2. When identified, use the appropriate DTC Diagnostics, Symptoms, Schematics, Component Connector End Views and Component Locator documents to locate and disconnect the affected harness connector(s) which are causing the condition. Note Fretting corrosion looks like little dark smudges on electrical terminals and appear where the actual electrical contact is being made. In less severe cases it may be unable to be seen or identified without the use of a magnifying glass. Important DO NOT apply an excessive amount of dielectric lubricant to the connectors as shown, as hydrolock may result when attempting to mate the connectors. Use ONLY a clean nylon brush that is dedicated to the repair of the conditions in this bulletin. 3. With a one-inch nylon bristle brush, apply dielectric lubricant to both the module/component side and the harness side of the affected connector(s). 4. Reconnect the affected connector(s) and wipe away any excess lubricant that may be present. 5. Attempt to duplicate the condition by using the following information: - DTC Diagnostic Procedure - Circuit/System Description - Conditions for Running the DTC - Conditions for Setting the DTC - Diagnostic Aids - Circuit/System Verification ‹› If the condition cannot be duplicated, the repair is complete. ‹› If the condition can be duplicated, then follow the appropriate DTC, Symptom or Circuit/System Testing procedure (refer to SI). Repair Order Documentation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > Customer Interest: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 9675 Important The following information MUST be documented on the repair order. Failure to do so may result in a chargeback. - Customer vehicle condition. - Was a Service Lamp or Service Message illuminated? If yes, specify which Service Lamp or Service Message. - Was a DTC(s) set? If yes, specify which DTC(s) were set. - After following the procedure contained within this bulletin, could the condition be duplicated? ‹› If the condition was not duplicated, then document the affected module/component connector name and number on the repair order. - If the condition was duplicated after the procedure contained within this bulletin was followed, and additional diagnosis led to the replacement of a module or component, the SI Document ID Number MUST be written on the repair order. Parts Information Alternate Distributor For All of North America Note NyoGel(R) 760G Lubricant* is equivalent to GMSPO P/N 12377900, and P/N 10953529 (Canada), specified for use to correct the condition in this bulletin. *We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for, or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > Customer Interest: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 9676 For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to refer to the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules Wiring Harness: All Technical Service Bulletins Electrical - MIL ON/DTC's Set By Various Control Modules TECHNICAL Bulletin No.: 09-06-03-004D Date: December 08, 2010 Subject: Intermittent No Crank/No Start, No Module Communication, MIL, Warning Lights, Vehicle Messages or DTCs Set by Various Control Modules - Diagnosing and Repairing Fretting Corrosion (Disconnect Affected Connector and Apply Dielectric Lubricant) Models: 2011 and Prior GM Passenger Cars and Trucks Attention: This repair can be applied to ANY electrical connection including, but not limited to: lighting, body electrical, in-line connections, powertrain control sensors, etc. DO NOT over apply lubricant to the point where it prevents the full engagement of sealed connectors. A light coating on the terminal surfaces is sufficient to correct the condition. Supercede: This bulletin is being revised to update the Attention statement and add the 2011 model year. Please discard Corporate Bulletin Number 09-06-03-004C (Section 06 Engine/Propulsion System). Condition Some customers may comment on any of the following conditions: - An intermittent no crank/no start - Intermittent malfunction indicator lamp (MIL) illumination - Intermittent service lamp illumination - Intermittent service message(s) being displayed The technician may determine that he is unable to duplicate the intermittent condition. Cause This condition may be caused by a buildup of nonconductive insulating oxidized debris known as fretting corrosion, occurring between two electrical contact surfaces of the connection or connector. This may be caused by any of the following conditions: - Vibration - Thermal cycling - Poor connection/terminal retention - Micro motion - A connector, component or wiring harness not properly secured resulting in movement On low current signal circuits this condition may cause high resistance, resulting in intermittent connections. On high current power circuits this condition may cause permanent increases in the resistance and may cause a device to become inoperative. Representative List of Control Modules and Components The following is only a representative list of control modules and components that may be affected by this connection or connector condition and DOES NOT include every possible module or component for every vehicle. - Blower Control Module - Body Control Module (BCM) - Communication Interface Module (CIM) - Cooling Fan Control Module - Electronic Brake Control Module (EBCM) - Electronic Brake and Traction Control Module (EBTCM) - Electronic Suspension Control (ESC) Module - Engine Control Module (ECM) - Heating, Ventilation and Air Conditioning (HVAC) Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 9682 - HVAC Actuator - Inflatable Restraint Sensing and Diagnostic Module (SDM) - Any AIR BAG module - Seatbelt Lap Anchor Pretensioner - Seatbelt Retractor Pretensioner - An SIR system connection or connector condition resulting in the following DTCs being set: B0015, B0016, B0019, B0020, B0022, or B0023 - Powertrain Control Module (PCM) - Remote Control Door Lock Receiver (RCDLR) - Transmission Control Module (TCM) Correction Important DO NOT replace the control module, wiring or component for the following conditions: - The condition is intermittent and cannot be duplicated. - The condition is present and by disconnecting and reconnecting the connector the condition can no longer be duplicated. Use the following procedure to correct the conditions listed above. 1. Install a scan tool and perform the Diagnostic System Check - Vehicle. Retrieve and record any existing history or current DTCs from all of the control modules (refer to SI). ‹› If any DTC(s) are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). ‹› If DTCs are not set, refer to Symptoms - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). 2. When identified, use the appropriate DTC Diagnostics, Symptoms, Schematics, Component Connector End Views and Component Locator documents to locate and disconnect the affected harness connector(s) which are causing the condition. Note Fretting corrosion looks like little dark smudges on electrical terminals and appear where the actual electrical contact is being made. In less severe cases it may be unable to be seen or identified without the use of a magnifying glass. Important DO NOT apply an excessive amount of dielectric lubricant to the connectors as shown, as hydrolock may result when attempting to mate the connectors. Use ONLY a clean nylon brush that is dedicated to the repair of the conditions in this bulletin. 3. With a one-inch nylon bristle brush, apply dielectric lubricant to both the module/component side and the harness side of the affected connector(s). 4. Reconnect the affected connector(s) and wipe away any excess lubricant that may be present. 5. Attempt to duplicate the condition by using the following information: - DTC Diagnostic Procedure - Circuit/System Description - Conditions for Running the DTC - Conditions for Setting the DTC - Diagnostic Aids - Circuit/System Verification ‹› If the condition cannot be duplicated, the repair is complete. ‹› If the condition can be duplicated, then follow the appropriate DTC, Symptom or Circuit/System Testing procedure (refer to SI). Repair Order Documentation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 9683 Important The following information MUST be documented on the repair order. Failure to do so may result in a chargeback. - Customer vehicle condition. - Was a Service Lamp or Service Message illuminated? If yes, specify which Service Lamp or Service Message. - Was a DTC(s) set? If yes, specify which DTC(s) were set. - After following the procedure contained within this bulletin, could the condition be duplicated? ‹› If the condition was not duplicated, then document the affected module/component connector name and number on the repair order. - If the condition was duplicated after the procedure contained within this bulletin was followed, and additional diagnosis led to the replacement of a module or component, the SI Document ID Number MUST be written on the repair order. Parts Information Alternate Distributor For All of North America Note NyoGel(R) 760G Lubricant* is equivalent to GMSPO P/N 12377900, and P/N 10953529 (Canada), specified for use to correct the condition in this bulletin. *We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for, or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 9684 For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to refer to the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair Wiring Harness: All Technical Service Bulletins Electrical - Information For Electrical Ground Repair INFORMATION Bulletin No.: 10-08-45-001B Date: October 25, 2010 Subject: Information for Electrical Ground Repair - Use New Replacement Fasteners with Conductive Finish Models: 2011 and Prior GM Passenger Cars and Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add the 2011 model year and update the Warranty Information. Please discard Corporate Bulletin Number 10-08-45-001A (Section 08 - Body and Accessories). Electrical Ground Repair Overview Proper electrical system function relies on secure, stable and corrosion-free electrical ground connections. Loose, stripped, or corroded connections increase the possibility of improper system function and loss of module communication. These conditions may also lead to unnecessary repairs and component replacement. In general, electrical ground connections are accomplished using one, or a combination of the following attachment methods: - Welded M6 stud and nut - Welded M6 nut and bolt - Welded M8 nut and bolt Determine which attachment method is used and perform the appropriate or alternative repair as described in this bulletin. M6 Weld Stud Replacement Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. Select a location adjacent the damaged or missing M6 ground stud having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the M6 conductive rivet stud flange. 2. Using GM approved residue-free solvent or equivalent, remove any grease from the repair site and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 3. Drill a 10 mm (0.40 in) diameter hole through the panel. 4. Remove paint and primer from the area surrounding the 10 mm (0.40 in) hole until bare metal is visible. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9689 Important The M6 conductive rivet stud as shown, can accommodate a panel thickness range of 0.7-4.2 mm (0.03-0.17 in). If there are layers of sheet metal, they should be touching without any air gaps to ensure a good ground. 5. Select a M6 conductive rivet stud. Refer to the Parts Information section of this bulletin. Note Use the GE-50317 rivet stud tool kit. 6. Place the M6 conductive rivet stud (1) in the 10 mm (0.40 in) hole. Assemble the rivet stud tool (2) with the groove and flare side facing the rivet stud, then the washer and the M6 nut (3). 7. Using a wrench on the rivet stud tool, and a socket on the M6 nut, secure the M6 conductive rivet stud. 8. Ensure the rivet stud is securely fastened, WITHOUT ANY detectable movement. 9. Completely wrap the threads of the rivet stud with painters tape or equivalent. Note The rivet stud and surrounding panel area MUST BE properly refinished PRIOR to the installation of the ground wire terminal and conductive nut to maintain a secure, stable and corrosion-free electrical ground. 10. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 11. Allow the refinished repair area to cure sufficiently before removing the protective material applied to the rivet stud threads. 12. Remove the painters tape or equivalent from the rivet stud threads. 13. Using GM approved residue-free solvent or equivalent, thoroughly clean the rivet stud threads to remove any adhesive and allow to dry. 14. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive rivet stud. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9690 15. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 16. Install the electrical ground wire terminal to the rivet stud. 17. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 18. Install the M6 conductive nut to the rivet stud and: Tighten Tighten to 8 Nm (71 lb in). 19. Verify proper system operation. M6 Weld Nut Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M6 weld nut at the electrical ground location is damaged or stripped, a M7 conductive self-threading bolt may be used to secure the ground wire terminal. 2. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the weld nut and allow to dry. 3. Remove any loose metal particles from the damaged or stripped weld nut with a stiff brush. 4. Select a M7 conductive self-threading bolt. Refer to the Parts Information section of this bulletin 5. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M7 conductive self-threading bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 6. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 7. Install the electrical ground wire terminal to the M7 conductive self-threading bolt. 8. Install the M7 conductive self-threading bolt and: Tighten Tighten to 9 Nm (80 lb in). 9. Verify proper system operation. M6 Weld Nut Alternative Repair Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the electrical ground location is accessible from both sides of the panel, a M6 conductive bolt and a M6 conductive nut may be used to secure the electrical ground wire terminal. Refer to the Parts Information section of this bulletin. 2. Select a location adjacent the damaged M6 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the new electrical ground site. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the ground location and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 8.5 mm (0.33 in) diameter hole through the panel. 5. Remove paint and primer from the area surrounding the 8.5 mm (0.33 in) hole until bare metal is visible. 6. Select a M6 conductive bolt. Refer to the Parts Information section of this bulletin. 7. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 8. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 9. Install the electrical ground wire terminal and the M6 conductive bolt to the ground location. 10. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 11. Install the M6 conductive nut to the bolt and: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9691 Tighten Tighten to 8 Nm (71 lb in). Note The repair area MUST BE properly refinished to maintain a secure, stable and corrosion-free electrical ground. 12. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 13. Verify proper system operation. M8 Weld Nut Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M8 weld nut electrical ground location is accessible from both sides of the panel, a M8 conductive bolt and a M8 conductive nut may be used to secure the electrical ground wire terminal. Refer to the Parts Information section of this bulletin. 2. Select a location adjacent the M8 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the new electrical ground site. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the surface surrounding the ground location and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 10 mm (0.40 in) diameter hole through the panel. 5. Remove paint and primer from the area surrounding the 10 mm (0.40 in) hole until bare metal is visible. 6. Select a M8 conductive bolt. Refer to the Parts Information section of this bulletin. 7. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M8 conductive bolt. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 8. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 9. Install the electrical ground wire terminal and the M8 conductive bolt to the ground location. 10. Select a M8 conductive nut. Refer to the Parts Information section of this bulletin. 11. Install the M8 conductive nut to the bolt and: Tighten Tighten to 22 Nm (16 lb ft). Note The repair area MUST BE properly refinished to maintain a secure, stable and corrosion-free electrical ground. 12. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 13. Verify proper system operation. M8 Weld Nut Alternative Repair Caution Use only the GM-approved replacement fasteners with conductive finish for electrical ground repair. 1. If the M8 weld nut electrical ground location is not accessible from both sides of the panel, a M6 conductive rivet stud and a M6 conductive nut may be used to secure the electrical ground wire terminal. 2. Select a location adjacent the damaged M8 weld nut having 20 mm (0.79 in) clearance behind the panel surface and 20 mm (0.79 in) clearance surrounding the M6 conductive rivet stud flange. 3. Using GM approved residue-free solvent or equivalent, remove any grease from the repair site and allow to dry. Note Ensure 20 mm (0.79 in) clearance is maintained behind the panel to be drilled. 4. Drill a 10 mm (0.40 in) diameter hole through the panel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9692 5. Remove paint and primer from the area surrounding the 10 mm (0.40 in) until bare metal is visible. Important The M6 conductive rivet stud as shown, can accommodate a panel thickness range of 0.7-4.2 mm (0.03-0.17 in). If there are layers of sheet metal, they should be touching without any air gaps to ensure a good ground. 6. Select a M6 conductive rivet stud. Refer to the Parts Information section of this bulletin. Note Use the GE-50317 rivet stud tool kit. 7. Place the M6 conductive rivet stud (1) in the 10 mm (0.40 in) hole. Assemble the rivet stud tool (2) with the groove and flare side facing the rivet stud, then the washer and the M6 nut (3). 8. Using a wrench on the rivet stud tool, and a socket on the M6 nut, secure the M6 conductive rivet stud. 9. Ensure the new rivet stud is securely fastened, WITHOUT ANY detectable movement. 10. Completely wrap the threads of the rivet stud with painters tape or equivalent. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9693 Note The rivet stud and surrounding panel area MUST BE properly refinished PRIOR to the installation of the electrical ground wire terminal and conductive nut to maintain a secure, stable and corrosion-free electrical ground. 11. Refinish the repair area using an anti-corrosion primer. Refer to Anti-Corrosion Treatment and Repair in SI. 12. Allow the refinished repair area to cure sufficiently before removing the protective material applied to the rivet stud threads. 13. Remove the painters tape or equivalent from the rivet stud threads. 14. Using GM approved residue-free solvent or equivalent, thoroughly clean the rivet stud threads to remove any adhesive and allow to dry. 15. Using a small brush, apply Dielectric Lubricant GM P/N 12377900 (Canadian P/N 10953529) to the threads of the M6 conductive rivet stud. Note Fretting corrosion is a build-up of insulating, oxidized wear debris that can form when there is a small motion between electrical contacts. The oxidized wear debris can accumulate at the electrical contact points causing the electrical resistance across the connection to increase. 16. Carefully remove ANY corrosion or contamination that may be present on the electrical ground wire terminal. 17. Install the electrical ground wire terminal to the M6 conductive rivet stud. 18. Select a M6 conductive nut. Refer to the Parts Information section of this bulletin. 19. Install the M6 conductive nut to the rivet stud and: Tighten Tighten to 8 Nm (71 lb in) 20. Verify proper system operation. Parts Information Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 10-08-45-001B > Oct > 10 > Electrical - Information For Electrical Ground Repair > Page 9694 For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 06-08-45-004 > May > 06 > Electrical - Instrument Panel & General Wiring Repair Wiring Harness: All Technical Service Bulletins Electrical - Instrument Panel & General Wiring Repair Bulletin No.: 06-08-45-004 Date: May 02, 2006 INFORMATION Subject: Instrument Panel (I/P), Body and General Wiring Harness Repair Models: 2007 and Prior GM Cars and Trucks 2003-2007 HUMMER H2 2006-2007 HUMMER H3 Important: A part restriction has been implemented on all Body and I/P harnesses and is being administered by the PQC. If a body or I/P harness replacement is required, it can take 12-28 weeks for a harness to be built and delivered to a dealer. The dealer technician is expected to repair any harness damage as the first and best choice before replacing a harness. In an effort to standardize repair practices, General Motors is requiring that all wiring harnesses be repaired instead of replaced. If there is a question concerning which connector and/or terminal you are working on, refer to the information in the appropriate Connector End Views in SI. The Instruction Manual J 38125-620, which is sent with each new update of the J 38125 Terminal Repair Kit, also has terminal crimping and terminal remove information. Important: There are some parts in the J 38125 Terminal Repair Kit (i.e. SIR connector CPAs and heat shrink tube (used in high heat area pigtail replacement) and some TPAs that are not available from GMSPO. It is vitally important that each update to the J 38125 Terminal Repair Kit be done as soon as it arrives at the dealer. Utilize the Terminal Repair Kit (J 38125) to achieve an effective wiring repair. The Terminal Repair Kit has been an essential tool for all GM Dealers since 1987. Replacement terminals and tools for this kit are available through SPX/Kent Moore. Refer to Corporate Bulletin Number 06-08-45-001 for more information. The Instruction Manual J 38125-620, which is sent with each new update to the J 38125 Terminal Repair Kit, also has terminal crimping and terminal removal information. U.S. Dealers Only - Training courses (including Tech Assists, Emerging Issues, Web, IDL and Hands-on) are available through the GM Training website. Refer to Resources and then Training Materials for a complete list of available courses. Canadian Dealers Only - Refer to the Training section of GM infoNet for a complete list of available courses and a copy of the J 38125 Terminal Repair Kit Instruction Manual. Wiring repair information is also available in Service Information (SI). The Wiring Repair section contains information for the following types of wiring repairs: - Testing for intermittent conditions and poor conditions - Flat wire repairs - GMLAN wiring repairs - High temperature wiring repairs - Splicing copper wire using splice clips - Splicing copper wire using splice sleeves - Splicing twisted or shielded cable - Splicing inline harness diodes Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 06-08-45-004 > May > 06 > Electrical - Instrument Panel & General Wiring Repair > Page 9699 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Power and Ground Distribution > Wiring Harness > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wiring Harness: > 676201 > Apr > 96 > Engine - Extreme Temperature Gauge Fluctuation Temperature Gauge: All Technical Service Bulletins Engine - Extreme Temperature Gauge Fluctuation File In Section: 6 - Engine Bulletin No.: 67-62-01 Date: April, 1996 Subject: Extreme Engine Temperature Gauge Fluctuation (Install a New Thermostat) Models: 1996 Chevrolet and GMC C/K, G Models with 4.3L, 5.0L, 5.7L Engines (VINs M, R, X, W RPOs L30, L31, LF6, L35) Condition Some owners may experience extreme engine temperature gauge fluctuation. Cause Thermostat was not optimally positioned to sense true engine coolant temperature. Correction Install a new thermostat which increases coolant flow past the thermostat temperature sensing element. Parts Information Refer to the following part number when replacing the thermostat: Part Number Description 12557859 Thermostat Parts are expected to be available on April 8, 1996 from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J3500 Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Alignment > System Information > Technical Service Bulletins > Steering/Suspension - Wheel Alignment Specifications Alignment: Technical Service Bulletins Steering/Suspension - Wheel Alignment Specifications WARRANTY ADMINISTRATION Bulletin No.: 05-03-07-009C Date: December 09, 2010 Subject: Wheel Alignment Specifications, Requirements and Recommendations for GM Vehicles Models: 2011 and Prior GM Passenger Cars and Light Duty Trucks Supercede: This bulletin is being extensively revised to provide technicians and warranty administrators with an all inclusive guide for wheel alignments. PLEASE FAMILIARIZE YOURSELF WITH THESE UPDATES BEFORE PERFORMING YOUR NEXT GM WHEEL ALIGNMENT SERVICE. Please discard Corporate Bulletin Number 05-03-07-009B (Section 03 - Suspension). Purpose The purpose of this bulletin is to provide retail, wholesale and fleet personnel with General Motors' warranty service requirements and recommendations for customer concerns related to wheel alignment. For your convenience, this bulletin updates and centralizes all of GM's Standard Wheel Alignment Service Procedures, Policy Guidelines and bulletins on wheel alignment warranty service. Important PLEASE FAMILIARIZE YOURSELF WITH THESE UPDATES BEFORE PERFORMING YOUR NEXT GM WHEEL ALIGNMENT SERVICE. The following five (5) key steps are a summary of this bulletin and are REQUIRED in completing a successful wheel alignment service. 1. Verify the vehicle is in an Original Equipment condition for curb weight, tires, wheels, suspension and steering configurations. Vehicles modified in any of these areas are not covered for wheel alignment warranty. 2. Review the customer concern relative to "Normal Operation" definitions. 3. Verify that vehicle is within the "Mileage Policy" range. 4. Document wheel alignment warranty claims appropriately for labor operations E2000 and E2020. The following information must be documented or attached to the repair order: - Customer concern in detail - What corrected the customer concern? - If a wheel alignment is performed: - Consult SI for proper specifications. - Document the "Before" AND "After" wheel alignment measurements/settings. - Completed "Wheel Alignment Repair Order Questionnaire" (form attached to this bulletin) 5. Use the proper wheel alignment equipment (preferred with print-out capability), process and the appropriate calibration maintenance schedules. Important If it is determined that a wheel alignment is necessary under warranty, use the proper labor code for the repair. E2000 for Steering Wheel Angle and/or Front Toe set or E2020 for Wheel Alignment Check/Adjust includes Caster, Camber and Toe set (Wheel alignment labor time for other component repairs is to be charged to the component that causes a wheel alignment operation.). The following flowchart is to help summarize the information detailed in this bulletin and should be used whenever a wheel alignment is performed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Alignment > System Information > Technical Service Bulletins > Steering/Suspension - Wheel Alignment Specifications > Page 9715 Verify Original Equipment Condition of the Vehicle - Verify that Original Equipment Tires and Wheels or Official GM Accessory Tires and Wheels are on the vehicle. - Verify that aftermarket suspension "Lift" or "Lowering" Kits or other suspension alterations have NOT been done to the vehicle. - Check for accidental damage to the vehicle; for example, severe pothole or curb impacts, collision damage that may have affected the wheel alignment of the vehicle; e.g., engine cradles, suspension control arms, axles, wheels, wheel covers, tires may show evidence of damage/impact. - Check to be sure vehicle has seen "Normal Use" rather than abuse; e.g., very aggressive driving may show up by looking at the tires and condition of the vehicle. - Check for other additional equipment items that may significantly affect vehicle mass such as large tool boxes, campers, snow plow packages (without the snowplow RPO), etc., especially in trucks and cutaway/incomplete vehicles. Significant additional mass can affect trim height and wheel alignment of the vehicle and may necessitate a customer pay wheel alignment when placed semi-permanently in the vehicle (Upfitter instructions are to realign the vehicle after placement of these types of items. (This typically applies to trucks and incomplete vehicles that can be upfit with equipment such as the above.) Customer Concerns, "Normal Operation" Conditions and "Mileage Policy" Possible Concerns The following are typical conditions that may require wheel alignment warranty service: 1. Lead/Pull: defined as "at a constant highway speed on a typical straight road, the amount of effort required at the steering wheel to maintain the vehicle's straight heading." Important Please evaluate for the condition with hands-on the steering wheel. Follow the "Vehicle Leads/Pulls" diagnostic tree located in SI to determine the cause of a lead/pull concern. Lead/Pull concerns can be due to road crown or road slope, tires, wheel alignment or even in rare circumstances a steering gear issue. Lead/pull concerns due to road crown are considered "Normal Operation" and are NOT a warrantable condition -- the customer should be advised that this is "Normal Operation." Important Some customers may comment on a "Lead/Pull" when they hold the steering wheel in a level condition. If so, this is more likely a "steering wheel angle" concern because the customer is "steering" the vehicle to obtain a "level" steering wheel. 2. Steering wheel angle to the left or right (counter-clockwise or clockwise, respectively): Defined as the steering wheel angle (clocking) deviation from "level" while maintaining a straight heading on a typical straight road. 3. Irregular or Premature tire wear: Slight to very slight "feathering" or "edge" wear on the shoulders of tires is NOT considered unusual and should even out with a tire rotation; if the customer is concerned about a "feathering" condition of the tires, the customer could be advised to rotate the tires earlier than the next scheduled mileage/maintenance interval (but no later than the next interval). Be sure to understand the customer's driving habits as this will also heavily influence the tire wear performance; tire wear from aggressive or abusive driving habits is NOT a warrantable condition. Important Slight or mild feathering, cupping, edge or heel/toe wear of tire tread shoulders is "normal" and can show up very early in a tire/vehicle service mileage; in fact, some new tires can show evidence of feathering from the factory. These issues do NOT affect the overall performance and tread life of the tire. Dealer personnel should always check the customer's maintenance records to ensure that tire inflation pressure is being maintained to placard and that the tires are being rotated (modified-X pattern) at the proper mileage intervals. Wheel alignments are NOT to be performed for the types of "Normal" Tire Feathering shown in Figures 1-4 below. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Alignment > System Information > Technical Service Bulletins > Steering/Suspension - Wheel Alignment Specifications > Page 9716 Figure 1: Full Tread View - "NORMAL" Tire "Feathering" Wear on the Shoulder/Adjacent/Center Ribs Figure 2: Tire Shoulder View Example 1 - "NORMAL" Tire "Feathering" Wear on the Shoulder Figure 3: Tire Shoulder View Example 2 - "NORMAL" Tire "Feathering" Wear Figure 4: Detail Side View of Tire Shoulder Area - "NORMAL" Tire "Feathering" Wear Important When a wheel alignment is deemed necessary for tire wear, be sure to document on the repair order, in as much detail as possible, the severity and type of tire wear (e.g., severe center wear or severe inside or outside shoulder wear) and the position of the tire on the vehicle (RF, LF, LR, RR). Please note the customer's concern with the wear such as, noise, appearance, wear life, etc. A field product report with pictures of the tire wear condition is recommended. Refer to Corporate Bulletin Number 02-00-89-002J and #07-00-89-036C. 4. Other repairs that affect wheel alignment; e.g., certain component replacement such as suspension control arm replacement, engine cradle adjustment/replace, steering gear replacement, steering tie rod replace, suspension strut/shock, steering knuckle, etc. may require a wheel alignment. Important If other components or repairs are identified as affecting the wheel alignment, policy calls for the wheel alignment labor time to be charged to the replaced/repaired component's labor operation time rather than the wheel alignment labor operations. Important Vibration type customer concerns are generally NOT due to wheel alignment except in the rare cases; e.g., extreme diagonal wear across the tread. In general, wheel alignments are NOT to be performed as an investigation/correction for vibration concerns. "Normal Operation" Conditions Vehicle Lead/Pull Due to Road Crown or Slope: As part of "Normal Operation," vehicles will follow side-to-side or left to right road crown or slope. Be sure to verify from the customer the types of roads they are driving as they may not recognize the influence of road crown on vehicle lead/pull and steering wheel angle. If a vehicle requires significant steering effort to prevent it from "climbing" the road crown there may be an issue to be looked into further. Important Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Alignment > System Information > Technical Service Bulletins > Steering/Suspension - Wheel Alignment Specifications > Page 9717 A wheel alignment will generally NOT correct vehicles that follow the road crown since this is within "Normal Operation." Mileage Policy The following mileage policy applies for E2020 and E2000 labor operations: Note Wheel Alignment is NOT covered under the New Vehicle Limited Warranty for Express and Savana Cutaway vehicles as these vehicles require Upfitters to set the wheel alignment after completing the vehicles. - 0-800 km (0-500 mi): E2000/E2020 claims ONLY allowed with Call Center Authorization. Due to the tie down during shipping, the vehicle's suspension requires some time to reach normal operating position. For this reason, new vehicles are generally NOT to be aligned until they have accumulated at least 800 km (500 mi). A field product report should accompany any claim within this mileage range. - 801-12,000 km (501-7,500 mi): - If a vehicle came from the factory with incorrect alignment settings, any resulting off-angle steering wheel, lead/pull characteristics or the rare occurrence of excessive tire wear would be apparent early in the life of the vehicle. The following policy applies: - Vehicles 100% Factory Set/Measured for Caster/Camber/Toe - Escalade/ESV/EXT, Tahoe/Suburban, Yukon/XL/Denali, Silverado/Sierra, Express/Savana, Corvette and Colorado/Canyon: E2000/E2020 Claims: Call Center Authorization Required - All Vehicles NOT 100% Factory Set/Measured for Caster/Camber/Toe as noted above: E2000/E2020 Claims: Dealer Service Manager Authorization Required - 12,001 km and beyond (7,501 miles and beyond): During this period, customers are responsible for the wheel alignment expense or dealers may provide on a case-by case basis a one-time customer enthusiasm claim up to 16,000 km (10,000 mi). In the event that a defective component required the use of the subject labor operations, the identified defective component labor operation will include the appropriate labor time for a wheel alignment as an add condition to the component repair. Important Only one wheel alignment labor operation claim (E2000 or E2020) may be used per VIN. Warranty Documentation Requirements When a wheel alignment service has been deemed necessary, the following items will need to be clearly documented on/with the repair order: - Customer concern in detail - What corrected the customer concern? - If a wheel alignment is performed: - Consult SI for proper specifications. - Document the "Before" AND "After" wheel alignment measurements/settings. - Completed "Wheel Alignment Repair Order Questionnaire" (form attached to this bulletin) 1. Document the customer concern in as much detail as possible on the repair order and in the warranty administration system. Preferred examples: - Steering wheel is off angle in the counterclockwise direction by approximately x degrees or clocking position. - Vehicle lead/pulls to the right at approximately x-y mph. Vehicle will climb the road crown. Severe, Moderate or Slight. - RF and LF tires are wearing on the outside shoulders with severe feathering. Important In the event of a lead/pull or steering wheel angle concern, please note the direction of lead/pull (left or right) or direction of steering wheel angle (clockwise or counterclockwise) on the repair order and within the warranty claim verbatim. Important In the event of a tire wear concern, please note the position on the vehicle and where the wear is occurring on the tire; i.e., the RF tire is wearing on the inside shoulder. 2. Document the technician's findings on cause and correction of the issue. Examples: - Reset LF toe from 0.45 degrees to 0.10 degrees and RF toe from -0.25 degrees to 0.10 degrees to correct the steering wheel angle from 5 degrees counterclockwise to 0 degrees. - Reset LF camber from 0.25 degrees to -0.05 degrees to correct the cross-camber condition of +0.30 degrees to 0.00 degrees on the vehicle. - Front Sum toe was found to be 0.50 degrees, reset to 0.20 degrees. 3. Print-out the "Before" and "After" wheel alignment measurements/settings and attach them to the Repair Order or if print-out capability is not Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Alignment > System Information > Technical Service Bulletins > Steering/Suspension - Wheel Alignment Specifications > Page 9718 available, measurements may also be clearly and legibly handwritten into the Wheel Alignment Repair Order Questionnaire attached to this bulletin. 4. Attach the Wheel Alignment Repair Order Questionnaire below along with the print-out of "Before" and "After" wheel alignment measurements to the Repair Order and retain for use by GM. Wheel Alignment Equipment and Process Wheel alignments must be performed with a quality machine that will give accurate results when performing checks. "External Reference" (image-based camera technology) is preferred. Please refer to Corporate Bulletin Number 05-00-89-029B: General Motors Dealership Critical Equipment Requirements and Recommendations. Requirements: - Computerized four wheel alignment system. - Computer capable of printing before and after alignment reports. - Computer capable of time and date stamp printout. - Racking system must have jacking capability - Racking system must be capable of level to 1.6 mm (1/16 in) - Appropriate wheel stops and safety certification - Built-in turn plates and slip plates - Wheel clamps capable of attaching to 20" or larger wheels - Racking capable of accepting any GM passenger car or light duty truck - Operator properly trained and ASE-certified (U.S. only) in wheel alignment Recommendations: Racking should have front and rear jacking capability. Equipment Maintenance and Calibration: Alignment machines must be regularly calibrated in order to give correct information. Most manufacturers recommend the following: - Alignment machines with "internal reference" sensors should be checked (and calibrated, if necessary) every six months. - Alignment machines with "external reference" (image-based camera technology) should be checked (and calibrated, if necessary) once a year. - Racks must be kept level to within 1.6 mm (1/16 in). - If any instrument that is part of the alignment machine is dropped or damaged in some way, check the calibration immediately. Check with the manufacturer of your specific equipment for their recommended service/calibration schedule. Wheel Alignment Process When performing wheel alignment measurement and/or adjustment, the following steps should be taken: Preliminary Steps: 1. Verify that the vehicle has a full tank of fuel (compensate as necessary). 2. Inspect the wheels and the tires for damage. 3. Inspect the tires for the proper inflation and irregular tire wear. 4. Inspect the wheel bearings for excessive play. 5. Inspect all suspension and steering parts for looseness, wear, or damage. 6. Inspect the steering wheel for excessive drag or poor return due to stiff or rusted linkage or suspension components. 7. Inspect the vehicle trim height. 8. Compensate for frame angle on targeted vehicles (refer to Wheel Alignment Specifications in SI). Satisfactory vehicle operation may occur over a wide range of alignment angles. However, if the wheel alignment angles are not within the range of specifications, adjust the wheel alignment to the specifications. Refer to Wheel Alignment Specifications in SI. Give consideration to excess loads, such as tool boxes, sample cases, etc. Follow the wheel alignment equipment manufacturer's instructions. Measure/Adjust: Important Prior to making any adjustments to wheel alignment on a vehicle, technicians must verify that the wheel alignment specifications loaded into their wheel alignment machine are up-to-date by comparing these to the wheel alignment specifications for the appropriate model and model year in SI. Using incorrect and/or outdated specifications may result in unnecessary adjustments, irregular and/or premature tire wear and repeat customer concerns Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Alignment > System Information > Technical Service Bulletins > Steering/Suspension - Wheel Alignment Specifications > Page 9719 Important When performing adjustments to vehicles requiring a 4-wheel alignment, set the rear wheel alignment angles first in order to obtain proper front wheel alignment angles. Perform the following steps in order to measure the front and rear alignment angles: 1. Install the alignment equipment according to the manufacturer's instructions. 2. Jounce the front and the rear bumpers 3 times prior to checking the wheel alignment. 3. Measure the alignment angles and record the readings. If necessary, adjust the wheel alignment to vehicle specification and record the before and after measurements. Refer to Wheel Alignment Specifications in SI. Important Technicians must refer to SI for the correct wheel alignment specifications. SI is the only source of GM wheel alignment specifications that is kept up-to-date throughout the year. Test drive vehicle to ensure proper repair. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Alignment > System Information > Technical Service Bulletins > Steering/Suspension - Wheel Alignment Specifications > Page 9720 Frame Angle Measurement (Express / Savana Only) ........ Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Alignment > System Information > Technical Service Bulletins > Steering/Suspension - Wheel Alignment Specifications > Page 9721 What corrected the customer concern and was the repair verified? Please Explain: ............. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Alignment > System Information > Specifications > Vehicle Ride (Trim) Height Specifications Alignment: Specifications Vehicle Ride (Trim) Height Specifications Vehicle Ride Height Location & Specifications "Z" HEIGHT 1. Lift front bumper of vehicle up approximately 1.5 inches. 2. Gently remove hands and allow vehicle to settle on its own. 3. Repeat this operation twice more for a total of three times. 4. Measure "Z" height, Fig. 1. 5. Push front bumper on vehicle down approximately 1.5 inches. 6. Gently remove hands and allow vehicle to rise on its own. 7. Repeat this operation twice more for a total of three times. 8. Measure "Z" height. 9. Find the average of the high and low measurements. This is the "Z" height. "Z" height should be 3.74 inches. "D" HEIGHT Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Alignment > System Information > Specifications > Vehicle Ride (Trim) Height Specifications > Page 9724 Use the same procedure used in determining the "Z" height. "D" height should be 7.17 inches. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Alignment > System Information > Specifications > Vehicle Ride (Trim) Height Specifications > Page 9725 Alignment: Specifications Alignment Specifications Caster, Degrees Checking [01] ....................................................................................................................................... ......................................................... 3.75 +/- 2.0 Setting [02] ............................................................. ....................................................................................................................................... 3.75 +/- 1.0 Camber, Degrees Checking [01] ....................................................................................................................................... ........................................................... 0.5 +/- 1.0 Setting [02] ............................................................. ......................................................................................................................................... 0.5 +/- 0.5 Toe-In, Degrees Checking [03] ....................................................................................................................................... ......................................................... 0.24 +/- 0.2 Setting [03] ............................................................. ..................................................................................................................................................... 0.24 Ball Joint Wear, inches [04] ................................................................................................................. ........................................................................... 0.08 Note: Caster angle must be corrected to level frame angle. [01] Left and right side should be equal within +1.0 deg. [02] Left and right side should equal within +0.5 deg. [03] Toe-in left and right side to be set equally per wheel and steering wheel must be held in straight ahead position within +/-5.0 deg. [04] Refer to /Steering & Suspension/ Ball Joint Inspection for inspection procedure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Alignment > System Information > Service and Repair > Front Wheel Alignment Alignment: Service and Repair Front Wheel Alignment Front Caster and Camber Adjustment Vehicle Ride Height Location & Specifications Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Alignment > System Information > Service and Repair > Front Wheel Alignment > Page 9728 Caster Measures CAMBER 1. Determine the camber from the alignment equipment. 2. Install adjustment kit No. 15538596, or equivalent. 3. Reset camber to specifications. CASTER All caster specifications are given with the vehicle frame level (zero angle). 1. Position vehicle on a smooth level surface. 2. If necessary, correct "Z" height. 3. Using a bubble protractor or inclinometer, measure frame angle, Figs. 1 and 2. 4. Note frame angle as being up in the rear or down in the rear. 5. Determine caster angle from alignment equipment. 6. Determine actual (corrected) caster reading, Fig. 2. 7. When measuring caster, note the following: a. A decrease in rear frame angle must be subtracted from a positive caster reading. b. An increase in rear frame angle must be added to a positive caster reading. c. A decrease in rear frame angle must be added to a negative caster reading. d. An increase in rear frame angle must be subtracted from a negative caster reading. 8. If the caster angle is incorrect, correct the caster angle by turning the adjustment cam bolts. Front Toe Adjustment 1. Determine toe-in from the alignment equipment. 2. Change length of both tie rod sleeves to effect a toe change. 3. Toe-in can be increased or decreased by changing the length of the tie rod ends. A threaded sleeve is provided for this purpose. When the tie rod ends are mounted ahead of the steering knuckle they must be decreased in length in order to increase toe-in. When the tie rod ends are mounted behind the steering knuckle they must be lengthened in order to increase toe-in. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Alignment > System Information > Service and Repair > Front Wheel Alignment > Page 9729 Alignment: Service and Repair Camber & Caster Adjustment Kit Installation Fig. 3 Upper Control Arm Removal Fig. 4 Alignment Service Kit 15538596 Installation As originally installed, the upper control arm cannot be adjusted for camber or caster. However, if the camber or caster is measured and found to be out of specification, the camber and caster can be set to proper specifications using adjustment kit 15538596, or equivalent. To install, proceed as follows: 1. Raise and support vehicle and lower control arms, then remove nut (60), washer (61) and bolt (62) from upper control arm bracket (44). Discard nut, washer and bolt. 2. Remove large washers (40), Figs. 3 and 4, which are welded to the upper control arm frame brackets. 3. Remove weld beads from the upper control arm bracket. Grind area smooth. 4. Install adjusting cams (49) to bracket (44). 5. Install bolt (48) and nut (50). 6. Adjust camber and caster to specifications by rotating bolt head. Tighten nuts to specification. See Steering and Suspension/Tires, Wheels and Alignment/Specifications/Mechanical. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Front Steering Knuckle > Component Information > Specifications Front Steering Knuckle: Specifications Lower Ball Joints to Steering Knuckle Nut ............................................................................................................................................. 128 Nm (94 ft. lb.) Upper Ball Joints to Steering Knuckle Nut ............................................................................................................................................. 100 Nm (74 ft. lb.) Splash Shield to Steering Knuckle Bolts ................................................................................................................................................... 26 Nm (19 ft. lb.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Pitman Arm > Component Information > Service and Repair Pitman Arm: Service and Repair IMPORTANT: Use the proper tool to separate all ball joints. REMOVE OR DISCONNECT TOOLS REQUIRED: ^ J 24319-01 Steering Linkage Puller. ^ J 29107 Pitman Arm Puller. ^ J 6632-01 Pitman Arm Remover. ^ Raise the vehicle. Support the vehicle with jack stands. 1. Relay rod nut (11) from the pitman arm ball stud (5). Do not reuse the nut. 2. Relay rod (14) from the pitman arm ball stud (5) using J 24319-01. 3. Pitman arm nut and washer. ^ Mark the pitman arm and the pitman shaft. This will permit proper alignment at assembly. NOTICE: Do not hammer on pitman arm, pitman shaft, or puller. Damage to pitman arm or steering gear may result. 4. Pitman arm. Use J 6632-01 or J 29107. INSPECT ^ Ball stud threads for damage. ^ Ball stud seals for excessive wear. CLEAN ^ Threads on the ball stud. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Pitman Arm > Component Information > Service and Repair > Page 9737 INSTALL OR CONNECT TOOLS REQUIRED: ^ J 29193 Steering Linkage Installer (12 mm). 1. Pitman arm on the pitman shaft. Line up the marks made at removal. 2. Pitman arm washer and nut. TIGHTEN ^ Pitman arm nut to 250 Nm (184 lbs. ft.). 3. Relay rod (14) to the pitman arm ball stud (5). Make sure the seal is on the stud. ^ Tighten J 29193 or J 29194 to 62 Nm (48 lbs. ft.) to seat the tapers. Remove the tool. 4. New relay rod prevailing torque nut (11) to the pitman arm ball stud (5). TIGHTEN ^ Nut (11) to 54 Nm (40 ft.lbs.). 5. Lower the vehicle. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Bleeding > System Information > Service and Repair Power Steering Bleeding: Service and Repair Fig. 2 Power Steering System Bleed Chart 1. Fill pump fluid reservoir to proper level and let fluid settle for at least two minutes. 2. Start and run engine for a few seconds. Do not turn steering wheel. 3. Turn engine OFF. Check fluid level, add fluid if necessary. 4. Repeat above procedure until fluid level remains constant after running engine. 5. Raise front end of vehicle so wheels are off ground. 6. Start engine. Slowly turn steering wheel in both directions, lightly contacting wheel stops. 7. Add power steering fluid, if necessary. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Bleeding > System Information > Service and Repair > Page 9742 8. Lower vehicle and turn steering wheel slowly from lock to lock. 9. Stop engine. Check fluid level and refill as required. 10. If fluid is extremely foamy, allow vehicle to stand a few minutes and repeat above procedure. For additional bleed procedures, refer to Fig. 2. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Pump > Component Information > Technical Service Bulletins > Customer Interest for Power Steering Pump: > 77-60-02 > Jun > 98 > Engine - Drive Belt Noise, P/S Pump Pulley Misaligned Power Steering Pump: Customer Interest Engine - Drive Belt Noise, P/S Pump Pulley Misaligned File In Section: 6 - Engine Bulletin No.: 77-60-02 Date: June, 1998 Subject: Accessory Drive Belt Noise Due to Power Steering Pump Pulley Misalignment (Properly Align Pulley) Models: 1996-98 Chevrolet and GMC C/K, M/L, S/T; G, P Models 1996-98 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, X, M, R, J, N - RPOs L35, LF6, L3O, L31, L29, L19) Condition Some owners may comment on accessory drive noise. Cause The power steering pump pulley may be misaligned with the end of the pump shaft. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Pump > Component Information > Technical Service Bulletins > Customer Interest for Power Steering Pump: > 77-60-02 > Jun > 98 > Engine - Drive Belt Noise, P/S Pump Pulley Misaligned > Page 9751 In addition to the normal service for the above condition, it is critical that the pulley is flush with the end of the power steering pump shaft. If it is not, reference the appropriate service manual for proper service instructions. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time E836O Use published labor operation time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Pump > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Power Steering Pump: > 77-60-02 > Jun > 98 > Engine - Drive Belt Noise, P/S Pump Pulley Misaligned Power Steering Pump: All Technical Service Bulletins Engine - Drive Belt Noise, P/S Pump Pulley Misaligned File In Section: 6 - Engine Bulletin No.: 77-60-02 Date: June, 1998 Subject: Accessory Drive Belt Noise Due to Power Steering Pump Pulley Misalignment (Properly Align Pulley) Models: 1996-98 Chevrolet and GMC C/K, M/L, S/T; G, P Models 1996-98 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L and 7.4L Engine (VINs W, X, M, R, J, N - RPOs L35, LF6, L3O, L31, L29, L19) Condition Some owners may comment on accessory drive noise. Cause The power steering pump pulley may be misaligned with the end of the pump shaft. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Pump > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Power Steering Pump: > 77-60-02 > Jun > 98 > Engine - Drive Belt Noise, P/S Pump Pulley Misaligned > Page 9757 In addition to the normal service for the above condition, it is critical that the pulley is flush with the end of the power steering pump shaft. If it is not, reference the appropriate service manual for proper service instructions. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time E836O Use published labor operation time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Pump > Component Information > Specifications > Mechanical Specifications Power Steering Pump: Mechanical Specifications Component .......................................................................................................................................... ..................................................................... Ft. Lbs. Adjuster Jam Nuts ............................................................................................................................... ............................................................................... 32 Coupling Clamp Bolt ....................................... .............................................................................................................................................................. .... 22 Gear To Frame Bolts ................................................................................................................. ....................................................................................... 100 Pitman Shaft Nut .................................. .............................................................................................................................................................. .............. 180 Pressure Line Fitting (At Gear) ...................................................................................... .................................................................................................... 20 Pressure Line Fitting (At Pump) .............................................................................................................................................................. ........................... 20 Pump Mounting Bolts ......................................................................................... ............................................................................................................... 37 Side Cover Bolts ............. .............................................................................................................................................................. ..................................... 48 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Pump > Component Information > Specifications > Mechanical Specifications > Page 9760 Power Steering Pump: Pressure, Vacuum and Temperature Specifications Pump Model ........................................................................................................................................ ........................................................................ C3HD Relief Valve Settings, psi Minimum [01]........................................................................................................................................ ..................................................................... 1465 Maximum [02]........................................................ .................................................................................................................................................... 1515 Pump Model ........................................................................................................................................ ............................................................................ [03] Relief Valve Settings, psi Minimum [01]........................................................................................................................................ ..................................................................... 1350 Maximum [02]........................................................ .................................................................................................................................................... 1450 [01] Output of power steering fluid at 90 deg.F when operating pump at 465 RPM against 665-735 psi. [02] Output of power steering fluid at 90 deg.F when operating pump at 1500 RPM against 50 psi. [03] All models except C3HD. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Pump > Component Information > Specifications > Page 9761 Power Steering Pump: Application and ID This vehicle uses a Vane type power steering pump w/ integral reservoir. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Pump > Component Information > Specifications > Page 9762 Power Steering Pump: Description and Operation Fig. 2 Exploded view of power steering pump The hydraulic pump is a submerged, vane-type design. Submerged pumps have a housing and internal parts inside the reservoir and operate submerged in fluid. There are two openings at the rear of the pump housing. The larger opening contains the cam ring, pressure plate, thrust plate, rotor and vane assembly and the end plate. The smaller opening contains the pressure line union, flow control valve, and spring. The flow control orifice is part of the pressure line union. The pressure relief valve, located inside the flow control valve, limits pump pressure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Pump > Component Information > Testing and Inspection > Power Steering System Test Power Steering Pump: Testing and Inspection Power Steering System Test NOTE: All tests are made with engine idling at normal operating temperature. Check idle speed adjustment and, if necessary, adjust to correct specification. 1. Place a container under steering gear or pump. 2. With engine Off, disconnect pressure hose at steering gear or power steering pump, then install J-5176-D to both hoses using adapter fitting No. J-5176-20 or equivalent. Gauge must be installed between shutoff valve and pump. 3. Open shutoff valve. 4. Remove filler cap from pump reservoir and check fluid level. Fill pump reservoir with power steering fluid to full mark on dipstick. Start engine and, momentarily holding steering wheel against stop, check connections for leakage. CAUTION: Do not hold wheel against stop for more than five seconds as pump can be damaged internally. 5. Bleed power steering system. 6. Insert thermometer No. J-5421-02 or equivalent in reservoir filler opening. Move steering wheel from stop to stop several times until thermometer indicates that hydraulic fluid in reservoir has reached a temperature of 150-170 °F. CAUTION: To prevent flat spotting tires, do not turn steering wheel more than five times without rolling vehicle to change tire to floor contact area. 7. Check pump fluid level. Add fluid if required. 8. When engine is at normal operating temperature, the initial pressure on gauge (valve open) should be within 80-125 psi. If pressure is in excess of 200 psi., check hoses for restrictions and poppet valve for proper assembly. 9. Open and close gauge valve fully three times. CAUTION: Do not leave valve closed for more than five seconds as pump could be damaged internally. 10. Record highest pressures attained each time. a. If pressures recorded are within specifications, and range of readings is within 50 psi., pump is functioning within specification. b. If pressures recorded are constant but more than 100 psi., below minimum specification, replace flow control valve and recheck. If pressures are still low, replace rotating group in pump. c. If pressure recorded are high, but do not repeat within 50 psi., flow control valve is sticking. Remove and clean valve. Remove any burrs using crocus cloth or fine hone. If system contains some dirt, flush system. If it is exceptionally dirty, both pump and gear must be completely disassembled, cleaned, flushed and reassembled before further use. 11. If pump checks within specifications, leave valve open and turn steering wheel to both stops. Record highest pressures and compare with maximum pump pressure recorded. If maximum pressure cannot be reached in either (or one) side of gear, gear is leaking internally and must be disassembled and repaired. 12. Turn engine Off, remove testing gauge, reconnect pressure hose, check fluid level and/or make needed repairs. 13. If problem still exists, steering and from suspension must be thoroughly examined. Refer to Troubleshooting. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Pump > Component Information > Testing and Inspection > Power Steering System Test > Page 9765 Power Steering Pump: Testing and Inspection Troubleshooting Fig. 1 Troubleshooting power steering system Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Pump > Component Information > Testing and Inspection > Power Steering System Test > Page 9766 Fig. 1 Troubleshooting power steering system Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Pump > Component Information > Testing and Inspection > Power Steering System Test > Page 9767 Fig. 1 Troubleshooting power steering system Refer to figures 1.1 through 1.3 when troublshooting power steering pump. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Pump > Component Information > Service and Repair > Removal/Installation Power Steering Pump: Service and Repair Removal/Installation POWER STEERING PUMP REPLACEMENT 4.3L, 5.0L, 5.7L Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Pump > Component Information > Service and Repair > Removal/Installation > Page 9770 7.4L 6.5L Tool Required J 25034-B Power Steering Pump Pulley Remover J 25033-B Power Steering Pump Pulley Installer Remove or Disconnect Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Pump > Component Information > Service and Repair > Removal/Installation > Page 9771 ^ Place a drain pan below the pump. 1. Hoses. Cap the hoses. 2. Unload the tensioner assembly. 3. Drive belt. 4. Pulley. ^ Install J 25034-B. Be sure the pilot bolt bottoms in the pump shaft by turning the nut to the top of the pilot bolt. ^ Hold the pilot bolt. ^ Turn the nut counterclockwise. 5. Front mounting bolts. 6. Rear mounting nuts from studs. 7. Pump. Install or Connect 1. Pump. 2. Front mount bolts. Tighten Tighten bolts to 50 N.m (37 lbs. ft.). 3. Rear mount nuts and studs. Tighten Tighten nuts to 50 N.m (37 lbs. ft.). 4. Pulley. ^ Place pulley on the end of the pump shaft. ^ Install J 25033-B. Be sure the pilot bolt bottoms in the shaft by turning the nut to the top of the pilot bolt. ^ Hold the pilot bolt. ^ Turn the nut clockwise. ^ Install pulley flush ± 0.25 mm (0.010 in.) with the end of the power steering pump shaft. NOTICE: Do not use arbor press or internal damage to the pump will result. 5. Drive belt. 6. Load the tensioner assembly. 7. Hoses. ^ Fill and bleed the system. Inspect ^ Hoses for clearance. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Pump > Component Information > Service and Repair > Removal/Installation > Page 9772 Power Steering Pump: Service and Repair Flushing Power Steering System 1. Raise front end of vehicle off ground until wheels are free to turn. 2. Remove fluid return line at pump reservoir inlet connector, then plug inlet connector port on pump reservoir. 3. Position fluid return line in large container. 4. While a second person fills reservoir with power steering fluid, run engine at idle. 5. Turn steering wheel from stop to stop. CAUTION: Do not contact wheel stops or hold wheel near a stop position or fluid will stop and pump will be in pressure relief mode. A sudden overflow from reservoir may develop if wheel is held at a stop. 6. Install any lines, hoses or components removed from vehicle, then fill system with new power steering fluid and bleed system. Refer to System Bleeding. 7. Operate engine for approximately 15 minutes, then remove pump return line at pump inlet and plug connection on pump. 8. While refilling reservoir, check draining fluid for contamination. If any foreign material is present, replace all lines and disassemble and clean or replace power steering system components. Do not reuse any drained power steering fluid. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Pump > Component Information > Service and Repair > Removal/Installation > Page 9773 Power Steering Pump: Service and Repair Power Steering Pump Overhaul Disassembly Fig. 2 Exploded view of power steering pump CAUTION: Before disassembly of pump, remove filler cap and drain fluid. If broken components or foreign materials are found during disassembly, hydraulic system should be disassembled, inspected, cleaned and flushed before servicing is complete. 1. Clean exterior of pump with solvent and crocus cloth. 2. Remove bolt and fitting from rear of pump reservoir, then the reservoir and seals. 3. Remove end plate retaining ring using a screwdriver and punch. 4. Remove endplate and pressure plate spring, then the O-ring, control valve and control valve spring by inverting housing. 5. Tap lightly on driveshaft with a rubber mallet to remove pressure plate. 6. Pull out pump ring and vanes, then remove shaft retaining ring, pump rotor and thrust plate. 7. Remove driveshaft key from slot in shaft, then with end of shaft pointed downward, press down until shaft is free. 8. Remove seals, dowel pins and O-rings. Inspection 1. Clean all parts with solvent and blow dry. 2. Check vane tips for scoring or wear. Vanes must fit snugly but slide freely in slots of rotor. Examine rotor slots for burrs and excessive wear at thrust faces. 3. Check inner surface of pump ring for scoring or wear and thrust plate and pressure plate for wear on plate surfaces. 4. If heavy wear is evident in any of above components, replace entire rotating group. 5. Inspect seal for leakage, cracking or swelling, if evident replace seal. 6. Check driveshaft for excessive burning or scoring. 7. Control valve must move smoothly in the valve bore. Assembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Power Steering > Power Steering Pump > Component Information > Service and Repair > Removal/Installation > Page 9774 Fig. 2 Exploded view of power steering pump 1. Lubricate O-rings, pump ring, rotor and vanes with power steering fluid. 2. Install O-rings and dowel pins on pump housing. 3. Using a seal installation tool, insert seal into front of housing. 4. Install driveshaft and thrust plate. Ensure counterbore faces driveshaft end of housing and install rotor. 5. Insert vanes into rotor, ensuring rounded edge faces away from rotor. 6. Install shaft retaining ring, pump ring and pressure plate. 7. Insert control valve spring, then install control valve and O-ring. 8. Install pressure plate spring and end plate, then secure with end plate retaining ring. 9. Connect seal and reservoir, then install bolt and fitting. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Column > Air Bag(s) Arming and Disarming > System Information > Service and Repair > Air Bag Disarming and Arming Air Bag(s) Arming and Disarming: Service and Repair Air Bag Disarming and Arming Disabling the SIR System Fig. 1 Air Bag Two-way Connector DRIVER SIDE Many service procedures require the air bag system to be disabled to prevent accidental deployment. The air bag system can maintain sufficient voltage to cause deployment for up to 2 minutes after the ignition switch is turned off, the battery ground cable is disconnected or the DERM fuse is removed. If the inflator module is disconnected from the deployment loop by the following procedure, service can begin immediately without waiting for the 2 minute time period to elapse. 1. Turn steering wheel so that vehicle wheels are pointed straight ahead. 2. Turn ignition switch to Lock position and remove key. 3. Remove air bag fuse from fuse block. 4. Remove steering column filler panel. 5. Remove Connector Position Assurance (CPA) and disconnect yellow two-way connector at base of steering column, Fig. 1. PASSENGER SIDE 1. Remove air bag fuse from fuse block. Enabling the SIR System Driver Side 1. Turn ignition switch to LOCK and remove key. 2. Connect yellow two-way connector and install connector position assurance (CPA). 3. Install steering column filler panel. 4. Insert air bag fuse into fuse block. 5. Turn ignition switch to RUN and verify that the air bag warning lamp flashes seven times then turns off. Passenger Side 1. Turn ignition switch to LOCK and remove key. 2. Insert air bag fuse into fuse block. 3. Turn ignition switch to RUN and verify that the air bag warning lamp flashes seven times then turns off. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Column > Air Bag(s) Arming and Disarming > System Information > Service and Repair > Air Bag Disarming and Arming > Page 9780 Air Bag(s) Arming and Disarming: Service and Repair General Service Precautions CAUTION: When performing service on or around SIR components or SIR wiring, follow the procedures listed below to temporarily disable the SIR system. Failure to follow procedures could result in possible air bag deployment, personal injury or otherwise unneeded SIR system repairs. The DERM can maintain sufficient voltage to cause a deployment for up to 2 minutes after the ignition switch is turned "OFF," the battery is disconnected, or the fuse powering the DERM is removed. Many of the service procedures require removal of the "AIR BAG" fuse, and disconnection of the inflator module from the deployment loop to avoid an accidental deployment. If the inflator module is disconnected from the deployment loop as noted in the "Disabling the SIR System" procedure that follows, service can begin immediately without waiting for the 2 minute time period to expire. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Column > Key Reminder Switch > Component Information > Locations Key Reminder Switch: Locations In Steering Column Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Column > Steering Column Bearing > Component Information > Technical Service Bulletins > Customer Interest for Steering Column Bearing: > 56-32-02B > Sep > 97 > Steering Column - Intermittent Click Noise/Snap Steering Column Bearing: Customer Interest Steering Column - Intermittent Click Noise/Snap File In Section: 3 - Steering/Suspension Bulletin No.: 56-32-02B Date: September, 1997 Subject: Intermittent Steering Column Snap or Click Noise when Turning (Install New Upper Bearing Spring) Models: 1994-96 Buick Century, LaSabre, Park Avenue, Regal, Roadmaster 1995-96 Buick Riviera 1994-96 Cadillac Concours, DeVille, Eldorado, Fleetwood, Seville 1994-96 Chevrolet Camaro, Caprice, Corvette, Lumina, Lumina APV 1995-96 Chevrolet Monte Carlo 1994-96 Oldsmobile Cutlass Ciera, Cutlass Supreme, Eighty Eight, Ninety Eight, Silhouette 1995-96 Oldsmobile Aurora 1994-96 Pontiac Bonneville, Firebird, Grand Prix, Trans Sport with Tilt Steering Columns 1995-96 Chevrolet and GMC C/K, S/T Trucks 1994-96 Chevrolet and GMC M/L, G Vans with Tilt Steering Columns This bulletin is being revised to correct the truck models and part number descriptions. Please discard Corporate Bulletin Number 56-32-02A, dated April, 1996 (Section 3 Steering/Suspension). Condition Some owners may comment on an intermittent steering column snap or click noise while turning. The snapping or clicking may also be felt in the steering wheel. Cause The upper bearing race seat may, under some turning conditions, move in an axial direction along the upper steering shaft. The noise is a result of the inner race seat hanging up on the shaft and then suddenly releasing causing a snapping or clicking noise. Correction A new upper bearing spring with increased stiffness has been developed and should- be installed in the steering column. The new spring will increase the preload between the upper bearing inner race seat and the upper steering shaft. To accommodate the new spring with increased stiffness, the cancel cam will also need to be replaced. The new spring and cancel cam, along with a retainer ring and an upper bearing inner race seat are included in the parts kit listed below. Service Procedure Follow the instructions given in Section 3F5 of the appropriate Service Manual and those contained in kit. Be sure to use all parts supplied in the service kit. Parts Information Part Number Description 26059701 1994-96 A/B/C/D/E/F/H/K/U/W 26059701 1994-95 M/L/G Vans 26059702 1995-96 Buick "G" 26059703 1995-96 Oldsmobile "G" 26059704 1995-96 C/K, S/T Truck 26059704 1996 MIL/G Vans (both styles of G Van) 26059705 1994-96 "Y" Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Column > Steering Column Bearing > Component Information > Technical Service Bulletins > Customer Interest for Steering Column Bearing: > 56-32-02B > Sep > 97 > Steering Column - Intermittent Click Noise/Snap > Page 9792 Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Column > Steering Column Bearing > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Steering Column Bearing: > 56-32-02B > Sep > 97 > Steering Column - Intermittent Click Noise/Snap Steering Column Bearing: All Technical Service Bulletins Steering Column - Intermittent Click Noise/Snap File In Section: 3 - Steering/Suspension Bulletin No.: 56-32-02B Date: September, 1997 Subject: Intermittent Steering Column Snap or Click Noise when Turning (Install New Upper Bearing Spring) Models: 1994-96 Buick Century, LaSabre, Park Avenue, Regal, Roadmaster 1995-96 Buick Riviera 1994-96 Cadillac Concours, DeVille, Eldorado, Fleetwood, Seville 1994-96 Chevrolet Camaro, Caprice, Corvette, Lumina, Lumina APV 1995-96 Chevrolet Monte Carlo 1994-96 Oldsmobile Cutlass Ciera, Cutlass Supreme, Eighty Eight, Ninety Eight, Silhouette 1995-96 Oldsmobile Aurora 1994-96 Pontiac Bonneville, Firebird, Grand Prix, Trans Sport with Tilt Steering Columns 1995-96 Chevrolet and GMC C/K, S/T Trucks 1994-96 Chevrolet and GMC M/L, G Vans with Tilt Steering Columns This bulletin is being revised to correct the truck models and part number descriptions. Please discard Corporate Bulletin Number 56-32-02A, dated April, 1996 (Section 3 Steering/Suspension). Condition Some owners may comment on an intermittent steering column snap or click noise while turning. The snapping or clicking may also be felt in the steering wheel. Cause The upper bearing race seat may, under some turning conditions, move in an axial direction along the upper steering shaft. The noise is a result of the inner race seat hanging up on the shaft and then suddenly releasing causing a snapping or clicking noise. Correction A new upper bearing spring with increased stiffness has been developed and should- be installed in the steering column. The new spring will increase the preload between the upper bearing inner race seat and the upper steering shaft. To accommodate the new spring with increased stiffness, the cancel cam will also need to be replaced. The new spring and cancel cam, along with a retainer ring and an upper bearing inner race seat are included in the parts kit listed below. Service Procedure Follow the instructions given in Section 3F5 of the appropriate Service Manual and those contained in kit. Be sure to use all parts supplied in the service kit. Parts Information Part Number Description 26059701 1994-96 A/B/C/D/E/F/H/K/U/W 26059701 1994-95 M/L/G Vans 26059702 1995-96 Buick "G" 26059703 1995-96 Oldsmobile "G" 26059704 1995-96 C/K, S/T Truck 26059704 1996 MIL/G Vans (both styles of G Van) 26059705 1994-96 "Y" Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Column > Steering Column Bearing > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Steering Column Bearing: > 56-32-02B > Sep > 97 > Steering Column - Intermittent Click Noise/Snap > Page 9798 Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Technical Service Bulletins > Tools - Adjuster Locknut Wrench Steering Gear: Technical Service Bulletins Tools - Adjuster Locknut Wrench File In Section: 3 - Steering/Suspension Bulletin No.: 83-32-10 Date: November, 1998 INFORMATION Subject: Essential Tool J 43435 Adjuster Locknut Wrench Models: 1990-99 Passenger Cars and Trucks with Integral Power Steering A new essential tool, J 43435 Adjuster Locknut Wrench, has been sent to all GM Dealers. This tool should be used on all Integral power steering gears, both past and current models. The following procedure should be used In place of existing Service Manual procedures for Coupling Shield and Locknut Removal and Replacement. The correct adjustment procedure and use of the essential tools are critical to restore the vehicle "On Center" feel (See Figure 1). Important: Coupling shield retainer and locknut assembly replacement procedures require the following special tools: J 42882 Adjuster Nut Wrench J 43435 Adjuster Locknut Wrench Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Technical Service Bulletins > Tools - Adjuster Locknut Wrench > Page 9803 (See Figure 2) Procedure 1. Place J 42882 over the end of the stub shaft. Place J 43435 over the end. J 43435 is reversible and can be used with both old and new style coupling shield retainers and locknuts. 2. Tighten the coupling shield retainer and locknut assembly after an adjustment or repair has been made to the power steering gear to the specified torque (See Figure 3). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Technical Service Bulletins > Page 9804 Steering Gear: Specifications Component .......................................................................................................................................... ..................................................................... Ft. Lbs. Adjuster Jam Nuts ............................................................................................................................... ............................................................................... 32 Coupling Clamp Bolt ....................................... .............................................................................................................................................................. .... 22 Gear To Frame Bolts ................................................................................................................. ....................................................................................... 100 Pitman Shaft Nut .................................. .............................................................................................................................................................. .............. 180 Pressure Line Fitting (At Gear) ...................................................................................... .................................................................................................... 20 Pressure Line Fitting (At Pump) .............................................................................................................................................................. ........................... 20 Pump Mounting Bolts ......................................................................................... ............................................................................................................... 37 Side Cover Bolts ............. .............................................................................................................................................................. ..................................... 48 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Technical Service Bulletins > Page 9805 Steering Gear: Application and ID This vehicle uses a Saginaw 708 series integral power steering gear. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Technical Service Bulletins > Page 9806 Steering Gear: Description and Operation Fig. 1 Exploded view of power steering gear The power steering gear has a recirculating ball system which acts as a rolling thread between the worm shaft and the rack piston. The worm shaft is supported by a thrust bearing preload and two conical thrust races at the lower end, and a bearing assembly in the adjuster plug at the upper end. The control valve in the steering gear directs the power steering fluid to either side of the rack piston. The rack piston converts the hydraulic pressure into a mechanical force. If the steering system loses hydraulic pressure, the vehicle can be controlled manually. When the worm shaft is turned right, the rack piston moves up in the gear while turning left moves the rack piston down in the gear. The rack piston teeth mesh with the pitman shaft sector. Turning the worm shaft turns the pitman shaft, which turns the wheels through the steering linkage. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Testing and Inspection > Symptom Related Diagnostic Procedures Steering Gear: Symptom Related Diagnostic Procedures Fig. 1 Troubleshooting power steering system Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Testing and Inspection > Symptom Related Diagnostic Procedures > Page 9809 Fig. 1 Troubleshooting power steering system Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Testing and Inspection > Symptom Related Diagnostic Procedures > Page 9810 Fig. 1 Troubleshooting power steering system Refer to figures when troubleshooting power steering pump. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Testing and Inspection > Symptom Related Diagnostic Procedures > Page 9811 Steering Gear: Component Tests and General Diagnostics NOTE: All tests are made with engine idling at normal operating temperature. Check idle speed adjustment and, if necessary, adjust to correct specification. 1. Place a container under steering gear or pump. 2. With engine Off, disconnect pressure hose at steering gear or power steering pump, then install J-5176-D to both hoses using adapter fitting No. J-5176-20 or equivalent. Gauge must be installed between shutoff valve and pump. 3. Open shutoff valve. 4. Remove filler cap from pump reservoir and check fluid level. Fill pump reservoir with power steering fluid to full mark on dipstick. Start engine and, momentarily holding steering wheel against stop, check connections for leakage. CAUTION: Do not hold wheel against stop for more than five seconds as pump can be damaged internally. 5. Bleed power steering system. 6. Insert thermometer No. J-5421-02 or equivalent in reservoir filler opening. Move steering wheel from stop to stop several times until thermometer indicates that hydraulic fluid in reservoir has reached a temperature of 150-170 °F. CAUTION: To prevent flat spotting tires, do not turn steering wheel more than five times without rolling vehicle to change tire to floor contact area. 7. Check pump fluid level. Add fluid if required. 8. When engine is at normal operating temperature, the initial pressure on gauge (valve open) should be within 80-125 psi. If pressure is in excess of 200 psi., check hoses for restrictions and poppet valve for proper assembly. 9. Open and close gauge valve fully three times. CAUTION: Do not leave valve closed for more than five seconds as pump could be damaged internally. 10. Record highest pressures attained each time. a. If pressures recorded are within specifications, and range of readings is within 50 psi., pump is functioning within specification. b. If pressures recorded are constant but more than 100 psi., below minimum specification, replace flow control valve and recheck. If pressures are still low, replace rotating group in pump. c. If pressure recorded are high, but do not repeat within 50 psi., flow control valve is sticking. Remove and clean valve. Remove any burrs using crocus cloth or fine hone. If system contains some dirt, flush system. If it is exceptionally dirty, both pump and gear must be completely disassembled, cleaned, flushed and reassembled before further use. 11. If pump checks within specifications, leave valve open and turn steering wheel to both stops. Record highest pressures and compare with maximum pump pressure recorded. If maximum pressure cannot be reached in either (or one) side of gear, gear is leaking internally and must be disassembled and repaired. 12. Turn engine Off, remove testing gauge, reconnect pressure hose, check fluid level and/or make needed repairs. 13. If problem still exists, steering and from suspension must be thoroughly examined. Refer to Troubleshooting. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Adjustments > Worm Bearing Preload Steering Gear: Adjustments Worm Bearing Preload Fig. 12 Adjuster plug nut removal 1. Loosen and remove adjuster plug nut. Fig. 4 Adjuster plug removal 2. Turn adjuster plug clockwise using spanner wrench tool J-7624 or equivalent, until plug and thrust bearing are firmly bottomed in housing. 3. Scribe an index mark on the housing even with a hole on adjuster plug. Fig. 13 Adjuster plug alignment mark 4. Measure back 3/16 - 1/4 inch from first index mark and scribe a second index mark. 5. Rotate adjuster plug counterclockwise until hole is aligned with second index mark. 6. Install adjuster plug nut, tighten to specifications. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Adjustments > Worm Bearing Preload > Page 9814 Fig. 14 Stub shaft torque reading 7. Using an inch-pound torque wrench and a 12-point deep socket, measure torque required to turn stub shaft. Take reading with handle of torque wrench near vertical position. Turn stub shaft to right stop, then back 1/4 turn at an even rate. Record torque reading. 8. Torque reading should be 4-10 inch lbs. If not, adjuster plug may not be tightened properly or may have turned during adjuster plug nut installation. Thrust bearings and races may also be damaged. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Adjustments > Worm Bearing Preload > Page 9815 Steering Gear: Adjustments Over Center Preload Fig. 15 Stub shaft alignment 1. Turn pitman shaft adjuster screw counterclockwise until fully extended, then reverse 1/2 turn clockwise. 2. Rotate stub shaft from stop to stop and count number of turns. 3. Starting at either stop, turn stub shaft halfway back. When gear is centered, flat on stub shaft will face upward and be parallel with side cover. 4. Place torque wrench on stub shaft and rotate 45° each side of center. Record highest drag torque measured on or near center. 5. Adjust over-center drag torque by loosening adjuster screw jam nut and turning pitman shaft adjuster screw clockwise until correct drag torque is obtained. 6. On new steering gears, add 6-10 inch lbs. torque to previously measured worm bearing preload torque. Do not exceed a total steering gear preload of 18 inch lbs. 7. On used steering gears, add 4-5 inch lbs. torque to previously measured worm bearing preload torque. Do not exceed a total steering gear preload of 14 inch lbs. 8. Install and tighten adjuster screw jam nut to specifications. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Service and Repair > Manual Steering Gear - Saginaw Recirculation Ball Steering Gear: Service and Repair Manual Steering Gear - Saginaw Recirculation Ball 1. Place front wheels in straight ahead position. 2. Remove flexible coupling to steering shaft bolts. 3. Mark position of pitman arm to shaft and remove pitman shaft nut or pinch bolt, then pitman arm from shaft with a puller. 4. Loosen steering gear and remove. 5. Remove flexible coupling pinch bolt, then flexible coupling from steering gear wormshaft. 6. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Service and Repair > Manual Steering Gear - Saginaw Recirculation Ball > Page 9818 Steering Gear: Service and Repair Saginaw Integral Power Steering Gear Component Service If broken components or foreign materials are found during disassembly of the gear, the hydraulic system should be inspected, cleaned and flushed before service is complete. The ball nut and control rings are not generally replaced unless cut or damaged. If replacing, inspect all mating parts for burrs, cracks, scratches or damage. Replace or repair as needed. System Bleeding Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Service and Repair > Manual Steering Gear - Saginaw Recirculation Ball > Page 9819 Fig. 2 Power Steering System Bleed Chart 1. Fill pump fluid reservoir to proper level and let fluid settle for at least two minutes. 2. Start and run engine for a few seconds. Do not turn steering wheel. 3. Turn engine OFF. Check fluid level, add fluid if necessary. 4. Repeat above procedure until fluid level remains constant after running engine. 5. Raise front end of vehicle so wheels are off ground. 6. Start engine. Slowly turn steering wheel in both directions, lightly contacting wheel stops. 7. Add power steering fluid, if necessary. 8. Lower vehicle and turn steering wheel slowly from lock to lock. 9. Stop engine. Check fluid level and refill as required. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Service and Repair > Manual Steering Gear - Saginaw Recirculation Ball > Page 9820 10. If fluid is extremely foamy, allow vehicle to stand a few minutes and repeat above procedure. For additional bleed procedures, refer to Fig. 2. Flushing Power Steering System 1. Raise front end of vehicle off ground until wheels are free to turn. 2. Remove fluid return line at pump reservoir inlet connector, then plug inlet connector port on pump reservoir. 3. Position fluid return line in large container. 4. While a second person fills reservoir with power steering fluid, run engine at idle. 5. Turn steering wheel from stop to stop. CAUTION: Do not contact wheel stops or hold wheel near a stop position or fluid will stop and pump will be in pressure relief mode. A sudden overflow from reservoir may develop if wheel is held at a stop. 6. Install any lines, hoses or components removed from vehicle, then fill system with new power steering fluid and bleed system. Refer to System Bleeding. 7. Operate engine for approximately 15 minutes, then remove pump return line at pump inlet and plug connection on pump. 8. While refilling reservoir, check draining fluid for contamination. If any foreign material is present, replace all lines and disassemble and clean or replace power steering system components. Do not reuse any drained power steering fluid. Disassembly Fig. 1 Exploded view of power steering gear 1. Pry retaining ring out of housing groove with a screwdriver. 2. Turn stub shaft to the left until plug on opposite end is forced out of cylinder, then remove seal. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Service and Repair > Manual Steering Gear - Saginaw Recirculation Ball > Page 9821 Fig. 2 Rack piston plug removal 3. Remove plug from rack piston. 4. Remove nut, bolt, side cover and gasket, then turn adjuster screw right until side cover separates from pitman shaft. 5. Remove piston shaft, then turn stub shaft left until pitman shaft teeth and rack piston disengage. Fig. 3 Bearing removal 6. Remove retaining ring, washers and seals, then remove bearing with bearing removal tool No. J-6278 or equivalent if necessary. 7. Remove rack piston and balls as follows: a. Insert ball retainer tool J-21552 or equivalent into rack piston bore with pilot seated into end of worm. b. Hold tool against worm and turn stub shaft to left. Rack piston will be forced onto the tool. c. Hold tool and pull rack piston toward handle until it is against flange. This will prevent end circuit balls from falling out. Fig. 4 Adjuster plug removal 8. Remove adjuster nut, then remove adjuster plug using spanner wrench tool J-7624 or equivalent. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Service and Repair > Manual Steering Gear - Saginaw Recirculation Ball > Page 9822 Fig. 5 Needle bearing removal 9. Disassemble adjuster plug as follows: a. Remove retaining ring, washer, seal and bearing. b. Remove bearing retainer by prying at raised area, then remove seal and needle bearing with adjuster plug bearing installer tool J-8524-2 and driver tool J-7079-2 or equivalents. Fig. 6 Worm shaft & valve body removal 10. Remove valve and worm shaft as an assembly with both races and bearing. Separate as follows: a. Remove worm shaft from valve body. b. Remove races and bearing from worm shaft, them remove seal. Fig. 7 Stub shaft pin disengage 11. Remove stub shaft from valve body as follows: a. Hold assembly and lightly tap stub shaft against a bench until shaft cap is free from valve body. b. Pull shaft assembly until shaft cap clears valve body by approximately 1/4 inch. c. Remove valve spool and seals. 12. Remove screws, clamp and ball guide from rack piston, then remove balls. 13. Remove connectors from housing. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Service and Repair > Manual Steering Gear - Saginaw Recirculation Ball > Page 9823 Assembly Fig. 8 Connector installation 1. Install connectors using valve connector installer tool J-6217 or equivalent. Fig. 9 Recirculating ball installation Fig. 2 Rack piston plug removal 2. Lubricate 24 balls with power steering fluid, then install alternately by color into rack piston. Use ball retainer tool J-21552 or equivalent, to hold balls inside. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Service and Repair > Manual Steering Gear - Saginaw Recirculation Ball > Page 9824 Fig. 10 Ball guide installation 3. Install balls in ball guide alternately by color, retain in guide with petroleum jelly. 4. Connect ball guide, clamp and screws to rack piston. 5. Lubricate stub shaft, valve spool and seals with power steering fluid, then install into valve body. 6. Connect valve body, seal, worm shaft, races and roller bearing. Fig. 11 Needle bearing installation 7. Install seal on adjuster plug, then needle bearing in adjuster plug using J-8524-1 and J-7079-2 or equivalent. 8. Install seal, washer and retaining ring in adjuster plug. CAUTION: Retainer projections must not extend beyond washer when retainer ring is seated. Washer must rotate freely. 9. Install worm shaft and valve assembly into gear housing. Fig. 4 Adjuster plug removal 10. Install adjuster plug into gear housing using spanner wrench tool J-7624 or equivalent. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Gear > Component Information > Service and Repair > Manual Steering Gear - Saginaw Recirculation Ball > Page 9825 Steering Gear: Service and Repair Power Steering Gear Replace To remove gear assembly, disconnect pressure and return hoses from gear housing and cap both hoses and steering gear outlets to prevent foreign material from entering system. Then Refer to, Manual Steering Gear-Saginaw Recirculation Ball. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Wheel > Component Information > Service and Repair Steering Wheel: Service and Repair TOOL REQUIRED: ^ J 1859-A Steering Wheel Puller Or Equivalent REMOVE OR DISCONNECT 1. Negative battery cable. 2. Disable the SIR system (if equipped). See: Steering Column/Air Bag(s) Arming and Disarming/Service and Repair 3. Inflator module. See: Restraint Systems/Air Bag Systems/Air Bag/Service and Repair 4. Horn contact (if equipped with SIR). See: Lighting and Horns/Horn/Horn Switch/Service and Repair 5. Horn pad assembly (if not equipped with SIR). See: Lighting and Horns/Horn/Horn Switch/Service and Repair 6. Steering wheel nut. Notice the alignment mark and its relationship to the steering wheel and steering shaft. 7. Steering wheel using J 1859-A. CAUTION: Do not hammer on the puller or damage could result to the steering column. INSTALL OR RECONNECT CAUTION: Always use the correct fastener in the proper location. When you replace a fastener, use ONLY the exact part number for that application. The manufacturer will call out those fasteners that require a replacement after removal. The manufacturer will also call out the fasteners that require thread lockers or thread sealant. UNLESS OTHERWISE SPECIFIED, do not use supplemental coatings (paints, greases, or other corrosion Inhibitors) on threaded fasteners or fastener joint interfaces. Generally, such coatings adversely affect the fastener torque and joint clamping force, and may damage the fastener. When you install fasteners, use the correct tightening sequence and specifications. Following these instructions can help you avoid damage to parts and systems. 1. Steering wheel onto the steering shaft. Align the marks on steering shaft and steering wheel. 2. Steering wheel nut. Tighten to 40 Nm (30 ft. lbs.). 3. Horn pad assembly (if not equipped with SIR). See: Lighting and Horns/Horn/Horn Switch/Service and Repair 4. Horn contact (if equipped with SIR). See: Lighting and Horns/Horn/Horn Switch/Service and Repair Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Steering > Steering Wheel > Component Information > Service and Repair > Page 9829 5. Inflator module assembly. See: Restraint Systems/Air Bag Systems/Air Bag/Service and Repair 6. Negative battery cable. 7. Enable the SIR system (if equipped with SIR). See: Steering Column/Air Bag(s) Arming and Disarming/Service and Repair Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Ball Joint > Component Information > Testing and Inspection > Upper Ball Joint: Testing and Inspection Upper 1. Wipe ball joints clean and check seals for damage. If seals are damaged, replace ball joint. 2. Adjust wheel bearings. 3. Check ball joint for vertical looseness as follows: a. With vehicle on jack stands, place dial indicator against spindle to show vertical movement. b. Pry between lower control arm and outer race while reading dial indicator. c. If dial indicator reading is more than 0.08 inch, replace ball joint. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Ball Joint > Component Information > Testing and Inspection > Upper > Page 9835 Ball Joint: Testing and Inspection Lower 1. Wipe ball joints clean and check seals for damage. If seals are damaged, replace ball joint. 2. Adjust wheel bearings. 3. Check ball joint for vertical looseness as follows: a. With vehicle on jack stands, place dial indicator against spindle to show vertical movement. b. Pry between lower control arm and outer race while reading dial indicator. c. If dial indicator reading is more than 0.08 inch, replace ball joint. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Ball Joint > Component Information > Service and Repair > Upper Ball Joint Ball Joint: Service and Repair Upper Ball Joint TOOL REQUIRED: J 23742 Ball Joint Separator IMPORTANT ^ Raise the vehicle and support it with safety stands. ^ Support the control arm with a jack. CAUTION: Floor jack or stand must remain under the control arm spring seat during removal and installation to retain the spring and control arm in position or personal injury may result. Fig. 8 Control arms & components REMOVE OR DISCONNECT 1. Tire and wheel assembly. 2. Brake caliper. IMPORTANT: Support the caliper with a piece of wire to prevent damage to the brake line. 3. Rivets from the upper ball joint (66). Drilling The Upper Ball Joint Rivets A. Use a 3.175 mm (1/8 inch) drill to cut a 6.35 mm (1/4 inch) deep hole in the center of each rivet. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Ball Joint > Component Information > Service and Repair > Upper Ball Joint > Page 9838 Drilling The Upper Ball Joint Heads B. Drill the rivet heads away using a 12.75 mm (1/2 inch) drill. Removing The Upper Ball Joint Rivets C. Punch the rivets out using a small pin punch. 4. Cotter pin. Fig. 8 Control arms & components 5. Stud nut (67) from the upper ball joint (66). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Ball Joint > Component Information > Service and Repair > Upper Ball Joint > Page 9839 Disconnecting The Upper Ball Joint A. Use J 23742. B. Apply pressure on the tool until the stud breaks loose. C. Remove J 23742. D. Pull the stud away from the knuckle. IMPORTANT: Support the knuckle assembly so that its weight will not damage the brake hose. 6. Upper ball joint (66). Fig. 8 Control arms & components INSTALL OR CONNECT 1. New upper ball joint (66) to the upper control arm (42). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Ball Joint > Component Information > Service and Repair > Upper Ball Joint > Page 9840 Installing The Upper Ball Joint ^ Position four attaching bolts and nuts. Tighten nuts (A) to 24 Nm (18 lb. ft.). ^ Take the support away from the knuckle assembly. 2. Upper ball joint (66) to the steering knuckle. 3. Stud nut (67). Tighten nut (67) to 100 Nm (74 lb. ft.). ^ Align the slot in the stud nut with the hole in the stud by tightening the stud nut. 4. New cotter pin. 5. Brake caliper. 6. Tire and wheel assembly. 7. Lower the vehicle. IMPORTANT ^ Check the running clearance at all suspension components. ^ Check the front wheel alignment. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Ball Joint > Component Information > Service and Repair > Upper Ball Joint > Page 9841 Ball Joint: Service and Repair Lower Ball Joint TOOLS REQUIRED: J 9519-E Ball Joint Remover and Installer Set J 23742 Ball Joint Separator J 9519-40 Lower Ball Joint Remover Adapter J 9519-E Ball Joint Remover and Installer Set IMPORTANT: Raise the vehicle and support the frame with suitable safety stands. Fig. 8 Control arms & components REMOVE OR DISCONNECT 1. Tire and wheel assembly. Place a floor jack under the control arm spring seat and raise it until it supports the control arm. CAUTION: Floor jack must remain under the control arm spring seat during removal and Installation to retain the spring and control arm in position or personal injury may result. 2. Brake caliper. IMPORTANT: Support the caliper with a piece of wire to prevent damage to the brake line. 3. Cotter pin (68) and the nut (67). Use J 23742 to break the ball joint loose from the knuckle. 4. Lower control arm (40) from the knuckle. ^ Guide the control arm out of the splash shield with a screwdriver while lifting the upper control arm with a pry bar. IMPORTANT: Block the knuckle assembly out of the way by placing a wooden block between the frame and upper control arm. Removing The Lower Ball Joint Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Ball Joint > Component Information > Service and Repair > Upper Ball Joint > Page 9842 5. Lower ball joint (69) from the lower control arm. INSPECT ^ The tapered hole in the steering knuckle and remove any dirt. If the hole is out of round, deformed or damaged, the knuckle must be replaced. Installing The Lower Ball Joint INSTALL OR CONNECT 1. New ball joint (69) into the lower, control arm (40). ^ Press in the ball joint. The ball joint will bottom on the control arm. 2. Ball joint stud into the steering knuckle. 3. Stud nut (67) onto the stud. Tighten nut (67) to 128 Nm (94 lb. ft.) and align the slot in the stud nut with the hole in the stud by tightening. 4. New cotter pin (68) to the stud. 5. Brake caliper. 8. Tire and wheel assembly. ^ Lower the vehicle. IMPORTANT: Check the front wheel alignment. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Control Arm > Control Arm Bushing > Component Information > Service and Repair Control Arm Bushing: Service and Repair The bushings on are welded in position and are not serviceable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Front Steering Knuckle > Component Information > Specifications Front Steering Knuckle: Specifications Lower Ball Joints to Steering Knuckle Nut ............................................................................................................................................. 128 Nm (94 ft. lb.) Upper Ball Joints to Steering Knuckle Nut ............................................................................................................................................. 100 Nm (74 ft. lb.) Splash Shield to Steering Knuckle Bolts ................................................................................................................................................... 26 Nm (19 ft. lb.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Stabilizer Bar, Sway Control > Component Information > Service and Repair Stabilizer Bar: Service and Repair Fig. 6 Stabilizer Shaft Components 1. Raise and support vehicle. 2. Remove nut from link bolt, Fig. 6. 3. Remove link bolt. 4. Remove spacer, attaching bolts, bracket and stabilizer shaft. 5. Remove bushing. 6. Reverse procedure to install. Tighten bracket attaching bolts to specification and link bolt assembly attaching bolt to 13 ft. lbs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Suspension Spring ( Coil / Leaf ) > Shackle > Component Information > Service and Repair Shackle: Service and Repair Fig. 6 Rear Axle Trim Height 1. Raise and support vehicle, then the axle. 2. Loosen shackle to spring attaching bolt. 3. Remove shackle to rear bracket bolt, nut and washers. 4. Remove shackle to spring nut, washers and bolt. 5. Remove shackle from vehicle. 6. Reverse procedure to install. To adjust spring height, proceed as follows: a. Adjust spring height to obtain a measurement of 7.17 inches between top surface of axle jounce pad and bottom surface of the frame jounce bracket. b. After adjustment, tighten front and rear spring nuts and shackle nut to specification. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Suspension Strut / Shock Absorber > Component Information > Technical Service Bulletins > Suspension - Shock Absorber/Strut Leakage Information Suspension Strut / Shock Absorber: Technical Service Bulletins Suspension - Shock Absorber/Strut Leakage Information INFORMATION Bulletin No.: 05-03-08-002C Date: October 16, 2009 Subject: Information on Replacement of Shock Absorbers and Struts Due to Fluid Leaks Models: 2010 and Prior GM Passenger Cars and Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add the 2010 model year and Inspection Procedures. Please discard Corporate Bulletin Number 05-03-08-002B (Section 03 - Suspension). This bulletin is intended to help identify the severity of shock absorber and strut fluid seepage. Improper diagnosis may lead to components being replaced that are within the manufacturer's specification. Shock absorbers and strut assemblies are fluid-filled components and will normally exhibit some seepage. Seepage is defined as oil film or dust accumulation on the exterior of the shock housing. Shock absorbers and struts are not to be replaced under warranty for seepage. Use the following information to determine if the condition is normal acceptable seepage or a defective component. Important Electronically controlled shock absorbers (MR) may have a tendency to attract dust to this oil film. Often this film and dust can be wiped off and will not return until similar mileage is accumulated again. Inspection Procedure Note The shock absorber or strut assembly DOES NOT have to be removed from the vehicle to perform the following inspection procedure. Use the following descriptions and graphics to determine the serviceability of the component. Shock Absorbers Do Not Replace shock absorbers displaying condition 1 or 2 levels of seepage. 1. Oil or fluid residue only on the bottom or top of the shock absorber and not originating from the shaft seal (the upper part of the lower shock tube). 2. Light film/residue on approximately 1/3 (a) or less of the lower shock tube (A) and originating from the shaft seal. Replace shock absorbers displaying conditions 3 and 4 levels of leaks. 3. Oil drip or trail down the lower shock tube and originating from the shaft seal. 4. An extreme wet film of oil covering more than 1/3 (b) of the lower shock tube and originating from the shaft seal. Coil-over Shock Absorber Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Suspension Strut / Shock Absorber > Component Information > Technical Service Bulletins > Suspension - Shock Absorber/Strut Leakage Information > Page 9861 Do Not Replace coil-over shock absorbers displaying condition 1 or 2 levels of seepage. 1. Oil or fluid residue only on the bottom of the lower shock absorber tube or the coil-over shock absorber components and not originating from the shaft seal (located at the top of the coil-over shock tube). 2. Light film/residue on the shock absorber tube, but not on the spring seat and originating from the shaft seal. Replace coil-over shock absorbers displaying conditions 3 and 4 levels of leaks. 3. Oil drip or trail down the lower shock tube and originating from the shaft seal. 4. An extreme, wet film of oil covering the shock absorber tube and pooling in the spring seat and originating from the shaft seal. Struts Do Not Replace Struts displaying condition 1 or 2 levels of seepage. 1. Oil or fluid residue only on the bottom of the strut tube or on other strut components and not originating from the shaft seal. 2. Light film/residue on the strut tube, but not on the spring seat and originating from the shaft seal. Replace Struts displaying conditions 3 and 4 levels of leaks. 3. Oil drip or trail down the strut tube and originating from the shaft seal (located at the top of the strut tube). 4. Extreme wet film of oil covering the strut tube and pooling in the spring seat and originating from the shaft seal. Correction Use the information published in SI for diagnosis and repair. Use the applicable published labor operation. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Suspension Strut / Shock Absorber > Component Information > Technical Service Bulletins > Suspension - Shock Absorber/Strut Leakage Information > Page 9862 Suspension Strut / Shock Absorber: Technical Service Bulletins Suspension - Shock Absorber/Strut Replacement Guidlines File In Section: Warranty Administration Bulletin No.: 72-05-12 Date: January, 1998 WARRANTY ADMINISTRATION Subject: Replacement of Shock Absorbers and Struts Labor Operations E3800, E3801, E3807, E5800, E5801, E5807, E3850, E3851, E3857, E5750, E5751, and E5757 Models: All Past, Present, and Future Passenger Cars & Trucks The purpose of this bulletin is to provide retail and wholesale service personnel with enhanced service policies for the above listed subject labor operations. Service Management should make certain that all dealership personnel responsible for replacement of suspension components are familiar with GM Service Manual procedures. Effective with repair orders dated on or after January 15, 1998 the following must also be followed: - Shock absorber/strut assemblies are fluid filled components and will normally exhibit seepage. Seepage is defined as oil film or dust accumulation on the exterior of the shock housing. Shock absorber/strut assemblies are not to be replaced under warranty or seepage. - Defective shock absorber/strut assemblies will have a visible oil path or drip coming from the component. A visible oil path or drip coming from the shock absorber/strut assembly should be replaced as a defective component. - Only defective shock absorber/strut assemblies should be replaced. DO NOT replace pairs unless both are defective, unless otherwise instructed in the Service Manual and/or Service Bulletin. - Service Management approval is required on the repair order for replacement of struts or shocks in pairs. This approval includes noting the reason for replacement. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Suspension Strut / Shock Absorber > Component Information > Technical Service Bulletins > Page 9863 Suspension Strut / Shock Absorber: Service and Repair Fig. 5 Shock Absorber Attachment 1. Raise and support vehicle. 2. Remove shock absorber attaching nut, Fig. 5. 3. Remove retainer, grommet and attaching bolts. 4. Remove shock absorber. 5. Reverse procedure to install. Tighten attaching nut to specification and torque attaching bolts to 20 ft. lbs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Wheel Bearing > Component Information > Adjustments > Front Wheel Bearing: Adjustments Front FRONT WHEEL BEARINGS ADJUSTMENT Fig. 5 Hub, knuckle & bearing components. REMOVE 1. Raise and support vehicle. 2. Remove wheel cover, if equipped. 3. Remove cap from hub/disc assembly. 4. Remove cotter pin. 5. Tighten nut (12), Fig. 5, to 12 ft lbs, while turning wheel forward by hand. This will seat the bearing. 6. Loosen nut (12) to a just loose position, then back nut off until hole in the spindle aligns with a slot in the nut. Do not back the nut off more than 1/2 flat. INSTALL 1. New cotter pin. With wheel bearing properly adjusted, there will be .001---.005 inch endplay. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Wheel Bearing > Component Information > Adjustments > Front > Page 9868 Wheel Bearing: Adjustments Rear Dana/Spicer Full Floating Axle REAR WHEEL BEARINGS ADJUSTMENT Ensure the brakes are completely released and do not drag. Check wheel bearing play by grasping the tire at the top and pulling and pushing back and forth, or by using a pry bar under the tire. If the wheel bearings are properly adjusted, movement of the brake drum in relation to the brake flange plate will be barely noticeable and the wheel will turn freely. If the movement is excessive, adjust the bearings as follows: 1. Back off attaching nut until just loose, but not more than one slot of the lock or the axle spindle using wheel bearing nut wrench tool No. J-2222-C or equivalent. 2. Align adjusting nut slot with keyway in the axle spindle. Rockwell Full Floating Axle REAR WHEEL BEARINGS ADJUSTMENT Ensure the brakes are completely released and do not drag. Check wheel bearing play by grasping the tire at the top and pulling and pushing back and forth, or by using a pry bar under the tire. If the wheel bearings are properly adjusted, movement of hub or disc will be barely noticeable. If the movement is excessive, adjust the bearings as follows: 1. Raise and support vehicle. 2. Remove axle shaft. 3. Remove retaining nut and lock washer. 4. Using nut wrench tool No. J-25510, or equivalent, torque adjusting nut, with hub rotating, to 50.0 ft. lbs. Ensure bearing surfaces are in contact, then back adjusting nut off 1/8 turn. 5. Install lock washer, the bend tang over flat of adjusting nut. 6. Install retaining nut and torque to 250 ft. lbs. 7. Install axle shaft. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Wheel Bearing > Component Information > Service and Repair > Front Wheel Bearing: Service and Repair Front FRONT WHEEL BEARINGS AND/OR HUB Fig. 5 Hub, knuckle & bearing components. REMOVE 1. Disconnect battery ground cable. 2. Raise and support vehicle, then remove brake caliper. 3. Remove cap from hub/disc assembly, Fig. 5. 4. Remove cotter pin, nut and washer. 5. Remove hub/disc from spindle. 6. Remove outer bearing, seal, inner bearing and cup. INSTALL 1. Reverse procedure to install. Note the following: a. Clean all components before installing. b. Apply an approved high temperature front wheel bearing grease to the spindle at the inner and outer bearing seat, shoulder and seal seat. Also finger apply a small amount of grease inboard of each bearing cup in the hub/disc assembly. Pressure pack the bearings with a grease machine or hand pack them. Ensure grease is worked thoroughly into the rollers, cone and cage. c. When installing inner bearing, apply an additional quantity of grease outboard of the inner bearing. d. Torque nut (12) 10-12 ft lbs while turning the wheel assembly forward by hand. Apply grease to the outboard side of the outer bearing. Adjust wheel bearings. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Wheel Bearing > Component Information > Service and Repair > Front > Page 9871 Wheel Bearing: Service and Repair Rear REAR WHEEL BEARINGS 1. Raise and support vehicle. 2. Remove axle shaft. 3. Remove hub and drum. 4. Remove oil seal, inner bearing and retaining ring. 5. Remove outer bearing. 6. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Wheel Hub > Component Information > Service and Repair Wheel Hub: Service and Repair FRONT HUB/BEARING Fig. 5 Hub, knuckle & bearing components. REMOVE 1. Disconnect battery ground cable. 2. Raise and support vehicle, then remove brake caliper. 3. Remove cap from hub/disc assembly, Fig. 5. 4. Remove cotter pin, nut and washer. 5. Remove hub/disc from spindle. 6. Remove outer bearing, seal, inner bearing and cup. INSTALL 1. Reverse procedure to install. Note the following: a. Clean all components before installing. b. Apply an approved high temperature front wheel bearing grease to the spindle at the inner and outer bearing seat, shoulder and seal seat. Also finger apply a small amount of grease inboard of each bearing cup in the hub/disc assembly. Pressure pack the bearings with a grease machine or hand pack them. Ensure grease is worked thoroughly into the rollers, cone and cage. c. When installing inner bearing, apply an additional quantity of grease outboard of the inner bearing. d. Torque nut (12) 10-12 ft lbs while turning the wheel assembly forward by hand. Apply grease to the outboard side of the outer bearing. Adjust wheel bearings. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Suspension > Wheel Seal > Component Information > Service and Repair Wheel Seal: Service and Repair Fig. 5 Hub, knuckle & bearing components. REMOVE 1. Disconnect battery ground cable. 2. Raise and support vehicle, then remove brake caliper. 3. Remove cap from hub/disc assembly, Fig. 5. 4. Remove cotter pin, nut and washer. 5. Remove hub/disc from spindle. 6. Remove outer bearing, seal, inner bearing and cup. INSTALL 1. Reverse procedure to install. Note the following: a. Clean all components before installing. b. Apply an approved high temperature front wheel bearing grease to the spindle at the inner and outer bearing seat, shoulder and seal seat. Also finger apply a small amount of grease inboard of each bearing cup in the hub/disc assembly. Pressure pack the bearings with a grease machine or hand pack them. Ensure grease is worked thoroughly into the rollers, cone and cage. c. When installing inner bearing, apply an additional quantity of grease outboard of the inner bearing. d. Torque nut (12) 10-12 ft lbs while turning the wheel assembly forward by hand. Apply grease to the outboard side of the outer bearing. Adjust wheel bearings. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Vehicle Lifting > Component Information > Service and Repair Vehicle Lifting: Service and Repair Fig. 12 Vehicle Lift Points. Fig. 12 Vehicle Lift Points. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Wheels/Tires - Use of Nitrogen Gas in Tires Tires: Technical Service Bulletins Wheels/Tires - Use of Nitrogen Gas in Tires INFORMATION Bulletin No.: 05-03-10-020C Date: April 27, 2010 Subject: Use of Nitrogen Gas in Tires Models: 2011 and Prior GM Passenger Cars and Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 05-03-10-020B (Section 03 - Suspension). GM's Position on the Use of Nitrogen Gas in Tires General Motors does not oppose the use of purified nitrogen as an inflation gas for tires. We expect the theoretical benefits to be reduced in practical use due to the lack of an existing infrastructure to continuously facilitate inflating tires with nearly pure nitrogen. Even occasional inflation with compressed atmospheric air will negate many of the theoretical benefits. Given those theoretical benefits, practical limitations, and the robust design of GM original equipment TPC tires, the realized benefits to our customer of inflating their tires with purified nitrogen are expected to be minimal. The Promise of Nitrogen: Under Controlled Conditions Recently, nitrogen gas (for use in inflating tires) has become available to the general consumer through some retailers. The use of nitrogen gas to inflate tires is a technology used in automobile racing. The following benefits under controlled conditions are attributed to nitrogen gas and its unique properties: - A reduction in the expected loss of Tire Pressure over time. - A reduction in the variance of Tire Pressures with temperature changes due to reduction of water vapor concentration. - A reduction of long term rubber degradation due to a decrease in oxygen concentrations. Important These are obtainable performance improvements when relatively pure nitrogen gas is used to inflate tires under controlled conditions. The Promise of Nitrogen: Real World Use Nitrogen inflation can provide some benefit by reducing gas migration (pressure loss) at the molecular level through the tire structure. NHTSA (National Highway Traffic Safety Administration) has stated that the inflation pressure loss of tires can be up to 5% a month. Nitrogen molecules are larger than oxygen molecules and, therefore, are less prone to "seeping" through the tire casing. The actual obtainable benefits of nitrogen vary, based on the physical construction and the materials used in the manufacturing of the tire being inflated. Another potential benefit of nitrogen is the reduced oxidation of tire components. Research has demonstrated that oxygen consumed in the oxidation process of the tire primarily comes from the inflation media. Therefore, it is reasonable to assume that oxidation of tire components can be reduced if the tire is inflated with pure nitrogen. However, only very small amounts of oxygen are required to begin the normal oxidation process. Even slight contamination of the tire inflation gas with compressed atmospheric air during normal inflation pressure maintenance, may negate the benefits of using nitrogen. GM Tire Quality, Technology and Focus of Importance Since 1972, General Motors has designed tires under the TPC (Tire Performance Criteria) specification system, which includes specific requirements that ensure robust tire performance under normal usage. General Motors works with tire suppliers to design and manufacture original equipment tires for GM vehicles. The GM TPC addresses required performance with respect to both inflation pressure retention, and endurance properties for original equipment tires. The inflation pressure retention requirements address availability of oxygen and oxidation concerns, while endurance requirements ensure the mechanical structure of the tire has sufficient strength. This combination has provided our customers with tires that maintain their structural integrity throughout their useful treadlife under normal operating conditions. Regardless of the inflation media for tires (atmospheric air or nitrogen), inflation pressure maintenance of tires is critical for overall tire, and ultimately, vehicle performance. Maintaining the correct inflation pressure allows the tire to perform as intended by the vehicle manufacturer in many areas, including comfort, fuel economy, stopping distance, cornering, traction, treadwear, and noise. Since the load carrying capability of a tire is related to inflation pressure, proper inflation pressure maintenance is necessary for the tire to support the load imposed by the vehicle without excessive structural Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Wheels/Tires - Use of Nitrogen Gas in Tires > Page 9886 degradation. Important Regardless of the inflation media for tires (atmospheric air or nitrogen), inflation pressure maintenance of tires is critical for overall tire, and ultimately, vehicle performance. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 04-03-10-001F > Apr > 10 > Tires/Wheels - Tire Puncture Repair Procedures Tires: Technical Service Bulletins Tires/Wheels - Tire Puncture Repair Procedures INFORMATION Bulletin No.: 04-03-10-001F Date: April 27, 2010 Subject: Tire Puncture Repair Procedures For All Cars and Light Duty Trucks Models: 2011 and Prior GM Passenger Cars and Light Duty Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 04-03-10-001E (Section 03 - Suspension). This bulletin covers puncture repair procedures for passenger car and light duty truck radial tires in the tread area only. The tire manufacturer must be contacted for its individual repair policy and whether or not the speed rating is retained after repair. Caution - Tire changing can be dangerous and should be done by trained professionals using proper tools and procedures. Always read and understand any manufacturer's warnings contained in their customers literature or molded into the tire sidewall. - Serious eye and ear injury may result from not wearing adequate eye and ear protection while repairing tires. - NEVER inflate beyond 275 kPa (40 pounds) pressure to seat beads. Some run flat tires, such as the Goodyear Extended Mobility Tire (EMT) used on the Corvette, may require more than 275 kPa (40 psi) to seat the bead. In such a case, a tire safety cage must be used. Consult the tire manufacturer for its individual repair policy. - NEVER stand, lean or reach over the assembly during inflation. Repairable area on a radial tire. Important - NEVER repair tires worn to the tread indicators 1.59 mm (2/32") remaining depth). - NEVER repair tires with a tread puncture larger than 6.35 mm (1/4"). - NEVER substitute an inner tube for a permissible or non-permissible repair. - NEVER perform an outside-in tire repair (plug only, on the wheel). - Every tire must be removed from the wheel for proper inspection and repair. - Regardless of the type of repair used, the repair must seal the inner liner and fill the injury. - Consult with repair material supplier/manufacturer for repair unit application procedures and repair tools/repair material recommendations. Three basic steps for tire puncture repair: 1. Remove the tire from the wheel for inspection and repair. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 04-03-10-001F > Apr > 10 > Tires/Wheels - Tire Puncture Repair Procedures > Page 9892 2. Fill the injury (puncture) to keep moisture out. 3. Seal the inner liner with a repair unit to prevent air loss. External Inspection 1. Prior to demounting, inspect the tire surface, the valve and the wheel for the source of the leak by using a water and soap solution. Mark the injured area and totally deflate the tire by removing the valve core. 2. Demount the tire from the wheel and place the tire on a well-lighted spreader. Internal Inspection 1. Spread the beads and mark the puncture with a tire crayon. 2. Inspect the inner tire for any signs of internal damage. 3. Remove the puncturing object, noting the direction of the penetration. 4. Probe the injury with a blunt awl in order to determine the extent and direction of the injury. 5. Remove any loose foreign material from the injury. 6. Punctures exceeding 6.35 mm (1/4") should not be repaired. Cleaning 1. Clean the area around the puncture thoroughly with a proper liner cleaner, clean cloth and a scraper. This step serves to remove dirt and mold lubricants to insure proper adhesion and non-contamination of the buffing tool. 2. Refer to information on the product or manufacturer's Material Safety Data Sheet and follow guidelines for handling and disposal. Clean the Injury Channel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 04-03-10-001F > Apr > 10 > Tires/Wheels - Tire Puncture Repair Procedures > Page 9893 1. Use a proper hand reamer, carbide cutter or drill bit to ream the puncture channel from the inside of the tire in order to clean the injury. 2. Remove steel wires protruding above the liner surface to prevent damage to the repair unit. 3. Consult your repair material supplier for recommended reaming tool(s). Fill the Injury 1. It is necessary to fill the injury channel to provide back up for the repair unit and to prevent moisture from entering the tire fabric and steel wires. 2. (For combination repair/plug units skip this step.) Cement the injured channel and fill the injury from the inside of the tire with the repair plug per repair material manufacturer's recommendations. Without stretching the plug, cut the plug off just above the inside tire surface. 3. Consult your repair material supplier for proper repair material selection. Repair Unit Selection Important Do not install the repair unit in this step. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 04-03-10-001F > Apr > 10 > Tires/Wheels - Tire Puncture Repair Procedures > Page 9894 1. Center the repair unit over the injury as a reference and outline an area larger than the unit so that buffing will not remove the crayon marks. 2. Remove the repair unit. 3. DO NOT overlap previous or multiple repair units. 4. Consult your repair material supplier for proper repair unit selection. Buffing 1. To prevent contamination and preserve the outline, buff within the marked area thoroughly and evenly with a low speed buffing tool using a fine wire brush or gritted rasp. 2. Buff to a smooth velvet surface (RMA #1 or #2 buffed texture). 3. Use caution not to gouge the inner liner or expose casing fabric. 4. Remove any buffing dust with a vacuum cleaner. 5. Consult your repair material supplier for a proper buffing tool. Cementing Apply chemical cement according to the repair material manufacturer's procedures. Repair Unit Application Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 04-03-10-001F > Apr > 10 > Tires/Wheels - Tire Puncture Repair Procedures > Page 9895 1. The tire must be in the relaxed position when the repair unit is installed (Do not spread the beads excessively). Two-Piece Plug and Repair Units 1. If applicable, install the repair unit so that the alignment is correct. 2. Center the repair unit over the injury and stitch down thoroughly with the stitching tool, working from the center out. 3. Being careful not to stretch the plug material, cut the plug flush with the outer tread. Combination Repair/Plug Units 1. Pull the plug through the injury until the repair just reaches the liner. Stitch down thoroughly. 2. Follow the repair material manufacturer's recommendations for further installation instructions. 2. Consult your repair material supplier for the proper stitching tool. Safety Cage Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 04-03-10-001F > Apr > 10 > Tires/Wheels - Tire Puncture Repair Procedures > Page 9896 Some run flat tires, such as the Goodyear Extended Mobility Tire (EMT) used on the Corvette, may require more than 275 kPa (40 psi) to seat the bead. In such a case, a tire safety cage must be used. Consult the tire manufacturer for its individual repair policy. Final Inspection 1. After remounting and inflating the tire, check both beads, the repair and the valve with a water and soap solution in order to detect leaks. 2. If the tire continues to lose air, the tire must be demounted and reinspected. 3. Balance the tire and wheel assembly. Refer to Tire and Wheel Assembly Balancing - OFF Vehicle. For additional tire puncture repair information, contact: Rubber Manufacturers Association (RMA) Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 05-03-10-020C > Apr > 10 > Wheels/Tires - Use of Nitrogen Gas in Tires Tires: Technical Service Bulletins Wheels/Tires - Use of Nitrogen Gas in Tires INFORMATION Bulletin No.: 05-03-10-020C Date: April 27, 2010 Subject: Use of Nitrogen Gas in Tires Models: 2011 and Prior GM Passenger Cars and Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 05-03-10-020B (Section 03 - Suspension). GM's Position on the Use of Nitrogen Gas in Tires General Motors does not oppose the use of purified nitrogen as an inflation gas for tires. We expect the theoretical benefits to be reduced in practical use due to the lack of an existing infrastructure to continuously facilitate inflating tires with nearly pure nitrogen. Even occasional inflation with compressed atmospheric air will negate many of the theoretical benefits. Given those theoretical benefits, practical limitations, and the robust design of GM original equipment TPC tires, the realized benefits to our customer of inflating their tires with purified nitrogen are expected to be minimal. The Promise of Nitrogen: Under Controlled Conditions Recently, nitrogen gas (for use in inflating tires) has become available to the general consumer through some retailers. The use of nitrogen gas to inflate tires is a technology used in automobile racing. The following benefits under controlled conditions are attributed to nitrogen gas and its unique properties: - A reduction in the expected loss of Tire Pressure over time. - A reduction in the variance of Tire Pressures with temperature changes due to reduction of water vapor concentration. - A reduction of long term rubber degradation due to a decrease in oxygen concentrations. Important These are obtainable performance improvements when relatively pure nitrogen gas is used to inflate tires under controlled conditions. The Promise of Nitrogen: Real World Use Nitrogen inflation can provide some benefit by reducing gas migration (pressure loss) at the molecular level through the tire structure. NHTSA (National Highway Traffic Safety Administration) has stated that the inflation pressure loss of tires can be up to 5% a month. Nitrogen molecules are larger than oxygen molecules and, therefore, are less prone to "seeping" through the tire casing. The actual obtainable benefits of nitrogen vary, based on the physical construction and the materials used in the manufacturing of the tire being inflated. Another potential benefit of nitrogen is the reduced oxidation of tire components. Research has demonstrated that oxygen consumed in the oxidation process of the tire primarily comes from the inflation media. Therefore, it is reasonable to assume that oxidation of tire components can be reduced if the tire is inflated with pure nitrogen. However, only very small amounts of oxygen are required to begin the normal oxidation process. Even slight contamination of the tire inflation gas with compressed atmospheric air during normal inflation pressure maintenance, may negate the benefits of using nitrogen. GM Tire Quality, Technology and Focus of Importance Since 1972, General Motors has designed tires under the TPC (Tire Performance Criteria) specification system, which includes specific requirements that ensure robust tire performance under normal usage. General Motors works with tire suppliers to design and manufacture original equipment tires for GM vehicles. The GM TPC addresses required performance with respect to both inflation pressure retention, and endurance properties for original equipment tires. The inflation pressure retention requirements address availability of oxygen and oxidation concerns, while endurance requirements ensure the mechanical structure of the tire has sufficient strength. This combination has provided our customers with tires that maintain their structural integrity throughout their useful treadlife under normal operating conditions. Regardless of the inflation media for tires (atmospheric air or nitrogen), inflation pressure maintenance of tires is critical for overall tire, and ultimately, vehicle performance. Maintaining the correct inflation pressure allows the tire to perform as intended by the vehicle manufacturer in many areas, including comfort, fuel economy, stopping distance, cornering, traction, treadwear, and noise. Since the load carrying capability of a tire is related to inflation pressure, proper inflation pressure maintenance is necessary for the tire to support the load imposed by the vehicle without excessive structural Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 05-03-10-020C > Apr > 10 > Wheels/Tires - Use of Nitrogen Gas in Tires > Page 9901 degradation. Important Regardless of the inflation media for tires (atmospheric air or nitrogen), inflation pressure maintenance of tires is critical for overall tire, and ultimately, vehicle performance. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 00-00-90-002J > Jan > 09 > Tires - Correct Inflation Pressure Information Tires: Technical Service Bulletins Tires - Correct Inflation Pressure Information INFORMATION Bulletin No.: 00-00-90-002J Date: January 28, 2009 Subject: Information on Proper Tire Pressure Models: 2010 and Prior GM Passenger Cars and Light Duty Trucks (including Saturn) 2009 and Prior HUMMER H2, H3, H3T 2005-2009 Saab 9-7X Supercede: This bulletin is being revised to add model years and clarify additional information. Please discard Corporate Bulletin Number 00-00-90-002I (Section 00 - General Information). Important: ^ Adjustment of tire pressure for a customer with a Low Tire Pressure Monitor (TPM) light on and no codes in the TPM system is NOT a warrantable repair. Claims to simply adjust the tire pressure will be rejected. ^ ALL tires (including the spare tire) MUST be set to the recommended inflation pressure stated on the vehicle's tire placard (on driver's door) during the PRE-DELIVERY INSPECTION (PDI). Recommended inflation pressure is not the pressure printed on tire sidewall. ^ Tires may be over-inflated from the assembly plant due to the mounting process. ^ Generally a 5.6°C (10°F) temperature change will result in (is equivalent to) a 6.9 kPa (1 psi) tire pressure change. ^ 2008-2009 HUMMER H2 Only - The H2 comes standard with Light Truck "D" Load Range tires with a recommended cold inflation pressure of 289 kPa (42 psi). These tires will alert the driver to a low pressure situation at roughly 262 kPa (38 psi) due to a requirement in FMVSS 138 which specifies a Minimum Activation Pressure for each tire type. This creates a relatively narrow window of "usable" pressure values and the warning will be more sensitive to outside temperature changes during the colder months. As with other cold temperature/tire pressure issues, there is nothing wrong with the system itself. If a vehicle is brought in with this concern, check for tire damage and set all tires to the Recommended Cold Inflation Pressure shown on the vehicle placard. Accurate tire pressures ensure the safe handling and appropriate ride characteristics of GM cars and trucks. It is critical that the tire pressure be adjusted to the specifications on the vehicle¡C■s tire placard during PDI. Ride, handling and road noise concerns may be caused by improperly adjusted tire pressure. The first step in the diagnosis of these concerns is to verify that the tires are inflated to the correct pressures. The recommended tire inflation pressure is listed on the vehicle¡C■s tire placard. The tire placard is located on the driver¡C■s side front or rear door edge, center pillar, or the rear compartment lid. Tip ^ Generally a 5.6°C (10°F) temperature increase will result in (is equivalent to) a 6.9 kPa (1 psi) tire pressure increase. ^ The definition of a "cold" tire is one that has been sitting for at least 3 hours, or driven no more than 1.6 km (1 mi). ^ On extremely cold days, if the vehicle has been indoors, it may be necessary to compensate for the low external temperature by adding additional air to the tire during PDI. ^ During cold weather, the Tire Pressure Monitor (TPM) indicator light (a yellow horseshoe with an exclamation point) may illuminate. If this indicator turns off after the tires warm up (reach operating temperature), the tire pressure should be reset to placard pressure at the cold temperature. ^ The TPM system will work correctly with nitrogen in tires. ^ The TPM system is compatible with the GM Vehicle Care Tire Sealant but may not be with other commercially available sealants. Important: ^ Do not use the tire pressure indicated on the tire itself as a guide. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 00-00-90-002J > Jan > 09 > Tires - Correct Inflation Pressure Information > Page 9906 ^ Always inspect and adjust the pressure when the tires are cold. ^ Vehicles that have different pressures for the front and the rear need to be adjusted after tire rotation. Improper tire inflation may result in any or all of the following conditions: ^ Premature tire wear ^ Harsh ride ^ Excessive road noise ^ Poor handling ^ Reduced fuel economy ^ Low Tire Pressure Monitor (TPM) Light ON ^ Low Tire Pressure Message on the Drivers Information Center (DIC) Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 01-03-10-011 > Dec > 01 > Tires - Sidewall Damage Tires: Technical Service Bulletins Tires - Sidewall Damage File In Section: 03 Suspension Bulletin No.: 01-03-10-011 Date: December, 2001 INFORMATION Subject: Tire Sidewall Damage Models: 2002 and Prior Passenger Cars and Light Duty Trucks Inspection of a number of tires returned to the Warranty Parts Center and the various tire manufacturers has revealed gouges and/or abrasions that are located on the tire's outboard sidewall. Typically, these gouges and/or abrasions appear to be located near where the tire was marked for wheel balance weight installation at the vehicle assembly plant. It has been determined that this type of surface damage to the tire may be the result of dealers or owners using a high pressure power washer to remove wax/paint/ink marks from the tire sidewall. Do not use a high pressure power washer on tires. To remove any markings from the tire's sidewall, only use soap water and a scrub brush. This type of tire sidewall damage should not be considered as a warrantable condition. DISCLAIMER Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 00-03-10-003B > May > 01 > Tires - Bumper To Bumper Warranty Coverage Tires: Technical Service Bulletins Tires - Bumper To Bumper Warranty Coverage File In Section: 03 - Suspension Bulletin No.: 00-03-10-003B Date: May, 2001 WARRANTY ADMINISTRATION Subject: GM Tire Warranty for Bumper-to-Bumper Program Models: 1996-2001 Passenger Cars and Light Duty Trucks Attention: "GM of Canada" and "IPC" dealers are not authorized to utilize this service bulletin. This bulletin is being revised to include information on the new GM Global Tire Warranty & Claims (GTWC) website for preparing the GM Tire Requisition & Return Document for tires being replaced under the Bumper-to-Bumper New Vehicle Limited Warranty Program. Please discard Corporate Bulletin Number 00-03-10-003A (Section 03 - Suspension) Since the 1996 model year, original equipment manufactured (OEM) tires on all GM passenger cars and light duty trucks are covered under the Bumper-to-Bumper time and mileage provisions of the GM New Vehicle Limited Warranty. Saturn began such coverage with the 2001 model year. Tire warranty coverage allows the customer to have all warranty needs, including tires, addressed at one location - a GM dealership. Although GM dealers are not required to inventory tires to administer this warranty coverage, some dealers may choose to do so. What Is Covered Only OEM tires are covered against defects in material and workmanship. OEM tires will always have a Tire Performance Criteria (TPC) number molded on the sidewall near the tire size. (Exceptions: Prizm and some Tracker models do not use TPC tires, but are still covered.) Any replaced tire will continue to be covered for the remaining portion of the New Vehicle Warranty. Tires will be warranted without prorated charges for tread mileage. Following expiration of GM's coverage, tires may continue to be warranted, on a pro-rated basis, by the tire manufacturer. Review the tire manufacturer's booklet (included as part of the glove box material). What Is Not Covered ^ Non-original equipment tires (those without a TPC number molded on the sidewall except Prizm and Tracker) are not covered. ^ Normal tire wear and wear out is not covered. ^ Road hazard is not covered. This includes punctures, cuts, impact breaks, etc. Road hazard is covered by the tire manufacturer on sealant and EMT (run flat) tires. ^ Damage due to misuse, negligence, lack of maintenance, alteration, racing and vandalism is not covered. Global Tire Warranty & Claims Website Effective May 14, 2001, GM dealers will be required to use the Global Tire Warranty & Claims (GTWC) website to electronically initiate the Tire Requisition & Return Document needed to obtain replacement tires. All previous paper copy versions of this document should be discarded. The GTWC website is a secured, encrypted, password-protected tool designed to allow GM to collect and monitor data on tires being replaced on all GM vehicles, providing an early warning for any concerns. The website will provide a more efficient, faster and error-free procedure for preparing the GM Tire Requisition & Return Document. The electronic Tire Requisition & Return Document requires one form per tire, not one form per vehicle, as in the past. This web form is designed to automatically fill data fields and provides many drop-down menu selections to minimize user effort. It also has additional data requirements on types of adjustments and has a monitoring system for the return of tires to the tire manufacturer for inspection. GM dealers will need to print copies of the completed web form to get replacement tires from the local tire dealer and to return the removed tire(s) to the tire manufacturer for inspection. Once the removed tire has been returned and inspected, the tire manufacturer will also use the GTWC web system to complete the form initiated by the GM dealer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 00-03-10-003B > May > 01 > Tires - Bumper To Bumper Warranty Coverage > Page 9915 Initiating a Tire Requisition & Return Document Online Users may access the system using any PC with an Internet connection through the GM ACCESS hyperlink or preferably using a local Internet Service Provider (ISP). The minimum browser version required is Netscape 4.5 or Internet Explorer 4.0 or higher. The GM ACCESS server has an outdated web browser and cannot be used to access this website. Please use a client PC with the appropriate level of browser. 1. From a Microsoft Internet Explorer or Netscape, type in the web address: http://gtwc.gm.com. 2. IN the pop-up logon window, type your User ID (which is your Business Association Code) and your password (your initial password is the same as your User ID) and then click the OK button. 3. For security, each dealer is encouraged to change their password after they logon the first time. Click on "Change Password" from the upper right-hand menu bar and follow the instructions provided. Please note that User IDs and passwords are case sensitive. 4. From the "Create New Adjustment" screen, select your GM Dealer Code from the drop-down menu. 5. Proceed through the form, using the drop-down menus and "populate" buttons to auto-fill related data. 6. Help buttons are located at individual data fields and overall forms help and definitions are available at the top right of the screen. 7. From the bottom of the screen, you can "Save as Draft" to complete the form later or "Submit" the form if it is complete. 8. A confirmation screen will appear allowing you to print the form. Three copies of the form should be printed. One copy will be provided to the tire store to obtain a replacement tire. The second copy will be sent with the returned tire and the third copy should be retained. in the vehicle history file. In addition, an option to quickly create another form called "Next Tire Same Vehicle" is shown. 9. On the navigation menu bar across the top of the screen, "Edit" and "View" choices provide a way to get back to incomplete forms or view forms that have been submitted. A search mechanism is available to sort through forms by fields (date of form, repair order number, etc.). U.S. help Line for GTWC Website Users: 1-888-337-1010 Follow prompt 3: For GM ACCESS, DealerWorld and Other Internet Applications Obtaining New Tires 1. Determine the vehicle and tire eligibility based on the What Is Covered/What Is Not Covered portion of this bulletin. 2. A GM Tire Requisition and Return Document must be completed electronically on the website to obtain tires. Pressing the web form Submit" button does NOT order a new tire. GM dealers will need to print a copy of the completed web form to get the replacement tire from the local tire dealer. 3. New tires are to be obtained through the local tire dealer using a printed copy of the GM Tire Requisition and Return web form. A warranty replacement tire will be provided at no charge. Dealers are NOT to purchase warranty replacement tires. If a tire dealer is not convenient, call the tire manufacturer's toll-free phone number (listed later in this bulletin). Some tire companies will ship direct to the GM dealership. 4. New tires should be properly mounted, dynamically balanced and installed in the customer's vehicle. Proper balance weights and wheel nut torque procedures must be used. Returning Old Tires MOST tires replaced under the New Vehicle Limited Bumper-to-Bumper Warranty will be returned to the tire manufacturer. This is done using pre-addressed, prepaid UPS shipping labels. These labels can be obtained from Helm by calling 1-888-549-6152. Do NOT call UPS or the tire companies for these labels. There will be instances when the GM Warranty Parts Center (WPC) will request tires. Therefore, all replaced tires must be retained until receipt of claim payment. The WPC will request a tire(s) on the same day the credit memo is received at the GM dealership. If no WPC request is received, the dealer should return tires to the proper tire manufacturer. GM dealers are encouraged to submit warranty claims as soon as possible in order to alleviate storage of tires. Whether returned to the tire manufacturer or the WPC, a printed copy of the Tire Requisition and Return Document web form and the repair order must be placed in an envelope and securely taped to EACH tire being returned. A shipping label to the WPC or tire company must be attached to EACH tire being returned. Using a tire crayon, mark the tire to indicate the reason for replacement or location of the defect. Submitting a Warranty Claim Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 00-03-10-003B > May > 01 > Tires - Bumper To Bumper Warranty Coverage > Page 9916 1. The correct tire warranty labor code must be used for the brand of tire replaced. Choose the correct labor code from the list as shown. 2. The generic number 09592318 MUST be inserted on all tire claims in the "part number" field regardless of manufacturer to ensure correct processing. 3. A $25 administrative allowance per repair order MUST be inserted in the "parts amount" field. 4. Labor for mounting and balancing should be submitted. 5. Freight charges for tire returns are NOT to be submitted. Labor time to replace one tire, including mounting and balancing, is 0.6 hr. Each additional tire replaced is 0.4 hr. Important: For tire replacement because of transportation damage or incorrect parts, use labor code E0421 and submit as a transportation claim. Tire Company Assistance DISCLAIMER Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 70-05-01 > Sep > 97 > Tires - Replacement During Bumper to Bumper Warranty Technical Service Bulletin # 70-05-01 Date: 970901 Tires - Replacement During Bumper to Bumper Warranty File In Section: Warranty Administration Bulletin No.: 70-05-01 Date: September, 1997 WARRANTY ADMINISTRATION Subject: Tire Replacement During Bumper to Bumper Vehicle Warranty Models: All 1996 and Newer Passenger Cars and Light Duty Trucks and All 1995 Cadillac Models Recent reviews of Tire Warranty Claims, including the physical inspection of tires returned by dealers to the tire manufacturers inspection centers, has identified areas of warranty administration needing improvement. The purpose of this bulletin is to point out those problem areas, recommend corrective solutions and to list the sources of information which could be of assistance to dealers in the administration of the tire portion of the GM Bumper to Bumper Vehicle Warranty. There are a number of reasons that tires may require replacement. The following information identities those reasons and what actions, if any, should be taken. When tire(s) replacement is required during the GM Bumper to Bumper Vehicle Warranty, they are to be obtained from the appropriate local tire dealer. - Provide the local tire dealer with a properly completed photocopy of the GM Tire Requisition and Return Document, and the repair order. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 70-05-01 > Sep > 97 > Tires - Replacement During Bumper to Bumper Warranty > Page 9921 - If assistance in obtaining replacement tire(s) is needed, contact the Tire Manufacturer using their toll-free Assistance Numbers: Tire Manufacturer Assistance Numbers BRIDGESTONE and 1-800-356-4644 FIRESTONE GENERAL 1-800-847-3349 GOODYEAR 1-800-782-7949 MICHELIN 1-800-887-0662 UNIROYAL and B.F. GOODRICH 1-800-231-5893 Return of tire(s) adjusted under the GM Bumper to Bumper Vehicle Warranty to the appropriate tire manufacturer return centers. - UPS will pickup adjusted tire(s) for return to the tire manufacturers return center during their routine weekly dealer delivery schedule. Dealer will not be charged tire return freight charges by UPS. - Quantities of preprinted, prepaid UPS shipping labels to the tire manufacturer's return center are available at no-charge through GM Fulfillment 1-800-269-5100. - Dealer should have adjusted tire(s) ready for pickup by UPS for shipment to the appropriate tire manufacturers return center within two business days after tire replacement(s). Tires scheduled for return are to be received at the tire manufacturers return location within 30 days after acquisition of the new tire(s). Dealer failure to return the failed tire(s) within this prescribed time limit will result in automatic debit of warranty claim. Important: Only tires replaced under the GM Bumper to Bumper Vehicle Warranty are to be returned to the tire manufacturers return center. Tires adjusted under the GM Bumper to Bumper Vehicle Warranty, received at tire manufacturers return center, must include the following required paper work: Tire Requisition and Return Document - Complete the owner information, tire warranty data, replaced tire information, and reason for tire removal sections of the GM Tire Requisition and Return Document. Photocopy forms as needed from the GM Service Policies and Procedures Manual, Article 1.5, or Service Bulletins. Repair Order - Staple the completed GM Tire Requisition and Return Document to a photocopy of the R.O. and place in an envelope. Also include copies of any other paperwork received from the tire dealer. Attach the envelope to the adjusted tire using clear package tape wrapped completely around the body of the tire. Tire returns received with improper or no paperwork will be subject to debit. Cause of failure determined to be other than detects in materials and/or workmanship. - Normal tire wear is not covered by warranty. - Road hazard damage such as punctures, cuts, snags and breaks resulting from pothole impact, curb impact, or from other objects, is not covered (sealant tires do have road hazard coverage and are to be handled directly with the tire dealer or tire manufacturer). - Damage from improper inflation, spinning (as when stuck in mud or snow), tire chains, racing, improper mounting or dismounting, misuse, negligence, alteration, vandalism, or misapplication is not covered. - Dealer Claims for tires returned with no identifiable defects in material and workmanship will be subject to debit. The following sources of information are available to assist dealers with proper tire problem diagnosis, repair, Warranty Administration and Service Information. - Information contained in the Warranty and Owner Assistance Information Booklet under "What is" and "What is Not Covered". - GM Techline Tire Warranty Training Video and GM Techline Tire Warranty Procedures Booklet available through GM Training 1-800-393-4831. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 70-05-01 > Sep > 97 > Tires - Replacement During Bumper to Bumper Warranty > Page 9922 - Warranty Administration Bulletin Number 52-05-09, 60-05-01, and 60-05-02 dated October 1995, May 1996 and November 1996 respectively. - GM Service Policies and Procedures Manual, Articles 1.5.2E, and 1.5.12. - GM Service Manuals, Section 3E. - Vibration Diagnosis Training through GM Training Centers. - In-Dealership training programs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 600501 > Apr > 96 > Warranty - Tire Replacement Tires: Technical Service Bulletins Warranty - Tire Replacement File In Section: Warranty Administration Bulletin No.: 60-05-01 Date: April, 1996 WARRANTY ADMINISTRATION Subject: Tire Replacements Models: All Passenger Cars and Light Duty Trucks With bulletin number 52-05-09 dated October, 1995, GM announced the 1996 Tire Warranty Administration Program for all divisions. The purpose of this bulletin is to clarify the use and application of warranty labor operation numbers in conjunction with tire replacements. ALL 1996 GM PASSENGER CARS AND LIGHT DUTY TRUCKS AND 1995 CADILLAC TIRE REPLACEMENTS UNDER THE BUMPER-TO-BUMPER COVERAGE When replacing a defective OEM tire under the bumper-to-bumper warranty, dealer may submit a warranty claim for labor utilizing the appropriate GM labor operation as shown. These labor operations and times will be published in the April, 1996 edition of the GM Labor Time Guides. Important: In the event one or more tires are replaced under the bumper-to-bumper warranty, dealer is to submit $25 administrative allowance as a net item per repair order. Also, any sublet charges for mounting and balancing by the tire dealer are to be submitted as a net item. ALL MODEL YEAR GM PASSENGER CAR AND LIGHT DUTY TRUCK TIRE REPLACEMENT FOR REASONS OTHER THAN A DEFECTIVE TIRE The following claims submission practices continue to apply to all model year vehicles. When replacing a tire that failed because of a defect in material or workmanship of another warranted component, include associated costs (parts and labor) with the claim for replacement of that failed part/component. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > 600501 > Apr > 96 > Warranty - Tire Replacement > Page 9927 Dealer reimbursement for tires adjusted under vehicle warranty will be at dealer net cost of tires, and any mounting, balancing and freight charges not covered by the tire manufacturer, plus a 0.2 hour handling allowance on each tire replacement R.O. No warranty parts handling allowance applies. Important: This type of claim will require appropriate authorization. Tire failure due to road hazard damage should not be submitted to GM for reimbursement and is not included in the replacement guidelines contained in this bulletin. ALL TRANSMISSION CLAIMS FOR TIRE REPLACEMENT For tire replacement because of transportation damage or missing/incorrect parts, use labor operation number E0421 and submit as a transportation claim. Refer to your GM claims processing manual for complete claims submission details. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > Page 9928 Tires: Technical Service Bulletins Tires/Wheels - Tire Puncture Repair Procedures INFORMATION Bulletin No.: 04-03-10-001F Date: April 27, 2010 Subject: Tire Puncture Repair Procedures For All Cars and Light Duty Trucks Models: 2011 and Prior GM Passenger Cars and Light Duty Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 04-03-10-001E (Section 03 - Suspension). This bulletin covers puncture repair procedures for passenger car and light duty truck radial tires in the tread area only. The tire manufacturer must be contacted for its individual repair policy and whether or not the speed rating is retained after repair. Caution - Tire changing can be dangerous and should be done by trained professionals using proper tools and procedures. Always read and understand any manufacturer's warnings contained in their customers literature or molded into the tire sidewall. - Serious eye and ear injury may result from not wearing adequate eye and ear protection while repairing tires. - NEVER inflate beyond 275 kPa (40 pounds) pressure to seat beads. Some run flat tires, such as the Goodyear Extended Mobility Tire (EMT) used on the Corvette, may require more than 275 kPa (40 psi) to seat the bead. In such a case, a tire safety cage must be used. Consult the tire manufacturer for its individual repair policy. - NEVER stand, lean or reach over the assembly during inflation. Repairable area on a radial tire. Important - NEVER repair tires worn to the tread indicators 1.59 mm (2/32") remaining depth). - NEVER repair tires with a tread puncture larger than 6.35 mm (1/4"). - NEVER substitute an inner tube for a permissible or non-permissible repair. - NEVER perform an outside-in tire repair (plug only, on the wheel). - Every tire must be removed from the wheel for proper inspection and repair. - Regardless of the type of repair used, the repair must seal the inner liner and fill the injury. - Consult with repair material supplier/manufacturer for repair unit application procedures and repair tools/repair material recommendations. Three basic steps for tire puncture repair: 1. Remove the tire from the wheel for inspection and repair. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > Page 9929 2. Fill the injury (puncture) to keep moisture out. 3. Seal the inner liner with a repair unit to prevent air loss. External Inspection 1. Prior to demounting, inspect the tire surface, the valve and the wheel for the source of the leak by using a water and soap solution. Mark the injured area and totally deflate the tire by removing the valve core. 2. Demount the tire from the wheel and place the tire on a well-lighted spreader. Internal Inspection 1. Spread the beads and mark the puncture with a tire crayon. 2. Inspect the inner tire for any signs of internal damage. 3. Remove the puncturing object, noting the direction of the penetration. 4. Probe the injury with a blunt awl in order to determine the extent and direction of the injury. 5. Remove any loose foreign material from the injury. 6. Punctures exceeding 6.35 mm (1/4") should not be repaired. Cleaning 1. Clean the area around the puncture thoroughly with a proper liner cleaner, clean cloth and a scraper. This step serves to remove dirt and mold lubricants to insure proper adhesion and non-contamination of the buffing tool. 2. Refer to information on the product or manufacturer's Material Safety Data Sheet and follow guidelines for handling and disposal. Clean the Injury Channel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > Page 9930 1. Use a proper hand reamer, carbide cutter or drill bit to ream the puncture channel from the inside of the tire in order to clean the injury. 2. Remove steel wires protruding above the liner surface to prevent damage to the repair unit. 3. Consult your repair material supplier for recommended reaming tool(s). Fill the Injury 1. It is necessary to fill the injury channel to provide back up for the repair unit and to prevent moisture from entering the tire fabric and steel wires. 2. (For combination repair/plug units skip this step.) Cement the injured channel and fill the injury from the inside of the tire with the repair plug per repair material manufacturer's recommendations. Without stretching the plug, cut the plug off just above the inside tire surface. 3. Consult your repair material supplier for proper repair material selection. Repair Unit Selection Important Do not install the repair unit in this step. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > Page 9931 1. Center the repair unit over the injury as a reference and outline an area larger than the unit so that buffing will not remove the crayon marks. 2. Remove the repair unit. 3. DO NOT overlap previous or multiple repair units. 4. Consult your repair material supplier for proper repair unit selection. Buffing 1. To prevent contamination and preserve the outline, buff within the marked area thoroughly and evenly with a low speed buffing tool using a fine wire brush or gritted rasp. 2. Buff to a smooth velvet surface (RMA #1 or #2 buffed texture). 3. Use caution not to gouge the inner liner or expose casing fabric. 4. Remove any buffing dust with a vacuum cleaner. 5. Consult your repair material supplier for a proper buffing tool. Cementing Apply chemical cement according to the repair material manufacturer's procedures. Repair Unit Application Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > Page 9932 1. The tire must be in the relaxed position when the repair unit is installed (Do not spread the beads excessively). Two-Piece Plug and Repair Units 1. If applicable, install the repair unit so that the alignment is correct. 2. Center the repair unit over the injury and stitch down thoroughly with the stitching tool, working from the center out. 3. Being careful not to stretch the plug material, cut the plug flush with the outer tread. Combination Repair/Plug Units 1. Pull the plug through the injury until the repair just reaches the liner. Stitch down thoroughly. 2. Follow the repair material manufacturer's recommendations for further installation instructions. 2. Consult your repair material supplier for the proper stitching tool. Safety Cage Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > Page 9933 Some run flat tires, such as the Goodyear Extended Mobility Tire (EMT) used on the Corvette, may require more than 275 kPa (40 psi) to seat the bead. In such a case, a tire safety cage must be used. Consult the tire manufacturer for its individual repair policy. Final Inspection 1. After remounting and inflating the tire, check both beads, the repair and the valve with a water and soap solution in order to detect leaks. 2. If the tire continues to lose air, the tire must be demounted and reinspected. 3. Balance the tire and wheel assembly. Refer to Tire and Wheel Assembly Balancing - OFF Vehicle. For additional tire puncture repair information, contact: Rubber Manufacturers Association (RMA) Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > Page 9934 Tires: Technical Service Bulletins Tires - Correct Inflation Pressure Information INFORMATION Bulletin No.: 00-00-90-002J Date: January 28, 2009 Subject: Information on Proper Tire Pressure Models: 2010 and Prior GM Passenger Cars and Light Duty Trucks (including Saturn) 2009 and Prior HUMMER H2, H3, H3T 2005-2009 Saab 9-7X Supercede: This bulletin is being revised to add model years and clarify additional information. Please discard Corporate Bulletin Number 00-00-90-002I (Section 00 - General Information). Important: ^ Adjustment of tire pressure for a customer with a Low Tire Pressure Monitor (TPM) light on and no codes in the TPM system is NOT a warrantable repair. Claims to simply adjust the tire pressure will be rejected. ^ ALL tires (including the spare tire) MUST be set to the recommended inflation pressure stated on the vehicle's tire placard (on driver's door) during the PRE-DELIVERY INSPECTION (PDI). Recommended inflation pressure is not the pressure printed on tire sidewall. ^ Tires may be over-inflated from the assembly plant due to the mounting process. ^ Generally a 5.6°C (10°F) temperature change will result in (is equivalent to) a 6.9 kPa (1 psi) tire pressure change. ^ 2008-2009 HUMMER H2 Only - The H2 comes standard with Light Truck "D" Load Range tires with a recommended cold inflation pressure of 289 kPa (42 psi). These tires will alert the driver to a low pressure situation at roughly 262 kPa (38 psi) due to a requirement in FMVSS 138 which specifies a Minimum Activation Pressure for each tire type. This creates a relatively narrow window of "usable" pressure values and the warning will be more sensitive to outside temperature changes during the colder months. As with other cold temperature/tire pressure issues, there is nothing wrong with the system itself. If a vehicle is brought in with this concern, check for tire damage and set all tires to the Recommended Cold Inflation Pressure shown on the vehicle placard. Accurate tire pressures ensure the safe handling and appropriate ride characteristics of GM cars and trucks. It is critical that the tire pressure be adjusted to the specifications on the vehicle¡C■s tire placard during PDI. Ride, handling and road noise concerns may be caused by improperly adjusted tire pressure. The first step in the diagnosis of these concerns is to verify that the tires are inflated to the correct pressures. The recommended tire inflation pressure is listed on the vehicle¡C■s tire placard. The tire placard is located on the driver¡C■s side front or rear door edge, center pillar, or the rear compartment lid. Tip ^ Generally a 5.6°C (10°F) temperature increase will result in (is equivalent to) a 6.9 kPa (1 psi) tire pressure increase. ^ The definition of a "cold" tire is one that has been sitting for at least 3 hours, or driven no more than 1.6 km (1 mi). ^ On extremely cold days, if the vehicle has been indoors, it may be necessary to compensate for the low external temperature by adding additional air to the tire during PDI. ^ During cold weather, the Tire Pressure Monitor (TPM) indicator light (a yellow horseshoe with an exclamation point) may illuminate. If this indicator turns off after the tires warm up (reach operating temperature), the tire pressure should be reset to placard pressure at the cold temperature. ^ The TPM system will work correctly with nitrogen in tires. ^ The TPM system is compatible with the GM Vehicle Care Tire Sealant but may not be with other commercially available sealants. Important: ^ Do not use the tire pressure indicated on the tire itself as a guide. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > Page 9935 ^ Always inspect and adjust the pressure when the tires are cold. ^ Vehicles that have different pressures for the front and the rear need to be adjusted after tire rotation. Improper tire inflation may result in any or all of the following conditions: ^ Premature tire wear ^ Harsh ride ^ Excessive road noise ^ Poor handling ^ Reduced fuel economy ^ Low Tire Pressure Monitor (TPM) Light ON ^ Low Tire Pressure Message on the Drivers Information Center (DIC) Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Tires > Component Information > Technical Service Bulletins > Technical Service Bulletins for Tires: > Page 9936 Tires: Technical Service Bulletins Tires - Sidewall Damage File In Section: 03 Suspension Bulletin No.: 01-03-10-011 Date: December, 2001 INFORMATION Subject: Tire Sidewall Damage Models: 2002 and Prior Passenger Cars and Light Duty Trucks Inspection of a number of tires returned to the Warranty Parts Center and the various tire manufacturers has revealed gouges and/or abrasions that are located on the tire's outboard sidewall. Typically, these gouges and/or abrasions appear to be located near where the tire was marked for wheel balance weight installation at the vehicle assembly plant. It has been determined that this type of surface damage to the tire may be the result of dealers or owners using a high pressure power washer to remove wax/paint/ink marks from the tire sidewall. Do not use a high pressure power washer on tires. To remove any markings from the tire's sidewall, only use soap water and a scrub brush. This type of tire sidewall damage should not be considered as a warrantable condition. DISCLAIMER Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > Customer Interest: > 00-03-10-006F > May > 10 > Wheels/Tires - Tire Radial Force Variation (RFV) Wheels: Customer Interest Wheels/Tires - Tire Radial Force Variation (RFV) INFORMATION Bulletin No.: 00-03-10-006F Date: May 04, 2010 Subject: Information on Tire Radial Force Variation (RFV) Models: 2011 and Prior GM Passenger Cars and Light Duty Trucks 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X 2000-2005 Saturn L Series 2003-2007 Saturn ION Supercede: This bulletin is being revised to considerably expand the available information on Radial Force Variation (RFV) and should be reviewed in whole. Please discard Corporate Bulletin Number 00-03-10-006E (Section 03 - Suspension). Important - Before measuring tires on equipment such as the Hunter GSP9700, the vehicle MUST be driven a minimum of 16 km (10 mi) to ensure removal of any flat-spotting. Refer to Corporate Bulletin Number 03-03-10-007E - Tire/Wheel Characteristics of GM Original Equipment Tires. - Equipment such as the Hunter GSP9700 MUST be calibrated prior to measuring tire/wheel assemblies for each vehicle. The purpose of this bulletin is to provide guidance to GM dealers when using tire force variation measurement equipment, such as the Hunter GSP9700. This type of equipment can be a valuable tool in diagnosing vehicle ride concerns. The most common ride concern involving tire radial force variation is highway speed shake on smooth roads. Tire related smooth road highway speed shake can be caused by three conditions: imbalance, out of round and tire force variation. These three conditions are not necessarily related. All three conditions must be addressed. Imbalance is normally addressed first, because it is the simpler of the three to correct. Off-vehicle, two plane dynamic wheel balancers are readily available and can accurately correct any imbalance. Balancer calibration and maintenance, proper attachment of the wheel to the balancer, and proper balance weights, are all factors required for a quality balance. However, a perfectly balanced tire/wheel assembly can still be "oval shaped" and cause a vibration. Before balancing, perform the following procedures. Tire and Wheel Diagnosis 1. Set the tire pressure to the placard values. 2. With the vehicle raised, ensure the wheels are centered on the hub by loosening all wheel nuts and hand-tightening all nuts first by hand while shaking the wheel, then torque to specifications using a torque wrench, NOT a torque stick. 3. Visually inspect the tires and the wheels. Inspect for evidence of the following conditions and correct as necessary: - Missing balance weights - Bent rim flange - Irregular tire wear - Incomplete bead seating - Tire irregularities (including pressure settings) - Mud/ice build-up in wheel - Stones in the tire tread - Remove any aftermarket wheels and/or tires and restore vehicle to original condition prior to diagnosing a smooth road shake condition. 4. Road test the vehicle using the Electronic Vibration Analyzer (EVA) essential tool. Drive for a sufficient distance on a known, smooth road surface to duplicate the condition. Determine if the vehicle is sensitive to brake apply. If the brakes are applied lightly and the pulsation felt in the steering wheel increases, refer to the Brakes section of the service manual that deals with brake-induced pulsation. If you can start to hear the vibration as a low boom noise (in addition to feeling it), but cannot see it, the vehicle likely has a first order (one pulse per propshaft revolution) driveline vibration. Driveline first order vibrations are high enough in frequency that most humans can start to hear them at highway speeds, but are too high to be able to be easily seen. These issues can be caused by driveline imbalance or misalignment. If the vehicle exhibits this low boom and the booming pulses in-and-out on a regular basis (like a throbbing), chances are good that the vehicle could have driveline vibration. This type Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > Customer Interest: > 00-03-10-006F > May > 10 > Wheels/Tires - Tire Radial Force Variation (RFV) > Page 9945 of vibration is normally felt more in the "seat of the pants" than the steering wheel. 5. Next, record the Hertz (Hz) reading as displayed by the EVA onto the tire data worksheet found at the end of this bulletin. This should be done after a tire break-in period of at least 16 km (10 mi) at 72 km/h (45 mph) or greater, in order to eliminate any possible tire flat-spotting. This reading confirms what the vehicle vibration frequency is prior to vehicle service and documents the amount of improvement occurring as the result of the various steps taken to repair. Completing the Steering Wheel Shake Worksheet below is required. A copy of the completed worksheet must be saved with the R.O. and a copy included with any parts returned to the Warranty Parts Center for analysis. A reading of 35 to 50 Hz typically indicates a first order propshaft vibration. If this is the situation, refer to Corporate Bulletin Number 08-07-30-044D. Generally, a reading between 10 and 20 Hz indicates a tire/wheel vibration and if this is the reading obtained, continue using this bulletin. If the tire 1st order vibration goes away and stays away during this evaluation, the cause is likely tire flat-spotting. Tire flat-spotting vibration may come and go at any speed over 72 km/h (45 mph) during the first 10 minutes of operation, if vibration continues after 10 minutes of driving at speeds greater than 72 km/h (45 mph), tire flat-spotting can be ruled out as the cause for vibration. 6. If flat-spotting is the cause, provide the explanation that this has occurred due to the vehicle being parked for long periods of time and that the nature of the tire is to take a set. Refer to Corporate Bulletin Number 03-03-10-007E: Information on Tire/Wheel Characteristics (Vibration, Balance, Shake, Flat Spotting) of GM Original Equipment Tires. 7. If the road test indicates a shake/vibration exists, check the imbalance of each tire/wheel assembly on a known, calibrated, off-car dynamic balancer.Make sure the mounting surface of the wheel and the surface of the balancer are absolutely clean and free of debris. Be sure to chose the proper cone/collet for the wheel, and always use the pilot bore for centering. Never center the wheel using the hub-cap bore since it is not a precision machined surface. If any assembly calls for more than 1/4 ounce on either rim flange, remove all balance weights and rebalance to as close to zero as possible. If you can see the vibration (along with feeling it) in the steering wheel (driving straight without your hands on the wheel), it is very likely to be a tire/wheel first order (one pulse per revolution) disturbance. First order disturbances can be caused by imbalance as well as non-uniformities in tires, wheels or hubs. This first order frequency is too low for a human to hear, but if the amplitude is high enough, it can be seen. If a vibration or shake still exists after balancing, any out of round conditions, of the wheel, and force variation conditions of the tire, must be addressed. Equipment such as the Hunter GSP9700 can address both (it is also a wheel balancer). Tire radial force vibration (RFV) can be defined as the amount of stiffness variation the tire will produce in one revolution under a constant load. Radial force variation is what the vehicle feels because the load (weight) of the vehicle is always on the tires. Although free runout of tires (not under load) is not always a good indicator of a smooth ride, it is critical that total tire/wheel assembly runout be within specification. Equipment such as the Hunter GSP9700 loads the tire, similar to on the vehicle, and measures radial force variation of the tire/wheel assembly. Note that the wheel is affecting the tire's RFV measurement at this point. To isolate the wheel, its runout must be measured. This can be easily done on the Hunter, without the need to set up dial indicators. If the wheel meets the runout specification, the tire's RFV can then be addressed. After measuring the tire/wheel assembly under load, and the wheel alone, the machine then calculates (predicts) the radial force variation of the tire. However, because this is a prediction that can include mounting inaccuracies, and the load wheel is much smaller in diameter than used in tire production, this type of service equipment should NOT be used to audit new tires. Rather, it should be used as a service diagnostic tool to minimize radial force variation of the tire/wheel assembly. Equipment such as the Hunter GSP9700 does an excellent job of measuring wheel runout, and of finding the low point of the wheel (for runout) and the high point of the tire (for radial force variation). This allows the tire to be matched mounted to the wheel for lowest tire/wheel assembly force variation. The machine will simplify this process into easy steps. The following assembly radial force variation numbers should be used as a guide: When measuring RFV and match mounting tires perform the following steps. Measuring Wheel Runout and Assembly Radial Force Variation Important The completed worksheet at the end of this bulletin must be attached to the hard copy of the repair order. - Measure radial force variation and radial runout. - If a road force/balancing machine is used, record the radial force variation (RFV) on the worksheet at the end of this bulletin. It may be of benefit to have the lowest RFV assembly to the front left corner. If the machine is not available and the EVA data suggests there is an issue, swap the tire and wheel assemblies from the front to the back. Re-check on the EVA and if the problem still exists, test another vehicle to find tires that do not exhibit the same frequency and swap those tires onto the subject vehicle. - If a runout/balancing machine is used, record the radial runout of the tire/wheel assemblies on the worksheet at the end of this bulletin. If one or more of the tire/wheel assemblies are more than.040 in (1.02 mm), match mount the tire to the wheel to get below.040 in (1.02 mm). For sensitive customers, readings of 0.030 inch (0.76 mm) or less are preferable, it may also be of benefit to have the lowest runout assembly to the front left corner. If the machine is not available and the EVA data suggests there is an issue, swap the tire and wheel assemblies from the front to the back. Re-check on the EVA and if the problem still exists, test another vehicle to find tires that do not exhibit the same frequency and swap those tires Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > Customer Interest: > 00-03-10-006F > May > 10 > Wheels/Tires - Tire Radial Force Variation (RFV) > Page 9946 onto the subject vehicle. - After match mounting, the tire/wheel assembly must be rebalanced. If match mounting tires to in-spec wheels produces assembly values higher than these, tire replacement may be necessary. Replacing tires at lower values will probably mean good tires are being condemned. Because tires can sometimes become temporarily flat-spotted, which will affect force variation, it is important that the vehicle be driven at least 16 km (10 mi) prior to measuring. Tire pressure must also be adjusted to the usage pressure on the vehicle's tire placard prior to measuring. Most GM vehicles will tolerate radial force variation up to these levels. However, some vehicles are more sensitive, and may require lower levels. Also, there are other tire parameters that equipment such as the Hunter GSP9700 cannot measure that may be a factor. In such cases, TAC should be contacted for further instructions. Important - When mounting a GM wheel to a wheel balancer/force variation machine, always use the wheel's center pilot hole. This is the primary centering mechanism on all GM wheels; the bolt holes are secondary. Usually a back cone method to the machine should be used. For added accuracy and repeatability, a flange plate should be used to clamp the wheel onto the cone and machine. This system is offered by all balancer manufacturers in GM's dealer program. - Any type of service equipment that removes tread rubber by grinding, buffing or truing is NOT recommended, and may void the tire warranty. However, tires may have been ground by the tire company as part of their tire manufacturing process. This is a legitimate procedure. Steering Wheel Shake Worksheet When diagnosing vibration concerns, use the following worksheet in conjunction with the appropriate Vibration Analysis-Road testing procedure in the Vibration Correction sub-section in SI. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > Customer Interest: > 00-03-10-006F > May > 10 > Wheels/Tires - Tire Radial Force Variation (RFV) > Page 9947 Refer to the appropriate section of SI for specifications and repair procedures that are related to the vibration concern. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > Customer Interest: > 05-03-10-003F > Apr > 10 > Tires/Wheels - Low Tire/Leaking Cast Aluminum Wheels Wheels: Customer Interest Tires/Wheels - Low Tire/Leaking Cast Aluminum Wheels TECHNICAL Bulletin No.: 05-03-10-003F Date: April 27, 2010 Subject: Low Tire Pressure, Leaking Cast Aluminum Wheels (Repair with Adhesive Sealant) Models: 2011 and Prior GM Passenger Cars and Light Duty Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X with Cast Aluminum Wheels Supercede: This bulletin is being revised to update the model years and the bulletin reference information. Please discard Corporate Bulletin Number 05-03-10-003E (Section 03 - Suspension). Condition Some customers may comment on a low tire pressure condition. Diagnosis of the low tire pressure condition indicates an air leak through the cast aluminum wheel. Cause Porosity in the cast aluminum wheel may be the cause. Notice This bulletin specifically addresses issues related to the wheel casting that may result in an air leak. For issues related to corrosion of the wheel in service, please refer to Corporate Bulletin Number 08-03-10-006C - Tire Slowly Goes Flat, Tire Air Loss, Low Tire Pressure Warning Light Illuminated, Aluminum Wheel Bead Seat Corrosion (Clean and Resurface Wheel Bead Seat). Correction 1. Remove the tire and wheel assembly from the vehicle. Refer to the appropriate service procedure in SI. 2. Locate the leaking area by inflating the tire to 276 kPa (40 psi) and dipping the tire/wheel assembly in a water bath, or use a spray bottle with soap and water to locate the specific leak location. Important - If the porosity leak is located in the bead area of the aluminum rim (where the tire meets the rim), the wheel should be replaced. - If two or more leaks are located on one wheel, the wheel should be replaced. 3. If air bubbles are observed, mark the location. - If the leak location is on the tire/rubber area, refer to Corporate Bulletin Number 04-03-10-001F Tire Puncture Repair Procedures for All Cars and Light Duty Trucks. - If the leak is located on the aluminum wheel area, continue with the next step. 4. Inscribe a mark on the tire at the valve stem in order to indicate the orientation of the tire to the wheel. 5. Dismount the tire from the wheel. Refer to Tire Mounting and Dismounting. 6. Remove the tire pressure sensor. Refer to Tire Pressure Sensor removal procedure in SI. 7. Scuff the INSIDE rim surface at the leak area with #80 grit paper and clean the area with general purpose cleaner, such as 3M(R) General Purpose Adhesive Cleaner, P/N 08984, or equivalent. 8. Apply a 3 mm (0.12 in) thick layer of Silicone - Adhesive/Sealant, P/N 12378478 (in Canada, use 88900041), or equivalent, to the leak area. 9. Allow for the adhesive/sealant to dry. Notice Caution must be used when mounting the tire so as not to damage the sealer. Damaging the repair area may result in an air leak. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > Customer Interest: > 05-03-10-003F > Apr > 10 > Tires/Wheels - Low Tire/Leaking Cast Aluminum Wheels > Page 9952 10. Align the inscribed mark on the tire with the valve stem on the wheel. 11. Reinstall the Tire Pressure Sensor. Refer to Tire Pressure Sensor installation procedure in SI. 12. Mount the tire on the wheel. Refer to Tire Mounting and Dismounting. 13. Pressurize the tire to 276 kPa (40 psi) and inspect for leaks. 14. Adjust tire pressure to meet the placard specification. 15. Balance the tire/wheel assembly. Refer to Tire and Wheel Assembly Balancing - Off-Vehicle. 16. Install the tire and wheel assembly onto the vehicle. Refer to the appropriate service procedure in SI. Parts Information Warranty Information (excluding Saab U.S. Models) Important The Silicone - Adhesive/Sealant comes in a case quantity of six. ONLY charge warranty one tube of adhesive/sealant per wheel repair. For vehicles repaired under warranty, use: One leak repair per wheel. Warranty Information (Saab U.S. Models) For vehicles repaired under warranty, use the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 00-03-10-002F > Apr > 11 > Wheels - Chrome Wheel Staining/Pitting/Corrosion Wheels: All Technical Service Bulletins Wheels - Chrome Wheel Staining/Pitting/Corrosion INFORMATION Bulletin No.: 00-03-10-002F Date: April 21, 2011 Subject: Chemical Staining, Pitting, Corrosion and/or Spotted Appearance of Chromed Aluminum Wheels Models: 2012 and Prior GM Cars and Trucks Supercede: This bulletin is being revised to update model years, suggest additional restorative products and add additional corrosion information. Please discard Corporate Bulletin Number 00-03-10-002E (Section 03 - Suspension). Important You may give a copy of this bulletin to the customer. What is Chemical Staining of Chrome Wheels? Figure 1 Chemical staining in most cases results from acid based cleaners (refer to Figure 1 for an example). These stains are frequently milky, black, or greenish in appearance. They result from using cleaning solutions that contain acids on chrome wheels. Soap and water is usually sufficient to clean wheels. If the customer insists on using a wheel cleaner they should only use one that specifically states that it is safe for chromed wheels and does not contain anything in the following list. (Dealers should also survey any products they use during prep or normal cleaning of stock units for these chemicals.) - Ammonium Bifluoride (fluoride source for dissolution of chrome) - Hydrofluoric Acid (directly dissolves chrome) - Hydrochloric Acid (directly dissolves chrome) - Sodium Dodecylbenzenesulfonic Acid - Sulfamic Acid - Phosphoric Acid - Hydroxyacetic Acid Notice Many wheel cleaner instructions advise to take care to avoid contact with painted surfaces. Most customers think of painted surfaces as the fenders, quarter panels and other exterior sheet metal. Many vehicles have painted brake calipers. Acidic wheel cleaners may craze, crack, or discolor the paint on the brake calipers. Damage from wheel cleaners is not covered under the vehicle new car warranty. Soap and water applied with a soft brush is usually all that is required to clean the calipers. Whenever any wheel cleaner is used, it must be THOROUGHLY rinsed off of the wheel with clean, clear water. Special care must be taken to rinse under the hub cap, balance weights, wheel nuts, lug nut caps, between the wheel cladding and off the back side of the wheel. Wheels returned to the Warranty Parts Center (WPC) that exhibit damage from wheel cleaners most often have the damage around and under the wheel weight where the cleaner was incompletely flushed away. Notice Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 00-03-10-002F > Apr > 11 > Wheels - Chrome Wheel Staining/Pitting/Corrosion > Page 9958 Do not use cleaning solutions that contain hydrofluoric, oxalic and most other acids on chrome wheels (or any wheels). If the customer is unsure of the chemical make-up of a particular wheel cleaner, it should be avoided. For wheels showing signs of milky staining from acidic cleaners, refer to Customer Assistance and Instructions below. Warranty of Stained Chrome Wheels Stained wheels are not warrantable. Most acid based cleaners will permanently stain chrome wheels. Follow-up with dealers has confirmed that such cleaners were used on wheels that were returned to the Warranty Parts Center (WPC). Any stained wheels received by the WPC will be charged back to the dealership. To assist the customer, refer to Customer Assistance and Instructions below. Pitting or Spotted Appearance of Chrome Wheels Figure 2 A second type or staining or finish disturbance may result from road chemicals, such as calcium chloride used for dust control of unpaved roads. The staining will look like small pitting (refer to Figure 2). This staining will usually be on the leading edges of each wheel spoke, but may be uniformly distributed. If a vehicle must be operated under such conditions, the chrome wheels should be washed with mild soap and water and thoroughly rinsed as soon as conveniently possible. Important Road chemicals, such as calcium chloride used for dust control of unpaved roads, can also stain chrome wheels. The staining will look like small pitting. This staining will usually be on the leading edges of each wheel spoke. This is explained by the vehicle traveling in the forward direction while being splashed by the road chemical. If a vehicle must be operated under such conditions, the chrome wheels should be washed with mild soap and water and thoroughly rinsed as soon as conveniently possible. Warranty of Pitted or Spotted Chrome Wheels Wheels returned with pitting or spotting as a result of road chemicals may be replaced one time. Damage resulting from contact with these applied road chemicals is corrosive to the wheels finish and may cause damage if the wheels are not kept clean. Important Notify the customer that this is a one time replacement. Please stress to the customer the vital importance of keeping the wheels clean if they are operating the vehicle in an area that applies calcium chloride or other dust controlling chemicals! "GM of Canada" dealers require prior approval by the District Manager - Customer Care and Service Process (DM-CCSP). "Stardust" Corrosion of Chrome Wheels Figure 3 A third type of finish disturbance results from prolonged exposure to brake dust and resultant penetration of brake dust through the chrome. As brakes are applied hot particles of brake material are thrown off and tend to be forced through the leading edge of the wheel spoke windows by airflow. These Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 00-03-10-002F > Apr > 11 > Wheels - Chrome Wheel Staining/Pitting/Corrosion > Page 9959 hot particles embed themselves in the chrome layer and create a small pit. If the material is allowed to sit on the wheel while it is exposed to moisture or salt, it will corrode the wheel beneath the chrome leaving a pit or small blister in the chrome. Heavy brake dust build-up should be removed from wheels by using GM Chrome Cleaner and Polish, P/N 1050173 (in Canada use 10953013). For moderate cleaning, light brake dust build-up or water spots use GM Swirl Remover Polish, P/N 12377965 (in Canada, use Meguiars Plast-X(TM) Clear Plastic Cleaner and Polish #G12310C**). After cleaning, the wheel should be waxed using GM Cleaner Wax, P/N 12377966 (in Canada, use Meguiars Cleaner Wax #M0616C**), which will help protect the wheel from brake dust and reduce adhesion of any brake dust that gets on the wheel surface. For general maintenance cleaning, PEEK Metal Polish† may be used. It will clean and shine the chrome and leave behind a wax coating that may help protect the finish. Warranty of Stardust Corroded Chrome Wheels Wheels returned with pitting or spotting as a result of neglect and brake dust build-up may be replaced one time. Important Notify the customer that this is a one time replacement. Please stress to the customer the vital importance of keeping the wheels clean and free of prolonged exposure to brake dust build-up. "GM of Canada" dealers require prior approval by the District Manager - Customer Care and Service Process (DM-CCSP). Customer Assistance and Instructions GM has looked for ways customers may improve the appearance of wheels damaged by acidic cleaners. The following product and procedure has been found to dramatically improve the appearance of stained wheels. For wheels that have milky stains caused by acidic cleaners try the following: Notice THE 3M CHROME AND METAL POLISH REQUIRED FOR THIS PROCEDURE IS AN EXTREMELY AGGRESSIVE POLISH/CLEANER. THE WHEELS MUST BE CLEANED BEFORE APPLICATION TO AVOID SCRATCHING THE WHEEL SURFACE. THIS PRODUCT WILL REDUCE THE THICKNESS OF THE CHROME PLATING ON THE WHEEL AND IF USED INCORRECTLY OR EXCESSIVELY MAY REMOVE THE CHROME PLATING ALL TOGETHER, EXPOSING A LESS BRIGHT AND BRASSY COLORED SUB-LAYER. FOLLOW INSTRUCTIONS EXACTLY. 1. Wash the wheels with vigorously with soap and water. This step will clean and may reduce wheel staining. Flood all areas of the wheel with water to rinse. 2. Dry the wheels completely. Notice Begin with a small section of the wheel and with light pressure buff off polish and examine results. ONLY apply and rub with sufficient force and time to remove enough staining that you are satisfied with the results. Some wheels may be stained to the extent that you may only achieve a 50% improvement while others may be able to be restored to the original lustre. IN ALL CASES, only apply until the results are satisfactory. 3. Apply 3M Chrome and Metal Polish #39527* with a clean terry cloth towel. As you apply the polish, the staining will be diminished. 4. When dry, buff off the polish with a clean portion of the towel. 5. Repeat application of the 3M Chrome and Metal Polish until satisfied with the results. If continued applications fail to improve the appearance further discontinue use. This procedure will improve the appearance of the wheels and may, with repeated applications, restore the finish dramatically. For wheels that exhibit spotting from road chemicals the above procedure may marginally improve the condition but will not restore the finish or remove the pitting. In this type of staining the wheel finish has actually been removed in spots and no manner of cleaning will restore the finish. †*We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Parts Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 00-03-10-002F > Apr > 11 > Wheels - Chrome Wheel Staining/Pitting/Corrosion > Page 9960 *This product is currently available from 3M. To obtain information for your local retail location please call 3M at 1-888-364-3577. **This product is currently available from Meguiars (Canada). To obtain information for your local retail location please call Meguiars at 1-800-347-5700 or at www.meguiarscanada.com. ^ This product is currently available from Tri-Peek International. To obtain information for your local retail location please call Tri-Peek at 1-877-615-4272 or at www.tripeek.com. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 99-08-51-007E > Mar > 11 > Wheels/Tires Refinishing Aluminum Wheels Wheels: All Technical Service Bulletins Wheels/Tires - Refinishing Aluminum Wheels INFORMATION Bulletin No.: 99-08-51-007E Date: March 17, 2011 Subject: Refinishing Aluminum Wheels Models: 2012 and Prior GM Passenger Cars and Trucks Supercede: This bulletin is being revised to add additional model years. Please discard Corporate Bulletin Number 99-08-51-007D (Section 08 - Body and Accessories). This bulletin updates General Motor's position on refinishing aluminum wheels. GM does not endorse any repairs that involve welding, bending, straightening or re-machining. Only cosmetic refinishing of the wheel's coatings, using recommended procedures, is allowed. Evaluating Damage In evaluating damage, it is the GM Dealer's responsibility to inspect the wheel for corrosion, scrapes, gouges, etc. The Dealer must insure that such damage is not deeper than what can be sanded or polished off. The wheel must be inspected for cracks. If cracks are found, discard the wheel. Any wheels with bent rim flanges must not be repaired or refinished. Wheels that have been refinished by an outside company must be returned to the same vehicle. The Dealer must record the wheel ID stamp or the cast date on the wheel in order to assure this requirement. Refer to Refinisher's Responsibility - Outside Company later in this bulletin. Aluminum Wheel Refinishing Recommendations - Chrome-plated aluminum wheels Re-plating these wheels is not recommended. - Polished aluminum wheels These wheels have a polyester or acrylic clearcoat on them. If the clearcoat is damaged, refinishing is possible. However, the required refinishing process cannot be performed in the dealer environment. Refer to Refinisher's Responsibility - Outside Company later in this bulletin. - Painted aluminum wheels These wheels are painted using a primer, color coat, and clearcoat procedure. If the paint is damaged, refinishing is possible. As with polished wheels, all original coatings must be removed first. Media blasting is recommended. Refer to GM Aluminum Refinishing Bulletin #53-17-03A for the re-painting of this type of wheel. - Bright, machined aluminum wheels These wheels have a polyester or acrylic clearcoat on them. In some cases, the recessed "pocket" areas of the wheel may be painted. Surface refinishing is possible. The wheel must be totally stripped by media blasting or other suitable means. The wheel should be resurfaced by using a sanding process rather than a machining process. This allows the least amount of material to be removed. Important Do not use any re-machining process that removes aluminum. This could affect the dimensions and function of the wheel. Painting is an option to re-clearcoating polished and bright machined aluminum wheels. Paint will better mask any surface imperfections and is somewhat more durable than clearcoat alone. GM recommends using Corsican SILVER WAEQ9283 for a fine "aluminum-like" look or Sparkle SILVER WA9967 for a very bright look. As an option, the body color may also be used. When using any of the painting options, it is recommended that all four wheels be refinished in order to maintain color uniformity. Refer to GM Aluminum Refinishing Bulletin #53-17-03A for specific procedures and product recommendations. Refinisher's Responsibility - Outside Company Important Some outside companies are offering wheel refinishing services. Such refinished wheels will be permanently marked by the refinisher and are warranted by the refinisher. Any process that re-machines or otherwise re-manufactures the wheel should not be used. A refinisher's responsibility includes inspecting for cracks using the Zyglo system or the equivalent. Any cracked wheels must not be refinished. No welding, hammering or reforming of any kind is allowed. The wheel ID must be recorded and follow the wheel throughout the process in order to assure that the same wheel is returned. A plastic media blast may be used for clean up of the wheel. Hand and/or lathe sanding of the machined surface and the wheel window is allowed. Material removal, though, must be kept to a minimum. Re-machining of the wheel is not allowed. Paint and/or clear coat must not be present on the following surfaces: the nut chamfers, the wheel mounting surfaces and the wheel pilot hole. The refinisher must permanently ID stamp the wheel and warrant the painted/clearcoated surfaces for a minimum of one year or the remainder of the new vehicle warranty, whichever is Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 99-08-51-007E > Mar > 11 > Wheels/Tires Refinishing Aluminum Wheels > Page 9965 longer. Important Whenever a wheel is refinished, the mounting surface and the wheel nut contact surfaces must not be painted or clearcoated. Coating these surfaces could affect the wheel nut torque. When re-mounting a tire on an aluminum wheel, coated balance weights must be used in order to reduce the chance of future cosmetic damage. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 06-03-10-010A > Jun > 10 > Wheels - Changing Procedures/Precautions Wheels: All Technical Service Bulletins Wheels - Changing Procedures/Precautions INFORMATION Bulletin No.: 06-03-10-010A Date: June 09, 2010 Subject: Information on Proper Wheel Changing Procedures and Cautions Models: 2011 and Prior GM Passenger Cars and Trucks 2010 and Prior HUMMER Models 2005-2009 Saab 9-7X 2005-2009 Saturn Vehicles Attention: Complete wheel changing instructions for each vehicle line can be found under Tire and Wheel Removal and Installation in Service Information (SI). This bulletin is intended to quickly review and reinforce simple but vital procedures to reduce the possibility of achieving low torque during wheel installation. Always refer to SI for wheel lug nut torque specifications and complete jacking instructions for safe wheel changing. Supercede: This bulletin is being revised to include the 2011 model year and update the available special tool list. Please discard Corporate Bulletin Number 06-03-10-010 (Section 03 Suspension). Frequency of Wheel Changes - Marketplace Driven Just a few years ago, the increasing longevity of tires along with greater resistance to punctures had greatly reduced the number of times wheels were removed to basically required tire rotation intervals. Today with the booming business in accessory wheels/special application tires (such as winter tires), consumers are having tire/wheel assemblies removed - replaced - or installed more than ever. With this increased activity, it opens up more of a chance for error on the part of the technician. This bulletin will review a few of the common concerns and mistakes to make yourself aware of. Proper Servicing Starts With the Right Tools The following tools have been made available to assist in proper wheel and tire removal and installation. - J 41013 Rotor Resurfacing Kit (or equivalent) - J 42450-A Wheel Hub Resurfacing Kit (or equivalent) Corroded Surfaces One area of concern is corrosion on the mating surfaces of the wheel to the hub on the vehicle. Excessive corrosion, dirt, rust or debris built up on these surfaces can mimic a properly tightened wheel in the service stall. Once the vehicle is driven, the debris may loosen, grind up or be washed away from water splash. This action may result in clearance at the mating surface of the wheel and an under-torqued condition. Caution Before installing a wheel, remove any buildup on the wheel mounting surface and brake drum or brake disc mounting surface. Installing wheels with poor metal-to-metal contact at the mounting surfaces can cause wheel nuts to loosen. This may cause a wheel to come off when the vehicle is moving, possibly resulting in a loss of control or personal injury. Whenever you remove the tire/wheel assemblies, you must inspect the mating surfaces. If corrosion is found, you should remove the debris with a die grinder equipped with a fine sanding pad, wire brush or cleaning disc. Just remove enough material to assure a clean, smooth mating surface. The J 41013 (or equivalent) can be used to clean the following surfaces: - The hub mounting surface - The brake rotor mounting surface - The wheel mounting surface Use the J 42450-A (or equivalent) to clean around the base of the studs and the hub. Lubricants, Grease and Fluids Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 06-03-10-010A > Jun > 10 > Wheels - Changing Procedures/Precautions > Page 9970 Some customers may use penetrating oils, grease or other lubricants on wheel studs to aid in removal or installation. Always use a suitable cleaner/solvent to remove these lubricants prior to installing the wheel and tire assemblies. Lubricants left on the wheel studs may cause improper readings of wheel nut torque. Always install wheels to clean, dry wheel studs ONLY. Notice Lubricants left on the wheel studs or vertical mounting surfaces between the wheel and the rotor or drum may cause the wheel to work itself loose after the vehicle is driven. Always install wheels to clean, dry wheel studs and surfaces ONLY. Beginning with 2011 model year vehicles, put a light coating of grease, GM P/N 1051344 (in Canada, P/N 9930370), on the inner surface of the wheel pilot hole to prevent wheel seizure to the axle or bearing hub. Wheel Stud and Lug Nut Damage Always inspect the wheel studs and lug nuts for signs of damage from crossthreading or abuse. You should never have to force wheel nuts down the stud. Lug nuts that are damaged may not retain properly, yet give the impression of fully tightening. Always inspect and replace any component suspected of damage. Tip Always start wheel nuts by hand! Be certain that all wheel nut threads have been engaged BEFORE tightening the nut. Important If the vehicle has directional tread tires, verify the directional arrow on the outboard side of the tire is pointing in the direction of forward rotation. Wheel Nut Tightening and Torque Improper wheel nut tightening can lead to brake pulsation and rotor damage. In order to avoid additional brake repairs, evenly tighten the wheel nuts to the proper torque specification as shown for each vehicle in SI. Always observe the proper wheel nut tightening sequence as shown below in order to avoid trapping the wheel on the wheel stud threads or clamping the wheel slightly off center resulting in vibration. The Most Important Service You Provide While the above information is well known, and wheel removal so common, technicians run the risk of becoming complacent on this very important Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 06-03-10-010A > Jun > 10 > Wheels - Changing Procedures/Precautions > Page 9971 service operation. A simple distraction or time constraint that rushes the job may result in personal injury if the greatest of care is not exercised. Make it a habit to double check your work and to always side with caution when installing wheels. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 00-03-10-006F > May > 10 > Wheels/Tires - Tire Radial Force Variation (RFV) Wheels: All Technical Service Bulletins Wheels/Tires - Tire Radial Force Variation (RFV) INFORMATION Bulletin No.: 00-03-10-006F Date: May 04, 2010 Subject: Information on Tire Radial Force Variation (RFV) Models: 2011 and Prior GM Passenger Cars and Light Duty Trucks 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X 2000-2005 Saturn L Series 2003-2007 Saturn ION Supercede: This bulletin is being revised to considerably expand the available information on Radial Force Variation (RFV) and should be reviewed in whole. Please discard Corporate Bulletin Number 00-03-10-006E (Section 03 - Suspension). Important - Before measuring tires on equipment such as the Hunter GSP9700, the vehicle MUST be driven a minimum of 16 km (10 mi) to ensure removal of any flat-spotting. Refer to Corporate Bulletin Number 03-03-10-007E - Tire/Wheel Characteristics of GM Original Equipment Tires. - Equipment such as the Hunter GSP9700 MUST be calibrated prior to measuring tire/wheel assemblies for each vehicle. The purpose of this bulletin is to provide guidance to GM dealers when using tire force variation measurement equipment, such as the Hunter GSP9700. This type of equipment can be a valuable tool in diagnosing vehicle ride concerns. The most common ride concern involving tire radial force variation is highway speed shake on smooth roads. Tire related smooth road highway speed shake can be caused by three conditions: imbalance, out of round and tire force variation. These three conditions are not necessarily related. All three conditions must be addressed. Imbalance is normally addressed first, because it is the simpler of the three to correct. Off-vehicle, two plane dynamic wheel balancers are readily available and can accurately correct any imbalance. Balancer calibration and maintenance, proper attachment of the wheel to the balancer, and proper balance weights, are all factors required for a quality balance. However, a perfectly balanced tire/wheel assembly can still be "oval shaped" and cause a vibration. Before balancing, perform the following procedures. Tire and Wheel Diagnosis 1. Set the tire pressure to the placard values. 2. With the vehicle raised, ensure the wheels are centered on the hub by loosening all wheel nuts and hand-tightening all nuts first by hand while shaking the wheel, then torque to specifications using a torque wrench, NOT a torque stick. 3. Visually inspect the tires and the wheels. Inspect for evidence of the following conditions and correct as necessary: - Missing balance weights - Bent rim flange - Irregular tire wear - Incomplete bead seating - Tire irregularities (including pressure settings) - Mud/ice build-up in wheel - Stones in the tire tread - Remove any aftermarket wheels and/or tires and restore vehicle to original condition prior to diagnosing a smooth road shake condition. 4. Road test the vehicle using the Electronic Vibration Analyzer (EVA) essential tool. Drive for a sufficient distance on a known, smooth road surface to duplicate the condition. Determine if the vehicle is sensitive to brake apply. If the brakes are applied lightly and the pulsation felt in the steering wheel increases, refer to the Brakes section of the service manual that deals with brake-induced pulsation. If you can start to hear the vibration as a low boom noise (in addition to feeling it), but cannot see it, the vehicle likely has a first order (one pulse per propshaft revolution) driveline vibration. Driveline first order vibrations are high enough in frequency that most humans can start to hear them at highway speeds, but are too high to be able to be easily seen. These issues can be caused by driveline imbalance or misalignment. If the vehicle exhibits this low boom and the booming pulses in-and-out on a regular basis (like a throbbing), chances are good that the vehicle could have driveline vibration. This type Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 00-03-10-006F > May > 10 > Wheels/Tires - Tire Radial Force Variation (RFV) > Page 9976 of vibration is normally felt more in the "seat of the pants" than the steering wheel. 5. Next, record the Hertz (Hz) reading as displayed by the EVA onto the tire data worksheet found at the end of this bulletin. This should be done after a tire break-in period of at least 16 km (10 mi) at 72 km/h (45 mph) or greater, in order to eliminate any possible tire flat-spotting. This reading confirms what the vehicle vibration frequency is prior to vehicle service and documents the amount of improvement occurring as the result of the various steps taken to repair. Completing the Steering Wheel Shake Worksheet below is required. A copy of the completed worksheet must be saved with the R.O. and a copy included with any parts returned to the Warranty Parts Center for analysis. A reading of 35 to 50 Hz typically indicates a first order propshaft vibration. If this is the situation, refer to Corporate Bulletin Number 08-07-30-044D. Generally, a reading between 10 and 20 Hz indicates a tire/wheel vibration and if this is the reading obtained, continue using this bulletin. If the tire 1st order vibration goes away and stays away during this evaluation, the cause is likely tire flat-spotting. Tire flat-spotting vibration may come and go at any speed over 72 km/h (45 mph) during the first 10 minutes of operation, if vibration continues after 10 minutes of driving at speeds greater than 72 km/h (45 mph), tire flat-spotting can be ruled out as the cause for vibration. 6. If flat-spotting is the cause, provide the explanation that this has occurred due to the vehicle being parked for long periods of time and that the nature of the tire is to take a set. Refer to Corporate Bulletin Number 03-03-10-007E: Information on Tire/Wheel Characteristics (Vibration, Balance, Shake, Flat Spotting) of GM Original Equipment Tires. 7. If the road test indicates a shake/vibration exists, check the imbalance of each tire/wheel assembly on a known, calibrated, off-car dynamic balancer.Make sure the mounting surface of the wheel and the surface of the balancer are absolutely clean and free of debris. Be sure to chose the proper cone/collet for the wheel, and always use the pilot bore for centering. Never center the wheel using the hub-cap bore since it is not a precision machined surface. If any assembly calls for more than 1/4 ounce on either rim flange, remove all balance weights and rebalance to as close to zero as possible. If you can see the vibration (along with feeling it) in the steering wheel (driving straight without your hands on the wheel), it is very likely to be a tire/wheel first order (one pulse per revolution) disturbance. First order disturbances can be caused by imbalance as well as non-uniformities in tires, wheels or hubs. This first order frequency is too low for a human to hear, but if the amplitude is high enough, it can be seen. If a vibration or shake still exists after balancing, any out of round conditions, of the wheel, and force variation conditions of the tire, must be addressed. Equipment such as the Hunter GSP9700 can address both (it is also a wheel balancer). Tire radial force vibration (RFV) can be defined as the amount of stiffness variation the tire will produce in one revolution under a constant load. Radial force variation is what the vehicle feels because the load (weight) of the vehicle is always on the tires. Although free runout of tires (not under load) is not always a good indicator of a smooth ride, it is critical that total tire/wheel assembly runout be within specification. Equipment such as the Hunter GSP9700 loads the tire, similar to on the vehicle, and measures radial force variation of the tire/wheel assembly. Note that the wheel is affecting the tire's RFV measurement at this point. To isolate the wheel, its runout must be measured. This can be easily done on the Hunter, without the need to set up dial indicators. If the wheel meets the runout specification, the tire's RFV can then be addressed. After measuring the tire/wheel assembly under load, and the wheel alone, the machine then calculates (predicts) the radial force variation of the tire. However, because this is a prediction that can include mounting inaccuracies, and the load wheel is much smaller in diameter than used in tire production, this type of service equipment should NOT be used to audit new tires. Rather, it should be used as a service diagnostic tool to minimize radial force variation of the tire/wheel assembly. Equipment such as the Hunter GSP9700 does an excellent job of measuring wheel runout, and of finding the low point of the wheel (for runout) and the high point of the tire (for radial force variation). This allows the tire to be matched mounted to the wheel for lowest tire/wheel assembly force variation. The machine will simplify this process into easy steps. The following assembly radial force variation numbers should be used as a guide: When measuring RFV and match mounting tires perform the following steps. Measuring Wheel Runout and Assembly Radial Force Variation Important The completed worksheet at the end of this bulletin must be attached to the hard copy of the repair order. - Measure radial force variation and radial runout. - If a road force/balancing machine is used, record the radial force variation (RFV) on the worksheet at the end of this bulletin. It may be of benefit to have the lowest RFV assembly to the front left corner. If the machine is not available and the EVA data suggests there is an issue, swap the tire and wheel assemblies from the front to the back. Re-check on the EVA and if the problem still exists, test another vehicle to find tires that do not exhibit the same frequency and swap those tires onto the subject vehicle. - If a runout/balancing machine is used, record the radial runout of the tire/wheel assemblies on the worksheet at the end of this bulletin. If one or more of the tire/wheel assemblies are more than.040 in (1.02 mm), match mount the tire to the wheel to get below.040 in (1.02 mm). For sensitive customers, readings of 0.030 inch (0.76 mm) or less are preferable, it may also be of benefit to have the lowest runout assembly to the front left corner. If the machine is not available and the EVA data suggests there is an issue, swap the tire and wheel assemblies from the front to the back. Re-check on the EVA and if the problem still exists, test another vehicle to find tires that do not exhibit the same frequency and swap those tires Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 00-03-10-006F > May > 10 > Wheels/Tires - Tire Radial Force Variation (RFV) > Page 9977 onto the subject vehicle. - After match mounting, the tire/wheel assembly must be rebalanced. If match mounting tires to in-spec wheels produces assembly values higher than these, tire replacement may be necessary. Replacing tires at lower values will probably mean good tires are being condemned. Because tires can sometimes become temporarily flat-spotted, which will affect force variation, it is important that the vehicle be driven at least 16 km (10 mi) prior to measuring. Tire pressure must also be adjusted to the usage pressure on the vehicle's tire placard prior to measuring. Most GM vehicles will tolerate radial force variation up to these levels. However, some vehicles are more sensitive, and may require lower levels. Also, there are other tire parameters that equipment such as the Hunter GSP9700 cannot measure that may be a factor. In such cases, TAC should be contacted for further instructions. Important - When mounting a GM wheel to a wheel balancer/force variation machine, always use the wheel's center pilot hole. This is the primary centering mechanism on all GM wheels; the bolt holes are secondary. Usually a back cone method to the machine should be used. For added accuracy and repeatability, a flange plate should be used to clamp the wheel onto the cone and machine. This system is offered by all balancer manufacturers in GM's dealer program. - Any type of service equipment that removes tread rubber by grinding, buffing or truing is NOT recommended, and may void the tire warranty. However, tires may have been ground by the tire company as part of their tire manufacturing process. This is a legitimate procedure. Steering Wheel Shake Worksheet When diagnosing vibration concerns, use the following worksheet in conjunction with the appropriate Vibration Analysis-Road testing procedure in the Vibration Correction sub-section in SI. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 00-03-10-006F > May > 10 > Wheels/Tires - Tire Radial Force Variation (RFV) > Page 9978 Refer to the appropriate section of SI for specifications and repair procedures that are related to the vibration concern. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 05-03-10-003F > Apr > 10 > Tires/Wheels - Low Tire/Leaking Cast Aluminum Wheels Wheels: All Technical Service Bulletins Tires/Wheels - Low Tire/Leaking Cast Aluminum Wheels TECHNICAL Bulletin No.: 05-03-10-003F Date: April 27, 2010 Subject: Low Tire Pressure, Leaking Cast Aluminum Wheels (Repair with Adhesive Sealant) Models: 2011 and Prior GM Passenger Cars and Light Duty Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X with Cast Aluminum Wheels Supercede: This bulletin is being revised to update the model years and the bulletin reference information. Please discard Corporate Bulletin Number 05-03-10-003E (Section 03 - Suspension). Condition Some customers may comment on a low tire pressure condition. Diagnosis of the low tire pressure condition indicates an air leak through the cast aluminum wheel. Cause Porosity in the cast aluminum wheel may be the cause. Notice This bulletin specifically addresses issues related to the wheel casting that may result in an air leak. For issues related to corrosion of the wheel in service, please refer to Corporate Bulletin Number 08-03-10-006C - Tire Slowly Goes Flat, Tire Air Loss, Low Tire Pressure Warning Light Illuminated, Aluminum Wheel Bead Seat Corrosion (Clean and Resurface Wheel Bead Seat). Correction 1. Remove the tire and wheel assembly from the vehicle. Refer to the appropriate service procedure in SI. 2. Locate the leaking area by inflating the tire to 276 kPa (40 psi) and dipping the tire/wheel assembly in a water bath, or use a spray bottle with soap and water to locate the specific leak location. Important - If the porosity leak is located in the bead area of the aluminum rim (where the tire meets the rim), the wheel should be replaced. - If two or more leaks are located on one wheel, the wheel should be replaced. 3. If air bubbles are observed, mark the location. - If the leak location is on the tire/rubber area, refer to Corporate Bulletin Number 04-03-10-001F Tire Puncture Repair Procedures for All Cars and Light Duty Trucks. - If the leak is located on the aluminum wheel area, continue with the next step. 4. Inscribe a mark on the tire at the valve stem in order to indicate the orientation of the tire to the wheel. 5. Dismount the tire from the wheel. Refer to Tire Mounting and Dismounting. 6. Remove the tire pressure sensor. Refer to Tire Pressure Sensor removal procedure in SI. 7. Scuff the INSIDE rim surface at the leak area with #80 grit paper and clean the area with general purpose cleaner, such as 3M(R) General Purpose Adhesive Cleaner, P/N 08984, or equivalent. 8. Apply a 3 mm (0.12 in) thick layer of Silicone - Adhesive/Sealant, P/N 12378478 (in Canada, use 88900041), or equivalent, to the leak area. 9. Allow for the adhesive/sealant to dry. Notice Caution must be used when mounting the tire so as not to damage the sealer. Damaging the repair area may result in an air leak. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 05-03-10-003F > Apr > 10 > Tires/Wheels - Low Tire/Leaking Cast Aluminum Wheels > Page 9983 10. Align the inscribed mark on the tire with the valve stem on the wheel. 11. Reinstall the Tire Pressure Sensor. Refer to Tire Pressure Sensor installation procedure in SI. 12. Mount the tire on the wheel. Refer to Tire Mounting and Dismounting. 13. Pressurize the tire to 276 kPa (40 psi) and inspect for leaks. 14. Adjust tire pressure to meet the placard specification. 15. Balance the tire/wheel assembly. Refer to Tire and Wheel Assembly Balancing - Off-Vehicle. 16. Install the tire and wheel assembly onto the vehicle. Refer to the appropriate service procedure in SI. Parts Information Warranty Information (excluding Saab U.S. Models) Important The Silicone - Adhesive/Sealant comes in a case quantity of six. ONLY charge warranty one tube of adhesive/sealant per wheel repair. For vehicles repaired under warranty, use: One leak repair per wheel. Warranty Information (Saab U.S. Models) For vehicles repaired under warranty, use the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 04-03-10-012B > Feb > 08 > Wheels - Chrome Wheel Brake Dust Accumulation/Pitting Wheels: All Technical Service Bulletins Wheels - Chrome Wheel Brake Dust Accumulation/Pitting Bulletin No.: 04-03-10-012B Date: February 01, 2008 INFORMATION Subject: Pitting and Brake Dust on Chrome wheels Models: 2008 and Prior GM Passenger Cars and Trucks (including Saturn) 2008 and Prior HUMMER H2, H3 2005-2008 Saab 9-7X Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 04-03-10-012A (Section 03 - Suspension). Analysis of Returned Wheels Chrome wheels returned under the New Vehicle Limited Warranty for pitting concerns have recently been evaluated. This condition is usually most severe in the vent (or window) area of the front wheels. This "pitting" may actually be brake dust that has been allowed to accumulate on the wheel. The longer this accumulation builds up, the more difficult it is to remove. Cleaning the Wheels In all cases, the returned wheels could be cleaned to their original condition using GM Vehicle Care Cleaner Wax, P/N 12377966 (in Canada, P/N 10952905). When using this product, you should confine your treatment to the areas of the wheel that show evidence of the brake dust build-up. This product is only for use on chromed steel or chromed aluminum wheels. Parts Information Warranty Information Wheel replacement for this condition is NOT applicable under the terms of the New Vehicle Limited Warranty. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 99-03-10-102 > Jun > 99 > Warranty - OE Chrome Plated Aluminum Wheel ID Wheels: All Technical Service Bulletins Warranty - OE Chrome Plated Aluminum Wheel ID File In Section: 03 - Suspension Bulletin No.: 99-03-10-102 Date: June, 1999 INFORMATION Subject: Original Equipment Chrome Plated Aluminum Wheel Identification Models: 1999 and Prior Passenger Cars and Light Duty Trucks Chrome plated aluminum wheels have been returned to the Warranty Parts Center that are not the original equipment (OE) components. Original equipment chrome plated aluminum wheels can be identified by either a balance weight clip retention groove (1) or a step (2) that is machined around both of the wheel's rim flanges. The rim flanges (3) of painted original equipment aluminum wheels do not have a groove or a step. Chrome plated aluminum wheels that do not have the wheel rim flange groove or step are aftermarket chrome plated components and are NOT warrantable. Any aftermarket chrome wheels received by the Warranty Parts Center will be charged back to the dealership. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 72-05-05 > Aug > 97 > Warranty - Guidelines for Using E0420 Wheel Replace Wheels: All Technical Service Bulletins Warranty - Guidelines for Using E0420 Wheel Replace File In Section: Warranty Administration Bulletin No.: 72-05-05 Date: August, 1997 WARRANTY ADMINISTRATION Subject: Guidelines for Using EO42O Wheel Replace Models: 1989-98 Passenger Cars and Light Duty Trucks The purpose of this bulletin is to provide service personnel with guidelines for using the above subject labor operation. Effective with repair orders dated on or after September 1, 1997, dealers are to be guided by the following: ^ Aluminum Wheels (including chrome plated) with Porosity - Wheels that exhibit porosity should be repaired as described in the vehicle service manual. Wheels should not be replaced without wholesale approval. ^ Aluminum Wheels (except chrome plated) with a "Finish Defect" - Wheels that exhibit a defect in the finish, (i.e., discoloration or surface degradation) should be refinished as described in the Corporate Service Bulletin Number 53-17-03A released in May, 1996. ^ Chrome Wheels - Wheels that are chromed and found to have a finish defect can only be replaced. ^ Aluminum and chrome wheels replaced under warranty will be subject to random part review and inspection. Those wheels inspected and found not to be defective and/or should have been repaired, will be subject to charge back. Wheels damaged by normal wear, road hazards, car wash brushes, or other physical or chemical damage are not eligible for warranty coverage. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 531703A > May > 96 > Aluminum Wheels Refinishing Technical Service Bulletin # 531703A Date: 960501 Aluminum Wheels - Refinishing File In Section: 10 - Body Bulletin No.: 53-17-03A Date: May, 1996 INFORMATION Subject: Aluminum Wheel Refinishing Models: 1991-96 Passenger Cars and Trucks This bulletin is being revised to delete the 1990 model year and add the 1996 model year. Please discard Corporate Bulletin Number 53-17-03 (Section 10 - Body). This bulletin supersedes and cancels all previous service bulletins concerning the refinishing of aluminum wheels. The purpose of this service bulletin is to assist dealerships in repairing the discoloration or surface degradation that has occurred on styled aluminum wheels. This bulletin provides NEW PROCEDURES AND SPECIFIC MATERIALS for the refinishing of painted aluminum wheels or aluminum wheels with discoloration or surface degradation. Important: THE RE-MACHINING OF ALUMINUM WHEELS IS NOT RECOMMENDED. THE RE-CLEAR COATING OF ALUMINUM WHEELS IS NO LONGER RECOMMENDED DUE TO CONCERNS OF REPAIR DURABILITY The new procedure requires the wheel surface be plastic media blasted to remove old paint or clear coat. CHEMICAL STRIPPERS ARE NOT RECOMMENDED. Material Required System 1: DuPont Products 3939-S Cleaning Solvent 615/616 Etching Primer URO 5000 Primer Surfacer IMRON 6000 Basecoat 3440-S IMRON Clear System 2: PPG Products DX533 Aluminum Cleaner DX503 Aluminum Conditioner DP Epoxy Primer Deltron Basecoat (DBC) Concept 2001 Clear Acrylic Urethane System 3: Spies Hecker Permahyd Silicone Remover 7090 Permahyd 1:1 Primer 4070 Permahyd 2:1 Surfacer 5080 Permahyd Base Coat Series 280/285 Permahyd H.S. Clearcoat 8060 Color Selection If the wheels being painted were previously clearcoated aluminum, we would recommend using Corsican SILVER WAEQ9283 for a fine "aluminum-like" look or Sparkle SILVER WA9967 for a very bright look. As an option to the customer, you may also use body color. For color Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 531703A > May > 96 > Aluminum Wheels Refinishing > Page 10000 selection and verification, refer to your paint manufacturer's color book. On wheels that were previous clearcoated aluminum it is recommended that all four wheels and their center caps be refinished to maintain color uniformity. Important: THE PRODUCTS LISTED MUST BE USED AS A SYSTEM. DO NOT MIX OTHER MANUFACTURERS' PRODUCT LINES WITH THE REQUIRED MATERIALS. PRODUCTS LISTED IN THIS BULLETIN HAVE SHOWN THE REQUIRED REPAIR DURABILITY, AND CURRENTLY ARE THE ONLY PAINT SYSTEMS THAT MEET GM SPECIFICATION 4350M-A336. Procedures 1. Remove wheels from vehicle. Tires may remain mounted on wheels. 2. Remove balance weights and mark their location on tire. 3. Wipe excess grease, etc. from wheels with wax and grease remover. 4. Have wheels plastic media blasted to remove clearcoat. FOR FURTHER INFORMATION ON MEDIA BLASTING IN YOUR AREA, CALL US TECHNOLOGIES INC., CONTACT DAVE ROSENBURG AT 1-800-634-9185. Caution: IT IS MANDATORY THAT ADEQUATE RESPIRATORY PROTECTION BE WORN. EXAMPLES OF SUCH PROTECTION ARE: AIR LINE RESPIRATORS WITH FULL HOOD OR HALF MASK. IF NOT AVAILABLE, USE A VAPOR/PARTICULATE RESPIRATOR THAT RESPIRATOR MANUFACTURER RECOMMENDS AS EFFECTIVE FOR ISOCYANATE VAPOR AND MISTS (UNLESS LOCAL REGULATIONS PREVAIL). 5. Painting Process a. Refer to Attachments 1-3 for each System's individual formula and process. b. After following the specific System's individual formula and process, follow these steps: 6. Unmask wheels. 7. Clean all wheel mounting surface of any corrosion, overspray, or dirt. 8. Install new coated balance weights, at marked locations. 9. Replace wheels on vehicle. 10. USE A TORQUE STICK ON AN IMPACT WRENCH, OR A TORQUE WRENCH TO CONSISTENTLY AND UNIFORMLY FASTEN THE WHEEL TO THE SPECIFIED TORQUE FOR THE VEHICLE. THE STAR PATTERN MUST BE FOLLOWED. Important: TORQUE STICKS MUST BE USED ANY TIME AN IMPACT WRENCH IS USED TO TIGHTEN WHEEL NUTS. Warranty Information For vehicles repaired under warranty, use as shown. Attachment 1 - DuPont Products Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 531703A > May > 96 > Aluminum Wheels Refinishing > Page 10001 Painting Process System: Dupont Products Paint Color Information: Corsican Silver WA EQ9283 Dupont # C9143, Sparkle Silver WA9967 Dupont # C9339 1. Wipe wheel with cleaning solvent: 3939-S, 3949-S or 3900-S. 2. Mask off tires. Important: 3. Mask off all wheel mounting surfaces and wheel mount surfaces. 4. Apply two coats of 615/616-S etching primer to wheel allowing 10 minutes flash between coats. Allow to dry for 30 minutes before applying primer coat. 5. Apply URO 5000 primer 1220/193-S + accelerator 389-S using two coats at 65-70 PSI at the gun. Allow 12-15 minutes between coats. Force bake 30 minutes at 140°F (60°C). 6. Scuff sand using green Scotch-Brite pad. 7. Solvent wipe before top coating. 8. Apply IMRON 6000 base coat to wheel. 2-3 coats to hiding at 60-70 PSI allowing to flash between coats. Base coat needs to dry 20-30 minutes before clearcoat is applied. 9. Apply 3440-S clearcoat to wheel using two coats at 60-70 PSI. Flash 10-15 minutes between coats. 389-S can be used in basecoat and clearcoat to give faster set up times. 10. Allow overnight dry before reassemble. Can be baked for 30 minutes at 140°F (60°C). Attachment 2 - PPG Products Painting Process: PPG System Paint Color Information: Corsican Silver WAEQ9283; PPG # DBC-3531, Sparkle Silver WA9967; PPG # 35367 1. Wash entire wheel with aluminum cleaner DX533, mix 1:3 with water. Allow to react 2-3 minutes and rinse thoroughly. 2. Wash entire wheel with aluminum conditioner DX5O3 straight from the container. Allow to react 2-3 minutes until pale gold or tan color develops. Rinse thoroughly and dry. 3. Mask off tires. Important: 4. Mask off all wheel nut mounting surfaces and wheel mounting surfaces. 5. Apply 1-2 coats of DP Primer and allow to flash for 15-20 minutes. 6. Apply 2-3 coats of Deltron Basecoat (DBC) and allow to flash 20 minutes after the final coat. 7. Apply two (2) wet coats of Concept 2001 Acrylic urethane. 8. Flash 20 minutes and bake 140°F (60°C) for 30 minutes. For more information contact your PPG Jobber. Attachment 3 - Spies Hecker Painting Process: Spies Hecker System Paint Color Information: Corsican Silver AWEQ9283; SH-72913, Sparkle Silver WA9967; SH-71912 1. Clean with Permahyd Silicone Remover 7090. 2. Mask off tires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheels: > 531703A > May > 96 > Aluminum Wheels Refinishing > Page 10002 Important: 3. Mask off all wheel nut mounting surfaces and wheel mounting surfaces. 4. Apply 1-1/2 coats of Permahyd 1:1 Primer 4070. Mix 1:1 with Permahyd Hardener 3070 as per TDS. 5. Allow to flash for 30 minutes. 6. Apply two (2) coats of Permahyd 2:1 Surfacer 5080. Mix 2:1 with Permahyd Hardener 3071 as per TDS. 7. Bake for 60 minutes at 140°F (60°C) or allow to flash for 3 hours at 68°F (20°C). 8. Apply Permahyd Base Coat Series 280/285 as per TDS. 9. Allow to flash 10 to 15 minutes. 10. Apply 1 to 2 coats of Permacron High Solid Clear Coat 8060 as per TDS. 11. Allow to flash 10 minutes. Then bake at 140°F (60°C) for 40 minutes. For more information, contact your SPIES HECKER Jobber. We believe these sources and their products to be reliable. There may be additional manufacturers of such products. General Motors does not endorse, indicate any preference for or assume any responsibility for the products or equipment from these firms or for any such items which may be available from other sources. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 00-03-10-002F > Apr > 11 > Wheels - Chrome Wheel Staining/Pitting/Corrosion Wheels: All Technical Service Bulletins Wheels - Chrome Wheel Staining/Pitting/Corrosion INFORMATION Bulletin No.: 00-03-10-002F Date: April 21, 2011 Subject: Chemical Staining, Pitting, Corrosion and/or Spotted Appearance of Chromed Aluminum Wheels Models: 2012 and Prior GM Cars and Trucks Supercede: This bulletin is being revised to update model years, suggest additional restorative products and add additional corrosion information. Please discard Corporate Bulletin Number 00-03-10-002E (Section 03 - Suspension). Important You may give a copy of this bulletin to the customer. What is Chemical Staining of Chrome Wheels? Figure 1 Chemical staining in most cases results from acid based cleaners (refer to Figure 1 for an example). These stains are frequently milky, black, or greenish in appearance. They result from using cleaning solutions that contain acids on chrome wheels. Soap and water is usually sufficient to clean wheels. If the customer insists on using a wheel cleaner they should only use one that specifically states that it is safe for chromed wheels and does not contain anything in the following list. (Dealers should also survey any products they use during prep or normal cleaning of stock units for these chemicals.) - Ammonium Bifluoride (fluoride source for dissolution of chrome) - Hydrofluoric Acid (directly dissolves chrome) - Hydrochloric Acid (directly dissolves chrome) - Sodium Dodecylbenzenesulfonic Acid - Sulfamic Acid - Phosphoric Acid - Hydroxyacetic Acid Notice Many wheel cleaner instructions advise to take care to avoid contact with painted surfaces. Most customers think of painted surfaces as the fenders, quarter panels and other exterior sheet metal. Many vehicles have painted brake calipers. Acidic wheel cleaners may craze, crack, or discolor the paint on the brake calipers. Damage from wheel cleaners is not covered under the vehicle new car warranty. Soap and water applied with a soft brush is usually all that is required to clean the calipers. Whenever any wheel cleaner is used, it must be THOROUGHLY rinsed off of the wheel with clean, clear water. Special care must be taken to rinse under the hub cap, balance weights, wheel nuts, lug nut caps, between the wheel cladding and off the back side of the wheel. Wheels returned to the Warranty Parts Center (WPC) that exhibit damage from wheel cleaners most often have the damage around and under the wheel weight where the cleaner was incompletely flushed away. Notice Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 00-03-10-002F > Apr > 11 > Wheels - Chrome Wheel Staining/Pitting/Corrosion > Page 10008 Do not use cleaning solutions that contain hydrofluoric, oxalic and most other acids on chrome wheels (or any wheels). If the customer is unsure of the chemical make-up of a particular wheel cleaner, it should be avoided. For wheels showing signs of milky staining from acidic cleaners, refer to Customer Assistance and Instructions below. Warranty of Stained Chrome Wheels Stained wheels are not warrantable. Most acid based cleaners will permanently stain chrome wheels. Follow-up with dealers has confirmed that such cleaners were used on wheels that were returned to the Warranty Parts Center (WPC). Any stained wheels received by the WPC will be charged back to the dealership. To assist the customer, refer to Customer Assistance and Instructions below. Pitting or Spotted Appearance of Chrome Wheels Figure 2 A second type or staining or finish disturbance may result from road chemicals, such as calcium chloride used for dust control of unpaved roads. The staining will look like small pitting (refer to Figure 2). This staining will usually be on the leading edges of each wheel spoke, but may be uniformly distributed. If a vehicle must be operated under such conditions, the chrome wheels should be washed with mild soap and water and thoroughly rinsed as soon as conveniently possible. Important Road chemicals, such as calcium chloride used for dust control of unpaved roads, can also stain chrome wheels. The staining will look like small pitting. This staining will usually be on the leading edges of each wheel spoke. This is explained by the vehicle traveling in the forward direction while being splashed by the road chemical. If a vehicle must be operated under such conditions, the chrome wheels should be washed with mild soap and water and thoroughly rinsed as soon as conveniently possible. Warranty of Pitted or Spotted Chrome Wheels Wheels returned with pitting or spotting as a result of road chemicals may be replaced one time. Damage resulting from contact with these applied road chemicals is corrosive to the wheels finish and may cause damage if the wheels are not kept clean. Important Notify the customer that this is a one time replacement. Please stress to the customer the vital importance of keeping the wheels clean if they are operating the vehicle in an area that applies calcium chloride or other dust controlling chemicals! "GM of Canada" dealers require prior approval by the District Manager - Customer Care and Service Process (DM-CCSP). "Stardust" Corrosion of Chrome Wheels Figure 3 A third type of finish disturbance results from prolonged exposure to brake dust and resultant penetration of brake dust through the chrome. As brakes are applied hot particles of brake material are thrown off and tend to be forced through the leading edge of the wheel spoke windows by airflow. These Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 00-03-10-002F > Apr > 11 > Wheels - Chrome Wheel Staining/Pitting/Corrosion > Page 10009 hot particles embed themselves in the chrome layer and create a small pit. If the material is allowed to sit on the wheel while it is exposed to moisture or salt, it will corrode the wheel beneath the chrome leaving a pit or small blister in the chrome. Heavy brake dust build-up should be removed from wheels by using GM Chrome Cleaner and Polish, P/N 1050173 (in Canada use 10953013). For moderate cleaning, light brake dust build-up or water spots use GM Swirl Remover Polish, P/N 12377965 (in Canada, use Meguiars Plast-X(TM) Clear Plastic Cleaner and Polish #G12310C**). After cleaning, the wheel should be waxed using GM Cleaner Wax, P/N 12377966 (in Canada, use Meguiars Cleaner Wax #M0616C**), which will help protect the wheel from brake dust and reduce adhesion of any brake dust that gets on the wheel surface. For general maintenance cleaning, PEEK Metal Polish† may be used. It will clean and shine the chrome and leave behind a wax coating that may help protect the finish. Warranty of Stardust Corroded Chrome Wheels Wheels returned with pitting or spotting as a result of neglect and brake dust build-up may be replaced one time. Important Notify the customer that this is a one time replacement. Please stress to the customer the vital importance of keeping the wheels clean and free of prolonged exposure to brake dust build-up. "GM of Canada" dealers require prior approval by the District Manager - Customer Care and Service Process (DM-CCSP). Customer Assistance and Instructions GM has looked for ways customers may improve the appearance of wheels damaged by acidic cleaners. The following product and procedure has been found to dramatically improve the appearance of stained wheels. For wheels that have milky stains caused by acidic cleaners try the following: Notice THE 3M CHROME AND METAL POLISH REQUIRED FOR THIS PROCEDURE IS AN EXTREMELY AGGRESSIVE POLISH/CLEANER. THE WHEELS MUST BE CLEANED BEFORE APPLICATION TO AVOID SCRATCHING THE WHEEL SURFACE. THIS PRODUCT WILL REDUCE THE THICKNESS OF THE CHROME PLATING ON THE WHEEL AND IF USED INCORRECTLY OR EXCESSIVELY MAY REMOVE THE CHROME PLATING ALL TOGETHER, EXPOSING A LESS BRIGHT AND BRASSY COLORED SUB-LAYER. FOLLOW INSTRUCTIONS EXACTLY. 1. Wash the wheels with vigorously with soap and water. This step will clean and may reduce wheel staining. Flood all areas of the wheel with water to rinse. 2. Dry the wheels completely. Notice Begin with a small section of the wheel and with light pressure buff off polish and examine results. ONLY apply and rub with sufficient force and time to remove enough staining that you are satisfied with the results. Some wheels may be stained to the extent that you may only achieve a 50% improvement while others may be able to be restored to the original lustre. IN ALL CASES, only apply until the results are satisfactory. 3. Apply 3M Chrome and Metal Polish #39527* with a clean terry cloth towel. As you apply the polish, the staining will be diminished. 4. When dry, buff off the polish with a clean portion of the towel. 5. Repeat application of the 3M Chrome and Metal Polish until satisfied with the results. If continued applications fail to improve the appearance further discontinue use. This procedure will improve the appearance of the wheels and may, with repeated applications, restore the finish dramatically. For wheels that exhibit spotting from road chemicals the above procedure may marginally improve the condition but will not restore the finish or remove the pitting. In this type of staining the wheel finish has actually been removed in spots and no manner of cleaning will restore the finish. †*We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Parts Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 00-03-10-002F > Apr > 11 > Wheels - Chrome Wheel Staining/Pitting/Corrosion > Page 10010 *This product is currently available from 3M. To obtain information for your local retail location please call 3M at 1-888-364-3577. **This product is currently available from Meguiars (Canada). To obtain information for your local retail location please call Meguiars at 1-800-347-5700 or at www.meguiarscanada.com. ^ This product is currently available from Tri-Peek International. To obtain information for your local retail location please call Tri-Peek at 1-877-615-4272 or at www.tripeek.com. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 99-08-51-007E > Mar > 11 > Wheels/Tires Refinishing Aluminum Wheels Wheels: All Technical Service Bulletins Wheels/Tires - Refinishing Aluminum Wheels INFORMATION Bulletin No.: 99-08-51-007E Date: March 17, 2011 Subject: Refinishing Aluminum Wheels Models: 2012 and Prior GM Passenger Cars and Trucks Supercede: This bulletin is being revised to add additional model years. Please discard Corporate Bulletin Number 99-08-51-007D (Section 08 - Body and Accessories). This bulletin updates General Motor's position on refinishing aluminum wheels. GM does not endorse any repairs that involve welding, bending, straightening or re-machining. Only cosmetic refinishing of the wheel's coatings, using recommended procedures, is allowed. Evaluating Damage In evaluating damage, it is the GM Dealer's responsibility to inspect the wheel for corrosion, scrapes, gouges, etc. The Dealer must insure that such damage is not deeper than what can be sanded or polished off. The wheel must be inspected for cracks. If cracks are found, discard the wheel. Any wheels with bent rim flanges must not be repaired or refinished. Wheels that have been refinished by an outside company must be returned to the same vehicle. The Dealer must record the wheel ID stamp or the cast date on the wheel in order to assure this requirement. Refer to Refinisher's Responsibility - Outside Company later in this bulletin. Aluminum Wheel Refinishing Recommendations - Chrome-plated aluminum wheels Re-plating these wheels is not recommended. - Polished aluminum wheels These wheels have a polyester or acrylic clearcoat on them. If the clearcoat is damaged, refinishing is possible. However, the required refinishing process cannot be performed in the dealer environment. Refer to Refinisher's Responsibility - Outside Company later in this bulletin. - Painted aluminum wheels These wheels are painted using a primer, color coat, and clearcoat procedure. If the paint is damaged, refinishing is possible. As with polished wheels, all original coatings must be removed first. Media blasting is recommended. Refer to GM Aluminum Refinishing Bulletin #53-17-03A for the re-painting of this type of wheel. - Bright, machined aluminum wheels These wheels have a polyester or acrylic clearcoat on them. In some cases, the recessed "pocket" areas of the wheel may be painted. Surface refinishing is possible. The wheel must be totally stripped by media blasting or other suitable means. The wheel should be resurfaced by using a sanding process rather than a machining process. This allows the least amount of material to be removed. Important Do not use any re-machining process that removes aluminum. This could affect the dimensions and function of the wheel. Painting is an option to re-clearcoating polished and bright machined aluminum wheels. Paint will better mask any surface imperfections and is somewhat more durable than clearcoat alone. GM recommends using Corsican SILVER WAEQ9283 for a fine "aluminum-like" look or Sparkle SILVER WA9967 for a very bright look. As an option, the body color may also be used. When using any of the painting options, it is recommended that all four wheels be refinished in order to maintain color uniformity. Refer to GM Aluminum Refinishing Bulletin #53-17-03A for specific procedures and product recommendations. Refinisher's Responsibility - Outside Company Important Some outside companies are offering wheel refinishing services. Such refinished wheels will be permanently marked by the refinisher and are warranted by the refinisher. Any process that re-machines or otherwise re-manufactures the wheel should not be used. A refinisher's responsibility includes inspecting for cracks using the Zyglo system or the equivalent. Any cracked wheels must not be refinished. No welding, hammering or reforming of any kind is allowed. The wheel ID must be recorded and follow the wheel throughout the process in order to assure that the same wheel is returned. A plastic media blast may be used for clean up of the wheel. Hand and/or lathe sanding of the machined surface and the wheel window is allowed. Material removal, though, must be kept to a minimum. Re-machining of the wheel is not allowed. Paint and/or clear coat must not be present on the following surfaces: the nut chamfers, the wheel mounting surfaces and the wheel pilot hole. The refinisher must permanently ID stamp the wheel and warrant the painted/clearcoated surfaces for a minimum of one year or the remainder of the new vehicle warranty, whichever is Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 99-08-51-007E > Mar > 11 > Wheels/Tires Refinishing Aluminum Wheels > Page 10015 longer. Important Whenever a wheel is refinished, the mounting surface and the wheel nut contact surfaces must not be painted or clearcoated. Coating these surfaces could affect the wheel nut torque. When re-mounting a tire on an aluminum wheel, coated balance weights must be used in order to reduce the chance of future cosmetic damage. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 06-03-10-010A > Jun > 10 > Wheels - Changing Procedures/Precautions Wheels: All Technical Service Bulletins Wheels - Changing Procedures/Precautions INFORMATION Bulletin No.: 06-03-10-010A Date: June 09, 2010 Subject: Information on Proper Wheel Changing Procedures and Cautions Models: 2011 and Prior GM Passenger Cars and Trucks 2010 and Prior HUMMER Models 2005-2009 Saab 9-7X 2005-2009 Saturn Vehicles Attention: Complete wheel changing instructions for each vehicle line can be found under Tire and Wheel Removal and Installation in Service Information (SI). This bulletin is intended to quickly review and reinforce simple but vital procedures to reduce the possibility of achieving low torque during wheel installation. Always refer to SI for wheel lug nut torque specifications and complete jacking instructions for safe wheel changing. Supercede: This bulletin is being revised to include the 2011 model year and update the available special tool list. Please discard Corporate Bulletin Number 06-03-10-010 (Section 03 Suspension). Frequency of Wheel Changes - Marketplace Driven Just a few years ago, the increasing longevity of tires along with greater resistance to punctures had greatly reduced the number of times wheels were removed to basically required tire rotation intervals. Today with the booming business in accessory wheels/special application tires (such as winter tires), consumers are having tire/wheel assemblies removed - replaced - or installed more than ever. With this increased activity, it opens up more of a chance for error on the part of the technician. This bulletin will review a few of the common concerns and mistakes to make yourself aware of. Proper Servicing Starts With the Right Tools The following tools have been made available to assist in proper wheel and tire removal and installation. - J 41013 Rotor Resurfacing Kit (or equivalent) - J 42450-A Wheel Hub Resurfacing Kit (or equivalent) Corroded Surfaces One area of concern is corrosion on the mating surfaces of the wheel to the hub on the vehicle. Excessive corrosion, dirt, rust or debris built up on these surfaces can mimic a properly tightened wheel in the service stall. Once the vehicle is driven, the debris may loosen, grind up or be washed away from water splash. This action may result in clearance at the mating surface of the wheel and an under-torqued condition. Caution Before installing a wheel, remove any buildup on the wheel mounting surface and brake drum or brake disc mounting surface. Installing wheels with poor metal-to-metal contact at the mounting surfaces can cause wheel nuts to loosen. This may cause a wheel to come off when the vehicle is moving, possibly resulting in a loss of control or personal injury. Whenever you remove the tire/wheel assemblies, you must inspect the mating surfaces. If corrosion is found, you should remove the debris with a die grinder equipped with a fine sanding pad, wire brush or cleaning disc. Just remove enough material to assure a clean, smooth mating surface. The J 41013 (or equivalent) can be used to clean the following surfaces: - The hub mounting surface - The brake rotor mounting surface - The wheel mounting surface Use the J 42450-A (or equivalent) to clean around the base of the studs and the hub. Lubricants, Grease and Fluids Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 06-03-10-010A > Jun > 10 > Wheels - Changing Procedures/Precautions > Page 10020 Some customers may use penetrating oils, grease or other lubricants on wheel studs to aid in removal or installation. Always use a suitable cleaner/solvent to remove these lubricants prior to installing the wheel and tire assemblies. Lubricants left on the wheel studs may cause improper readings of wheel nut torque. Always install wheels to clean, dry wheel studs ONLY. Notice Lubricants left on the wheel studs or vertical mounting surfaces between the wheel and the rotor or drum may cause the wheel to work itself loose after the vehicle is driven. Always install wheels to clean, dry wheel studs and surfaces ONLY. Beginning with 2011 model year vehicles, put a light coating of grease, GM P/N 1051344 (in Canada, P/N 9930370), on the inner surface of the wheel pilot hole to prevent wheel seizure to the axle or bearing hub. Wheel Stud and Lug Nut Damage Always inspect the wheel studs and lug nuts for signs of damage from crossthreading or abuse. You should never have to force wheel nuts down the stud. Lug nuts that are damaged may not retain properly, yet give the impression of fully tightening. Always inspect and replace any component suspected of damage. Tip Always start wheel nuts by hand! Be certain that all wheel nut threads have been engaged BEFORE tightening the nut. Important If the vehicle has directional tread tires, verify the directional arrow on the outboard side of the tire is pointing in the direction of forward rotation. Wheel Nut Tightening and Torque Improper wheel nut tightening can lead to brake pulsation and rotor damage. In order to avoid additional brake repairs, evenly tighten the wheel nuts to the proper torque specification as shown for each vehicle in SI. Always observe the proper wheel nut tightening sequence as shown below in order to avoid trapping the wheel on the wheel stud threads or clamping the wheel slightly off center resulting in vibration. The Most Important Service You Provide While the above information is well known, and wheel removal so common, technicians run the risk of becoming complacent on this very important Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 06-03-10-010A > Jun > 10 > Wheels - Changing Procedures/Precautions > Page 10021 service operation. A simple distraction or time constraint that rushes the job may result in personal injury if the greatest of care is not exercised. Make it a habit to double check your work and to always side with caution when installing wheels. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 04-03-10-012B > Feb > 08 > Wheels - Chrome Wheel Brake Dust Accumulation/Pitting Wheels: All Technical Service Bulletins Wheels - Chrome Wheel Brake Dust Accumulation/Pitting Bulletin No.: 04-03-10-012B Date: February 01, 2008 INFORMATION Subject: Pitting and Brake Dust on Chrome wheels Models: 2008 and Prior GM Passenger Cars and Trucks (including Saturn) 2008 and Prior HUMMER H2, H3 2005-2008 Saab 9-7X Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 04-03-10-012A (Section 03 - Suspension). Analysis of Returned Wheels Chrome wheels returned under the New Vehicle Limited Warranty for pitting concerns have recently been evaluated. This condition is usually most severe in the vent (or window) area of the front wheels. This "pitting" may actually be brake dust that has been allowed to accumulate on the wheel. The longer this accumulation builds up, the more difficult it is to remove. Cleaning the Wheels In all cases, the returned wheels could be cleaned to their original condition using GM Vehicle Care Cleaner Wax, P/N 12377966 (in Canada, P/N 10952905). When using this product, you should confine your treatment to the areas of the wheel that show evidence of the brake dust build-up. This product is only for use on chromed steel or chromed aluminum wheels. Parts Information Warranty Information Wheel replacement for this condition is NOT applicable under the terms of the New Vehicle Limited Warranty. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 99-03-10-102 > Jun > 99 > Warranty - OE Chrome Plated Aluminum Wheel ID Wheels: All Technical Service Bulletins Warranty - OE Chrome Plated Aluminum Wheel ID File In Section: 03 - Suspension Bulletin No.: 99-03-10-102 Date: June, 1999 INFORMATION Subject: Original Equipment Chrome Plated Aluminum Wheel Identification Models: 1999 and Prior Passenger Cars and Light Duty Trucks Chrome plated aluminum wheels have been returned to the Warranty Parts Center that are not the original equipment (OE) components. Original equipment chrome plated aluminum wheels can be identified by either a balance weight clip retention groove (1) or a step (2) that is machined around both of the wheel's rim flanges. The rim flanges (3) of painted original equipment aluminum wheels do not have a groove or a step. Chrome plated aluminum wheels that do not have the wheel rim flange groove or step are aftermarket chrome plated components and are NOT warrantable. Any aftermarket chrome wheels received by the Warranty Parts Center will be charged back to the dealership. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 72-05-05 > Aug > 97 > Warranty - Guidelines for Using E0420 Wheel Replace Wheels: All Technical Service Bulletins Warranty - Guidelines for Using E0420 Wheel Replace File In Section: Warranty Administration Bulletin No.: 72-05-05 Date: August, 1997 WARRANTY ADMINISTRATION Subject: Guidelines for Using EO42O Wheel Replace Models: 1989-98 Passenger Cars and Light Duty Trucks The purpose of this bulletin is to provide service personnel with guidelines for using the above subject labor operation. Effective with repair orders dated on or after September 1, 1997, dealers are to be guided by the following: ^ Aluminum Wheels (including chrome plated) with Porosity - Wheels that exhibit porosity should be repaired as described in the vehicle service manual. Wheels should not be replaced without wholesale approval. ^ Aluminum Wheels (except chrome plated) with a "Finish Defect" - Wheels that exhibit a defect in the finish, (i.e., discoloration or surface degradation) should be refinished as described in the Corporate Service Bulletin Number 53-17-03A released in May, 1996. ^ Chrome Wheels - Wheels that are chromed and found to have a finish defect can only be replaced. ^ Aluminum and chrome wheels replaced under warranty will be subject to random part review and inspection. Those wheels inspected and found not to be defective and/or should have been repaired, will be subject to charge back. Wheels damaged by normal wear, road hazards, car wash brushes, or other physical or chemical damage are not eligible for warranty coverage. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 531703A > May > 96 > Aluminum Wheels Refinishing Technical Service Bulletin # 531703A Date: 960501 Aluminum Wheels - Refinishing File In Section: 10 - Body Bulletin No.: 53-17-03A Date: May, 1996 INFORMATION Subject: Aluminum Wheel Refinishing Models: 1991-96 Passenger Cars and Trucks This bulletin is being revised to delete the 1990 model year and add the 1996 model year. Please discard Corporate Bulletin Number 53-17-03 (Section 10 - Body). This bulletin supersedes and cancels all previous service bulletins concerning the refinishing of aluminum wheels. The purpose of this service bulletin is to assist dealerships in repairing the discoloration or surface degradation that has occurred on styled aluminum wheels. This bulletin provides NEW PROCEDURES AND SPECIFIC MATERIALS for the refinishing of painted aluminum wheels or aluminum wheels with discoloration or surface degradation. Important: THE RE-MACHINING OF ALUMINUM WHEELS IS NOT RECOMMENDED. THE RE-CLEAR COATING OF ALUMINUM WHEELS IS NO LONGER RECOMMENDED DUE TO CONCERNS OF REPAIR DURABILITY The new procedure requires the wheel surface be plastic media blasted to remove old paint or clear coat. CHEMICAL STRIPPERS ARE NOT RECOMMENDED. Material Required System 1: DuPont Products 3939-S Cleaning Solvent 615/616 Etching Primer URO 5000 Primer Surfacer IMRON 6000 Basecoat 3440-S IMRON Clear System 2: PPG Products DX533 Aluminum Cleaner DX503 Aluminum Conditioner DP Epoxy Primer Deltron Basecoat (DBC) Concept 2001 Clear Acrylic Urethane System 3: Spies Hecker Permahyd Silicone Remover 7090 Permahyd 1:1 Primer 4070 Permahyd 2:1 Surfacer 5080 Permahyd Base Coat Series 280/285 Permahyd H.S. Clearcoat 8060 Color Selection If the wheels being painted were previously clearcoated aluminum, we would recommend using Corsican SILVER WAEQ9283 for a fine "aluminum-like" look or Sparkle SILVER WA9967 for a very bright look. As an option to the customer, you may also use body color. For color Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 531703A > May > 96 > Aluminum Wheels Refinishing > Page 10038 selection and verification, refer to your paint manufacturer's color book. On wheels that were previous clearcoated aluminum it is recommended that all four wheels and their center caps be refinished to maintain color uniformity. Important: THE PRODUCTS LISTED MUST BE USED AS A SYSTEM. DO NOT MIX OTHER MANUFACTURERS' PRODUCT LINES WITH THE REQUIRED MATERIALS. PRODUCTS LISTED IN THIS BULLETIN HAVE SHOWN THE REQUIRED REPAIR DURABILITY, AND CURRENTLY ARE THE ONLY PAINT SYSTEMS THAT MEET GM SPECIFICATION 4350M-A336. Procedures 1. Remove wheels from vehicle. Tires may remain mounted on wheels. 2. Remove balance weights and mark their location on tire. 3. Wipe excess grease, etc. from wheels with wax and grease remover. 4. Have wheels plastic media blasted to remove clearcoat. FOR FURTHER INFORMATION ON MEDIA BLASTING IN YOUR AREA, CALL US TECHNOLOGIES INC., CONTACT DAVE ROSENBURG AT 1-800-634-9185. Caution: IT IS MANDATORY THAT ADEQUATE RESPIRATORY PROTECTION BE WORN. EXAMPLES OF SUCH PROTECTION ARE: AIR LINE RESPIRATORS WITH FULL HOOD OR HALF MASK. IF NOT AVAILABLE, USE A VAPOR/PARTICULATE RESPIRATOR THAT RESPIRATOR MANUFACTURER RECOMMENDS AS EFFECTIVE FOR ISOCYANATE VAPOR AND MISTS (UNLESS LOCAL REGULATIONS PREVAIL). 5. Painting Process a. Refer to Attachments 1-3 for each System's individual formula and process. b. After following the specific System's individual formula and process, follow these steps: 6. Unmask wheels. 7. Clean all wheel mounting surface of any corrosion, overspray, or dirt. 8. Install new coated balance weights, at marked locations. 9. Replace wheels on vehicle. 10. USE A TORQUE STICK ON AN IMPACT WRENCH, OR A TORQUE WRENCH TO CONSISTENTLY AND UNIFORMLY FASTEN THE WHEEL TO THE SPECIFIED TORQUE FOR THE VEHICLE. THE STAR PATTERN MUST BE FOLLOWED. Important: TORQUE STICKS MUST BE USED ANY TIME AN IMPACT WRENCH IS USED TO TIGHTEN WHEEL NUTS. Warranty Information For vehicles repaired under warranty, use as shown. Attachment 1 - DuPont Products Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 531703A > May > 96 > Aluminum Wheels Refinishing > Page 10039 Painting Process System: Dupont Products Paint Color Information: Corsican Silver WA EQ9283 Dupont # C9143, Sparkle Silver WA9967 Dupont # C9339 1. Wipe wheel with cleaning solvent: 3939-S, 3949-S or 3900-S. 2. Mask off tires. Important: 3. Mask off all wheel mounting surfaces and wheel mount surfaces. 4. Apply two coats of 615/616-S etching primer to wheel allowing 10 minutes flash between coats. Allow to dry for 30 minutes before applying primer coat. 5. Apply URO 5000 primer 1220/193-S + accelerator 389-S using two coats at 65-70 PSI at the gun. Allow 12-15 minutes between coats. Force bake 30 minutes at 140°F (60°C). 6. Scuff sand using green Scotch-Brite pad. 7. Solvent wipe before top coating. 8. Apply IMRON 6000 base coat to wheel. 2-3 coats to hiding at 60-70 PSI allowing to flash between coats. Base coat needs to dry 20-30 minutes before clearcoat is applied. 9. Apply 3440-S clearcoat to wheel using two coats at 60-70 PSI. Flash 10-15 minutes between coats. 389-S can be used in basecoat and clearcoat to give faster set up times. 10. Allow overnight dry before reassemble. Can be baked for 30 minutes at 140°F (60°C). Attachment 2 - PPG Products Painting Process: PPG System Paint Color Information: Corsican Silver WAEQ9283; PPG # DBC-3531, Sparkle Silver WA9967; PPG # 35367 1. Wash entire wheel with aluminum cleaner DX533, mix 1:3 with water. Allow to react 2-3 minutes and rinse thoroughly. 2. Wash entire wheel with aluminum conditioner DX5O3 straight from the container. Allow to react 2-3 minutes until pale gold or tan color develops. Rinse thoroughly and dry. 3. Mask off tires. Important: 4. Mask off all wheel nut mounting surfaces and wheel mounting surfaces. 5. Apply 1-2 coats of DP Primer and allow to flash for 15-20 minutes. 6. Apply 2-3 coats of Deltron Basecoat (DBC) and allow to flash 20 minutes after the final coat. 7. Apply two (2) wet coats of Concept 2001 Acrylic urethane. 8. Flash 20 minutes and bake 140°F (60°C) for 30 minutes. For more information contact your PPG Jobber. Attachment 3 - Spies Hecker Painting Process: Spies Hecker System Paint Color Information: Corsican Silver AWEQ9283; SH-72913, Sparkle Silver WA9967; SH-71912 1. Clean with Permahyd Silicone Remover 7090. 2. Mask off tires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheels > Component Information > Technical Service Bulletins > All Other Service Bulletins for Wheels: > 531703A > May > 96 > Aluminum Wheels Refinishing > Page 10040 Important: 3. Mask off all wheel nut mounting surfaces and wheel mounting surfaces. 4. Apply 1-1/2 coats of Permahyd 1:1 Primer 4070. Mix 1:1 with Permahyd Hardener 3070 as per TDS. 5. Allow to flash for 30 minutes. 6. Apply two (2) coats of Permahyd 2:1 Surfacer 5080. Mix 2:1 with Permahyd Hardener 3071 as per TDS. 7. Bake for 60 minutes at 140°F (60°C) or allow to flash for 3 hours at 68°F (20°C). 8. Apply Permahyd Base Coat Series 280/285 as per TDS. 9. Allow to flash 10 to 15 minutes. 10. Apply 1 to 2 coats of Permacron High Solid Clear Coat 8060 as per TDS. 11. Allow to flash 10 minutes. Then bake at 140°F (60°C) for 40 minutes. For more information, contact your SPIES HECKER Jobber. We believe these sources and their products to be reliable. There may be additional manufacturers of such products. General Motors does not endorse, indicate any preference for or assume any responsibility for the products or equipment from these firms or for any such items which may be available from other sources. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheel Bearing > Component Information > Adjustments > Front Wheel Bearing: Adjustments Front FRONT WHEEL BEARINGS ADJUSTMENT Fig. 5 Hub, knuckle & bearing components. REMOVE 1. Raise and support vehicle. 2. Remove wheel cover, if equipped. 3. Remove cap from hub/disc assembly. 4. Remove cotter pin. 5. Tighten nut (12), Fig. 5, to 12 ft lbs, while turning wheel forward by hand. This will seat the bearing. 6. Loosen nut (12) to a just loose position, then back nut off until hole in the spindle aligns with a slot in the nut. Do not back the nut off more than 1/2 flat. INSTALL 1. New cotter pin. With wheel bearing properly adjusted, there will be .001---.005 inch endplay. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheel Bearing > Component Information > Adjustments > Front > Page 10045 Wheel Bearing: Adjustments Rear Dana/Spicer Full Floating Axle REAR WHEEL BEARINGS ADJUSTMENT Ensure the brakes are completely released and do not drag. Check wheel bearing play by grasping the tire at the top and pulling and pushing back and forth, or by using a pry bar under the tire. If the wheel bearings are properly adjusted, movement of the brake drum in relation to the brake flange plate will be barely noticeable and the wheel will turn freely. If the movement is excessive, adjust the bearings as follows: 1. Back off attaching nut until just loose, but not more than one slot of the lock or the axle spindle using wheel bearing nut wrench tool No. J-2222-C or equivalent. 2. Align adjusting nut slot with keyway in the axle spindle. Rockwell Full Floating Axle REAR WHEEL BEARINGS ADJUSTMENT Ensure the brakes are completely released and do not drag. Check wheel bearing play by grasping the tire at the top and pulling and pushing back and forth, or by using a pry bar under the tire. If the wheel bearings are properly adjusted, movement of hub or disc will be barely noticeable. If the movement is excessive, adjust the bearings as follows: 1. Raise and support vehicle. 2. Remove axle shaft. 3. Remove retaining nut and lock washer. 4. Using nut wrench tool No. J-25510, or equivalent, torque adjusting nut, with hub rotating, to 50.0 ft. lbs. Ensure bearing surfaces are in contact, then back adjusting nut off 1/8 turn. 5. Install lock washer, the bend tang over flat of adjusting nut. 6. Install retaining nut and torque to 250 ft. lbs. 7. Install axle shaft. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheel Bearing > Component Information > Service and Repair > Front Wheel Bearing: Service and Repair Front FRONT WHEEL BEARINGS AND/OR HUB Fig. 5 Hub, knuckle & bearing components. REMOVE 1. Disconnect battery ground cable. 2. Raise and support vehicle, then remove brake caliper. 3. Remove cap from hub/disc assembly, Fig. 5. 4. Remove cotter pin, nut and washer. 5. Remove hub/disc from spindle. 6. Remove outer bearing, seal, inner bearing and cup. INSTALL 1. Reverse procedure to install. Note the following: a. Clean all components before installing. b. Apply an approved high temperature front wheel bearing grease to the spindle at the inner and outer bearing seat, shoulder and seal seat. Also finger apply a small amount of grease inboard of each bearing cup in the hub/disc assembly. Pressure pack the bearings with a grease machine or hand pack them. Ensure grease is worked thoroughly into the rollers, cone and cage. c. When installing inner bearing, apply an additional quantity of grease outboard of the inner bearing. d. Torque nut (12) 10-12 ft lbs while turning the wheel assembly forward by hand. Apply grease to the outboard side of the outer bearing. Adjust wheel bearings. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheel Bearing > Component Information > Service and Repair > Front > Page 10048 Wheel Bearing: Service and Repair Rear REAR WHEEL BEARINGS 1. Raise and support vehicle. 2. Remove axle shaft. 3. Remove hub and drum. 4. Remove oil seal, inner bearing and retaining ring. 5. Remove outer bearing. 6. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheel Hub > Component Information > Service and Repair Wheel Hub: Service and Repair FRONT HUB/BEARING Fig. 5 Hub, knuckle & bearing components. REMOVE 1. Disconnect battery ground cable. 2. Raise and support vehicle, then remove brake caliper. 3. Remove cap from hub/disc assembly, Fig. 5. 4. Remove cotter pin, nut and washer. 5. Remove hub/disc from spindle. 6. Remove outer bearing, seal, inner bearing and cup. INSTALL 1. Reverse procedure to install. Note the following: a. Clean all components before installing. b. Apply an approved high temperature front wheel bearing grease to the spindle at the inner and outer bearing seat, shoulder and seal seat. Also finger apply a small amount of grease inboard of each bearing cup in the hub/disc assembly. Pressure pack the bearings with a grease machine or hand pack them. Ensure grease is worked thoroughly into the rollers, cone and cage. c. When installing inner bearing, apply an additional quantity of grease outboard of the inner bearing. d. Torque nut (12) 10-12 ft lbs while turning the wheel assembly forward by hand. Apply grease to the outboard side of the outer bearing. Adjust wheel bearings. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheel Fastener > Component Information > Technical Service Bulletins > Customer Interest for Wheel Fastener: > 01-03-10-009A > Jul > 04 > Wheels - Plastic Wheel Nut Covers Loose/Missing Wheel Fastener: Customer Interest Wheels - Plastic Wheel Nut Covers Loose/Missing Bulletin No.: 01-03-10-009A Date: July 27, 2004 TECHNICAL Subject: Plastic Wheel Nut Covers Missing and/or Loose (Replace Missing Covers and Add Sealant to All Covers) Models: 2005 and All Prior Passenger Cars (Except All Cadillac Models and Pontiac GTO) with Plastic Wheel Nut Covers Supercede: This bulletin is being revised to add additional models years. Please discard Corporate Bulletin Number 01-03-10-009. Condition Some customers may comment that the plastic wheel nut covers are missing and/or loose. Correction Important: ^ DO NOT USE a silicone-based adhesive. ^ Do not apply the *permatex(R) around the threads in a circular pattern. ^ Apply a single bead across the threads approximately 10 mm (0.4 in) in length, 5 mm (0.2 in) in height and 5 mm (0.2 in) in width. Replace any missing plastic wheel nut covers with the appropriate covers and apply Permatex(R) # 2 Form A Gasket Sealant(R) to the threads of all the plastic wheel nut covers. Tighten finger tight plus a 1/4 turn with a hand wrench. *We believe this source and their products to be reliable. There may be additional manufacturers of such material. General Motors does not endorse, indicate any preference for or assume any responsibility for the products from this firm or for any other such items which may be available from other sources. Permatex(R) # 2 Form A Gasket Sealant(R) part numbers (available at your local parts supplier) ^ P/N 80009 (2A/2AR) - 44 ml (1.5 oz) tube boxed ^ P/N 80015 (2AR) - 44 ml (1.5 oz) tube carded ^ P/N 80010 (2B/2BR) - 89 ml (3 oz) tube boxed ^ P/N 80016 (2BR) - 89 ml (3 oz) tube carded ^ P/N 80011 (2C) - 325 ml (11 oz) tube boxed Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheel Fastener > Component Information > Technical Service Bulletins > Customer Interest for Wheel Fastener: > 01-03-10-009A > Jul > 04 > Wheels - Plastic Wheel Nut Covers Loose/Missing > Page 10060 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheel Fastener > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheel Fastener: > 01-03-10-009A > Jul > 04 > Wheels Plastic Wheel Nut Covers Loose/Missing Wheel Fastener: All Technical Service Bulletins Wheels - Plastic Wheel Nut Covers Loose/Missing Bulletin No.: 01-03-10-009A Date: July 27, 2004 TECHNICAL Subject: Plastic Wheel Nut Covers Missing and/or Loose (Replace Missing Covers and Add Sealant to All Covers) Models: 2005 and All Prior Passenger Cars (Except All Cadillac Models and Pontiac GTO) with Plastic Wheel Nut Covers Supercede: This bulletin is being revised to add additional models years. Please discard Corporate Bulletin Number 01-03-10-009. Condition Some customers may comment that the plastic wheel nut covers are missing and/or loose. Correction Important: ^ DO NOT USE a silicone-based adhesive. ^ Do not apply the *permatex(R) around the threads in a circular pattern. ^ Apply a single bead across the threads approximately 10 mm (0.4 in) in length, 5 mm (0.2 in) in height and 5 mm (0.2 in) in width. Replace any missing plastic wheel nut covers with the appropriate covers and apply Permatex(R) # 2 Form A Gasket Sealant(R) to the threads of all the plastic wheel nut covers. Tighten finger tight plus a 1/4 turn with a hand wrench. *We believe this source and their products to be reliable. There may be additional manufacturers of such material. General Motors does not endorse, indicate any preference for or assume any responsibility for the products from this firm or for any other such items which may be available from other sources. Permatex(R) # 2 Form A Gasket Sealant(R) part numbers (available at your local parts supplier) ^ P/N 80009 (2A/2AR) - 44 ml (1.5 oz) tube boxed ^ P/N 80015 (2AR) - 44 ml (1.5 oz) tube carded ^ P/N 80010 (2B/2BR) - 89 ml (3 oz) tube boxed ^ P/N 80016 (2BR) - 89 ml (3 oz) tube carded ^ P/N 80011 (2C) - 325 ml (11 oz) tube boxed Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheel Fastener > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wheel Fastener: > 01-03-10-009A > Jul > 04 > Wheels Plastic Wheel Nut Covers Loose/Missing > Page 10066 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheel Fastener > Component Information > Technical Service Bulletins > Page 10067 Wheel Fastener: Specifications Wheel Stud Nut Wheel Stud Nut Vehicles with 5 Lugs 140 ft.lb Vehicles with 6 Lugs 140 ft.lb Vehicles with 8 Lugs 140 ft.lb Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Steering and Suspension > Wheels and Tires > Wheel Seal > Component Information > Service and Repair Wheel Seal: Service and Repair Fig. 5 Hub, knuckle & bearing components. REMOVE 1. Disconnect battery ground cable. 2. Raise and support vehicle, then remove brake caliper. 3. Remove cap from hub/disc assembly, Fig. 5. 4. Remove cotter pin, nut and washer. 5. Remove hub/disc from spindle. 6. Remove outer bearing, seal, inner bearing and cup. INSTALL 1. Reverse procedure to install. Note the following: a. Clean all components before installing. b. Apply an approved high temperature front wheel bearing grease to the spindle at the inner and outer bearing seat, shoulder and seal seat. Also finger apply a small amount of grease inboard of each bearing cup in the hub/disc assembly. Pressure pack the bearings with a grease machine or hand pack them. Ensure grease is worked thoroughly into the rollers, cone and cage. c. When installing inner bearing, apply an additional quantity of grease outboard of the inner bearing. d. Torque nut (12) 10-12 ft lbs while turning the wheel assembly forward by hand. Apply grease to the outboard side of the outer bearing. Adjust wheel bearings. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Accumulator HVAC > Component Information > Description and Operation Accumulator HVAC: Description and Operation OPERATION The sealed accumulator assembly connects to the evaporator outlet pipe. It functions as a liquid/vapor separator that receives refrigerant vapor, some liquid refrigerant and refrigerant oil from the evaporator. It only allows refrigerant vapor and oil to flow to the compressor. At the bottom of the accumulator is desiccant that acts as a drying agent for moisture that may have entered the system. An oil bleed hole is also located near the bottom of the accumulator outlet pipe to provide an oil return path to the compressor. A low-side pressure service fitting is located on the accumulator. A similar service fitting is provided for mounting the cycling pressure switch. It is not necessary to discharge the system to replace the switch. The accumulator is serviced only as a replacement assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Accumulator HVAC > Component Information > Description and Operation > Page 10075 Accumulator HVAC: Service and Repair Accumulator Tool Required: J 38042 Dual ORing Tube Separator Remove or Disconnect 1. Negative battery cable. 2. Recover refrigerant. 3. Electrical connectors, as necessary. 4. Pressure cycling switch. 5. Refrigerant hose from accumulator using J 38042. 6. Accumulator from the evaporator using J 38042. 7. O-ring seals from accumulator. Important Cap or plug all open connections. 8. Accumulator bracket screw. 9. Accumulator. 10. Upper and lower accumulator insulators. Install or Connect 1. Upper and lower accumulator insulators. 2. Accumulator. 3. Accumulator bracket screw. Tighten screw to 6 Nm (53 lb in). 4. New O-ring seals. - Coat O-ring seals with 525 viscosity refrigerant oil. 5. Accumulator to the evaporator.Tighten Accumulator to 41 Nm (30 lb ft). 6. Refrigerant hose to accumulator. Tighten Hose to 41 Nm (30 lb ft). 7. Pressure cycling switch. 8. Electrical connectors, as necessary. 9. Negative battery cable. 10. Charge system. - Check system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Conditioning Switch > Component Information > Locations > Auxiliary Heater Control Switch, Rear Air Conditioning Switch: Locations Auxiliary Heater Control Switch, Rear I/P, Right of Steering Column Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Conditioning Switch > Component Information > Locations > Auxiliary Heater Control Switch, Rear > Page 10080 Air Conditioning Switch: Locations Rear Auxiliary Heater Control Switch in Headliner Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Conditioning Switch > Component Information > Locations > Auxiliary Heater Control Switch, Rear > Page 10081 Air Conditioning Switch: Locations Rear Auxiliary Heater/A/C Fan Switch in Headliner Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Conditioning Switch > Component Information > Diagrams > Heater and A/C Control Switch Air Conditioning Switch: Diagrams Heater and A/C Control Switch C1: Heater And A/C Control Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Conditioning Switch > Component Information > Diagrams > Heater and A/C Control Switch > Page 10084 C3: Heater And A/C Control Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Conditioning Switch > Component Information > Diagrams > Heater and A/C Control Switch > Page 10085 C300: Rear Body HARN To AUX. A/C Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Conditioning Switch > Component Information > Diagrams > Heater and A/C Control Switch > Page 10086 C401: Rear Body HARN To AUX A/C Switch HARN Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Door, HVAC > Air Door Actuator / Motor, HVAC > Component Information > Locations > Rear Auxiliary Mode Door Motor Air Door Actuator / Motor: Locations Rear Auxiliary Mode Door Motor in Headliner Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Door, HVAC > Air Door Actuator / Motor, HVAC > Component Information > Locations > Rear Auxiliary Mode Door Motor > Page 10092 Air Door Actuator / Motor: Locations Rear Auxiliary Temperature Door Motor In Auxiliary Heater A/C Module, forward of LH rear Wheelhouse Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Door, HVAC > Air Door Actuator / Motor, HVAC > Component Information > Locations > Rear Auxiliary Mode Door Motor > Page 10093 Heater And Air Conditioning Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Door, HVAC > Air Door Actuator / Motor, HVAC > Component Information > Locations > Rear Auxiliary Mode Door Motor > Page 10094 Heater And Air Conditioning Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Door, HVAC > Air Door Actuator / Motor, HVAC > Component Information > Locations > Rear Auxiliary Mode Door Motor > Page 10095 Air Door Actuator / Motor: Locations Temperature Actuator Mode Actuator Replacement The temperature actuator is located in the passenger compartment of the vehicle, on the front of the heater case. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Door, HVAC > Air Door Actuator / Motor, HVAC > Component Information > Service and Repair > Temperature Actuator Removal and Installation Air Door Actuator / Motor: Service and Repair Temperature Actuator Removal and Installation Temperature Actuator Location Temperature Actuator Replacment Remove or Disconnect 1. Negative battery cable. 2. Roll instrument panel forward. 3. Electrical connector. 4. Screws. 5. Actuator. Adjust A. Electrical connector to the actuator. B. Turn the ignition key to the run position and let the actuator position itself. C. Turn off the ignition key. D. Remove the actuator from the electrical connector. Install or Connect 1. Actuator. 2. Screws. 3. Electrical connectors. 4. Instrument panel compartment. 5. Negative battery cable. ^Check circuit operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Door, HVAC > Air Door Actuator / Motor, HVAC > Component Information > Service and Repair > Temperature Actuator Removal and Installation > Page 10098 Air Door Actuator / Motor: Service and Repair Actuator Removal and Installation Mode Actuator Location Mode Actuator Replacement Remove or Disconnect 1. Negative battery cable. 2. Electrical connector. 3. Screws. 4. Adjuster links from control lever. 5. Mode actuator. Adjust A. Electrical connector to the actuator. B. Turn the ignition key to the run position and let the actuator position itself. C. Turn off the ignition key. D. Remove the actuator from the electrical connection. Install or Connect 1. Mode actuator. 2. Screws. 3. Adjuster links to control lever. 4. Electrical connector. 5. Negative battery cable. ^Check circuit operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Door, HVAC > Air Door Cable, HVAC > Component Information > Service and Repair Air Door Cable: Service and Repair Remove or Disconnect 1. Instrument cluster trim plate. 2. Control assembly. 3. Electrical connector. 4. Defrost cable from the control assembly. 5. Defrost cable from the defroster valve. Install or Connect 1. Index the cable before installing. A. Cycle the mode rotary knob to "HEATER." B. Make sure the defrost door is closed. 2. Cable to the defrost valve. A. Snap the cable onto the valve. B. Secure the cable by snapping the cable into the heater case. 3. Defrost cable to the control assembly. - Route the cable in the same location as removed. 4. Electrical connector. 5. Control assembly. 6. Instrument cluster trim plate. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Duct > Component Information > Technical Service Bulletins > Customer Interest for Air Duct: > 86-11-04 > Mar > 98 > Windshield, Driver Side - Insufficient Defrosting Air Duct: Customer Interest Windshield, Driver Side - Insufficient Defrosting File In Section: 1 - HVAC Bulletin No.: 86-11-04 Date: March, 1998 Subject: Insufficient Driver Side Windshield Clearing in Defrost Mode (Replace Air Distribution Duct Assembly) Models: 1995-96 Chevrolet and GMC C/K Models Condition Some owners may comment that windshield clearing on the driver's side while in the defrost mode is not up to their expectations. Cause Airflow from the defroster grille outlet effectively clears the windshield and meets all manufacturer's and federal standards. However, to better meet customer expectations, design changes have been made to enhance airflow and clearing. Correction Replace the air distribution duct assembly using the part number listed. Use the Service Procedure in Section 1A of the Service Manual. Parts Information P/N Description Qty 15002895 Duct Asm. - Air 1 Distribution Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time D1506 Duct, Air Use Published Distribution Outlet - Labor Operation R&R; or Replace Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Duct > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Air Duct: > 86-11-04 > Mar > 98 > Windshield, Driver Side - Insufficient Defrosting Air Duct: All Technical Service Bulletins Windshield, Driver Side - Insufficient Defrosting File In Section: 1 - HVAC Bulletin No.: 86-11-04 Date: March, 1998 Subject: Insufficient Driver Side Windshield Clearing in Defrost Mode (Replace Air Distribution Duct Assembly) Models: 1995-96 Chevrolet and GMC C/K Models Condition Some owners may comment that windshield clearing on the driver's side while in the defrost mode is not up to their expectations. Cause Airflow from the defroster grille outlet effectively clears the windshield and meets all manufacturer's and federal standards. However, to better meet customer expectations, design changes have been made to enhance airflow and clearing. Correction Replace the air distribution duct assembly using the part number listed. Use the Service Procedure in Section 1A of the Service Manual. Parts Information P/N Description Qty 15002895 Duct Asm. - Air 1 Distribution Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time D1506 Duct, Air Use Published Distribution Outlet - Labor Operation R&R; or Replace Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Duct > Component Information > Technical Service Bulletins > Page 10115 Air Duct: Description and Operation PURPOSE A one-piece air distributor duct directs air to the passenger compartment. It attaches to the instrument panel with snap-in style retainers and three screws. In case of poor air output, check the air distributor duct for obstructions such as leaves, dirt, or objects that may have fallen into it from the passenger compartment. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Duct > Component Information > Service and Repair > With Air Conditioning Air Duct: Service and Repair With Air Conditioning Air Distributor Duct Remove or Disconnect 1. Negative battery cable. 2. Instrument panel bezel. 3. Radio. 4. Roll instrument panel back. 5. Duct mounting screws. - Squeeze the retainer in the component carrier compartment to release the duct. 6. Duct from instrument panel. Install or Connect 1. Duct to instrument panel. 2. Duct mounting screws. Tighten screws to 1.9 Nm (17 lb in). 3. Roll instrument panel forward. 4. Radio. 5. Instrument panel bezel. 6. Negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Air Duct > Component Information > Service and Repair > With Air Conditioning > Page 10118 Air Duct: Service and Repair W/O Air Conditioner Air Distributor Duct Remove or Disconnect 1. Instrument cluster trim plate. 2. Defroster grille. 3. Three duct mounting screws. 4. Tilt back instrument panel assembly. 5. Duct from instrument panel by squeezing to release retainers in three places. 6. Duct from the instrument panel. Install or Connect 1. Duct to instrument panel. 2. Tilt up instrument panel. 3. Duct mounting screws. Tighten Screws to 1.9 Nm (17 lbs. in.). 4. Defroster grille. 5. Instrument cluster trim plate. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > Customer Interest for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates Blower Motor: Customer Interest A/C - Odor at Start up in Humid Climates File In Section: 1 - HVAC Bulletin No.: 53-12-12A Date: December, 1996 Subject: Air Conditioning Odor at Start Up in Humid Climates (Disinfect Evaporator Core, Install Delayed Blower Control Package) Models: 1993-96 Passenger Cars (Except GEO) 1993-96 Light Duty Models (Except Tracker) This bulletin is being revised to update the wiring diagrams, add the Corvette (with RPO C60) and delete medium/heavy duty trucks. Please discard Corporate Bulletin Number 53-12-12 (Section 1 HVAC). Condition Some owners may comment on odors emitted from the air conditioning system, primarily at start up in hot, humid climates. Cause This odor may be the result of microbial growth on the evaporator core. When the blower motor fan is turned on, the microbial growth may release an unpleasant musty odor into the passenger compartment. Correction To remove odors of this type, it is necessary to eliminate the microbial growth and prevent its recurrence. To accomplish this, these two procedures must be completed. ^ Deodorize the evaporator core using Deodorizing Aerosol Kit, P/N 12377951 (AC Delco 15-102). ^ Install the new A/C Delayed Blower Control Package, P/N 12370470, (AC Delco 15-8632). The blower control package will enable the blower to run at high speed for five (5) minutes. It will do so approximately fifty (50) minutes after the ignition has been turned off if the compressor had been engaged for four (4) or more minutes prior to shutting off engine. By doing so, the evaporator case and core are dried out, reducing the chances of a recurring A/C odor. Procedure 1. Visually inspect the air conditioning evaporator drain hose for obstructions or working condition. 2. Apply deodorizing aerosol as described in the instructions supplied with the kit. Once the deodorizer has been applied, some of the mixture may overflow from the drain hose. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > Customer Interest for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10127 3. The chart identifies specific instructions for each vehicle. This chart will identify the proper deodorizing procedure, template and wiring diagram. Deodorizing the evaporator case can easily be done by removing the blower motor resistor and tape off opening. The nozzle can now be inserted through a pierced hole in the tape to deodorize the evaporator case. For some of the vehicles specified below, a drilling procedure is identified in the deodorizing instructions. This type of alternative procedure and others can be done by using the referenced templates in the chart. 4. Complete detailed installation instructions are supplied with the blower control package. Important: A. 1996 ONLY (Use blower resistor location for drilling procedure) B. 1994-1996 ONLY Refer to appropriate Service Manual for enabling afterblow feature through on-board diagnostics. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > Customer Interest for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10128 For vehicles repaired under warranty, use as shown. Figure 1 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > Customer Interest for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10129 Figure 2 Figure 3 Figure 4 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > Customer Interest for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10130 Figure 5 Figure 6 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > Customer Interest for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10131 Figure 7 Figure 8 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > Customer Interest for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10132 Figure 9 Figure 10 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > Customer Interest for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10133 Figure 11 Figure 12 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > Customer Interest for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10134 Figure 13 Figure 14 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > Customer Interest for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10135 Figure 15 Figure 16 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > Customer Interest for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10136 Figure 17 Figure 18 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > Customer Interest for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10137 Figure 19 Figure 20 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > Customer Interest for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10138 Figure 21 Figure 22 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > Customer Interest for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10139 Figure 23 Figure 24 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > Customer Interest for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10140 Figure 25 Figure 26 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > Customer Interest for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10141 Figure 27 Figure 28 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > Customer Interest for Blower Motor: > 661103 > Jul > 96 > A/C - Fan Only Operates on High Speed Blower Motor: Customer Interest A/C - Fan Only Operates on High Speed File In Section: 1 - HVAC Bulletin No.: 66-11-03 Date: July, 1996 Subject: HVAC Fan Only Operates on High Speed (Replace Blower Motor Resistor Assembly) Models: 1995-96 Chevrolet and GMC C/K Models Built before the VIN breakpoints as shown. Condition Some owners may comment that the HVAC fan will operate only on high speed setting. Cause The blower motor resistor fails open. Correction Replace blower motor resistor assembly with new part, following the service procedure in Section 1B of the appropriate C/K Truck Service Manual. Parts Information P/N Description Qty 15024815 Resistor Asm - Blower Motor 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time D1002 Resistor, Blower Use Published Labor Motor - Replace Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates Blower Motor: All Technical Service Bulletins A/C - Odor at Start up in Humid Climates File In Section: 1 - HVAC Bulletin No.: 53-12-12A Date: December, 1996 Subject: Air Conditioning Odor at Start Up in Humid Climates (Disinfect Evaporator Core, Install Delayed Blower Control Package) Models: 1993-96 Passenger Cars (Except GEO) 1993-96 Light Duty Models (Except Tracker) This bulletin is being revised to update the wiring diagrams, add the Corvette (with RPO C60) and delete medium/heavy duty trucks. Please discard Corporate Bulletin Number 53-12-12 (Section 1 HVAC). Condition Some owners may comment on odors emitted from the air conditioning system, primarily at start up in hot, humid climates. Cause This odor may be the result of microbial growth on the evaporator core. When the blower motor fan is turned on, the microbial growth may release an unpleasant musty odor into the passenger compartment. Correction To remove odors of this type, it is necessary to eliminate the microbial growth and prevent its recurrence. To accomplish this, these two procedures must be completed. ^ Deodorize the evaporator core using Deodorizing Aerosol Kit, P/N 12377951 (AC Delco 15-102). ^ Install the new A/C Delayed Blower Control Package, P/N 12370470, (AC Delco 15-8632). The blower control package will enable the blower to run at high speed for five (5) minutes. It will do so approximately fifty (50) minutes after the ignition has been turned off if the compressor had been engaged for four (4) or more minutes prior to shutting off engine. By doing so, the evaporator case and core are dried out, reducing the chances of a recurring A/C odor. Procedure 1. Visually inspect the air conditioning evaporator drain hose for obstructions or working condition. 2. Apply deodorizing aerosol as described in the instructions supplied with the kit. Once the deodorizer has been applied, some of the mixture may overflow from the drain hose. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10151 3. The chart identifies specific instructions for each vehicle. This chart will identify the proper deodorizing procedure, template and wiring diagram. Deodorizing the evaporator case can easily be done by removing the blower motor resistor and tape off opening. The nozzle can now be inserted through a pierced hole in the tape to deodorize the evaporator case. For some of the vehicles specified below, a drilling procedure is identified in the deodorizing instructions. This type of alternative procedure and others can be done by using the referenced templates in the chart. 4. Complete detailed installation instructions are supplied with the blower control package. Important: A. 1996 ONLY (Use blower resistor location for drilling procedure) B. 1994-1996 ONLY Refer to appropriate Service Manual for enabling afterblow feature through on-board diagnostics. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10152 For vehicles repaired under warranty, use as shown. Figure 1 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10153 Figure 2 Figure 3 Figure 4 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10154 Figure 5 Figure 6 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10155 Figure 7 Figure 8 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10156 Figure 9 Figure 10 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10157 Figure 11 Figure 12 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10158 Figure 13 Figure 14 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10159 Figure 15 Figure 16 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10160 Figure 17 Figure 18 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10161 Figure 19 Figure 20 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10162 Figure 21 Figure 22 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10163 Figure 23 Figure 24 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10164 Figure 25 Figure 26 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Blower Motor: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10165 Figure 27 Figure 28 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Blower Motor: > 661103 > Jul > 96 > A/C - Fan Only Operates on High Speed Blower Motor: All Technical Service Bulletins A/C - Fan Only Operates on High Speed File In Section: 1 - HVAC Bulletin No.: 66-11-03 Date: July, 1996 Subject: HVAC Fan Only Operates on High Speed (Replace Blower Motor Resistor Assembly) Models: 1995-96 Chevrolet and GMC C/K Models Built before the VIN breakpoints as shown. Condition Some owners may comment that the HVAC fan will operate only on high speed setting. Cause The blower motor resistor fails open. Correction Replace blower motor resistor assembly with new part, following the service procedure in Section 1B of the appropriate C/K Truck Service Manual. Parts Information P/N Description Qty 15024815 Resistor Asm - Blower Motor 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time D1002 Resistor, Blower Use Published Labor Motor - Replace Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Locations > Auxiliary Blower Motor Blower Motor: Locations Auxiliary Blower Motor rear side of Cabin area, behind rear Wheel House Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Locations > Auxiliary Blower Motor > Page 10172 Heater And Air Conditioning Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions Blower Motor: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10175 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10176 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10177 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10178 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10179 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10180 Blower Motor: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10181 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10182 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10183 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10184 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10185 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10186 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10187 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10188 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10189 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10190 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10191 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10192 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10193 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10194 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10195 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10196 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10197 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10198 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10199 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10200 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10201 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10202 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10203 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10204 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10205 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10206 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10207 Blower Motor: Electrical Diagrams Front Heater Blower, W/ A/C Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10208 Rear Auxiliary Blower, W/ A/C, W/ Heater Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10209 Rear Auxiliary Blower, W/ A/C W/O Heater (C69) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10210 Front Heater Blower, W/O A/C Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10211 Rear Auxiliary Heater Blower, W/O A/C (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Diagrams > Diagram Information and Instructions > Page 10212 Rear Auxiliary Heater Blower, W/O A/C (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Testing and Inspection > Blower Noise Diagnosis Blower Motor: Testing and Inspection Blower Noise Diagnosis A constant air rush noise is typical of high-speed blower operation. Some systems and modes may be noisier than others. If possible, check another similar vehicle to determine whether the noise is typical or excessive. Sit in the vehicle with the doors and windows closed. With the engine running, run the blower on "HIGH"speed with the temperature set for maximum cooling. Cycle through the blower speeds, modes, and temperature settings to find where the noise does not occur. Try to define the types of noise. - Noise is constant, but decreases with blower speed reduction. Typical noises are a whine, tick/click, flutter, or scrape. - Noise is only at start-up or intermittent. This noise may occur at cold ambients and low blower speeds. Typical noise is a squeal/screech. Noise is constant at high blower speeds in certain modes, but can be eliminated at lower blower speeds in other modes. Typical noises are a flutter or rumble. If the noise persists, remove the blower assembly and check for obstructions or foreign material causing noise and remove. If no obstructions are found and the noise is still heard, replace the blower assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Service and Repair > With Air Conditioning Blower Motor: Service and Repair With Air Conditioning Evaporator/ Heater Core Case Remove or Disconnect 1. Negative battery cable. 2. Instrument panel compartment. 3. Front screw from right door sill plate. 4. Right hinge pillar trim panel. 5. Electrical connectors from ECM, as necessary. 6. ECM and mounting bracket (diesel engines only). 7. Electrical connectors from blower motor (60), as necessary. 8. Bolt from right lower I/P support. 9. Blower motor cover. 10. Blower motor cooling tube. 11. Blower motor flange screws (59). 12. Blower motor (60). - Pull the blower motor forward carefully to avoid distorting the blower fan. - May be necessary to pry back right side of instrument panel. Inspect - Blower motor terminals for distortion. Clean corrosion from the terminals or replace the blower motor (60) as necessary. - Flange of the blower motor (60) for damage or distortion that could cause an air leak. Repair as necessary. - Blower fan for damage and distortion. Install or Connect 1. Blower motor (60). - Guide the blower motor and blower fan into position, being careful not to catch the blower fan on protruding parts. 2. Blower motor flange screws (59). 3. Blower motor cooling tube. 4. Blower motor cover 5. Bolt to right lower I/P support. 6. Electrical connectors to blower motor (16), as necessary. 7. Mounting bracket and ECM. 8. Electrical connectors to ECM, as necessary. 9. Right hinge pillar trim panel. 10. Front screw into front door sill plate. 11. Instrument panel compartment. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Service and Repair > With Air Conditioning > Page 10217 12. Negative battery cable. - Check circuit operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Service and Repair > With Air Conditioning > Page 10218 Blower Motor: Service and Repair W/O Air Conditioning Heater Case (1 OF 2) Heater Case(2 OF 2) Remove or Disconnect 1. Negative battery cable. 2. Instrument panel storage compartment. 3. Front screw from right door sill plate. 4. Right hinge pillar trim panel. 5. Electrical connectors from blower motor, as necessary. 6. Bolt from right lower lip support. 7. Blower motor cover. 8. Blower motor cooling tube. 9. Blower motor flange screws. 10. Blower motor. ^ Pull the blower motor forward carefully to avoid distorting the blower fan. ^ May be necessary to pry back right side of instrument panel. Inspect - Blower motor terminals for distortion. Clean corrosion from the terminals or replace the blower motor as necessary. - Flange of the blower motor for damage or distortion that could cause an air leak. Repair as necessary. - Blower fan for damage and distortion. Install or Connect 1. Blower motor. - Guide the blower motor and blower fan into position, being careful not to catch the blower fan on protruding parts. 2. Blower motor flange screws. Tighten Blower motor flange screws to 1.4 Nm (12 lb in). 3. Blower motor cooling tube. 4. Blower motor cover. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor > Component Information > Service and Repair > With Air Conditioning > Page 10219 5. Bolt to right lower I/P support. 6. Electrical connectors to blower motor, as necessary. 7. Right hinge pillar trim panel. 8. Front screw into front door sill plate. 9. Instrument panel storage compartment. 10. Negative battery cable. - Check circuit operation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor Relay > Component Information > Locations > Blower Motor Relay High Front Blower Motor Relay: Locations Blower Motor Relay High Front Behind I/P Compartment Box on HVAC Plenum Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor Relay > Component Information > Locations > Blower Motor Relay High Front > Page 10224 Blower Motor Relay: Locations Blower Relay High Heater And Air Conditioning Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor Relay > Component Information > Locations > Blower Motor Relay High Front > Page 10225 Auxiliary Heater And Air Conditioning Wiring, Rear Under I/P, on top of HVAC Plenum Auxiliary Heater And Air Conditioning Wiring, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor Relay > Component Information > Locations > Blower Motor Relay High Front > Page 10226 Auxiliary Heater And Air Conditioning Wiring, Rear Medium Rear On Auxiliary Heater and A/C Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor Relay > Component Information > Locations > Page 10227 High Blower Relay Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor Relay > Component Information > Locations > Page 10228 Blower Motor Relay: Service and Repair 1 Screw, 2 Resistor, 3 Relay Bracket, 4 Relay Remove or Disconnect 1. Negative battery cable. 2. Instrument panel compartment. 3. Electrical connectors, as necessary. 4. Relay from relay bracket. Install or Connect 1. Relay to relay bracket. 2. Electrical connectors, as necessary. 3. Instrument panel compartment. 4. Negative battery cable. - Check circuit operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor Resistor > Component Information > Technical Service Bulletins > Customer Interest for Blower Motor Resistor: > 661103 > Jul > 96 > A/C - Fan Only Operates on High Speed Blower Motor Resistor: Customer Interest A/C - Fan Only Operates on High Speed File In Section: 1 - HVAC Bulletin No.: 66-11-03 Date: July, 1996 Subject: HVAC Fan Only Operates on High Speed (Replace Blower Motor Resistor Assembly) Models: 1995-96 Chevrolet and GMC C/K Models Built before the VIN breakpoints as shown. Condition Some owners may comment that the HVAC fan will operate only on high speed setting. Cause The blower motor resistor fails open. Correction Replace blower motor resistor assembly with new part, following the service procedure in Section 1B of the appropriate C/K Truck Service Manual. Parts Information P/N Description Qty 15024815 Resistor Asm - Blower Motor 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time D1002 Resistor, Blower Use Published Labor Motor - Replace Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor Resistor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Blower Motor Resistor: > 661103 > Jul > 96 > A/C - Fan Only Operates on High Speed Blower Motor Resistor: All Technical Service Bulletins A/C - Fan Only Operates on High Speed File In Section: 1 - HVAC Bulletin No.: 66-11-03 Date: July, 1996 Subject: HVAC Fan Only Operates on High Speed (Replace Blower Motor Resistor Assembly) Models: 1995-96 Chevrolet and GMC C/K Models Built before the VIN breakpoints as shown. Condition Some owners may comment that the HVAC fan will operate only on high speed setting. Cause The blower motor resistor fails open. Correction Replace blower motor resistor assembly with new part, following the service procedure in Section 1B of the appropriate C/K Truck Service Manual. Parts Information P/N Description Qty 15024815 Resistor Asm - Blower Motor 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time D1002 Resistor, Blower Use Published Labor Motor - Replace Operation Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor Resistor > Component Information > Locations > Blower Resistor Auxiliary Heater And Air Conditioning Wiring, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor Resistor > Component Information > Locations > Blower Resistor > Page 10244 Heater And Air Conditioning Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor Resistor > Component Information > Service and Repair > With Air Conditioning Blower Motor Resistor: Service and Repair With Air Conditioning 1 Screw, 2 Resistor, 3 Relay Bracket, 4 Relay Remove or Disconnect 1. Negative battery cable. 2. Roll instrument panel back. 3. Plenum tray. 4. Electrical connectors, as necessary. 5. Screws. 6. Blower motor resistor. Install or Connect 1. Blower motor resistor. 2. Tighten screws to 1.9 Nm (17 lb in). 3. Electrical connectors, as necessary. 4. Plenum tray. 5. Roll instrument panel forward. 6. Negative battery cable. - Check circuit operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor Resistor > Component Information > Service and Repair > With Air Conditioning > Page 10247 Blower Motor Resistor: Service and Repair W/O Air Conditioning Blower Motor Resistor REMOVE OR DISCONNECT 1. Negative battery cable. 2. Roll instrument panel back. 3. Plenum tray. 4. Electrical connector. 5. Screws. 6. Resistor. INSTALL OR CONNECT NOTE: When installing resistor to the heater case, do not let the resistor coils contact each other. Improper system operation or vehicle damage could result. 1. Resistor. 2. Tighten Screws to 1.9 Nm (17 lb in). 3. Electrical connector. 4. Plenum tray. 5. Roll instrument panel forward. 6. Negative battery cable. - Check circuit operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor Switch > Component Information > Locations > Aux Fan Control Switch C227: TCC/Stop Lamp Switch Jumper, AUX Fan Control Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor Switch > Component Information > Locations > Aux Fan Control Switch > Page 10252 Blower Motor Switch: Locations Fan Switch, Front At heater control. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor Switch > Component Information > Locations > Aux Fan Control Switch > Page 10253 Cargo Lamp Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor Switch > Component Information > Locations > Page 10254 C2: Heater Blower Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor Switch > Component Information > Service and Repair > With Air Conditioning Blower Motor Switch: Service and Repair With Air Conditioning Control Assembly Remove or Disconnect 1. Instrument cluster trim. 2. Control assembly. - Release the retainers using a small screwdriver, then pull the control assembly out from the instrument panel. 3. Electrical connectors, as necessary. Install or Connect 1. Electrical connectors, as necessary. 2. Control assembly. - The control assembly snap-fits to the instrument panel. 3. Instrument cluster trim. Check circuit operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Blower Motor Switch > Component Information > Service and Repair > With Air Conditioning > Page 10257 Blower Motor Switch: Service and Repair W/O Air Conditioning Control Assembly Replacment Remove or Disconnect 1. Instrument cluster trim plate. 2. Control assembly by releasing the snap-fit retainers with a small screwdriver. 3. Electrical connection. 4. Cables from the control assembly by releasing retainers. 5. Blower switch. Remove the blower switch rotary knob and the retaining clip from the shaft of the blower switch. Install or Connect 1. Blower switch. A. Hold the blower switch in position and install the retaining clip. B. Install the blower switch rotary knob. 2. Cables to the control assembly. 3. Electrical connection. 4. Control assembly to the instrument panel by snapping in. 5. Instrument cluster trim plate. Check circuit operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Clutch > Component Information > Specifications Compressor Clutch: Specifications Clutch Plate & Rotor ............................................................................................................................ ................................... 0.50-0.76mm (0.020-0.030") Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Clutch > Component Information > Specifications > Page 10262 Compressor Clutch: Locations Front of A/C Compressor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Clutch > Component Information > Specifications > Page 10263 Compressor Clutch: Service and Repair Clutch Plate And Hub Assembly Removal Remove or Disconnect 1. Clamp the holding fixture J 33026 in a vise and attach compressor to holding fixture with thumb screws J 330261. 2. With center Screw forcing tip in place to thrust against the end of the shaft, thread the Clutch Plate and Hub Assembly Installer-Remover J 33013-B into the hub. Hold the body of the remover with a wrench and turn the center screw into the remover body to remove the clutch plate and hub assembly. NOTICE: Do not drive or pound on the clutch hub or shaft. Internal damage to compressor may result. The forcing tip on J 33013-B remover-installer center screw must be flat or the end of the shaft/axial plate assembly will be damaged. 3. Remove the shaft key and retain for reassembly. Shaft Key, Clutch Plate/Hub Installation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Clutch > Component Information > Specifications > Page 10264 Installing Clutch Plate & Hub Assembly Removing Pulley Rotor And Bearing Assembly Install or Connect 1. Install the shaft key into the hub key groove. Allow the key to project approximately 3.2mm (1/8") out of the keyway. The shaft key is curved slightly to provide an interference fit in the hub key groove. 2. Be sure the frictional surface of the clutch plate and the clutch rotor are clean before installing the clutch plate and hub assembly. 3. Align the shaft key with the shaft keyway and place the clutch plate and the hub assembly onto the compressor shaft. 4. Remove the forcing tip on J 33013-B clutch plate and hub assembly installer-remover center screw and reverse the body direction on the center screw, as shown in the illustration. 5. Install the clutch plate and hub installer-remover J 33013-B with bearing as shown in the illustration. The body of the J 33013-B installer-remover should be backed off sufficiently to allow the center screw to be threaded onto the end of the compressor shaft. 6. Hold the center screw with a wrench. Tighten the hex portion of the installer-remover J 33013-B body to press the hub onto the shaft. Tighten the body several turns, remove the installer and check to see that the shaft key is still in place In the keyway before Installing the clutch plate and hub assembly to its final position. The air gap between frictional surfaces of the clutch plate and clutch rotor should be 0.50-0.76mm (0.020-0.030"). NOTICE: If the center screw is threaded fully onto the end of the compressor shaft. or if the body of the installer is held and the center screw is rotated, the key will wedge and will break the clutch hub. 7. Remove installer J 33013-B, check for proper positioning of the shaft key (even or slightly above the clutch hub). 8. Spin the pulley rotor by hand to see that the rotor is not rubbing the clutch drive plate. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Clutch Bearing > Component Information > Locations Compressor Components - Disassembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Clutch Bearing > Component Information > Locations > Page 10268 Compressor Clutch Bearing: Service and Repair Installing - Removing Pulley Rotor & Bearing Assembly Retaining Ring Remove or Disconnect 1. Remove the clutch plate and hub assembly as described previously. 2. Remove rotor and bearing assembly retaining ring, using snap ring pliers J 6083. Installing Pulley Rotor/Bearing Puller Guide Removing Pulley Rotor And Bearing Assembly 3. Install pulley rotor and bearing puller guide J 33023-A to the front head and install J 41552 pulley rotor and bearing puller down into the inner circle of slots in the rotor. Turn the J 41552 puller clockwise in the slots in the rotor. 4. Hold the J 41552 puller in place and tighten the puller screw against the puller guide to remove the pulley rotor and bearing assembly. 5. To prevent damage to the pulley rotor during bearing removal the rotor hub must be properly supported. Remove the forcing screw from J 41552 puller and, with the puller tangs still engaged in the rotor slots, invert the assembly onto a solid flat surface or blocks as shown. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Clutch Bearing > Component Information > Locations > Page 10269 6. Drive the bearing out of the rotor hub with rotor bearing remover J 9398-A and J 29886 universal handle. NOTICE: It is not necessary to remove the staking in front of the bearing to remove the bearing, however, it will be necessary to file away the old stake metal for proper clearance for the new bearing to be installed into the rotor bore or the bearing may be damaged. Install or Connect 1. Place the pulley rotor on the J 21352-A support block to fully support the rotor hub during bearing installation. NOTICE: DO NOT support the rotor by resting the pulley rim on a flat surface during the bearing installation or the rotor face will be bent. 2. Align the new bearing squarely with the hub bore and using puller and bearing installer J 9481-A with universal handle J 29886, drive the bearing fully into the hub. The installer will apply force to the outer race of the bearing, if used as shown. 3. Place bearing staking guide J 33019-1 and bearing staking pin J 33019-2 in the hub bore as shown. Shift the rotor and bearing assembly on the J 21352-A support block to give full support of the hub under the staking pin location. A heavy duty rubber band may be used to hold the stake pin in the guide, and the stake pin should be properly positioned in the guide after each impact on the pin. 4. Using care to prevent personal injury, strike the staking pin with a hammer until a metal stake, similar to the original, is formed down to but not Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Clutch Bearing > Component Information > Locations > Page 10270 touching the bearing. Noisy bearing operation and reduced bearing life may result if outer bearing race is deformed while staking, The stake metal should not contact the outer race of the bearing. Stake three places 120 degrees apart as shown. 5. With the compressor mounted to the J 33026 holding fixture, position the rotor and bearing assembly on the front head. 6. Position the J 33017 pulley, rotor and bearing installer and J 33023-A puller pilot directly over the inner race of the bearing. 7. Position puller crossbar J 8433-1 on the puller pilot J 33023-A and assemble the two J 33026-2 through bolts and washers through the puller bar slots and thread them into the J 33026 holding fixture. The thread of the through bolts should engage the full thickness of the holding fixture. 8. Tighten the center screw in the J 8433-1 puller crossbar to force the pulley rotor and bearing assembly onto the compressor front head. Should the J 33017 pulley rotor and bearing installer slip off direct in-line contact with the inner race of the bearing, loosen the J 8433-1 center forcing screw and realign the installer and pilot so that the S 33017 installer will properly clear the front head. Installing - Removing Pulley Rotor & Bearing Assembly Retaining Ring 9. Install rotor and bearing assembly retainer ring, using snap ring pliers J 6083. 10. Reinstall clutch plate and hub assembly as described previously. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Clutch Coil > Component Information > Locations Compressor Components - Disassembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Clutch Coil > Component Information > Locations > Page 10274 Compressor Clutch Coil: Service and Repair Installing - Removing Pulley Rotor & Bearing Assembly Retaining Ring Remove and Disconnect 1. Remove the clutch plate and hub assembly as described previously. 2. Remove rotor and bearing assembly retaining ring, using snap ring pliers J 6083. Installing Pulley Rotor/Bearing Puller Guide Removing Pulley Rotor And Bearing Assembly 3. Install pulley rotor and bearing puller guide J 33023-A to the front head and install J 41552 pulley rotor and bearing puller down into the inner circle of slots in the rotor. Turn the J 41552 puller clockwise in the slots in the rotor. 4. Hold the J 41552 puller in place and tighten the puller screw against the puller guide to remove the pulley rotor and bearing assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Clutch Coil > Component Information > Locations > Page 10275 Clutch Coil Assembly Removal 5. Mark clutch coil terminal location on compressor front head. 6. Install J 33023-A puller pilot on front head of compressor. Also install J 8433-1 pull crossbar with J 33025 puller legs as shown. 7. Tighten J 8433-3 forcing screw against the puller pilot remove the clutch coil. Install or Connect 1. Place the clutch coil assembly on the front head with the terminals positioned at the "marked" location. 2. Place the J 33024 clutch coil installer over the internal opening of the clutch coil housing and align install with the compressor front head. Installing Clutch Coil Assembly 3. Center the J 8433-1 puller crossbar in the counter-sunk center hole of the J 33024 clutch coil installer. Install J 33026-2 through bolts and washers through the crossbar slots and thread them into the holding fixture J 33026 to full fixture thickness. 4. Turn the center forcing screw of the J 8433-1 pull crossbar to force the clutch coil onto the front head. Be sure clutch coil and J 33024 installer stay "in-line during installation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Clutch Coil > Component Information > Locations > Page 10276 Staking Clutch Coil To Front Head 5. When coil is fully seated on the front head, use a 1/8" diameter drift punch and stake the front head at three places 120 degrees apart, to ensure clutch coil remains in position. Details Of Stakes In Front Head For Clutch Coil - Stake size should be only one-half the area of the punch tip and be only approximately 0.28-0.35mm (.010.015") deep. 6. Install rotor and bearing assembly and the clutch plate and hub assembly as described previously. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Clutch Hub > Component Information > Specifications Compressor Clutch Hub: Specifications Clutch Plate & Rotor ............................................................................................................................ ................................... 0.50-0.76mm (0.020-0.030") Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Clutch Hub > Component Information > Specifications > Page 10280 Compressor Components - Disassembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Clutch Hub > Component Information > Specifications > Page 10281 Compressor Clutch Hub: Service and Repair Clutch Plate And Hub Assembly Removal Remove or Disconnect 1. Clamp the holding fixture J 33026 in a vise and attach compressor to holding fixture with thumb screws J 330261. 2. With center screw forcing tip in place to thrust against the end of the shaft, thread the Clutch Plate and Hub Assembly Installer-Remover J 33013-B into the hub. Hold the body of the remover with a wrench and turn the center screw into the remover body to remove the clutch plate and hub assembly. NOTE: Do not drive or pound on the clutch hub or shaft. Internal damage to compressor may result. The forcing tip on J 33013-B remover-installer center screw must be flat or the end of the shaft/axial plate assembly will be damaged. 3. Remove the shaft key and retain for reassembly. Shaft Key, Clutch Plate/Hub Installation Install or Connect 1. Install the shaft key into the hub key groove. Allow the key to project approximately 3.2mm (1/8") out of the keyway. The shaft key is curved slightly to provide an interference fit in the hub key groove. 2. Be sure the frictional surface of the clutch plate and the clutch rotor are clean before installing the clutch plate and hub assembly. 3. Align the shaft key with the shaft keyway and place the clutch plate and the hub assembly onto the compressor shaft. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Clutch Hub > Component Information > Specifications > Page 10282 Installing Clutch Plate & Hub Assembly 4. Remove the forcing tip on J 33013-B clutch plate and hub assembly installer-remover center screw and reverse the body direction on the center screw. Removing Pulley Rotor And Bearing Assembly 5. Install the clutch plate and hub installer-remover J 33013-B with bearing as shown. The body of the J 33013-B installer-remover should be backed off sufficiently to allow the center screw to be threaded onto the end of the compressor shaft. 6. Hold the center screw with a wrench. Tighten the hex portion of the installer-remover J 33013-B body to press the hub onto the shaft. Tighten the body several turns, remove the installer and check to see that the shaft key is still in place In the keyway before Installing the clutch plate and hub assembly to its final position. The air gap between frictional surfaces of the clutch plate and clutch rotor should be 0.50-0.76mm (0.020-0.030 in.). NOTE: If the center screw is threaded fully onto the end of the compressor shaft. or if the body of the installer is held and the center screw is rotated, the key will wedge and will break the clutch hub. 7. Remove installer J 33013-B, check for proper positioning of the shaft key (even or slightly above the clutch hub). 8. Spin the pulley rotor by hand to see that the rotor is not rubbing the clutch drive plate. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Shaft Seal > Component Information > Technical Service Bulletins > A/C Compressor Seal Washer - Reference Chart Compressor Shaft Seal: Technical Service Bulletins A/C Compressor Seal Washer - Reference Chart File In Section: 1 - HVAC Bulletin No.: 63-12-15 Date: November, 1996 INFORMATION Subject: Reference Chart for A/C Compressor Seal Washers Models: 1997 and Prior Passenger Cars (Except Corvette and GEO) 1997 and Prior Light Duty Trucks (Except Tracker) GMSPO A/C compressors include a seal washer kit. These kits contain various color edge painted washer seals and inserts in which only two (2) washers and possibly one (1) insert are used. It has come to our attention that some packaging discrepancies were found and some of the seals cannot be properly identified for installation. These seals are very close in size and some of the seals were inadvertently edge painted the wrong color or not painted. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Shaft Seal > Component Information > Technical Service Bulletins > A/C Compressor Seal Washer - Reference Chart > Page 10287 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Shaft Seal > Component Information > Technical Service Bulletins > A/C Compressor Seal Washer - Reference Chart > Page 10288 The chart shown will help to properly identify the seals. Use the chart by placing the seal over the pictured seal to identity inside and outside diameters and thickness. Because these seals are very similar in size, specifications are also listed in the chart. Important: If seals are damaged upon installation, obtain new seal kit. Seals will be available separately at a later date. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Shaft Seal > Component Information > Technical Service Bulletins > Page 10289 Compressor Components - Disassembly Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Shaft Seal > Component Information > Technical Service Bulletins > Page 10290 Compressor Shaft Seal: Testing and Inspection 1. Blow shop air behind and in front of the compressor clutch/pulley for at least 15 seconds. 2. Wait 1-2 minutes. 3. Probe the area in front of the pulley. If the detector goes to a solid alarm, a leak has been found. 5. If possible, visually inspect the core face with a flashlight for evidence of refrigerant oil. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Shaft Seal > Component Information > Technical Service Bulletins > Page 10291 Compressor Shaft Seal: Service and Repair Removing Or Installing Shaft Seal Retaining Ring Removing Or Installing Shaft Seal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Shaft Seal > Component Information > Technical Service Bulletins > Page 10292 Removing And Installing Shaft Seal And O-Ring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor HVAC > Compressor Shaft Seal > Component Information > Technical Service Bulletins > Page 10293 Compressor Shaft Seal Seal Leak Detection A shaft seal should not be changed because of small amounts of oil found on an adjacent surface but only after actual refrigerant leakage is found using an approved leak detector, J 39400 or equivalent. Remove or Disconnect 1. Recover the refrigerant using J 39500-GM. 2. Loosen and reposition compressor in mounting brackets, if necessary. 3. Remove clutch plate and hub assembly from compressor as described in minor repairs. 4. Remove the shaft seal retainer ring, using snap ring pliers J 5403. 5. Thoroughly clean inside of compressor neck area surrounding the shaft, the exposed portion of the seal, the retainer ring groove and the shaft itself. Any dirt or foreign material getting into compressor may cause damage. 6. Fully engage the knurled tangs of Seal Remover-Installer J 23128-A into the recessed portion of the Seal by turning the handle clockwise. Remove the Seal from the compressor with a rotary-pulling motion. Discard the seal. The handle must be hand-tightened securely. Do not use a wrench or pliers. 7. Remove and discard the seal seat O-ring from the compressor neck using O-ring remover J 9553-01. 8. Recheck the shaft and inside of the compressor neck for dirt or foreign material and be sure these areas are perfectly clean before installing new parts. Clean - Thoroughly clean O-ring seal groove in front head. NOTICE: Seals should not be re-used. Always use a new specification service seal on rebuild. Be sure that the seal to he installed is not scratched or damaged in anyway. Make sure that the seal seat and seal are free of lint and dirt that could damage the seal surface or prevent sealing. Install or Connect 1. Dip the new seal seat O-ring in clean 525 viscosity refrigerant oil and assemble onto O-ring installer J 33011. 2. Insert the O-ring installer J 33011 into the compressor neck until the installer "bottoms." Lower the moveable slide of the O-ring installer to release the O-ring into the seal O-ring lower groove. (The compressor neck top groove is for the shaft seal retainer ring.) Rotate the installer to seat the O-ring and remove the installer. 3. Dip the new seal in clean 525 viscosity refrigerant oil and assemble seal to Seal Installer J 23128-A, by turning handle clockwise. The stamped steel case side of the lip seal must he engaged with knurled tangs of installer so that flared-out side of lip seal is facing and installed towards the compressor. Install seal protector J 34614, in the seal lip and place over the compressor shaft, and push the seal in place with a rotary motion or place the seal protector J 34014 over end of compressor shaft, and slide the new seal onto the shaft with a rotary motion until it stops. Take care not to dislodge the O-ring. Be sure the seal makes good contact with the O-ring. Disengage the installer from the seal and remove the installer J 23128-A and the seal protector J 34614. NOTICE: Handling and care of seal protector is important. If seal protector is nicked or the bottom flared, the new seal may be damaged during installation. 4. Install the new seal retainer ring with its flat side against the Seal, using Snap-Ring Pliers J 5403. See illustration. Use the sleeve from O-ring installer J 33011 to press in on the seal retainer ring so that it snaps into its groove. 5. To leak test, install compressor leak test fixture J 39893 on rear head of compressor and connect gage charging lines and J 39500-GM Refrigerant Recovery System. Pressurize suction and high-side of compressor with R-134a Refrigerant. Temporarily install (M9 x 1.25 thread on shaft) nut and, with the compressor in horizontal position, rotate the compressor shaft in normal direction of rotation several turns by hand. Leak test the seal area and correct and leak found. Recover the refrigerant. Remove shaft nut. 6. Remove any excess oil resulting from installing the new seal parts from the shaft and inside the compressor neck. 7. Install the clutch plate and hub assembly as described in minor repair procedures. 8. Reinstall compressor belt and tighten bracket. 9. Evacuate and charge the refrigerant system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor Clutch Relay > Component Information > Locations Underhood Fuse-Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Compressor Fitting HVAC > Component Information > Service and Repair Compressor Fitting HVAC: Service and Repair Sealing Washer Installation (1 OF 2) Important - When installing sealing washers, keep dirt and foreign material from getting on the sealing surfaces of the washers, hose block, or compressor ports. Clean all sealing surfaces with a lint-free rag. - Do not reuse sealing washers. - Sealing washers do not have to be oiled prior to assembly. Sealing Washer Installation (2 OF 2) Install or Connect 1. Install sealing washer onto pilots of suction/discharge block fitting. Washers must "bottom" against surface of block fitting. 2. Install hose block to the compressor. Make sure the sealing washers are seated within the compressor machined surfaces. 3. Hold block in place, hand tighten bolt. Tighten Bolt to 34 Nm (25 lb ft). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Condenser HVAC > Component Information > Description and Operation Condenser HVAC: Description and Operation PURPOSE The condenser assembly in front of the radiator consists of coils, that carry the refrigerant, and cooling fins, that provide rapid transfer of heat. Air passing through the condenser cools the high-pressure refrigerant vapor causing it to condense into a liquid. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Condenser HVAC > Component Information > Description and Operation > Page 10303 Condenser HVAC: Service and Repair Condenser Assembly REMOVE OR DISCONNECT 1. Recover refrigerant. 2. Grille. 3. Hood primary latch support. 4. Auxiliary cooling fan, if equipped. 5. Refrigerant hose from condenser. 6. Evaporator tube from condenser. ^ Cap or plug all open connections. 7. Bolts. 8. Brackets. 9. Upper insulators. 10. Condenser. - Bend the left grille support outboard to gain clearance for the condenser removal. 11. Lower insulators. INSTALL OR CONNECT 1. Lower insulators. 2. Condenser. Refer to Refrigerant Oil Distribution, if replacing condenser. 3. Upper insulators. 4. Brackets. 5. Tighten Bolts to 4.5 Nm (40 lb in). 6. Evaporator tube to condenser. 7. Refrigerant hose to condenser. 8. Auxiliary cooling fan, if equipped. 9. Hood primary latch support. 10. Grille. 11. Charge system. 12. Check system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Technical Service Bulletins > Customer Interest: > 76-11-01 > Oct > 97 > A/C - Control Knob Spins Freely Control Assembly: Customer Interest A/C - Control Knob Spins Freely File In Section: 1 - HVAC Bulletin No.: 76-11-01 Date: October, 1997 Subject: HVAC Control Knob Spins Freely (Replace all Three Knobs) Models: 1996-97 Chevrolet and GMC M/L and G Vans 1995-97 Chevrolet and GMC C/K Trucks Condition Some customers may report that one or more HVAC Control Knobs spin freely, resulting in loss of fan, temperature and/or mode operation. Cause The knob's plastic inner shaft may crack when forced against its stop. Correction If any one of the three HVAC control knobs exhibits this condition, replace all three knobs with new P/N 16268157. Parts Information P/N Description Qty 16268157 Knob, HVAC Control 3 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time D0100 Knobs, Control Assy, 0.2 hr Replace Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Technical Service Bulletins > All Technical Service Bulletins: > 76-11-01 > Oct > 97 > A/C - Control Knob Spins Freely Control Assembly: All Technical Service Bulletins A/C - Control Knob Spins Freely File In Section: 1 - HVAC Bulletin No.: 76-11-01 Date: October, 1997 Subject: HVAC Control Knob Spins Freely (Replace all Three Knobs) Models: 1996-97 Chevrolet and GMC M/L and G Vans 1995-97 Chevrolet and GMC C/K Trucks Condition Some customers may report that one or more HVAC Control Knobs spin freely, resulting in loss of fan, temperature and/or mode operation. Cause The knob's plastic inner shaft may crack when forced against its stop. Correction If any one of the three HVAC control knobs exhibits this condition, replace all three knobs with new P/N 16268157. Parts Information P/N Description Qty 16268157 Knob, HVAC Control 3 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time D0100 Knobs, Control Assy, 0.2 hr Replace Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Technical Service Bulletins > All Other Service Bulletins for Control Assembly: > 99-05-24-001A > Sep > 99 > Brakes Lead/Pull & Front Brake Wear Brake Shoe: All Technical Service Bulletins Brakes - Lead/Pull & Front Brake Wear File In Section: 05 - Brakes Bulletin No.: 99-05-24-001A Date: September, 1999 TECHNICAL Subject: Brake Lead/Pull and Front Brake Wear (Replace Front Brake Pads and/or Rear Brake Shoes) Models: 1992-99 Chevrolet and GMC C/K Cab Chassis, Crew Cab, and Pickup Models with Power Brakes (RPO JB8) 1992-99 Chevrolet and GMC C/K Suburban Models with 8600 # GVW (RPO C6P) 1996-2000 Chevrolet and GMC G Vans with Power Brakes (RPO JD7 & JB8) and GVW's of 7,700 # up to 9,500 # (RPO's C3F, C6P, & E23) This bulletin is being revised to update information in the Models Section and Correction Information. Please discard Corporate Bulletin Number 99-05-24-001 (Section 5 - Brakes). Condition Some owners may comment about the vehicle leading or pulling to either side while applying the brakes, and premature front brake wear, especially vehicles that have been used to tow a heavy load. Cause The condition may be caused by wearing of the front brake material. Improvements to the above conditions can be gained through brake material modifications. On the Suburban models, the best performance from this new brake material can be achieved with replacing the brake combination valve. Correction Replace the rear brake shoes with P/N 18029651. THIS FIX DOES NOT APPLY TO THE 13 x 2-1/2 BRAKE, DURASTOP(TM) P/N 18029650, OR ANY OTHER SIZE. On Suburban models, a brake combination valve must be replaced. ALL OTHER MODELS (C/K, G Van), NO BRAKE COMBINATION VALVE CHANGE IS REQUIRED. Refer to the Drum Brakes or Hydraulic Brakes subsection of the appropriate Service Manual. For G2/G3 Series Vans only (with GVW's of 7,700 # up to 9,500 # - RPOs C3F, C6P, E23) also replace the front brakes pads with P/N 12471685. Refer to the Disc Brake subsection of the appropriate Service Manual. Important: The new front brake pad material has been selected for improved wear characteristics. Some customers may experience increased brake noise from this brake pad and should be advised that some squeal is a characteristic of this particular material. Important: If you encounter disc brakes that are extremely worn on the inboard side, with very little wear to the outboard side, verify the clearance between the caliper and the steering knuckle bracket stops. MEASURE THE CLEARANCES INDIVIDUALLY AND ADD THE CLEARANCES TOGETHER FOR TOTAL CLEARANCE BEFORE REMOVING THE CALIPER. If the caliper (total clearance) to the steering knuckle stops is under 0.26 mm (0.010 in), correct this by filing metal off at the steering knuckle stops in order to obtain a total clearance of 0.26 to 0.60 mm (0.010 to 0.024 in). DO NOT FILE METAL OFF OF THE CALIPER. Refer to the Disc Brake subsection of the appropriate Service Manual for additional information on this procedure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Technical Service Bulletins > All Other Service Bulletins for Control Assembly: > 99-05-24-001A > Sep > 99 > Brakes Lead/Pull & Front Brake Wear > Page 10322 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Technical Service Bulletins > All Other Service Bulletins for Control Assembly: > 99-05-24-001A > Sep > 99 > Brakes Lead/Pull & Front Brake Wear > Page 10328 Parts Information Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Locations > Auxiliary System Control Assembly: Locations Auxiliary System Overhead Console Auxiliary Heater and A/C Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Locations > Auxiliary System > Page 10331 Overhead Console Control Modules are attached to Control Assemblies. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Locations > Auxiliary System > Page 10332 Control Assembly: Locations Main System HVAC Control Panel & Module Control Module is attached to Control Assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions Control Assembly: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10335 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10336 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10337 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10338 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10339 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10340 Control Assembly: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10341 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10342 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10343 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10344 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10345 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10346 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10347 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10348 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10349 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10350 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10351 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10352 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10353 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10354 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10355 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10356 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10357 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10358 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10359 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10360 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10361 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10362 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10363 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10364 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10365 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10366 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10367 Control Assembly: Connector Views Auxiliary Heater And A/C Control Logic Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10368 Auxiliary Heater And A/C Control Module, Front Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Diagrams > Diagram Information and Instructions > Page 10369 Auxiliary Heater And A/C Control Module (Rear) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Description and Operation > Blower Controls Control Assembly: Description and Operation Blower Controls Front Blower Controls Battery Voltage is supplied at all times to Front High Blower Relay Pin A2 through the RED (542) wire. When the ignition Switch is OFF or the Front Blower Switch at the Heater Control Module or Heater and A/C Control Module is OFF, no Voltage is applied to the Relay Coil through the ORN (52) wire and the Relay remains de-energized. Similarly, no Voltage is applied to the normally closed contact at Pin B2 of the Relay. Battery Voltage is not applied to the Front Blower Motor and it does not operate at any speed. When the Ignition Switch is in RUN and the Front Blower Switch is in LO, Voltage is applied through all three Blower Resistors to the normally closed contact in the Relay. The Relay remains de-energized. Reduced Voltage is applied to the Front Blower Motor through the PPL (65) wire and the Motor operates at its slowest speed. With the Front Blower Switch in either M1 or M2, current flows through fewer resistors in the Front Blower Resistor and the Front Blower Motor runs faster. With the Front Blower Switch in HI, the Blower Resistors are bypassed by the energizing of the Front High Blower Relay. The contacts change state and Battery Voltage from the Underhood Fuse-Relay Center is applied directly to the Motor. The Front Blower Motor then operates at it's fastest speed. Rear Auxiliary Blower Controls (Heater W/O A/C) Battery Voltage is supplied when the Ignition Switch is in RUN to Relay Coil Pin 5 of each of the three Rear Blower Relays through the BRN (341) wire. Battery Voltage is also supplied when the Ignition Switch is in RUN to Pin 1 of each of the three Rear Blower Relays through the RED (542) wire. With the Rear Auxiliary Heater Control Switch in OFF, no grounding path is provided for the Relay Coils and the Relays remain de-energized. The Relay contacts remain open and no Voltage is supplied to the Rear Blower Motor. When the Ignition Switch is in RUN and the Rear Auxiliary Heater Control Switch is in LO, a ground path is provided for the Rear Low Blower Relay Coil through the DK BLU (1926) wire to the Control Switch then through BLK (150) wire to Ground G200. The Relay Coil energizes and the Relay contacts close. This applies Battery Voltage to the Rear Blower Resistor through the YEL (1176) wire. Current flows through two resistors and to the Rear Blower Motor through the YEL (1172) wire. The Motor operates at its slowest speed. When the Rear Auxiliary Heater Control Switch is in MED, the Rear Medium Blower Relay is energized. Current flow's to the Motor through one resistor and the Motor operates at an intermediate speed. When the Rear Auxiliary Heater Control Switch is in HI, the Rear High Blower Relay is energized. Current bypasses both resistors and the Motor operates at its highest speed. An illumination lamp is provided at the Rear Auxiliary Heater Control Switch to facilitate Switch operations. The lamp is powered by the Instrument Panel Dimming system. Rear Auxiliary Blower Controls (Heater W/ A/C) The Rear Blower Motor is controlled by either of two Rear Blower Switches when optional rear auxiliary heating and air conditioning is provided. Both Switches are located in overhead modules, one over the Instrument Panel and the other in the center of the vehicle. The Rear Blower Motor will operate from the Rear Blower Switch at the Rear Auxiliary Heater and A/C Control Module only when the Rear Blower Switch at the Front Auxiliary Heater and A/C Control Module is in the REAR position. Refer to HVAC Air Delivery and Temperature Controls for a description of the control priorities for the ventilation modes. Battery Voltage is supplied when the Ignition Switch is in RUN to Relay Coil Pin 5 of each of the three Rear Blower Relays through the BRN (341) wires. Battery Voltage is also supplied when the Ignition Switch is in RUN to contact Pin 1 of each of the three Rear Blower Relays through the RED (542) wires. With the Rear Blower Switch at the Front Auxiliary Heater and A/C Control Module in OFF and with the Rear Blower Switch at the Rear Auxiliary Heater and A/C Control Module in OFF, no grounding path is provided for the Relay Coils and the Relays remain de-energized. The Relay contacts remain pen and no Voltage is supplied to the Rear Blower Motor. When the Ignition Switch is in RUN and the Blower Switch at the Front Module is in LO a ground path is provided for the Rear Low Blower Relay through the DK BLU (1925) wire to the Front Blower Switch then through BLK (150) wire to Ground G400. The Relay Coil energizes and the Relay contacts close. This applies Battery Voltage to the Rear Blower Resistor through the YEL (1176) wire. Current flows through two resistors and to the Rear Blower Motor through the YEL (1172) wire. The Motor operates at its slowest speed. When the Rear Blower Switch at the Front Heater and A/C Control Module is in REAR and the Rear Blower Switch at the Rear Heater and A/C Control Module is in LO, the grounding path is different. The ground path is through the DK BLU (1925) wire to the Rear Auxiliary Heater and A/C Control Module. The DK BLU (77) wire continues the ground path to the Auxiliary and Heater and A/C Control Logic Module. ORN (77) wire continues the ground path to the Front Auxiliary Heater and A/C Control Module where is continues to Ground G400. When the Rear Blower Switch is in MED, the Rear Medium Blower Relay is energized. Current flows to the Motor through one resistor and the Motor operates at an intermediate speed. When the Rear Blower Switch is in HI, the Rear High Blower Relay is energized. Current bypasses both resistors and the Motor operates at its highest speed. An illumination lamp is provided at each Heater and A/C Control Module to facilitate Switch operations. The lamps are powered by the Instrument Panel Dimming system. Rear Auxiliary Blower Controls (A/C W/O Heater) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Description and Operation > Blower Controls > Page 10372 The Circuit operation for the optional Rear Auxiliary Air Conditioning system is similar to that for the optional Rear Auxiliary Heating and Air Conditioning option. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Description and Operation > Blower Controls > Page 10373 Control Assembly: Description and Operation Control Assembly Description System Components OPERATION The air conditioning system is electronically controlled. Three backlit, rotary knobs provide full control of the system. These rotary knobs control blower speed, air temperature, and mode of operation. Two push-to-latch buttons select recirculation mode for maximum cooling and control over the air conditioning compressor. The blower speed rotary control has four fan speeds and an off position. When the blower fan is turned off, all HVAC operations turn off also. The air inlet door is automatically placed in the recirculation position by the recirculation actuator. The temperature rotary control has 180° of travel. A detent at the full cold-end of travel engages recirculation. Operating the system with the temperature control placed in this detent will result in maximum cooling. Air inside the passenger compartment will be recirculated through the blower case. Outside air use will be minimal. Recirculation can also be manually selected by pushing the "RECIRO" button. The mode rotary control has three major detents to indicate "VENT," "FLOOR," and "DEFROST' mode positions. Placing the control anywhere in between the major detents results in air output blending between the two modes. The recirculation mode is not available anytime "DEFROST' is selected, or while air is being blended out the defrost outlets. Automatic recirculation will occur when compressor head pressures exceed 2275 kPa (350 psi) and disable after head pressures reach 1724 kPa (250 psi). When activated, it cannot be manually disabled by the "MAX" button. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Service and Repair > With Air Conditioning Control Assembly: Service and Repair With Air Conditioning Control Assembly REMOVE OR DISCONNECT 1. Instrument cluster trim. 2. Control assembly. - Release the retainers using a small screwdriver, then pull the control assembly out from the instrument panel. 3. Electrical connectors, as necessary. INSTALL OR CONNECT 1. Electrical connectors, as necessary. 2. Control assembly. - The control assembly snap-fits to the instrument panel. 3. Instrument cluster trim. - Check circuit operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Assembly, HVAC > Component Information > Service and Repair > With Air Conditioning > Page 10376 Control Assembly: Service and Repair W/O Air Conditioning Control Assembly Replacment Remove Or Disconnect - Instrument cluster trim plate. - Control assembly by releasing the snap-fit retainers with a small screwdriver. - Electrical connection. - Cables from the control assembly by releasing retainers. - Blower switch. - Remove the blower switch rotary knob and the retaining clip from the shaft of the blower switch. Install Or Connect - Blower switch. Hold the blower switch in position and install the retaining clip. Install the blower switch rotary knob. - Cables to the control assembly. - Electrical connection. - Control assembly to the instrument panel by snapping in. - Instrument cluster trim plate. - Check Circuit Operation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Module HVAC > Component Information > Locations > Auxiliary System Control Module HVAC: Locations Auxiliary System Overhead Console Auxiliary Heater and A/C Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Module HVAC > Component Information > Locations > Auxiliary System > Page 10381 Overhead Console Control Modules are attached to Control Assemblies. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Control Module HVAC > Component Information > Locations > Auxiliary System > Page 10382 Control Module HVAC: Locations Blower Control Module HVAC Control Panel & Module Control Module is attached to Control Assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Coupler HVAC > A/C Coupler O-ring > Component Information > Description and Operation A/C Coupler O-ring: Description and Operation This vehicle uses GM's dual O-ring joint design in the system. This design increases the durability of the joint seal by providing a second O-ring seal. The dual O-ring design consists of: - An aluminum-alloy, externally threaded fitting which is brazed or welded to an aluminum tube. - A free-spinning, plated steel internally threaded nut. - A precision machined, male-piloted aluminum tube end which accommodates two O-rings. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Coupler HVAC > A/C Coupler O-ring > Component Information > Service and Repair > Dual O-Ring Seals A/C Coupler O-ring: Service and Repair Dual O-Ring Seals Tool Required: J 38042 Dual O-Ring Tube Separator When servicing the dual O-ring joint, the following procedure should be followed: - Completely recover refrigerant from system. - Use J 38042 dual O-ring tube separator to separate the joint while loosing the female nut. - Whenever a fitting joint is opened, replace the O-rings with new ones. - Use a nonmetallic tool when removing O-rings to prevent the chance of damaging the seal surface. - Avoid excessive stretching and twisting of replacement O-rings. - Align the end forms for pilot-to-bore insertion, then push together completely. - Dual O-ring fittings are different in size from standard A/C fitting O-rings. - Dual O-ring fittings require that the aluminum nut be tightened to a torque of 24 Nm (18 lb ft). Before installation, O-ring seals and fittings should be examined to make sure they have not been nicked or deformed. Replace nicked or deformed parts to prevent refrigerant leakage. Application of a small amount of 525 viscosity refrigerant oil will ease insertion. Important - Dual O-ring fittings are different in size from standard A/C fitting O-rings. - Dual O-ring fittings require that the aluminum nut be tightened to a torque of 24 Nm (18 lb ft). Before installation, O-ring seals and fittings should be examined to make sure they have not been nicked or deformed. Replace nicked or deformed parts to prevent refrigerant leakage. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Coupler HVAC > A/C Coupler O-ring > Component Information > Service and Repair > Dual O-Ring Seals > Page 10389 A/C Coupler O-ring: Service and Repair O-Ring Seals Coat air conditioning O-ring seals with 525 viscosity refrigerant oil just before installation. Slip them onto the flange tube to ensure proper locating and sealing. To prevent the possibility of swelling and a reduction in sealing effectiveness, do not soak O-ring seals in refrigerant oil. Before installation, O-ring seals and fittings should be examined to make sure they have not been nicked or deformed. Replace nicked or deformed parts to prevent refrigerant leakage. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Customer Interest: > 99-01-39-004C > Jun > 09 > A/C - Musty Odors Emitted From (HVAC) System Evaporator Core: Customer Interest A/C - Musty Odors Emitted From (HVAC) System TECHNICAL Bulletin No.: 99-01-39-004C Date: June 12, 2009 Subject: Air Conditioning Odor (Install Evaporator Core Dryer Kit and Apply Cooling Coil Coating) Models: 1993-2010 GM Passenger Cars and Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 All Equipped with Air Conditioning Supercede: This bulletin is being revised to add the 2009 and 2010 model years. Please discard Corporate Bulletin Number 99-01-39-004B (Section 01 - HVAC). Condition Some customers may comment about musty odors emitted from the Heating, Ventilation and Air Conditioning (HVAC) system at vehicle start-up in hot, humid conditions. Cause This condition may be caused by condensate build-up on the evaporator core, which does not evaporate by itself in high humidity conditions. The odor may be the result of microbial growth on the evaporator core. When the blower motor fan is turned on, the microbial growth may release an unpleasant musty odor into the passenger compartment. There are several other possible sources of a musty odor in a vehicle. A common source is a water leak into the interior of the vehicle or foreign material in the HVAC air distribution system. Follow the procedures in SI for identifying and correcting water leaks and air inlet inspection. The procedure contained in this bulletin is only applicable if the odor source has been determined to be microbial growth on the evaporator core inside the HVAC module. Correction Many vehicles currently incorporate an afterblow function within the HVAC control module software. The afterblow feature, when enabled, employs the HVAC blower fan to dry the evaporator after vehicle shut down and this function will inhibit microbial growth. Technicians are to confirm that the customer concern is evaporator core odor and that the vehicle has the imbedded afterblow feature, as defined in the SI document for that specific vehicle model, model year and specific HVAC option. Refer to SI for enabling the afterblow function. Vehicles being delivered in areas prone to high humidity conditions may benefit from having the afterblow enabled calibration installed prior to any customer comment. Important If the vehicle is not factory equipped with the imbedded afterblow enable feature, it may be added with the Electronic Evaporator Dryer Module Kit (P/N 12497910 or AC Delco 15-5876). Important When installing the Electronic Evaporator Dryer Module, you MUST use the included electrical splice connectors to ensure a proper splice. Complete detailed installation instructions and self testing procedures are supplied with the kit. If necessary, the Electronic Evaporator Dryer Module may be installed underhood if it is protected from extreme heat and water splash areas. To immediately remove the evaporator core odor on all suspect vehicles, it is necessary to eliminate the microbial growth and prevent its re-occurrence. To accomplish this, perform the following procedure: Vehicle and Applicator Tool Preparation 1. The evaporator core must be dry. This may be accomplished by disabling the compressor and running the blower fan on the recirc heat setting for an extended period of time. Note Compressor engagement will cause the evaporator core to remain wet and will prevent full adherence of the Coiling Coil Coating to the evaporator core surfaces. 2. Verify that the air conditioning drain hose is not clogged and place a drain pan beneath the vehicle. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Customer Interest: > 99-01-39-004C > Jun > 09 > A/C - Musty Odors Emitted From (HVAC) System > Page 10398 3. Place a protective cover over the carpet below the evaporator core. 4. Remove the cabin air filter, if equipped, and cover the opening prior to applying the Cooling Coil Coating, as the product may clog the filter. If the cabin air filter appears to have little or no remaining life, suggest a replacement to your customer. 5. If the HVAC module has a blower motor cooling tube, be careful NOT TO SPRAY THE COOLING COIL COATING INTO THE BLOWER MOTOR COOLING TUBE. 6. Attach the Flexible Applicator Pressure Spray Tool (J-43810-20A) to a compressed air line operating at 586 kPa (85 psi) to 793 kPa (115 psi). 7. Shake the bottle of Cooling Coil Coating well. Screw the bottle onto the cap on the applicator tool's pick-up tube. Note The pick-up tube is designed for 120 ml (4 oz) and 240 ml (8 oz) bottles and should coil slightly in the bottom of a 120 ml (4 oz) bottle. 8. Use one of the following three methods to apply the Cooling Coil Coating. Important If the Pressure Applicator Spray Tool (J-43810-20A) is not available, the Cooling Coil Coating is also available in an aerosol can (P/N 12377951 (in Canada, 10953503)). Application Through Blower Motor Control Module Opening - Remove the blower motor control module (blower motor resistor). Refer to the applicable procedure in SI. - Clean any debris or foreign material from inside the HVAC module and on the evaporator core surface. - Apply the Cooling Coil Coating directly to the evaporator core through the blower motor blower motor control module (blower motor resistor) opening. - Use the flexible wand to direct the Cooling Coil Coating over the entire evaporator core and surrounding gasket surfaces. - When the application is complete, install the blower motor blower motor control module (blower motor control module). Application Through Blower Motor Opening - Remove the blower motor. Refer to the applicable blower motor removal procedure in SI. - Clean any debris or foreign material from inside the HVAC module and on the evaporator core surface. - Apply the Cooling Coil Coating directly to the evaporator core through the blower motor opening. - Use the flexible wand to direct the Cooling Coil Coating over the entire evaporator core and surrounding gasket surfaces. - When the application is complete, install the blower motor. Application Through a Hole in the HVAC Module - If neither of the two previous application methods are available, it may be necessary to drill a hole in the HVAC module. - Locate an area of the HVAC module between the blower motor and the evaporator core. Drill a 10 mm (3/8 in) hole in the HVAC module. Use caution to keep the drill clear of the evaporator core and the blower motor fan. - With the air distribution vents closed and the blower motor fan speed on HIGH, insert the applicator tool into the hole and spray the Cooling Coil Coating into the airstream toward the evaporator core. - Use a GM approved RTV sealant to plug the hole in the HVAC module. 9. After the Cooling Coil Coating application is complete, start and run the vehicle for approximately 10 minutes, with the compressor disabled, HVAC mode set to Recirculate/Max, heat set to full warm, blower motor fan speed on high, and one window open approximately 12 mm (1/2 in). This cures the Cooling Coil Coating onto the evaporator core surface. 10. While the engine is running, rinse the applicator tool with warm water to prolong the life of the tool. Be sure to spray warm water through the nozzle to rinse out any residual Cooling Coil Coating still in the capillary pick up tube, otherwise it will dry and clog the applicator tool. Also remove the small green valve from the bottle cap and rinse it thoroughly while rolling it between two fingers and then reinstall it. If this valve is clogged , the Cooling Coil Coating will not flow through the applicator tool. 11. Shut off the engine and enable the compressor again. 12. Verify proper HVAC system operation. 13. Remove the protective cover from inside the vehicle. 14. Remove the drain pan from underneath the vehicle. 15. Reinstall the cabin air filter if necessary. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Customer Interest: > 99-01-39-004C > Jun > 09 > A/C - Musty Odors Emitted From (HVAC) System > Page 10399 Parts Information Important The Cooling Coil Coating listed below is the only GM approved product for use under warranty as an evaporator core disinfectant and for the long term control of evaporator core microbial growth. Warranty Information For vehicles repaired under warranty, use the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Customer Interest: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates Evaporator Core: Customer Interest A/C - Odor at Start up in Humid Climates File In Section: 1 - HVAC Bulletin No.: 53-12-12A Date: December, 1996 Subject: Air Conditioning Odor at Start Up in Humid Climates (Disinfect Evaporator Core, Install Delayed Blower Control Package) Models: 1993-96 Passenger Cars (Except GEO) 1993-96 Light Duty Models (Except Tracker) This bulletin is being revised to update the wiring diagrams, add the Corvette (with RPO C60) and delete medium/heavy duty trucks. Please discard Corporate Bulletin Number 53-12-12 (Section 1 HVAC). Condition Some owners may comment on odors emitted from the air conditioning system, primarily at start up in hot, humid climates. Cause This odor may be the result of microbial growth on the evaporator core. When the blower motor fan is turned on, the microbial growth may release an unpleasant musty odor into the passenger compartment. Correction To remove odors of this type, it is necessary to eliminate the microbial growth and prevent its recurrence. To accomplish this, these two procedures must be completed. ^ Deodorize the evaporator core using Deodorizing Aerosol Kit, P/N 12377951 (AC Delco 15-102). ^ Install the new A/C Delayed Blower Control Package, P/N 12370470, (AC Delco 15-8632). The blower control package will enable the blower to run at high speed for five (5) minutes. It will do so approximately fifty (50) minutes after the ignition has been turned off if the compressor had been engaged for four (4) or more minutes prior to shutting off engine. By doing so, the evaporator case and core are dried out, reducing the chances of a recurring A/C odor. Procedure 1. Visually inspect the air conditioning evaporator drain hose for obstructions or working condition. 2. Apply deodorizing aerosol as described in the instructions supplied with the kit. Once the deodorizer has been applied, some of the mixture may overflow from the drain hose. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Customer Interest: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10404 3. The chart identifies specific instructions for each vehicle. This chart will identify the proper deodorizing procedure, template and wiring diagram. Deodorizing the evaporator case can easily be done by removing the blower motor resistor and tape off opening. The nozzle can now be inserted through a pierced hole in the tape to deodorize the evaporator case. For some of the vehicles specified below, a drilling procedure is identified in the deodorizing instructions. This type of alternative procedure and others can be done by using the referenced templates in the chart. 4. Complete detailed installation instructions are supplied with the blower control package. Important: A. 1996 ONLY (Use blower resistor location for drilling procedure) B. 1994-1996 ONLY Refer to appropriate Service Manual for enabling afterblow feature through on-board diagnostics. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Customer Interest: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10405 For vehicles repaired under warranty, use as shown. Figure 1 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Customer Interest: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10406 Figure 2 Figure 3 Figure 4 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Customer Interest: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10407 Figure 5 Figure 6 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Customer Interest: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10408 Figure 7 Figure 8 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Customer Interest: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10409 Figure 9 Figure 10 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Customer Interest: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10410 Figure 11 Figure 12 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Customer Interest: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10411 Figure 13 Figure 14 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Customer Interest: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10412 Figure 15 Figure 16 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Customer Interest: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10413 Figure 17 Figure 18 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Customer Interest: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10414 Figure 19 Figure 20 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Customer Interest: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10415 Figure 21 Figure 22 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Customer Interest: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10416 Figure 23 Figure 24 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Customer Interest: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10417 Figure 25 Figure 26 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Customer Interest: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10418 Figure 27 Figure 28 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 99-01-39-004C > Jun > 09 > A/C - Musty Odors Emitted From (HVAC) System Evaporator Core: All Technical Service Bulletins A/C - Musty Odors Emitted From (HVAC) System TECHNICAL Bulletin No.: 99-01-39-004C Date: June 12, 2009 Subject: Air Conditioning Odor (Install Evaporator Core Dryer Kit and Apply Cooling Coil Coating) Models: 1993-2010 GM Passenger Cars and Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 All Equipped with Air Conditioning Supercede: This bulletin is being revised to add the 2009 and 2010 model years. Please discard Corporate Bulletin Number 99-01-39-004B (Section 01 - HVAC). Condition Some customers may comment about musty odors emitted from the Heating, Ventilation and Air Conditioning (HVAC) system at vehicle start-up in hot, humid conditions. Cause This condition may be caused by condensate build-up on the evaporator core, which does not evaporate by itself in high humidity conditions. The odor may be the result of microbial growth on the evaporator core. When the blower motor fan is turned on, the microbial growth may release an unpleasant musty odor into the passenger compartment. There are several other possible sources of a musty odor in a vehicle. A common source is a water leak into the interior of the vehicle or foreign material in the HVAC air distribution system. Follow the procedures in SI for identifying and correcting water leaks and air inlet inspection. The procedure contained in this bulletin is only applicable if the odor source has been determined to be microbial growth on the evaporator core inside the HVAC module. Correction Many vehicles currently incorporate an afterblow function within the HVAC control module software. The afterblow feature, when enabled, employs the HVAC blower fan to dry the evaporator after vehicle shut down and this function will inhibit microbial growth. Technicians are to confirm that the customer concern is evaporator core odor and that the vehicle has the imbedded afterblow feature, as defined in the SI document for that specific vehicle model, model year and specific HVAC option. Refer to SI for enabling the afterblow function. Vehicles being delivered in areas prone to high humidity conditions may benefit from having the afterblow enabled calibration installed prior to any customer comment. Important If the vehicle is not factory equipped with the imbedded afterblow enable feature, it may be added with the Electronic Evaporator Dryer Module Kit (P/N 12497910 or AC Delco 15-5876). Important When installing the Electronic Evaporator Dryer Module, you MUST use the included electrical splice connectors to ensure a proper splice. Complete detailed installation instructions and self testing procedures are supplied with the kit. If necessary, the Electronic Evaporator Dryer Module may be installed underhood if it is protected from extreme heat and water splash areas. To immediately remove the evaporator core odor on all suspect vehicles, it is necessary to eliminate the microbial growth and prevent its re-occurrence. To accomplish this, perform the following procedure: Vehicle and Applicator Tool Preparation 1. The evaporator core must be dry. This may be accomplished by disabling the compressor and running the blower fan on the recirc heat setting for an extended period of time. Note Compressor engagement will cause the evaporator core to remain wet and will prevent full adherence of the Coiling Coil Coating to the evaporator core surfaces. 2. Verify that the air conditioning drain hose is not clogged and place a drain pan beneath the vehicle. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 99-01-39-004C > Jun > 09 > A/C - Musty Odors Emitted From (HVAC) System > Page 10424 3. Place a protective cover over the carpet below the evaporator core. 4. Remove the cabin air filter, if equipped, and cover the opening prior to applying the Cooling Coil Coating, as the product may clog the filter. If the cabin air filter appears to have little or no remaining life, suggest a replacement to your customer. 5. If the HVAC module has a blower motor cooling tube, be careful NOT TO SPRAY THE COOLING COIL COATING INTO THE BLOWER MOTOR COOLING TUBE. 6. Attach the Flexible Applicator Pressure Spray Tool (J-43810-20A) to a compressed air line operating at 586 kPa (85 psi) to 793 kPa (115 psi). 7. Shake the bottle of Cooling Coil Coating well. Screw the bottle onto the cap on the applicator tool's pick-up tube. Note The pick-up tube is designed for 120 ml (4 oz) and 240 ml (8 oz) bottles and should coil slightly in the bottom of a 120 ml (4 oz) bottle. 8. Use one of the following three methods to apply the Cooling Coil Coating. Important If the Pressure Applicator Spray Tool (J-43810-20A) is not available, the Cooling Coil Coating is also available in an aerosol can (P/N 12377951 (in Canada, 10953503)). Application Through Blower Motor Control Module Opening - Remove the blower motor control module (blower motor resistor). Refer to the applicable procedure in SI. - Clean any debris or foreign material from inside the HVAC module and on the evaporator core surface. - Apply the Cooling Coil Coating directly to the evaporator core through the blower motor blower motor control module (blower motor resistor) opening. - Use the flexible wand to direct the Cooling Coil Coating over the entire evaporator core and surrounding gasket surfaces. - When the application is complete, install the blower motor blower motor control module (blower motor control module). Application Through Blower Motor Opening - Remove the blower motor. Refer to the applicable blower motor removal procedure in SI. - Clean any debris or foreign material from inside the HVAC module and on the evaporator core surface. - Apply the Cooling Coil Coating directly to the evaporator core through the blower motor opening. - Use the flexible wand to direct the Cooling Coil Coating over the entire evaporator core and surrounding gasket surfaces. - When the application is complete, install the blower motor. Application Through a Hole in the HVAC Module - If neither of the two previous application methods are available, it may be necessary to drill a hole in the HVAC module. - Locate an area of the HVAC module between the blower motor and the evaporator core. Drill a 10 mm (3/8 in) hole in the HVAC module. Use caution to keep the drill clear of the evaporator core and the blower motor fan. - With the air distribution vents closed and the blower motor fan speed on HIGH, insert the applicator tool into the hole and spray the Cooling Coil Coating into the airstream toward the evaporator core. - Use a GM approved RTV sealant to plug the hole in the HVAC module. 9. After the Cooling Coil Coating application is complete, start and run the vehicle for approximately 10 minutes, with the compressor disabled, HVAC mode set to Recirculate/Max, heat set to full warm, blower motor fan speed on high, and one window open approximately 12 mm (1/2 in). This cures the Cooling Coil Coating onto the evaporator core surface. 10. While the engine is running, rinse the applicator tool with warm water to prolong the life of the tool. Be sure to spray warm water through the nozzle to rinse out any residual Cooling Coil Coating still in the capillary pick up tube, otherwise it will dry and clog the applicator tool. Also remove the small green valve from the bottle cap and rinse it thoroughly while rolling it between two fingers and then reinstall it. If this valve is clogged , the Cooling Coil Coating will not flow through the applicator tool. 11. Shut off the engine and enable the compressor again. 12. Verify proper HVAC system operation. 13. Remove the protective cover from inside the vehicle. 14. Remove the drain pan from underneath the vehicle. 15. Reinstall the cabin air filter if necessary. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 99-01-39-004C > Jun > 09 > A/C - Musty Odors Emitted From (HVAC) System > Page 10425 Parts Information Important The Cooling Coil Coating listed below is the only GM approved product for use under warranty as an evaporator core disinfectant and for the long term control of evaporator core microbial growth. Warranty Information For vehicles repaired under warranty, use the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates Evaporator Core: All Technical Service Bulletins A/C - Odor at Start up in Humid Climates File In Section: 1 - HVAC Bulletin No.: 53-12-12A Date: December, 1996 Subject: Air Conditioning Odor at Start Up in Humid Climates (Disinfect Evaporator Core, Install Delayed Blower Control Package) Models: 1993-96 Passenger Cars (Except GEO) 1993-96 Light Duty Models (Except Tracker) This bulletin is being revised to update the wiring diagrams, add the Corvette (with RPO C60) and delete medium/heavy duty trucks. Please discard Corporate Bulletin Number 53-12-12 (Section 1 HVAC). Condition Some owners may comment on odors emitted from the air conditioning system, primarily at start up in hot, humid climates. Cause This odor may be the result of microbial growth on the evaporator core. When the blower motor fan is turned on, the microbial growth may release an unpleasant musty odor into the passenger compartment. Correction To remove odors of this type, it is necessary to eliminate the microbial growth and prevent its recurrence. To accomplish this, these two procedures must be completed. ^ Deodorize the evaporator core using Deodorizing Aerosol Kit, P/N 12377951 (AC Delco 15-102). ^ Install the new A/C Delayed Blower Control Package, P/N 12370470, (AC Delco 15-8632). The blower control package will enable the blower to run at high speed for five (5) minutes. It will do so approximately fifty (50) minutes after the ignition has been turned off if the compressor had been engaged for four (4) or more minutes prior to shutting off engine. By doing so, the evaporator case and core are dried out, reducing the chances of a recurring A/C odor. Procedure 1. Visually inspect the air conditioning evaporator drain hose for obstructions or working condition. 2. Apply deodorizing aerosol as described in the instructions supplied with the kit. Once the deodorizer has been applied, some of the mixture may overflow from the drain hose. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10430 3. The chart identifies specific instructions for each vehicle. This chart will identify the proper deodorizing procedure, template and wiring diagram. Deodorizing the evaporator case can easily be done by removing the blower motor resistor and tape off opening. The nozzle can now be inserted through a pierced hole in the tape to deodorize the evaporator case. For some of the vehicles specified below, a drilling procedure is identified in the deodorizing instructions. This type of alternative procedure and others can be done by using the referenced templates in the chart. 4. Complete detailed installation instructions are supplied with the blower control package. Important: A. 1996 ONLY (Use blower resistor location for drilling procedure) B. 1994-1996 ONLY Refer to appropriate Service Manual for enabling afterblow feature through on-board diagnostics. Parts Information Parts are currently available from GMSPO. Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10431 For vehicles repaired under warranty, use as shown. Figure 1 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10432 Figure 2 Figure 3 Figure 4 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10433 Figure 5 Figure 6 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10434 Figure 7 Figure 8 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10435 Figure 9 Figure 10 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10436 Figure 11 Figure 12 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10437 Figure 13 Figure 14 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10438 Figure 15 Figure 16 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10439 Figure 17 Figure 18 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10440 Figure 19 Figure 20 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10441 Figure 21 Figure 22 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10442 Figure 23 Figure 24 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10443 Figure 25 Figure 26 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 531212A > Dec > 96 > A/C - Odor at Start up in Humid Climates > Page 10444 Figure 27 Figure 28 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 661206 > Sep > 96 > A/C - Insufficient Cooling Diagnosis Table Updated Evaporator Core: All Technical Service Bulletins A/C - Insufficient Cooling Diagnosis Table Updated File In Section: 1 - HVAC Bulletin No.: 66-12-06 Date: September, 1996 SERVICE MANUAL UPDATE Subject: Section 1B - HVAC - Updated CCOT Insufficient Cooling Diagnosis Table Models: 1991-97 Chevrolet and GMC C/K Models This bulletin updates Section 1B "Heater, Ventilation, and Air Conditioning" of the 1991-97 C/K Truck Service Manuals. The current Service Manual air conditioning diagnostic information tables have been updated to better address the possibility of a missing or damaged orifice tube in the air conditioning system. The revised chart "A" will send the technician to both charts "D" and "E" in the event that the evaporator inlet and outlet pipes are the same temperature while the air conditioning system is in operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Evaporator Core: > 661206 > Sep > 96 > A/C - Insufficient Cooling Diagnosis Table Updated > Page 10449 Bulletin No.: 66-12-06 The included revised chart "A" should be used in place of the chart "A" in the 1991-97 Service Manuals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Other Service Bulletins for Evaporator Core: > 661206 > Sep > 96 > A/C - Insufficient Cooling Diagnosis Table Updated Evaporator Core: All Technical Service Bulletins A/C - Insufficient Cooling Diagnosis Table Updated File In Section: 1 - HVAC Bulletin No.: 66-12-06 Date: September, 1996 SERVICE MANUAL UPDATE Subject: Section 1B - HVAC - Updated CCOT Insufficient Cooling Diagnosis Table Models: 1991-97 Chevrolet and GMC C/K Models This bulletin updates Section 1B "Heater, Ventilation, and Air Conditioning" of the 1991-97 C/K Truck Service Manuals. The current Service Manual air conditioning diagnostic information tables have been updated to better address the possibility of a missing or damaged orifice tube in the air conditioning system. The revised chart "A" will send the technician to both charts "D" and "E" in the event that the evaporator inlet and outlet pipes are the same temperature while the air conditioning system is in operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > All Other Service Bulletins for Evaporator Core: > 661206 > Sep > 96 > A/C - Insufficient Cooling Diagnosis Table Updated > Page 10455 Bulletin No.: 66-12-06 The included revised chart "A" should be used in place of the chart "A" in the 1991-97 Service Manuals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Technical Service Bulletins > Page 10456 Evaporator Core: Testing and Inspection One of the most difficult leaks to find is in the evaporator core. To leak test the core: 1. Turn the blower fan on "HIGH" for 15 or more seconds then turn it off. 2. Wait 10 minutes. 3. Remove the blower motor resistor. 4. Insert the leak detector probe as close to the evaporator as possible. If the detector goes to a solid alarm, a leak has been found. 5. If possible, visually inspect the core face with a flashlight for evidence of refrigerant oil. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Service and Repair > Primary A/C System Evaporator Core: Service and Repair Primary A/C System Evaporator/ Heater Core Case Remove or Disconnect 1. Negative battery cable. 2. Engine coolant. 3. Recover refrigerant. 4. Instrument panel. 5. Electrical connectors, as necessary. 6. Center floor air distribution duct. 7. ECM and mounting tray. 8. Hinge pillar trim panels. 9. Blower motor cover. 10. Blower motor (60). 11. Steering column. 12. Tilt back instrument panel assembly. 13. Coolant recovery reservoir. 14. Heater hoses. 15. Evaporator tube. 16. Accumulator. 17. Screws (52 and 64). 18. Nut (50). 19. Screw (56). 20. Module assembly (57). - May be necessary to have an assistant when removing module assembly. 21. Evaporator case bottom cover plate (63). - Remove the seven screws that hold the cover plate to the module assembly. 22. Heater core and seal from module assembly. 23. Evaporator case cover (61). - Remove the four screws that hold the case cover to the module assembly. 24. Evaporator core. Install or Connect 1. Evaporator core. Refer to Specifications / Capacities / Refrigerant Oil Distribution. 2. Evaporator case cover (61). - Install the four screws that hold the case cover to the module assembly. 3. Heater core and seal into module assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Service and Repair > Primary A/C System > Page 10459 4. Evaporator case bottom cover plate (63). - Install the seven screws that hold the cover plate to the module assembly. 5. Module assembly (57). - May be necessary to have an assistant when installing module assembly. 6. Screw (56). 7. Nut (50). 8. Screws (52 and 64). Tighten ^ Screw (56) to 11 Nm (97 lb in). ^ Nut (50) to 2.8 Nm (25 lb in). ^ Screws (52 and 64) to 1.9 Nm (17 lb in). 9. Accumulator. 10. Evaporator tube. 11. Heater hoses. 12. Coolant recovery reservoir. 13. Instrument panel. 14. Steering column. 15. Blower motor (60). 16. Blower motor cover. 17. Hinge pillar trim panels. 18. ECM and mounting tray. 19. Center floor air distribution duct. 20. Electrical connectors, as necessary. 21. Engine coolant. 22. Negative battery cable. 23. Charge system. 24. Check system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Service and Repair > Primary A/C System > Page 10460 Evaporator Core: Service and Repair Auxiliary A/C System Some Figure 46 - Auxiliary Heater And A/C Module Removing Case Clip Remove or Disconnect 1. Negative battery cable. 2. Recover refrigerant. 3. Rear quarter interior trim, as necessary. 4. Right rear quarter trim panel. 5. Right rear wheelhouse (Suburban). 6. Rear heater hoses from auxiliary heater core, if equipped (Suburban only). 7. Auxiliary refrigerant hoses from auxiliary evaporator. 8. Electrical connectors, as necessary. 9. Heater/evaporator case cover. For Suburban models, proceed as follows: A. Remove case clips (Figure 48). B. Remove eleven case screws. C. Separate case halves. - For Four Door Utility models, proceed as follows: A. Remove screws securing case to rear quarter sheet metal. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Service and Repair > Primary A/C System > Page 10461 B. Remove blower housing from rear of case. C. Remove 10 case clips. D. Separate case halves. 10. Pipe insulator. 11. Evaporator core. Install or Connect 1. Evaporator core. 2. Pipe insulator. 3. Heater/evaporator case cover screws or clips as equipped. - Blower housing to case on Four Door Utility models - Blower motor to case on Suburban models 4. Auxiliary case to the vehicle. 5. Auxiliary refrigerant hoses to auxiliary evaporator. 6. Rear heater hoses to auxiliary heater core, if equipped. 7. Electrical connectors, as necessary. 8. Right rear wheelhouse (Suburban only). 9. Right rear quarter trim panel. 10. Rear quarter interior trim, as necessary. 11. Negative battery cable. 12. Charge system. 13. Check system for leaks. 4 Door Utility Figure 47 - Auxiliary A/C Module Remove or Disconnect 1. Negative battery cable. 2. Recover refrigerant. 3. Rear quarter interior trim, as necessary. 4. Right rear quarter trim panel. 5. Right rear wheelhouse (Suburban only). 6. Rear heater hoses from auxiliary heater core, if equipped (Suburban only). 7. Auxiliary refrigerant hoses from auxiliary evaporator. 8. Electrical connectors, as necessary. 9. Heater/evaporator case cover. For Suburban models, proceed as follows: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Service and Repair > Primary A/C System > Page 10462 A. Remove case clips (Figure 48). B. Remove eleven case screws. C. Separate case halves. - For Four Door Utility models, proceed as follows: A. Remove screws securing case to rear quarter sheet metal. B. Remove blower housing from rear of case. C. Remove 10 case clips. D. Separate case halves. 10. Pipe insulator. 11. Evaporator core. Install or Connect 1. Evaporator core. 2. Pipe insulator. 3. Heater/evaporator case cover screws or clips as equipped. - Blower housing to case on Four Door Utility models - Blower motor to case on Suburban models 4. Auxiliary case to the vehicle. 5. Auxiliary refrigerant hoses to auxiliary evaporator. 6. Rear heater hoses to auxiliary heater core, if equipped. 7. Electrical connectors, as necessary. 8. Right rear wheelhouse (Suburban only). 9. Right rear quarter trim panel. 10. Rear quarter interior trim, as necessary. 11. Negative battery cable. 12. Charge system. 13. Check system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Evaporator Core > Component Information > Service and Repair > Primary A/C System > Page 10463 Evaporator Core: Service and Repair Rear Air Conditioning Remove or Disconnect 1. Negative battery cable. 2. Recover refrigerant. 3. Rear quarter interior trim. 4. Right rear quarter trim. 5. Auxiliary refrigerant hoses from auxiliary evaporator. 6. Electrical connectors, as necessary. 7. Auxiliary case cover. a. Remove screws securing case to rear quarter sheet metal. b. Remove blower housing from rear of case. c. Remove 10 case clips. d. Separate case halves. 8. Pipe insulator. 9. Evaporator core. Install or Connect 1. Evaporator core. 2. Pipe insulator. 3. Auxiliary case cover screws or clips as equipped. 4. Auxiliary case to the vehicle. 5. Auxiliary refrigerant hoses to auxiliary evaporator. 6. Electrical connectors as necessary. 7. Right rear quarter trim panel. 8. Rear quarter interior trim, as necessary. 9. Negative battery cable. 10. Charge A/C system. 11. Check system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Expansion Block/Orifice Tube > Component Information > Technical Service Bulletins > A/C - Insufficient Cooling Diagnosis Table Updated Expansion Block/Orifice Tube: Technical Service Bulletins A/C - Insufficient Cooling Diagnosis Table Updated File In Section: 1 - HVAC Bulletin No.: 66-12-06 Date: September, 1996 SERVICE MANUAL UPDATE Subject: Section 1B - HVAC - Updated CCOT Insufficient Cooling Diagnosis Table Models: 1991-97 Chevrolet and GMC C/K Models This bulletin updates Section 1B "Heater, Ventilation, and Air Conditioning" of the 1991-97 C/K Truck Service Manuals. The current Service Manual air conditioning diagnostic information tables have been updated to better address the possibility of a missing or damaged orifice tube in the air conditioning system. The revised chart "A" will send the technician to both charts "D" and "E" in the event that the evaporator inlet and outlet pipes are the same temperature while the air conditioning system is in operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Expansion Block/Orifice Tube > Component Information > Technical Service Bulletins > A/C - Insufficient Cooling Diagnosis Table Updated > Page 10468 Bulletin No.: 66-12-06 The included revised chart "A" should be used in place of the chart "A" in the 1991-97 Service Manuals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Expansion Block/Orifice Tube > Component Information > Locations > For Front Unit Expansion Block/Orifice Tube: Locations For Front Unit With Front A/C Only Evaporator Tube The Expansion Tube is located in the condenser outlet pipe (high side line) at the liquid line connection. With Front and Rear This image is updated by TSB 661205 dated August 1996. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Expansion Block/Orifice Tube > Component Information > Locations > For Front Unit > Page 10471 The expansion tube is located in a Y-shaped junction block in the tube between the condenser and the front evaporator. The junction block is located near the right side of the radiator support. The expansion tube is located between the junction block and the front evaporator. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Expansion Block/Orifice Tube > Component Information > Locations > For Front Unit > Page 10472 Expansion Block/Orifice Tube: Locations For Rear Unit Rear Heater Auxiliary A/C Module Rear units use an Expansion Valve. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Expansion Block/Orifice Tube > Component Information > Locations > Page 10473 Expansion Block/Orifice Tube: Description and Operation OPERATION The orifice tube provides a restriction to the high-pressure liquid refrigerant in the liquid line, metering the flow of refrigerant to the evaporator as a low-pressure liquid. The expansion tube and orifice are protected from contamination by filter screens on both inlet and outlet sides. The tube is serviced only as a replacement assembly. When the engine is turned "OFF" with the air conditioning operating, the refrigerant in the system will flow from the high-pressure side of the expansion tube (orifice) to the low-pressure side until the pressure is equalized. This may be detected as a faint sound of liquid flowing (hissing) for 30 to 60 seconds and is a normal condition. When system diagnostics indicate a restricted expansion tube, it may not be necessary to replace it. Metal chips, flakes, or slivers found on the screen may be removed with compressed air. The expansion tube may be reused if: ^ The plastic frame is not broken. ^ The expansion tube is not damaged or plugged. ^ The screen material is not torn. ^ The screen is not plugged with fine gritty material. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Expansion Block/Orifice Tube > Component Information > Locations > Page 10474 Expansion Block/Orifice Tube: Service and Repair Evaporator Tube Tool Required: J 26549-E Orifice Tube Remover and Installer or Equivalent Remove or Disconnect 1. Recover refrigerant. 2. Grille. 3. Evaporator tube from condenser. 4. O-ring seal. - Cap or plug the open line. 5. Expansion (orifice) tube from the condenser outlet pipe, using J 26549-E or equivalent. - In the event that difficulty is encountered during the removal of a restricted or plugged expansion (orifice) tube, the following procedure is recommended: A Remove as much of any impacted residue as possible. B. Carefully apply heat with heat gun (hair drier, epoxy drier or equivalent) approximately 7 mm (1/4 inch) from dimples on inlet pipe. Do not overheat pipe. C. While applying heat, use expansion tube removal tools J 26549-E or equivalent to grip the expansion (orifice) tube. Use a turning motion along with a push-pull motion to loosen the impacted expansion (orifice) tube and remove it. Install or Connect 1. Expansion tube into condenser outlet pipe, using J 26549-E or equivalent. 2. New O-ring seal. A. Coat O-ring seal with 525 viscosity refrigerant oil. B. Insert the short screen end of the new orifice into the evaporator tube. 3. Evaporator tube to condenser. 4. Grille. 5. Charge system. 6. Check system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Expansion Valve > Component Information > Locations Rear Heater Auxiliary A/C Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Expansion Valve > Component Information > Locations > Page 10478 Expansion Valve: Description and Operation PURPOSE The rear air conditioning system uses a Thermo Expansion Valve (TXV). The valve consists of the capillary tube, body, actuating pins, seat and orifice. At the high pressure liquid inlet, a fine mesh screen prevents dirt, fillings or other foreign material from entering the valve orifice. OPERATION When the valve is connected in the system, high pressure liquid refrigerant enters the valve through the screen from the condenser and passes on to the seat and orifice where it changes into a low pressure liquid. The low pressure liquid leaves the valve and flows into the evaporator core where it absorbs heat from the evaporator core and changes to a low pressure vapor and leaves the evaporator core. The capillary tube is clamped to the low pressure vapor line just below the outlet of the evaporator. The capillary tube is held in contact with the rear evaporator outlet tube by a metal clip placed near the end of the tube. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Expansion Valve > Component Information > Service and Repair > Note on Expansion Valve Expansion Valve: Service and Repair Note on Expansion Valve Note: Only suburbans with rear air conditioning are equipped with an expansion valve. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Heater Control Valve > Component Information > Locations Heater Control Valve: Locations Engine Compartment, RH rear side of Inner Fender Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Heater Control Valve > Component Information > Locations > Page 10484 Heater Control Valve: Service and Repair Heater Water Valve Remove or Disconnect 1. Engine coolant. 2. Hose clamps at heater water valve. - Loosen the clamps enough to slide the clamps away from the fittings on the valve. 3. Hoses from valve. 4. Vacuum line from valve. 5. Valve. Install or Connect 1. Vacuum line to valve. 2. Hoses to valve. 3. Clamps to hoses. - Slide clamps to previous location beyond retaining bead on water valve fitting. 4. Engine coolant. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Heater Core > Component Information > Technical Service Bulletins > Cooling System, A/C - Aluminum Heater Cores/Radiators Heater Core: Technical Service Bulletins Cooling System, A/C - Aluminum Heater Cores/Radiators INFORMATION Bulletin No.: 05-06-02-001A Date: July 16, 2008 Subject: Information On Aluminum Heater Core and/or Radiator Replacement Models: 2005 and Prior GM Passenger Cars and Light Duty Trucks (including Saturn) 2003-2005 HUMMER H2 Supercede: This bulletin is being revised to update the Warranty Information. Please discard Corporate Bulletin Number 05-06-02-001 (Section 06 - Engine/Propulsion System). Important: 2004-05 Chevrolet Aveo (Pontiac Wave, Canada Only) does not use DEX-COOL(R). Refer to the flushing procedure explained later in this bulletin. The following information should be utilized when servicing aluminum heater core and/or radiators on repeat visits. A replacement may be necessary because erosion, corrosion, or insufficient inhibitor levels may cause damage to the heater core, radiator or water pump. A coolant check should be performed whenever a heater core, radiator, or water pump is replaced. The following procedures/ inspections should be done to verify proper coolant effectiveness. Caution: To avoid being burned, do not remove the radiator cap or surge tank cap while the engine is hot. The cooling system will release scalding fluid and steam under pressure if the radiator cap or surge tank cap is removed while the engine and radiator are still hot. Important: If the vehicle's coolant is low, drained out, or the customer has repeatedly added coolant or water to the system, then the system should be completely flushed using the procedure explained later in this bulletin. Technician Diagnosis ^ Verify coolant concentration. A 50% coolant/water solution ensures proper freeze and corrosion protection. Inhibitor levels cannot be easily measured in the field, but can be indirectly done by the measurement of coolant concentration. This must be done by using a Refractometer J 23688 (Fahrenheit scale) or J 26568 (centigrade scale), or equivalent, coolant tester. The Refractometer uses a minimal amount of coolant that can be taken from the coolant recovery reservoir, radiator or the engine block. Inexpensive gravity float testers (floating balls) will not completely analyze the coolant concentration fully and should not be used. The concentration levels should be between 50% and 65% coolant concentrate. This mixture will have a freeze point protection of -34 degrees Fahrenheit (-37 degrees Celsius). If the concentration is below 50%, the cooling system must be flushed. ^ Inspect the coolant flow restrictor if the vehicle is equipped with one. Refer to Service Information (SI) and/or the appropriate Service Manual for component location and condition for operation. ^ Verify that no electrolysis is present in the cooling system. This electrolysis test can be performed before or after the system has been repaired. Use a digital voltmeter set to 12 volts. Attach one test lead to the negative battery post and insert the other test lead into the radiator coolant, making sure the lead does not touch the filler neck or core. Any voltage reading over 0.3 volts indicates that stray current is finding its way into the coolant. Electrolysis is often an intermittent condition that occurs when a device or accessory that is mounted to the radiator is energized. This type of current could be caused from a poorly grounded cooling fan or some other accessory and can be verified by watching the volt meter and turning on and off various accessories or engage the starter motor. Before using one of the following flush procedures, the coolant recovery reservoir must be removed, drained, cleaned and reinstalled before refilling the system. Notice: ^ Using coolant other than DEX‐COOL(R) may cause premature engine, heater core or radiator corrosion. In addition, the engine coolant may require changing sooner, at 30,000 miles (50,000 km) or 24 months, whichever occurs first. Any repairs would not be covered by your warranty. Always use DEX‐COOL(R) (silicate free) coolant in your vehicle. ^ If you use an improper coolant mixture, your engine could overheat and be badly damaged. The repair cost would not be covered by your warranty. Too much water in the mixture can freeze and crack the engine, radiator, heater core and other parts. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Heater Core > Component Information > Technical Service Bulletins > Cooling System, A/C - Aluminum Heater Cores/Radiators > Page 10489 Flushing Procedures using DEX-COOL(R) Important: The following procedure recommends refilling the system with DEX-COOL(R), P/N 12346290 (in Canada, use P/N 10953464), GM specification 6277M. This coolant is orange in color and has a service interval of 5 years or 240,000 km (150,000 mi). However, when used on vehicles built prior to the introduction of DEX-COOL(R), maintenance intervals will remain the same as specified in the Owner's Manual. ^ If available, use the approved cooling system flush and fill machine (available through the GM Dealer Equipment Program) following the manufacturer's operating instructions. ^ If approved cooling system flush and fill machine is not available, drain the coolant and dispose of properly following the draining procedures in the appropriate Service Manual. Refill the system using clear, drinkable water and run the vehicle until the thermostat opens. Repeat and run the vehicle three (3) times to totally remove the old coolant or until the drained coolant is almost clear. Once the system is completely flushed, refill the cooling system to a 50%-60% concentration with DEX‐COOL(R), P/N 12346290 (in Canada, use P/N 10953464), GM specification 6277M, following the refill procedures in the appropriate Service Manual. If a Service Manual is not available, fill half the capacity of the system with 100% DEX-COOL(R), P/N 12346290 (in Canada, use P/N 10953464), GM specification 6277M. Then slowly add clear, drinkable water (preferably distilled) to the system until the level of the coolant mixture has reached the base of the radiator neck. Wait two (2) minutes and reverify the coolant level. If necessary, add clean water to restore the coolant to the appropriate level. Once the system is refilled, reverify the coolant concentration using a Refractometer J 23688 (Fahrenheit scale) or J 26568 (centigrade scale) coolant tester, or equivalent. The concentration levels should be between 50% and 65%. Flushing Procedures using Conventional Silicated (Green Colored) Coolant Important: 2004-2005 Chevrolet Aveo (Pontiac Wave, Canada Only) does not use DEX‐COOL(R). The Aveo and Wave are filled with conventional, silicated engine coolant that is blue in color. Silicated coolants are typically green in color and are required to be drained, flushed and refilled every 30,000 miles (48,000 km). The Aveo and Wave are to be serviced with conventional, silicated coolant. Use P/N 12378560 (1 gal) (in Canada, use P/N 88862159 (1 L). Refer to the Owner's Manual or Service Information (SI) for further information on OEM coolant. Important: Do not mix the OEM orange colored DEX-COOL(R) coolant with green colored coolant when adding coolant to the system or when servicing the vehicle's cooling system. Mixing the orange and green colored coolants will produce a brown coolant which may be a customer dissatisfier and will not extend the service interval to that of DEX-COOL(R). Conventional silicated coolants offered by GM Service and Parts Operations are green in color. ^ If available, use the approved cooling system flush and fill machine (available through the GM Dealer Equipment Program) following the manufacturer's operating instructions. ^ If approved cooling systems flush and fill machine is not available, drain coolant and dispose of properly following the draining procedures in appropriate Service Manual. Refill the system using clear, drinkable water and run vehicle until thermostat opens. Repeat and run vehicle three (3) times to totally remove old coolant or until drained coolant is almost clear. Once the system is completely flushed, refill the cooling system to a 50%-60% concentration with a good quality ethylene glycol base engine coolant, P/N 12378560, 1 gal (in Canada, use P/N 88862159 1 L), conforming to GM specification 1825M, or recycled coolant conforming to GM specification 1825M, following the refill procedures in the appropriate Service Manual. If a Service Manual is not available, fill half the capacity of the system with 100% good quality ethylene glycol base (green colored) engine coolant, P/N 12378560 1 gal., (in Canada, use P/N 88862159 1 L) conforming to GM specification 1825M. Then slowly add clear, drinkable water (preferably distilled) to system until the level of the coolant mixture has reached the base of the radiator neck. Wait two (2) minutes and recheck coolant level. If necessary, add clean water to restore coolant to the appropriate level. Once the system is refilled, recheck the coolant concentration using a Refractometer J 23688 (Fahrenheit scale) or J 26568 (centigrade scale) coolant tester, or equivalent. Concentration levels should be between 50% and 65%. Parts Information Warranty Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Heater Core > Component Information > Technical Service Bulletins > Cooling System, A/C - Aluminum Heater Cores/Radiators > Page 10490 For vehicles repaired under warranty, use the table. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Heater Core > Component Information > Technical Service Bulletins > Page 10491 Heater Core: Description and Operation PURPOSE In any air conditioning mode, the heater core heats the cool, dehumidified air to achieve the desired temperature. The position of the control assembly temperature rotary knob determines how much heat is added to the incoming air. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Heater Core > Component Information > Service and Repair > With Air Conditioning Heater Core: Service and Repair With Air Conditioning HEATER CORE Remove or Disconnect 1. Engine coolant. 2. Instrument panel storage compartment. 3. Electrical connectors, as necessary. 4. Center floor air distribution duct. 5. Hinge pillar trim panels. 6. Blower motor cover. 7. Blower motor. 8. Steering column. 9. Roll instrument panel back. 10. Coolant recovery reservoir. 11. Heater hoses. 12. Screw on interior side of cowl, near the evaporator pipe (if equipped) while holding heater case to the cowl. 13. Four screws on the engine side of the cowl holding the heater case to the cowl. 14. Two nuts on the engine side of the cowl holding the heater case to the cowl. 15. Heater case. - It may be necessary to have an assistant when removing heater case. 16. Heater cover. - Remove seven screws that hold cover to the heater case. 17. Heater core from retainer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Heater Core > Component Information > Service and Repair > With Air Conditioning > Page 10494 Install or Connect 1. Heater core into retainer. - Install seven screws that hold heater cover to heater case. 2. Heater cover. - Make sure heater cover is properly sealed. 3. Heater case. - May be necessary to have an assistant when installing heater case. 4. Nuts. 5. Screws. Tighten - Screws on engine side of the cowl to 1.9 Nm (17 lb in). - uts to 2.8 Nm (25 lb in). - Screw on interior side of the cowl to 11 Nm (97 lb in). 6. Heater hoses. 7. Coolant recovery reservoir. 8. Roll instrument panel forward. 9. Steering column. 10. Blower motor. 11. Blower motor cover. 12. Hinge pillar trim panels. 13. Center floor air distribution duct. 14. Electrical connectors, as necessary. 15. Instrument panel storage compartment. 16. Engine coolant. - Check the system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Heater Core > Component Information > Service and Repair > With Air Conditioning > Page 10495 Heater Core: Service and Repair Without Air Conditioning HEATER CORE Remove or Disconnect 1. Engine coolant. 2. Instrument panel storage compartment. 3. Electrical connectors, as necessary. 4. Center floor air distribution duct. 5. Hinge pillar trim panels. 6. Blower motor cover. 7. Blower motor. 8. Steering column. 9. Roll instrument panel back. 10. Coolant recovery reservoir. 11. Heater hoses. 12. Screw on interior side of cowl, near the evaporator pipe (if equipped) while holding heater case to the cowl. 13. Four screws on the engine side of the cowl holding the heater case to the cowl. 14. Two nuts on the engine side of the cowl holding the heater case to the cowl. 15. Heater case. - It may be necessary to have an assistant when removing heater case. 16. Heater cover. - Remove seven screws that hold cover to the heater case. 17. Heater core from retainer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Heater Core > Component Information > Service and Repair > With Air Conditioning > Page 10496 Install or Connect 1. Heater core into retainer. - Install seven screws that hold heater cover to heater case. 2. Heater cover. - Make sure heater cover is properly sealed. 3. Heater case. - May be necessary to have an assistant when installing heater case. 4. Nuts. 5. Screws. Tighten Screws on engine side of the cowl to 1.9 Nm (17 lb in). - Nuts to 2.8 Nm (25 lb in). - Screw on interior side of the cowl to 11 Nm (97 lb in). 6. Heater hoses. 7. Coolant recovery reservoir. 8. Roll instrument panel forward. 9. Steering column. 10. Blower motor. 11. Blower motor cover. 12. Hinge pillar trim panels. 13. Center floor air distribution duct. 14. Electrical connectors, as necessary. 15. Instrument panel storage compartment. 16. Engine coolant. - Check the system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Heater Hose > Component Information > Service and Repair > Heater Inlet Hose Heater Hose: Service and Repair Heater Inlet Hose Heater Hose Routing Quick Connect Heater Inlet Connector Tool Required: J 38723 Heater Line Quick Connect Separator Remove or Disconnect 1. Engine coolant. 2. Inlet hose from generator bracket. 3. Inlet hose at fender clip. 4. Inlet hose clamp at heater core. water shut off valve or tee fining. - Loosen the clamp enough to slide the clamp away from the fining on the inlet hose. 5. Inlet hose from heater core. 6. Push inlet hose into connector and insert J 38723 or equivalent into connector to release locking tabs. 7. Pull retainer and hose from heater inlet connector. Inspect - O-ring sealing surface on hose/pipe. Adjust - If replacing heater inlet connector, remove retainer from hose and discard, as new connector is equipped with retainer. - If replacing hose, remove retainer from hose and reinsert in connector. - If reusing hose and connector, retainer can remain in place on hose. Install or Connect 1. Push hose into connector until retainer tabs lock. - Pull back on hose to check for proper engagement. 2. Inlet hose to heater core, water shut off valve or tee fitting. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Heater Hose > Component Information > Service and Repair > Heater Inlet Hose > Page 10501 3. Inlet hose clamp. 4. Inlet hose mounting screw. Tighten Screw to 30 Nm (22 lb ft). 5. Inlet hose to fender clip. 6. Engine coolant. - Check the system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Heater Hose > Component Information > Service and Repair > Heater Inlet Hose > Page 10502 Heater Hose: Service and Repair Heater Outlet Hose Heater Hose Routing Quick Connect Heater Inlet Connector Remove or Disconnect 1. Engine coolant. 2. Outlet hose from fender clip. 3. Outlet hose clamp from heater core, water shut off valve or tee fitting. 4. Outlet hose from heater core. 5. Outlet hose mounting screw. 6. Outlet hose from generator bracket. 7. Outlet hose clamp from water pump. 8. Outlet hose from water pump. Install or Connect 1. Outlet hose to water pump. 2. Outlet hose clamp to water pump. 3. Outlet hose to generator bracket. 4. Generator bracket mounting screw. Tighten screw to 30 Nm (22 lb ft). 5. Outlet hose to heater core. 6. Outlet hose clamp to heater core. 7. Outlet hose to fender clip. 8. Engine coolant. - Check the system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > High Pressure Safety Valve HVAC > Component Information > Specifications High Pressure Safety Valve HVAC: Specifications Pressure Relief Valve .......................................................................................................................... .................................................... 9.0 N.m (6.1 lb. ft.) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > High Pressure Safety Valve HVAC > Component Information > Specifications > Page 10506 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > High Pressure Safety Valve HVAC > Component Information > Specifications > Page 10507 High Pressure Safety Valve HVAC: Description and Operation PURPOSE The compressor is equipped with a pressure relief valve as a safety factor. Under certain conditions, the refrigerant on the discharge side may exceed the designed operating pressure. Exceeding this pressure limit may cause refrigerant loss out of the pressure relief valve. To prevent refrigerant loss or compressor damage, the high pressure cutoff switch opens automatically at approximately 3036 kPa (440 psi). When the switch opens, current to the compressor clutch is interrupted. Any condition that causes the switch to open will keep the compressor from operating. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > High Pressure Safety Valve HVAC > Component Information > Specifications > Page 10508 High Pressure Safety Valve HVAC: Service and Repair Compressor - Rear Head Remove or Disconnect 1. Recover the refrigerant using J 39500-GM. 2. Remove old pressure relief valve. Install or Connect 1. Clean valve seat area on rear bead. 2. Lubricate O-ring of new pressure relief valve and O-ring assembly with new 525 viscosity refrigerant oil. Install new valve and torque in place, 9.0 N.m (6.1 lbs. ft.) 3. Evacuate and recharge the system. 4. Leak test system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Hose/Line HVAC > Component Information > Service Precautions Hose/Line HVAC: Service Precautions Proper O-Ring Installation Improper O-Ring Installation IMPORTANT - Before opening the refrigeration system to the atmosphere, make sure the work area is well ventilated. Welding or steam-cleaning operations should not be done on or near refrigeration system lines or other air conditioning parts on the vehicle. - All metal tubing lines should be free of dents or kinks to prevent loss of system capacity due to line restriction. - The flexible hose lines should never be bent to a radius of less than four times the diameter of the hose. - The flexible hose lines should never be allowed to come within a distance of 6.5 mm (2.5 inches) of the exhaust manifold. - Flexible hose lines should be inspected regularly for leaks or brittleness and replaced with new lines if deterioration or leaking is found. - When disconnecting any fitting in the refrigerant system, the system must be discharged of all Refrigerant-134a. However, proceed very cautiously, regardless of the gage readings. Open very slowly, keeping your face and hands away so that no injury can occur, If pressure is noticed when a fitting is loosened, allow it to bleed off very slowly. NOTICE: Alcohol should never be used In the refrigeration system In an attempt to remove moisture. Damage to system components could occur. - If any refrigerant line is opened to the atmosphere, it should be immediately capped to prevent the entrance of moisture and dirt. These contaminants can cause internal compressor wear or plugged lines in the condenser and evaporator core and expansion (orifice) tubes or compressor inlet screens. - Remove sealing caps from subassemblies just before making connections for final assembly. Use a small amount of clean 525 viscosity refrigerant oil on all tube and hose joints. Use new O-ring seals dipped in 525 viscosity refrigerant oil when assembling joints. The oil will aid in assembly and help to provide a leakproof joint. O-ring seals and seats must be in perfect condition because a burr or a piece of dirt can cause a refrigerant Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Hose/Line HVAC > Component Information > Service Precautions > Page 10512 leak. - It is important to use the proper wrenches when making connections on O-ring seal fittings. The use of improper wrenches may damage the connection. The opposing fitting should always be backed up with a wrench to prevent distortion of connecting lines or components. When connecting the flexible hose connections, it is important that the swaged fitting and the flare nut, as well as the coupling to which it is attached, be held at the same time using three different wrenches to prevent turning the fitting and damaging the seat. - Tighten tubing connections to the specified torque. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Hose/Line HVAC > Component Information > Service and Repair > Main Unit Hose/Line HVAC: Service and Repair Main Unit Evaporator Tube Remove or Disconnect 1. Negative battery cable. 2. Recover refrigerant. 3. Auxiliary heater pipe, if equipped. 4. Coolant recovery reservoir. 5. Evaporator tube from evaporator. 6. O-ring seal. 7. Evaporator tube from condenser. 8. O-ring seal. Install or Connect 1. Evaporator tube into clip. 2. New O-ring seal. - Coat O-ring seal with 525 viscosity refrigerant oil. 3. Evaporator tube to condenser. Tighten Evaporator tube to 24 Nm (18 lb ft). 4. New O-ring seal. - Coat O-ring seal with 525 viscosity refrigerant oil. 5. Evaporator tube to evaporator. Tighten Evaporator tube to 24 Nm (18 lb ft). 6. Coolant recovery reservoir. 7. Auxiliary heater pipe, if equipped. 8. Negative battery cable. 9. Charge system. - Check system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Hose/Line HVAC > Component Information > Service and Repair > Main Unit > Page 10515 Hose/Line HVAC: Service and Repair Auxiliary Unit Auxiliary Evaporator Tube Location Remove or Disconnect 1. Discharge and recover refrigerant from the system. 2. Evaporator tube from evaporator. 3. O-ring seal. 4. Evaporator tube from condenser. 5. O-ring seal. 6. Evaporator tube from auxiliary evaporator hose. 7. O-ring seal. 8. Evaporator tube. Install or Connect 1. Evaporator tube. 2. New O-ring seal. - Coat O-ring seal with 525 viscosity refrigerant oil. 3. Evaporator tube to auxiliary evaporator hose. Tighten evaporator tube to 24 Nm (18 lbs. ft.). 4. New O-ring seal. - Coat O-ring seal with 525 viscosity refrigerant oil. 5. Evaporator tube to condenser. Tighten evaporator tube to 24 Nm (18 lbs. ft.). 6. New O-ring seal. - Coat O-ring seal with 525 viscosity refrigerant oil. 7. Evaporator tube to evaporator. Tighten evaporator tube to 24 Nm (18 lbs. ft.). 8. Refrigerant to the system. - Check the system for leaks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Refrigerant > Component Information > Technical Service Bulletins > A/C - Refrigerant Recovery/Recycling/Equipment Refrigerant: Technical Service Bulletins A/C - Refrigerant Recovery/Recycling/Equipment Bulletin No.: 08-01-38-001 Date: January 25, 2008 INFORMATION Subject: Information On New GE-48800 CoolTech Refrigerant Recovery/Recharge Equipment Models: 2008 and Prior GM Passenger Cars and Light Duty Trucks (Including Saturn) 2008 and Prior HUMMER H2, H3 2005-2008 Saab 9-7X Attention: This bulletin is being issued to announce the release of GM approved Air Conditioning (A/C) Refrigerant Recovery and Recharging Equipment that meets the new Society of Automotive Engineers (SAE) J2788 Refrigerant Recovery Standards. The ACR2000 (J-43600) cannot be manufactured in its current state after December 2007 and will be superseded by GE-48800. The new J2788 standard does not require that GM Dealers replace their ACR2000 units. ACR2000's currently in use are very capable of servicing today's refrigerant systems when used correctly and can continue to be used. Details regarding the new SAE J2788 standard are outlined in GM Bulletin 07-01-38-004. Effective February 1 2008, new A/C Refrigerant Recovery/Recharging equipment (P/N GE-48800) will be released as a required replacement for the previously essential ACR2000 (J-43600). This equipment is SAE J2788 compliant and meets GM requirements for A/C Refrigerant System Repairs on all General Motors vehicles, including Hybrid systems with Polyolester (POE) refrigerant oil. This equipment will not be shipped as an essential tool to GM Dealerships. In addition, this equipment is Hybrid compliant and designed to prevent oil cross contamination when servicing Hybrid vehicles with Electric A/C Compressors that use POE refrigerant oil. The ACR2000 (J-43600) will need to be retrofitted with a J-43600-50 (Hose - ACR2000 Oil Flush Loop) to be able to perform Hybrid A/C service work. All Hybrid dealers will receive the J-43600-50, with installation instructions, as a component of the Hybrid essential tool package. Dealerships that do not sell Hybrids, but may need to service Hybrids, can obtain J-43600-50 from SPX Kent Moore. Refer to GM Bulletin 08-01-39-001 for the ACR2000 Hose Flush procedure. The High Voltage (HV) electric A/C compressor used on Two Mode Hybrid vehicles uses a Polyolester (POE) refrigerant oil instead of a Polyalkylene Glycol (PAG) synthetic refrigerant oil. This is due to the better electrical resistance of the POE oil and its ability to provide HV isolation. Failure to flush the hoses before adding refrigerant to a Hybrid vehicle with an electric A/C compressor may result in an unacceptable amount of PAG oil entering the refrigerant system. It may cause a Battery Energy Control Module Hybrid Battery Voltage System Isolation Lost Diagnostic Trouble Code (DTC P1AE7) to be set. Additionally, the A/C system warranty will be voided. Warranty Submission Requirements The Electronically Generated Repair Data (snapshot summary) and printer functions have been eliminated from the GE-48800. The VGA display and temperature probes were eliminated to reduce equipment costs. As a result, effective immediately the 18 digit "Snapshot/Charge Summary" code is no longer required for Air Conditioning (A/C) refrigerant system repairs that are submitted for warranty reimbursement. The charge summary data from before and after system repairs will continue to required, but documented on the repair order only. Both high and low pressures and the recovery and charge amounts should be noted during the repair and entered on the repair order. If using ACR2000 (J-43600), the "Snapshot/Charge Summary" printouts should continue to be attached to the shops copy of the repair order. The labor codes that are affected by this requirement are D3000 through D4500. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Refrigerant > Component Information > Technical Service Bulletins > A/C - Refrigerant Recovery/Recycling/Equipment > Page 10520 Refrigerant: Technical Service Bulletins A/C - Contaminated R134A Refrigerant Bulletin No.: 06-01-39-007 Date: July 25, 2006 INFORMATION Subject: Contaminated R134a Refrigerant Found on Market for Automotive Air-Conditioning Systems Models: 2007 and Prior GM Passenger Cars and Trucks (including Saturn) 2007 and Prior HUMMER H2, H3 2007 and Prior Saab 9-7X Attention: This bulletin should be directed to the Service Manager as well as the Parts Manager. Commercially Available Contaminated R134a Refrigerant Impurities have been found in new commercially available containers of R134a. High levels of contaminates may cause decreased performance, and be detrimental to some air-conditioning components. Accompanying these contaminates has been high levels of moisture. Tip: Excessive moisture may cause system concerns such as orifice tube freeze-up and reduced performance. Industry Reaction: New Industry Purity Standards Due to the potential availability of these lower quality refrigerants, the Society of Automotive Engineers (SAE), and the Air Conditioning and Refrigeration Industry (ARI) are in the process of instituting reliable standards that will be carried on the labels of future R134a refrigerant containers. This identifying symbol will be your assurance of a product that conforms to the minimum standard for OEM Automotive Air-Conditioning use. How Can You Protect Yourself Today? It is recommended to use GM or ACDelco(R) sourced refrigerants for all A/C repair work. These refrigerants meet General Motors own internal standards for quality and purity, insuring that your completed repairs are as good as the way it left the factory. Parts Information The part numbers shown are available through GMSPO or ACDelco(R). The nearest ACDelco(R) distributor in your area can be found by calling 1-800-223-3526 (U.S. Only). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Refrigerant > Component Information > Technical Service Bulletins > A/C - Refrigerant Recovery/Recycling/Equipment > Page 10521 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Refrigerant > Component Information > Technical Service Bulletins > A/C - Refrigerant Recovery/Recycling/Equipment > Page 10522 Refrigerant: Technical Service Bulletins A/C - Refrigerant Recovery/Recharge Equipment File In Section: 01 - HVAC Bulletin No.: 99-01-38-006A Date: May, 2000 WARRANTY ADMINISTRATION Subject: J-43600 ACR 2000 Essential Refrigerant Recovery/Recharge Equipment Models: 1993-2000 Passenger Cars and Light Duty Trucks with R-134a Refrigerant This bulletin is being revised to change the effective date and to update the text. Please discard Corporate Bulletin Number 99-01-38-006 (Section 01 - HVAC). Effective June 1, 2000, the use of J-43600 ACR 2000 will be required on all repairs that require A/C system recovery and are reimbursable by GM. Additionally, GM highly recommends that J-43600 ACR 2000 be used on all GM cars and trucks for customer paid A/C repairs. Important: Also effective June 1, 2000, the "Add" time for all air conditioning recovery is revised to 0.5 hours for front systems and 0.7 hours for front/rear dual systems (RPO C69 or C34). After June 1, 2000, all air conditioning claims submitted with the 0.9 hours "Add" time will be rejected for "labor hours excessive". After the completion of repairs (charging), the ACR 2000 will prompt the user to perform a snapshot of the air conditioning system operating data. The snapshot includes: ^ Maximum high side pressure. ^ Minimum low side pressure. ^ Duct outlet temperatures (2). ^ Refrigerant purity information. This information is captured on a paper printout and in a warranty code. For all GM paid repairs, the paper printout should be attached to the shop copy of the repair order. The warranty code must be submitted in the warranty claim information in the comments field. The code enables the reporting of valuable information about the repair to GM for product quality improvement. Claims submitted without this information may be subject to review and subsequent debit. The required use of J-43600 ACR 2000 raises the question of the acceptable uses for any existing recovery/recycle equipment that GM dealers are currently using. GM recognizes that many of the previously essential ACR4's are reaching the end of their useful life. There are several alternatives for existing equipment that may be considered: ^ Use the existing equipment as customer paid recovery only equipment. Example: Collision repair area. ^ Use the existing equipment as a scavenger unit for contaminated A/C systems. ^ Sell the existing units to repair facilities outside the GM dealer network. ^ Discontinue the use of the existing units if the repair/maintenance costs exceed the value of the equipment. ^ Donate the existing equipment to local technical schools. ^ Dedicate the ACR4 to A/C system flushing, using the J-42939 Flush Adapter. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Refrigerant > Component Information > Technical Service Bulletins > A/C - Refrigerant Recovery/Recycling/Equipment > Page 10523 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Refrigerant > Component Information > Technical Service Bulletins > A/C - Refrigerant Recovery/Recycling/Equipment > Page 10524 Technical Service Bulletin # 631209 Date: 960501 A/C - R12 or R134a Service Recommendations File In Section: 1 - HVAC Bulletin No.: 63-12-09 Date: May, 1996 INFORMATION Subject: Service Issues for Vehicles with R12 or R134a Air Conditioning Systems Models: 1988-96 Passenger Cars and Trucks R12 Service Recommendations As you know, production of R12 refrigerant ceased on December 31, 1995. Although R12 will no longer be manufactured, there is a reserve supply of R12 available. This reserve, along with strict A/C repair service adherence to proper refrigerant recycling procedures, should assure continued availability to meet consumers' needs. R12 can and should continue to be used to service vehicles built with R12 A/C systems as long as it is available. If R12 is no longer available or affordable, a system retrofit utilizing R134a is recommended. R134a IS THE ONLY SUBSTITUTE REFRIGERANT RECOMMENDED BY GM FOR USE IN GM VEHICLE A/C SYSTEMS, AND THEN ONLY AFTER FOLLOWING THE PROPER RETROFIT PROCEDURES FOR THE SPECIFIC MODEL. All new vehicle manufacturers have chosen R134a for retrofit. One of the key reasons is to protect both the service industry and consumers from the high costs that would result from purchasing equipment necessary to service multiple refrigerants. This position also reduces the threat of recycled refrigerant contamination. GM currently offers a simple, low cost R12 to R134a retrofit on many of its late model, front wheel drive passenger cars. Dealers should discuss this capability with owners of these specific models, listed in Retrofit Corporate Bulletin # 43-12-07D, whenever a repair to the A/C refrigerant system is required. Early retrofit of these specific models will aid in prolonging availability of the R12 supply and provide dealer service technicians the opportunity to become more familiar with the proper procedures for performing a retrofit. Remember - R12 and R134a refrigerant are not interchangeable! They cannot be mixed together. In fact, despite the claims of some refrigerant manufacturers, no proposed R12 refrigerant substitute can be added to, mixed with or used to "top off" an R12 system. Under provisions of law covering the service of refrigerants, mixing dissimilar refrigerant products during service is prohibited. To Summarize GM R12 Service Policy 1. Service R12 vehicles with good quality new or recycled R12 as long as it is available. 2. Purchase R12 from a reliable supplier. GMSPO has a supply of high quality R12 available. Dealers are requested to use only R12 supplied by GMSPO for warranty repairs. This high quality refrigerant will insure system performance and avoid the possibility of introducing contaminated material into the customer's A/C system. 3. Carefully test recovered R12 using the PureGuard monitor. On recovery equipment not protected by the PureGuard, always test the recovery cylinder prior to recharging a vehicle A/C system. 4. Discuss the R12 to R134a retrofit option with owners of GM vehicles listed in Retrofit Corporate Bulletin # 43-12-07D. Provide owner with a copy of the pamphlet "Converting Your Auto Air Conditioning System to Use the New Refrigerant". 5. Become familiar with retrofit procedures and exercise care in the handling of dissimilar refrigerants to prevent contamination. R134A Service Recommendations When servicing a previously retrofitted vehicle, there is concern that if all of the R12 is not completely removed prior to the retrofit procedure, it could contaminate your R134a equipment and recovery tank when a subsequent A/C repair is performed. Although the number of retrofits being performed today is minimal, the volume will increase as R12 prices rise. GM Service Technology Group is in the process of field testing a new R134a refrigerant purity tester similar to the PureGuard R12 refrigerant tester you now use. This new tool will mount to your ACR4 R134a Recovery Recycle and Recharge cart and sample all R134a refrigerant prior to recovery. It is expected that testing of this tool will be completed this year. This new tool, the Pureguard 2, will also test vehicles and your recycle tank for air contamination, which is threatening A/C system performance. High levels of air have been found in the recovery tanks on a number of R12 and R134a recovery carts. Air contamination is caused by improper recovery Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Refrigerant > Component Information > Technical Service Bulletins > A/C - Refrigerant Recovery/Recycling/Equipment > Page 10525 procedures and short-cutting refrigerant recycling times. Use the following procedure for testing and correcting air contamination in your A/C service equipment. 1. Make certain that the ACR4 equipment has not been used for at least 12 hours. It is recommended that the equipment be left in an area where the temperature will remain constant overnight to allow the temperature of the refrigerant in the tank to stabilize. 2. Record the surrounding air temperature next to the ACR4 refrigerant tank. Important: A major assumption is that the ambient air temperature next to the tank represents the refrigerant temperature in the tank. Failure to take care in measuring the temperature could result in unnecessary work. 3. Close both liquid (blue) and vapor (red) valves on the ACR4 tank. 4. Disconnect low side (blue) service hose from the back of the ACR4. 5. Slowly disconnect the tank vapor hose (red) from the back of the ACR4 and connect it to the low side service port. 6. Open the vapor (red) valve on the tank and record the tank pressure on the low side gage. 7. Restore hoses to the original position. 8. Referring to the Table, find the ambient temperature measured in Step 2. Compare the pressure reading from Step 6 to the "maximum allowable pressure". If the pressure reading from Step 6 is less than the "maximum allowable pressure", no further action is necessary. Important: The closer the tank pressure is to the desired tank pressure, the better the A/C system will perform. 9. If the pressure reading from Step 6 exceeds the maximum allowable pressure from the Table, open both tank valves and operate the ACR4 through 4 or 5 evacuation cycles. This will activate the automatic air purge to lower the tank pressure. Important: Station should not be connected to vehicle. 10. Repeat the tank pressure checking procedure the next day to determine if the pressure has been reduced to acceptable levels. If the tank pressure has been reduced but is not acceptable, cycle with ACR4 through more evacuation cycles and recheck the next day. Continue process until acceptable pressure is obtained. If the tank pressure is not reduced through the evacuation cycling, then Kent-Moore should be contacted at 1-800-345-2233. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Refrigerant > Component Information > Specifications > Capacity Specifications Refrigerant: Capacity Specifications A/C Refrigerant Capacity 2.25 lb (US) Refrigerant Type Refrigerant-134a Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Refrigerant > Component Information > Specifications > Capacity Specifications > Page 10528 Refrigerant: Fluid Type Specifications A/C Refrigerant Type Refrigerant-134a Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Refrigerant > Component Information > Specifications > Page 10529 Refrigerant: Description and Operation PURPOSE Like the coolant in the engine cooling system, the refrigerant is the substance in the air conditioning system that absorbs, carries, and then releases heat. Although various substances are used as refrigerants in other types of refrigeration systems, some automotive air conditioning systems use a type called Refrigerant-12 (R-12). This vehicle uses Refrigerant-134a (R-134a). It is a non-toxic1 non-flammable, clear, colorless liquefied gas. While the R-134a A/C system is very similar to an, R-12 A/C system, the differences in the refrigerant, lubricants, and service equipment are important. NOTICE:R-134a refrigerant is not compatible with R-12 refrigerant in an air conditioning system. R-12 in a R-134a system will cause compressor failure, refrigerant oil sludge or poor air conditioning system performance. Refrigerant-134a carries a charge of a special lubricant called polyalkaline glycol (PAG) refrigerant oil. GM (PAG) refrigerant oil has a slight blue tint. The oil is hydroscopic (absorbs water from the atmosphere). Store it in closed containers. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Refrigerant Oil > Component Information > Technical Service Bulletins > A/C - New PAG Oil Refrigerant Oil: Technical Service Bulletins A/C - New PAG Oil Bulletin No.: 02-01-39-004B Date: November 16, 2005 INFORMATION Subject: New PAG Oil Released Models: 2006 and Prior GM Passenger Cars and Trucks (Including Saturn) 2003-2006 HUMMER H2 2006 HUMMER H3 2005-2006 Saab 9-7X Built With R-134a Refrigeration System All Air Conditioning Compressor Types (Excluding R4 and A6 Type Compressors) Supercede: This bulletin is being revised to change the PAG oil part number used for R4 and A6 compressors with R-134a refrigerant systems. Please discard Corporate Bulletin Number 02-01-39-004A (Section 01 - HVAC). All General Motors vehicles built with R-134a refrigerant systems shall now be serviced with GM Universal PAG Oil (excluding vehicles equipped with an R4 or A6 compressor). R4 and A6 compressors with R-134a refrigerant systems shall use PAG OIL, GM P/N 12356151 (A/C Delco part number 15-118) (in Canada, use P/N 10953486). Important: The PAG oil referenced in this bulletin is formulated with specific additive packages that meet General Motors specifications and use of another oil may void the A/C systems warranty. Use this new PAG oil when servicing the A/C system on the vehicles listed above. Oil packaged in an 8 oz tube should be installed using A/C Oil Injector, J 45037. Refer to the HVAC Section of Service Information for detailed information on Oil Balancing and Capacities. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Refrigerant Oil > Component Information > Specifications > Capacity Specifications Refrigerant Oil: Capacity Specifications REFRIGERANT OIL DISTRIBUTION The Harrison HT-6 compressor system used on all models requires polyalkaline glycol (PAG) refrigerant oil in the quantities listed below: - Without Aux. A/C - 240 ml (8 fl oz) - With Aux. A/C - 330 ml (11 fl oz) New oil quantities must be added to the system during component replacement and conditions stated as follows: - With no signs of excessive oil leakage, add: A. All Compressors (drain and measure the oil) - If less than 30 ml (1 fl oz) is drained-add 60 ml (2 fl oz) to the new compressor. - If more than 30 ml (1 fl oz) is drained-add same amount that was drained to the new compressor. B. Accumulator-Add 105 ml (3.5 fl oz) of new oil to the replacement accumulator to compensate for oil retained by original accumulator desiccant and bag assemblies. The accumulator should only be replaced if leaking due to a perforation, damaged O-ring seal seat, or damaged threads. C. Evaporator-Add 90 ml (3 fl oz) of new refrigerant oil. D. Condenser-Add 30 ml (1 fl oz) of new refrigerant oil. REFRIGERANT OIL LOSS DUE TO A LARGE LEAK If the refrigerant charge is abruptly lost due to a large refrigerant leak, approximately 90 ml (3 fl oz) of refrigerant oil will be carried out of the system suspended in the refrigerant. Any failure that caused a abrupt refrigerant discharge will experience this oil loss. Failures that allow the refrigerant to seep or bleed off over time do not experience this oil loss. Upon replacement of a component that caused a large refrigerant leak, add 90 ml (3 fl oz) of new polyalkaline glycol (PAG) refrigerant oil plus the desired amount of oil for the particular component. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Refrigerant Oil > Component Information > Specifications > Capacity Specifications > Page 10536 Refrigerant Oil: Fluid Type Specifications REFRIGERANT OIL TYPE - R-134a PAG (Polyalkaline Glycol) synthetic refrigerant oil (GM Part No. 12345923) or equivalent. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Refrigerant Pressure Sensor / Switch, HVAC > A/C Pressure Sensor/Switch - Cooling Fan > Component Information > Locations A/C Pressure Sensor/Switch - Cooling Fan: Locations Front of Engine Compartment, on Condenser Manifold Tubing Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Relays and Modules - HVAC > Blower Motor Relay > Component Information > Locations > Blower Motor Relay High Front Blower Motor Relay: Locations Blower Motor Relay High Front Behind I/P Compartment Box on HVAC Plenum Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Relays and Modules - HVAC > Blower Motor Relay > Component Information > Locations > Blower Motor Relay High Front > Page 10546 Blower Motor Relay: Locations Blower Relay High Heater And Air Conditioning Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Relays and Modules - HVAC > Blower Motor Relay > Component Information > Locations > Blower Motor Relay High Front > Page 10547 Auxiliary Heater And Air Conditioning Wiring, Rear Under I/P, on top of HVAC Plenum Auxiliary Heater And Air Conditioning Wiring, Rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Relays and Modules - HVAC > Blower Motor Relay > Component Information > Locations > Blower Motor Relay High Front > Page 10548 Auxiliary Heater And Air Conditioning Wiring, Rear Medium Rear On Auxiliary Heater and A/C Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Relays and Modules - HVAC > Blower Motor Relay > Component Information > Locations > Page 10549 High Blower Relay Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Relays and Modules - HVAC > Blower Motor Relay > Component Information > Locations > Page 10550 Blower Motor Relay: Service and Repair 1 Screw, 2 Resistor, 3 Relay Bracket, 4 Relay Remove or Disconnect 1. Negative battery cable. 2. Instrument panel compartment. 3. Electrical connectors, as necessary. 4. Relay from relay bracket. Install or Connect 1. Relay to relay bracket. 2. Electrical connectors, as necessary. 3. Instrument panel compartment. 4. Negative battery cable. - Check circuit operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Relays and Modules - HVAC > Compressor Clutch Relay > Component Information > Locations Underhood Fuse-Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Relays and Modules - HVAC > Control Module HVAC > Component Information > Locations > Auxiliary System Control Module HVAC: Locations Auxiliary System Overhead Console Auxiliary Heater and A/C Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Relays and Modules - HVAC > Control Module HVAC > Component Information > Locations > Auxiliary System > Page 10558 Overhead Console Control Modules are attached to Control Assemblies. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Relays and Modules - HVAC > Control Module HVAC > Component Information > Locations > Auxiliary System > Page 10559 Control Module HVAC: Locations Blower Control Module HVAC Control Panel & Module Control Module is attached to Control Assembly. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Sensors and Switches - HVAC > Air Conditioning Switch > Component Information > Locations > Auxiliary Heater Control Switch, Rear Air Conditioning Switch: Locations Auxiliary Heater Control Switch, Rear I/P, Right of Steering Column Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Sensors and Switches - HVAC > Air Conditioning Switch > Component Information > Locations > Auxiliary Heater Control Switch, Rear > Page 10565 Air Conditioning Switch: Locations Rear Auxiliary Heater Control Switch in Headliner Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Sensors and Switches - HVAC > Air Conditioning Switch > Component Information > Locations > Auxiliary Heater Control Switch, Rear > Page 10566 Air Conditioning Switch: Locations Rear Auxiliary Heater/A/C Fan Switch in Headliner Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Sensors and Switches - HVAC > Air Conditioning Switch > Component Information > Diagrams > Heater and A/C Control Switch Air Conditioning Switch: Diagrams Heater and A/C Control Switch C1: Heater And A/C Control Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Sensors and Switches - HVAC > Air Conditioning Switch > Component Information > Diagrams > Heater and A/C Control Switch > Page 10569 C3: Heater And A/C Control Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Sensors and Switches - HVAC > Air Conditioning Switch > Component Information > Diagrams > Heater and A/C Control Switch > Page 10570 C300: Rear Body HARN To AUX. A/C Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Sensors and Switches - HVAC > Air Conditioning Switch > Component Information > Diagrams > Heater and A/C Control Switch > Page 10571 C401: Rear Body HARN To AUX A/C Switch HARN Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Sensors and Switches - HVAC > Blower Motor Switch > Component Information > Locations > Aux Fan Control Switch C227: TCC/Stop Lamp Switch Jumper, AUX Fan Control Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Sensors and Switches - HVAC > Blower Motor Switch > Component Information > Locations > Aux Fan Control Switch > Page 10576 Blower Motor Switch: Locations Fan Switch, Front At heater control. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Sensors and Switches - HVAC > Blower Motor Switch > Component Information > Locations > Aux Fan Control Switch > Page 10577 Cargo Lamp Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Sensors and Switches - HVAC > Blower Motor Switch > Component Information > Locations > Page 10578 C2: Heater Blower Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Sensors and Switches - HVAC > Blower Motor Switch > Component Information > Service and Repair > With Air Conditioning Blower Motor Switch: Service and Repair With Air Conditioning Control Assembly Remove or Disconnect 1. Instrument cluster trim. 2. Control assembly. - Release the retainers using a small screwdriver, then pull the control assembly out from the instrument panel. 3. Electrical connectors, as necessary. Install or Connect 1. Electrical connectors, as necessary. 2. Control assembly. - The control assembly snap-fits to the instrument panel. 3. Instrument cluster trim. Check circuit operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Sensors and Switches - HVAC > Blower Motor Switch > Component Information > Service and Repair > With Air Conditioning > Page 10581 Blower Motor Switch: Service and Repair W/O Air Conditioning Control Assembly Replacment Remove or Disconnect 1. Instrument cluster trim plate. 2. Control assembly by releasing the snap-fit retainers with a small screwdriver. 3. Electrical connection. 4. Cables from the control assembly by releasing retainers. 5. Blower switch. Remove the blower switch rotary knob and the retaining clip from the shaft of the blower switch. Install or Connect 1. Blower switch. A. Hold the blower switch in position and install the retaining clip. B. Install the blower switch rotary knob. 2. Cables to the control assembly. 3. Electrical connection. 4. Control assembly to the instrument panel by snapping in. 5. Instrument cluster trim plate. Check circuit operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Sensors and Switches - HVAC > Refrigerant Pressure Sensor / Switch, HVAC > A/C Pressure Sensor/Switch - Cooling Fan > Component Information > Locations A/C Pressure Sensor/Switch - Cooling Fan: Locations Front of Engine Compartment, on Condenser Manifold Tubing Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Heating and Air Conditioning > Service Port HVAC > Component Information > Locations Service Port HVAC: Locations The high pressure fitting is located either in the high pressure vapor line or muffler, while the low pressure fitting is located on the accumulator. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag(s) Arming and Disarming > System Information > Service and Repair > Air Bag Disarming and Arming Air Bag(s) Arming and Disarming: Service and Repair Air Bag Disarming and Arming Disabling the SIR System Fig. 1 Air Bag Two-way Connector DRIVER SIDE Many service procedures require the air bag system to be disabled to prevent accidental deployment. The air bag system can maintain sufficient voltage to cause deployment for up to 2 minutes after the ignition switch is turned off, the battery ground cable is disconnected or the DERM fuse is removed. If the inflator module is disconnected from the deployment loop by the following procedure, service can begin immediately without waiting for the 2 minute time period to elapse. 1. Turn steering wheel so that vehicle wheels are pointed straight ahead. 2. Turn ignition switch to Lock position and remove key. 3. Remove air bag fuse from fuse block. 4. Remove steering column filler panel. 5. Remove Connector Position Assurance (CPA) and disconnect yellow two-way connector at base of steering column, Fig. 1. PASSENGER SIDE 1. Remove air bag fuse from fuse block. Enabling the SIR System Driver Side 1. Turn ignition switch to LOCK and remove key. 2. Connect yellow two-way connector and install connector position assurance (CPA). 3. Install steering column filler panel. 4. Insert air bag fuse into fuse block. 5. Turn ignition switch to RUN and verify that the air bag warning lamp flashes seven times then turns off. Passenger Side 1. Turn ignition switch to LOCK and remove key. 2. Insert air bag fuse into fuse block. 3. Turn ignition switch to RUN and verify that the air bag warning lamp flashes seven times then turns off. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag(s) Arming and Disarming > System Information > Service and Repair > Air Bag Disarming and Arming > Page 10595 Air Bag(s) Arming and Disarming: Service and Repair General Service Precautions CAUTION: When performing service on or around SIR components or SIR wiring, follow the procedures listed below to temporarily disable the SIR system. Failure to follow procedures could result in possible air bag deployment, personal injury or otherwise unneeded SIR system repairs. The DERM can maintain sufficient voltage to cause a deployment for up to 2 minutes after the ignition switch is turned "OFF," the battery is disconnected, or the fuse powering the DERM is removed. Many of the service procedures require removal of the "AIR BAG" fuse, and disconnection of the inflator module from the deployment loop to avoid an accidental deployment. If the inflator module is disconnected from the deployment loop as noted in the "Disabling the SIR System" procedure that follows, service can begin immediately without waiting for the 2 minute time period to expire. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag > Component Information > Technical Service Bulletins > Air Bag - Module Shipping/Return Procedure Air Bag: Technical Service Bulletins Air Bag - Module Shipping/Return Procedure File In Section: 9 - Accessories Bulletin No.: 31-90-04A Date: September, 1996 Subject: Supplemental Inflatable Restraint (SIR) Module Shipping/Return Procedure Models: 1993-97 Passenger Cars and Trucks - Equipped with Supplemental Inflatable Restraint (SIR) Modules EXCEPT THE MODELS AND YEARS AS LISTED This bulletin is being revised to update the: models and years affected, the contact telephone numbers and the hazardous classification rating. Various areas of the text and the attachments have also been revised. Please discard Corporate Bulletin Number 319004 (Group Reference Accessories). This bulletin outlines the return procedure for undeployed Supplemental Inflatable Restraint (SIR) modules. Undeployed SIR modules in all vehicles (except models indicated), removed for warranty purposes, are to be returned to Delphi Interior and Lighting Systems, General Motors Corporation. This bulletin outlines procedures that all dealers must follow for shipping undeployed airbag modules. This bulletin is in effect and should be retained at all times at the dealership until superseded by a subsequent bulletin. This return program does NOT apply to dealers in Alaska, Hawaii, US Territories, and foreign countries. SIR modules replaced outside the continental United States should be deployed and disposed of following the procedure outlined in Corporate Bulletin Number 319003R. All other modules (i.e., out of warranty or car scrapped) should be disposed of per Corporate Bulletin Number 319003R. Important: If a vehicle is the subject of a Preliminary Investigation (GM-1241), DO NOT ALTER the SIR system until cleared by the Zone Service Representative. An SIR module returned following a 1241 investigation must be clearly designated by: 1. Indicating on the REPAIR ORDER copy inside the box "SUBJECT TO 1241". 2. Indicating the VIN and vehicle owner on the REPAIR ORDER. 3. Sending photocopies of the REPAIR ORDER to: a. The appropriate Zone service Representative b. Cigna Company GM Central Claims Unit 485 W. Milwaukee Suite 690 Detroit, MI 48202 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag > Component Information > Technical Service Bulletins > Air Bag - Module Shipping/Return Procedure > Page 10600 Mailing Address: P.O. Box 02489, Detroit, MI 48202 Questions related to handling of 1241 associated SIR modules may be answered by calling: Cigna Company - GM Central Claims Unit, 1-800-888-1491. The U.S. Department of Transportation (DOT) Hazardous Materials Regulations classify SIR modules as the following: ^ Proper Shipping Name: Air Bag Modules ^ Hazardous Class: Class 9 - Air Bag Failure to comply with DOT regulations will result in civil penalties of up to $10,000 per violation or criminal penalties of up to $25,000 per violation and imprisonment. Return Procedure for Supplemental Inflatable Restraint Modules (Undeployed Modules Only) All undeployed SIR modules in all vehicles (except as indicated in the models section of this bulletin), removed for warranty purposes, are to be returned to Delphi Interior and Lighting Systems, General Motors. The following procedure should be followed when returning SIR modules from any location within the continental United States. 1. Packaging Requirements Return undeployed SIR modules in the same carton that was received with the new replacement module. Do not use any carton that has been damaged to the extent that the product will not be protected during the shipment. If you need a replacement carton, contact Delphi Interior and Lighting Systems at (513) 356-2426. ENCLOSE A COPY OF THE REPAIR ORDER, detailing the reason(s) for the SIR module replacement. Close and secure the carton with packaging tape (transparent tape is recommended). All existing labels and markings on the carton must be visible. Important: DO NOT staple container. DO NOT cover any portion of the black and white "Class 9" label or any markings on the carton. 2. Package Labels and Markings Add the names and addresses for the consignee and the consignor. The method of closure cannot interfere with the labels or the markings on the package (see Attachments "A" - Driver Side, and "D" - Passenger Side). 3. Shipping Paper (UPS Hazardous Material Label and Shipper's Certification) The following items on the shipping papers must be completed with the same information as enclosed with the replacement SIR module when received: proper shipping name, hazard class, identification number, packaging group number, "EX" number, and emergency response telephone number. The remaining information should be completed in accordance with Attachments "B" and "E" (Driver Side) and "C" and "F" (Passenger Side). A copy of the emergency response guidelines (see Attachment "G") is enclosed with the replacement SIR module and must be attached to the shipping papers you complete for the SIR module being shipped. 4. Transportation All SIR modules are to be returned using United Parcel Service (UPS) which will require the sender to pre-pay the freight charges. If difficulties arise, contact Delphi Interior and Lighting Systems, General Motors at (513) 356-2426. 5. RETURN ALL SUPPLEMENTAL INFLATABLE RESTRAINT MODULES (EXCEPT FOR THOSE MODELS LISTED IN THIS BULLETIN) TO THE FOLLOWING ADDRESS: Delphi Interior and Light Systems 3249 McCall Avenue Dayton, OH 45417 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag > Component Information > Technical Service Bulletins > Air Bag - Module Shipping/Return Procedure > Page 10601 ATTACHMENT A DRIVER AIRBAG Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag > Component Information > Technical Service Bulletins > Air Bag - Module Shipping/Return Procedure > Page 10602 ATTACHMENT B DRIVER SIDE Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag > Component Information > Technical Service Bulletins > Air Bag - Module Shipping/Return Procedure > Page 10603 ATTACHMENT C DRIVER SIDE Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag > Component Information > Technical Service Bulletins > Air Bag - Module Shipping/Return Procedure > Page 10604 ATTACHMENT D PASSENGER AIRBAG Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag > Component Information > Technical Service Bulletins > Air Bag - Module Shipping/Return Procedure > Page 10605 ATTACHMENT E PASSENGER SIDE Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag > Component Information > Technical Service Bulletins > Air Bag - Module Shipping/Return Procedure > Page 10606 ATTACHMENT F PASSENGER SIDE Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag > Component Information > Technical Service Bulletins > Air Bag - Module Shipping/Return Procedure > Page 10607 ATTACHMENT G Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag > Component Information > Locations > Driver Inflator Module Steering Column Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag > Component Information > Locations > Driver Inflator Module > Page 10610 Air Bag: Locations Steering Wheel Air Bag Inflator Module Center of Steering Wheel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag > Component Information > Locations > Page 10611 Air Bag: Description and Operation The inflator module is located on the steering wheel hub. It consists of an inflatable bag and an inflator (gas canister). In the event of a frontal collision, current flows through the deployment loop, igniting the gas producing material in the inflator module and rapidly inflating the air bag. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag > Component Information > Service and Repair > Ball Lock Fastener Type Air Bag: Service and Repair Ball Lock Fastener Type INFLATOR MODULE REPLACEMENT SIR (BALL LOCK FASTENER TYPE) CAUTION: When performing service on or around Supplemental Inflatable Restraint (SIR) components or wiring, follow the procedures listed below to temporarily disable the SIR system. Failure to follow procedures could result in possible SIR bag deployment, personal injury, or otherwise unneeded SIR system repairs. REMOVE OR DISCONNECT Inflator Module Components (Ball Lock Type) 1. Disable the SIR system. See: Air Bag(s) Arming and Disarming/Service and Repair 2. Negative battery cable. 3. Turn steering wheel 90 degrees to access rear shroud holes to inflator module. 4. Release each of four ball lock fasteners by pushing a ball-point pen or similar device into the end of each fastener through the holes in the steering shroud. 5. Inflator module (tilt rearward from the top to access SIR wiring). 6. SIR lead wire from clip on inflator module. 7. SIR lead wire from clip on steering wheel. 8. Connector position assurance (CPA) and retainer from the inflator module. CAUTION: When carrying a live inflator module, make sure the bag opening is pointed away from you. In case of accidental deployment, the bag will then deploy with a minimal chance of personal injury. Never carry the inflator module by the wires or connectors on the underside of the module. When placing a live Inflator module on a bench or other surface, always face the bag and trim cover up, away from the surface. This is necessary so that a free space is provided to allow the air bag to expand in the unlikely event of accidental deployment. Never rest a steering column assembly on the steering wheel with the inflator module face down and the column vertical. Otherwise, personal injury may result. INSTALL OR CONNECT 1. SIR connector (CPA) and retainer to the inflator module. 2. SIR lead wire to clip on steering wheel. 3. SIR lead wire to clip on inflator module. 4. Inflator module by pressing it firmly into steering wheel enough to engage and latch all four ball lock fasteners. Do not pinch the wires. NOTICE: it may be necessary to reset the ball lock fasteners by using a ball-point pen or similar device. 5. Negative battery cable. 6. Enable the SIR system. See: Air Bag(s) Arming and Disarming/Service and Repair Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag > Component Information > Service and Repair > Ball Lock Fastener Type > Page 10614 Air Bag: Service and Repair Leaf Spring and Notched Pin Type WARNING: When performing service on or around Supplemental Inflatable Restraint (SIR) components or wiring, follow the procedures listed below to temporarily disable the SIR system. Failure to follow procedures could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. REMOVE OR DISCONNECT 1. Disable the SIR system. See: Air Bag(s) Arming and Disarming/Service and Repair 2. Negative battery cable. 3. Turn steering wheel 90° to access rear shroud holes to inflator module. 4. Insert screw driver and push leaf spring to release pin. 5. Turn steering wheel 180° to access remaining rear shroud holes. 6. Insert screw driver and push leaf spring to release pin. 7. Inflator module (tilt rearward from the top to access SIR wiring). 8. SIR lead wire from clip on inflator module. 9. SIR lead wire from clip on steering wheel. 10. Connector Position Assurance (CPA) and retainer from the inflator module. WARNING: When carrying a live inflator module, make sure the bag opening is pointed away from you. In case of accidental deployment, the bag will then deploy with a minimal chance of personal injury. Never carry the inflator module by the wires or connectors on the underside of the module. When placing a alive inflator module on a bench or other surface, always face the bag and trim cover up, away from the surface. This is necessary so that a tree apace la provided to allow the air bag to expand in the unlikely event of accidental deployment. Never rest a steering column assembly on the steering wheel with the inflator module face down and the column vertical. Otherwise, personal injury may result. CAUTION: Always use the correct fastener in the proper location. When you replace a fastener, use ONLY the exact part number for that application. The manufacturer will call out those fasteners that require a replacement after removal. The manufacturer will also call out the fasteners that require thread lockers or thread sealant. UNLESS OTHERWISE SPECIFIED, do not use supplemental coatings (paints, greases, or other corrosion Inhibitors) on threaded fasteners or fastener joint interfaces. Generally, such coatings adversely affect the fastener torque and joint clamping force, and may damage the fastener. When you install fasteners, use the correct tightening sequence and specifications. Following these instructions can help you avoid damage to parts and systems. INSTALL OR CONNECT 1. CPA and retainer to the inflator module. 2. SIR lead wire to clip on steering wheel. 3. SIR lead wire to clip on inflator module. 4. Inflator module by pressing it firmly into steering wheel enough to engage and latch all four notched pins in the leaf spring. Do not pinch the wires. 5. Negative battery cable. 6. Enable the SIR system. See: Air Bag(s) Arming and Disarming/Service and Repair Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag Control Module > Component Information > Locations > System Component Locations Air Bag Control Module: Locations System Component Locations Fig. 4 Air Bag System Component Locations Refer to Fig. 4 for air bag system component locations. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag Control Module > Component Information > Locations > System Component Locations > Page 10619 Air Bag Control Module: Locations Diagnostic Energy Reserve Module (DERM) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag Control Module > Component Information > Locations > System Component Locations > Page 10620 Cargo Lamp Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag Control Module > Component Information > Locations > Page 10621 Description Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag Control Module > Component Information > Locations > Page 10622 Air Bag Control Module: Description and Operation A function of the DERM is to supply the deployment loop with a 36 volt loop reserve to ensure sufficient energy to deploy the air bag if the ignition feed to the arming sensor is lost during a frontal collision. Another function of the DERM is electrical system diagnostics. The DERM can detect circuit and component malfunctions within the deployment loop. Voltage drops across components within the loop are measured during non-deployment conditions. If the monitored voltages fall outside of the expected limits, the DERM will indicate a malfunction through the storage of a diagnostic trouble code and the illumination of the air bag warning light. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag Control Module > Component Information > Locations > Page 10623 Air Bag Control Module: Service and Repair Prior to performing replacement procedures, disarm air bag system. Refer to, Service and Repair/ Air Bag System Disarming & Air Bag System Arming. Refer to, / Specifications/ Mechanical for torque values when installing components. All sensors and mounting bracket bolts must be carefully torqued to assure proper operation. Never power up the air bag system when any sensor is not rigidly attached to the vehicle, since the sensor could be activated when not attached, causing air bag deployment. Do not open DERM case for any reason. Touching connector pins or soldered components may cause electrostatic discharge damage. Repair of a malfunctioning DERM is by replacement only. 1. Remove DERM from mounting bracket. 2. Remove Connector Position Assurance (CPA) lock, then disconnect DERM electrical connector from DERM. 3. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Air Bag Safety Switch/Connector > Component Information > Locations Steering Column Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Clockspring Assembly / Spiral Cable, Air Bag > Component Information > Description and Operation Clockspring Assembly / Spiral Cable: Description and Operation The coil assembly consists of two current carrying coils. They are attached to the steering column and allow rotation of the steering wheel while maintaining continuous contact of the deployment loop to the inflator module. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Impact Sensor > Component Information > Locations > Arming Sensor Impact Sensor: Locations Arming Sensor Inside LH Frame Rail, below Driver's Door Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Impact Sensor > Component Information > Locations > Arming Sensor > Page 10634 Impact Sensor: Locations RH Front Discriminating Sensor RH Front outside of RH Frame Rail Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Impact Sensor > Component Information > Locations > Arming Sensor > Page 10635 Impact Sensor: Locations LH Front Discriminating Sensor Front outside of LH Frame Rail Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Impact Sensor > Component Information > Locations > Page 10636 I/P HARN To Arming Sensor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Impact Sensor > Component Information > Description and Operation > Arming Sensor Impact Sensor: Description and Operation Arming Sensor The arming sensor is a protective switch located in the power side of the deployment loop. It is calibrated to close at low level speed changes. This ensures that the inflator module is connected directly to the 36 Volt Loop Reserve (VLR) output of the DERM when either of the discriminating sensors close. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Impact Sensor > Component Information > Description and Operation > Arming Sensor > Page 10639 Impact Sensor: Description and Operation Discriminating Sensors There are two discriminating sensors in the air bag system. They are wired in parallel on the low (ground) side of the deployment loop. These sensors are calibrated to close with speed changes severe enough to warrant deployment. A diagnostic resistor is connected in parallel with the switch contacts within each of the discriminating sensors. These parallel resistors supply the ground path for the current passing through the deployment loop during normal operation. This current flow results in voltage drops across each component in the deployment loop. The DERM monitors these voltage drops to detect malfunctions. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Impact Sensor > Component Information > Service and Repair > Arming Sensor Impact Sensor: Service and Repair Arming Sensor Prior to performing replacement procedures, disarm air bag system. Refer to, Service and Repair/ Air Bag System Disarming & Air Bag System Arming. Refer to, / Specifications/ Mechanical for torque values when installing components. All sensors and mounting bracket bolts must be carefully torqued to assure proper operation. Never power up the air bag system when any sensor is not rigidly attached to the vehicle, since the sensor could be activated when not attached, causing air bag deployment. 1. disconnect sensor electrical connector from retainer, remove Connector Position Assurance (CPA) lock from connector, then disconnect connector. 2. Remove sensor mounting bolts and sensor from vehicle. 3. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Impact Sensor > Component Information > Service and Repair > Arming Sensor > Page 10642 Impact Sensor: Service and Repair Forward Discriminating Sensor Prior to performing replacement procedures, disarm air bag system. Refer to, Service and Repair/ Air Bag System Disarming & Air Bag System Arming. Refer to, / Specifications/ Mechanical for torque values when installing components. All sensors and mounting bracket bolts must be carefully torqued to assure proper operation. Never power up the air bag system when any sensor is not rigidly attached to the vehicle, since the sensor could be activated when not attached, causing air bag deployment. 1. Disconnect sensor electrical connector from retainer, then remove connector from Connector Position Assurance (CPA) lock and disconnect. 2. Remove sensor mounting bolts, then the sensor from vehicle. 3. Reverse procedure to install. Ensure arrow is pointed toward front of vehicle. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Seat Occupant Sensor > Component Information > Technical Service Bulletins > Restraints - Passenger Presence System Information Seat Occupant Sensor: Technical Service Bulletins Restraints - Passenger Presence System Information INFORMATION Bulletin No.: 06-08-50-009F Date: December 23, 2010 Subject: Information on Passenger Presence Sensing System (PPS or PSS) Concerns With Custom Upholstery, Accessory Seat Heaters or Other Comfort Enhancing Devices Models: 2011 and Prior GM Passenger Cars and Trucks Equipped with Passenger Presence Sensing System Supercede: This bulletin is being revised to update the model years. Please discard Corporate Bulletin Number 06-08-50-009E (Section 08 - Body and Accessories). Concerns About Safety and Alterations to the Front Passenger Seat Important ON A GM VEHICLE EQUIPPED WITH A PASSENGER SENSING SYSTEM, USE THE SEAT COVERS AND OTHER SEAT-RELATED EQUIPMENT AS RELEASED BY GM FOR THAT VEHICLE. DO NOT ALTER THE SEAT COVERS OR SEAT-RELATED EQUIPMENT. ANY ALTERATIONS TO SEAT COVERS OR GM ACCESSORIES DEFEATS THE INTENDED DESIGN OF THE SYSTEM. GM WILL NOT BE LIABLE FOR ANY PROBLEMS CAUSED BY USE OF SUCH IMPROPER SEAT ALTERATIONS, INCLUDING ANY WARRANTY REPAIRS INCURRED. The front passenger seat in many GM vehicles is equipped with a passenger sensing system that will turn off the right front passenger's frontal airbag under certain conditions, such as when an infant or child seat is present. In some vehicles, the passenger sensing system will also turn off the right front passenger's seat mounted side impact airbag. For the system to function properly, sensors are used in the seat to detect the presence of a properly-seated occupant. The passenger sensing system may not operate properly if the original seat trim is replaced (1) by non-GM covers, upholstery or trim, or (2) by GM covers, upholstery or trim designed for a different vehicle or (3) by GM covers, upholstery or trim that has been altered by a trim shop, or (4) if any object, such as an aftermarket seat heater or a comfort enhancing pad or device is installed under the seat fabric or between the occupant and the seat fabric. Aftermarket Seat Heaters, Custom Upholstery, and Comfort Enhancing Pads or Devices Important ON A GM VEHICLE EQUIPPED WITH A PASSENGER SENSING SYSTEM, USE ONLY SEAT COVERS AND OTHER SEAT-RELATED EQUIPMENT RELEASED AS GM ACCESSORIES FOR THAT VEHICLE. DO NOT USE ANY OTHER TYPE OF SEAT COVERS OR SEAT-RELATED EQUIPMENT, OR GM ACCESSORIES RELEASED FOR OTHER VEHICLE APPLICATIONS. GM WILL NOT BE LIABLE FOR ANY PROBLEMS CAUSED BY USE OF SUCH IMPROPER SEAT ACCESSORIES, INCLUDING ANY WARRANTY REPAIRS MADE NECESSARY BY SUCH USE. Many types of aftermarket accessories are available to customers, upfitting shops, and dealers. Some of these devices sit on top of, or are Velcro(R) strapped to the seat while others such as seat heaters are installed under the seat fabric. Additionally, seat covers made of leather or other materials may have different padding thickness installed that could prevent the Passenger Sensing System from functioning properly. Never alter the vehicle seats. Never add pads or other devices to the seat cushion, as this may interfere with the operation of the Passenger Sensing System and either prevent proper deployment of the passenger airbag or prevent proper suppression of the passenger air bag. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Malfunction Lamp / Indicator, Air Bag > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Lamp / Indicator: > 83-81-34 > Mar > 99 > SIR - Operating Vehicle with Warning Light On Malfunction Lamp / Indicator: Customer Interest SIR - Operating Vehicle with Warning Light On File In Section: 8 - Chassis/Body Electrical Bulletin No.: 83-81-34 Date: March, 1999 INFORMATION Subject: Operating Vehicle with Supplemental Inflatable Restraint (SIR) Warning Light Illuminated Models: 1999 and Prior Passenger Cars and Light Duty Trucks with SDM Controlled Air Bag System The AIR BAG warning light is the key to driver notification of Supplemental Inflatable Restraint (SIR) system malfunctions. When the warning light remains illuminated or continues to flash, one or more of the following conditions may occur if vehicle operation is continued. ^ Non-deployment of the air bags in the event of a crash. ^ Deployment of the air bags without a crash. ^ Deployment of the air bags in crashes less severe than intended. If an AIR BAG warning light is illuminated or flashing, you should advise the customer of these possibilities and that the vehicle should be serviced right away. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Malfunction Lamp / Indicator, Air Bag > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Lamp / Indicator: > 83-81-34 > Mar > 99 > SIR - Operating Vehicle with Warning Light On Malfunction Lamp / Indicator: All Technical Service Bulletins SIR - Operating Vehicle with Warning Light On File In Section: 8 - Chassis/Body Electrical Bulletin No.: 83-81-34 Date: March, 1999 INFORMATION Subject: Operating Vehicle with Supplemental Inflatable Restraint (SIR) Warning Light Illuminated Models: 1999 and Prior Passenger Cars and Light Duty Trucks with SDM Controlled Air Bag System The AIR BAG warning light is the key to driver notification of Supplemental Inflatable Restraint (SIR) system malfunctions. When the warning light remains illuminated or continues to flash, one or more of the following conditions may occur if vehicle operation is continued. ^ Non-deployment of the air bags in the event of a crash. ^ Deployment of the air bags without a crash. ^ Deployment of the air bags in crashes less severe than intended. If an AIR BAG warning light is illuminated or flashing, you should advise the customer of these possibilities and that the vehicle should be serviced right away. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Air Bag Systems > Malfunction Lamp / Indicator, Air Bag > Component Information > Technical Service Bulletins > Page 10660 Malfunction Lamp / Indicator: Description and Operation The warning lamp will illuminate if there is an air bag system malfunction. Ignition voltage is supplied to the air bag warning lamp when the ignition switch is in the RUN or START positions. The DERM controls the lamp by providing a ground with the lamp driver. The air bag warning lamp will flash seven times when the ignition switch is first turned on to verify DERM operation. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Head Restraint System > System Information > Technical Service Bulletins > Restraints - Driver/Passenger Seat Head Rest Information Head Restraint System: Technical Service Bulletins Restraints - Driver/Passenger Seat Head Rest Information INFORMATION Bulletin No.: 10-08-50-003A Date: March 24, 2011 Subject: Information on Driver or Passenger Seat Head Restraint Concerns with Comfort, Custom Upholstery or Other Comfort Enhancing Devices Models: 2012 and Prior GM Passenger Cars and Trucks Equipped with Adjustable Head Restraints Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 10-08-50-003 (Section 08 - Body and Accessories). Important ON A GM VEHICLE EQUIPPED WITH ADJUSTABLE HEAD RESTRAINTS, USE THE HEAD RESTRAINT COVERS, FOAM AND OTHER SEAT-RELATED EQUIPMENT AS RELEASED BY GM FOR THAT VEHICLE. DO NOT ALTER OR REPOSITION THE HEAD RESTRAINT SYSTEM. ANY ALTERATIONS TO HEAD RESTRAINTS DEFEATS THE INTENDED DESIGN OF THE SYSTEM. GM WILL NOT BE LIABLE FOR ANY PROBLEMS CAUSED BY USE OF SUCH IMPROPER DESIGN ALTERATIONS, INCLUDING ANY WARRANTY REPAIRS INCURRED. You may have a customer with a concern that the head restraint is uncomfortable or sits too far forward. The front driver and passenger seats are equipped with head restraints that have been designed to help minimize injuries while still providing comfort to the occupants. Each GM vehicle has its own specifically designed head restraint. The head restraints should only be used in the vehicle for which they were designed. The head restraint will not operate to its design intent if the original foam is replaced (1) by non-GM foam or head restraint, (2) by GM foam or head restraint designed for a different vehicle, (3) by GM foam or head restraint that has been altered by a trim shop or (4) if any object, such as an aftermarket comfort enhancing pad or device, is installed. Never modify the design of the head restraint or remove the head restraint from the vehicle as this may interfere with the operation of the seating and restraint systems and may prevent proper positioning of the passenger within the vehicle. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Relays and Modules - Restraint Systems > Air Bag Control Module > Component Information > Locations > System Component Locations Air Bag Control Module: Locations System Component Locations Fig. 4 Air Bag System Component Locations Refer to Fig. 4 for air bag system component locations. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Relays and Modules - Restraint Systems > Air Bag Control Module > Component Information > Locations > System Component Locations > Page 10670 Air Bag Control Module: Locations Diagnostic Energy Reserve Module (DERM) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Relays and Modules - Restraint Systems > Air Bag Control Module > Component Information > Locations > System Component Locations > Page 10671 Cargo Lamp Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Relays and Modules - Restraint Systems > Air Bag Control Module > Component Information > Locations > Page 10672 Description Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Relays and Modules - Restraint Systems > Air Bag Control Module > Component Information > Locations > Page 10673 Air Bag Control Module: Description and Operation A function of the DERM is to supply the deployment loop with a 36 volt loop reserve to ensure sufficient energy to deploy the air bag if the ignition feed to the arming sensor is lost during a frontal collision. Another function of the DERM is electrical system diagnostics. The DERM can detect circuit and component malfunctions within the deployment loop. Voltage drops across components within the loop are measured during non-deployment conditions. If the monitored voltages fall outside of the expected limits, the DERM will indicate a malfunction through the storage of a diagnostic trouble code and the illumination of the air bag warning light. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Relays and Modules - Restraint Systems > Air Bag Control Module > Component Information > Locations > Page 10674 Air Bag Control Module: Service and Repair Prior to performing replacement procedures, disarm air bag system. Refer to, Service and Repair/ Air Bag System Disarming & Air Bag System Arming. Refer to, / Specifications/ Mechanical for torque values when installing components. All sensors and mounting bracket bolts must be carefully torqued to assure proper operation. Never power up the air bag system when any sensor is not rigidly attached to the vehicle, since the sensor could be activated when not attached, causing air bag deployment. Do not open DERM case for any reason. Touching connector pins or soldered components may cause electrostatic discharge damage. Repair of a malfunctioning DERM is by replacement only. 1. Remove DERM from mounting bracket. 2. Remove Connector Position Assurance (CPA) lock, then disconnect DERM electrical connector from DERM. 3. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Seat Belt Systems > Air Bag(s) Arming and Disarming > System Information > Service and Repair > Air Bag Disarming and Arming Air Bag(s) Arming and Disarming: Service and Repair Air Bag Disarming and Arming Disabling the SIR System Fig. 1 Air Bag Two-way Connector DRIVER SIDE Many service procedures require the air bag system to be disabled to prevent accidental deployment. The air bag system can maintain sufficient voltage to cause deployment for up to 2 minutes after the ignition switch is turned off, the battery ground cable is disconnected or the DERM fuse is removed. If the inflator module is disconnected from the deployment loop by the following procedure, service can begin immediately without waiting for the 2 minute time period to elapse. 1. Turn steering wheel so that vehicle wheels are pointed straight ahead. 2. Turn ignition switch to Lock position and remove key. 3. Remove air bag fuse from fuse block. 4. Remove steering column filler panel. 5. Remove Connector Position Assurance (CPA) and disconnect yellow two-way connector at base of steering column, Fig. 1. PASSENGER SIDE 1. Remove air bag fuse from fuse block. Enabling the SIR System Driver Side 1. Turn ignition switch to LOCK and remove key. 2. Connect yellow two-way connector and install connector position assurance (CPA). 3. Install steering column filler panel. 4. Insert air bag fuse into fuse block. 5. Turn ignition switch to RUN and verify that the air bag warning lamp flashes seven times then turns off. Passenger Side 1. Turn ignition switch to LOCK and remove key. 2. Insert air bag fuse into fuse block. 3. Turn ignition switch to RUN and verify that the air bag warning lamp flashes seven times then turns off. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Seat Belt Systems > Air Bag(s) Arming and Disarming > System Information > Service and Repair > Air Bag Disarming and Arming > Page 10680 Air Bag(s) Arming and Disarming: Service and Repair General Service Precautions CAUTION: When performing service on or around SIR components or SIR wiring, follow the procedures listed below to temporarily disable the SIR system. Failure to follow procedures could result in possible air bag deployment, personal injury or otherwise unneeded SIR system repairs. The DERM can maintain sufficient voltage to cause a deployment for up to 2 minutes after the ignition switch is turned "OFF," the battery is disconnected, or the fuse powering the DERM is removed. Many of the service procedures require removal of the "AIR BAG" fuse, and disconnection of the inflator module from the deployment loop to avoid an accidental deployment. If the inflator module is disconnected from the deployment loop as noted in the "Disabling the SIR System" procedure that follows, service can begin immediately without waiting for the 2 minute time period to expire. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Seat Belt Systems > Child Restraint > Child Seat Tether Attachment > Component Information > Technical Service Bulletins > Restraints - Child Seat Top Teather Attachment Kits Child Seat Tether Attachment: Technical Service Bulletins Restraints - Child Seat Top Teather Attachment Kits Bulletin No.: 99-09-40-004a Date: April 12, 2005 INFORMATION Subject: Top Tether Hardware Package for Child Restraint Seats Models: 1989-2002 Passenger Cars, Light Duty Trucks and Multi-Purpose Passenger Vehicles (Except EV1 and Prizm) Supercede: This bulletin is being revised to add the 2000-2002 model years. Please discard Corporate Bulletin Number 99-09-40-009 (Section 09 - Restraints). Important: GM of Canada and IPC Dealers are not authorized to utilize this service bulletin. Beginning in August, 1997 General Motors began providing Child Restraint Seat Top Tether Hardware Packages to customers in the United States who requested them. The Top Tether Hardware Package contains the necessary hardware for anchoring a forward facing child restraint seat top tether. One Child Restraint Seat Top Tether Hardware Package will be provided per vehicle to the retail customer at no charge for installation. Charges for installation of additional Top Tether Hardware Packages per vehicle are the responsibility of the customer. Most forward facing child restraint seats (CRS) sold in the United States prior to calendar year 1999 were not sold with top tether straps, but have provisions for them. Top tethers, which are required in Canada, can help to better secure the seat in the vehicle. When a forward facing CRS including a top tether is used, specially designed components must be used to secure the child seat top tether. These components are included in the Hardware Package from GMSPO. Top tethers are not normally required or used with rearward facing infant restraint seats. Rearward facing infant restraint seats should never be secured in the front seat of an air bag equipped vehicle unless the vehicle is equipped with an air bag de-activation (shut-off) switch and the switch has been used to turn the air bag off. Should a retail customer request installation of a Tether Hardware Package at the time of sale or delivery, it is to be installed at no charge to the owner. The labor to install a Tether Hardware Package prior to delivery of a new vehicle to the customer is considered to be part of the delivery "get ready process", and as such, is not claimable. Claiming for the cost and applicable handling allowance of the proper Tether Hardware Package used in the installation is allowed. If the customer requests installation of a Tether Hardware Package some time after delivery, the package is to be provided free of charge. Hardware Packages include installation instructions which are easily followed and can be installed by most customers. However, should the customer request the dealership's assistance to install the Tether Hardware Package, it is to be installed at no charge to the customer and the labor may be claimed. All claims submitted for installation labor of an approved Tether Hardware Package must be supported by a signed customer work order. Additional Hardware Packages and installation charges are the responsibility of the customer. In addition, passenger vehicle deliveries, including vans and sport utilities for daily rental usage, may have one tether hardware package supplied. Additional packages are the owner's responsibility. Dealers may claim appropriate parts under these circumstances. Sufficient quantities of parts should be ordered in advance of the arrival of vehicles to avoid delays. Important: When installing a Child Restraint Seat Top Tether Hardware Package, follow the installation instructions included in the package. Additional information about specific mounting locations and installations may be available in the Seat Belt Section (Sections 9, 10-10, 10-11 or 10A) I of the appropriate Service Manual, or the Restraints section of SI. Any questions regarding this policy should be directed to your Area Manager, Parts or Service. Parts Information For Top Tether Hardware Package part numbers and usage, see Group 14.870 (passenger cars & U-van), or Group 16.710 (Light Duty Truck) of the appropriate GMSPO Parts Catalog. In addition, they can also be found in Accessories Group 21.042. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Seat Belt Systems > Child Restraint > Child Seat Tether Attachment > Component Information > Technical Service Bulletins > Restraints - Child Seat Top Teather Attachment Kits > Page 10686 Warranty Information The dealership will be reimbursed for the parts and labor, if applicable, through the submission of a regular warranty claim. All claims submitted must be supported by a signed customer work order. Purchase and installation of additional Hardware Packages is the responsibility of the customer. For Top Tether Hardware Packages installed in the United States, submit as a normal warranty claim using the labor operations and time allowances shown. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Seat Belt Systems > Seat Belt > Component Information > Technical Service Bulletins > Recalls for Seat Belt: > NHTSA97V096000 > Jun > 97 > Recall 97V096000: Outboard Seat Belt Replacement Seat Belt: Recalls Recall 97V096000: Outboard Seat Belt Replacement Vehicle Description: Extended cab pickup trucks equipped with 60/40 front bench seats and extended cab pickup trucks and 2-door utility vehicles equipped with manual locking recliner bucket seats. The outboard safety belt webbing on the driver's and/or passenger's seat can separate during a frontal impact. If a separation occurred and there were secondary crash events or vehicle rollover, there would be no belt restraint of the occupant and increased injuries could occur. Dealers will replace these safety belts. Owner Notification: Owner notification will begin during September 1997. Owners who take their vehicles to an authorized dealer on an agreed upon service date and do not receive the free remedy within a reasonable time should contact Chevrolet at 1-800-222-1020 or GMC at 1-800-462-8782. Also contact the National Highway Traffic Safety Administration's Auto Safety Hotline at 1-800-424-9393. 1994 CHEVROLET TRUCK S10 1994 GMC S15 1995 CHEVROLET TRUCK S10 1995 GMC S15 1996 CHEVROLET TRUCK BLAZER 1996 CHEVROLET TRUCK S10 1996 GMC JIMMY 1996 GMC S15 1997 CHEVROLET TRUCK BLAZER 1997 CHEVROLET TRUCK S10 1997 GMC JIMMY 1997 GMC S15 1997 ISUZU TRUCK HOMBRE Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Seat Belt Systems > Seat Belt > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Seat Belt: > NHTSA97V096000 > Jun > 97 > Recall 97V096000: Outboard Seat Belt Replacement Seat Belt: All Technical Service Bulletins Recall 97V096000: Outboard Seat Belt Replacement Vehicle Description: Extended cab pickup trucks equipped with 60/40 front bench seats and extended cab pickup trucks and 2-door utility vehicles equipped with manual locking recliner bucket seats. The outboard safety belt webbing on the driver's and/or passenger's seat can separate during a frontal impact. If a separation occurred and there were secondary crash events or vehicle rollover, there would be no belt restraint of the occupant and increased injuries could occur. Dealers will replace these safety belts. Owner Notification: Owner notification will begin during September 1997. Owners who take their vehicles to an authorized dealer on an agreed upon service date and do not receive the free remedy within a reasonable time should contact Chevrolet at 1-800-222-1020 or GMC at 1-800-462-8782. Also contact the National Highway Traffic Safety Administration's Auto Safety Hotline at 1-800-424-9393. 1994 CHEVROLET TRUCK S10 1994 GMC S15 1995 CHEVROLET TRUCK S10 1995 GMC S15 1996 CHEVROLET TRUCK BLAZER 1996 CHEVROLET TRUCK S10 1996 GMC JIMMY 1996 GMC S15 1997 CHEVROLET TRUCK BLAZER 1997 CHEVROLET TRUCK S10 1997 GMC JIMMY 1997 GMC S15 1997 ISUZU TRUCK HOMBRE Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Seat Belt Systems > Seat Belt Buckle > Component Information > Technical Service Bulletins > Customer Interest for Seat Belt Buckle: > 09-09-40-001A > Feb > 11 > Restraints - Seat Belt Warning Lamp On/Buckling Issues Seat Belt Buckle: Customer Interest Restraints - Seat Belt Warning Lamp On/Buckling Issues INFORMATION Bulletin No.: 09-09-40-001A Date: February 02, 2011 Subject: Seat Belt Buckle Latching Issues and/or Seat Belt Warning Lights Illuminated Models: 2011 and Prior GM Passenger Cars and Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7 X Supercede: This bulletin is being revised to add the 2011 model year. Please discard Corporate Bulletin Number 09-09-40-001 (Section 09 - Restraints). This bulletin is being published to advise dealers about seat belt buckles not operating and/or seat belt warning light illumination, as well as difficulty latching and unlatching the buckle or the buckle release button sticking. Analysis of warranty data has determined that this condition may be caused by sticky beverages being spilled onto or into the seat belt buckle assembly. Foreign debris from food, candy wrappers, paper and coins can also contribute to this condition. Important If foreign material (debris) or sticky liquids are the cause of the concern, show the customer the condition of the component (buckle assembly) and explain how it is affecting the function of the restraint system. Strongly recommend that the component be replaced. Point out the fact that this is not a manufacturing defect and is not covered by the new vehicle warranty. If the customer declines to have parts replaced, the service department management must make a notation on the service record that the lack of functionality of seating position with an inoperative buckle was fully explained to the customer. The service department management must advise the customer that having a non-functioning buckle in a seating position voids ability to use that seating position (no one should ride in the seat). Also make the customer aware that it may be against the law to ride in a vehicle without wearing a restraint system. Important Never insert anything other than the seat belt latch plate into the buckle assembly. Do not attempt to dig anything out of a buckle with a tool. Never try to wash out a buckle to remove a spilled liquid as this may damage the buckle. Use the following steps to determine the cause of the concern. 1. Inspect the buckle assembly with a light shining on the latch plate insertion area. Look for any debris or foreign objects in the buckle. 2. If any debris or foreign objects are observed, try to vacuum out the item. After the foreign material is removed, latch and unlatch the seat belt. If the system functions properly, do not replace the seat belt buckle assembly. 3. If the condition has not been corrected, inspect the buckle assembly for any sticky residue. If sticky residue is found, inform the customer that a substance was spilled on the seat belt buckle assembly causing the malfunction. The buckle assembly will need to be replaced at the customer's expense. 4. Refer to SI for seat belt component replacement. Important If foreign material (debris) or sticky liquids are the cause of the concern, show the customer the condition of the component (buckle assembly) and explain how it is affecting the function of the restraint system. Strongly recommend that the component be replaced at the customer's expense. Point out the fact that this is not a manufacturing defect and is not covered by the new vehicle warranty. If the customer declines to have parts replaced, the service department management must make a notation on the service record that the lack of functionality of seating position with an inoperative buckle was fully explained to the customer. The service department management must advise customer that having a non-functioning buckle in a seating position voids ability to use that seating position (no one should ride in the seat). Also make the customer aware that it may be against the law to ride in a vehicle without wearing a restraint system. 5. If further restraint diagnosis is required, refer to Seat Belt System Operational and Functional Checks in SI. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Seat Belt Systems > Seat Belt Buckle > Component Information > Technical Service Bulletins > Customer Interest for Seat Belt Buckle: > 09-09-40-001A > Feb > 11 > Restraints - Seat Belt Warning Lamp On/Buckling Issues > Page 10708 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Seat Belt Systems > Seat Belt Buckle > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Seat Belt Buckle: > 09-09-40-001A > Feb > 11 > Restraints - Seat Belt Warning Lamp On/Buckling Issues Seat Belt Buckle: All Technical Service Bulletins Restraints - Seat Belt Warning Lamp On/Buckling Issues INFORMATION Bulletin No.: 09-09-40-001A Date: February 02, 2011 Subject: Seat Belt Buckle Latching Issues and/or Seat Belt Warning Lights Illuminated Models: 2011 and Prior GM Passenger Cars and Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7 X Supercede: This bulletin is being revised to add the 2011 model year. Please discard Corporate Bulletin Number 09-09-40-001 (Section 09 - Restraints). This bulletin is being published to advise dealers about seat belt buckles not operating and/or seat belt warning light illumination, as well as difficulty latching and unlatching the buckle or the buckle release button sticking. Analysis of warranty data has determined that this condition may be caused by sticky beverages being spilled onto or into the seat belt buckle assembly. Foreign debris from food, candy wrappers, paper and coins can also contribute to this condition. Important If foreign material (debris) or sticky liquids are the cause of the concern, show the customer the condition of the component (buckle assembly) and explain how it is affecting the function of the restraint system. Strongly recommend that the component be replaced. Point out the fact that this is not a manufacturing defect and is not covered by the new vehicle warranty. If the customer declines to have parts replaced, the service department management must make a notation on the service record that the lack of functionality of seating position with an inoperative buckle was fully explained to the customer. The service department management must advise the customer that having a non-functioning buckle in a seating position voids ability to use that seating position (no one should ride in the seat). Also make the customer aware that it may be against the law to ride in a vehicle without wearing a restraint system. Important Never insert anything other than the seat belt latch plate into the buckle assembly. Do not attempt to dig anything out of a buckle with a tool. Never try to wash out a buckle to remove a spilled liquid as this may damage the buckle. Use the following steps to determine the cause of the concern. 1. Inspect the buckle assembly with a light shining on the latch plate insertion area. Look for any debris or foreign objects in the buckle. 2. If any debris or foreign objects are observed, try to vacuum out the item. After the foreign material is removed, latch and unlatch the seat belt. If the system functions properly, do not replace the seat belt buckle assembly. 3. If the condition has not been corrected, inspect the buckle assembly for any sticky residue. If sticky residue is found, inform the customer that a substance was spilled on the seat belt buckle assembly causing the malfunction. The buckle assembly will need to be replaced at the customer's expense. 4. Refer to SI for seat belt component replacement. Important If foreign material (debris) or sticky liquids are the cause of the concern, show the customer the condition of the component (buckle assembly) and explain how it is affecting the function of the restraint system. Strongly recommend that the component be replaced at the customer's expense. Point out the fact that this is not a manufacturing defect and is not covered by the new vehicle warranty. If the customer declines to have parts replaced, the service department management must make a notation on the service record that the lack of functionality of seating position with an inoperative buckle was fully explained to the customer. The service department management must advise customer that having a non-functioning buckle in a seating position voids ability to use that seating position (no one should ride in the seat). Also make the customer aware that it may be against the law to ride in a vehicle without wearing a restraint system. 5. If further restraint diagnosis is required, refer to Seat Belt System Operational and Functional Checks in SI. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Seat Belt Systems > Seat Belt Buckle > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Seat Belt Buckle: > 09-09-40-001A > Feb > 11 > Restraints - Seat Belt Warning Lamp On/Buckling Issues > Page 10714 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Seat Belt Systems > Seat Belt Extension > Component Information > Technical Service Bulletins > Restraints - Extender Availability For Seat Belt Seat Belt Extension: Technical Service Bulletins Restraints - Extender Availability For Seat Belt INFORMATION Bulletin No.: 99-09-40-005F Date: June 23, 2010 Subject: Seat Belt Extender Availability Models: 2011 and Prior GM Passenger Cars and Trucks (Including Saturn) 2009 and Prior HUMMER H2 2010 and Prior HUMMER H3 2005-2009 Saab 9-7X Supercede: This bulletin is being revised to add the 2009‐2011 model years and update the Warranty Information. Please discard Corporate Bulletin Number 99-09-40-005E (Section 09 Restraints). Important: DO NOT use belt extenders when securing a child restraint. The seat and shoulder belt restraint systems used in all General Motors vehicles have sufficient belt length to accommodate most drivers and passengers. Consequently, requests for belt extensions (extenders) should be minimal. Seat belt extenders are available ONLY IN BLACK for most GM passenger cars and trucks produced in recent years. They are available in two different lengths, 23 cm (9 in) and 38 cm (15 in). They are designed to be coupled with the existing belts in each vehicle. When in use, the extender makes the belt arrangement a "custom fit" and use by anyone else or in another vehicle will lessen or nullify the protection offered by the vehicle's restraint system. For this reason, it is extremely important that the correct length extender be used for the vehicle and occupant intended. Important: Do not use an extender just to make it easier to buckle the safety belt. Use an extender only when you cannot buckle the safety belt without using an extender. Parts Information For part numbers, usage and availability of extenders, see Extension Kit in Group 14.875 (cars) or Group 16.714 (trucks) of the appropriate parts catalog. Saturn retailers should refer to the appropriate model year Parts & Illustration catalog for the vehicle. U.S. Saab dealers should contact the Parts Help line. Canadian Saab dealers should fax requests to Partech Canada. Warranty Information ^ Seat belt extenders are a NO CHARGE item to all GM customers who request them for their specific vehicles. ^ Dealers should not be charging part costs since these extenders are supplied by GM to the dealers. ^ Dealers should not be charging labor costs since the extender can be customer installed. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Seat Belt Systems > Seat Sensor/Switch > Component Information > Locations Seat Belt Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Sensors and Switches - Restraint Systems > Impact Sensor > Component Information > Locations > Arming Sensor Impact Sensor: Locations Arming Sensor Inside LH Frame Rail, below Driver's Door Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Sensors and Switches - Restraint Systems > Impact Sensor > Component Information > Locations > Arming Sensor > Page 10727 Impact Sensor: Locations RH Front Discriminating Sensor RH Front outside of RH Frame Rail Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Sensors and Switches - Restraint Systems > Impact Sensor > Component Information > Locations > Arming Sensor > Page 10728 Impact Sensor: Locations LH Front Discriminating Sensor Front outside of LH Frame Rail Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Sensors and Switches - Restraint Systems > Impact Sensor > Component Information > Locations > Page 10729 I/P HARN To Arming Sensor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Sensors and Switches - Restraint Systems > Impact Sensor > Component Information > Description and Operation > Arming Sensor Impact Sensor: Description and Operation Arming Sensor The arming sensor is a protective switch located in the power side of the deployment loop. It is calibrated to close at low level speed changes. This ensures that the inflator module is connected directly to the 36 Volt Loop Reserve (VLR) output of the DERM when either of the discriminating sensors close. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Sensors and Switches - Restraint Systems > Impact Sensor > Component Information > Description and Operation > Arming Sensor > Page 10732 Impact Sensor: Description and Operation Discriminating Sensors There are two discriminating sensors in the air bag system. They are wired in parallel on the low (ground) side of the deployment loop. These sensors are calibrated to close with speed changes severe enough to warrant deployment. A diagnostic resistor is connected in parallel with the switch contacts within each of the discriminating sensors. These parallel resistors supply the ground path for the current passing through the deployment loop during normal operation. This current flow results in voltage drops across each component in the deployment loop. The DERM monitors these voltage drops to detect malfunctions. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Sensors and Switches - Restraint Systems > Impact Sensor > Component Information > Service and Repair > Arming Sensor Impact Sensor: Service and Repair Arming Sensor Prior to performing replacement procedures, disarm air bag system. Refer to, Service and Repair/ Air Bag System Disarming & Air Bag System Arming. Refer to, / Specifications/ Mechanical for torque values when installing components. All sensors and mounting bracket bolts must be carefully torqued to assure proper operation. Never power up the air bag system when any sensor is not rigidly attached to the vehicle, since the sensor could be activated when not attached, causing air bag deployment. 1. disconnect sensor electrical connector from retainer, remove Connector Position Assurance (CPA) lock from connector, then disconnect connector. 2. Remove sensor mounting bolts and sensor from vehicle. 3. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Sensors and Switches - Restraint Systems > Impact Sensor > Component Information > Service and Repair > Arming Sensor > Page 10735 Impact Sensor: Service and Repair Forward Discriminating Sensor Prior to performing replacement procedures, disarm air bag system. Refer to, Service and Repair/ Air Bag System Disarming & Air Bag System Arming. Refer to, / Specifications/ Mechanical for torque values when installing components. All sensors and mounting bracket bolts must be carefully torqued to assure proper operation. Never power up the air bag system when any sensor is not rigidly attached to the vehicle, since the sensor could be activated when not attached, causing air bag deployment. 1. Disconnect sensor electrical connector from retainer, then remove connector from Connector Position Assurance (CPA) lock and disconnect. 2. Remove sensor mounting bolts, then the sensor from vehicle. 3. Reverse procedure to install. Ensure arrow is pointed toward front of vehicle. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Sensors and Switches - Restraint Systems > Seat Occupant Sensor > Component Information > Technical Service Bulletins > Restraints - Passenger Presence System Information Seat Occupant Sensor: Technical Service Bulletins Restraints - Passenger Presence System Information INFORMATION Bulletin No.: 06-08-50-009F Date: December 23, 2010 Subject: Information on Passenger Presence Sensing System (PPS or PSS) Concerns With Custom Upholstery, Accessory Seat Heaters or Other Comfort Enhancing Devices Models: 2011 and Prior GM Passenger Cars and Trucks Equipped with Passenger Presence Sensing System Supercede: This bulletin is being revised to update the model years. Please discard Corporate Bulletin Number 06-08-50-009E (Section 08 - Body and Accessories). Concerns About Safety and Alterations to the Front Passenger Seat Important ON A GM VEHICLE EQUIPPED WITH A PASSENGER SENSING SYSTEM, USE THE SEAT COVERS AND OTHER SEAT-RELATED EQUIPMENT AS RELEASED BY GM FOR THAT VEHICLE. DO NOT ALTER THE SEAT COVERS OR SEAT-RELATED EQUIPMENT. ANY ALTERATIONS TO SEAT COVERS OR GM ACCESSORIES DEFEATS THE INTENDED DESIGN OF THE SYSTEM. GM WILL NOT BE LIABLE FOR ANY PROBLEMS CAUSED BY USE OF SUCH IMPROPER SEAT ALTERATIONS, INCLUDING ANY WARRANTY REPAIRS INCURRED. The front passenger seat in many GM vehicles is equipped with a passenger sensing system that will turn off the right front passenger's frontal airbag under certain conditions, such as when an infant or child seat is present. In some vehicles, the passenger sensing system will also turn off the right front passenger's seat mounted side impact airbag. For the system to function properly, sensors are used in the seat to detect the presence of a properly-seated occupant. The passenger sensing system may not operate properly if the original seat trim is replaced (1) by non-GM covers, upholstery or trim, or (2) by GM covers, upholstery or trim designed for a different vehicle or (3) by GM covers, upholstery or trim that has been altered by a trim shop, or (4) if any object, such as an aftermarket seat heater or a comfort enhancing pad or device is installed under the seat fabric or between the occupant and the seat fabric. Aftermarket Seat Heaters, Custom Upholstery, and Comfort Enhancing Pads or Devices Important ON A GM VEHICLE EQUIPPED WITH A PASSENGER SENSING SYSTEM, USE ONLY SEAT COVERS AND OTHER SEAT-RELATED EQUIPMENT RELEASED AS GM ACCESSORIES FOR THAT VEHICLE. DO NOT USE ANY OTHER TYPE OF SEAT COVERS OR SEAT-RELATED EQUIPMENT, OR GM ACCESSORIES RELEASED FOR OTHER VEHICLE APPLICATIONS. GM WILL NOT BE LIABLE FOR ANY PROBLEMS CAUSED BY USE OF SUCH IMPROPER SEAT ACCESSORIES, INCLUDING ANY WARRANTY REPAIRS MADE NECESSARY BY SUCH USE. Many types of aftermarket accessories are available to customers, upfitting shops, and dealers. Some of these devices sit on top of, or are Velcro(R) strapped to the seat while others such as seat heaters are installed under the seat fabric. Additionally, seat covers made of leather or other materials may have different padding thickness installed that could prevent the Passenger Sensing System from functioning properly. Never alter the vehicle seats. Never add pads or other devices to the seat cushion, as this may interfere with the operation of the Passenger Sensing System and either prevent proper deployment of the passenger airbag or prevent proper suppression of the passenger air bag. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Restraint Systems > Sensors and Switches - Restraint Systems > Seat Sensor/Switch > Component Information > Locations Seat Belt Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antenna > Antenna, Navigation > Component Information > Technical Service Bulletins > Customer Interest: > 00-08-46-003B > Feb > 05 > Instruments - GPS System Performance Degradation Antenna, Navigation: Customer Interest Instruments - GPS System Performance Degradation Info - Global Position Sensor (GPS) Performance Degradation # 00-08-46-003B - (Feb 9, 2005) Models: 1996-2005 Passenger Cars and Trucks 2002-2005 Saturn Vehicles with Navigation Systems and/or OnStar(R) This bulletin is being revised to include additional information. Please discard Corporate Bulletin Number 00-08-46-003A (Section 08 - Body and Accessories). Navigation and OnStar(R) systems require a GPS antenna in order to function properly. This antenna may be located inside the vehicle. If the GPS antenna is located inside the vehicle, performance of the system may be compromised by window tinting film. If the GPS system performance is in question and the vehicle has window tinting, a quick diagnostic check can be made by temporarily moving the GPS antenna to an external vehicle surface, such as the decklid or roof. If the GPS function of the navigation or On Star(R) system operates normally with the antenna relocated the repair would not be considered a warranty repair. The subsequent repair procedure or GPS placement would be up to the customer. Some vehicles have the GPS antenna located on the rear window shelf Objects placed on the rear window shelf such as tissue boxes, books, dolls, etc,, also have the potential to interfere with GPS performance. Warranty Information Repairs made to the vehicle navigation and/or OnStar(R) system, which are the result of window tinting, are not considered warranty repairs. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antenna > Antenna, Navigation > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Antenna, Navigation: > 00-08-46-002A > Apr > 05 > OnStar(R) - Cellular Antenna Replacement Parts Antenna, Navigation: All Technical Service Bulletins OnStar(R) - Cellular Antenna Replacement Parts Bulletin No.: 00-08-46-002A Date: April 12, 2005 INFORMATION Subject: OnStar(R) System Cellular Antenna Replacement Parts Availability Models: 1996-2005 Passenger Cars and Light Duty Trucks 2003-2005 HUMMER H2 with OnStar(R) and Glass Mounted Antennas Supercede: This bulletin is being revised to update the model years, models and parts information. Please discard Corporate Bulletin Number 00-08-46-002 (Section 08 - Body & Accessories). Replacement parts for the OnStar(R) system cellular antenna are available as follows: ^ Cellular Antenna Kit - If the antenna mast or exterior base is damaged or missing or if the antenna base has separated from the exterior glass surface. ^ Cellular Antenna Inner Coupling - If the antenna coupling on the inside of the glass requires replacement. Important: If glass replacement is required, both the Cellular Antenna Kit and the Cellular Antenna Inner Coupling are required. The kits listed contain all the necessary parts and instructions needed to properly install a new cellular antenna exterior base or interior coupling to the glass surface. To obtain maximum adhesion during installation, the instructions included in the kits must be followed carefully and exactly as written. Important: Do not attempt to reinstall the original cellular antenna exterior base or interior coupling using any type of glue, adhesive tapes, etc. Doing so may eliminate the cellular signal transfer through the glass and reduce the maximum performance of the system that includes air bag deployment notification. Important: To obtain maximum adhesion between the new cellular exterior base or interior coupling and the glass surface, the base, coupling and glass must be kept dry and above 15°C (60°F) during the installation and for the 24 hours immediately following the installation. Not keeping the vehicle dry and above the temperature listed for 24 hours may result in the new cellular antenna exterior base or interior coupling coming off. Parts Information Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antenna > Antenna, Navigation > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Antenna, Navigation: > 00-08-46-002A > Apr > 05 > OnStar(R) - Cellular Antenna Replacement Parts > Page 10758 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antenna > Antenna, Navigation > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Antenna, Navigation: > 00-08-46-003B > Feb > 05 > Instruments - GPS System Performance Degradation Antenna, Navigation: All Technical Service Bulletins Instruments - GPS System Performance Degradation Info - Global Position Sensor (GPS) Performance Degradation # 00-08-46-003B - (Feb 9, 2005) Models: 1996-2005 Passenger Cars and Trucks 2002-2005 Saturn Vehicles with Navigation Systems and/or OnStar(R) This bulletin is being revised to include additional information. Please discard Corporate Bulletin Number 00-08-46-003A (Section 08 - Body and Accessories). Navigation and OnStar(R) systems require a GPS antenna in order to function properly. This antenna may be located inside the vehicle. If the GPS antenna is located inside the vehicle, performance of the system may be compromised by window tinting film. If the GPS system performance is in question and the vehicle has window tinting, a quick diagnostic check can be made by temporarily moving the GPS antenna to an external vehicle surface, such as the decklid or roof. If the GPS function of the navigation or On Star(R) system operates normally with the antenna relocated the repair would not be considered a warranty repair. The subsequent repair procedure or GPS placement would be up to the customer. Some vehicles have the GPS antenna located on the rear window shelf Objects placed on the rear window shelf such as tissue boxes, books, dolls, etc,, also have the potential to interfere with GPS performance. Warranty Information Repairs made to the vehicle navigation and/or OnStar(R) system, which are the result of window tinting, are not considered warranty repairs. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antenna > Antenna, Navigation > Component Information > Technical Service Bulletins > All Other Service Bulletins for Antenna, Navigation: > 00-08-46-002A > Apr > 05 > OnStar(R) - Cellular Antenna Replacement Parts Antenna, Navigation: All Technical Service Bulletins OnStar(R) - Cellular Antenna Replacement Parts Bulletin No.: 00-08-46-002A Date: April 12, 2005 INFORMATION Subject: OnStar(R) System Cellular Antenna Replacement Parts Availability Models: 1996-2005 Passenger Cars and Light Duty Trucks 2003-2005 HUMMER H2 with OnStar(R) and Glass Mounted Antennas Supercede: This bulletin is being revised to update the model years, models and parts information. Please discard Corporate Bulletin Number 00-08-46-002 (Section 08 - Body & Accessories). Replacement parts for the OnStar(R) system cellular antenna are available as follows: ^ Cellular Antenna Kit - If the antenna mast or exterior base is damaged or missing or if the antenna base has separated from the exterior glass surface. ^ Cellular Antenna Inner Coupling - If the antenna coupling on the inside of the glass requires replacement. Important: If glass replacement is required, both the Cellular Antenna Kit and the Cellular Antenna Inner Coupling are required. The kits listed contain all the necessary parts and instructions needed to properly install a new cellular antenna exterior base or interior coupling to the glass surface. To obtain maximum adhesion during installation, the instructions included in the kits must be followed carefully and exactly as written. Important: Do not attempt to reinstall the original cellular antenna exterior base or interior coupling using any type of glue, adhesive tapes, etc. Doing so may eliminate the cellular signal transfer through the glass and reduce the maximum performance of the system that includes air bag deployment notification. Important: To obtain maximum adhesion between the new cellular exterior base or interior coupling and the glass surface, the base, coupling and glass must be kept dry and above 15°C (60°F) during the installation and for the 24 hours immediately following the installation. Not keeping the vehicle dry and above the temperature listed for 24 hours may result in the new cellular antenna exterior base or interior coupling coming off. Parts Information Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antenna > Antenna, Navigation > Component Information > Technical Service Bulletins > All Other Service Bulletins for Antenna, Navigation: > 00-08-46-002A > Apr > 05 > OnStar(R) - Cellular Antenna Replacement Parts > Page 10768 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antenna > Antenna, Phone > Component Information > Technical Service Bulletins > OnStar(R) - Cellular Antenna Replacement Parts Antenna, Phone: Technical Service Bulletins OnStar(R) - Cellular Antenna Replacement Parts Bulletin No.: 00-08-46-002A Date: April 12, 2005 INFORMATION Subject: OnStar(R) System Cellular Antenna Replacement Parts Availability Models: 1996-2005 Passenger Cars and Light Duty Trucks 2003-2005 HUMMER H2 with OnStar(R) and Glass Mounted Antennas Supercede: This bulletin is being revised to update the model years, models and parts information. Please discard Corporate Bulletin Number 00-08-46-002 (Section 08 - Body & Accessories). Replacement parts for the OnStar(R) system cellular antenna are available as follows: ^ Cellular Antenna Kit - If the antenna mast or exterior base is damaged or missing or if the antenna base has separated from the exterior glass surface. ^ Cellular Antenna Inner Coupling - If the antenna coupling on the inside of the glass requires replacement. Important: If glass replacement is required, both the Cellular Antenna Kit and the Cellular Antenna Inner Coupling are required. The kits listed contain all the necessary parts and instructions needed to properly install a new cellular antenna exterior base or interior coupling to the glass surface. To obtain maximum adhesion during installation, the instructions included in the kits must be followed carefully and exactly as written. Important: Do not attempt to reinstall the original cellular antenna exterior base or interior coupling using any type of glue, adhesive tapes, etc. Doing so may eliminate the cellular signal transfer through the glass and reduce the maximum performance of the system that includes air bag deployment notification. Important: To obtain maximum adhesion between the new cellular exterior base or interior coupling and the glass surface, the base, coupling and glass must be kept dry and above 15°C (60°F) during the installation and for the 24 hours immediately following the installation. Not keeping the vehicle dry and above the temperature listed for 24 hours may result in the new cellular antenna exterior base or interior coupling coming off. Parts Information Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antenna > Antenna, Phone > Component Information > Technical Service Bulletins > OnStar(R) - Cellular Antenna Replacement Parts > Page 10773 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antenna > Global Positioning System Antenna > Component Information > Technical Service Bulletins > OnStar(R) - Cellular Antenna Replacement Parts Global Positioning System Antenna: Technical Service Bulletins OnStar(R) - Cellular Antenna Replacement Parts Bulletin No.: 00-08-46-002A Date: April 12, 2005 INFORMATION Subject: OnStar(R) System Cellular Antenna Replacement Parts Availability Models: 1996-2005 Passenger Cars and Light Duty Trucks 2003-2005 HUMMER H2 with OnStar(R) and Glass Mounted Antennas Supercede: This bulletin is being revised to update the model years, models and parts information. Please discard Corporate Bulletin Number 00-08-46-002 (Section 08 - Body & Accessories). Replacement parts for the OnStar(R) system cellular antenna are available as follows: ^ Cellular Antenna Kit - If the antenna mast or exterior base is damaged or missing or if the antenna base has separated from the exterior glass surface. ^ Cellular Antenna Inner Coupling - If the antenna coupling on the inside of the glass requires replacement. Important: If glass replacement is required, both the Cellular Antenna Kit and the Cellular Antenna Inner Coupling are required. The kits listed contain all the necessary parts and instructions needed to properly install a new cellular antenna exterior base or interior coupling to the glass surface. To obtain maximum adhesion during installation, the instructions included in the kits must be followed carefully and exactly as written. Important: Do not attempt to reinstall the original cellular antenna exterior base or interior coupling using any type of glue, adhesive tapes, etc. Doing so may eliminate the cellular signal transfer through the glass and reduce the maximum performance of the system that includes air bag deployment notification. Important: To obtain maximum adhesion between the new cellular exterior base or interior coupling and the glass surface, the base, coupling and glass must be kept dry and above 15°C (60°F) during the installation and for the 24 hours immediately following the installation. Not keeping the vehicle dry and above the temperature listed for 24 hours may result in the new cellular antenna exterior base or interior coupling coming off. Parts Information Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antenna > Global Positioning System Antenna > Component Information > Technical Service Bulletins > OnStar(R) - Cellular Antenna Replacement Parts > Page 10778 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antitheft and Alarm Systems > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Receiver > Component Information > Locations Keyless Entry Receiver: Locations Under center portion of instrument panel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antitheft and Alarm Systems > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Transmitter > Component Information > Technical Service Bulletins > Customer Interest: > 66-90-03 > Jun > 97 > Keyless Entry - Unintended Release of Rear Hatch Keyless Entry Transmitter: Customer Interest Keyless Entry - Unintended Release of Rear Hatch File In Section: 9 - Accessories Bulletin No.: 66-90-03 Date: June, 1997 Subject: Unintended Release of Rear Hatch (Replace Transmitter Cover) Models: 1994-96 Chevrolet and GMC C/K, S/T, M/L, G Models 1994 Oldsmobile Bravada 1996 Oldsmobile Bravada Condition An owner may report that the Rear Hatch Releases without their being aware of it. Cause The Keyless Entry Transmitter Button is unintentionally bumped activating the hatch release. Correction Replace the Keyless Entry Transmitter Cover. The revised cover has a deeper recess around the release button making it less prone to inadvertent bumping. Parts Information P/N Description Qty 15740707 Bezel, Transmitter Cover 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time R4490 Control Assembly 0.3 hr Cover - Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antitheft and Alarm Systems > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Transmitter > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Keyless Entry Transmitter: > 83-90-12 > Aug > 98 > Tools - Keyless Entry Transmitter Tester Keyless Entry Transmitter: All Technical Service Bulletins Tools - Keyless Entry Transmitter Tester File In Section: 9 - Accessories Bulletin No.: 83-90-12 Date: August, 1998 INFORMATION Subject: Essential Tool J 43241 Remote Keyless Entry and Passive Keyless Entry Transmitter Tester Models: 1990-99 Passenger Cars and Trucks with Remote Keyless Entry or Passive Keyless Entry Systems A new essential tool, J 43241 Remote Keyless Entry Transmitter Tester, has been sent to all GM Dealers. This tester can be used on all RKE and PKE systems, on past as well as current models. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antitheft and Alarm Systems > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Transmitter > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Keyless Entry Transmitter: > 83-90-12 > Aug > 98 > Tools - Keyless Entry Transmitter Tester > Page 10797 Important: Before using the tester and the diagnostic chart, the following two steps must be performed. 1. Verify that the keyless entry transmitter is the correct model for the vehicle remote system. An incorrect model transmitter may pass this test, but may not activate the vehicle remote system. The correct transmitter can usually be identified by part number. 2. Ensure that the transmitter is synchronized with the vehicle (if applicable). Refer to Transmitter Synchronization in the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antitheft and Alarm Systems > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Transmitter > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Keyless Entry Transmitter: > 66-90-03 > Jun > 97 > Keyless Entry - Unintended Release of Rear Hatch Keyless Entry Transmitter: All Technical Service Bulletins Keyless Entry - Unintended Release of Rear Hatch File In Section: 9 - Accessories Bulletin No.: 66-90-03 Date: June, 1997 Subject: Unintended Release of Rear Hatch (Replace Transmitter Cover) Models: 1994-96 Chevrolet and GMC C/K, S/T, M/L, G Models 1994 Oldsmobile Bravada 1996 Oldsmobile Bravada Condition An owner may report that the Rear Hatch Releases without their being aware of it. Cause The Keyless Entry Transmitter Button is unintentionally bumped activating the hatch release. Correction Replace the Keyless Entry Transmitter Cover. The revised cover has a deeper recess around the release button making it less prone to inadvertent bumping. Parts Information P/N Description Qty 15740707 Bezel, Transmitter Cover 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time R4490 Control Assembly 0.3 hr Cover - Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antitheft and Alarm Systems > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Transmitter > Component Information > Technical Service Bulletins > All Other Service Bulletins for Keyless Entry Transmitter: > 83-90-12 > Aug > 98 > Tools - Keyless Entry Transmitter Tester Keyless Entry Transmitter: All Technical Service Bulletins Tools - Keyless Entry Transmitter Tester File In Section: 9 - Accessories Bulletin No.: 83-90-12 Date: August, 1998 INFORMATION Subject: Essential Tool J 43241 Remote Keyless Entry and Passive Keyless Entry Transmitter Tester Models: 1990-99 Passenger Cars and Trucks with Remote Keyless Entry or Passive Keyless Entry Systems A new essential tool, J 43241 Remote Keyless Entry Transmitter Tester, has been sent to all GM Dealers. This tester can be used on all RKE and PKE systems, on past as well as current models. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antitheft and Alarm Systems > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Transmitter > Component Information > Technical Service Bulletins > All Other Service Bulletins for Keyless Entry Transmitter: > 83-90-12 > Aug > 98 > Tools - Keyless Entry Transmitter Tester > Page 10807 Important: Before using the tester and the diagnostic chart, the following two steps must be performed. 1. Verify that the keyless entry transmitter is the correct model for the vehicle remote system. An incorrect model transmitter may pass this test, but may not activate the vehicle remote system. The correct transmitter can usually be identified by part number. 2. Ensure that the transmitter is synchronized with the vehicle (if applicable). Refer to Transmitter Synchronization in the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antitheft and Alarm Systems > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Transmitter > Component Information > Locations > Component Locations Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antitheft and Alarm Systems > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Transmitter > Component Information > Locations > Component Locations > Page 10810 Data Link Connector (DLC) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Antitheft and Alarm Systems > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Transmitter > Component Information > Locations > Page 10811 Keyless Entry Transmitter: Service and Repair Data Link Connector (DLC) 1. Ground pin G of the Data Link Connector (DLC). ^ Receiver will respond by locking and unlocking doors within 2 seconds. 2. Press any button of the first transmitter to be programmed. 3. The control module will respond by locking/unlocking doors and activating rear window release. 4. Press any button of the second transmitter to be programmed (if used). 5. The control module will respond by locking/unlocking doors and activating the rear window release. 6. Remove the ground applied to the reprogramming connector. 7. Transmitter operation is verified by locking and unlocking the doors and activating the rear window release. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Cellular Phone > Component Information > Technical Service Bulletins > OnStar(R)/Cell Phone - Integration Cellular Phone: Technical Service Bulletins OnStar(R)/Cell Phone - Integration Bulletin No.: 01-08-46-004A Date: March 08, 2005 INFORMATION Subject: Vehicle Integration of Cellular Phones and Normal Operating Characteristics Models: 2002 and Prior Passenger Cars and Trucks Supercede: This bulletin is being issued to cancel Corporate Bulletin Number 01-08-46-004. Please discard all copies of Corporate Bulletin Number 01-08-46-004 (Section 08 - Body and Accessories). This bulletin effectively cancels Corporate Bulletin Number 01-08-46-004. OnStar(R) no longer offers cellular phones as part of the OnStar(R) system. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Cellular Phone > Component Information > Technical Service Bulletins > OnStar(R)/Cell Phone - Integration > Page 10816 Technical Service Bulletin # 83-96-05 Date: 980701 Radio Telephone/Mobile Radio - Install/Troubleshooting File In Section: 9 - Accessories Bulletin No.: 83-96-05 Date: July, 1998 Subject: Radio Telephone/Mobile Radio (Transceiver) Installation and Troubleshooting Guidelines Models: 1990-99 Passenger Cars and Trucks This bulletin cancels and supercedes bulletin 34-92-12. Please discard Corporate Bulletin Number 34-92-12 (Section 9 - Accessories). The following information is being provided to assist in the installation and troubleshooting of Radio Telephone/Mobile Radios. Certain radio telephones or land mobile radios (also known as Radio Transceivers), or the way in which they are installed, may adversely affect various vehicle operations such as engine performance, driver information, entertainment and electrical systems. Expenses incurred to protect the vehicle systems from any adverse effect of any such installation are NOT the responsibility of General Motors Corporation. The following are general guidelines for installing a radio transceiver in General Motors vehicles. These guidelines are intended to supplement, but not to be used in place of, detailed instructions which are the sole responsibility of the manufacturer of the involved radio transceiver. Although this document refers to passenger vehicles, the same general guidelines apply to trucks. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Cellular Phone > Component Information > Technical Service Bulletins > OnStar(R)/Cell Phone - Integration > Page 10817 EMC TROUBLESHOOTING CHART 1. Transceiver Location Refer to the attached figures during installation. 1. Transceiver Location Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Cellular Phone > Component Information > Technical Service Bulletins > OnStar(R)/Cell Phone - Integration > Page 10818 a. One piece transceivers should be mounted under the dash, or on the transmission hump where they will not interfere with vehicle controls or passenger movement (See Figure 1 - One Piece Transceiver Installation). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Cellular Phone > Component Information > Technical Service Bulletins > OnStar(R)/Cell Phone - Integration > Page 10819 b. Locate the transceiver for remote radios on the driver's side of trunk as near to the vehicle body side as possible (See Figure 2 - Trunk Mount Transceiver Installation). Caution: To avoid possible serious injury, do not mount any transceivers, microphones, speakers, or any other item In the deployment path of a Supplemental Inflatable Restraint (SIR) or "Air Bag". 2. Antenna Installation a. Each vehicle model reacts to radio frequency energy differently. It is suggested that a magnetic-mount antenna be used to check the proposed antenna location for unwanted effects on the vehicle. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Cellular Phone > Component Information > Technical Service Bulletins > OnStar(R)/Cell Phone - Integration > Page 10820 Antenna location is a major factor in these effects. b. The antenna should be a permanent-mount type, located in the center of the roof or center of the rear deck lid. If a magnet-mount antenna is used, care should be taken to mount the antenna in the same location as a permanent-mount type. If a disguise-mount antenna is used, great care should be taken to shield (using copper tape, etc.) any tuning network from vehicle electronics and wiring, or mount the tuning network in an area completely clear (6 inches or 15 cm away) of vehicle electronics and wiring. c. Standard metal mount antennas may be mounted on a vehicle with non-metallic body panels by two methods: 1. Mount the antenna near a metal frame section and bond the antenna mount to the frame with a short metal strap, which will provide the ground plane connection. 2. Some antenna manufacturers may offer "Ground Plane Kits" that consist of self adhesive metal foil that may be attached to the body panel to provide a ground plane connection. d. Glass Mount Antennas Glass mounted antennas should be kept as high as possible in the center of the rear window or windshield, between rear window defrost "grid lines", if present. Some vehicles use glass that contains a thin metallic layer for defrosting, or to control solar gain. GLASS MOUNT ANTENNAS WILL NOT FUNCTION WHEN MOUNTED ON THIS TYPE OF GLASS. 3. Antenna Cable Routing a. Always use high quality coax cable (95% shield coverage minimum), located away (at least 6 inches or 15 cm) from ECM's, PCM's and other electronic modules. b. Care should be taken to maintain as great a distance as possible between any vehicle wiring and coax cable. 4. Antenna Tuning It is important that the antenna be tuned properly and that reflected power be kept to less than 10% (VSWR less than 2:1) at all operating frequencies. Important: High VSWR has been shown to contribute/cause interference problems with vehicle systems. 5. Radio Wiring and Power Lead Connection Locations a. Methods to connect radio power on General Motors vehicles is dependent on the vehicle model (See Figure 1 - One Piece Transceiver Installation or Figure 2 - Trunk Mount Transceiver Installation as needed). Do not connect the negative power lead to any under-dash termination point. One of the following four methods is suggested: 1. Connect the positive and negative power leads directly to the battery terminals. GM approved methods of connecting auxiliary wiring include the adapter package illustrated in Figure 4 - Power Cable Battery Connections. Important: It is recommended that a fuse be placed in the transceiver negative power lead. This is to prevent possible transceiver damage in the event the battery to engine block ground lead is inadvertently disconnected. 2. Connect the positive lead to the auxiliary power terminal (usually identified by a red plastic cover in the underhood area). Connect the negative lead directly to the negative battery terminal. Important: See above important statement regarding fusing the negative power lead. 3. Connect the positive lead to the auxiliary power terminal (usually identified by a red plastic cover in the underhood area). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Cellular Phone > Component Information > Technical Service Bulletins > OnStar(R)/Cell Phone - Integration > Page 10821 Connect the negative lead to the battery body connection point (usually identified by a short # 10 AWG or larger wire running from the negative battery terminal to the body of the vehicle). Important: See above important statement regarding fusing the negative power lead. 4. Connect the positive and negative leads to the Special Equipment Option (SEO) wiring provided for this purpose (if vehicle has this option). b. For One Piece Transceivers (See Figure 1 - One Piece Transceiver Installation) When ignition switch control is desired, and no SEO wiring exists, a 12 volt power contactor must be installed in the transceiver positive power lead (See Figure 3 - Power Contactor Wiring). The contactor (supplied by the installer) should be located near a proper 12 volt feed source. One lead of the contactor coil should be connected through an appropriate in-line fuse to an available accessory circuit or ignition circuit not Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Cellular Phone > Component Information > Technical Service Bulletins > OnStar(R)/Cell Phone - Integration > Page 10822 powered during engine cranking. The return lead of the contactor coil must return to a proper fused negative point. c. Handset or Control Units 1. Any negative power lead from a handset or control unit must return to a properly fused negative connection point. 2. It is preferable that the positive power lead for a handset, or control unit, be connected directly to a properly fused positive power feed point. If ignition switch control is desired, the handset or control unit positive power lead may be connected through an appropriate in-line fuse to an available accessory circuit (or ignition circuit not powered during engine cranking). 3. It is recommended that the handset or control unit positive and negative power leads be appropriately fused separately from the transceiver positive and negative power leads. d. Multiple Transceivers or Receivers If multiple transceivers or receivers are to be installed in the vehicle, power leads to the trunk or under the dash should be connected to covered, insulated terminal strips. All transceivers or receivers may then have their power leads connected to the insulated terminal strips. This makes a neater installation and reduces the number of wires running to the vehicle underhood area. Both positive and negative power leads should be fused. 6. Radio Wire Routing (See Figure 1 - One Piece Transceiver Installation, or Figure 2 - Trunk Mount Transceiver Installation as needed). a. The power leads (fused) should be brought through a grommeted hole (provided by the installer) in the front cowl. For trunk mounted transceivers, the cables should continue on along the driver's side door sills, under the rear seat and into the trunk through a rear bulkhead. Maintain as great a distance as possible between radio power leads and vehicle electronic modules and wiring. b. If the radio power leads need to cross the engine compartment, they should cross between the engine and the front of the vehicle. Troubleshooting Refer to the Troubleshooting Chart as needed. 1. Most vehicle-radio interaction is avoided by following the Installation Guidelines outlined above. 2. If vehicle-radio interaction is evident following radio installation, the source of the problem should be determined prior to further vehicle/radio operation. The EMC Troubleshooting Chart should help in determining the source of the vehicle-radio interaction. Parts Information P/N Description 1846855 Adapter Kit, Side Terminal Battery (consisting of Adapter Terminal, Terminal Cover, Wire Connector, Insulation Boot) 12004188 Bolt, Battery Cable Terminal 12354951 Spacer, Battery Cable Terminal Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Emergency Contact Module > Component Information > Technical Service Bulletins > OnStar(R) - Analog Only Systems Information Emergency Contact Module: Technical Service Bulletins OnStar(R) - Analog Only Systems Information INFORMATION Bulletin No.: 06-08-64-007A Date: September 22, 2008 Subject: Information on OnStar(R) Analog-Only Systems Models Supercede: This bulletin is being revised to update the models affected list above. Please discard Corporate Bulletin Number 06-08-46-007 (Section 08 - Body & Accessories). All vehicles equipped with OnStar(R) listed in this bulletin were built with Analog-Only OnStar(R) Hardware. OnStar(R) equipped vehicles with analog-only equipment were designed to operate only on the analog wireless network and cannot be upgraded for digital network compatibility. Vehicles with this equipment will no longer be able to receive OnStar(R) services beginning January 1, 2008. At that time, service will be available only through Dual-Mode (Analog / Digital) equipment. Analog-Only vehicles cannot be upgraded to digital equipment. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Emergency Contact Module > Component Information > Technical Service Bulletins > OnStar(R) - Analog Only Systems Information > Page 10827 Emergency Contact Module: Technical Service Bulletins OnStar(R) - Aftermarket Device Interference Information INFORMATION Bulletin No.: 08-08-46-004 Date: August 14, 2008 Subject: Information on Aftermarket Device Interference with OnStar(R) Diagnostic Services Models: 2009 and Prior GM Passenger Car and Truck (including Saturn) 2009 and Prior HUMMER H2, H3 Models 2009 and Prior Saab 9-7X with OnStar(R) (RPO UE1) This bulletin is being issued to provide dealer service personnel with information regarding aftermarket devices connected to the Diagnostic Link Connector (DLC) and the impact to OnStar(R) diagnostic probes and Vehicle Diagnostic e-mails. Certain aftermarket devices, when connected to the Diagnostic Link Connector, such as, but not limited to, Scan Tools, Trip Computers, Fuel Economy Analyzers and Insurance Tracking Devices, interfere with OnStar's ability to perform a diagnostic probe when requested (via a blue button call) by a subscriber. These devices also prohibit the ability to gather diagnostic and tire pressure data for a subscriber's scheduled OnStar(R) Vehicle Diagnostic (OVD) e-mail. These aftermarket devices utilize the Vehicles serial data bus to perform data requests and/or information gathering. When these devices are requesting data, OnStar(R) is designed not to interfere with any data request being made by these devices as required by OBD II regulations. The OnStar(R) advisor is unable to definitively detect the presence of these devices and will only be able to inform the caller or requester of the unsuccessful or incomplete probe and may in some cases refer the subscriber/requester to take the vehicle to a dealer for diagnosis of the concern. When performing a diagnostic check for an unsuccessful or incomplete OnStar(R) diagnostic probe, or for concerns regarding completeness of the OnStar(R) Vehicle Diagnostic (OVD) e-mail, verify that an aftermarket device was not present at the time of the requested probe. Regarding the OVD e-mail, if an aftermarket device is interfering (including a Scan Tool of any type), the e-mail will consistently display a "yellow" indication in diagnostics section for all vehicle systems except the OnStar(R) System and Tire Pressure data (not available on all vehicles) will not be displayed (i.e. section is collapsed). Successful diagnostic probes and complete OVD e-mails will resume following the removal or disconnecting of the off-board device. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Emergency Contact Module > Component Information > Technical Service Bulletins > OnStar(R) - Analog Only Systems Information > Page 10828 Emergency Contact Module: Technical Service Bulletins OnStar - Analog-Only Systems Information Bulletin No.: 06-08-46-007 Date: December 13, 2006 INFORMATION Subject: Information on OnStar(R) Analog-Only Systems Models: 1996-2001 GM Passenger Cars and Trucks Plus: 2002 Buick LeSabre, Rendezvous 2002-2003 Buick Century, Regal 2002-2005 Buick Park Avenue 2002 Cadillac Eldorado, Escalade Models 2002 Chevrolet Avalanche, Silverado, Suburban, Tahoe, Venture 2002 GMC Denali, Denali XL, Jimmy, Sierra, Yukon, Yukon XL 2002 Oldsmobile Intrigue, Silhouette 2002-2003 Oldsmobile Aurora 2002 Pontiac Aztek, Bonneville, Montana 2002-2003 Pontiac Grand Prix with OnStar(R) (RPO UE1) All vehicles equipped with OnStar(R) listed in this bulletin were built with Analog-Only OnStar(R) Hardware. OnStar(R) equipped vehicles with analog-only equipment were designed to operate only on the analog wireless network and cannot be upgraded for digital network compatibility. Vehicles with this equipment will no longer be able to receive OnStar(R) services beginning January 1, 2008. At that time, service will be available only through Dual-Mode (Analog/Digital) equipment. Analog-Only vehicles cannot be upgraded to digital equipment. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Global Positioning System > Global Positioning System Antenna > Component Information > Technical Service Bulletins > OnStar(R) - Cellular Antenna Replacement Parts Global Positioning System Antenna: Technical Service Bulletins OnStar(R) - Cellular Antenna Replacement Parts Bulletin No.: 00-08-46-002A Date: April 12, 2005 INFORMATION Subject: OnStar(R) System Cellular Antenna Replacement Parts Availability Models: 1996-2005 Passenger Cars and Light Duty Trucks 2003-2005 HUMMER H2 with OnStar(R) and Glass Mounted Antennas Supercede: This bulletin is being revised to update the model years, models and parts information. Please discard Corporate Bulletin Number 00-08-46-002 (Section 08 - Body & Accessories). Replacement parts for the OnStar(R) system cellular antenna are available as follows: ^ Cellular Antenna Kit - If the antenna mast or exterior base is damaged or missing or if the antenna base has separated from the exterior glass surface. ^ Cellular Antenna Inner Coupling - If the antenna coupling on the inside of the glass requires replacement. Important: If glass replacement is required, both the Cellular Antenna Kit and the Cellular Antenna Inner Coupling are required. The kits listed contain all the necessary parts and instructions needed to properly install a new cellular antenna exterior base or interior coupling to the glass surface. To obtain maximum adhesion during installation, the instructions included in the kits must be followed carefully and exactly as written. Important: Do not attempt to reinstall the original cellular antenna exterior base or interior coupling using any type of glue, adhesive tapes, etc. Doing so may eliminate the cellular signal transfer through the glass and reduce the maximum performance of the system that includes air bag deployment notification. Important: To obtain maximum adhesion between the new cellular exterior base or interior coupling and the glass surface, the base, coupling and glass must be kept dry and above 15°C (60°F) during the installation and for the 24 hours immediately following the installation. Not keeping the vehicle dry and above the temperature listed for 24 hours may result in the new cellular antenna exterior base or interior coupling coming off. Parts Information Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Global Positioning System > Global Positioning System Antenna > Component Information > Technical Service Bulletins > OnStar(R) - Cellular Antenna Replacement Parts > Page 10834 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Navigation System > Component Information > Technical Service Bulletins > OnStar(R) - Analog Only Systems Information Navigation System: Technical Service Bulletins OnStar(R) - Analog Only Systems Information INFORMATION Bulletin No.: 06-08-64-007A Date: September 22, 2008 Subject: Information on OnStar(R) Analog-Only Systems Models Supercede: This bulletin is being revised to update the models affected list above. Please discard Corporate Bulletin Number 06-08-46-007 (Section 08 - Body & Accessories). All vehicles equipped with OnStar(R) listed in this bulletin were built with Analog-Only OnStar(R) Hardware. OnStar(R) equipped vehicles with analog-only equipment were designed to operate only on the analog wireless network and cannot be upgraded for digital network compatibility. Vehicles with this equipment will no longer be able to receive OnStar(R) services beginning January 1, 2008. At that time, service will be available only through Dual-Mode (Analog / Digital) equipment. Analog-Only vehicles cannot be upgraded to digital equipment. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Navigation System > Component Information > Technical Service Bulletins > OnStar(R) - Analog Only Systems Information > Page 10839 Navigation System: Technical Service Bulletins OnStar(R) - Aftermarket Device Interference Information INFORMATION Bulletin No.: 08-08-46-004 Date: August 14, 2008 Subject: Information on Aftermarket Device Interference with OnStar(R) Diagnostic Services Models: 2009 and Prior GM Passenger Car and Truck (including Saturn) 2009 and Prior HUMMER H2, H3 Models 2009 and Prior Saab 9-7X with OnStar(R) (RPO UE1) This bulletin is being issued to provide dealer service personnel with information regarding aftermarket devices connected to the Diagnostic Link Connector (DLC) and the impact to OnStar(R) diagnostic probes and Vehicle Diagnostic e-mails. Certain aftermarket devices, when connected to the Diagnostic Link Connector, such as, but not limited to, Scan Tools, Trip Computers, Fuel Economy Analyzers and Insurance Tracking Devices, interfere with OnStar's ability to perform a diagnostic probe when requested (via a blue button call) by a subscriber. These devices also prohibit the ability to gather diagnostic and tire pressure data for a subscriber's scheduled OnStar(R) Vehicle Diagnostic (OVD) e-mail. These aftermarket devices utilize the Vehicles serial data bus to perform data requests and/or information gathering. When these devices are requesting data, OnStar(R) is designed not to interfere with any data request being made by these devices as required by OBD II regulations. The OnStar(R) advisor is unable to definitively detect the presence of these devices and will only be able to inform the caller or requester of the unsuccessful or incomplete probe and may in some cases refer the subscriber/requester to take the vehicle to a dealer for diagnosis of the concern. When performing a diagnostic check for an unsuccessful or incomplete OnStar(R) diagnostic probe, or for concerns regarding completeness of the OnStar(R) Vehicle Diagnostic (OVD) e-mail, verify that an aftermarket device was not present at the time of the requested probe. Regarding the OVD e-mail, if an aftermarket device is interfering (including a Scan Tool of any type), the e-mail will consistently display a "yellow" indication in diagnostics section for all vehicle systems except the OnStar(R) System and Tire Pressure data (not available on all vehicles) will not be displayed (i.e. section is collapsed). Successful diagnostic probes and complete OVD e-mails will resume following the removal or disconnecting of the off-board device. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Navigation System > Component Information > Technical Service Bulletins > OnStar(R) - Analog Only Systems Information > Page 10840 Navigation System: Technical Service Bulletins Navigation System - Replacement Navigation Discs Bulletin No.: 07-08-44-007 Date: April 17, 2007 INFORMATION Subject: Information on Obtaining Replacement Navigation Discs When Radios are Exchanged Order Replacement Navigation Disc Through Navigation Disc Center Models: 2007 and Prior GM Passenger Cars and Trucks (Including Saturn) 2007 and Prior HUMMER H2, H3 2007 and Prior Saab 9-7X with a Navigation Radio Attention: The purpose of this bulletin is to inform dealership personnel of a new procedure for obtaining a replacement navigation disc for radios that are sent to an ESC for exchange. This bulletin applies to U.S. and Canadian dealers only and is not intended for use by export dealers. When a navigation radio warranty exchange is performed, the customer must have a navigation disc to operate the new radio. If the customer's navigation disc was damaged or is stuck in the failed radio, the customer would have to wait for an excessive period of time for the disc to be returned or replaced. The Electronic Service Centers (ESC) are not authorized to remove stuck navigation discs from cores, as the cores must be returned to the supplier for analysis prior to any disassembly. The time it would take for the supplier to return the navigation disc would significantly delay the completion of the repair at the dealership. If the customer's navigation disc is damaged or cannot be removed from the radio, the dealership is to obtain an exchange radio through an ESC and a new navigation disc through the GM Navigation Disc Center. Both items can be shipped overnight to the dealership upon request. GM Navigation Disc Center Contact Information Via the web through gmnavdisc.com The GM Navigation Disc Center is also the center of expertise for navigation system questions. Warranty Information Include the part number and cost of the new navigation disc on the warranty claim for the navigation radio exchange. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Amplifier, Sound System > Component Information > Locations > Power Amplifier Amplifier: Locations Power Amplifier Under Driver's Seat Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Amplifier, Sound System > Component Information > Locations > Power Amplifier > Page 10846 Power Door Lock Relay Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Amplifier, Sound System > Component Information > Locations > Page 10847 Amplifier: Diagrams Power Amplifier Power Amplifier Relay Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Technical Service Bulletins > Customer Interest for Compact Disc Player (CD): > 649601 > Jan > 97 > Compact Disc Players - CD Changer Loading Procedures Compact Disc Player (CD): Customer Interest Compact Disc Players - CD Changer Loading Procedures File In Section: 9 - Accessories Bulletin No.: 64-96-01 Date: January, 1997 INFORMATION Subject: Compact Disc Players - Procedures for Correct Use and Maintenance Models: 1997 and Prior Passenger Cars and Trucks CD Changer Loading Procedures Because of differences in CD changer loading procedures, some confusion exists regarding this issue. Although correct loading procedures are included with each changer's Owner's Manual, often this information is not available to the dealer service personnel. Verify proper loading when evaluating customer concerns of "CD inoperative". Delco Electronics Product Type Loading Procedure Radio w/intergral CD label side up 6 disc changer (LLAI) label side up 10 disc changer (FMI) label side up 12 disc changer (LLAI) label side down Important: Failure to load magazine/player correctly will disable the operation. Important: Only the 12 disc changer is to be loaded with the label side down. CD Cleaners Avoid use of commercially available CD cleaners. The use of CD cleaners is not recommended and can damage the player's CD mechanism. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Compact Disc Player (CD): > 649601 > Jan > 97 > Compact Disc Players - CD Changer Loading Procedures Compact Disc Player (CD): All Technical Service Bulletins Compact Disc Players - CD Changer Loading Procedures File In Section: 9 - Accessories Bulletin No.: 64-96-01 Date: January, 1997 INFORMATION Subject: Compact Disc Players - Procedures for Correct Use and Maintenance Models: 1997 and Prior Passenger Cars and Trucks CD Changer Loading Procedures Because of differences in CD changer loading procedures, some confusion exists regarding this issue. Although correct loading procedures are included with each changer's Owner's Manual, often this information is not available to the dealer service personnel. Verify proper loading when evaluating customer concerns of "CD inoperative". Delco Electronics Product Type Loading Procedure Radio w/intergral CD label side up 6 disc changer (LLAI) label side up 10 disc changer (FMI) label side up 12 disc changer (LLAI) label side down Important: Failure to load magazine/player correctly will disable the operation. Important: Only the 12 disc changer is to be loaded with the label side down. CD Cleaners Avoid use of commercially available CD cleaners. The use of CD cleaners is not recommended and can damage the player's CD mechanism. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Technical Service Bulletins > Page 10861 Cargo Lamp Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions Compact Disc Player (CD): Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10864 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10865 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10866 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10867 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10868 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10869 Compact Disc Player (CD): Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10870 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10871 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10872 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10873 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10874 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10875 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10876 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10877 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10878 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10879 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10880 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10881 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10882 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10883 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10884 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10885 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10886 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10887 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10888 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10889 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10890 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10891 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10892 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10893 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10894 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Compact Disc Player (CD) > Component Information > Diagrams > Diagram Information and Instructions > Page 10895 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > Customer Interest: > 669601 > Aug > 96 > Radios - Revised With Integral Cooling Fan Operation Radio/Stereo: Customer Interest Radios - Revised With Integral Cooling Fan Operation File in Section: 9 - Accessories Bulletin No.: 66-96-01 Date: August, 1996 INFORMATION Subject: New Radios with Integral Cooling Fan Models: 1996 Chevrolet and GMC C/K Models Effective May 6, 1996, Delco began shipping to assembly plants, revised radios with an integral cooling fan. Some customers may ask about the slight sound created when the fan is operating. The purpose of the fan is to maintain an optimal operating temperature in the unit only while the cassette or compact disc player is operating. Because the fan runs only when a cassette or compact disc is being played, it is recommended that cassette or compact disc be removed when not in use. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Radio/Stereo: > 01-08-44-006A > Jun > 01 > Audio System - Clearing `CLN' Message From Display Radio/Stereo: All Technical Service Bulletins Audio System - Clearing `CLN' Message From Display File In Section: 08 - Body and Accessories Bulletin No.: 01-08-44-006A Date: June, 2001 INFORMATION Subject: Cleaning the Cassette Tape Player and Clearing the CLN Message from the Radio Display Models: 1996-2002 Chevrolet and GMC Truck Models With Remote Cassette Tape Player (RP0 UP0) This bulletin is being revised to include additional model years and models, parts information, and to provide a procedure for cleaning the cassette tape player and resetting the CLN indicator on the radio display. Please discard Corporate Bulletin Number 01-08-44-006 (Section 08 - Body and Accessories). When the CLN message appears on the audio system, it indicates that the cassette tape player requires cleaning. Customers should follow the listed instructions. The recommended cleaning method for the remote cassette player is to use a scrubbing action, non-abrasive cleaning cassette, GM P/N 12344789. The cleaning cassette scrubs the tape head as the hubs of the cleaner cassette turn. Use the following procedure to clean the remote cassette player and reset the CLN indicator on the radio. 1. With the radio ON, insert the recommended cleaning cassette. 2. After a few seconds, the cleaning cassette may eject because it may appear to the player as a cassette with a broken tape. If ejection occurs, reinsert the cleaning cassette. Continue this process three or four times until the cleaning cassette is engaged for the time recommended by the cleaning cassette instructions. 3. Eject the cleaning cassette if the cassette does not eject on its own. 4. Press and hold the RECALL button on the radio until CLN appears on the radio display. While still pressing the radio RECALL button, press EJECT on the remote player. Release both buttons when the radio display indicates that the CLN indicator timer has been reset. Parts Information Parts are currently available from GMSPO. DISCLAIMER Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Radio/Stereo: > 01-08-44-005 > Apr > 01 > Radio Display - Error Code Diagnosis/Repair Radio/Stereo: All Technical Service Bulletins Radio Display - Error Code Diagnosis/Repair File In Section: 08 - Body and Accessories Bulletin No.: 01-08-44-005 Date: April, 2001 INFORMATION Subject: Information on Error Codes on Radio Display - Their Cause and Corrective Action Models: 1995 - 1999 Buick LeSabre 1995 - 2002 Buick Century, Park Avenue, Regal 1995 - 1996 Buick Roadmaster 1996 - 1999 Buick Riviera, Skylark 1995 - 1999 Chevrolet Lumina, Monte Carlo 1996 - 1999 Chevrolet Cavalier 1996 Chevrolet Lumina APV 1997 - 2002 Chevrolet Camaro 1998 1999 Chevrolet Venture 1997 - 2002 Chevrolet Corvette 1995 - 1999 Oldsmobile Aurora, Eighty Eight 1995 - 1997 Oldsmobile Cutlass Supreme 1999 - 2000 Oldsmobile Alero 1998 - 2001 Oldsmobile Intrigue 1995 - 1996 Oldsmobile Ninety Eight 1996 - 1999 Oldsmobile Achieva, Silhouette 1996 - 2001 Oldsmobile Bravada 1995 - 1999 Pontiac Bonneville, Sunfire 1995 - 2002 Pontiac Firebird, Grand Prix 1996 - 2000 Pontiac Grand Am 1996 - 1999 Pontiac Trans Sport 1995 - 2002 Chevrolet and GMC C/K, S/T Trucks 1996 - 2002 Chevrolet and GMC M/L Vans 1996 2000 Chevrolet and GMC G Vans This bulletin is being revised to update model years and vehicles. Please discard Corporate Bulletin Number 64-90-04A (Section 9 - Assessories). Starting in 1995, the family style radios, as well as the 12-disc LLAI and 6-disc LLAI (Low Level Audio Interface) changers and the 10-disc FMI (FM Interface) changers, have error codes to help diagnose playback mediums. Some systems will only have an ERR message and no other indicator. If an ERR message is encountered without any other identifier, you may review the following error codes to try to determine the cause of the error and correct it before sending the unit to the authorized service center. If ERR or E (and a number) appears on a customer's radio display, the number may give you a clue to the problem and corrective action. Below is a list of code numbers that may appear on the unit. Important: Not all family radios have these codes. They are dependent on the model year. Cassette Errors - E10: Tight tape error Cause(s): A restricted cassette tape transport or broken cassette drive belt Correction: Substitute a different cassette tape. If there still is an error code, service the unit at an ACDelco(R) Service Center. - E11: Broken Tape Error Cause(s): A broken cassette tape Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Radio/Stereo: > 01-08-44-005 > Apr > 01 > Radio Display - Error Code Diagnosis/Repair > Page 10913 Correction(s): Substitute a different cassette tape - E12: Communication Error Cause(s): A vehicle/radio communication problem or an internal radio communication problem. Correction(s): Disconnect the battery voltage to the radio then reconnect after a few minutes. If there still is an error, service the unit at an ACDelco(R) Service Center. - E13: Tape Communication Error Cause(s): The micro-processor is reading the speed pulses from the tape deck either too fast or too slow. Correction(s): It the tape player is still playing a cassette, try a new cassette. If there is still an error, service the unit at an ACDelco(R) Service Center. - E14: Wrapped Tape Cause(s): The tape is wrapped around the capstan. This means a tape is wound up in the tape player. This error message could appear when a CD adapter is being used. Other causes could be old or damaged tapes. Long playing (90 or 120 minute) tapes are thin and can stretch easily creating this condition. Correction(s): Try playing a known good quality tape. Remove the CD adapter. - Cln Tape Indicator Cause(s): This message appears after 50 hours of accumulated tape play. Correction(s): We suggest cleaning the tape head. Then reset the radio by depressing the eject button for five seconds. Cleaning the heads will not reset the "Cln" display. To reset the "Cln" display, push and hold the eject button for five seconds. The display will return to its normal display. CD Errors - E20: Focus Error Cause(s): The CD player cannot focus on the disc or there is an internal focus problem. Correction(s): Try cleaning the disc or using a new disc. Make sure the disc is loaded correctly. The road could be too rough or there is too much humidity. If the problem is not corrected, service the unit at an ACDelco(R) Service Center. - E21: Tracking Error Cause(s): There is a problem with reading the disc. Correction(s): Try cleaning the disc or using a new disc. Make sure the disc is loaded correctly. The road could be too rough or there is too much humidity. If there is still an error, service the unit at an ACDelco(R) Service Center. - E22: Motor Error Cause(s): The CD motor is not handling the compact disc properly. Correction(s): Service or exchange the unit at an ACDelco(R) Service Center. - E23: Communications Error Cause(s): There is a vehicle/radio communication problem or an internal radio communication problem. Correction(s): Disconnect battery voltage to the radio and then reconnect after a few minutes. If there is still an error, send the unit to an ACDelco(R) Service Center. LLAI CD Changer Errors - E30: Focus Error Cause(s): The CD player cannot focus on the disc or there is an internal focus problem. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Radio/Stereo: > 01-08-44-005 > Apr > 01 > Radio Display - Error Code Diagnosis/Repair > Page 10914 Correction(s): Try cleaning the disc or using a new disc. Make sure the disc is loaded correctly. The road could be too rough or there is too much humidity. If there is still an error, service the unit at an ACDelco(R) Service Center. - E31: Tracking Error Cause(s): There is a problem with reading the disc. Correction(s): Try cleaning the disc or try using a new disc. Make sure the disc is loaded correctly. The road could be too rough or there is too much humidity. If there is still an error, service the unit at an ACDelco(R) Service Center. - E32: Motor Error Cause(s): The CD motor is not handling the compact disc properly or defective magazine mounting screws are interfering with the mechanism. Correction(s): Reload the magazine. If there is still a problem, replace the magazine. If the problem continues, back out the mounting screws. If the condition is corrected, replace the screws with shorter screws or add washers to the existing screws. If this condition still exists, service the unit at an ACDelco(R) Service Center. - E33: CD Changer Communication Error Cause(s): There is a vehicle/radio communication problem or internal radio communication problem. Correction(s): Disconnect battery voltage to the radio and then reconnect after a few minutes. If there is still an error, determine if the problem is with the radio, the harness or the changer. Inspect for correct voltage at all connectors. If there is still an error, service the unit at an ACDelco(R) Service Center. - E34: Changer Door Open - E35: Changer Magazine Empty FMI 10-Disc Changer Errors - E01 Cause: This indicates a malfunction of the disc changer functions. Correction: Before sending the unit in for service, perform the following procedure: 1. Press the reset button on both the changer and the remote. The reset button on the changer is located on the front panel of the unit. It can be activated with the tip of a pin. 2. If the unit does not operate after resetting it, remove the magazine by inserting a business card between the magazine and the mechanism. The lock lever will disengage to allow the magazine to eject. 3. Make sure all CDs are in the magazine and none remain lodged in the carriage. If, upon removing the magazine, a CD is found lodged in the carriage, remove all CDs from the magazine and reinsert the magazine into the changer. 4. Press the eject button. This should cause the lodged CD to move from the carriage into the empty magazine. The magazine should automatically eject and normal operation will return. 5. If the changer fails to resume normal operation, send the unit to an ACDelco(R) Service Center. - E30 Cause: Excessive temperature Correction: Let the temperature of the changer resume to the normal range. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Radio/Stereo: > 01-08-44-005 > Apr > 01 > Radio Display - Error Code Diagnosis/Repair > Page 10915 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns Radio/Stereo: All Technical Service Bulletins Audio - Procedure To Handle Customer Radio Concerns File In Section: 9 - Accessories Bulletin No.: 68-96-O1A Date: October, 1996 INFORMATION Subject: Procedure to Handle Customer Radio Concerns Models: 1997 and Prior Passenger Cars and Trucks This bulletin is being revised to change the Sales Center Information to Service Center Information. Please discard Corporate Bulletin Number 68-96-01 (Section 9 - Accessories). Many of the radios being returned to the Delco Electronics remanufacturing centers have been misdiagnosed. This misdiagnosis results in unnecessary customer comebacks, decreased customer satisfaction and reduces the availability of exchange radios. To resolve these issues, the following information was developed to give General Motors' dealers a common service process to handle customer audio system concerns. When a customer either calls or comes in with a concern about the radio system in their vehicle, it is important that as much information as possible is gathered. This process begins with the Service Consultant asking the customer specific questions related to their vehicle as outlined on the Service Writer/Customer Check list. Once the Service Consultant has completed the diagnostic worksheet, it should be attached to the customer repair order for the technician. This worksheet should help the technician determine if the concern is vehicle related or radio related. Two excellent service manuals are also available for this purpose and are available from General Motors at the address shown below. A service bulletin, 34-92-12, Radio Frequency Interference Diagnosis, is also available as is assistance from the Divisional Technical Assistance Centers. Mascotech Mktg. Service 1972 Brown Road Auburn Hills, ML 48326 1-800-393-4831 Delco Electronics Sound Service Audio Systems Diagnostic Guide P/N 19007.03-1A @ $10.00 per manual STG Audio Systems Training manual P/N 19007.03-2 @ $15.00 per manual Repairs to the vehicle or the audio system can usually be done very quickly and the vehicle returned to the customer that day. If the diagnosis indicates that the radio needs to be replaced, remove the radio from the vehicle and order an exchange radio from your local AC Delco radio exchange center. There are 28 approved AC Delco exchange centers nationally (listing attached). If your local exchange center does not have the required exchange radio, it is important that you contact the AC Delco locator service. This service can be found on the Service Parts TRACS system 1-800-433-6961, prompt 4. It will be necessary to request overnight shipping so that the owner's vehicle is retained at your dealership for only one night. If the vehicle is kept overnight and it is a warranty repair, the customer should be offered courtesy transportation or alternate transportation. Please do not return the vehicle with the suspect radio installed or without a radio. Many of our vehicles today use a multiplex wiring system and the vehicle will not run correctly without a radio. When you receive the exchange radio, please return the removed radio to the AC Delco Exchange Center within 24 hours (please enclose the diagnostic worksheet that the Service Consultant and the Technician used with the removed radio along with the 1078 form). This will help the AC Delco Exchange Center. In the event you know the vehicle will need a radio before the customer brings the vehicle in, every effort should be made to have a pre-exchanged radio available. A radio identification list is attached to help you select the correct radio. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10920 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10921 AC Delco AUTHORIZED ELECTRONIC SERVICE CENTERS Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10922 Duplicate form for your convenience SERVICE WRITER/CUSTOMER CHECK LIST Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10923 RECEPTION/NOISE CONCERN: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10924 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10925 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10926 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10927 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10928 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10929 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10930 1997 APPLICATIONS Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Radio/Stereo: > 669601 > Aug > 96 > Radios - Revised With Integral Cooling Fan Operation Radio/Stereo: All Technical Service Bulletins Radios - Revised With Integral Cooling Fan Operation File in Section: 9 - Accessories Bulletin No.: 66-96-01 Date: August, 1996 INFORMATION Subject: New Radios with Integral Cooling Fan Models: 1996 Chevrolet and GMC C/K Models Effective May 6, 1996, Delco began shipping to assembly plants, revised radios with an integral cooling fan. Some customers may ask about the slight sound created when the fan is operating. The purpose of the fan is to maintain an optimal operating temperature in the unit only while the cassette or compact disc player is operating. Because the fan runs only when a cassette or compact disc is being played, it is recommended that cassette or compact disc be removed when not in use. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Other Service Bulletins for Radio/Stereo: > 01-08-44-006A > Jun > 01 > Audio System - Clearing `CLN' Message From Display Radio/Stereo: All Technical Service Bulletins Audio System - Clearing `CLN' Message From Display File In Section: 08 - Body and Accessories Bulletin No.: 01-08-44-006A Date: June, 2001 INFORMATION Subject: Cleaning the Cassette Tape Player and Clearing the CLN Message from the Radio Display Models: 1996-2002 Chevrolet and GMC Truck Models With Remote Cassette Tape Player (RP0 UP0) This bulletin is being revised to include additional model years and models, parts information, and to provide a procedure for cleaning the cassette tape player and resetting the CLN indicator on the radio display. Please discard Corporate Bulletin Number 01-08-44-006 (Section 08 - Body and Accessories). When the CLN message appears on the audio system, it indicates that the cassette tape player requires cleaning. Customers should follow the listed instructions. The recommended cleaning method for the remote cassette player is to use a scrubbing action, non-abrasive cleaning cassette, GM P/N 12344789. The cleaning cassette scrubs the tape head as the hubs of the cleaner cassette turn. Use the following procedure to clean the remote cassette player and reset the CLN indicator on the radio. 1. With the radio ON, insert the recommended cleaning cassette. 2. After a few seconds, the cleaning cassette may eject because it may appear to the player as a cassette with a broken tape. If ejection occurs, reinsert the cleaning cassette. Continue this process three or four times until the cleaning cassette is engaged for the time recommended by the cleaning cassette instructions. 3. Eject the cleaning cassette if the cassette does not eject on its own. 4. Press and hold the RECALL button on the radio until CLN appears on the radio display. While still pressing the radio RECALL button, press EJECT on the remote player. Release both buttons when the radio display indicates that the CLN indicator timer has been reset. Parts Information Parts are currently available from GMSPO. DISCLAIMER Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Other Service Bulletins for Radio/Stereo: > 01-08-44-005 > Apr > 01 > Radio Display - Error Code Diagnosis/Repair Radio/Stereo: All Technical Service Bulletins Radio Display - Error Code Diagnosis/Repair File In Section: 08 - Body and Accessories Bulletin No.: 01-08-44-005 Date: April, 2001 INFORMATION Subject: Information on Error Codes on Radio Display - Their Cause and Corrective Action Models: 1995 - 1999 Buick LeSabre 1995 - 2002 Buick Century, Park Avenue, Regal 1995 - 1996 Buick Roadmaster 1996 - 1999 Buick Riviera, Skylark 1995 - 1999 Chevrolet Lumina, Monte Carlo 1996 - 1999 Chevrolet Cavalier 1996 Chevrolet Lumina APV 1997 - 2002 Chevrolet Camaro 1998 1999 Chevrolet Venture 1997 - 2002 Chevrolet Corvette 1995 - 1999 Oldsmobile Aurora, Eighty Eight 1995 - 1997 Oldsmobile Cutlass Supreme 1999 - 2000 Oldsmobile Alero 1998 - 2001 Oldsmobile Intrigue 1995 - 1996 Oldsmobile Ninety Eight 1996 - 1999 Oldsmobile Achieva, Silhouette 1996 - 2001 Oldsmobile Bravada 1995 - 1999 Pontiac Bonneville, Sunfire 1995 - 2002 Pontiac Firebird, Grand Prix 1996 - 2000 Pontiac Grand Am 1996 - 1999 Pontiac Trans Sport 1995 - 2002 Chevrolet and GMC C/K, S/T Trucks 1996 - 2002 Chevrolet and GMC M/L Vans 1996 2000 Chevrolet and GMC G Vans This bulletin is being revised to update model years and vehicles. Please discard Corporate Bulletin Number 64-90-04A (Section 9 - Assessories). Starting in 1995, the family style radios, as well as the 12-disc LLAI and 6-disc LLAI (Low Level Audio Interface) changers and the 10-disc FMI (FM Interface) changers, have error codes to help diagnose playback mediums. Some systems will only have an ERR message and no other indicator. If an ERR message is encountered without any other identifier, you may review the following error codes to try to determine the cause of the error and correct it before sending the unit to the authorized service center. If ERR or E (and a number) appears on a customer's radio display, the number may give you a clue to the problem and corrective action. Below is a list of code numbers that may appear on the unit. Important: Not all family radios have these codes. They are dependent on the model year. Cassette Errors - E10: Tight tape error Cause(s): A restricted cassette tape transport or broken cassette drive belt Correction: Substitute a different cassette tape. If there still is an error code, service the unit at an ACDelco(R) Service Center. - E11: Broken Tape Error Cause(s): A broken cassette tape Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Other Service Bulletins for Radio/Stereo: > 01-08-44-005 > Apr > 01 > Radio Display - Error Code Diagnosis/Repair > Page 10944 Correction(s): Substitute a different cassette tape - E12: Communication Error Cause(s): A vehicle/radio communication problem or an internal radio communication problem. Correction(s): Disconnect the battery voltage to the radio then reconnect after a few minutes. If there still is an error, service the unit at an ACDelco(R) Service Center. - E13: Tape Communication Error Cause(s): The micro-processor is reading the speed pulses from the tape deck either too fast or too slow. Correction(s): It the tape player is still playing a cassette, try a new cassette. If there is still an error, service the unit at an ACDelco(R) Service Center. - E14: Wrapped Tape Cause(s): The tape is wrapped around the capstan. This means a tape is wound up in the tape player. This error message could appear when a CD adapter is being used. Other causes could be old or damaged tapes. Long playing (90 or 120 minute) tapes are thin and can stretch easily creating this condition. Correction(s): Try playing a known good quality tape. Remove the CD adapter. - Cln Tape Indicator Cause(s): This message appears after 50 hours of accumulated tape play. Correction(s): We suggest cleaning the tape head. Then reset the radio by depressing the eject button for five seconds. Cleaning the heads will not reset the "Cln" display. To reset the "Cln" display, push and hold the eject button for five seconds. The display will return to its normal display. CD Errors - E20: Focus Error Cause(s): The CD player cannot focus on the disc or there is an internal focus problem. Correction(s): Try cleaning the disc or using a new disc. Make sure the disc is loaded correctly. The road could be too rough or there is too much humidity. If the problem is not corrected, service the unit at an ACDelco(R) Service Center. - E21: Tracking Error Cause(s): There is a problem with reading the disc. Correction(s): Try cleaning the disc or using a new disc. Make sure the disc is loaded correctly. The road could be too rough or there is too much humidity. If there is still an error, service the unit at an ACDelco(R) Service Center. - E22: Motor Error Cause(s): The CD motor is not handling the compact disc properly. Correction(s): Service or exchange the unit at an ACDelco(R) Service Center. - E23: Communications Error Cause(s): There is a vehicle/radio communication problem or an internal radio communication problem. Correction(s): Disconnect battery voltage to the radio and then reconnect after a few minutes. If there is still an error, send the unit to an ACDelco(R) Service Center. LLAI CD Changer Errors - E30: Focus Error Cause(s): The CD player cannot focus on the disc or there is an internal focus problem. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Other Service Bulletins for Radio/Stereo: > 01-08-44-005 > Apr > 01 > Radio Display - Error Code Diagnosis/Repair > Page 10945 Correction(s): Try cleaning the disc or using a new disc. Make sure the disc is loaded correctly. The road could be too rough or there is too much humidity. If there is still an error, service the unit at an ACDelco(R) Service Center. - E31: Tracking Error Cause(s): There is a problem with reading the disc. Correction(s): Try cleaning the disc or try using a new disc. Make sure the disc is loaded correctly. The road could be too rough or there is too much humidity. If there is still an error, service the unit at an ACDelco(R) Service Center. - E32: Motor Error Cause(s): The CD motor is not handling the compact disc properly or defective magazine mounting screws are interfering with the mechanism. Correction(s): Reload the magazine. If there is still a problem, replace the magazine. If the problem continues, back out the mounting screws. If the condition is corrected, replace the screws with shorter screws or add washers to the existing screws. If this condition still exists, service the unit at an ACDelco(R) Service Center. - E33: CD Changer Communication Error Cause(s): There is a vehicle/radio communication problem or internal radio communication problem. Correction(s): Disconnect battery voltage to the radio and then reconnect after a few minutes. If there is still an error, determine if the problem is with the radio, the harness or the changer. Inspect for correct voltage at all connectors. If there is still an error, service the unit at an ACDelco(R) Service Center. - E34: Changer Door Open - E35: Changer Magazine Empty FMI 10-Disc Changer Errors - E01 Cause: This indicates a malfunction of the disc changer functions. Correction: Before sending the unit in for service, perform the following procedure: 1. Press the reset button on both the changer and the remote. The reset button on the changer is located on the front panel of the unit. It can be activated with the tip of a pin. 2. If the unit does not operate after resetting it, remove the magazine by inserting a business card between the magazine and the mechanism. The lock lever will disengage to allow the magazine to eject. 3. Make sure all CDs are in the magazine and none remain lodged in the carriage. If, upon removing the magazine, a CD is found lodged in the carriage, remove all CDs from the magazine and reinsert the magazine into the changer. 4. Press the eject button. This should cause the lodged CD to move from the carriage into the empty magazine. The magazine should automatically eject and normal operation will return. 5. If the changer fails to resume normal operation, send the unit to an ACDelco(R) Service Center. - E30 Cause: Excessive temperature Correction: Let the temperature of the changer resume to the normal range. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Other Service Bulletins for Radio/Stereo: > 01-08-44-005 > Apr > 01 > Radio Display - Error Code Diagnosis/Repair > Page 10946 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Other Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns Radio/Stereo: All Technical Service Bulletins Audio - Procedure To Handle Customer Radio Concerns File In Section: 9 - Accessories Bulletin No.: 68-96-O1A Date: October, 1996 INFORMATION Subject: Procedure to Handle Customer Radio Concerns Models: 1997 and Prior Passenger Cars and Trucks This bulletin is being revised to change the Sales Center Information to Service Center Information. Please discard Corporate Bulletin Number 68-96-01 (Section 9 - Accessories). Many of the radios being returned to the Delco Electronics remanufacturing centers have been misdiagnosed. This misdiagnosis results in unnecessary customer comebacks, decreased customer satisfaction and reduces the availability of exchange radios. To resolve these issues, the following information was developed to give General Motors' dealers a common service process to handle customer audio system concerns. When a customer either calls or comes in with a concern about the radio system in their vehicle, it is important that as much information as possible is gathered. This process begins with the Service Consultant asking the customer specific questions related to their vehicle as outlined on the Service Writer/Customer Check list. Once the Service Consultant has completed the diagnostic worksheet, it should be attached to the customer repair order for the technician. This worksheet should help the technician determine if the concern is vehicle related or radio related. Two excellent service manuals are also available for this purpose and are available from General Motors at the address shown below. A service bulletin, 34-92-12, Radio Frequency Interference Diagnosis, is also available as is assistance from the Divisional Technical Assistance Centers. Mascotech Mktg. Service 1972 Brown Road Auburn Hills, ML 48326 1-800-393-4831 Delco Electronics Sound Service Audio Systems Diagnostic Guide P/N 19007.03-1A @ $10.00 per manual STG Audio Systems Training manual P/N 19007.03-2 @ $15.00 per manual Repairs to the vehicle or the audio system can usually be done very quickly and the vehicle returned to the customer that day. If the diagnosis indicates that the radio needs to be replaced, remove the radio from the vehicle and order an exchange radio from your local AC Delco radio exchange center. There are 28 approved AC Delco exchange centers nationally (listing attached). If your local exchange center does not have the required exchange radio, it is important that you contact the AC Delco locator service. This service can be found on the Service Parts TRACS system 1-800-433-6961, prompt 4. It will be necessary to request overnight shipping so that the owner's vehicle is retained at your dealership for only one night. If the vehicle is kept overnight and it is a warranty repair, the customer should be offered courtesy transportation or alternate transportation. Please do not return the vehicle with the suspect radio installed or without a radio. Many of our vehicles today use a multiplex wiring system and the vehicle will not run correctly without a radio. When you receive the exchange radio, please return the removed radio to the AC Delco Exchange Center within 24 hours (please enclose the diagnostic worksheet that the Service Consultant and the Technician used with the removed radio along with the 1078 form). This will help the AC Delco Exchange Center. In the event you know the vehicle will need a radio before the customer brings the vehicle in, every effort should be made to have a pre-exchanged radio available. A radio identification list is attached to help you select the correct radio. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Other Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10951 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Other Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10952 AC Delco AUTHORIZED ELECTRONIC SERVICE CENTERS Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Other Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10953 Duplicate form for your convenience SERVICE WRITER/CUSTOMER CHECK LIST Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Other Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10954 RECEPTION/NOISE CONCERN: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Other Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10955 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Other Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10956 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Other Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10957 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Other Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10958 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Other Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10959 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Other Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10960 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > All Other Service Bulletins for Radio/Stereo: > 689601A > Oct > 96 > Audio - Procedure To Handle Customer Radio Concerns > Page 10961 1997 APPLICATIONS Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Technical Service Bulletins > Page 10962 Cargo Lamp Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions Radio/Stereo: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10965 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10966 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10967 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10968 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10969 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10970 Radio/Stereo: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10971 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10972 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10973 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10974 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10975 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10976 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10977 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10978 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10979 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10980 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10981 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10982 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10983 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10984 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10985 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10986 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10987 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10988 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10989 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10990 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10991 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10992 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10993 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10994 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10995 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10996 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10997 Radio/Stereo: Connector Views C1: Radio Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Diagram Information and Instructions > Page 10998 C2: Radio Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Radio/Stereo > Component Information > Diagrams > Page 10999 Radio/Stereo: Service and Repair 1. Disconnect battery ground cable. 2. Remove steering column filler panel and ashtray. 3. Release side radio retainer clips using a small screw driver. 4. Remove radio by sliding forward. 5. Disconnect electrical connectors and antenna connection. 6. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Locations > LH Rear Door Speaker: Locations LH Rear Door In rear LH Door Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Locations > LH Rear Door > Page 11004 Speaker: Locations LH Rear Roof In rear Headliner, LH side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Locations > LH Rear Door > Page 11005 Speaker: Locations RH Rear Door In rear RH Door Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Locations > LH Rear Door > Page 11006 Speaker: Locations Speaker LH In front LH Door RH In front RH Door Rear Speakers Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions Speaker: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11009 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11010 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11011 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11012 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11013 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11014 Speaker: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11015 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11016 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11017 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11018 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11019 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11020 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11021 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11022 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11023 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11024 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11025 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11026 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11027 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11028 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11029 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11030 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11031 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11032 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11033 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11034 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11035 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11036 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11037 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11038 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11039 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11040 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Speaker > Component Information > Diagrams > Diagram Information and Instructions > Page 11041 C410: Cross Body HARN To Rear Speakers HARN Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Technical Service Bulletins > Customer Interest: > 549001A > Mar > 97 > Radio - CLN Indicator ON Tape Player: Customer Interest Radio - CLN Indicator ON File In Section: 9 - Accessories Bulletin No.: 54-90-01A Date: March, 1997 Subject: "CLN" Indicator Appears On Radio Display and Does Not Turn Off (Reset "CLN" Indicator with the Eject Button On Tape) Models: 1995-96 Buick Roadmaster 1995-97 Buick Regal, Park Avenue, LeSabre 1996-97 Buick Skylark, Riviera 1996-97 Cadillac Eldorado, Seville, Concours 1994-97 Chevrolet Lumina 1995-97 Chevrolet Monte Carlo 1996-97 Chevrolet Cavalier, Lumina Apv 1997 Chevrolet Corvette 1994-97 Oldsmobile Regency, Eighty-Eight 1995-97 Oldsmobile Cutlass Supreme 1995-97 Oldsmobile Aurora 1996-97 Oldsmobile Achieva 1997 Oldsmobile Silhouette 1994-97 Pontiac Grand Prix, Bonneville, Firebird 1995-97 Pontiac Sunfire 1996-97 Pontiac Grand Am, Trans Sport 1995-97 Chevrolet and GMC C/K Models 1996.5-97 Chevrolet and GMC M/L, G Models This bulletin is being revised to include current model year and additional models. Also included is the procedure for the remote cassette unit. Condition Some owners may comment that "CLN" appears on radio display and does not turn off after tape heads have been cleaned. Cause The "CLN" display is a reminder for the customer that the tape heads need to be cleaned. This reminder will appear after 50 hours of tape usage. The "CLN" indicator will not automatically turn off after the tape heads have been cleaned. Correction Integral Cassette Radios The customer must reset the "CLN" indicator manually. To reset after proper cleaning of the tape heads push the EJECT button and hold for 5 seconds until the display clears. The "CLN" reminder will be reset and start timing the hours of tape usage. The radio display will resume its normal operating functions. Remote Cassette Unit The customer must reset the "CLN" indicator manually. To reset after proper cleaning of the tape heads push the EJECT button on the remote and the RECALL button on the radio and hold for 5 seconds until the display clears. The "CLN" reminder will be reset and start timing the hours of tape usage. The radio display will resume its normal operating functions. Important: Radio and playback functions are discussed in Section 9A of the Service Manuals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Technical Service Bulletins > Customer Interest: > 549001 > Dec > 95 > Radio Display - CLN Indicator Appears Won't Turn OFF Tape Player: Customer Interest Radio Display - CLN Indicator Appears Won't Turn OFF File In Section: 9 - Accessories Bulletin No.: 54-90-01 Date: December, 1995 Subject: "CLN" Indicator Appears on Radio Display and Does Not Turn Off (Reset "CLN" Indicator with the Eject Button on Tape) Models: 1995-96 Buick Regal, Road master, Park Avenue, LeSabre 1996 Buick Skylark, Riviera 1996 Cadillac Eldorado, Seville, Concours 1994-96 Chevrolet Lumina 1995-96 Chevrolet Monte Carlo 1996 Chevrolet Cavalier, Lumina APV 1994-96 Oldsmobile Ninety Eight, Eighty Eight 1995-96 Oldsmobile Cutlass Supreme 1995-96 Oldsmobile Aurora 1996 Oldsmobile Achieva 1994-96 Pontiac Grand Prix, Bonneville, Firebird 1995-96 Pontiac Sunfire 1996 Pontiac Grand Am, Trans Sport 1995-96 Chevrolet and GMC Truck C/K Models 1996.5 Chevrolet and GMC Truck M, G Models Condition Some owners may comment that "CLN" appears on radio display and does not turn off after tape heads have been cleaned. Cause The "CLN" display is a reminder for the customer that the tape heads need to be cleaned. This reminder will appear after 50 hours of tape usage. The "CLN" indicator will not automatically turn off after the tape heads have been cleaned. Correction The customer must reset the "CLN" indicator manually to reset after proper cleaning of the tape heads push the eject button and hold for 5 seconds until the display clears. The "CLN" reminder will be reset and start timing the hours of tape usage. The radio display will resume its normal operating functions. Important: Radio and playback functions are discussed in Section 9A of the service manuals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Tape Player: > 01-08-44-006A > Jun > 01 > Audio System - Clearing `CLN' Message From Display Tape Player: All Technical Service Bulletins Audio System - Clearing `CLN' Message From Display File In Section: 08 - Body and Accessories Bulletin No.: 01-08-44-006A Date: June, 2001 INFORMATION Subject: Cleaning the Cassette Tape Player and Clearing the CLN Message from the Radio Display Models: 1996-2002 Chevrolet and GMC Truck Models With Remote Cassette Tape Player (RP0 UP0) This bulletin is being revised to include additional model years and models, parts information, and to provide a procedure for cleaning the cassette tape player and resetting the CLN indicator on the radio display. Please discard Corporate Bulletin Number 01-08-44-006 (Section 08 - Body and Accessories). When the CLN message appears on the audio system, it indicates that the cassette tape player requires cleaning. Customers should follow the listed instructions. The recommended cleaning method for the remote cassette player is to use a scrubbing action, non-abrasive cleaning cassette, GM P/N 12344789. The cleaning cassette scrubs the tape head as the hubs of the cleaner cassette turn. Use the following procedure to clean the remote cassette player and reset the CLN indicator on the radio. 1. With the radio ON, insert the recommended cleaning cassette. 2. After a few seconds, the cleaning cassette may eject because it may appear to the player as a cassette with a broken tape. If ejection occurs, reinsert the cleaning cassette. Continue this process three or four times until the cleaning cassette is engaged for the time recommended by the cleaning cassette instructions. 3. Eject the cleaning cassette if the cassette does not eject on its own. 4. Press and hold the RECALL button on the radio until CLN appears on the radio display. While still pressing the radio RECALL button, press EJECT on the remote player. Release both buttons when the radio display indicates that the CLN indicator timer has been reset. Parts Information Parts are currently available from GMSPO. DISCLAIMER Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Tape Player: > 549001A > Mar > 97 > Radio - CLN Indicator ON Tape Player: All Technical Service Bulletins Radio - CLN Indicator ON File In Section: 9 - Accessories Bulletin No.: 54-90-01A Date: March, 1997 Subject: "CLN" Indicator Appears On Radio Display and Does Not Turn Off (Reset "CLN" Indicator with the Eject Button On Tape) Models: 1995-96 Buick Roadmaster 1995-97 Buick Regal, Park Avenue, LeSabre 1996-97 Buick Skylark, Riviera 1996-97 Cadillac Eldorado, Seville, Concours 1994-97 Chevrolet Lumina 1995-97 Chevrolet Monte Carlo 1996-97 Chevrolet Cavalier, Lumina Apv 1997 Chevrolet Corvette 1994-97 Oldsmobile Regency, Eighty-Eight 1995-97 Oldsmobile Cutlass Supreme 1995-97 Oldsmobile Aurora 1996-97 Oldsmobile Achieva 1997 Oldsmobile Silhouette 1994-97 Pontiac Grand Prix, Bonneville, Firebird 1995-97 Pontiac Sunfire 1996-97 Pontiac Grand Am, Trans Sport 1995-97 Chevrolet and GMC C/K Models 1996.5-97 Chevrolet and GMC M/L, G Models This bulletin is being revised to include current model year and additional models. Also included is the procedure for the remote cassette unit. Condition Some owners may comment that "CLN" appears on radio display and does not turn off after tape heads have been cleaned. Cause The "CLN" display is a reminder for the customer that the tape heads need to be cleaned. This reminder will appear after 50 hours of tape usage. The "CLN" indicator will not automatically turn off after the tape heads have been cleaned. Correction Integral Cassette Radios The customer must reset the "CLN" indicator manually. To reset after proper cleaning of the tape heads push the EJECT button and hold for 5 seconds until the display clears. The "CLN" reminder will be reset and start timing the hours of tape usage. The radio display will resume its normal operating functions. Remote Cassette Unit The customer must reset the "CLN" indicator manually. To reset after proper cleaning of the tape heads push the EJECT button on the remote and the RECALL button on the radio and hold for 5 seconds until the display clears. The "CLN" reminder will be reset and start timing the hours of tape usage. The radio display will resume its normal operating functions. Important: Radio and playback functions are discussed in Section 9A of the Service Manuals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Tape Player: > 549001 > Dec > 95 > Radio Display - CLN Indicator Appears Won't Turn OFF Tape Player: All Technical Service Bulletins Radio Display - CLN Indicator Appears Won't Turn OFF File In Section: 9 - Accessories Bulletin No.: 54-90-01 Date: December, 1995 Subject: "CLN" Indicator Appears on Radio Display and Does Not Turn Off (Reset "CLN" Indicator with the Eject Button on Tape) Models: 1995-96 Buick Regal, Road master, Park Avenue, LeSabre 1996 Buick Skylark, Riviera 1996 Cadillac Eldorado, Seville, Concours 1994-96 Chevrolet Lumina 1995-96 Chevrolet Monte Carlo 1996 Chevrolet Cavalier, Lumina APV 1994-96 Oldsmobile Ninety Eight, Eighty Eight 1995-96 Oldsmobile Cutlass Supreme 1995-96 Oldsmobile Aurora 1996 Oldsmobile Achieva 1994-96 Pontiac Grand Prix, Bonneville, Firebird 1995-96 Pontiac Sunfire 1996 Pontiac Grand Am, Trans Sport 1995-96 Chevrolet and GMC Truck C/K Models 1996.5 Chevrolet and GMC Truck M, G Models Condition Some owners may comment that "CLN" appears on radio display and does not turn off after tape heads have been cleaned. Cause The "CLN" display is a reminder for the customer that the tape heads need to be cleaned. This reminder will appear after 50 hours of tape usage. The "CLN" indicator will not automatically turn off after the tape heads have been cleaned. Correction The customer must reset the "CLN" indicator manually to reset after proper cleaning of the tape heads push the eject button and hold for 5 seconds until the display clears. The "CLN" reminder will be reset and start timing the hours of tape usage. The radio display will resume its normal operating functions. Important: Radio and playback functions are discussed in Section 9A of the service manuals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Technical Service Bulletins > All Other Service Bulletins for Tape Player: > 01-08-44-006A > Jun > 01 > Audio System - Clearing `CLN' Message From Display Tape Player: All Technical Service Bulletins Audio System - Clearing `CLN' Message From Display File In Section: 08 - Body and Accessories Bulletin No.: 01-08-44-006A Date: June, 2001 INFORMATION Subject: Cleaning the Cassette Tape Player and Clearing the CLN Message from the Radio Display Models: 1996-2002 Chevrolet and GMC Truck Models With Remote Cassette Tape Player (RP0 UP0) This bulletin is being revised to include additional model years and models, parts information, and to provide a procedure for cleaning the cassette tape player and resetting the CLN indicator on the radio display. Please discard Corporate Bulletin Number 01-08-44-006 (Section 08 - Body and Accessories). When the CLN message appears on the audio system, it indicates that the cassette tape player requires cleaning. Customers should follow the listed instructions. The recommended cleaning method for the remote cassette player is to use a scrubbing action, non-abrasive cleaning cassette, GM P/N 12344789. The cleaning cassette scrubs the tape head as the hubs of the cleaner cassette turn. Use the following procedure to clean the remote cassette player and reset the CLN indicator on the radio. 1. With the radio ON, insert the recommended cleaning cassette. 2. After a few seconds, the cleaning cassette may eject because it may appear to the player as a cassette with a broken tape. If ejection occurs, reinsert the cleaning cassette. Continue this process three or four times until the cleaning cassette is engaged for the time recommended by the cleaning cassette instructions. 3. Eject the cleaning cassette if the cassette does not eject on its own. 4. Press and hold the RECALL button on the radio until CLN appears on the radio display. While still pressing the radio RECALL button, press EJECT on the remote player. Release both buttons when the radio display indicates that the CLN indicator timer has been reset. Parts Information Parts are currently available from GMSPO. DISCLAIMER Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions Tape Player: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11074 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11075 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11076 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11077 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11078 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11079 Tape Player: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11080 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11081 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11082 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11083 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11084 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11085 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11086 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11087 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11088 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11089 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11090 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11091 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11092 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11093 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11094 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11095 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11096 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11097 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11098 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11099 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11100 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11101 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11102 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11103 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11104 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Radio, Stereo, and Compact Disc > Tape Player > Component Information > Diagrams > Diagram Information and Instructions > Page 11105 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Relays and Modules - Accessories and Optional Equipment > Emergency Contact Module > Component Information > Technical Service Bulletins > OnStar(R) - Analog Only Systems Information Emergency Contact Module: Technical Service Bulletins OnStar(R) - Analog Only Systems Information INFORMATION Bulletin No.: 06-08-64-007A Date: September 22, 2008 Subject: Information on OnStar(R) Analog-Only Systems Models Supercede: This bulletin is being revised to update the models affected list above. Please discard Corporate Bulletin Number 06-08-46-007 (Section 08 - Body & Accessories). All vehicles equipped with OnStar(R) listed in this bulletin were built with Analog-Only OnStar(R) Hardware. OnStar(R) equipped vehicles with analog-only equipment were designed to operate only on the analog wireless network and cannot be upgraded for digital network compatibility. Vehicles with this equipment will no longer be able to receive OnStar(R) services beginning January 1, 2008. At that time, service will be available only through Dual-Mode (Analog / Digital) equipment. Analog-Only vehicles cannot be upgraded to digital equipment. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Relays and Modules - Accessories and Optional Equipment > Emergency Contact Module > Component Information > Technical Service Bulletins > OnStar(R) - Analog Only Systems Information > Page 11111 Emergency Contact Module: Technical Service Bulletins OnStar(R) - Aftermarket Device Interference Information INFORMATION Bulletin No.: 08-08-46-004 Date: August 14, 2008 Subject: Information on Aftermarket Device Interference with OnStar(R) Diagnostic Services Models: 2009 and Prior GM Passenger Car and Truck (including Saturn) 2009 and Prior HUMMER H2, H3 Models 2009 and Prior Saab 9-7X with OnStar(R) (RPO UE1) This bulletin is being issued to provide dealer service personnel with information regarding aftermarket devices connected to the Diagnostic Link Connector (DLC) and the impact to OnStar(R) diagnostic probes and Vehicle Diagnostic e-mails. Certain aftermarket devices, when connected to the Diagnostic Link Connector, such as, but not limited to, Scan Tools, Trip Computers, Fuel Economy Analyzers and Insurance Tracking Devices, interfere with OnStar's ability to perform a diagnostic probe when requested (via a blue button call) by a subscriber. These devices also prohibit the ability to gather diagnostic and tire pressure data for a subscriber's scheduled OnStar(R) Vehicle Diagnostic (OVD) e-mail. These aftermarket devices utilize the Vehicles serial data bus to perform data requests and/or information gathering. When these devices are requesting data, OnStar(R) is designed not to interfere with any data request being made by these devices as required by OBD II regulations. The OnStar(R) advisor is unable to definitively detect the presence of these devices and will only be able to inform the caller or requester of the unsuccessful or incomplete probe and may in some cases refer the subscriber/requester to take the vehicle to a dealer for diagnosis of the concern. When performing a diagnostic check for an unsuccessful or incomplete OnStar(R) diagnostic probe, or for concerns regarding completeness of the OnStar(R) Vehicle Diagnostic (OVD) e-mail, verify that an aftermarket device was not present at the time of the requested probe. Regarding the OVD e-mail, if an aftermarket device is interfering (including a Scan Tool of any type), the e-mail will consistently display a "yellow" indication in diagnostics section for all vehicle systems except the OnStar(R) System and Tire Pressure data (not available on all vehicles) will not be displayed (i.e. section is collapsed). Successful diagnostic probes and complete OVD e-mails will resume following the removal or disconnecting of the off-board device. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Relays and Modules - Accessories and Optional Equipment > Emergency Contact Module > Component Information > Technical Service Bulletins > OnStar(R) - Analog Only Systems Information > Page 11112 Emergency Contact Module: Technical Service Bulletins OnStar - Analog-Only Systems Information Bulletin No.: 06-08-46-007 Date: December 13, 2006 INFORMATION Subject: Information on OnStar(R) Analog-Only Systems Models: 1996-2001 GM Passenger Cars and Trucks Plus: 2002 Buick LeSabre, Rendezvous 2002-2003 Buick Century, Regal 2002-2005 Buick Park Avenue 2002 Cadillac Eldorado, Escalade Models 2002 Chevrolet Avalanche, Silverado, Suburban, Tahoe, Venture 2002 GMC Denali, Denali XL, Jimmy, Sierra, Yukon, Yukon XL 2002 Oldsmobile Intrigue, Silhouette 2002-2003 Oldsmobile Aurora 2002 Pontiac Aztek, Bonneville, Montana 2002-2003 Pontiac Grand Prix with OnStar(R) (RPO UE1) All vehicles equipped with OnStar(R) listed in this bulletin were built with Analog-Only OnStar(R) Hardware. OnStar(R) equipped vehicles with analog-only equipment were designed to operate only on the analog wireless network and cannot be upgraded for digital network compatibility. Vehicles with this equipment will no longer be able to receive OnStar(R) services beginning January 1, 2008. At that time, service will be available only through Dual-Mode (Analog/Digital) equipment. Analog-Only vehicles cannot be upgraded to digital equipment. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Relays and Modules - Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > Customer Interest for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules Relay Module: Customer Interest Electrical - MIL ON/DTC's Set By Various Control Modules TECHNICAL Bulletin No.: 09-06-03-004D Date: December 08, 2010 Subject: Intermittent No Crank/No Start, No Module Communication, MIL, Warning Lights, Vehicle Messages or DTCs Set by Various Control Modules - Diagnosing and Repairing Fretting Corrosion (Disconnect Affected Connector and Apply Dielectric Lubricant) Models: 2011 and Prior GM Passenger Cars and Trucks Attention: This repair can be applied to ANY electrical connection including, but not limited to: lighting, body electrical, in-line connections, powertrain control sensors, etc. DO NOT over apply lubricant to the point where it prevents the full engagement of sealed connectors. A light coating on the terminal surfaces is sufficient to correct the condition. Supercede: This bulletin is being revised to update the Attention statement and add the 2011 model year. Please discard Corporate Bulletin Number 09-06-03-004C (Section 06 Engine/Propulsion System). Condition Some customers may comment on any of the following conditions: - An intermittent no crank/no start - Intermittent malfunction indicator lamp (MIL) illumination - Intermittent service lamp illumination - Intermittent service message(s) being displayed The technician may determine that he is unable to duplicate the intermittent condition. Cause This condition may be caused by a buildup of nonconductive insulating oxidized debris known as fretting corrosion, occurring between two electrical contact surfaces of the connection or connector. This may be caused by any of the following conditions: - Vibration - Thermal cycling - Poor connection/terminal retention - Micro motion - A connector, component or wiring harness not properly secured resulting in movement On low current signal circuits this condition may cause high resistance, resulting in intermittent connections. On high current power circuits this condition may cause permanent increases in the resistance and may cause a device to become inoperative. Representative List of Control Modules and Components The following is only a representative list of control modules and components that may be affected by this connection or connector condition and DOES NOT include every possible module or component for every vehicle. - Blower Control Module - Body Control Module (BCM) - Communication Interface Module (CIM) - Cooling Fan Control Module - Electronic Brake Control Module (EBCM) - Electronic Brake and Traction Control Module (EBTCM) - Electronic Suspension Control (ESC) Module - Engine Control Module (ECM) - Heating, Ventilation and Air Conditioning (HVAC) Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Relays and Modules - Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > Customer Interest for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 11121 - HVAC Actuator - Inflatable Restraint Sensing and Diagnostic Module (SDM) - Any AIR BAG module - Seatbelt Lap Anchor Pretensioner - Seatbelt Retractor Pretensioner - An SIR system connection or connector condition resulting in the following DTCs being set: B0015, B0016, B0019, B0020, B0022, or B0023 - Powertrain Control Module (PCM) - Remote Control Door Lock Receiver (RCDLR) - Transmission Control Module (TCM) Correction Important DO NOT replace the control module, wiring or component for the following conditions: - The condition is intermittent and cannot be duplicated. - The condition is present and by disconnecting and reconnecting the connector the condition can no longer be duplicated. Use the following procedure to correct the conditions listed above. 1. Install a scan tool and perform the Diagnostic System Check - Vehicle. Retrieve and record any existing history or current DTCs from all of the control modules (refer to SI). ‹› If any DTC(s) are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). ‹› If DTCs are not set, refer to Symptoms - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). 2. When identified, use the appropriate DTC Diagnostics, Symptoms, Schematics, Component Connector End Views and Component Locator documents to locate and disconnect the affected harness connector(s) which are causing the condition. Note Fretting corrosion looks like little dark smudges on electrical terminals and appear where the actual electrical contact is being made. In less severe cases it may be unable to be seen or identified without the use of a magnifying glass. Important DO NOT apply an excessive amount of dielectric lubricant to the connectors as shown, as hydrolock may result when attempting to mate the connectors. Use ONLY a clean nylon brush that is dedicated to the repair of the conditions in this bulletin. 3. With a one-inch nylon bristle brush, apply dielectric lubricant to both the module/component side and the harness side of the affected connector(s). 4. Reconnect the affected connector(s) and wipe away any excess lubricant that may be present. 5. Attempt to duplicate the condition by using the following information: - DTC Diagnostic Procedure - Circuit/System Description - Conditions for Running the DTC - Conditions for Setting the DTC - Diagnostic Aids - Circuit/System Verification ‹› If the condition cannot be duplicated, the repair is complete. ‹› If the condition can be duplicated, then follow the appropriate DTC, Symptom or Circuit/System Testing procedure (refer to SI). Repair Order Documentation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Relays and Modules - Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > Customer Interest for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 11122 Important The following information MUST be documented on the repair order. Failure to do so may result in a chargeback. - Customer vehicle condition. - Was a Service Lamp or Service Message illuminated? If yes, specify which Service Lamp or Service Message. - Was a DTC(s) set? If yes, specify which DTC(s) were set. - After following the procedure contained within this bulletin, could the condition be duplicated? ‹› If the condition was not duplicated, then document the affected module/component connector name and number on the repair order. - If the condition was duplicated after the procedure contained within this bulletin was followed, and additional diagnosis led to the replacement of a module or component, the SI Document ID Number MUST be written on the repair order. Parts Information Alternate Distributor For All of North America Note NyoGel(R) 760G Lubricant* is equivalent to GMSPO P/N 12377900, and P/N 10953529 (Canada), specified for use to correct the condition in this bulletin. *We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for, or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Relays and Modules - Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > Customer Interest for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 11123 For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to refer to the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Relays and Modules - Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules Relay Module: All Technical Service Bulletins Electrical - MIL ON/DTC's Set By Various Control Modules TECHNICAL Bulletin No.: 09-06-03-004D Date: December 08, 2010 Subject: Intermittent No Crank/No Start, No Module Communication, MIL, Warning Lights, Vehicle Messages or DTCs Set by Various Control Modules - Diagnosing and Repairing Fretting Corrosion (Disconnect Affected Connector and Apply Dielectric Lubricant) Models: 2011 and Prior GM Passenger Cars and Trucks Attention: This repair can be applied to ANY electrical connection including, but not limited to: lighting, body electrical, in-line connections, powertrain control sensors, etc. DO NOT over apply lubricant to the point where it prevents the full engagement of sealed connectors. A light coating on the terminal surfaces is sufficient to correct the condition. Supercede: This bulletin is being revised to update the Attention statement and add the 2011 model year. Please discard Corporate Bulletin Number 09-06-03-004C (Section 06 Engine/Propulsion System). Condition Some customers may comment on any of the following conditions: - An intermittent no crank/no start - Intermittent malfunction indicator lamp (MIL) illumination - Intermittent service lamp illumination - Intermittent service message(s) being displayed The technician may determine that he is unable to duplicate the intermittent condition. Cause This condition may be caused by a buildup of nonconductive insulating oxidized debris known as fretting corrosion, occurring between two electrical contact surfaces of the connection or connector. This may be caused by any of the following conditions: - Vibration - Thermal cycling - Poor connection/terminal retention - Micro motion - A connector, component or wiring harness not properly secured resulting in movement On low current signal circuits this condition may cause high resistance, resulting in intermittent connections. On high current power circuits this condition may cause permanent increases in the resistance and may cause a device to become inoperative. Representative List of Control Modules and Components The following is only a representative list of control modules and components that may be affected by this connection or connector condition and DOES NOT include every possible module or component for every vehicle. - Blower Control Module - Body Control Module (BCM) - Communication Interface Module (CIM) - Cooling Fan Control Module - Electronic Brake Control Module (EBCM) - Electronic Brake and Traction Control Module (EBTCM) - Electronic Suspension Control (ESC) Module - Engine Control Module (ECM) - Heating, Ventilation and Air Conditioning (HVAC) Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Relays and Modules - Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 11129 - HVAC Actuator - Inflatable Restraint Sensing and Diagnostic Module (SDM) - Any AIR BAG module - Seatbelt Lap Anchor Pretensioner - Seatbelt Retractor Pretensioner - An SIR system connection or connector condition resulting in the following DTCs being set: B0015, B0016, B0019, B0020, B0022, or B0023 - Powertrain Control Module (PCM) - Remote Control Door Lock Receiver (RCDLR) - Transmission Control Module (TCM) Correction Important DO NOT replace the control module, wiring or component for the following conditions: - The condition is intermittent and cannot be duplicated. - The condition is present and by disconnecting and reconnecting the connector the condition can no longer be duplicated. Use the following procedure to correct the conditions listed above. 1. Install a scan tool and perform the Diagnostic System Check - Vehicle. Retrieve and record any existing history or current DTCs from all of the control modules (refer to SI). ‹› If any DTC(s) are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). ‹› If DTCs are not set, refer to Symptoms - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). 2. When identified, use the appropriate DTC Diagnostics, Symptoms, Schematics, Component Connector End Views and Component Locator documents to locate and disconnect the affected harness connector(s) which are causing the condition. Note Fretting corrosion looks like little dark smudges on electrical terminals and appear where the actual electrical contact is being made. In less severe cases it may be unable to be seen or identified without the use of a magnifying glass. Important DO NOT apply an excessive amount of dielectric lubricant to the connectors as shown, as hydrolock may result when attempting to mate the connectors. Use ONLY a clean nylon brush that is dedicated to the repair of the conditions in this bulletin. 3. With a one-inch nylon bristle brush, apply dielectric lubricant to both the module/component side and the harness side of the affected connector(s). 4. Reconnect the affected connector(s) and wipe away any excess lubricant that may be present. 5. Attempt to duplicate the condition by using the following information: - DTC Diagnostic Procedure - Circuit/System Description - Conditions for Running the DTC - Conditions for Setting the DTC - Diagnostic Aids - Circuit/System Verification ‹› If the condition cannot be duplicated, the repair is complete. ‹› If the condition can be duplicated, then follow the appropriate DTC, Symptom or Circuit/System Testing procedure (refer to SI). Repair Order Documentation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Relays and Modules - Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 11130 Important The following information MUST be documented on the repair order. Failure to do so may result in a chargeback. - Customer vehicle condition. - Was a Service Lamp or Service Message illuminated? If yes, specify which Service Lamp or Service Message. - Was a DTC(s) set? If yes, specify which DTC(s) were set. - After following the procedure contained within this bulletin, could the condition be duplicated? ‹› If the condition was not duplicated, then document the affected module/component connector name and number on the repair order. - If the condition was duplicated after the procedure contained within this bulletin was followed, and additional diagnosis led to the replacement of a module or component, the SI Document ID Number MUST be written on the repair order. Parts Information Alternate Distributor For All of North America Note NyoGel(R) 760G Lubricant* is equivalent to GMSPO P/N 12377900, and P/N 10953529 (Canada), specified for use to correct the condition in this bulletin. *We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for, or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Relays and Modules - Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 11131 For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to refer to the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > Customer Interest for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules Relay Module: Customer Interest Electrical - MIL ON/DTC's Set By Various Control Modules TECHNICAL Bulletin No.: 09-06-03-004D Date: December 08, 2010 Subject: Intermittent No Crank/No Start, No Module Communication, MIL, Warning Lights, Vehicle Messages or DTCs Set by Various Control Modules - Diagnosing and Repairing Fretting Corrosion (Disconnect Affected Connector and Apply Dielectric Lubricant) Models: 2011 and Prior GM Passenger Cars and Trucks Attention: This repair can be applied to ANY electrical connection including, but not limited to: lighting, body electrical, in-line connections, powertrain control sensors, etc. DO NOT over apply lubricant to the point where it prevents the full engagement of sealed connectors. A light coating on the terminal surfaces is sufficient to correct the condition. Supercede: This bulletin is being revised to update the Attention statement and add the 2011 model year. Please discard Corporate Bulletin Number 09-06-03-004C (Section 06 Engine/Propulsion System). Condition Some customers may comment on any of the following conditions: - An intermittent no crank/no start - Intermittent malfunction indicator lamp (MIL) illumination - Intermittent service lamp illumination - Intermittent service message(s) being displayed The technician may determine that he is unable to duplicate the intermittent condition. Cause This condition may be caused by a buildup of nonconductive insulating oxidized debris known as fretting corrosion, occurring between two electrical contact surfaces of the connection or connector. This may be caused by any of the following conditions: - Vibration - Thermal cycling - Poor connection/terminal retention - Micro motion - A connector, component or wiring harness not properly secured resulting in movement On low current signal circuits this condition may cause high resistance, resulting in intermittent connections. On high current power circuits this condition may cause permanent increases in the resistance and may cause a device to become inoperative. Representative List of Control Modules and Components The following is only a representative list of control modules and components that may be affected by this connection or connector condition and DOES NOT include every possible module or component for every vehicle. - Blower Control Module - Body Control Module (BCM) - Communication Interface Module (CIM) - Cooling Fan Control Module - Electronic Brake Control Module (EBCM) - Electronic Brake and Traction Control Module (EBTCM) - Electronic Suspension Control (ESC) Module - Engine Control Module (ECM) - Heating, Ventilation and Air Conditioning (HVAC) Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > Customer Interest for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 11140 - HVAC Actuator - Inflatable Restraint Sensing and Diagnostic Module (SDM) - Any AIR BAG module - Seatbelt Lap Anchor Pretensioner - Seatbelt Retractor Pretensioner - An SIR system connection or connector condition resulting in the following DTCs being set: B0015, B0016, B0019, B0020, B0022, or B0023 - Powertrain Control Module (PCM) - Remote Control Door Lock Receiver (RCDLR) - Transmission Control Module (TCM) Correction Important DO NOT replace the control module, wiring or component for the following conditions: - The condition is intermittent and cannot be duplicated. - The condition is present and by disconnecting and reconnecting the connector the condition can no longer be duplicated. Use the following procedure to correct the conditions listed above. 1. Install a scan tool and perform the Diagnostic System Check - Vehicle. Retrieve and record any existing history or current DTCs from all of the control modules (refer to SI). ‹› If any DTC(s) are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). ‹› If DTCs are not set, refer to Symptoms - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). 2. When identified, use the appropriate DTC Diagnostics, Symptoms, Schematics, Component Connector End Views and Component Locator documents to locate and disconnect the affected harness connector(s) which are causing the condition. Note Fretting corrosion looks like little dark smudges on electrical terminals and appear where the actual electrical contact is being made. In less severe cases it may be unable to be seen or identified without the use of a magnifying glass. Important DO NOT apply an excessive amount of dielectric lubricant to the connectors as shown, as hydrolock may result when attempting to mate the connectors. Use ONLY a clean nylon brush that is dedicated to the repair of the conditions in this bulletin. 3. With a one-inch nylon bristle brush, apply dielectric lubricant to both the module/component side and the harness side of the affected connector(s). 4. Reconnect the affected connector(s) and wipe away any excess lubricant that may be present. 5. Attempt to duplicate the condition by using the following information: - DTC Diagnostic Procedure - Circuit/System Description - Conditions for Running the DTC - Conditions for Setting the DTC - Diagnostic Aids - Circuit/System Verification ‹› If the condition cannot be duplicated, the repair is complete. ‹› If the condition can be duplicated, then follow the appropriate DTC, Symptom or Circuit/System Testing procedure (refer to SI). Repair Order Documentation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > Customer Interest for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 11141 Important The following information MUST be documented on the repair order. Failure to do so may result in a chargeback. - Customer vehicle condition. - Was a Service Lamp or Service Message illuminated? If yes, specify which Service Lamp or Service Message. - Was a DTC(s) set? If yes, specify which DTC(s) were set. - After following the procedure contained within this bulletin, could the condition be duplicated? ‹› If the condition was not duplicated, then document the affected module/component connector name and number on the repair order. - If the condition was duplicated after the procedure contained within this bulletin was followed, and additional diagnosis led to the replacement of a module or component, the SI Document ID Number MUST be written on the repair order. Parts Information Alternate Distributor For All of North America Note NyoGel(R) 760G Lubricant* is equivalent to GMSPO P/N 12377900, and P/N 10953529 (Canada), specified for use to correct the condition in this bulletin. *We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for, or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > Customer Interest for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical - MIL ON/DTC's Set By Various Control Modules > Page 11142 For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to refer to the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical MIL ON/DTC's Set By Various Control Modules Relay Module: All Technical Service Bulletins Electrical - MIL ON/DTC's Set By Various Control Modules TECHNICAL Bulletin No.: 09-06-03-004D Date: December 08, 2010 Subject: Intermittent No Crank/No Start, No Module Communication, MIL, Warning Lights, Vehicle Messages or DTCs Set by Various Control Modules - Diagnosing and Repairing Fretting Corrosion (Disconnect Affected Connector and Apply Dielectric Lubricant) Models: 2011 and Prior GM Passenger Cars and Trucks Attention: This repair can be applied to ANY electrical connection including, but not limited to: lighting, body electrical, in-line connections, powertrain control sensors, etc. DO NOT over apply lubricant to the point where it prevents the full engagement of sealed connectors. A light coating on the terminal surfaces is sufficient to correct the condition. Supercede: This bulletin is being revised to update the Attention statement and add the 2011 model year. Please discard Corporate Bulletin Number 09-06-03-004C (Section 06 Engine/Propulsion System). Condition Some customers may comment on any of the following conditions: - An intermittent no crank/no start - Intermittent malfunction indicator lamp (MIL) illumination - Intermittent service lamp illumination - Intermittent service message(s) being displayed The technician may determine that he is unable to duplicate the intermittent condition. Cause This condition may be caused by a buildup of nonconductive insulating oxidized debris known as fretting corrosion, occurring between two electrical contact surfaces of the connection or connector. This may be caused by any of the following conditions: - Vibration - Thermal cycling - Poor connection/terminal retention - Micro motion - A connector, component or wiring harness not properly secured resulting in movement On low current signal circuits this condition may cause high resistance, resulting in intermittent connections. On high current power circuits this condition may cause permanent increases in the resistance and may cause a device to become inoperative. Representative List of Control Modules and Components The following is only a representative list of control modules and components that may be affected by this connection or connector condition and DOES NOT include every possible module or component for every vehicle. - Blower Control Module - Body Control Module (BCM) - Communication Interface Module (CIM) - Cooling Fan Control Module - Electronic Brake Control Module (EBCM) - Electronic Brake and Traction Control Module (EBTCM) - Electronic Suspension Control (ESC) Module - Engine Control Module (ECM) - Heating, Ventilation and Air Conditioning (HVAC) Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical MIL ON/DTC's Set By Various Control Modules > Page 11148 - HVAC Actuator - Inflatable Restraint Sensing and Diagnostic Module (SDM) - Any AIR BAG module - Seatbelt Lap Anchor Pretensioner - Seatbelt Retractor Pretensioner - An SIR system connection or connector condition resulting in the following DTCs being set: B0015, B0016, B0019, B0020, B0022, or B0023 - Powertrain Control Module (PCM) - Remote Control Door Lock Receiver (RCDLR) - Transmission Control Module (TCM) Correction Important DO NOT replace the control module, wiring or component for the following conditions: - The condition is intermittent and cannot be duplicated. - The condition is present and by disconnecting and reconnecting the connector the condition can no longer be duplicated. Use the following procedure to correct the conditions listed above. 1. Install a scan tool and perform the Diagnostic System Check - Vehicle. Retrieve and record any existing history or current DTCs from all of the control modules (refer to SI). ‹› If any DTC(s) are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). ‹› If DTCs are not set, refer to Symptoms - Vehicle to identify the connector(s) of the control module/component which may be causing the condition (refer to SI). 2. When identified, use the appropriate DTC Diagnostics, Symptoms, Schematics, Component Connector End Views and Component Locator documents to locate and disconnect the affected harness connector(s) which are causing the condition. Note Fretting corrosion looks like little dark smudges on electrical terminals and appear where the actual electrical contact is being made. In less severe cases it may be unable to be seen or identified without the use of a magnifying glass. Important DO NOT apply an excessive amount of dielectric lubricant to the connectors as shown, as hydrolock may result when attempting to mate the connectors. Use ONLY a clean nylon brush that is dedicated to the repair of the conditions in this bulletin. 3. With a one-inch nylon bristle brush, apply dielectric lubricant to both the module/component side and the harness side of the affected connector(s). 4. Reconnect the affected connector(s) and wipe away any excess lubricant that may be present. 5. Attempt to duplicate the condition by using the following information: - DTC Diagnostic Procedure - Circuit/System Description - Conditions for Running the DTC - Conditions for Setting the DTC - Diagnostic Aids - Circuit/System Verification ‹› If the condition cannot be duplicated, the repair is complete. ‹› If the condition can be duplicated, then follow the appropriate DTC, Symptom or Circuit/System Testing procedure (refer to SI). Repair Order Documentation Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical MIL ON/DTC's Set By Various Control Modules > Page 11149 Important The following information MUST be documented on the repair order. Failure to do so may result in a chargeback. - Customer vehicle condition. - Was a Service Lamp or Service Message illuminated? If yes, specify which Service Lamp or Service Message. - Was a DTC(s) set? If yes, specify which DTC(s) were set. - After following the procedure contained within this bulletin, could the condition be duplicated? ‹› If the condition was not duplicated, then document the affected module/component connector name and number on the repair order. - If the condition was duplicated after the procedure contained within this bulletin was followed, and additional diagnosis led to the replacement of a module or component, the SI Document ID Number MUST be written on the repair order. Parts Information Alternate Distributor For All of North America Note NyoGel(R) 760G Lubricant* is equivalent to GMSPO P/N 12377900, and P/N 10953529 (Canada), specified for use to correct the condition in this bulletin. *We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for, or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources. Warranty Information (excluding Saab Models) For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to: Warranty Information (Saab Models) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Accessories and Optional Equipment > Relay Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Relay Module: > 09-06-03-004D > Dec > 10 > Electrical MIL ON/DTC's Set By Various Control Modules > Page 11150 For vehicles repaired under warranty, use the appropriate/closest labor operation depending upon the module/component connection that the dielectric lubricant was applied to refer to the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Bumper > Front Bumper > Front Bumper Cover / Fascia > System Information > Technical Service Bulletins > Body - TPO Fascia Cleaning Prior to Painting Front Bumper Cover / Fascia: Technical Service Bulletins Body - TPO Fascia Cleaning Prior to Painting INFORMATION Bulletin No.: 08-08-51-002 Date: March 12, 2008 Subject: New Primer For TPO Fascias and Affected Cleaning Process of Painting Operation Models: 2009 and Prior Passenger Cars and Trucks 2009 and Prior HUMMER H2, H3 The purpose of this bulletin is to inform the technician that General Motors has made a change in the primer it uses for TPO plastic for service parts. This new primer comes in several different colors from five different suppliers. This change affects the cleaning process of the painting operation. The new process is as follows. 1. Wash with soap and water. 2. Clean with a 50% mix of isopropyl alcohol and water (or a waterborne cleaner). Check with your paint supplier for product recommendations. 3. Scuff sand per your paint suppliers recommendations. Note: The use of a solvent-type cleaner will soften, or begin to dissolve the primer. Base coats do not have any affect on this primer. 4. Reclean with a 50% mix of isopropyl alcohol and water (or a waterborne cleaner). All fascias, with the exception of the Corvette, Camaro, and Cadillac XLR, are made of TPO. You may find other TPO parts with this primer. If the technician has a question as to the type of plastic they are painting, inspect the back of the part for the plastic symbol (TPO). Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Bumper > Front Bumper > Front Bumper Reinforcement > System Information > Technical Service Bulletins > Body - Polypropylene Energy Absorber Replacement Front Bumper Reinforcement: Technical Service Bulletins Body - Polypropylene Energy Absorber Replacement Bulletin No.: 07-08-63-001 Date: April 17, 2007 INFORMATION Subject: Information on Repair of Polypropylene Energy Absorbers Models: 2007 and Prior GM Passenger Cars and Trucks (including Saturn) 2007 and Prior HUMMER H2, H3 2005-2007 Saab 9-7X Supercede: This bulletin is being revised to change the repair information. Please discard Corporate Bulletin Number 63-20-02 (Section 8 - Body and Accessories). Because the energy absorbers are relatively low in cost to replace, it is now more cost efficient to replace the energy absorbers whenever they are damaged. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Bumper > Rear Bumper > Rear Bumper Cover / Fascia > System Information > Technical Service Bulletins > Body - TPO Fascia Cleaning Prior to Painting Rear Bumper Cover / Fascia: Technical Service Bulletins Body - TPO Fascia Cleaning Prior to Painting INFORMATION Bulletin No.: 08-08-51-002 Date: March 12, 2008 Subject: New Primer For TPO Fascias and Affected Cleaning Process of Painting Operation Models: 2009 and Prior Passenger Cars and Trucks 2009 and Prior HUMMER H2, H3 The purpose of this bulletin is to inform the technician that General Motors has made a change in the primer it uses for TPO plastic for service parts. This new primer comes in several different colors from five different suppliers. This change affects the cleaning process of the painting operation. The new process is as follows. 1. Wash with soap and water. 2. Clean with a 50% mix of isopropyl alcohol and water (or a waterborne cleaner). Check with your paint supplier for product recommendations. 3. Scuff sand per your paint suppliers recommendations. Note: The use of a solvent-type cleaner will soften, or begin to dissolve the primer. Base coats do not have any affect on this primer. 4. Reclean with a 50% mix of isopropyl alcohol and water (or a waterborne cleaner). All fascias, with the exception of the Corvette, Camaro, and Cadillac XLR, are made of TPO. You may find other TPO parts with this primer. If the technician has a question as to the type of plastic they are painting, inspect the back of the part for the plastic symbol (TPO). Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Bumper > Rear Bumper > Rear Bumper Reinforcement > System Information > Technical Service Bulletins > Body - Polypropylene Energy Absorber Replacement Rear Bumper Reinforcement: Technical Service Bulletins Body - Polypropylene Energy Absorber Replacement Bulletin No.: 07-08-63-001 Date: April 17, 2007 INFORMATION Subject: Information on Repair of Polypropylene Energy Absorbers Models: 2007 and Prior GM Passenger Cars and Trucks (including Saturn) 2007 and Prior HUMMER H2, H3 2005-2007 Saab 9-7X Supercede: This bulletin is being revised to change the repair information. Please discard Corporate Bulletin Number 63-20-02 (Section 8 - Body and Accessories). Because the energy absorbers are relatively low in cost to replace, it is now more cost efficient to replace the energy absorbers whenever they are damaged. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Doors > Front Door > Front Door Panel > System Information > Service and Repair > Door Trim Panel Replacement Front Door Panel: Service and Repair Door Trim Panel Replacement Front Door Trim Panel Front Door Trim Panel Courtesy Lamp Tool Required: J 38778 Trim Panel Remover. Remove or Disconnect 1. Door handle bezel. Refer to Inside Handle Bezel. 2. Window regulator handle (if equipped). Refer to Window Regulator Handle. 3. Power accessory mounting panel wiring connector (if equipped with power accessories). Refer to Door Power Accessory Mounting Panel. 4. Trim Panel Upper Extension. Refer to Trim Panel Upper Extension. 5. Trim panel armrest screws. Carefully pry off trim panel armrest screw cover with a flat blade tool to access screw. 6. Trim panel from the door. Carefully pry the retainers from their seats using J 38778. Disconnect courtesy light connector (if equipped). 7. Courtesy Lamp lens or reflector. 8. Retainers from trim panel. Pull retainers from slot. Install or Connect 1. Retainers to trim panel. Push retainer from slot. 2. Courtesy lamp lens or reflector. 3. Trim panel to the door. Align retainers with holes in door. Carefully apply pressure to seat retainers. 4. Window regulator handle (if equipped). Refer to Window Regulator Handle. 5. Power accessory switch mounting panel (if equipped with power accessories). 6. Trim panel arm rest screw. Tighten: Trim panel armrest screw to 1.9 Nm (17 lbs. in.). Insert screw cover. 7. Trim Panel Upper Extension. 8. Door handle bezel. Refer to Inside Handle Bezel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Doors > Front Door > Front Door Panel > System Information > Service and Repair > Door Trim Panel Replacement > Page 11178 Front Door Panel: Service and Repair Trim Panel Upper Extension Trim Panel Upper Extension Remove or Disconnect Tool Required: J 38778 Trim Panel Remover. 1. Trim panel from the door. Carefully pry the retainer from door using J 38778. Pull upward to release extension from trim panel. 2. Retainer from extension. Install or Connect 1. Retainer to extension. 2. Extension to door. Insert extension on to trim panel. Align retainer into hole in door. Push extension until retainer seats. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Doors > Front Door > Front Door Window Glass > System Information > Technical Service Bulletins > Body - Vehicle Glass Distortion Information Front Door Window Glass: Technical Service Bulletins Body - Vehicle Glass Distortion Information INFORMATION Bulletin No.: 00-08-48-005D Date: September 10, 2010 Subject: Distortion in Outer Surface of Vehicle Glass Models: 2011 and Prior GM Passenger Cars and Trucks 2009 and Prior HUMMER H2 2010 and Prior HUMMER H3 2005-2009 Saab 9-7X 2010 and Prior Saturn Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 00-08-48-005C (Section 08 - Body and Accessories). Distortion in the outer surface of the windshield glass, door glass or backlite glass may appear after the vehicle has: - Accumulated some mileage. - Been frequently washed in automatic car washes, particularly "touchless" car washes. This distortion may look like a subtle orange peel pattern, or may look like a drip or sag etched into the surface of the glass. Some car wash solutions contain a buffered solution of hydrofluoric acid which is used to clean the glass. This should not cause a problem if used in the correct concentration. However, if not used correctly, hydrofluoric acid will attack the glass, and over time, will cause visual distortion in the outer surface of the glass which cannot be removed by scraping or polishing. If this condition is suspected, look at the area of the windshield under the wipers or below the belt seal on the side glass. The area of the glass below the wipers or belt seal will not be affected and what looks like a drip or sag may be apparent at the edge of the wiper or belt seal. You may also see a line on the glass where the wiper blade or the belt seal contacts the glass. Important The repair will require replacing the affected glass and is not a result of a defect in material or workmanship. Therefore, is not covered by New Vehicle Warranty. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Doors > Front Door > Front Door Window Glass > System Information > Technical Service Bulletins > Body - Vehicle Glass Distortion Information > Page 11183 Front Door Window Glass: Technical Service Bulletins Body - Side Window Chipping Information INFORMATION Bulletin No.: 06-08-64-001B Date: October 20, 2009 Subject: Information on Side Door Window Glass Chipping Caused by Hanging Vehicle Key Lock Box Models: 2010 and Prior Passenger Cars and Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add vehicles and model years and to include all types of door window glass. Please discard Corporate Bulletin Number 06-08-64-001A (Section 08 - Body & Accessories). - In several warranty parts review cases, side door window glass was observed with a chip or chips on the top side of the window glass. Dealer contacts confirmed that they use a vehicle key lock box on the front side door window glass. - A random selection of side door glass returns will be conducted to confirm adherence. If a side door glass is discovered with a chip or chips in the location previously described, the side door glass will be returned to the dealership for debit. Example of Side Door Glass - DO NOT place a vehicle key lock box on a side door window glass. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Doors > Front Door > Front Door Window Glass > System Information > Technical Service Bulletins > Body - Vehicle Glass Distortion Information > Page 11184 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Doors > Rear Door > Rear Door Panel > System Information > Service and Repair > Main Panel Rear Door Panel: Service and Repair Main Panel Typical Rear Door Trim Panel Tool Required: J 38778 Trim Panel Remover. Remove or Disconnect 1. Door handle bezel. Refer to Inside Handle Bezel. 2. Window regulator handle (if equipped). Refer to Window Regulator Handle. 3. Speaker grill and speaker (if equipped). 4. Trim panel armrest screws. 5. Trim panel from the door. ^ Carefully pry the retainers from their seats using J 38778. ^ Disconnect courtesy light connector (if equipped). ^ Disconnect power window switch (if equipped). ^ Disconnect speaker wiring (if equipped). 6. Retainers from trim panel. 7. Courtesy lamp lens. Refer to Courtesy Lamp. 8. Power window switch (if equipped). Refer to Power Window Switch. Install or Connect 1. Retainers to trim panel. 2. Power window switch (if equipped). Refer to Power Window Switch. 3. Courtesy Lamp lens or reflector to trim panel. 4. Speaker and speaker grill(if equipped). 5. Trim panel to the door. ^ Connect speaker and power window switch connectors (if equipped). ^ Connect Courtesy lamp connector. ^ Align retainers with holes in door. ^ Carefully apply pressure to seat retainers. 6. Window regulator handle (it equipped). Refer to Window Regulator Handle. 7. Trim panel arm rest screws. Tighten: Trim panel armrest screws to 1.9 Nm (17 lbs. in.). 8. Door handle bezel. Refer to Inside Handle Bezel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Doors > Rear Door > Rear Door Panel > System Information > Service and Repair > Main Panel > Page 11190 Rear Door Panel: Service and Repair Rear Door Trim Inner Mounting Panel Front Door Inner Mounting Panel Assembly Lock Rods And Actuator Inner Mounting Panel And Window Sash Lower Window Remove or Disconnect 1. Trim panel. Refer to Trim Panel. 2. Water deflector. Refer to Inner Panel Water Deflector. 3. Speaker (if equiped). Carefully pry out retainer clips. 4. Inner panel bolts. 5. Lock rods from lock handle, lock lever, and lock rod guides. 6. Lock rods from actuator (If equipped). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Doors > Rear Door > Rear Door Panel > System Information > Service and Repair > Main Panel > Page 11191 7. Wiring harness. 8. Inner mounting panel from window sash. Slide inner mounting panel rearward to release regulator roller from window sash. Install or Connect 1. Inner mounting panel to window sash. Slide inner mounting panel forward to release regulator roller from window sash. 2. Wiring harness. 3. Lock rods to actuator (If equipped). 4. Lock rods to lock handle, lock lever, and lock rod guides. 5. Inner panel bolts. 6. Speaker (if equipped). 7. Trim panel. Refer to Trim Panel. Carefully pry out retainer clips. 8. Water deflector. Refer to Inner Panel Water Deflector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Hood > Component Information > Technical Service Bulletins > Customer Interest for Hood: > 661505 > Mar > 96 > Hood - Lower Edge of Hood Wrap Flange Contacts Grille Hood: Customer Interest Hood - Lower Edge of Hood Wrap Flange Contacts Grille File In Section: 10 - Body Bulletin No.: 66-15-05 Date: March, 1996 Subject: Hood to Grille Contact (Install Paint Protection Film) Models: 1988-96 Chevrolet and GMC C/K Models Condition Some customers may comment that the lower edge of the hood wrap flange contacts the top edge of the grille resulting in marring of the hood and/or grille. Cause Due to normal variation in the manufacturing process, the high spots on the hood wrap flange, and/or the top of the grille, may exhibit signs of marring if hood to grille contact has occurred. Correction Install 3M SCOTCHCAL film on the lower edge of the hood wrap flange. Service Procedure Important: This procedure must be done with the hood at normal shop temperature. Do not install the tape when the hood is very hot or cold. 1. Flatten any high spots of the hood wrap flange with a wooden or hard rubber mallet. The hood wrap flange should be as close to parallel to top surface of the grille as possible, as shown in Figure 1. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Hood > Component Information > Technical Service Bulletins > Customer Interest for Hood: > 661505 > Mar > 96 > Hood - Lower Edge of Hood Wrap Flange Contacts Grille > Page 11200 2. Ensure that the hood wrap flange is smooth with no spot welds or slag protruding. Utilize a small die grinder to eliminate any protrusions and touch up paint if necessary. 3. Clean the hood wrap flange surface with 3M General Purpose Adhesive Cleaner # 8984 or equivalent. 4. Following the application instructions provided with the 3M SCOTCHCAL film, apply a strip of film, beginning from the left front edge of the hood wrap flange to the center of the hood, as shown in Figure 1, Item 1. Make sure the 3M SCOTCHCAL film extends beyond the rear edge of the hood wrap flange 2-3 mm as shown in Figure 1, Item 2. Important: Minimize stretching the 3M SCOTCHCAL film as it is being applied. 5. Repeat step 4 on the right front edge of the hood wrap flange to the center of the hood. 6. Trim the 3M SCOTCHCAL film at the center and outboard edges of the hood as necessary to eliminate any excess. 7. Check the hood leveling bumpers for quality by turning upward two revolutions. Replace the bumpers if the threads of the bumpers are distorted and adjust as necessary. Parts Information 3M SCOTCHCAL film material can be obtained through your local 3M distributor (see your local Yellow Pages phone directory) by requesting Paint Protection Film, part # 84701. The roll of film is enough to service five vehicles. Warranty Information For vehicles repaired under warranty, use: Labor Labor Operation Description Time B1536 Hood to Grille Contact 0.3 hr Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Hood > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Hood: > 661505 > Mar > 96 > Hood - Lower Edge of Hood Wrap Flange Contacts Grille Hood: All Technical Service Bulletins Hood - Lower Edge of Hood Wrap Flange Contacts Grille File In Section: 10 - Body Bulletin No.: 66-15-05 Date: March, 1996 Subject: Hood to Grille Contact (Install Paint Protection Film) Models: 1988-96 Chevrolet and GMC C/K Models Condition Some customers may comment that the lower edge of the hood wrap flange contacts the top edge of the grille resulting in marring of the hood and/or grille. Cause Due to normal variation in the manufacturing process, the high spots on the hood wrap flange, and/or the top of the grille, may exhibit signs of marring if hood to grille contact has occurred. Correction Install 3M SCOTCHCAL film on the lower edge of the hood wrap flange. Service Procedure Important: This procedure must be done with the hood at normal shop temperature. Do not install the tape when the hood is very hot or cold. 1. Flatten any high spots of the hood wrap flange with a wooden or hard rubber mallet. The hood wrap flange should be as close to parallel to top surface of the grille as possible, as shown in Figure 1. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Hood > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Hood: > 661505 > Mar > 96 > Hood - Lower Edge of Hood Wrap Flange Contacts Grille > Page 11206 2. Ensure that the hood wrap flange is smooth with no spot welds or slag protruding. Utilize a small die grinder to eliminate any protrusions and touch up paint if necessary. 3. Clean the hood wrap flange surface with 3M General Purpose Adhesive Cleaner # 8984 or equivalent. 4. Following the application instructions provided with the 3M SCOTCHCAL film, apply a strip of film, beginning from the left front edge of the hood wrap flange to the center of the hood, as shown in Figure 1, Item 1. Make sure the 3M SCOTCHCAL film extends beyond the rear edge of the hood wrap flange 2-3 mm as shown in Figure 1, Item 2. Important: Minimize stretching the 3M SCOTCHCAL film as it is being applied. 5. Repeat step 4 on the right front edge of the hood wrap flange to the center of the hood. 6. Trim the 3M SCOTCHCAL film at the center and outboard edges of the hood as necessary to eliminate any excess. 7. Check the hood leveling bumpers for quality by turning upward two revolutions. Replace the bumpers if the threads of the bumpers are distorted and adjust as necessary. Parts Information 3M SCOTCHCAL film material can be obtained through your local 3M distributor (see your local Yellow Pages phone directory) by requesting Paint Protection Film, part # 84701. The roll of film is enough to service five vehicles. Warranty Information For vehicles repaired under warranty, use: Labor Labor Operation Description Time B1536 Hood to Grille Contact 0.3 hr Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Trunk / Liftgate > Power Trunk / Liftgate Lock Actuator > Component Information > Technical Service Bulletins > Customer Interest for Power Trunk / Liftgate Lock Actuator: > 66-90-03 > Jun > 97 > Keyless Entry - Unintended Release of Rear Hatch Power Trunk / Liftgate Lock Actuator: Customer Interest Keyless Entry - Unintended Release of Rear Hatch File In Section: 9 - Accessories Bulletin No.: 66-90-03 Date: June, 1997 Subject: Unintended Release of Rear Hatch (Replace Transmitter Cover) Models: 1994-96 Chevrolet and GMC C/K, S/T, M/L, G Models 1994 Oldsmobile Bravada 1996 Oldsmobile Bravada Condition An owner may report that the Rear Hatch Releases without their being aware of it. Cause The Keyless Entry Transmitter Button is unintentionally bumped activating the hatch release. Correction Replace the Keyless Entry Transmitter Cover. The revised cover has a deeper recess around the release button making it less prone to inadvertent bumping. Parts Information P/N Description Qty 15740707 Bezel, Transmitter Cover 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time R4490 Control Assembly 0.3 hr Cover - Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Trunk / Liftgate > Power Trunk / Liftgate Lock Actuator > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Power Trunk / Liftgate Lock Actuator: > 66-90-03 > Jun > 97 > Keyless Entry - Unintended Release of Rear Hatch Power Trunk / Liftgate Lock Actuator: All Technical Service Bulletins Keyless Entry - Unintended Release of Rear Hatch File In Section: 9 - Accessories Bulletin No.: 66-90-03 Date: June, 1997 Subject: Unintended Release of Rear Hatch (Replace Transmitter Cover) Models: 1994-96 Chevrolet and GMC C/K, S/T, M/L, G Models 1994 Oldsmobile Bravada 1996 Oldsmobile Bravada Condition An owner may report that the Rear Hatch Releases without their being aware of it. Cause The Keyless Entry Transmitter Button is unintentionally bumped activating the hatch release. Correction Replace the Keyless Entry Transmitter Cover. The revised cover has a deeper recess around the release button making it less prone to inadvertent bumping. Parts Information P/N Description Qty 15740707 Bezel, Transmitter Cover 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time R4490 Control Assembly 0.3 hr Cover - Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Trunk / Liftgate > Trunk / Liftgate Hinge > Component Information > Technical Service Bulletins > Customer Interest for Trunk / Liftgate Hinge: > 76-15-10 > Apr > 97 > Endgate - Broken Rear Cargo Door Hinge Technical Service Bulletin # 76-15-10 Date: 970401 Endgate - Broken Rear Cargo Door Hinge File In Section: 10 - Body Bulletin No.: 76-15-10 Date: April, 1997 Subject: Broken Rear Cargo Door Hinge (Install Replacement Hinge) Models: 1992-97 Chevrolet and GMC C/K Suburban and Utility Models with Rear Cargo Doors (RPO ZW9) Condition The door side of the hinge may fracture as a result of lack of lubrication, corrosion, or attempts to remove the hinge pin without following the procedure outlined in GM Service Bulletin No. 36-10-14A. The cargo door hinges are welded on in production. Correction A bolt on door side of the hinge is now available for service through GMSPO. There are no plans to release the body side of the hinge for service due to feasibility of installation of that side of the hinge. Parts Information Hinge Pins and Bushings are multi-packaged by GMSPO. Parts quantity listed will complete this operation on both rear cargo doors. Warranty Information For vehicles repaired under warranty, use the table. Service Procedure 1. If you are involved with this procedure, you have a damaged door side of the hinge and it will be necessary to separate the door from the body side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Trunk / Liftgate > Trunk / Liftgate Hinge > Component Information > Technical Service Bulletins > Customer Interest for Trunk / Liftgate Hinge: > 76-15-10 > Apr > 97 > Endgate - Broken Rear Cargo Door Hinge > Page 11229 of the damaged hinge. Cut the hinge pin into three sections using a 1/32" cut off wheel on a die grinder. The two cuts should be made between the hinge pin bushings in the center ear of the body side of the hinge and the top and bottom ears of the door side of the hinge. Notice: Care should be taken not to damage the center ear (body side) of the hinge because it is not serviceable. 2. The remaining hinge pin on the undamaged hinge should be removed using the procedure outlined in GM Service Bulletin No. 36-10-14A. Notice: Failure to follow the procedure outlined in GM Service Bulletin 36-10-14A may result in damage to the hinge. 3. Once the door is removed from the vehicle, the hinge pin must be removed from the center ear of the damaged hinge. Utilize the drills included with Kent Moore tool # J 41226 to drill out the hinge pin and bushings. Center punch the center of the hinge pin and then use J 41226-11 (small drill), J 41226-12 (medium drill), and J 41226-10 (large drill) to drill out the pin and bushings. Care should be taken not to damage the center ear of the hinge. 4. Install new hinge pin bushings as illustrated in view A of Figure 1. 5. Remove the lower interior trim panel from the door. 6. Locate the factory welds by using 400 grit sand paper and the service hinge backing plate as a sanding block. Lightly sand that attaching face of the hinge until the puddles of the spot welds become visible. Use a center punch to mark these locations for future reference. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Trunk / Liftgate > Trunk / Liftgate Hinge > Component Information > Technical Service Bulletins > Customer Interest for Trunk / Liftgate Hinge: > 76-15-10 > Apr > 97 > Endgate - Broken Rear Cargo Door Hinge > Page 11230 7. Cut out the appropriate template (see Figure 2) and position it on the hinge as indicated. Center punch the location points of the bolt on fasteners. 8. Drill the center points of the bolt on fasteners using a 1/8 inch (3 mm) drill. Drill completely through the hinge, inner door panel sheet metal, and the interior hinge reinforcement sheet metal for future reference. 9. Drill the center points of the spot weld locations using a 1/8 inch (3 mm) drill only as deep as the hinge material thickness. Do not drill these holes through the inner door panel sheet metal. 10. Drill the center points of the spot welds using a 1/2 inch (13 mm) drill. It will be necessary to drill until the tip of the drill penetrates the door sheet metal to allow a full 1/2 inch (13 mm) diameter of material to be removed from the hinge. 11. Use a chisel to separate the hinge from the door if necessary. Care should be taken to minimize damage to the door. 12. Drill the bolt on fastener locations identified in step 8 using a 1/2 inch (13 mm) drill through the inner door sheet metal and hinge reinforcement sheet metal. 13. Prepare the door surface to insure the hinge area is flat and free of burrs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Trunk / Liftgate > Trunk / Liftgate Hinge > Component Information > Technical Service Bulletins > Customer Interest for Trunk / Liftgate Hinge: > 76-15-10 > Apr > 97 > Endgate - Broken Rear Cargo Door Hinge > Page 11231 14. Coat the mating surface of the hinge with a medium body sealer. 15. Attach the hinge to the door using the bolts and backing plate provided in the service hinge kit (see Figure 3). Snug the tour fastener bolts, but do not tighten at this point. 16. Install the door on the body by tapping in the new hinge pins in three fourths of their total length to hold the door in position. 17. Align the door as necessary. 18. Tighten the hinge fastener bolts to 25 N.m (18 lb ft). 19. Install J 41226-4 protective template to the upper hinge. 20. Install J 41226-1 drill fixture with J 41226-3 large bushing onto the hinge assembly and position the lower screw into the hinge and tighten the screw to secure the fixture. Important: J 41226-1 fixture and J 41226-3 bushing will act as a guide to finish installation of the hinge pins when using J 41226-21 and an air driver hammer. 21. Using the air hammer and J 41226-21, install the hinge pin until the hinge pin bottoms on the upper hinge body. 22. Repeat steps 19 through 21 on the lower hinge. 23. Verity final fit and adjust if necessary. 24. Clean off any excessive body sealer applied in step 14. Refinish the hinge using the paint system utilized at your dealership. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Trunk / Liftgate > Trunk / Liftgate Hinge > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Trunk / Liftgate Hinge: > 76-15-10 > Apr > 97 > Endgate - Broken Rear Cargo Door Hinge Technical Service Bulletin # 76-15-10 Date: 970401 Endgate - Broken Rear Cargo Door Hinge File In Section: 10 - Body Bulletin No.: 76-15-10 Date: April, 1997 Subject: Broken Rear Cargo Door Hinge (Install Replacement Hinge) Models: 1992-97 Chevrolet and GMC C/K Suburban and Utility Models with Rear Cargo Doors (RPO ZW9) Condition The door side of the hinge may fracture as a result of lack of lubrication, corrosion, or attempts to remove the hinge pin without following the procedure outlined in GM Service Bulletin No. 36-10-14A. The cargo door hinges are welded on in production. Correction A bolt on door side of the hinge is now available for service through GMSPO. There are no plans to release the body side of the hinge for service due to feasibility of installation of that side of the hinge. Parts Information Hinge Pins and Bushings are multi-packaged by GMSPO. Parts quantity listed will complete this operation on both rear cargo doors. Warranty Information For vehicles repaired under warranty, use the table. Service Procedure 1. If you are involved with this procedure, you have a damaged door side of the hinge and it will be necessary to separate the door from the body side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Trunk / Liftgate > Trunk / Liftgate Hinge > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Trunk / Liftgate Hinge: > 76-15-10 > Apr > 97 > Endgate - Broken Rear Cargo Door Hinge > Page 11237 of the damaged hinge. Cut the hinge pin into three sections using a 1/32" cut off wheel on a die grinder. The two cuts should be made between the hinge pin bushings in the center ear of the body side of the hinge and the top and bottom ears of the door side of the hinge. Notice: Care should be taken not to damage the center ear (body side) of the hinge because it is not serviceable. 2. The remaining hinge pin on the undamaged hinge should be removed using the procedure outlined in GM Service Bulletin No. 36-10-14A. Notice: Failure to follow the procedure outlined in GM Service Bulletin 36-10-14A may result in damage to the hinge. 3. Once the door is removed from the vehicle, the hinge pin must be removed from the center ear of the damaged hinge. Utilize the drills included with Kent Moore tool # J 41226 to drill out the hinge pin and bushings. Center punch the center of the hinge pin and then use J 41226-11 (small drill), J 41226-12 (medium drill), and J 41226-10 (large drill) to drill out the pin and bushings. Care should be taken not to damage the center ear of the hinge. 4. Install new hinge pin bushings as illustrated in view A of Figure 1. 5. Remove the lower interior trim panel from the door. 6. Locate the factory welds by using 400 grit sand paper and the service hinge backing plate as a sanding block. Lightly sand that attaching face of the hinge until the puddles of the spot welds become visible. Use a center punch to mark these locations for future reference. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Trunk / Liftgate > Trunk / Liftgate Hinge > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Trunk / Liftgate Hinge: > 76-15-10 > Apr > 97 > Endgate - Broken Rear Cargo Door Hinge > Page 11238 7. Cut out the appropriate template (see Figure 2) and position it on the hinge as indicated. Center punch the location points of the bolt on fasteners. 8. Drill the center points of the bolt on fasteners using a 1/8 inch (3 mm) drill. Drill completely through the hinge, inner door panel sheet metal, and the interior hinge reinforcement sheet metal for future reference. 9. Drill the center points of the spot weld locations using a 1/8 inch (3 mm) drill only as deep as the hinge material thickness. Do not drill these holes through the inner door panel sheet metal. 10. Drill the center points of the spot welds using a 1/2 inch (13 mm) drill. It will be necessary to drill until the tip of the drill penetrates the door sheet metal to allow a full 1/2 inch (13 mm) diameter of material to be removed from the hinge. 11. Use a chisel to separate the hinge from the door if necessary. Care should be taken to minimize damage to the door. 12. Drill the bolt on fastener locations identified in step 8 using a 1/2 inch (13 mm) drill through the inner door sheet metal and hinge reinforcement sheet metal. 13. Prepare the door surface to insure the hinge area is flat and free of burrs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Trunk / Liftgate > Trunk / Liftgate Hinge > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Trunk / Liftgate Hinge: > 76-15-10 > Apr > 97 > Endgate - Broken Rear Cargo Door Hinge > Page 11239 14. Coat the mating surface of the hinge with a medium body sealer. 15. Attach the hinge to the door using the bolts and backing plate provided in the service hinge kit (see Figure 3). Snug the tour fastener bolts, but do not tighten at this point. 16. Install the door on the body by tapping in the new hinge pins in three fourths of their total length to hold the door in position. 17. Align the door as necessary. 18. Tighten the hinge fastener bolts to 25 N.m (18 lb ft). 19. Install J 41226-4 protective template to the upper hinge. 20. Install J 41226-1 drill fixture with J 41226-3 large bushing onto the hinge assembly and position the lower screw into the hinge and tighten the screw to secure the fixture. Important: J 41226-1 fixture and J 41226-3 bushing will act as a guide to finish installation of the hinge pins when using J 41226-21 and an air driver hammer. 21. Using the air hammer and J 41226-21, install the hinge pin until the hinge pin bottoms on the upper hinge body. 22. Repeat steps 19 through 21 on the lower hinge. 23. Verity final fit and adjust if necessary. 24. Clean off any excessive body sealer applied in step 14. Refinish the hinge using the paint system utilized at your dealership. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Trunk / Liftgate > Trunk / Liftgate Motor > Component Information > Locations Liftgate Release Motor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Trunk / Liftgate > Trunk / Liftgate Switch > Component Information > Locations > Luggage Compartment Latch Switch Trunk / Liftgate Switch: Locations Luggage Compartment Latch Switch LH side of I/P Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Doors, Hood and Trunk > Trunk / Liftgate > Trunk / Liftgate Switch > Component Information > Locations > Luggage Compartment Latch Switch > Page 11247 Trunk / Liftgate Switch: Locations Rear Glass Release Switch LH side of I/P Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Exterior Moulding / Trim > Body Emblem > Component Information > Technical Service Bulletins > 06-08-111-004B - BULLETIN CANCELLATION NOTIFICATION Body Emblem: Technical Service Bulletins 06-08-111-004B - BULLETIN CANCELLATION NOTIFICATION TECHNICAL Bulletin No.: 06-08-111-004B Date: September 25, 2009 Subject: Information on Discoloration, Blistering, Peeling or Erosion of Various Exterior Emblems Including Chevy Bowtie (Bulletin Cancelled) Models: 2009 and Prior GM Passenger Cars and Trucks (including Saturn) 2003-2009 HUMMER H2 2006-2009 HUMMER H3 2005-2009 Saab 9-7X Supercede: This bulletin is being cancelled. Please discard Corporate Bulletin Number 06-08-111-004A (Section 08 - Body & Accessories). This bulletin is being cancelled. The information is no longer applicable. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Fender > Component Information > Technical Service Bulletins > Customer Interest for Fender: > 661509A > Apr > 97 > Fiber Glass Rear Fender Paint - Star Shaped Crack Fender: Customer Interest Fiber Glass Rear Fender Paint - Star Shaped Crack File In Section: 10 - Body Bulletin No.: 66-15-09A Date: April, 1997 Subject: Fiber Glass Rear Fender Paint Star Shaped Cracks (Install Protective Liner) Models: 1988-97 Chevrolet and GMC C/K Models with RPO E62 or R05 This bulletin is being revised to add 1997 models. Please discard Corporate Bulletin Number 66-15-09 (Section 10 - Body) Condition Some customers may report star shaped cracks in the paint on fiber glass rear fenders. Cause Star shaped cracks in the paint finish are caused by the impact of rocks flung out of the tire treads against the inside of the fiber glass fender. Correction Install protective fender liner. The liner is a special polymer layer with an aluminum foil backing that is applied to the inside of the fenders. Service Procedure The inner fender must be clean, dry, and the temperature must be above 45°F. Power washing may be necessary. Any after market undercoating must be removed. Caution: To prevent cuts and abrasions on your hands from sharp aluminum foil edges, gloves should be worn during this service procedure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Fender > Component Information > Technical Service Bulletins > Customer Interest for Fender: > 661509A > Apr > 97 > Fiber Glass Rear Fender Paint - Star Shaped Crack > Page 11261 1. Attach the inboard center section of the liner to the inboard center section of the fender first. Remove a small section of the protective wax paper on the inboard center section of the liner to expose the adhesive layer of the fender liner. Using moderate pressure, apply the top fender liner to the inside top of the fender as illustrated (Figure 1). Carefully peel the wax paper from the center of the liner toward the front and rear of the fender attaching the liner as you go. Repeat this process to the opposite fender. 2. Apply the rear fender liner to the inside rear of the fender as illustrated (Figure 1). Take care to overlap the rear liner on the top liner as illustrated. Repeat this process to the opposite fender. 3. Apply moderate pressure to the entire surface of the fender liners to insure good adhesion to the inside of the fenders. Parts Information Part quantity reflects the number required to do both fenders on one vehicle. P/N Description Qty 15741040 Protector-rear 2 fender upper 15741041 Protector-rear 2 fender rear Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time B8340 Install fender liner, 0.3 hr right side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Fender > Component Information > Technical Service Bulletins > Customer Interest for Fender: > 661509A > Apr > 97 > Fiber Glass Rear Fender Paint - Star Shaped Crack > Page 11262 B8341 Install fender liner, 0.3 hr left side B8342 Install fender liner, 0.5 hr both sides Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Fender > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fender: > 661509A > Apr > 97 > Fiber Glass Rear Fender Paint - Star Shaped Crack Fender: All Technical Service Bulletins Fiber Glass Rear Fender Paint - Star Shaped Crack File In Section: 10 - Body Bulletin No.: 66-15-09A Date: April, 1997 Subject: Fiber Glass Rear Fender Paint Star Shaped Cracks (Install Protective Liner) Models: 1988-97 Chevrolet and GMC C/K Models with RPO E62 or R05 This bulletin is being revised to add 1997 models. Please discard Corporate Bulletin Number 66-15-09 (Section 10 - Body) Condition Some customers may report star shaped cracks in the paint on fiber glass rear fenders. Cause Star shaped cracks in the paint finish are caused by the impact of rocks flung out of the tire treads against the inside of the fiber glass fender. Correction Install protective fender liner. The liner is a special polymer layer with an aluminum foil backing that is applied to the inside of the fenders. Service Procedure The inner fender must be clean, dry, and the temperature must be above 45°F. Power washing may be necessary. Any after market undercoating must be removed. Caution: To prevent cuts and abrasions on your hands from sharp aluminum foil edges, gloves should be worn during this service procedure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Fender > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fender: > 661509A > Apr > 97 > Fiber Glass Rear Fender Paint - Star Shaped Crack > Page 11268 1. Attach the inboard center section of the liner to the inboard center section of the fender first. Remove a small section of the protective wax paper on the inboard center section of the liner to expose the adhesive layer of the fender liner. Using moderate pressure, apply the top fender liner to the inside top of the fender as illustrated (Figure 1). Carefully peel the wax paper from the center of the liner toward the front and rear of the fender attaching the liner as you go. Repeat this process to the opposite fender. 2. Apply the rear fender liner to the inside rear of the fender as illustrated (Figure 1). Take care to overlap the rear liner on the top liner as illustrated. Repeat this process to the opposite fender. 3. Apply moderate pressure to the entire surface of the fender liners to insure good adhesion to the inside of the fenders. Parts Information Part quantity reflects the number required to do both fenders on one vehicle. P/N Description Qty 15741040 Protector-rear 2 fender upper 15741041 Protector-rear 2 fender rear Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time B8340 Install fender liner, 0.3 hr right side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Fender > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fender: > 661509A > Apr > 97 > Fiber Glass Rear Fender Paint - Star Shaped Crack > Page 11269 B8341 Install fender liner, 0.3 hr left side B8342 Install fender liner, 0.5 hr both sides Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Frame > Component Information > Technical Service Bulletins > Body Squeeze Type Resistance Spot Welding/Equipment Frame: Technical Service Bulletins Body - Squeeze Type Resistance Spot Welding/Equipment INFORMATION Bulletin No.: 03-08-98-002B Date: June 30, 2010 Subject: Squeeze Type Resistance Spot Welding/Equipment Models: 2011 and Prior Passenger Cars and Trucks (Including Saturn) 2003-2010 HUMMER H2, H3 Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 03-08-98-002A (Section 08 - Body and Accessories). This bulletin provides guidelines for repair shops that wish to use squeeze type resistance spot welding (or simply, spot welding) as an alternative to MIG plug welding when performing collision repair procedures. The process of spot welding for attaching body panels and components has been around for many years and is similar to the production welding process used in assembly plants. Spot welding may be applicable in similar situations that are currently MIG plug welded. The following are some of the benefits of spot welding: - Less heat or burn damage - Less damage to corrosion protection - Drilling of holes not required - Replication of the production weld appearance Applicable components for this technology may be panels or components with flanges that are accessible with arms and tips supplied by the equipment manufacturer. Welds from this equipment should be applied on a one-for-one basis, next to the production welds. Here are some of the important factors in proper welding with this equipment. Important Proper use and safety training for each user of the equipment is a must. - Use equipment from companies that are able to produce welds that meet industry standards for size and strength. Equipment most likely to meet those standards at this time would be "inverter" technology and include the following suppliers (other suppliers may have comparable equipment): - Pro Spot (PR2000) - Elektron (M100) - Blackhawk (WEL700) - Car-O-Liner (CR500) For specific information about this and other equipment, call GM Dealer Equipment. - Ensure that the building power source is capable of meeting the equipment manufacturer's power requirement specifications. For example, fuse 60 amp, 208-230 V single or 3-phase, using supply wire of sufficient gauge to carry the current load. Consult with a qualified electrician for wiring assistance. - Prepare and perform sample welds for destructive testing made from similar materials. Perform this operation for each vehicle repaired and prior to actual repair. - Proper equipment maintenance - Proper weld tip alignment and maintenance - Ensure that metal flanges are clean and conform to each other A more complete description of these practices and standards can be found in the following publications: - SAE J-2667, Surface Vehicles Recommended Practice, http://www.sae.org - AWS D8.7-88, Recommended Practices Automotive Weld Quality - Resistance Spot Welding, http://www.aws.org/w/a/ - AWS D8.9-97, Recommended Practices for Test Methods for Evaluating the Resistance Spot Welding Behavior of Automotive Sheet Steels, http://www.aws.com Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Frame > Component Information > Technical Service Bulletins > Body Squeeze Type Resistance Spot Welding/Equipment > Page 11274 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Interior Moulding / Trim > Carpet > Component Information > Technical Service Bulletins > Interior - Proper Use of Floor Mats Carpet: Technical Service Bulletins Interior - Proper Use of Floor Mats INFORMATION Bulletin No.: 10-08-110-001 Date: March 30, 2010 Subject: Information on Proper Use of Floor Mats Models: 2011 and Prior GM Passenger Cars and Trucks (Including Saturn) 2003-2009 HUMMER H2 2006-2010 HUMMER H3, H3T 2005-2009 Saab 9-7X GM's carpeted and all-weather (rubber) floor mats are especially designed for use in specific GM vehicles. Using floor mats that were not designed for the specific vehicle or using them incorrectly may cause interference with the accelerator or brake pedal. Please review the following safety guidelines regarding proper driver's side floor mat usage with the customer. Warning If a floor mat is the wrong size or is not properly installed, it can interfere with the accelerator pedal and/or brake pedal. Interference with the pedals can cause unintended acceleration and/or increased stopping distance which can cause a crash and injury. Make sure the floor mat does not interfere with the accelerator or brake pedal. - Do not flip the driver's floor mat over (in an effort to keep the floor mat clean) - Do not place anything on top of the driver's floor mat (e.g. carpet remnant, towel) - Do not place another mat on top of the driver's floor mat (e.g. do not place all-weather rubber mats over carpeted floor mats) - Only use floor mats that are designed specifically for your vehicle - When using replacement mats, make certain the mats do not interfere with the accelerator or brake pedal before driving the vehicle If your vehicle is equipped with a floor mat retaining pin(s) or clip(s), make certain the mat is installed correctly and according to the instructions. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Interior Moulding / Trim > Carpet > Component Information > Technical Service Bulletins > Interior - Proper Use of Floor Mats > Page 11280 After installing floor mats, make certain they cannot move and do not interfere with the accelerator or brake pedals. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Interior Moulding / Trim > Carpet > Component Information > Technical Service Bulletins > Interior - Proper Use of Floor Mats > Page 11281 Carpet: Technical Service Bulletins Interior - Elimination Of Unwanted Odors INFORMATION Bulletin No.: 00-00-89-027E Date: September 29, 2008 Subject: Eliminating Unwanted Odors in Vehicles Models: 2009 and Prior GM Passenger Cars and Trucks (including Saturn) 2009 and Prior HUMMER H2, H3 Vehicles 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add model years and refine the instructions. Please discard Corporate Bulletin Number 00-00-89-027D (Section 00 - General Information). Vehicle Odor Elimination General Motors offers a product that may control or eliminate odors in the interior and luggage compartment areas of GM vehicles. GM Vehicle Care Odor Eliminator is a non-toxic, biodegradable odor remover. This odorless product has been shown to greatly reduce or remove objectionable smells of mold and mildew resulting from vehicle water leaks (as well as customer created odors, i.e. smoke). You may use GM Vehicle Care Odor Eliminator on fabrics, vinyl, leather, carpet and sound deadening materials. It may also be induced into HVAC modules and instrument panel ducts (for the control of non-bacterial related odors). Important: This product leaves no residual scent and should not be sold as or considered an air freshener. Product action may result in the permanent elimination of an odor and may be preferable to customers with allergies who are sensitive to perfumes. How to Use This Product GM Vehicle Care Odor Eliminator may be sprayed on in a ready-to-use formula or used in steam cleaners as an additive with carpet shampoo. This water-based, odorless product is safe for all vehicle interiors. Do not wet or soak any interior surface that plain water would cause to deteriorate, as this product will have the same effect. Also avoid letting this product come into contact with vinegar or any acidic substance. Acid-based products will hamper the effectiveness of, or render GM Vehicle Care Odor Eliminator inert. Note: Complete eight page treatment sheets are enclosed within each case of GM Vehicle Care Odor Eliminator. These treatment instructions range from simple vehicle odor elimination to full step by step procedures for odor removal from water leaks. If lost, contact 800-977-4145 to get a replacement set faxed or e-mailed to your dealership. Instructions and cautions are printed on the bottle, but additional help is available. If you encounter a difficult to eliminate or reoccurring odor, you may call 1-800-955-8591 (in Canada, 1-800-977-4145) to obtain additional information and usage suggestions. Important: This product may effectively remove odors when directly contacting the odor source. It should be used in conjunction with diagnostic procedures (in cases such as a water leak) to first eliminate the root cause of the odor, and then the residual odor to permanently correct the vehicle condition. Vehicle Waterleak Odor Elimination STEP ONE: Confirm that all water leaks have been repaired. Determine what areas of the vehicle were water soaked or wet. Components with visible mold/mildew staining should be replaced. Isolate the odor source inside the vehicle. Often an odor can be isolated to an area or component of the vehicle interior by careful evaluation. Odor evaluation may need to be performed by multiple persons. Another method of isolating an odor source is to remove and segregate interior trim and components. Plastic sheeting or drop cloths can be used to confine seats, headliners, etc. to assist in evaluation and diagnoses. If appropriate the vehicle and interior trim should be evaluated separately to determine if the odor stays with the vehicle or the interior components. Odors that stay with the vehicle may be isolated to insulating and sound deadening materials (i.e. water leak at the windshield or standing water in the front foot well area caused mold/mildew to form on the bulkhead or kick panel sound deadening pads. If the interior is removed the floor pan and primed/painted surfaces should be treated with bleach/soap solution, rinsed with clean water and dried. Interior surfaces should then be treated with GM Vehicle Care Odor Eliminator product before reinstalling carpet or reassembling. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Interior Moulding / Trim > Carpet > Component Information > Technical Service Bulletins > Interior - Proper Use of Floor Mats > Page 11282 The GM Vehicle Care Odor Eliminator product is an effective odor elimination product when used properly. It must come into direct contact with the odor source. It should be used in conjunction with diagnostic procedures to first eliminate the root cause of the odor. Some procedures for use after odor root cause correction are: STEP TWO: ^ Use the trigger spray head. ^ Put a drop of dish soap the size of a quarter in the bottom of a bottle. ^ Add 8 oz. of GM Vehicle Care Odor Eliminator (1 cup) to the dish soap and top off the bottle with tap water. ^ This formula should be used on hard surfaces (dash, interior plastic molding, and floor pan) STEP THREE: The third step to neutralizing the vehicle is a light to medium treatment of all carpeting and upholstered seats with the GM Vehicle Care Odor Eliminator formula and a wide fan spray setting (at full strength) (i.e.: carpeting on the driver's side requires 4-5 triggers pulls for coverage). The headliner and trunk should be sprayed next. Lightly brushing the formula into the carpeting and upholstery is a recommended step for deep odor problems. The dash and all hard surfaces should be sprayed with dish soap/water mixture. Let stand for 1-2 minutes then wipe off the surface. STEP FOUR: (vehicle ventilation system treatment) The ventilation system is generally the last step in the treatment of the vehicle. a. Spray the GM Vehicle Care Odor Eliminator formula into all dash vents. (1-2 trigger pulls per vent). b. Start the vehicle and turn the vehicle fan on high cool (not A/C setting). c. Spray the formula (10 trigger pulls) into the outside fresh air intake vent (cowl at base of windshield) d. Enter the vehicle after 1 minute and wipe off the excess formula spurting out of the dash vents. e. Smell the air coming from the dash vents. If odors are still present, spray another 5 triggers into the cowl, wait another minute and smell the results. Once you have obtained a fresh, clean smell coming from the vents, turn the system to the A/C re-circulation setting. Roll up the windows, spray 3-5 pumps into the right lower IP area and let the vehicle run with the fan set on high for 5-7 minutes. Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. Additional Suggestions to Increase Customer Satisfaction Here are some additional ideas to benefit your dealership and to generate greater customer enthusiasm for this product. ^ Keep this product on-hand for both the Service Department and the Used Car lot. Add value to your used car trades; treat loaner and demo cars during service and at final sale to eliminate smoke, pet, and other common odors offensive to customers. Make deodorizing a vehicle part of your normal vehicle detailing service. ^ Consider including GM Vehicle Care Odor Eliminator as a give-away item with new vehicle purchases. Many dealers give away as "gifts" various cleaning supplies at time of delivery. GM Odor Eliminator is one of a few products GM offers that has as many uses in the home as in the vehicle. Customers may find this product can be used for a host of recreational activities associated with their new vehicle, such as deodorizing a boat they tow, or a camper. ^ GM Odor Eliminator and many of the GM Vehicle Care products offer you the chance to increase dealership traffic as these superior quality products cannot be purchased in stores. Many Dealerships have product displays at the parts counter. Consider additional displays in the Customer Service Lounge, the Showroom and at the Service Desk or Cashier Window. Many customers who purchase vehicles and receive regular maintenance at your dealership may never visit the parts counter, and subsequently are not exposed to the variety and value that these products offer. Parts Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Interior Moulding / Trim > Carpet > Component Information > Technical Service Bulletins > Interior - Proper Use of Floor Mats > Page 11283 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Interior Moulding / Trim > Dash Board / Instrument Panel <--> [Dashboard / Instrument Panel] > Air Bag(s) Arming and Disarming > System Information > Service and Repair > Air Bag Disarming and Arming Air Bag(s) Arming and Disarming: Service and Repair Air Bag Disarming and Arming Disabling the SIR System Fig. 1 Air Bag Two-way Connector DRIVER SIDE Many service procedures require the air bag system to be disabled to prevent accidental deployment. The air bag system can maintain sufficient voltage to cause deployment for up to 2 minutes after the ignition switch is turned off, the battery ground cable is disconnected or the DERM fuse is removed. If the inflator module is disconnected from the deployment loop by the following procedure, service can begin immediately without waiting for the 2 minute time period to elapse. 1. Turn steering wheel so that vehicle wheels are pointed straight ahead. 2. Turn ignition switch to Lock position and remove key. 3. Remove air bag fuse from fuse block. 4. Remove steering column filler panel. 5. Remove Connector Position Assurance (CPA) and disconnect yellow two-way connector at base of steering column, Fig. 1. PASSENGER SIDE 1. Remove air bag fuse from fuse block. Enabling the SIR System Driver Side 1. Turn ignition switch to LOCK and remove key. 2. Connect yellow two-way connector and install connector position assurance (CPA). 3. Install steering column filler panel. 4. Insert air bag fuse into fuse block. 5. Turn ignition switch to RUN and verify that the air bag warning lamp flashes seven times then turns off. Passenger Side 1. Turn ignition switch to LOCK and remove key. 2. Insert air bag fuse into fuse block. 3. Turn ignition switch to RUN and verify that the air bag warning lamp flashes seven times then turns off. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Interior Moulding / Trim > Dash Board / Instrument Panel <--> [Dashboard / Instrument Panel] > Air Bag(s) Arming and Disarming > System Information > Service and Repair > Air Bag Disarming and Arming > Page 11289 Air Bag(s) Arming and Disarming: Service and Repair General Service Precautions CAUTION: When performing service on or around SIR components or SIR wiring, follow the procedures listed below to temporarily disable the SIR system. Failure to follow procedures could result in possible air bag deployment, personal injury or otherwise unneeded SIR system repairs. The DERM can maintain sufficient voltage to cause a deployment for up to 2 minutes after the ignition switch is turned "OFF," the battery is disconnected, or the fuse powering the DERM is removed. Many of the service procedures require removal of the "AIR BAG" fuse, and disconnection of the inflator module from the deployment loop to avoid an accidental deployment. If the inflator module is disconnected from the deployment loop as noted in the "Disabling the SIR System" procedure that follows, service can begin immediately without waiting for the 2 minute time period to expire. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Interior Moulding / Trim > Sun Visor > Component Information > Locations Electrochromatic Inside Rearview Mirror With Compass Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Key > Component Information > Technical Service Bulletins > Locks - Key Code Security Rules and Information Key: Technical Service Bulletins Locks - Key Code Security Rules and Information INFORMATION Bulletin No.: 10-00-89-010 Date: May 27, 2010 Subject: Key Code Security Rules and Information on GM KeyCode Look-Up Application (Canada Only) Models: 2011 and Prior GM Passenger Cars and Trucks 2010 and Prior HUMMER H2, H3 2009 and Prior Saturn and Saab 2002 and Prior Isuzu Attention: This bulletin has been created to address potential issues and questions regarding KeyCode security. This bulletin should be read by all parties involved in KeyCode activity, including dealer operator, partner security coordinator, sales, service and parts departments. A copy of this bulletin should be printed and maintained in the parts department for use as a reference. Important U.S. dealers should refer to Corporate Bulletin Number 10-00-89-009. Where Are Key Codes Located? General Motors provides access to KeyCodes through three sources when a vehicle is delivered to a dealer. Vehicle KeyCodes are located on the original vehicle invoice to the dealership. There is a small white bar coded tag sent with most new vehicles that also has the key code printed on it. Dealerships should make a practice of comparing the tag's keycode numbers to the keycode listed on the invoice. Any discrepancy should be reported immediately to the GM of Canada Key Code Inquiry Desk. Remember to remove the key tag prior to showing vehicles to potential customers. The third source for Key codes is through the GM KeyCode Look-Up feature within the OEConnection D2DLink application. KeyCode Look-Up currently goes back 17 previous model years from the current model year. When a vehicle is received by the dealership, care should be taken to safeguard the original vehicle invoice and KeyCode tag provided with the vehicle. Potential customers should not have access to the invoice or this KeyCode tag prior to the sale being completed. After a sale has been completed, the KeyCode information belongs to the customer and General Motors. Tip Only the original invoice contains key code information, a re-printed invoice does not. GM KeyCode Look-Up Application for GM of Canada Dealers All dealers should review the General Motors of Canada KeyCode Look-Up Policies and Procedures (Service Policy & Procedures Manual Section 3.1.6 "Replacement of VIN plates & keys"). Please note that the KeyCode Access site is restricted. Only authorized users should be using this application. Please see your Parts Manager for site authorized users. KeyCode Look-Up currently goes back 17 years from current model year. Important notes about security: - Users may not access the system from multiple computers simultaneously. - Users may only request one KeyCode at a time. - KeyCode information will only be available on the screen for 2 minutes. - Each user is personally responsible for maintaining and protecting their password. - Never share your password with others. - User Id's are suspended after 6 consecutive failed attempts. - User Id's are disabled if not used for 90 days. - Processes must be in place for regular dealership reviews. - The Parts Manager (or assigned management) must have processes in place for employee termination or life change events. Upon termination individuals access must be turned off immediately and access should be re-evaluated upon any position changes within the dealership. - If you think your password or ID security has been breached, contact Dealer Systems Support at 1-800-265-0573. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Key > Component Information > Technical Service Bulletins > Locks - Key Code Security Rules and Information > Page 11298 Each user will be required to accept the following agreement each time the KeyCode application is used. Key Code User Agreement - Key codes are proprietary information belonging to General Motors Corporation and to the vehicle owner. - Unauthorized access to, or use of, key code information is unlawful and may subject the user to criminal and civil penalties. - This information should be treated as strictly confidential and should not be disclosed to anyone unless authorized. I will ensure that the following information is obtained prior to releasing any Key Code information: 1. Government issued picture ID (Drivers License) 2. Registration or other proof of ownership. Registration should have normal markings from the Province that issued the registration and possibly the receipt for payment recorded as well. Important - GM takes this agreement seriously. Each user must be certain of vehicle ownership before giving out key codes. - When the ownership of the vehicle is in doubt, dealership personnel should not provide the information. Key code requests should never be received via a fax or the internet and key codes should never be provided to anyone in this manner. A face to face contact with the owner of the vehicle is the expected manner that dealers will use to release a key code or as otherwise stipulated in this bulletin or other materials. - Key codes should NEVER be sent via a fax or the internet. - Each Dealership should create a permanent file to document all KeyCode Look Up transactions. Requests should be filed by VIN and in each folder retain copies of the following: - Government issued picture ID (Drivers License) - Registration or other proof of ownership. - Copy of the paid customer receipt which has the name of the employee who cut and sold the key to the customer. - Do not put yourself or your Dealership in the position of needing to "explain" a KeyCode Look Up to either GM or law enforcement officials. - Dealership Management has the ability to review all KeyCode Look-Up transactions. - Dealership KeyCode documentation must be retained for two years. Frequently Asked Questions (FAQs) for GM of Canada Dealers How do I request a KeyCode for customer owned vehicle that is not registered? Scrapped, salvaged or stored vehicles that do not have a current registration should still have the ownership verified by requesting the vehicle title, current insurance policy and / or current lien holder information from the customers financing source. If you cannot determine if the customer is the owner of the vehicle, do not provide the key code information. In these cases, a short description of the vehicle (scrapped, salvaged, etc.) and the dealership location should be kept on file. Any clarifying explanation should be entered into the comments field. How do I document a KeyCode request for a vehicle that is being repossessed? The repossessor must document ownership of the vehicle by providing a court ordered repossession order and lien-holder documents prior to providing key code information. Copies of the repossessors Drivers License and a business card should be retained by the dealership for documentation. What do I do if the registration information is locked in the vehicle? Every effort should be made to obtain complete information for each request. Each Dealership will have to decide on a case by case basis if enough information is available to verify the customer's ownership of the vehicle. Other forms of documentation include vehicle title, insurance policy, and or current lien information from the customers financing source. Dealership Management must be involved in any request without complete information. If you cannot determine if the customer is the owner of the vehicle, do not provide the key code information. Can I get a print out of the information on the screen? It is important to note that the Key Code Look Up Search Results contain sensitive and/or proprietary information. For this reason GM recommends against printing it. If the Search Results must be printed, store and/or dispose of the printed copy properly to minimize the risk of improper or illegal use. Who in the dealership has access to the KeyCode application? Dealership Parts Manager (or assigned management) will determine, and control, who is authorized to access the KeyCode Look Up application. However, we anticipate that dealership parts and service management will be the primary users of the application. The KeyCode Look Up application automatically tracks each user activity session. Information tracked by the system includes: User name, User ID, all other entered data and the date/time of access. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Key > Component Information > Technical Service Bulletins > Locks - Key Code Security Rules and Information > Page 11299 What if I input the VIN incorrectly? If an incorrect VIN is entered into the system (meaning that the system does not recognize the VIN or that the VIN has been entered incorrectly) the system will return an error message. If I am an authorized user for the KeyCode application, can I access the application from home? Yes. What if I suspect key code misuse? Your dealership should communicate the proper procedures for requesting key codes. Any suspicious activity either within the dealership or externally should be reported to Dealer Systems Support at 1-800-265-0573 or GM of Canada Key Code Inquiry Desk at 1-905-644-4892. Whose key codes can I access through the system? At this time the following Canadian vehicle codes are available through the system: Chevrolet, Cadillac, Buick, Pontiac, GMC, HUMMER (H2 and H3 only), Oldsmobile, Saturn, Saab and Isuzu (up to 2002 model year) for a maximum of 17 model years. What should I do if I enter a valid VIN and the system does not produce any key code information? Occasionally, the KeyCode Look Up application may not produce a key code for a valid VIN. This may be the result of new vehicle information not yet available. In addition, older vehicle information may have been sent to an archive status. If you do not receive a key code returned for valid VIN, you should contact GM of Canada Key Code Inquiry Desk at 1-905-644-4892. How do I access KeyCodes if the KeyCode Look-up system is down? If the KeyCode Look-up system is temporarily unavailable, you can contact the original selling dealer who may have it on file or contact GM of Canada Key Code Inquiry Desk at 1-905-644-4892. If the customer is dealing with an emergency lock-out situation, you need to have the customer contact Roadside assistance, OnStar if subscribed, or 911. What should I do if the KeyCode from the look-up system does not work on the vehicle? On occasion a dealer may encounter a KeyCode that will not work on the vehicle in question. In cases where the KeyCode won't work you will need to verify with the manufacturer of the cutting equipment that the key has been cut correctly. If the key has been cut correctly you may be able to verify the proper KeyCode was given through the original selling dealer. When unable to verify the KeyCode through the original selling dealer contact GM of Canada Key Code Inquiry Desk at 1-905-644-4892. If the key has been cut correctly and the code given does not work, the lock cylinder may have been changed. In these situations following the proper SI document for recoding a key or replacing the lock cylinder may be necessary. How long do I have to keep KeyCode Records? Dealership KeyCode documentation must be retained for two years. Can I get a KeyCode changed in the Look-Up system? Yes, KeyCodes can be changed in the Look-Up system if a lock cylinder has been changed. Contact GM of Canada Key Code Inquiry Desk at 1-905-644-4892. What information do I need before I can provide a driver of a company fleet vehicle Keys or KeyCode information? The dealership should have a copy of the individual's driver's license, proof of employment and registration. If there is any question as to the customer's employment by the fleet company, the dealer should attempt to contact the fleet company for verification. If there is not enough information to determine ownership and employment, this information should not be provided. How do I document a request from an Independent Repair facility for a KeyCode or Key? The independent must provide a copy of their driver's license, proof of employment and signed copy of the repair order for that repair facility. The repair order must include customer's name, address, VIN, city, province and license plate number. Copies of this information must be included in your dealer KeyCode file. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Key > Component Information > Technical Service Bulletins > Locks - Key Code Security Rules and Information > Page 11300 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Receiver > Component Information > Locations Keyless Entry Receiver: Locations Under center portion of instrument panel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Transmitter > Component Information > Technical Service Bulletins > Customer Interest: > 66-90-03 > Jun > 97 > Keyless Entry - Unintended Release of Rear Hatch Keyless Entry Transmitter: Customer Interest Keyless Entry - Unintended Release of Rear Hatch File In Section: 9 - Accessories Bulletin No.: 66-90-03 Date: June, 1997 Subject: Unintended Release of Rear Hatch (Replace Transmitter Cover) Models: 1994-96 Chevrolet and GMC C/K, S/T, M/L, G Models 1994 Oldsmobile Bravada 1996 Oldsmobile Bravada Condition An owner may report that the Rear Hatch Releases without their being aware of it. Cause The Keyless Entry Transmitter Button is unintentionally bumped activating the hatch release. Correction Replace the Keyless Entry Transmitter Cover. The revised cover has a deeper recess around the release button making it less prone to inadvertent bumping. Parts Information P/N Description Qty 15740707 Bezel, Transmitter Cover 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time R4490 Control Assembly 0.3 hr Cover - Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Transmitter > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Keyless Entry Transmitter: > 83-90-12 > Aug > 98 > Tools - Keyless Entry Transmitter Tester Keyless Entry Transmitter: All Technical Service Bulletins Tools - Keyless Entry Transmitter Tester File In Section: 9 - Accessories Bulletin No.: 83-90-12 Date: August, 1998 INFORMATION Subject: Essential Tool J 43241 Remote Keyless Entry and Passive Keyless Entry Transmitter Tester Models: 1990-99 Passenger Cars and Trucks with Remote Keyless Entry or Passive Keyless Entry Systems A new essential tool, J 43241 Remote Keyless Entry Transmitter Tester, has been sent to all GM Dealers. This tester can be used on all RKE and PKE systems, on past as well as current models. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Transmitter > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Keyless Entry Transmitter: > 83-90-12 > Aug > 98 > Tools - Keyless Entry Transmitter Tester > Page 11318 Important: Before using the tester and the diagnostic chart, the following two steps must be performed. 1. Verify that the keyless entry transmitter is the correct model for the vehicle remote system. An incorrect model transmitter may pass this test, but may not activate the vehicle remote system. The correct transmitter can usually be identified by part number. 2. Ensure that the transmitter is synchronized with the vehicle (if applicable). Refer to Transmitter Synchronization in the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Transmitter > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Keyless Entry Transmitter: > 66-90-03 > Jun > 97 > Keyless Entry - Unintended Release of Rear Hatch Keyless Entry Transmitter: All Technical Service Bulletins Keyless Entry - Unintended Release of Rear Hatch File In Section: 9 - Accessories Bulletin No.: 66-90-03 Date: June, 1997 Subject: Unintended Release of Rear Hatch (Replace Transmitter Cover) Models: 1994-96 Chevrolet and GMC C/K, S/T, M/L, G Models 1994 Oldsmobile Bravada 1996 Oldsmobile Bravada Condition An owner may report that the Rear Hatch Releases without their being aware of it. Cause The Keyless Entry Transmitter Button is unintentionally bumped activating the hatch release. Correction Replace the Keyless Entry Transmitter Cover. The revised cover has a deeper recess around the release button making it less prone to inadvertent bumping. Parts Information P/N Description Qty 15740707 Bezel, Transmitter Cover 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time R4490 Control Assembly 0.3 hr Cover - Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Transmitter > Component Information > Technical Service Bulletins > All Other Service Bulletins for Keyless Entry Transmitter: > 83-90-12 > Aug > 98 > Tools - Keyless Entry Transmitter Tester Keyless Entry Transmitter: All Technical Service Bulletins Tools - Keyless Entry Transmitter Tester File In Section: 9 - Accessories Bulletin No.: 83-90-12 Date: August, 1998 INFORMATION Subject: Essential Tool J 43241 Remote Keyless Entry and Passive Keyless Entry Transmitter Tester Models: 1990-99 Passenger Cars and Trucks with Remote Keyless Entry or Passive Keyless Entry Systems A new essential tool, J 43241 Remote Keyless Entry Transmitter Tester, has been sent to all GM Dealers. This tester can be used on all RKE and PKE systems, on past as well as current models. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Transmitter > Component Information > Technical Service Bulletins > All Other Service Bulletins for Keyless Entry Transmitter: > 83-90-12 > Aug > 98 > Tools - Keyless Entry Transmitter Tester > Page 11328 Important: Before using the tester and the diagnostic chart, the following two steps must be performed. 1. Verify that the keyless entry transmitter is the correct model for the vehicle remote system. An incorrect model transmitter may pass this test, but may not activate the vehicle remote system. The correct transmitter can usually be identified by part number. 2. Ensure that the transmitter is synchronized with the vehicle (if applicable). Refer to Transmitter Synchronization in the appropriate Service Manual. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Transmitter > Component Information > Locations > Component Locations Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Transmitter > Component Information > Locations > Component Locations > Page 11331 Data Link Connector (DLC) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Remote Keyless Entry <--> [Keyless Entry] > Keyless Entry Transmitter > Component Information > Locations > Page 11332 Keyless Entry Transmitter: Service and Repair Data Link Connector (DLC) 1. Ground pin G of the Data Link Connector (DLC). ^ Receiver will respond by locking and unlocking doors within 2 seconds. 2. Press any button of the first transmitter to be programmed. 3. The control module will respond by locking/unlocking doors and activating rear window release. 4. Press any button of the second transmitter to be programmed (if used). 5. The control module will respond by locking/unlocking doors and activating the rear window release. 6. Remove the ground applied to the reprogramming connector. 7. Transmitter operation is verified by locking and unlocking the doors and activating the rear window release. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Power Locks > Power Door Lock Actuator > Component Information > Locations > Cargo RH Cargo Door Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Power Locks > Power Door Lock Actuator > Component Information > Locations > Cargo > Page 11338 Front Door Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Power Locks > Power Door Lock Actuator > Component Information > Locations > Cargo > Page 11339 Rear Door Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Power Locks > Power Door Lock Relay > Component Information > Locations Power Door Lock Relay: Locations POWER DOOR LOCK RELAY Power Door Lock Relay The Power Door Lock Relay is located under the center portion of Instrument panel (I/P), near Remote Control Door Lock Receiver (RCDLR). NOTE: This relay is used only on 4 Door and 2 Door Utility, Crew Cab/Suburban. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Power Locks > Power Door Lock Relay > Component Information > Locations > Page 11343 Door Lock Relay Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Power Locks > Power Door Lock Switch > Component Information > Locations > Door Lock Switch Front Door Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Locks > Power Locks > Power Door Lock Switch > Component Information > Locations > Door Lock Switch > Page 11348 Power Door Lock Switch: Locations Door Lock Switch, Right Front On LH Door Trim Panel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Mirrors > Heated Element, Mirror > Component Information > Technical Service Bulletins > Mirrors - Heated Mirrors, Defrosting Time Heated Element: Technical Service Bulletins Mirrors - Heated Mirrors, Defrosting Time INFORMATION Bulletin No.: 08-08-64-011A Date: February 25, 2010 Subject: Information on Heated Electrochromatic Outside Rearview Mirror Performance Models: 2010 and Prior GM Passenger Cars and Light Duty Trucks (including Saturn) 2009 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to update the model years. Please discard Corporate Bulletin Number 08-08-64-011 (Section 08 - Body and Accessories). Defrosting Time/Performance Concern The electrochromatic (auto-dimming) outside rearview mirror used on the driver's side of many GM vehicles is slower to defrost than the passenger side outside rearview mirror. This is a normal condition. The glass on the driver's side electrochromatic mirror is twice as thick as the traditional glass on the passenger side mirror. The heating elements for the mirrors on both sides draw the same wattage, therefore the driver's side mirror will take approximately twice as long to defrost as the passenger mirror (approximately four minutes versus two minutes). Should a customer indicate that the driver's side heated mirror is not functioning correctly, verify it's function based upon this information prior to replacing the mirror. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Mirrors > Power Mirror Motor > Component Information > Locations > LH Outside Mirror Power Mirror Motor: Locations LH Outside Mirror On outside of LH front Door Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Mirrors > Power Mirror Motor > Component Information > Locations > LH Outside Mirror > Page 11358 Power Mirror Motor: Locations RH Outside Mirror On outside of RH front Door Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Mirrors > Power Mirror Switch > Component Information > Locations Power Mirror Switch: Locations On LH Door Trim Panel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > Customer Interest: > 05-08-51-008C > Jun > 09 > Body - Bumps or Rust Colored Spots in Paint Paint: Customer Interest Body - Bumps or Rust Colored Spots in Paint TECHNICAL Bulletin No.: 05-08-51-008C Date: June 22, 2009 Subject: Bumps or Rust Colored Spots in Paint Due to Rail or Iron Dust (Remove Rail Dust) Models: 1994-2010 GM Passenger Cars and Trucks (Including Saturn) 2003-2010 HUMMER H2 2006-2010 HUMMER H3 2005-2009 Saab 9-7X Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 05-08-51-008B (Section 08 - Body and Accessories). Condition Visible rust colored spots or bumps on a vehicle's paint surface from rail or iron dust. Cause Rail dust comes from tiny iron particles produced from the friction between train wheels and the tracks and gets deposited on the vehicle surfaces. Iron dust can get deposited on the surface if the vehicle is stored near any operation producing iron dust such as an iron ore yard. Either material can lay on top of, or become embedded in, the paint surface. Correction Because the severity of the condition varies, proper diagnosis of the damage is critical to the success of repairs. Diagnosis should be performed on horizontal surfaces (hood, roof, deck lid, pick up box, etc.) after the vehicle has been properly cleaned. There are two types of repair materials recommended to repair rail dust or iron dust: 1. GEL TYPE OXALIC ACID: - Has the characteristics of the liquid type oxalic acid but stays where you put it because of its gel consistency. 2. CLAY TYPE NON-ACID BASED: - Requires surface lubricant during use. - Has different grades available. Caution Rail dust remover (Oxalic Acid) is an acidic substance containing chemicals that will break down the iron particles embedded in the finish. When working with rail dust remover, use the necessary safety equipment, including gloves and goggles. Follow the chemical manufacturer's directions closely because it may require special handling and disposal. If, upon inspection, some particles are still present, the various chemical manufacturer's processes can be repeated. After the removal process, small pits may remain in the clearcoat and can be corrected, in most cases, with a finesse/polish operation. Procedure 1. Move the vehicle to a cool shaded area and make sure that the vehicle surfaces are cool during the removal process. DO NOT PERFORM THE REMOVAL PROCESS IN DIRECT SUNLIGHT OR ON A VEHICLE WITH HOT OR WARM BODY PANELS. 2. Wash the vehicle with soap and water. Dry it immediately and clean the affected areas with a wax and grease remover. 3. Perform the removal process according to the chemical manufacturer's directions. Once the damage has been repaired, the final step involves a polishing process. Rail Dust Remover Manufacturers Use the chemical manufacturers listed below, or equivalent: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > Customer Interest: > 05-08-51-008C > Jun > 09 > Body - Bumps or Rust Colored Spots in Paint > Page 11371 Auto Magic(R) or Clay Magic(R) products available from: Auto Wax Company, Inc. 1275 Round Table Dr. Dallas, TX 75247 (800) 826-0828 (Toll-Free) or (214) 631-4000 (Local) Fax (214) 634-1342 www.automagic.com [email protected] E038 Fallout Gel or E038E Liquid Fallout Remover II available from: Valvoline Car Brite Company 1910 South State Avenue Indianapolis, In 46203 (800) 347-2439 (Toll Free) or (317) 788-9925 (Local) Fax (317) 788-9930 www.carbrite.com [email protected] *We believe these sources and their products to be reliable. There may be additional manufacturers of such products. General Motors does not endorse, indicate any preference for or assume any responsibility for the products from these firms or for any such items which may be available from other sources. If rail dust remover is not available in your area, call one of the numbers listed above for a distributor near your location. Warranty Information (excluding Saab U.S. Models) Important Refer to the Policy & Procedures Manual, section 1.2.1.7 for detailed information regarding warranty coverage for this condition. Important In certain cases where the vehicle finish is severely damaged and the actual repair time exceeds the published time, the additional time should be submitted in the "Other Labor Hours" field. Warranty Information (Saab U.S. Models) Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > Customer Interest: > 661509A > Apr > 97 > Fiber Glass Rear Fender Paint - Star Shaped Crack Paint: Customer Interest Fiber Glass Rear Fender Paint - Star Shaped Crack File In Section: 10 - Body Bulletin No.: 66-15-09A Date: April, 1997 Subject: Fiber Glass Rear Fender Paint Star Shaped Cracks (Install Protective Liner) Models: 1988-97 Chevrolet and GMC C/K Models with RPO E62 or R05 This bulletin is being revised to add 1997 models. Please discard Corporate Bulletin Number 66-15-09 (Section 10 - Body) Condition Some customers may report star shaped cracks in the paint on fiber glass rear fenders. Cause Star shaped cracks in the paint finish are caused by the impact of rocks flung out of the tire treads against the inside of the fiber glass fender. Correction Install protective fender liner. The liner is a special polymer layer with an aluminum foil backing that is applied to the inside of the fenders. Service Procedure The inner fender must be clean, dry, and the temperature must be above 45°F. Power washing may be necessary. Any after market undercoating must be removed. Caution: To prevent cuts and abrasions on your hands from sharp aluminum foil edges, gloves should be worn during this service procedure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > Customer Interest: > 661509A > Apr > 97 > Fiber Glass Rear Fender Paint - Star Shaped Crack > Page 11376 1. Attach the inboard center section of the liner to the inboard center section of the fender first. Remove a small section of the protective wax paper on the inboard center section of the liner to expose the adhesive layer of the fender liner. Using moderate pressure, apply the top fender liner to the inside top of the fender as illustrated (Figure 1). Carefully peel the wax paper from the center of the liner toward the front and rear of the fender attaching the liner as you go. Repeat this process to the opposite fender. 2. Apply the rear fender liner to the inside rear of the fender as illustrated (Figure 1). Take care to overlap the rear liner on the top liner as illustrated. Repeat this process to the opposite fender. 3. Apply moderate pressure to the entire surface of the fender liners to insure good adhesion to the inside of the fenders. Parts Information Part quantity reflects the number required to do both fenders on one vehicle. P/N Description Qty 15741040 Protector-rear 2 fender upper 15741041 Protector-rear 2 fender rear Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time B8340 Install fender liner, 0.3 hr right side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > Customer Interest: > 661509A > Apr > 97 > Fiber Glass Rear Fender Paint - Star Shaped Crack > Page 11377 B8341 Install fender liner, 0.3 hr left side B8342 Install fender liner, 0.5 hr both sides Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Technical Service Bulletins for Paint: > 05-08-51-008C > Jun > 09 > Body - Bumps or Rust Colored Spots in Paint Paint: All Technical Service Bulletins Body - Bumps or Rust Colored Spots in Paint TECHNICAL Bulletin No.: 05-08-51-008C Date: June 22, 2009 Subject: Bumps or Rust Colored Spots in Paint Due to Rail or Iron Dust (Remove Rail Dust) Models: 1994-2010 GM Passenger Cars and Trucks (Including Saturn) 2003-2010 HUMMER H2 2006-2010 HUMMER H3 2005-2009 Saab 9-7X Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 05-08-51-008B (Section 08 - Body and Accessories). Condition Visible rust colored spots or bumps on a vehicle's paint surface from rail or iron dust. Cause Rail dust comes from tiny iron particles produced from the friction between train wheels and the tracks and gets deposited on the vehicle surfaces. Iron dust can get deposited on the surface if the vehicle is stored near any operation producing iron dust such as an iron ore yard. Either material can lay on top of, or become embedded in, the paint surface. Correction Because the severity of the condition varies, proper diagnosis of the damage is critical to the success of repairs. Diagnosis should be performed on horizontal surfaces (hood, roof, deck lid, pick up box, etc.) after the vehicle has been properly cleaned. There are two types of repair materials recommended to repair rail dust or iron dust: 1. GEL TYPE OXALIC ACID: - Has the characteristics of the liquid type oxalic acid but stays where you put it because of its gel consistency. 2. CLAY TYPE NON-ACID BASED: - Requires surface lubricant during use. - Has different grades available. Caution Rail dust remover (Oxalic Acid) is an acidic substance containing chemicals that will break down the iron particles embedded in the finish. When working with rail dust remover, use the necessary safety equipment, including gloves and goggles. Follow the chemical manufacturer's directions closely because it may require special handling and disposal. If, upon inspection, some particles are still present, the various chemical manufacturer's processes can be repeated. After the removal process, small pits may remain in the clearcoat and can be corrected, in most cases, with a finesse/polish operation. Procedure 1. Move the vehicle to a cool shaded area and make sure that the vehicle surfaces are cool during the removal process. DO NOT PERFORM THE REMOVAL PROCESS IN DIRECT SUNLIGHT OR ON A VEHICLE WITH HOT OR WARM BODY PANELS. 2. Wash the vehicle with soap and water. Dry it immediately and clean the affected areas with a wax and grease remover. 3. Perform the removal process according to the chemical manufacturer's directions. Once the damage has been repaired, the final step involves a polishing process. Rail Dust Remover Manufacturers Use the chemical manufacturers listed below, or equivalent: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Technical Service Bulletins for Paint: > 05-08-51-008C > Jun > 09 > Body - Bumps or Rust Colored Spots in Paint > Page 11383 Auto Magic(R) or Clay Magic(R) products available from: Auto Wax Company, Inc. 1275 Round Table Dr. Dallas, TX 75247 (800) 826-0828 (Toll-Free) or (214) 631-4000 (Local) Fax (214) 634-1342 www.automagic.com [email protected] E038 Fallout Gel or E038E Liquid Fallout Remover II available from: Valvoline Car Brite Company 1910 South State Avenue Indianapolis, In 46203 (800) 347-2439 (Toll Free) or (317) 788-9925 (Local) Fax (317) 788-9930 www.carbrite.com [email protected] *We believe these sources and their products to be reliable. There may be additional manufacturers of such products. General Motors does not endorse, indicate any preference for or assume any responsibility for the products from these firms or for any such items which may be available from other sources. If rail dust remover is not available in your area, call one of the numbers listed above for a distributor near your location. Warranty Information (excluding Saab U.S. Models) Important Refer to the Policy & Procedures Manual, section 1.2.1.7 for detailed information regarding warranty coverage for this condition. Important In certain cases where the vehicle finish is severely damaged and the actual repair time exceeds the published time, the additional time should be submitted in the "Other Labor Hours" field. Warranty Information (Saab U.S. Models) Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Technical Service Bulletins for Paint: > 08-08-51-002 > Mar > 08 > Body - TPO Fascia Cleaning Prior to Painting Paint: All Technical Service Bulletins Body - TPO Fascia Cleaning Prior to Painting INFORMATION Bulletin No.: 08-08-51-002 Date: March 12, 2008 Subject: New Primer For TPO Fascias and Affected Cleaning Process of Painting Operation Models: 2009 and Prior Passenger Cars and Trucks 2009 and Prior HUMMER H2, H3 The purpose of this bulletin is to inform the technician that General Motors has made a change in the primer it uses for TPO plastic for service parts. This new primer comes in several different colors from five different suppliers. This change affects the cleaning process of the painting operation. The new process is as follows. 1. Wash with soap and water. 2. Clean with a 50% mix of isopropyl alcohol and water (or a waterborne cleaner). Check with your paint supplier for product recommendations. 3. Scuff sand per your paint suppliers recommendations. Note: The use of a solvent-type cleaner will soften, or begin to dissolve the primer. Base coats do not have any affect on this primer. 4. Reclean with a 50% mix of isopropyl alcohol and water (or a waterborne cleaner). All fascias, with the exception of the Corvette, Camaro, and Cadillac XLR, are made of TPO. You may find other TPO parts with this primer. If the technician has a question as to the type of plastic they are painting, inspect the back of the part for the plastic symbol (TPO). Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Technical Service Bulletins for Paint: > 72-05-11 > Dec > 97 > Warranty - Rail Dust Removal & Chemical Spotting Labor Paint: All Technical Service Bulletins Warranty - Rail Dust Removal & Chemical Spotting Labor File In Section: Warranty Administration Bulletin No.: 72-05-11 Date: December, 1997 WARRANTY ADMINISTRATION Subject: Clarification of Rail Dust Removal (A5575-A5580) and Chemical Spotting (A5541-A5544) Labor Operations Models: All Past and Future Passenger Cars and Light Duty Trucks The purpose of this Warranty Administration Bulletin is to clarify the usage, limits and guidelines for the proper use of the above subject labor operations. The above subject labor operations were introduced to correct paint imperfections caused by fallout that occurred either during shipment to the dealer or within the first 12 months or 12,000 miles (20,000 kms) of vehicle ownership. GM vehicle owners are informed that although no defect in the factory applied paint causes this, GM will repair, at no charge to the owner, the surfaces of new vehicles damaged by fallout condition within 12 months or 12,000 miles (20,000 kms) whichever occurs first. Effective with repair orders dated on or after December 1, 1997, labor operations A5575-A5580 Rail Dust Removal and A5541 through A5544 Chemical Spotting will be limited to within the first 12 months or 12,000 miles of the Base Vehicle Warranty (20,000 kms) whichever occurs first. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Technical Service Bulletins for Paint: > 63-17-07B > Jun > 97 > Paint - Basecoat/Clearcoat Paint Systems Specifications Paint: All Technical Service Bulletins Paint - Basecoat/Clearcoat Paint Systems Specifications File In Section: 10 - Body Bulletin No.: 63-17-07B Date: June, 1997 INFORMATION Subject: New Aftermarket Paint Specification (GM4901M) for Basecoat/Clearcoat Paint Systems (Rigid Exterior Surfaces) Models: 1993-97 Passenger Cars and Trucks This bulletin is being revised to provide additional information on approved paint systems (Attachment 1 added). Please discard Corporate Bulletin Number 63-17-07A (Section 10 - Body). A vehicle's appearance is important to any customer's perception of that vehicle's quality and value. Furthermore, when an exterior finish repair is made, the customer expects that repair to match the showroom finish. Based upon rigorous and exhaustive testing, General Motors has established an aftermarket refinish paint specification, known as GM4901M, which is listed in the GM Engineering Specifications Manual. Use this specification when selecting a paint system for General Motors vehicle warranty paint repairs. All major paint suppliers are involved and support this program. The booklet enclosed with Corporate Bulletin # 63-17-07, "GM Approved Refinish Materials", P/N GM4901 M-D, identifies the paint systems you may use. All approved products (including VOC-compliant) are listed in the "system" approach recommended by the individual manufacturer. This booklet will be updated periodically to ensure you are provided with the latest information on paint systems. GM and Paint Supplier training services encompass this new specification and can address any questions. All materials listed in the booklet fall under the current materials allowance. However, this may change as costs increase. With this program, it is our goal to ensure quality repairs. After all, skilled technicians using the right materials offer the only path to true customer enthusiasm. By adhering to the GM4901M Specification for Aftermarket Paint Repair Materials, you will ensure our customers only receive the best while maximizing your quality throughout on exterior finish repairs. When a meeting or training session is held in your area, be sure your team is represented. We look forward to your support for this program. Additional Information In the development of this paint specification, major paint suppliers were invited to submit materials for approval. The requirements of the program are included in the approved materials booklet referenced above, dated December, 1996. Important: As of 7-1-97, the BASF products listed on Attachment 1 are now approved for use. The approved suppliers are: ^ Akzo Nobel (Sikkens) ^ American Standox ^ BASF ^ DuPont ^ ICI Autocolor ^ Martin Senour ^ PPG ^ Sherwin Williams Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Technical Service Bulletins for Paint: > 63-17-07B > Jun > 97 > Paint - Basecoat/Clearcoat Paint Systems Specifications > Page 11396 ^ Spies Hecker Your Zone wholesale personnel, Training Centers, STG Field Service Engineers, and the approved suppliers have additional training materials that may answer your further questions. Use of these GM approved materials ensures the highest quality for maintaining customer satisfaction. The dealer or retailer must ensure that all refinish materials, including sublets, meet GM Specification GM4901-M. Use of materials (and associated application methods) that do not meet this GM standard may result in a review of claim(s) leading to chargeback(s), as specified in the Policies and Procedures manual, Article 1.4.17. The standards will be updated periodically and other suppliers may be added when new standards are released by the fall of 1997. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Technical Service Bulletins for Paint: > 63-17-07B > Jun > 97 > Paint - Basecoat/Clearcoat Paint Systems Specifications > Page 11397 ATTACHMENT 1 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Technical Service Bulletins for Paint: > 661509A > Apr > 97 > Fiber Glass Rear Fender Paint - Star Shaped Crack Paint: All Technical Service Bulletins Fiber Glass Rear Fender Paint - Star Shaped Crack File In Section: 10 - Body Bulletin No.: 66-15-09A Date: April, 1997 Subject: Fiber Glass Rear Fender Paint Star Shaped Cracks (Install Protective Liner) Models: 1988-97 Chevrolet and GMC C/K Models with RPO E62 or R05 This bulletin is being revised to add 1997 models. Please discard Corporate Bulletin Number 66-15-09 (Section 10 - Body) Condition Some customers may report star shaped cracks in the paint on fiber glass rear fenders. Cause Star shaped cracks in the paint finish are caused by the impact of rocks flung out of the tire treads against the inside of the fiber glass fender. Correction Install protective fender liner. The liner is a special polymer layer with an aluminum foil backing that is applied to the inside of the fenders. Service Procedure The inner fender must be clean, dry, and the temperature must be above 45°F. Power washing may be necessary. Any after market undercoating must be removed. Caution: To prevent cuts and abrasions on your hands from sharp aluminum foil edges, gloves should be worn during this service procedure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Technical Service Bulletins for Paint: > 661509A > Apr > 97 > Fiber Glass Rear Fender Paint - Star Shaped Crack > Page 11402 1. Attach the inboard center section of the liner to the inboard center section of the fender first. Remove a small section of the protective wax paper on the inboard center section of the liner to expose the adhesive layer of the fender liner. Using moderate pressure, apply the top fender liner to the inside top of the fender as illustrated (Figure 1). Carefully peel the wax paper from the center of the liner toward the front and rear of the fender attaching the liner as you go. Repeat this process to the opposite fender. 2. Apply the rear fender liner to the inside rear of the fender as illustrated (Figure 1). Take care to overlap the rear liner on the top liner as illustrated. Repeat this process to the opposite fender. 3. Apply moderate pressure to the entire surface of the fender liners to insure good adhesion to the inside of the fenders. Parts Information Part quantity reflects the number required to do both fenders on one vehicle. P/N Description Qty 15741040 Protector-rear 2 fender upper 15741041 Protector-rear 2 fender rear Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time B8340 Install fender liner, 0.3 hr right side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Technical Service Bulletins for Paint: > 661509A > Apr > 97 > Fiber Glass Rear Fender Paint - Star Shaped Crack > Page 11403 B8341 Install fender liner, 0.3 hr left side B8342 Install fender liner, 0.5 hr both sides Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Technical Service Bulletins for Paint: > 631705 > May > 96 > Body/Paint - New Color Pull-Ahead Program Paint: All Technical Service Bulletins Body/Paint - New Color Pull-Ahead Program File In Section: 10 - Body Bulletin No.: 63-17-05 Date: May, 1996 INFORMATION Subject: New Color Pull-Ahead Program Models: 1996 Chevrolet and GMC Light Duty Trucks Beginning in the Spring of 1996, General Motors will implement an annual New Color Pull-Ahead program. This will encompass building the next model year's new colors on current production vehicles approximately 90 days prior to the start of regular production (SORP). In other words, in the Spring of 1996, the colors that are new for 1997 will be built on some 1996 vehicles. The purpose of the program is to assure a successful new color start up. New color WA numbers are listed below. Important: Check Spid label for verification of WA number. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Technical Service Bulletins for Paint: > 43-01-03A > Dec > 95 > Paint - Information and SPID Label Paint: All Technical Service Bulletins Paint - Information and SPID Label File In Section: 0 - General Information Bulletin No.: 43-01-03A Date: December, 1995 INFORMATION Subject: SPID Label and Paint information Models: 1995-96 Passenger Cars and Trucks This bulletin is being revised to add the 1996 model year. Please discard Corporate Bulletin Number 43-01-03 (Section 0 - General Information). The information concerns the service parts identification label (SPID) location on all 1995-96 vehicles and the paint information location on those labels. Important: There may be a label location change for the F-car (interim 1996-1/2 model year). When the interim production change occurs, the label may be located on the left door jamb. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Technical Service Bulletins for Paint: > 43-01-03A > Dec > 95 > Paint - Information and SPID Label > Page 11412 1995-96 GENERAL MOTORS Vehicle Paint Identification SERVICE PARTS IDENTIFICATION LABEL LOCATIONS Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Technical Service Bulletins for Paint: > 43-01-03A > Dec > 95 > Paint - Information and SPID Label > Page 11413 PAINT CODE EXPLANATIONS SERVICE PARTS IDENTIFICATION LABEL The Service Parts Identification Label (below) is a paper material with a protective plastic coating. It is being used to replace the metal Fisher Body plate. The label should provide the following: ^ Vehicle Identification Number (VIN) ^ "WA" Number ^ Two-Digit Paint Code ^ Paint Technology ^ Vinyl Top Color (where applicable) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Technical Service Bulletins for Paint: > 43-01-03A > Dec > 95 > Paint - Information and SPID Label > Page 11414 ^ Interior Color Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Technical Service Bulletins for Paint: > 531704 > Sep > 95 > Paint - Polishing And Swirl Mark Removal Paint: All Technical Service Bulletins Paint - Polishing And Swirl Mark Removal File in Section: 10 - Body Bulletin No. 53-17-04 Date: September, 1995 INFORMATION Subject: Polishing and Swirl Mark Removal Techniques for Basecoat/Clearcoat Paint Models: 1993-96 Passenger Cars and Trucks with Basecoat/Clearcoat This bulletin supersedes and cancels Corporate Bulletin Number 111702. Previous divisional publication numbers were: Buick 93-10-22 Cadillac T-93-104 Chevrolet 93-188-OB GM Canada 93-10-158 Oldsmobile 07-93-106 (Service Guild) Pontiac 93-10-28 Today's basecoat/clearcoat paint finishes are very different from materials used on vehicles in the 1980's. Materials, procedures and equipment which once worked well for polishing traditional finishes may not be acceptable for use on basecoat/clearcoat paint surfaces. The use of outdated materials, procedures and equipment may produce what appears to be acceptable results under shop lighting, but will be unacceptable to the owner when the finish is exposed to sunlight (typically, swirl marks). While the following information can be most helpful in the new car "prep" area, it should also be made available to the "used car" area and the collision/ paint repair area. KEEP THE VEHICLE CLEAN AND DRY; ^ Avoid washing vehicles in direct sunlight. ^ Avoid using strong soaps or chemical detergents. ^ Use "brush less" type automatic car wash equipment. ^ Avoid using products containing acids (unless specified to correct a condition such as "rail dust"). ^ Don't use brushes or brooms to remove snow or ice from vehicles in storage or on lots. ^ Cleaning agents and water should be dried promptly and not allowed to dry on the surface. ^ Standing rinse water should be dried promptly and not allowed to dry on the surface. ^ Drying with a soft chamois is recommended. DON'T CREATE A PROBLEM: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Technical Service Bulletins for Paint: > 531704 > Sep > 95 > Paint - Polishing And Swirl Mark Removal > Page 11419 ^ DO NOT polish vehicles unless a surface condition exists that can only be corrected by polishing (see chart). ^ If a surface condition does exist, the repair approach should be one of "less is best" (the very least it takes to correct the condition). ^ Avoid removing too much clearcoat (whenever possible, use paint gauges before, during, and after polishing). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Technical Service Bulletins for Paint: > 531704 > Sep > 95 > Paint - Polishing And Swirl Mark Removal > Page 11420 ^ Use ONLY the products recommended in this bulletin (or their equivalent). ^ Make sure that any power polishing equipment does not exceed the requirements in the polish manufacturer's recommendation or in the chart. FINAL STEP: The final step of the finesse/polish procedure is the removal of SWIRL MARKS. Swirl marks are defined as very fine scratches in a uniform circular direction that cause an optical distortion on the paint surface. Swirl marks may not be visible with shop lighting. They should be viewed in direct sunlight or under specific lights, i.e. Sodium Vapor (parking lot type lights). SWIRL MARK REMOVAL - To remove swirl marks, use an orbital polisher (DA) with speeds in the 1,500 to 2,000 RPM range. Apply a small amount of the appropriate material (see chart) to the swirl mark area. Use the pad on the random orbital buffer to spread the material evenly over polished area before buffing. When buffing, keep pad flat and constantly moving over the repair area. Polish with heavier pressure applied for 4-6 seconds, then polish with lighter pressure for 6-8 more seconds. Always blend or feather outer edges of repair spot. After buffing, the buffed areas should be inspected by the buffing person to ensure that the swirls are completely removed. If swirls are still present, rebuff as needed. Hand wipe the surface with a clean soft, non-scratching cloth and a 50/50 mixture of Isopropyl Alcohol and water. ^ DON'T USE WAX OR SILICONE-TYPE PRODUCTS TO HIDE SWIRL MARKS (this condition will reappear later and cause owner dissatisfaction). ^ Specific conditions on paint (environmental damage, rail dust, etc.) can be corrected by referring to previously published Service bulletins on those specific topics. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > 08-08-51-002 > Mar > 08 > Body - TPO Fascia Cleaning Prior to Painting Paint: All Technical Service Bulletins Body - TPO Fascia Cleaning Prior to Painting INFORMATION Bulletin No.: 08-08-51-002 Date: March 12, 2008 Subject: New Primer For TPO Fascias and Affected Cleaning Process of Painting Operation Models: 2009 and Prior Passenger Cars and Trucks 2009 and Prior HUMMER H2, H3 The purpose of this bulletin is to inform the technician that General Motors has made a change in the primer it uses for TPO plastic for service parts. This new primer comes in several different colors from five different suppliers. This change affects the cleaning process of the painting operation. The new process is as follows. 1. Wash with soap and water. 2. Clean with a 50% mix of isopropyl alcohol and water (or a waterborne cleaner). Check with your paint supplier for product recommendations. 3. Scuff sand per your paint suppliers recommendations. Note: The use of a solvent-type cleaner will soften, or begin to dissolve the primer. Base coats do not have any affect on this primer. 4. Reclean with a 50% mix of isopropyl alcohol and water (or a waterborne cleaner). All fascias, with the exception of the Corvette, Camaro, and Cadillac XLR, are made of TPO. You may find other TPO parts with this primer. If the technician has a question as to the type of plastic they are painting, inspect the back of the part for the plastic symbol (TPO). Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > 72-05-11 > Dec > 97 > Warranty - Rail Dust Removal & Chemical Spotting Labor Paint: All Technical Service Bulletins Warranty - Rail Dust Removal & Chemical Spotting Labor File In Section: Warranty Administration Bulletin No.: 72-05-11 Date: December, 1997 WARRANTY ADMINISTRATION Subject: Clarification of Rail Dust Removal (A5575-A5580) and Chemical Spotting (A5541-A5544) Labor Operations Models: All Past and Future Passenger Cars and Light Duty Trucks The purpose of this Warranty Administration Bulletin is to clarify the usage, limits and guidelines for the proper use of the above subject labor operations. The above subject labor operations were introduced to correct paint imperfections caused by fallout that occurred either during shipment to the dealer or within the first 12 months or 12,000 miles (20,000 kms) of vehicle ownership. GM vehicle owners are informed that although no defect in the factory applied paint causes this, GM will repair, at no charge to the owner, the surfaces of new vehicles damaged by fallout condition within 12 months or 12,000 miles (20,000 kms) whichever occurs first. Effective with repair orders dated on or after December 1, 1997, labor operations A5575-A5580 Rail Dust Removal and A5541 through A5544 Chemical Spotting will be limited to within the first 12 months or 12,000 miles of the Base Vehicle Warranty (20,000 kms) whichever occurs first. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > 63-17-07B > Jun > 97 > Paint - Basecoat/Clearcoat Paint Systems Specifications Paint: All Technical Service Bulletins Paint - Basecoat/Clearcoat Paint Systems Specifications File In Section: 10 - Body Bulletin No.: 63-17-07B Date: June, 1997 INFORMATION Subject: New Aftermarket Paint Specification (GM4901M) for Basecoat/Clearcoat Paint Systems (Rigid Exterior Surfaces) Models: 1993-97 Passenger Cars and Trucks This bulletin is being revised to provide additional information on approved paint systems (Attachment 1 added). Please discard Corporate Bulletin Number 63-17-07A (Section 10 - Body). A vehicle's appearance is important to any customer's perception of that vehicle's quality and value. Furthermore, when an exterior finish repair is made, the customer expects that repair to match the showroom finish. Based upon rigorous and exhaustive testing, General Motors has established an aftermarket refinish paint specification, known as GM4901M, which is listed in the GM Engineering Specifications Manual. Use this specification when selecting a paint system for General Motors vehicle warranty paint repairs. All major paint suppliers are involved and support this program. The booklet enclosed with Corporate Bulletin # 63-17-07, "GM Approved Refinish Materials", P/N GM4901 M-D, identifies the paint systems you may use. All approved products (including VOC-compliant) are listed in the "system" approach recommended by the individual manufacturer. This booklet will be updated periodically to ensure you are provided with the latest information on paint systems. GM and Paint Supplier training services encompass this new specification and can address any questions. All materials listed in the booklet fall under the current materials allowance. However, this may change as costs increase. With this program, it is our goal to ensure quality repairs. After all, skilled technicians using the right materials offer the only path to true customer enthusiasm. By adhering to the GM4901M Specification for Aftermarket Paint Repair Materials, you will ensure our customers only receive the best while maximizing your quality throughout on exterior finish repairs. When a meeting or training session is held in your area, be sure your team is represented. We look forward to your support for this program. Additional Information In the development of this paint specification, major paint suppliers were invited to submit materials for approval. The requirements of the program are included in the approved materials booklet referenced above, dated December, 1996. Important: As of 7-1-97, the BASF products listed on Attachment 1 are now approved for use. The approved suppliers are: ^ Akzo Nobel (Sikkens) ^ American Standox ^ BASF ^ DuPont ^ ICI Autocolor ^ Martin Senour ^ PPG ^ Sherwin Williams Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > 63-17-07B > Jun > 97 > Paint - Basecoat/Clearcoat Paint Systems Specifications > Page 11434 ^ Spies Hecker Your Zone wholesale personnel, Training Centers, STG Field Service Engineers, and the approved suppliers have additional training materials that may answer your further questions. Use of these GM approved materials ensures the highest quality for maintaining customer satisfaction. The dealer or retailer must ensure that all refinish materials, including sublets, meet GM Specification GM4901-M. Use of materials (and associated application methods) that do not meet this GM standard may result in a review of claim(s) leading to chargeback(s), as specified in the Policies and Procedures manual, Article 1.4.17. The standards will be updated periodically and other suppliers may be added when new standards are released by the fall of 1997. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > 63-17-07B > Jun > 97 > Paint - Basecoat/Clearcoat Paint Systems Specifications > Page 11435 ATTACHMENT 1 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > 631705 > May > 96 > Body/Paint - New Color Pull-Ahead Program Paint: All Technical Service Bulletins Body/Paint - New Color Pull-Ahead Program File In Section: 10 - Body Bulletin No.: 63-17-05 Date: May, 1996 INFORMATION Subject: New Color Pull-Ahead Program Models: 1996 Chevrolet and GMC Light Duty Trucks Beginning in the Spring of 1996, General Motors will implement an annual New Color Pull-Ahead program. This will encompass building the next model year's new colors on current production vehicles approximately 90 days prior to the start of regular production (SORP). In other words, in the Spring of 1996, the colors that are new for 1997 will be built on some 1996 vehicles. The purpose of the program is to assure a successful new color start up. New color WA numbers are listed below. Important: Check Spid label for verification of WA number. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > 43-01-03A > Dec > 95 > Paint - Information and SPID Label Paint: All Technical Service Bulletins Paint - Information and SPID Label File In Section: 0 - General Information Bulletin No.: 43-01-03A Date: December, 1995 INFORMATION Subject: SPID Label and Paint information Models: 1995-96 Passenger Cars and Trucks This bulletin is being revised to add the 1996 model year. Please discard Corporate Bulletin Number 43-01-03 (Section 0 - General Information). The information concerns the service parts identification label (SPID) location on all 1995-96 vehicles and the paint information location on those labels. Important: There may be a label location change for the F-car (interim 1996-1/2 model year). When the interim production change occurs, the label may be located on the left door jamb. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > 43-01-03A > Dec > 95 > Paint - Information and SPID Label > Page 11444 1995-96 GENERAL MOTORS Vehicle Paint Identification SERVICE PARTS IDENTIFICATION LABEL LOCATIONS Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > 43-01-03A > Dec > 95 > Paint - Information and SPID Label > Page 11445 PAINT CODE EXPLANATIONS SERVICE PARTS IDENTIFICATION LABEL The Service Parts Identification Label (below) is a paper material with a protective plastic coating. It is being used to replace the metal Fisher Body plate. The label should provide the following: ^ Vehicle Identification Number (VIN) ^ "WA" Number ^ Two-Digit Paint Code ^ Paint Technology ^ Vinyl Top Color (where applicable) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > 43-01-03A > Dec > 95 > Paint - Information and SPID Label > Page 11446 ^ Interior Color Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > 531704 > Sep > 95 > Paint - Polishing And Swirl Mark Removal Paint: All Technical Service Bulletins Paint - Polishing And Swirl Mark Removal File in Section: 10 - Body Bulletin No. 53-17-04 Date: September, 1995 INFORMATION Subject: Polishing and Swirl Mark Removal Techniques for Basecoat/Clearcoat Paint Models: 1993-96 Passenger Cars and Trucks with Basecoat/Clearcoat This bulletin supersedes and cancels Corporate Bulletin Number 111702. Previous divisional publication numbers were: Buick 93-10-22 Cadillac T-93-104 Chevrolet 93-188-OB GM Canada 93-10-158 Oldsmobile 07-93-106 (Service Guild) Pontiac 93-10-28 Today's basecoat/clearcoat paint finishes are very different from materials used on vehicles in the 1980's. Materials, procedures and equipment which once worked well for polishing traditional finishes may not be acceptable for use on basecoat/clearcoat paint surfaces. The use of outdated materials, procedures and equipment may produce what appears to be acceptable results under shop lighting, but will be unacceptable to the owner when the finish is exposed to sunlight (typically, swirl marks). While the following information can be most helpful in the new car "prep" area, it should also be made available to the "used car" area and the collision/ paint repair area. KEEP THE VEHICLE CLEAN AND DRY; ^ Avoid washing vehicles in direct sunlight. ^ Avoid using strong soaps or chemical detergents. ^ Use "brush less" type automatic car wash equipment. ^ Avoid using products containing acids (unless specified to correct a condition such as "rail dust"). ^ Don't use brushes or brooms to remove snow or ice from vehicles in storage or on lots. ^ Cleaning agents and water should be dried promptly and not allowed to dry on the surface. ^ Standing rinse water should be dried promptly and not allowed to dry on the surface. ^ Drying with a soft chamois is recommended. DON'T CREATE A PROBLEM: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > 531704 > Sep > 95 > Paint - Polishing And Swirl Mark Removal > Page 11451 ^ DO NOT polish vehicles unless a surface condition exists that can only be corrected by polishing (see chart). ^ If a surface condition does exist, the repair approach should be one of "less is best" (the very least it takes to correct the condition). ^ Avoid removing too much clearcoat (whenever possible, use paint gauges before, during, and after polishing). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > 531704 > Sep > 95 > Paint - Polishing And Swirl Mark Removal > Page 11452 ^ Use ONLY the products recommended in this bulletin (or their equivalent). ^ Make sure that any power polishing equipment does not exceed the requirements in the polish manufacturer's recommendation or in the chart. FINAL STEP: The final step of the finesse/polish procedure is the removal of SWIRL MARKS. Swirl marks are defined as very fine scratches in a uniform circular direction that cause an optical distortion on the paint surface. Swirl marks may not be visible with shop lighting. They should be viewed in direct sunlight or under specific lights, i.e. Sodium Vapor (parking lot type lights). SWIRL MARK REMOVAL - To remove swirl marks, use an orbital polisher (DA) with speeds in the 1,500 to 2,000 RPM range. Apply a small amount of the appropriate material (see chart) to the swirl mark area. Use the pad on the random orbital buffer to spread the material evenly over polished area before buffing. When buffing, keep pad flat and constantly moving over the repair area. Polish with heavier pressure applied for 4-6 seconds, then polish with lighter pressure for 6-8 more seconds. Always blend or feather outer edges of repair spot. After buffing, the buffed areas should be inspected by the buffing person to ensure that the swirls are completely removed. If swirls are still present, rebuff as needed. Hand wipe the surface with a clean soft, non-scratching cloth and a 50/50 mixture of Isopropyl Alcohol and water. ^ DON'T USE WAX OR SILICONE-TYPE PRODUCTS TO HIDE SWIRL MARKS (this condition will reappear later and cause owner dissatisfaction). ^ Specific conditions on paint (environmental damage, rail dust, etc.) can be corrected by referring to previously published Service bulletins on those specific topics. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > Page 11453 Paint: By Symptom Technical Service Bulletin # 05-08-51-008C Date: 090622 Body - Bumps or Rust Colored Spots in Paint TECHNICAL Bulletin No.: 05-08-51-008C Date: June 22, 2009 Subject: Bumps or Rust Colored Spots in Paint Due to Rail or Iron Dust (Remove Rail Dust) Models: 1994-2010 GM Passenger Cars and Trucks (Including Saturn) 2003-2010 HUMMER H2 2006-2010 HUMMER H3 2005-2009 Saab 9-7X Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 05-08-51-008B (Section 08 - Body and Accessories). Condition Visible rust colored spots or bumps on a vehicle's paint surface from rail or iron dust. Cause Rail dust comes from tiny iron particles produced from the friction between train wheels and the tracks and gets deposited on the vehicle surfaces. Iron dust can get deposited on the surface if the vehicle is stored near any operation producing iron dust such as an iron ore yard. Either material can lay on top of, or become embedded in, the paint surface. Correction Because the severity of the condition varies, proper diagnosis of the damage is critical to the success of repairs. Diagnosis should be performed on horizontal surfaces (hood, roof, deck lid, pick up box, etc.) after the vehicle has been properly cleaned. There are two types of repair materials recommended to repair rail dust or iron dust: 1. GEL TYPE OXALIC ACID: - Has the characteristics of the liquid type oxalic acid but stays where you put it because of its gel consistency. 2. CLAY TYPE NON-ACID BASED: - Requires surface lubricant during use. - Has different grades available. Caution Rail dust remover (Oxalic Acid) is an acidic substance containing chemicals that will break down the iron particles embedded in the finish. When working with rail dust remover, use the necessary safety equipment, including gloves and goggles. Follow the chemical manufacturer's directions closely because it may require special handling and disposal. If, upon inspection, some particles are still present, the various chemical manufacturer's processes can be repeated. After the removal process, small pits may remain in the clearcoat and can be corrected, in most cases, with a finesse/polish operation. Procedure 1. Move the vehicle to a cool shaded area and make sure that the vehicle surfaces are cool during the removal process. DO NOT PERFORM THE REMOVAL PROCESS IN DIRECT SUNLIGHT OR ON A VEHICLE WITH HOT OR WARM BODY PANELS. 2. Wash the vehicle with soap and water. Dry it immediately and clean the affected areas with a wax and grease remover. 3. Perform the removal process according to the chemical manufacturer's directions. Once the damage has been repaired, the final step involves a polishing process. Rail Dust Remover Manufacturers Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > Page 11454 Use the chemical manufacturers listed below, or equivalent: Auto Magic(R) or Clay Magic(R) products available from: Auto Wax Company, Inc. 1275 Round Table Dr. Dallas, TX 75247 (800) 826-0828 (Toll-Free) or (214) 631-4000 (Local) Fax (214) 634-1342 www.automagic.com [email protected] E038 Fallout Gel or E038E Liquid Fallout Remover II available from: Valvoline Car Brite Company 1910 South State Avenue Indianapolis, In 46203 (800) 347-2439 (Toll Free) or (317) 788-9925 (Local) Fax (317) 788-9930 www.carbrite.com [email protected] *We believe these sources and their products to be reliable. There may be additional manufacturers of such products. General Motors does not endorse, indicate any preference for or assume any responsibility for the products from these firms or for any such items which may be available from other sources. If rail dust remover is not available in your area, call one of the numbers listed above for a distributor near your location. Warranty Information (excluding Saab U.S. Models) Important Refer to the Policy & Procedures Manual, section 1.2.1.7 for detailed information regarding warranty coverage for this condition. Important In certain cases where the vehicle finish is severely damaged and the actual repair time exceeds the published time, the additional time should be submitted in the "Other Labor Hours" field. Warranty Information (Saab U.S. Models) Disclaimer Technical Service Bulletin # 661509A Date: 970401 Fiber Glass Rear Fender Paint - Star Shaped Crack Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > Page 11455 File In Section: 10 - Body Bulletin No.: 66-15-09A Date: April, 1997 Subject: Fiber Glass Rear Fender Paint Star Shaped Cracks (Install Protective Liner) Models: 1988-97 Chevrolet and GMC C/K Models with RPO E62 or R05 This bulletin is being revised to add 1997 models. Please discard Corporate Bulletin Number 66-15-09 (Section 10 - Body) Condition Some customers may report star shaped cracks in the paint on fiber glass rear fenders. Cause Star shaped cracks in the paint finish are caused by the impact of rocks flung out of the tire treads against the inside of the fiber glass fender. Correction Install protective fender liner. The liner is a special polymer layer with an aluminum foil backing that is applied to the inside of the fenders. Service Procedure The inner fender must be clean, dry, and the temperature must be above 45°F. Power washing may be necessary. Any after market undercoating must be removed. Caution: To prevent cuts and abrasions on your hands from sharp aluminum foil edges, gloves should be worn during this service procedure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > Page 11456 1. Attach the inboard center section of the liner to the inboard center section of the fender first. Remove a small section of the protective wax paper on the inboard center section of the liner to expose the adhesive layer of the fender liner. Using moderate pressure, apply the top fender liner to the inside top of the fender as illustrated (Figure 1). Carefully peel the wax paper from the center of the liner toward the front and rear of the fender attaching the liner as you go. Repeat this process to the opposite fender. 2. Apply the rear fender liner to the inside rear of the fender as illustrated (Figure 1). Take care to overlap the rear liner on the top liner as illustrated. Repeat this process to the opposite fender. 3. Apply moderate pressure to the entire surface of the fender liners to insure good adhesion to the inside of the fenders. Parts Information Part quantity reflects the number required to do both fenders on one vehicle. P/N Description Qty 15741040 Protector-rear 2 fender upper 15741041 Protector-rear 2 fender rear Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time B8340 Install fender liner, 0.3 hr right side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > Page 11457 B8341 Install fender liner, 0.3 hr left side B8342 Install fender liner, 0.5 hr both sides Technical Service Bulletin # 05-08-51-008C Date: 090622 Body - Bumps or Rust Colored Spots in Paint TECHNICAL Bulletin No.: 05-08-51-008C Date: June 22, 2009 Subject: Bumps or Rust Colored Spots in Paint Due to Rail or Iron Dust (Remove Rail Dust) Models: 1994-2010 GM Passenger Cars and Trucks (Including Saturn) 2003-2010 HUMMER H2 2006-2010 HUMMER H3 2005-2009 Saab 9-7X Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 05-08-51-008B (Section 08 - Body and Accessories). Condition Visible rust colored spots or bumps on a vehicle's paint surface from rail or iron dust. Cause Rail dust comes from tiny iron particles produced from the friction between train wheels and the tracks and gets deposited on the vehicle surfaces. Iron dust can get deposited on the surface if the vehicle is stored near any operation producing iron dust such as an iron ore yard. Either material can lay on top of, or become embedded in, the paint surface. Correction Because the severity of the condition varies, proper diagnosis of the damage is critical to the success of repairs. Diagnosis should be performed on horizontal surfaces (hood, roof, deck lid, pick up box, etc.) after the vehicle has been properly cleaned. There are two types of repair materials recommended to repair rail dust or iron dust: 1. GEL TYPE OXALIC ACID: - Has the characteristics of the liquid type oxalic acid but stays where you put it because of its gel consistency. 2. CLAY TYPE NON-ACID BASED: - Requires surface lubricant during use. - Has different grades available. Caution Rail dust remover (Oxalic Acid) is an acidic substance containing chemicals that will break down the iron particles embedded in the finish. When working with rail dust remover, use the necessary safety equipment, including gloves and goggles. Follow the chemical manufacturer's directions closely because it may require special handling and disposal. If, upon inspection, some particles are still present, the various chemical manufacturer's processes can be repeated. After the removal process, small pits may remain in the clearcoat and can be corrected, in most cases, with a finesse/polish operation. Procedure 1. Move the vehicle to a cool shaded area and make sure that the vehicle surfaces are cool during the removal process. DO NOT PERFORM THE REMOVAL PROCESS IN DIRECT SUNLIGHT OR ON A VEHICLE WITH HOT OR WARM BODY PANELS. 2. Wash the vehicle with soap and water. Dry it immediately and clean the affected areas with a wax and grease remover. 3. Perform the removal process according to the chemical manufacturer's directions. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > Page 11458 Once the damage has been repaired, the final step involves a polishing process. Rail Dust Remover Manufacturers Use the chemical manufacturers listed below, or equivalent: Auto Magic(R) or Clay Magic(R) products available from: Auto Wax Company, Inc. 1275 Round Table Dr. Dallas, TX 75247 (800) 826-0828 (Toll-Free) or (214) 631-4000 (Local) Fax (214) 634-1342 www.automagic.com [email protected] E038 Fallout Gel or E038E Liquid Fallout Remover II available from: Valvoline Car Brite Company 1910 South State Avenue Indianapolis, In 46203 (800) 347-2439 (Toll Free) or (317) 788-9925 (Local) Fax (317) 788-9930 www.carbrite.com [email protected] *We believe these sources and their products to be reliable. There may be additional manufacturers of such products. General Motors does not endorse, indicate any preference for or assume any responsibility for the products from these firms or for any such items which may be available from other sources. If rail dust remover is not available in your area, call one of the numbers listed above for a distributor near your location. Warranty Information (excluding Saab U.S. Models) Important Refer to the Policy & Procedures Manual, section 1.2.1.7 for detailed information regarding warranty coverage for this condition. Important In certain cases where the vehicle finish is severely damaged and the actual repair time exceeds the published time, the additional time should be submitted in the "Other Labor Hours" field. Warranty Information (Saab U.S. Models) Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > Page 11459 Technical Service Bulletin # 661509A Date: 970401 Fiber Glass Rear Fender Paint - Star Shaped Crack File In Section: 10 - Body Bulletin No.: 66-15-09A Date: April, 1997 Subject: Fiber Glass Rear Fender Paint Star Shaped Cracks (Install Protective Liner) Models: 1988-97 Chevrolet and GMC C/K Models with RPO E62 or R05 This bulletin is being revised to add 1997 models. Please discard Corporate Bulletin Number 66-15-09 (Section 10 - Body) Condition Some customers may report star shaped cracks in the paint on fiber glass rear fenders. Cause Star shaped cracks in the paint finish are caused by the impact of rocks flung out of the tire treads against the inside of the fiber glass fender. Correction Install protective fender liner. The liner is a special polymer layer with an aluminum foil backing that is applied to the inside of the fenders. Service Procedure The inner fender must be clean, dry, and the temperature must be above 45°F. Power washing may be necessary. Any after market undercoating must be removed. Caution: To prevent cuts and abrasions on your hands from sharp aluminum foil edges, gloves should be worn during this service procedure. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > Page 11460 1. Attach the inboard center section of the liner to the inboard center section of the fender first. Remove a small section of the protective wax paper on the inboard center section of the liner to expose the adhesive layer of the fender liner. Using moderate pressure, apply the top fender liner to the inside top of the fender as illustrated (Figure 1). Carefully peel the wax paper from the center of the liner toward the front and rear of the fender attaching the liner as you go. Repeat this process to the opposite fender. 2. Apply the rear fender liner to the inside rear of the fender as illustrated (Figure 1). Take care to overlap the rear liner on the top liner as illustrated. Repeat this process to the opposite fender. 3. Apply moderate pressure to the entire surface of the fender liners to insure good adhesion to the inside of the fenders. Parts Information Part quantity reflects the number required to do both fenders on one vehicle. P/N Description Qty 15741040 Protector-rear 2 fender upper 15741041 Protector-rear 2 fender rear Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time B8340 Install fender liner, 0.3 hr right side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Paint, Striping and Decals > Paint > System Information > Technical Service Bulletins > All Other Service Bulletins for Paint: > Page 11461 B8341 Install fender liner, 0.3 hr left side B8342 Install fender liner, 0.5 hr both sides Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Relays and Modules - Body and Frame > Power Door Lock Relay > Component Information > Locations Power Door Lock Relay: Locations POWER DOOR LOCK RELAY Power Door Lock Relay The Power Door Lock Relay is located under the center portion of Instrument panel (I/P), near Remote Control Door Lock Receiver (RCDLR). NOTE: This relay is used only on 4 Door and 2 Door Utility, Crew Cab/Suburban. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Relays and Modules - Body and Frame > Power Door Lock Relay > Component Information > Locations > Page 11466 Door Lock Relay Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Roof and Associated Components > Sun Shade > Component Information > Technical Service Bulletins > Sunshade - Replacement Availability Sun Shade: Technical Service Bulletins Sunshade - Replacement Availability File In Section: 08 - Body and Accessories Bulletin No.: 99-08-110-005 Date: June, 1999 INFORMATION Subject: Sunshade Replacement Models: 1999 and Prior Chevrolet and GMC Light Duty Trucks This bulletin is to inform dealers that new replacement sunshades are being introduced for service on approximately July 19, 1999. These new replacement sunshades will no longer have the map strap feature. The part numbers for these replacement sunshades will remain the same as the previous parts. Once these new sunshades become available, current replacement sunshades on hand may be used at the customer's/dealer's discretion. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Seats > Head Restraint System > System Information > Technical Service Bulletins > Restraints - Driver/Passenger Seat Head Rest Information Head Restraint System: Technical Service Bulletins Restraints - Driver/Passenger Seat Head Rest Information INFORMATION Bulletin No.: 10-08-50-003A Date: March 24, 2011 Subject: Information on Driver or Passenger Seat Head Restraint Concerns with Comfort, Custom Upholstery or Other Comfort Enhancing Devices Models: 2012 and Prior GM Passenger Cars and Trucks Equipped with Adjustable Head Restraints Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 10-08-50-003 (Section 08 - Body and Accessories). Important ON A GM VEHICLE EQUIPPED WITH ADJUSTABLE HEAD RESTRAINTS, USE THE HEAD RESTRAINT COVERS, FOAM AND OTHER SEAT-RELATED EQUIPMENT AS RELEASED BY GM FOR THAT VEHICLE. DO NOT ALTER OR REPOSITION THE HEAD RESTRAINT SYSTEM. ANY ALTERATIONS TO HEAD RESTRAINTS DEFEATS THE INTENDED DESIGN OF THE SYSTEM. GM WILL NOT BE LIABLE FOR ANY PROBLEMS CAUSED BY USE OF SUCH IMPROPER DESIGN ALTERATIONS, INCLUDING ANY WARRANTY REPAIRS INCURRED. You may have a customer with a concern that the head restraint is uncomfortable or sits too far forward. The front driver and passenger seats are equipped with head restraints that have been designed to help minimize injuries while still providing comfort to the occupants. Each GM vehicle has its own specifically designed head restraint. The head restraints should only be used in the vehicle for which they were designed. The head restraint will not operate to its design intent if the original foam is replaced (1) by non-GM foam or head restraint, (2) by GM foam or head restraint designed for a different vehicle, (3) by GM foam or head restraint that has been altered by a trim shop or (4) if any object, such as an aftermarket comfort enhancing pad or device, is installed. Never modify the design of the head restraint or remove the head restraint from the vehicle as this may interfere with the operation of the seating and restraint systems and may prevent proper positioning of the passenger within the vehicle. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Seats > Power Seat Motor > Component Information > Locations Power Seat Motor: Locations Under Driver's Seat Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Seats > Power Seat Motor > Component Information > Diagrams > Cross Body Harn to Power Seat, RH C240: Cross Body HARN To Power Seat, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Seats > Power Seat Motor > Component Information > Diagrams > Cross Body Harn to Power Seat, RH > Page 11482 C212: PWR Seat To Cross Body HARN, Body HARN To Cross Body HARN, Cargo Lamp SW Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Seats > Power Seat Switch > Component Information > Locations > Forward/Rearward Up and Down Switch Power Seat Switch: Locations Forward/Rearward Up and Down Switch LH rear top of Engine, above Valve Cover Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Seats > Power Seat Switch > Component Information > Locations > Forward/Rearward Up and Down Switch > Page 11487 Power Seat Switch: Locations Power Lumbar Seat Switch LH Front front Under Passenger's Seat RH Front front Under Passenger's Seat Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Seats > Power Seat Switch > Component Information > Locations > Forward/Rearward Up and Down Switch > Page 11488 Power Seat Switch: Locations Tilt Switch, Front On Seat Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Seats > Seat Cover > Component Information > Technical Service Bulletins > Interior - Seat Cover Wrinkle/Crease/Burn Info Seat Cover: Technical Service Bulletins Interior - Seat Cover Wrinkle/Crease/Burn Info INFORMATION Bulletin No.: 04-08-50-006D Date: September 09, 2010 Subject: Minor Wrinkles/Creases, Discoloration, Cigarette Burns and Customer Induced Cuts and Stains on Front and Rear Driver and Passenger Seats with Leather, Vinyl or Cloth Seat Covers Models: 2011 and Prior GM Passenger Cars and Light Duty Trucks 2009 and Prior HUMMER H2 2010 and Prior HUMMER H3 2009 and Prior Saab 9-7X 2010 and Prior Saturn Supercede: This bulletin is being revised to add a model year. Please discard Corporate Bulletin Number 04-08-50-006C (Section 08 - Body and Accessories). If a customer comes in to your dealership due to certain conditions of the seat covers (splits, wrinkles, loose stitching, etc.), you must examine the seat cover in order to determine the validity of the customer claim. Some components from the above listed vehicles have been returned to the Warranty Parts Center (WPC) and analysis of these parts showed "customer induced damage" or No Trouble Found (NTF). The dealer should pay particular attention to the following conditions: - Cigarette burns Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Seats > Seat Cover > Component Information > Technical Service Bulletins > Interior - Seat Cover Wrinkle/Crease/Burn Info > Page 11493 - Customer induced cuts (knife cuts, cut by customer tools, etc.) - Paint stains (customer should have cleaned paint stains while paint was still wet) - Coffee stains and other removable dirt These should be cleaned as described in the Owner's Manual under Appearance Care. Also, refer to Corporate Bulletin Number 06-00-89-029A or later. - Evidence of chemicals used for cleaning, other than those specified in the Owner's Manual - Other chemical spills - Minor and normal leather wrinkles as a result of use - Other defects to the seat cover not detected during the pre-delivery inspection (PDI). Inform the customer that the above issues were not present when the vehicle was purchased and cannot be replaced under warranty. The covers, however, may be repaired or replaced at the customer's expense. The following conditions are not caused by the customer and should be covered by warranty: - Split seams Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Seats > Seat Cover > Component Information > Technical Service Bulletins > Interior - Seat Cover Wrinkle/Crease/Burn Info > Page 11494 - Wear/cracking/peeling - Discoloration/dye transfer from customer clothing (if discoloration/dye transfer is not removed after using GM Leather and Vinyl Plastic Cleaner, P/N 88861401 (in Canada, P/N 88861409), replace the covers.) Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Seats > Seat Cover > Component Information > Technical Service Bulletins > Interior - Seat Cover Wrinkle/Crease/Burn Info > Page 11495 Seat Cover: Technical Service Bulletins Interior - Elimination Of Unwanted Odors INFORMATION Bulletin No.: 00-00-89-027E Date: September 29, 2008 Subject: Eliminating Unwanted Odors in Vehicles Models: 2009 and Prior GM Passenger Cars and Trucks (including Saturn) 2009 and Prior HUMMER H2, H3 Vehicles 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add model years and refine the instructions. Please discard Corporate Bulletin Number 00-00-89-027D (Section 00 - General Information). Vehicle Odor Elimination General Motors offers a product that may control or eliminate odors in the interior and luggage compartment areas of GM vehicles. GM Vehicle Care Odor Eliminator is a non-toxic, biodegradable odor remover. This odorless product has been shown to greatly reduce or remove objectionable smells of mold and mildew resulting from vehicle water leaks (as well as customer created odors, i.e. smoke). You may use GM Vehicle Care Odor Eliminator on fabrics, vinyl, leather, carpet and sound deadening materials. It may also be induced into HVAC modules and instrument panel ducts (for the control of non-bacterial related odors). Important: This product leaves no residual scent and should not be sold as or considered an air freshener. Product action may result in the permanent elimination of an odor and may be preferable to customers with allergies who are sensitive to perfumes. How to Use This Product GM Vehicle Care Odor Eliminator may be sprayed on in a ready-to-use formula or used in steam cleaners as an additive with carpet shampoo. This water-based, odorless product is safe for all vehicle interiors. Do not wet or soak any interior surface that plain water would cause to deteriorate, as this product will have the same effect. Also avoid letting this product come into contact with vinegar or any acidic substance. Acid-based products will hamper the effectiveness of, or render GM Vehicle Care Odor Eliminator inert. Note: Complete eight page treatment sheets are enclosed within each case of GM Vehicle Care Odor Eliminator. These treatment instructions range from simple vehicle odor elimination to full step by step procedures for odor removal from water leaks. If lost, contact 800-977-4145 to get a replacement set faxed or e-mailed to your dealership. Instructions and cautions are printed on the bottle, but additional help is available. If you encounter a difficult to eliminate or reoccurring odor, you may call 1-800-955-8591 (in Canada, 1-800-977-4145) to obtain additional information and usage suggestions. Important: This product may effectively remove odors when directly contacting the odor source. It should be used in conjunction with diagnostic procedures (in cases such as a water leak) to first eliminate the root cause of the odor, and then the residual odor to permanently correct the vehicle condition. Vehicle Waterleak Odor Elimination STEP ONE: Confirm that all water leaks have been repaired. Determine what areas of the vehicle were water soaked or wet. Components with visible mold/mildew staining should be replaced. Isolate the odor source inside the vehicle. Often an odor can be isolated to an area or component of the vehicle interior by careful evaluation. Odor evaluation may need to be performed by multiple persons. Another method of isolating an odor source is to remove and segregate interior trim and components. Plastic sheeting or drop cloths can be used to confine seats, headliners, etc. to assist in evaluation and diagnoses. If appropriate the vehicle and interior trim should be evaluated separately to determine if the odor stays with the vehicle or the interior components. Odors that stay with the vehicle may be isolated to insulating and sound deadening materials (i.e. water leak at the windshield or standing water in the front foot well area caused mold/mildew to form on the bulkhead or kick panel sound deadening pads. If the interior is removed the floor pan and primed/painted surfaces should be treated with bleach/soap solution, rinsed with clean water and dried. Interior surfaces should then be treated with GM Vehicle Care Odor Eliminator product before reinstalling carpet or reassembling. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Seats > Seat Cover > Component Information > Technical Service Bulletins > Interior - Seat Cover Wrinkle/Crease/Burn Info > Page 11496 The GM Vehicle Care Odor Eliminator product is an effective odor elimination product when used properly. It must come into direct contact with the odor source. It should be used in conjunction with diagnostic procedures to first eliminate the root cause of the odor. Some procedures for use after odor root cause correction are: STEP TWO: ^ Use the trigger spray head. ^ Put a drop of dish soap the size of a quarter in the bottom of a bottle. ^ Add 8 oz. of GM Vehicle Care Odor Eliminator (1 cup) to the dish soap and top off the bottle with tap water. ^ This formula should be used on hard surfaces (dash, interior plastic molding, and floor pan) STEP THREE: The third step to neutralizing the vehicle is a light to medium treatment of all carpeting and upholstered seats with the GM Vehicle Care Odor Eliminator formula and a wide fan spray setting (at full strength) (i.e.: carpeting on the driver's side requires 4-5 triggers pulls for coverage). The headliner and trunk should be sprayed next. Lightly brushing the formula into the carpeting and upholstery is a recommended step for deep odor problems. The dash and all hard surfaces should be sprayed with dish soap/water mixture. Let stand for 1-2 minutes then wipe off the surface. STEP FOUR: (vehicle ventilation system treatment) The ventilation system is generally the last step in the treatment of the vehicle. a. Spray the GM Vehicle Care Odor Eliminator formula into all dash vents. (1-2 trigger pulls per vent). b. Start the vehicle and turn the vehicle fan on high cool (not A/C setting). c. Spray the formula (10 trigger pulls) into the outside fresh air intake vent (cowl at base of windshield) d. Enter the vehicle after 1 minute and wipe off the excess formula spurting out of the dash vents. e. Smell the air coming from the dash vents. If odors are still present, spray another 5 triggers into the cowl, wait another minute and smell the results. Once you have obtained a fresh, clean smell coming from the vents, turn the system to the A/C re-circulation setting. Roll up the windows, spray 3-5 pumps into the right lower IP area and let the vehicle run with the fan set on high for 5-7 minutes. Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. Additional Suggestions to Increase Customer Satisfaction Here are some additional ideas to benefit your dealership and to generate greater customer enthusiasm for this product. ^ Keep this product on-hand for both the Service Department and the Used Car lot. Add value to your used car trades; treat loaner and demo cars during service and at final sale to eliminate smoke, pet, and other common odors offensive to customers. Make deodorizing a vehicle part of your normal vehicle detailing service. ^ Consider including GM Vehicle Care Odor Eliminator as a give-away item with new vehicle purchases. Many dealers give away as "gifts" various cleaning supplies at time of delivery. GM Odor Eliminator is one of a few products GM offers that has as many uses in the home as in the vehicle. Customers may find this product can be used for a host of recreational activities associated with their new vehicle, such as deodorizing a boat they tow, or a camper. ^ GM Odor Eliminator and many of the GM Vehicle Care products offer you the chance to increase dealership traffic as these superior quality products cannot be purchased in stores. Many Dealerships have product displays at the parts counter. Consider additional displays in the Customer Service Lounge, the Showroom and at the Service Desk or Cashier Window. Many customers who purchase vehicles and receive regular maintenance at your dealership may never visit the parts counter, and subsequently are not exposed to the variety and value that these products offer. Parts Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Seats > Seat Cover > Component Information > Technical Service Bulletins > Interior - Seat Cover Wrinkle/Crease/Burn Info > Page 11497 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Sensors and Switches - Body and Frame > Power Door Lock Switch > Component Information > Locations > Door Lock Switch Front Door Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Sensors and Switches - Body and Frame > Power Door Lock Switch > Component Information > Locations > Door Lock Switch > Page 11503 Power Door Lock Switch: Locations Door Lock Switch, Right Front On LH Door Trim Panel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Sensors and Switches - Body and Frame > Power Mirror Switch > Component Information > Locations Power Mirror Switch: Locations On LH Door Trim Panel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Sensors and Switches - Body and Frame > Power Seat Switch > Component Information > Locations > Forward/Rearward Up and Down Switch Power Seat Switch: Locations Forward/Rearward Up and Down Switch LH rear top of Engine, above Valve Cover Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Sensors and Switches - Body and Frame > Power Seat Switch > Component Information > Locations > Forward/Rearward Up and Down Switch > Page 11511 Power Seat Switch: Locations Power Lumbar Seat Switch LH Front front Under Passenger's Seat RH Front front Under Passenger's Seat Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Sensors and Switches - Body and Frame > Power Seat Switch > Component Information > Locations > Forward/Rearward Up and Down Switch > Page 11512 Power Seat Switch: Locations Tilt Switch, Front On Seat Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Sensors and Switches - Body and Frame > Trunk / Liftgate Switch > Component Information > Locations > Luggage Compartment Latch Switch Trunk / Liftgate Switch: Locations Luggage Compartment Latch Switch LH side of I/P Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Sensors and Switches - Body and Frame > Trunk / Liftgate Switch > Component Information > Locations > Luggage Compartment Latch Switch > Page 11517 Trunk / Liftgate Switch: Locations Rear Glass Release Switch LH side of I/P Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Tailgate > Component Information > Locations Tailgate: Locations Center of I/P Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Tailgate > Component Information > Locations > Page 11521 C302: Rear Body HARN To Cross Body HARN, End Gate Release Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Weatherstrip > Component Information > Technical Service Bulletins > Customer Interest: > 561505A > Mar > 96 > Front Door/A-Pillar - Wind Noise Weatherstrip: Customer Interest Front Door/A-Pillar - Wind Noise File In Section: 10 - Body Bulletin No.: 56-15-05A Date: March, 1996 Subject: Front Door/A-Pillar Wind Noise (Install Service Package) Models: 1988-95 Chevrolet and GMC C/K Models 1990-95 Topkick/Kodiak Models This bulletin is being revised to change the service procedure, change the glass sealer and adhesive used and change caption wording. Please discard Corporate Bulletin Number 56-15-05 (Section 10 - Body). Condition Some owners may comment that their truck has excessive front door or windshield to door wind noise at the A-pillar area. Cause A combination of marginal sealing along the windshield header, and the A-pillar to door crevice gap may contribute to excessive wind noise. Correction A new, service-only, A-pillar weatherstrip and repair procedure have been released. This includes applying a bead of glass sealer along the windshield roof header and installing the new A-pillar seals. Service Procedure 1. Take the customer for a test ride in order to verify the condition. 2. Use masking tape to cover the windshield/roof header gap, and gaps between the windshield and doors at both A-pillars. The purpose in doing this is to seal off any crevices that might generate a wind noise. Important: Remove any aftermarket equipment such as bug deflectors or window deflectors before the test drive. 3. If this eliminated the customer's concern, remove the masking tape used to cover only the windshield header and re-roadtest. This is to confirm the need to seal or not seal this area. 4. If this test failed to isolate the customer concern, determine the root cause by taping up the rest of the vehicle, section by section, until the source of the wind noise is located. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Weatherstrip > Component Information > Technical Service Bulletins > Customer Interest: > 561505A > Mar > 96 > Front Door/A-Pillar - Wind Noise > Page 11530 5. If the second roadtest verified the need to seal the top of the windshield, mask off the top of the windshield encapsulation and the leading edge of the roof with tape so that only the crevice between the roof and windshield is exposed. This will protect the windshield and painted roof surface from damage due to contact with the sealer. (See Figure 1) 6. Obtain locally or from Kem Krest (1-800-955-8591) Permatex Auto Glass Sealer P/N DWS 37 or equivalent, and sparingly apply to the cavity between the roof and windshield encapsulation, following the directions on the package. Note: This product flows into gaps best at or above normal room temperature. Important: Do not use any sealer which contains silicone. Be sure it is smooth and evenly distributed along the entire length of the windshield header. Clean off any excess sealant following the package directions. Remove masking tape and clean off any tape adhesive left behind with adhesive remover. 7. Test fit the A-pillar weatherstrips (P/N 15715158) to the A-pillar encapsulation (See Figure 1) and clean the areas of contact. Remove the weatherstrips. 8. Apply a 1/8th inch thick bead of GM Weatherstrip Adhesive, P/N 12345097 (available from Kern Krest) or equivalent, to the inside crevice of one A-pillar weatherstrip. 9. Install and align the weatherstrip to the A-pillar windshield encapsulation then repeat the process for the other side. 10. Once the adhesive is dry, roadtest to verify the customer concern is corrected. Parts Information P/N Description Qty 15715158 Weatherstrip, A-pillar 2 Service Only 12345097 GM Weatherstrip 1 Adhesive Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Weatherstrip > Component Information > Technical Service Bulletins > Customer Interest: > 561505A > Mar > 96 > Front Door/A-Pillar - Wind Noise > Page 11531 Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time C0020 Glass, Windshield Use Published Labor Reseal Operation time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Weatherstrip > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Weatherstrip: > 99-08-64-016C > Jul > 09 > Body - Maintaining Exterior Weatherstrip Appearance Weatherstrip: All Technical Service Bulletins Body - Maintaining Exterior Weatherstrip Appearance INFORMATION Bulletin No.: 99-08-64-016C Date: July 29, 2009 Subject: Information on Maintaining Exterior Weatherstrip Appearance Models: 2010 and Prior Passenger Cars and Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add model years and update the parts and procedure information. Please discard Corporate Bulletin Number 99-08-64-016B (Section 08 - Body and Accessories). Exterior weatherstrips are exposed to a variety of environmental elements, including UV rays, acid rain, insect and bird residue and atmospheric fallout. All of these may effect the appearance of the weatherstrips; however, they do not effect the functionality of the weatherstrip. Weatherstrips that are discolored should not be replaced under the normal GM New Vehicle Warranty. Weatherstrip Maintenance Instructions Silicone grease on weatherstrips will make them last longer, seal better, and not stick or squeak. Clean the weatherstrips with a mild soap and water solution. Apply silicone grease with a clean cloth. During very cold, damp weather, frequent application may be required. Refer to the information below for the recommended maintenance products. Weatherstrips that are not maintained may crack and weather due to environmental elements. Parts Information Weatherstrip Conditioning Weatherstrip Lubricant (GM P/N 3634770 [in Canada, P/N 10953518]) or Dielectric Silicone Grease (GM P/N 12345579 [in Canada, P/N 992887]). Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Weatherstrip > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Weatherstrip: > 561505A > Mar > 96 > Front Door/A-Pillar - Wind Noise Weatherstrip: All Technical Service Bulletins Front Door/A-Pillar - Wind Noise File In Section: 10 - Body Bulletin No.: 56-15-05A Date: March, 1996 Subject: Front Door/A-Pillar Wind Noise (Install Service Package) Models: 1988-95 Chevrolet and GMC C/K Models 1990-95 Topkick/Kodiak Models This bulletin is being revised to change the service procedure, change the glass sealer and adhesive used and change caption wording. Please discard Corporate Bulletin Number 56-15-05 (Section 10 - Body). Condition Some owners may comment that their truck has excessive front door or windshield to door wind noise at the A-pillar area. Cause A combination of marginal sealing along the windshield header, and the A-pillar to door crevice gap may contribute to excessive wind noise. Correction A new, service-only, A-pillar weatherstrip and repair procedure have been released. This includes applying a bead of glass sealer along the windshield roof header and installing the new A-pillar seals. Service Procedure 1. Take the customer for a test ride in order to verify the condition. 2. Use masking tape to cover the windshield/roof header gap, and gaps between the windshield and doors at both A-pillars. The purpose in doing this is to seal off any crevices that might generate a wind noise. Important: Remove any aftermarket equipment such as bug deflectors or window deflectors before the test drive. 3. If this eliminated the customer's concern, remove the masking tape used to cover only the windshield header and re-roadtest. This is to confirm the need to seal or not seal this area. 4. If this test failed to isolate the customer concern, determine the root cause by taping up the rest of the vehicle, section by section, until the source of the wind noise is located. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Weatherstrip > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Weatherstrip: > 561505A > Mar > 96 > Front Door/A-Pillar - Wind Noise > Page 11541 5. If the second roadtest verified the need to seal the top of the windshield, mask off the top of the windshield encapsulation and the leading edge of the roof with tape so that only the crevice between the roof and windshield is exposed. This will protect the windshield and painted roof surface from damage due to contact with the sealer. (See Figure 1) 6. Obtain locally or from Kem Krest (1-800-955-8591) Permatex Auto Glass Sealer P/N DWS 37 or equivalent, and sparingly apply to the cavity between the roof and windshield encapsulation, following the directions on the package. Note: This product flows into gaps best at or above normal room temperature. Important: Do not use any sealer which contains silicone. Be sure it is smooth and evenly distributed along the entire length of the windshield header. Clean off any excess sealant following the package directions. Remove masking tape and clean off any tape adhesive left behind with adhesive remover. 7. Test fit the A-pillar weatherstrips (P/N 15715158) to the A-pillar encapsulation (See Figure 1) and clean the areas of contact. Remove the weatherstrips. 8. Apply a 1/8th inch thick bead of GM Weatherstrip Adhesive, P/N 12345097 (available from Kern Krest) or equivalent, to the inside crevice of one A-pillar weatherstrip. 9. Install and align the weatherstrip to the A-pillar windshield encapsulation then repeat the process for the other side. 10. Once the adhesive is dry, roadtest to verify the customer concern is corrected. Parts Information P/N Description Qty 15715158 Weatherstrip, A-pillar 2 Service Only 12345097 GM Weatherstrip 1 Adhesive Parts are currently available from GMSPO. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Weatherstrip > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Weatherstrip: > 561505A > Mar > 96 > Front Door/A-Pillar - Wind Noise > Page 11542 Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time C0020 Glass, Windshield Use Published Labor Reseal Operation time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Body and Frame > Weatherstrip > Component Information > Technical Service Bulletins > All Other Service Bulletins for Weatherstrip: > 99-08-64-016C > Jul > 09 > Body - Maintaining Exterior Weatherstrip Appearance Weatherstrip: All Technical Service Bulletins Body - Maintaining Exterior Weatherstrip Appearance INFORMATION Bulletin No.: 99-08-64-016C Date: July 29, 2009 Subject: Information on Maintaining Exterior Weatherstrip Appearance Models: 2010 and Prior Passenger Cars and Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add model years and update the parts and procedure information. Please discard Corporate Bulletin Number 99-08-64-016B (Section 08 - Body and Accessories). Exterior weatherstrips are exposed to a variety of environmental elements, including UV rays, acid rain, insect and bird residue and atmospheric fallout. All of these may effect the appearance of the weatherstrips; however, they do not effect the functionality of the weatherstrip. Weatherstrips that are discolored should not be replaced under the normal GM New Vehicle Warranty. Weatherstrip Maintenance Instructions Silicone grease on weatherstrips will make them last longer, seal better, and not stick or squeak. Clean the weatherstrips with a mild soap and water solution. Apply silicone grease with a clean cloth. During very cold, damp weather, frequent application may be required. Refer to the information below for the recommended maintenance products. Weatherstrips that are not maintained may crack and weather due to environmental elements. Parts Information Weatherstrip Conditioning Weatherstrip Lubricant (GM P/N 3634770 [in Canada, P/N 10953518]) or Dielectric Silicone Grease (GM P/N 12345579 [in Canada, P/N 992887]). Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Locations Instrument Panel Wiring, LH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions Brake Switch (Cruise Control): Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11554 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11555 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11556 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11557 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11558 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11559 Brake Switch (Cruise Control): Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11560 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11561 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11562 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11563 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11564 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11565 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11566 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11567 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11568 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11569 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11570 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11571 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11572 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11573 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11574 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11575 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11576 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11577 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11578 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11579 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11580 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11581 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11582 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11583 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11584 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11585 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Brake Switch (Cruise Control) > Component Information > Description and Operation > Electric Brake Release Switch Brake Switch (Cruise Control): Description and Operation Electric Brake Release Switch The brake pedal is equipped with two switches: a combination stop light/cruise control/TCC switch and a plunger type release switch. Each switch disengages the cruise control system when the brake pedal is depressed. When the brake pedal is released, the system will remain disengaged. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Locations Clutch Switch: Locations At the top of the Clutch Pedal. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions Clutch Switch: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11593 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11594 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11595 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11596 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11597 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11598 Clutch Switch: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11599 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11600 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11601 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11602 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11603 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11604 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11605 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11606 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11607 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11608 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11609 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11610 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11611 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11612 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11613 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11614 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11615 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11616 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11617 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11618 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11619 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11620 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11621 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11622 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11623 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11624 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Clutch Switch, Cruise Control > Component Information > Description and Operation > Electric Clutch Release Switch Clutch Switch: Description and Operation Electric Clutch Release Switch Fig. 3 Electric clutch release switch On models equipped with manual transmission, a plunger type clutch switch, Fig. 3, is used in series with the two brake switches. The switch disengages the cruise control system when the clutch pedal is depressed. When the clutch pedal is released, the system will remain disengaged. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Locations Cruise Control Module: Locations Cruise Control Module Vehicle Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions Cruise Control Module: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11632 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11633 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11634 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11635 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11636 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11637 Cruise Control Module: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11638 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11639 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11640 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11641 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11642 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11643 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11644 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11645 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11646 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11647 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11648 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11649 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11650 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11651 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11652 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11653 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11654 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11655 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11656 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11657 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11658 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11659 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11660 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11661 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11662 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11663 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11664 Cruise Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Description and Operation > Cruise Control Module Cruise Control Module: Description and Operation Cruise Control Module Fig. 1 Cruise Control Module. The cruise control module is mounted near the master cylinder on the engine side of the cowl. The module houses an electronic controller and an electric motor. Together, these components vary throttle position in response to cruise control mode selection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Module > Component Information > Description and Operation > Page 11667 Cruise Control Module: Service and Repair Fig. 15 Cruise control module & cable replacement 1. Disconnect battery ground cable. 2. Disconnect cruise control cable from module, Fig. 15. 3. Remove module attaching screws, then disconnect electrical connector and remove module. The module cannot be serviced. 4. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions Cruise Control Servo: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11672 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11673 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11674 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11675 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11676 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11677 Cruise Control Servo: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11678 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11679 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11680 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11681 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11682 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11683 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11684 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11685 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11686 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11687 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11688 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11689 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11690 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11691 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11692 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11693 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11694 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11695 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11696 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11697 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11698 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11699 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11700 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11701 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11702 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo > Component Information > Diagrams > Diagram Information and Instructions > Page 11703 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo Cable > Component Information > Adjustments Cruise Control Servo Cable: Adjustments Fig. 19 Unlocking cable conduit 1. Unlock the cable conduit engine fitting, Fig. 19. 2. Move cable conduit until throttle plate begins to open. 3. From this position, move conduit in the opposite direction enough to close the throttle plate. 4. Do not release cable, until the cable conduit lock is in place. Fig. 18 Locking cable conduit 5. While holding the cable conduit, firmly push down on the cable conduit until it snaps in place, Fig. 18. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Servo Cable > Component Information > Adjustments > Page 11707 Cruise Control Servo Cable: Service and Repair Fig. 15 Cruise control module & cable replacement Removal 1. Unfasten retainer clip, then remove engine end fitting from lever stud. 2. Remove cable conduit from engine bracket and module housing. 3. Remove cable bead from end of ribbon fitting on cruise module. Installation 1. Connect cable bead to ribbon fitting on cruise module. 2. Position cable conduit over ribbon fitting and insert tangs into module housing. Pull engine end fitting until cable is snug, then rotate cable to position ribbon fitting flat and vertical. The ribbon must not be twisted. 3. Install cable conduit into engine bracket. 4. Unlock cable conduit, then connect engine end fitting of cable to lever stud. 5. Install retainer clip. Secure cable conduit by firmly depressing lock until it snaps into place. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Locations Cruise Control Switch: Locations Steering Column Wiring At the turn signal lever. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions Cruise Control Switch: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11713 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11714 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11715 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11716 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11717 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11718 Cruise Control Switch: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11719 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11720 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11721 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11722 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11723 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11724 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11725 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11726 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11727 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11728 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11729 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11730 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11731 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11732 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11733 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11734 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11735 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11736 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11737 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11738 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11739 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11740 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11741 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11742 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11743 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11744 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Switch > Component Information > Diagrams > Page 11745 Cruise Control Switch: Service and Repair 1. Disconnect battery ground cable. Fig. 38 Cruise Control Switch Replacement. 2. Remove cruise control switch protector cover, Fig. 38. 3. Disconnect switch electrical connector, then remove the switch and cruise control wire. 4. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions Cruise Control Vacuum Vent Solenoid: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11750 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11751 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11752 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11753 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11754 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11755 Cruise Control Vacuum Vent Solenoid: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11756 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11757 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11758 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11759 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11760 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11761 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11762 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11763 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11764 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11765 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11766 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11767 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11768 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11769 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11770 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11771 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11772 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11773 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11774 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11775 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11776 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11777 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11778 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11779 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11780 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Cruise Control Vacuum Vent Solenoid > Component Information > Diagrams > Diagram Information and Instructions > Page 11781 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Locations Cruise Control Module: Locations Cruise Control Module Vehicle Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions Cruise Control Module: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11788 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11789 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11790 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11791 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11792 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11793 Cruise Control Module: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11794 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11795 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11796 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11797 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11798 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11799 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11800 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11801 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11802 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11803 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11804 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11805 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11806 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11807 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11808 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11809 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11810 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11811 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11812 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11813 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11814 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11815 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11816 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11817 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11818 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11819 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Diagrams > Diagram Information and Instructions > Page 11820 Cruise Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Description and Operation > Cruise Control Module Cruise Control Module: Description and Operation Cruise Control Module Fig. 1 Cruise Control Module. The cruise control module is mounted near the master cylinder on the engine side of the cowl. The module houses an electronic controller and an electric motor. Together, these components vary throttle position in response to cruise control mode selection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Relays and Modules - Cruise Control > Cruise Control Module > Component Information > Description and Operation > Page 11823 Cruise Control Module: Service and Repair Fig. 15 Cruise control module & cable replacement 1. Disconnect battery ground cable. 2. Disconnect cruise control cable from module, Fig. 15. 3. Remove module attaching screws, then disconnect electrical connector and remove module. The module cannot be serviced. 4. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Locations Instrument Panel Wiring, LH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions Brake Switch (Cruise Control): Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11830 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11831 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11832 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11833 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11834 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11835 Brake Switch (Cruise Control): Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11836 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11837 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11838 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11839 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11840 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11841 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11842 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11843 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11844 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11845 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11846 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11847 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11848 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11849 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11850 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11851 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11852 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11853 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11854 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11855 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11856 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11857 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11858 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11859 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11860 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Diagrams > Diagram Information and Instructions > Page 11861 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Brake Switch (Cruise Control) > Component Information > Description and Operation > Electric Brake Release Switch Brake Switch (Cruise Control): Description and Operation Electric Brake Release Switch The brake pedal is equipped with two switches: a combination stop light/cruise control/TCC switch and a plunger type release switch. Each switch disengages the cruise control system when the brake pedal is depressed. When the brake pedal is released, the system will remain disengaged. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Locations Clutch Switch: Locations At the top of the Clutch Pedal. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions Clutch Switch: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11869 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11870 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11871 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11872 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11873 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11874 Clutch Switch: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11875 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11876 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11877 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11878 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11879 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11880 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11881 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11882 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11883 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11884 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11885 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11886 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11887 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11888 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11889 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11890 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11891 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11892 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11893 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11894 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11895 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11896 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11897 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11898 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11899 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11900 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Clutch Switch, Cruise Control > Component Information > Description and Operation > Electric Clutch Release Switch Clutch Switch: Description and Operation Electric Clutch Release Switch Fig. 3 Electric clutch release switch On models equipped with manual transmission, a plunger type clutch switch, Fig. 3, is used in series with the two brake switches. The switch disengages the cruise control system when the clutch pedal is depressed. When the clutch pedal is released, the system will remain disengaged. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Locations Cruise Control Switch: Locations Steering Column Wiring At the turn signal lever. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions Cruise Control Switch: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11908 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11909 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11910 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11911 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11912 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11913 Cruise Control Switch: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11914 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11915 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11916 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11917 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11918 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11919 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11920 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11921 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11922 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11923 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11924 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11925 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11926 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11927 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11928 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11929 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11930 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11931 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11932 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11933 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11934 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11935 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11936 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11937 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11938 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 11939 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Cruise Control Switch > Component Information > Diagrams > Page 11940 Cruise Control Switch: Service and Repair 1. Disconnect battery ground cable. Fig. 38 Cruise Control Switch Replacement. 2. Remove cruise control switch protector cover, Fig. 38. 3. Disconnect switch electrical connector, then remove the switch and cruise control wire. 4. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Locations Instrument Panel Wiring, RH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions Vehicle Speed Sensor/Transducer - Cruise Control: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11946 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11947 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11948 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11949 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11950 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11951 Vehicle Speed Sensor/Transducer - Cruise Control: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11952 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11953 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11954 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11955 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11956 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11957 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11958 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11959 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11960 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11961 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11962 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11963 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11964 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11965 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11966 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11967 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11968 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11969 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11970 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11971 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11972 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11973 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11974 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11975 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11976 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Sensors and Switches - Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11977 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions Vacuum Vent Valve: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11982 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11983 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11984 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11985 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11986 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11987 Vacuum Vent Valve: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11988 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11989 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11990 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11991 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11992 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11993 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11994 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11995 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11996 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11997 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11998 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 11999 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12000 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12001 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12002 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12003 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12004 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12005 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12006 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12007 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12008 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12009 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12010 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12011 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12012 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vacuum Vent Valve, Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12013 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Locations Instrument Panel Wiring, RH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions Vehicle Speed Sensor/Transducer - Cruise Control: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12019 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12020 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12021 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12022 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12023 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12024 Vehicle Speed Sensor/Transducer - Cruise Control: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12025 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12026 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12027 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12028 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12029 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12030 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12031 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12032 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12033 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12034 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12035 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12036 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12037 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12038 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12039 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12040 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12041 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12042 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12043 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12044 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12045 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12046 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12047 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12048 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12049 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Cruise Control > Vehicle Speed Sensor/Transducer - Cruise Control > Component Information > Diagrams > Diagram Information and Instructions > Page 12050 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions Audible Warning Device: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12056 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12057 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12058 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12059 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12060 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12061 Audible Warning Device: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12062 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12063 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12064 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12065 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12066 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12067 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12068 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12069 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12070 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12071 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12072 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12073 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12074 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12075 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12076 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12077 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12078 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12079 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12080 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12081 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12082 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12083 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12084 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12085 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12086 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12087 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Diagrams > Diagram Information and Instructions > Page 12088 Audible Warnings Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Description and Operation > Fasten Safety Belts Warning Alarm Audible Warning Device: Description and Operation Fasten Safety Belts Warning Alarm The Fasten Safety Belts Warning Alarm will sound when the following conditions are met simultaneously: The Ignition Switch is in the RUN, BULB TEST or START position and the LH front safety belt is not fastened. When the LH front Safety Belt is not fastened, ground is sensed at the Audio Alarm Module . The alarm will sound for approximately five seconds. The Diagnostic Energy Reserve Module (DERM) also senses ground when the LH Front Safety Belt remains unbuckled. Refer to "Air Bags and Seat Belts". See: Restraint Systems The Audio Alarm Module's Fasten Safety Belt Warning Alarm also incorporates an indicator within the Instrument Cluster. The Fasten Safety Belts Indicator works in conjunction with the Fasten Safety Belts Warning Alarm. When the Audio Alarm Module receives a signal that the LH Front Safety Belt is unfastened, it Connect Voltage to Pin 3 for the Fasten Safety Belts Indicator. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Description and Operation > Fasten Safety Belts Warning Alarm > Page 12091 Audible Warning Device: Description and Operation Key-In Warning Alarm The Key-In Warning Alarm will sound if the following conditions are met simultaneously: The ignition key must be in the Ignition Switch with the Ignition Switch in the ACC, LOCK or OFF position and the LH Front Door must be open. When the ignition key is in the Ignition Switch and the LH Front Door is open, the Key-in Warning Buzzer Switch is closed as is the LH Door Jamb Switch. When both of these switches are closed, ground is sensed at the Audio Alarm Module activating the Key-In Warning Alarm. The Key-In Warning Alarm will stop sounding if the ignition key is removed from the Ignition Switch, the LH front door is closed, or the Ignition Switch is turned to the RUN position. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Description and Operation > Fasten Safety Belts Warning Alarm > Page 12092 Audible Warning Device: Description and Operation Lamps-ON Warning Alarm The Lamps-On Warning Alarm will sound if the following conditions are met simultaneously: The Headlamp and Panel Dimmer Switch is in the HEAD or PARK position, the Panel Dimmer Switch is not in the fully dim position, and the Ignition Switch in the LOCK, ACC or OFF position. When the Headlamp and Panel Dimmer Switch is in the HEAD or PARK position voltage is applied through the ILLUM FUSE 14 to the Audio Alarm Module. When voltage is sensed at the Lamps On input terminal of the Audio Alarm Module and there is an absence of Voltage at the Ignition On Input terminal, then the Lamps-On Warning Alarm will sound. The Lamps-On Warning Alarm can be silenced by either turning the Headlamp Switch to the OFF position or turning the Ignition Switch to the RUN position. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Testing and Inspection > Symptom Related Diagnostic Procedures Audible Warning Device: Symptom Related Diagnostic Procedures Fasten Belts Warning Alarm Fails On Fasten Safety Belts Indicator Fails Off Fasten Safety Belts Indicator Fails On Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Testing and Inspection > Symptom Related Diagnostic Procedures > Page 12095 The Fasten Safety Belts Warning Alarm Fails Off Key-in Warning Alarm Fails Off Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Testing and Inspection > Symptom Related Diagnostic Procedures > Page 12096 Key-in Warning Alarm Fails On Lamps-on Warning Alarm Fails Off Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Testing and Inspection > Symptom Related Diagnostic Procedures > Page 12097 Lamps-on Warning Alarm Fails On No Audible Warning Alarm Functions Troubleshooting Hints 1. CHECK that GAGES FUSE 4, ILLUM FUSE 14 and STOP/HAZ FUSE 1 are not open. If Fuse(s) is open, then LOCATE and REPAIR source of overload and REPLACE Fuse(s). 2. CHECK that Ground G200 is clean and tight. 3. CHECK Fasten Safety Belts Indicator for an open filament. 4. CHECK that Audio Alarm Module is securely mounted in Convenience Center. 5. CHECK that the LH Door Jamb Switch operates freely. 6. If the Lamps-On Warning Alarm is inoperative CHECK to see that the Panel Dimmer Switch is not in the fully dim position. 7. If the Fasten Safety Belts Warning Alarm remains present after 5 seconds, then the Audio Alarm Module may have failed. 8. Failure of two of the three Alarm Functions may indicate Audio Alarm Module failure. 9. Refer to "Instrument Panel Dimming" for diagnosis of Instrument Panel Dimming System. See: Lighting and Horns/Testing and Inspection ^ CHECK for a broken (or partially broken) wire inside of the insulation which could cause system malfunction but prove "GOOD" in a Continuity/Voltage check with a system disconnected. These Circuits may be intermittent or resistive when loaded, and if possible, should be checked by monitoring for a Voltage drop with the system operational (under load). ^ CHECK for proper installation of aftermarket electronic equipment which may affect the integrity of other systems (Refer "Troubleshooting Procedures"). See: Diagrams/Diagnostic Aids Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device > Component Information > Testing and Inspection > Symptom Related Diagnostic Procedures > Page 12098 Audible Warning Device: Component Tests and General Diagnostics Fasten Safety Belts Warning Alarm The Fasten Safety Belts Warning Alarm will sound when the following conditions are met simultaneously: The Ignition Switch is in the RUN, BULB TEST or START position and the LH front safety belt is not fastened. When the LH front Safety Belt is not fastened, ground is sensed at the Audio Alarm Module . The alarm will sound for approximately five seconds. The Diagnostic Energy Reserve Module (DERM) also senses ground when the LH Front Safety Belt remains unbuckled. Refer to "Air Bags and Seat Belts". See: Restraint Systems The Audio Alarm Module's Fasten Safety Belt Warning Alarm also incorporates an indicator within the Instrument Cluster. The Fasten Safety Belts Indicator works in conjunction with the Fasten Safety Belts Warning Alarm. When the Audio Alarm Module receives a signal that the LH Front Safety Belt is unfastened, it Connect Voltage to Pin 3 for the Fasten Safety Belts Indicator. Key-In Warning Alarm The Key-In Warning Alarm will sound if the following conditions are met simultaneously: The ignition key must be in the Ignition Switch with the Ignition Switch in the ACC, LOCK or OFF position and the LH Front Door must be open. When the ignition key is in the Ignition Switch and the LH Front Door is open, the Key-in Warning Buzzer Switch is closed as is the LH Door Jamb Switch. When both of these switches are closed, ground is sensed at the Audio Alarm Module activating the Key-In Warning Alarm. The Key-In Warning Alarm will stop sounding if the ignition key is removed from the Ignition Switch, the LH front door is closed, or the Ignition Switch is turned to the RUN position. Lamps-ON Warning Alarm The Lamps-On Warning Alarm will sound if the following conditions are met simultaneously: The Headlamp and Panel Dimmer Switch is in the HEAD or PARK position, the Panel Dimmer Switch is not in the fully dim position, and the Ignition Switch in the LOCK, ACC or OFF position. When the Headlamp and Panel Dimmer Switch is in the HEAD or PARK position voltage is applied through the ILLUM FUSE 14 to the Audio Alarm Module. When voltage is sensed at the Lamps On input terminal of the Audio Alarm Module and there is an absence of Voltage at the Ignition On Input terminal, then the Lamps-On Warning Alarm will sound. The Lamps-On Warning Alarm can be silenced by either turning the Headlamp Switch to the OFF position or turning the Ignition Switch to the RUN position. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Audible Warning Device Control Module > Component Information > Locations Convenience Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions Brake Warning Indicator: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12106 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12107 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12108 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12109 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12110 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12111 Brake Warning Indicator: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12112 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12113 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12114 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12115 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12116 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12117 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12118 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12119 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12120 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12121 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12122 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12123 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12124 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12125 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12126 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12127 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12128 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12129 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12130 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12131 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12132 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12133 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12134 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12135 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12136 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12137 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Diagram Information and Instructions > Page 12138 Brake Warning System Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Diagrams > Page 12139 Brake Warning Indicator: Description and Operation Battery voltage is applied through the GAGES FUSE 4 to the "BRAKE" Indicator when the Ignition Switch is in the RUN, BULB TEST or START positions. The "BRAKE" Indicator can be lit by having ground applied to it from any of three switches or the Antilock Brake Module. The "BRAKE" Indicator will light whenever the Parking Brake is engaged. When the Parking Brake is engaged, ground is supplied through the closed contacts of the Parking Brake Warning Switch to the "BRAKE" Indicator. The "BRAKE" Indicator lights to alert the driver that the Parking Brake is engaged. The "BRAKE" Indicator will light when the Ignition Switch is turned from the "LOCK" to the RUN position. This is when the Antilock Brake Module conducts its initial test which entails lighting the "BRAKE" Indicator and the ABS Indicator. The Antilock Brake Module will also light the "BRAKE" Indicator if there is a malfunction within the Four Wheel Antilock Brake System which is affecting the operation of the base Hydraulic Braking system. The "BRAKE" Indicator will light if there is low Brake fluid pressure in the front or rear Brakes. When the Combination Valve senses low Brake fluid pressure in the front or rear brakes it closes the Brake Pressure Warning Switch. A ground is supplied through the closed contacts of the Brake Pressure Warning Switch to the "BRAKE" Indicator. With both power and ground applied to the "BRAKE" Indication it will light. The "BRAKE" Indicator will also light whenever the Ignition Switch is turned to the BULB TEST position. The Daytime Running Lamps Module senses ground through the Park Brake Warning Switch. When this input is grounded, the Daytime Running Lamps are not energized. Diode D202 prevents Anti-Lock Brake Module or Brake Pressure Warning Switch operation from turning off the Daytime Running Lamps. The "BRAKE" Indicator will also light whenever the Ignition Switch is turned to the BULB TEST Position. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Testing and Inspection > Initial Inspection and Diagnostic Overview Brake Warning Indicator: Initial Inspection and Diagnostic Overview Circuit Operation Battery voltage is applied through the GAGES FUSE 4 to the "BRAKE" Indicator when the Ignition Switch is in the RUN, BULB TEST or START positions. The "BRAKE" Indicator can be lit by having ground applied to it from any of three switches or the Antilock Brake Module. The "BRAKE" Indicator will light whenever the Parking Brake is engaged. When the Parking Brake is engaged, ground is supplied through the closed contacts of the Parking Brake Warning Switch to the "BRAKE" Indicator. The "BRAKE" Indicator lights to alert the driver that the Parking Brake is engaged. The "BRAKE" Indicator will light when the Ignition Switch is turned from the "LOCK" to the RUN position. This is when the Antilock Brake Module conducts its initial test which entails lighting the "BRAKE" Indicator and the ABS Indicator. The Antilock Brake Module will also light the "BRAKE" Indicator if there is a malfunction within the Four Wheel Antilock Brake System which is affecting the operation of the base Hydraulic Braking system. The "BRAKE" Indicator will light if there is low Brake fluid pressure in the front or rear Brakes. When the Combination Valve senses low Brake fluid pressure in the front or rear brakes it closes the Brake Pressure Warning Switch. A ground is supplied through the closed contacts of the Brake Pressure Warning Switch to the "BRAKE" Indicator. With both power and ground applied to the "BRAKE" Indication it will light. The "BRAKE" Indicator will also light whenever the Ignition Switch is turned to the BULB TEST position. The Daytime Running Lamps Module senses ground through the Park Brake Warning Switch. When this input is grounded, the Daytime Running Lamps are not energized. Diode D202 prevents Anti-Lock Brake Module or Brake Pressure Warning Switch operation from turning off the Daytime Running Lamps. The "BRAKE" Indicator will also light whenever the Ignition Switch is turned to the BULB TEST Position. Troubleshooting Hints 1. CHECK condition of GAGES FUSE 4. If Fuse is Open, LOCATE and REPAIR source of overload and REPLACE Fuse. 2. CHECK that Engine Ground G105 is clean and tight. 3. CHECK the "BRAKE" Indicator Bulb for an open filament. 4. CHECK that the Parking Brake is fully released. 5. Make sure that there is an adequate amount of Brake fluid in the reservoir. 6. If any ABS Diagnostic Codes are Set, Refer Antilock Brake System See: Brakes and Traction Control/Antilock Brakes / Traction Control Systems 7. If the Brake Indicator only lights for the Brake Pressure Warning Switch or for the Anti-Lock Brake Module (Ignition Switch Lock to RUN), then Diode D202 may have opened. 8. If the Brake Indicator only lights for the Ignition Switch in BULB test or for the Park Brake Warning Switch, then Diode 1 in the Underhood Fuse-Relay Center may have opened. ^ CHECK for a broken (or partially broken) wire inside of the insulation which could cause system malfunction but prove "GOOD" in a Continuity/Voltage check with a system disconnected. These Circuits may be intermittent or resistive when loaded, and if possible, should be checked by monitoring for a Voltage drop with the system operational (under load). ^ CHECK for proper installation of aftermarket electronic equipment which may affect the integrity of other systems (Refer "Troubleshooting Procedures"). See: Diagrams/Diagnostic Aids Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Testing and Inspection > Initial Inspection and Diagnostic Overview > Page 12142 Brake Warning Indicator: Symptom Related Diagnostic Procedures Brake Indicator Is Inoperative (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Brake Warning Indicator > Component Information > Testing and Inspection > Initial Inspection and Diagnostic Overview > Page 12143 Brake Indicator Is Inoperative (Part 2 Of 2) Brake Indicator Remains On Continuously Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Charge Lamp/Indicator > Component Information > Testing and Inspection Charge Lamp/Indicator: Testing and Inspection Before performing diagnostic procedures, ensure system wiring is good, alternator belt is tight, and battery is fully charged. TROUBLESHOOTING 1. Check drive belt for wear and proper adjustment. 2. With ignition switch on and engine off, charging indicator lamp should be on. Fig. 23 Charge Indicator Lamp Wiring System. Delcotron Charging System. 3. If indicator lamp is not on, disconnect wiring harness at alternator. Ground "L terminal using a fused 5 amp jumper wire. 4. If lamp lights, replace alternator. If lamp does not light, check for a open between the grounding lead and the ignition switch. Reconnect wiring. 5. With switch on and engine running at a moderate RPM, lamp should be off. If not, stop engine, turn switch on, then disconnect wiring harness at alternator. 6. If lamp goes out, replace alternator. 7. If lamp stays on, check for a grounded "L terminal wire in harness. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Cigarette Lighter > Component Information > Technical Service Bulletins > Customer Interest for Cigarette Lighter: > 99-08-45-005 > Nov > 99 > Accessory Receptacle/Cigar Lighter - Inoperative Cigarette Lighter: Customer Interest Accessory Receptacle/Cigar Lighter - Inoperative File In Section: 08 - Body and Accessories Bulletin No.: 99-08-45-005 Date: November, 1999 TECHNICAL Subject: Accessory Receptacle/Cigar Lighter is Inoperative (Check Aftermarket Device Plug for Short to Ground) Models: 1995-2000 Passenger Cars and Trucks Condition Some customers may comment that the cigar lighter or the accessory receptacle is inoperative; or that the internal fuse (within the plug on an aftermarket device), blows intermittently. Cause Certain aftermarket devices have a newly designed power plug with an internal mini fuse. The mini fuse may have an external terminal (which may be used to externally check the fuse). If the mini fuse external test terminal is not recessed into the mini fuse body, it may come in contact with the shell of the vehicle receptacle and cause the fuse (of either the vehicle or the aftermarket device), to blow intermittently. Correction Test the aftermarket device plug for short to ground. The following step may be performed at the customer's expense. As this is not a defect in material, design or workmanship of the vehicle, it would be the owner's responsibility. 1. Place a piece of tape over the mini fuse terminal temporarily. 2. Explain to the customer that the fuse for the device must have no exposed terminals, and that finding one would be his responsibility. 3. Refer the customer to the manufacturer of the aftermarket device for a new plug. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Cigarette Lighter > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Cigarette Lighter: > 99-08-45-005 > Nov > 99 > Accessory Receptacle/Cigar Lighter - Inoperative Cigarette Lighter: All Technical Service Bulletins Accessory Receptacle/Cigar Lighter - Inoperative File In Section: 08 - Body and Accessories Bulletin No.: 99-08-45-005 Date: November, 1999 TECHNICAL Subject: Accessory Receptacle/Cigar Lighter is Inoperative (Check Aftermarket Device Plug for Short to Ground) Models: 1995-2000 Passenger Cars and Trucks Condition Some customers may comment that the cigar lighter or the accessory receptacle is inoperative; or that the internal fuse (within the plug on an aftermarket device), blows intermittently. Cause Certain aftermarket devices have a newly designed power plug with an internal mini fuse. The mini fuse may have an external terminal (which may be used to externally check the fuse). If the mini fuse external test terminal is not recessed into the mini fuse body, it may come in contact with the shell of the vehicle receptacle and cause the fuse (of either the vehicle or the aftermarket device), to blow intermittently. Correction Test the aftermarket device plug for short to ground. The following step may be performed at the customer's expense. As this is not a defect in material, design or workmanship of the vehicle, it would be the owner's responsibility. 1. Place a piece of tape over the mini fuse terminal temporarily. 2. Explain to the customer that the fuse for the device must have no exposed terminals, and that finding one would be his responsibility. 3. Refer the customer to the manufacturer of the aftermarket device for a new plug. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Cigarette Lighter > Component Information > Technical Service Bulletins > Page 12160 Cigarette Lighter: Locations Center of I/P, at Ashtray Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions Compass: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12165 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12166 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12167 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12168 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12169 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12170 Compass: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12171 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12172 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12173 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12174 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12175 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12176 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12177 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12178 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12179 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12180 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12181 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12182 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12183 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12184 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12185 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12186 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12187 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12188 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12189 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12190 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12191 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12192 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12193 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12194 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12195 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12196 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Diagrams > Diagram Information and Instructions > Page 12197 Electrochromatic Rearview Mirror With Compass Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Testing and Inspection > Initial Inspection and Diagnostic Overview Compass: Initial Inspection and Diagnostic Overview Circuit Operation The Electrochromatic Rear View Mirror dims to a level required to minimize glare while still maintaining maximum rear vision. The mirror switch has three positions; OFF, M and C/M. The M position energizes the mirror only while the C/M position energizes both the mirror and the compass. When a situation requires, the electronic module within the mirror assembly reduces the reflectivity of the Rear View Mirror and automatically dims the LED compass readout. The Automatic Dimming function is inhibited while backing up. COMPASS DISPLAY The Compass Display circuitry is entirely contained within the Rearview Mirror. The compass display is located on the mirror. It presents directional displays relative to symbolic horizon lines and road lines. The electronic compass includes a fluxgate magnetic field sensor and a microprocessor. The microprocessor receives inputs from the sensor, processes them and provides outputs to the compass display which indicates the vehicle heading, relative to the Earth's magnet fields. Troubleshooting Hints 1. CHECK GAUGES Fuse 4. If fuse is open, LOCATE and REPAIR source of overload, and REPLACE Fuse. 2. CHECK that Ground G200 is clean and tight. CHECK for a broken (or partially broken) wire inside of the insulation which could cause system malfunction but prove "GOOD" in Continuity/Voltage Check with a system disconnected. These Circuits may be intermittent or resistive when loaded. and if possible, should be checked by monitoring for a Voltage drop with the system operational (under load). ^ CHECK for proper installation of aftermarket electronic equipment which may affect the integrity of other system (Refer "Troubleshooting Procedures"). See: Diagrams/Diagnostic Aids Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Compass > Component Information > Testing and Inspection > Initial Inspection and Diagnostic Overview > Page 12200 Compass: Symptom Related Diagnostic Procedures Electrochromatic Mirror/Electronic Compass-Inoperative Display Mirror Does Not Respond To Back-up Lamp Operations Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Coolant Level Indicator Lamp > Component Information > Diagrams Low Coolant Level Indicator Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Coolant Level Indicator Lamp > Component Information > Diagrams > Page 12204 Coolant Level Indicator Lamp: Description and Operation This system uses a sensor mounted on the radiator and an indicator light mounted in the instrument panel to warn the driver if coolant level is too low. This light is wired in series with the ignition switch, ECM and the sensor. When the ignition switch is turned to the crank position, the circuit is energized and the indicator light will illuminate. When the ignition switch is turned to the ON position and coolant level is sufficient, the sensor will indicate this to the ECM and the light will turn off. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Coolant Level Indicator Lamp > Component Information > Testing and Inspection > Indicator Lamp Remains Illuminated Coolant Level Indicator Lamp: Testing and Inspection Indicator Lamp Remains Illuminated 1. Turn ignition switch to the On position, then check coolant level and add coolant as necessary. If lamp remains illuminated, proceed to step 2. 2. Disconnect electrical connector at the sensor. If lamp does not illuminate replace the sensor. If lamp remains illuminated, proceed to step 3. 3. Connect electrical lead to the sensor and check for an open circuit between the sensor and the module. Repair or replace as necessary. If circuit is satisfactory, replace the ECM. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Coolant Level Indicator Lamp > Component Information > Testing and Inspection > Indicator Lamp Remains Illuminated > Page 12207 Coolant Level Indicator Lamp: Testing and Inspection Indicator Lamp Will Not Illuminate 1. Turn ignition switch to the crank position, and proceed as follows: a. If lamp illuminates, lamp is satisfactory and connector is properly installed. Proceed to step 2. b. If lamp does not illuminate, check bulb, socket and wiring between socket and module connector. Replace or repair as necessary. 2. Turn ignition switch to the On position and disconnect electrical lead at coolant level sensor mounted on the radiator. If lamp fails to illuminate, check wiring between coolant level sensor connector and ECM for a short circuit to ground. If circuit is satisfactory, replace the ECM. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Dash Board / Instrument Panel <--> [Dashboard / Instrument Panel] > Air Bag(s) Arming and Disarming > System Information > Service and Repair > Air Bag Disarming and Arming Air Bag(s) Arming and Disarming: Service and Repair Air Bag Disarming and Arming Disabling the SIR System Fig. 1 Air Bag Two-way Connector DRIVER SIDE Many service procedures require the air bag system to be disabled to prevent accidental deployment. The air bag system can maintain sufficient voltage to cause deployment for up to 2 minutes after the ignition switch is turned off, the battery ground cable is disconnected or the DERM fuse is removed. If the inflator module is disconnected from the deployment loop by the following procedure, service can begin immediately without waiting for the 2 minute time period to elapse. 1. Turn steering wheel so that vehicle wheels are pointed straight ahead. 2. Turn ignition switch to Lock position and remove key. 3. Remove air bag fuse from fuse block. 4. Remove steering column filler panel. 5. Remove Connector Position Assurance (CPA) and disconnect yellow two-way connector at base of steering column, Fig. 1. PASSENGER SIDE 1. Remove air bag fuse from fuse block. Enabling the SIR System Driver Side 1. Turn ignition switch to LOCK and remove key. 2. Connect yellow two-way connector and install connector position assurance (CPA). 3. Install steering column filler panel. 4. Insert air bag fuse into fuse block. 5. Turn ignition switch to RUN and verify that the air bag warning lamp flashes seven times then turns off. Passenger Side 1. Turn ignition switch to LOCK and remove key. 2. Insert air bag fuse into fuse block. 3. Turn ignition switch to RUN and verify that the air bag warning lamp flashes seven times then turns off. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Dash Board / Instrument Panel <--> [Dashboard / Instrument Panel] > Air Bag(s) Arming and Disarming > System Information > Service and Repair > Air Bag Disarming and Arming > Page 12213 Air Bag(s) Arming and Disarming: Service and Repair General Service Precautions CAUTION: When performing service on or around SIR components or SIR wiring, follow the procedures listed below to temporarily disable the SIR system. Failure to follow procedures could result in possible air bag deployment, personal injury or otherwise unneeded SIR system repairs. The DERM can maintain sufficient voltage to cause a deployment for up to 2 minutes after the ignition switch is turned "OFF," the battery is disconnected, or the fuse powering the DERM is removed. Many of the service procedures require removal of the "AIR BAG" fuse, and disconnection of the inflator module from the deployment loop to avoid an accidental deployment. If the inflator module is disconnected from the deployment loop as noted in the "Disabling the SIR System" procedure that follows, service can begin immediately without waiting for the 2 minute time period to expire. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Dimmer Switch > Component Information > Technical Service Bulletins > IP Dimmer Control - Proper Setting Dimmer Switch: Technical Service Bulletins IP Dimmer Control - Proper Setting File In Section: 08 - Body and Accessories Bulletin No.: 99-08-42-009 Date: November, 1999 INFORMATION Subject: Proper Setting of I/P Dimmer Control to View PRNDL Display with Automatic Headlamp Control Models: 2000 and Prior All Passenger Cars and Trucks With Automatic Headlamp Control and Electronic PRNDL Display Under certain conditions, if the instrument panel dimmer control is turned relatively low, the PRNDL will not be visible until the automatic headlamp control turns the headlamps off and the daytime running lamps (DRL) are turned back on. Such a condition may be if the vehicle is first started in an environment where the headlamp control turns on the headlamps and then the vehicle is driven out into a brighter environment (for example, when a vehicle is backed out of a dark garage into the bright sunlight). This condition is normal and any repair attempt will not be successful. Demonstrate this condition to the customer using the service lane and then turn the instrument panel dimmer control to a higher setting. This will enable the driver to see the PRNDL display Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Door Switch > Component Information > Locations > Cargo Door Jamb Switch Door Switch: Locations Cargo Door Jamb Switch On RH rear Cargo Door Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 12222 Door Switch: Locations Door Jamb Switch, Cargo Upper RH Body Opening incorporated in Cargo Door Contractor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 12223 Door Switch: Locations Door Jamb Switch, LH Front At LH end of I/P Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 12224 Door Switch: Locations Door Jamb Switch, LH Rear Center of LH "B" Pillar Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 12225 Door Switch: Locations Cargo Door Jamb Switch On RH rear Cargo Door Door Jamb Switch, Cargo Upper RH Body Opening incorporated in Cargo Door Contractor Door Jamb Switch, LH Front At LH end of I/P Door Jamb Switch, LH Rear Center of LH "B" Pillar Rear Door Jamb Switch Wiring Door Jamb Switch, RH Front At RH end of I/P Door Jamb Switch, RH Rear Center of RH "B" Pillar Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Fuel Gauge > Component Information > Technical Service Bulletins > Customer Interest for Fuel Gauge: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not Fuel Gauge: Customer Interest Instruments - Fuel Gauge Indicates Empty When Not File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-03A Date: June, 1998 Subject: Fuel Gauge Indicates Empty with 7-8 Gallons (30 Liters) Left in Tank (Replace Fuel Level Sensor Float Arm Assembly) Models: 1995-97 Chevrolet and GMC C/K 4 Door Models Built Prior to VIN Breakpoints: Models VIN Breakpoints Chevrolet VJ355982 GMC VJ724930 This bulletin is being revised to change the labor operation number. Please discard Corporate Bulletin Number 76-83-03 (Section 8 - Chassis/Body Electrical). Condition Some owners may comment that the fuel gauge indicates empty after only going 200 to 250 miles, and they are only able to put approximately 23 gallons or less of fuel in the 30 gallon tank. Cause The Fuel Level Indication System was designed with excessive empty reserve. The Fuel Level Sender will be labeled with Broadcast code "TCB", (see Figure 1). Vehicles built after December 14, 1996, have the revised Float Arm Assembly. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Fuel Gauge > Component Information > Technical Service Bulletins > Customer Interest for Fuel Gauge: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not > Page 12234 Following the procedure described in Section 8A of the Service Manual, remove the Sender Assembly and replace the original Float and Arm with P/N 25312833 (see Figure 2). Reinstall the Sender Assembly and Tank. Parts Information P/N Description Qty 25312833 Float Kit, Fuel Level Sensor 1 The part is currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time L1225 Sender Use published Assembly, Fuel Labor Operation (Tank Unit) - Time Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Fuel Gauge > Component Information > Technical Service Bulletins > Customer Interest for Fuel Gauge: > 76-83-05 > Sep > 97 > Instruments - Excessive Fuel Gauge Fluctuation Fuel Gauge: Customer Interest Instruments - Excessive Fuel Gauge Fluctuation File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-05 Date: September, 1997 Subject: Excessive Fuel Gauge Fluctuation (Install Fuel Level Damper Kit) Models: 1995-97 Chevrolet and GMC C/K 4 Door Utility Models Condition Some owners may comment about excessive fuel gauge needle fluctuation when making turns or braking with less than a half tank of fuel. Correction Install fuel level damper module kit P/N 12167652 following the procedure described on the instruction sheets included with the kit. Parts Information P/N Description Qty 12167652 Module Kit, Fuel Level Damper 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time N4844 Module, Anti-slosh - Install 0.8 hr Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Fuel Gauge > Component Information > Technical Service Bulletins > Customer Interest for Fuel Gauge: > 73-83-15 > Apr > 97 > Instruments - Fuel Gauge Responds Slowly After Fueling Fuel Gauge: Customer Interest Instruments - Fuel Gauge Responds Slowly After Fueling File In Section: 8 - Chassis/Body Electrical Bulletin No.: 73-83-15 Date: April, 1997 INFORMATION Subject: Fuel Gauge Responds Slowly After Fueling Models: 1996-97 Passenger Cars and Trucks (Except Geo) Some owners may comment that the fuel gage reading responds very slowly after fueling the vehicle. The needle may take up to 8 minutes before reaching the "FULL" mark. Most 1997 vehicles, and some 1996, contain a damping function in the fuel gauge circuit. This allows the gauge to respond slowly to changes in tank level, preventing the large needle swings when the vehicle is driven around comers or during acceleration/deceleration. This is called an "anti-slosh" function. The anti-slosh function does not operate immediately after the ignition is first turned on. Therefore, the above condition will only occur if the ignition is left on during fueling. The owner can get the correct reading immediately by turning the ignition key off, then on. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Fuel Gauge > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Gauge: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not Fuel Gauge: All Technical Service Bulletins Instruments - Fuel Gauge Indicates Empty When Not File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-03A Date: June, 1998 Subject: Fuel Gauge Indicates Empty with 7-8 Gallons (30 Liters) Left in Tank (Replace Fuel Level Sensor Float Arm Assembly) Models: 1995-97 Chevrolet and GMC C/K 4 Door Models Built Prior to VIN Breakpoints: Models VIN Breakpoints Chevrolet VJ355982 GMC VJ724930 This bulletin is being revised to change the labor operation number. Please discard Corporate Bulletin Number 76-83-03 (Section 8 - Chassis/Body Electrical). Condition Some owners may comment that the fuel gauge indicates empty after only going 200 to 250 miles, and they are only able to put approximately 23 gallons or less of fuel in the 30 gallon tank. Cause The Fuel Level Indication System was designed with excessive empty reserve. The Fuel Level Sender will be labeled with Broadcast code "TCB", (see Figure 1). Vehicles built after December 14, 1996, have the revised Float Arm Assembly. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Fuel Gauge > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Gauge: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not > Page 12248 Following the procedure described in Section 8A of the Service Manual, remove the Sender Assembly and replace the original Float and Arm with P/N 25312833 (see Figure 2). Reinstall the Sender Assembly and Tank. Parts Information P/N Description Qty 25312833 Float Kit, Fuel Level Sensor 1 The part is currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time L1225 Sender Use published Assembly, Fuel Labor Operation (Tank Unit) - Time Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Fuel Gauge > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Gauge: > 76-83-05 > Sep > 97 > Instruments Excessive Fuel Gauge Fluctuation Fuel Gauge: All Technical Service Bulletins Instruments - Excessive Fuel Gauge Fluctuation File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-05 Date: September, 1997 Subject: Excessive Fuel Gauge Fluctuation (Install Fuel Level Damper Kit) Models: 1995-97 Chevrolet and GMC C/K 4 Door Utility Models Condition Some owners may comment about excessive fuel gauge needle fluctuation when making turns or braking with less than a half tank of fuel. Correction Install fuel level damper module kit P/N 12167652 following the procedure described on the instruction sheets included with the kit. Parts Information P/N Description Qty 12167652 Module Kit, Fuel Level Damper 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time N4844 Module, Anti-slosh - Install 0.8 hr Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Fuel Gauge > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Gauge: > 73-83-15 > Apr > 97 > Instruments - Fuel Gauge Responds Slowly After Fueling Fuel Gauge: All Technical Service Bulletins Instruments - Fuel Gauge Responds Slowly After Fueling File In Section: 8 - Chassis/Body Electrical Bulletin No.: 73-83-15 Date: April, 1997 INFORMATION Subject: Fuel Gauge Responds Slowly After Fueling Models: 1996-97 Passenger Cars and Trucks (Except Geo) Some owners may comment that the fuel gage reading responds very slowly after fueling the vehicle. The needle may take up to 8 minutes before reaching the "FULL" mark. Most 1997 vehicles, and some 1996, contain a damping function in the fuel gauge circuit. This allows the gauge to respond slowly to changes in tank level, preventing the large needle swings when the vehicle is driven around comers or during acceleration/deceleration. This is called an "anti-slosh" function. The anti-slosh function does not operate immediately after the ignition is first turned on. Therefore, the above condition will only occur if the ignition is left on during fueling. The owner can get the correct reading immediately by turning the ignition key off, then on. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Fuel Gauge > Component Information > Testing and Inspection > Fuel Gauge Inaccurate Fuel Gauge: Testing and Inspection Fuel Gauge Inaccurate 1. Ensure terminals are clean and terminal connections are tight. 2. Disconnect fuel tank sender connector, then connect tester J 33431-B, or equivalent, as follows: - Connect tester red lead to purple wire of the connector, then connect the other lead of the tester to a suitable ground. 3. Set resistance dials of tester to 0 ohms and then to 90 ohms. 4. Gauge should read low when resistance is set to 0 ohms and read full when resistance is set to 90 ohms. Allow some time for gauge to read full due to the anti-slosh device. 5. If gauge responds accurately, check for clean mounting surface on sending unit to ensure a good ground. If ground is good, replace sending unit. 6. If gauge does not respond accurately, check circuit between gauge and sending unit for an open or short to ground. If circuit is satisfactory, replace gauge. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Fuel Gauge > Component Information > Testing and Inspection > Fuel Gauge Inaccurate > Page 12259 Fuel Gauge: Testing and Inspection Gauge Stays at Empty This condition is generally caused by a short in the fuel tank wiring circuit. 1. Ensure fuel tank is full, then disconnect lead at fuel tank and turn ignition switch to the On position. 2. If gauge moves but not past full mark, replace fuel tank sending unit. 3. If gauge stays at empty, locate and repair short in circuit between gauge and fuel tank. If circuit is satisfactory, replace gauge. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Fuel Gauge > Component Information > Testing and Inspection > Fuel Gauge Inaccurate > Page 12260 Fuel Gauge: Testing and Inspection Gauge Stays at Full or Beyond This condition is generally caused by a open circuit between the gauge and sending unit. 1. Disconnect sender lead at fuel tank, then ground lead and turn ignition switch to the On position. 2. If fuel gauge reads empty, replace tank sending unit. 3. If gauge reads at full or beyond, locate and repair open in circuit between gauge and fuel tank. If circuit is satisfactory, replace gauge. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Customer Interest for Fuel Gauge Sender: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not Fuel Gauge Sender: Customer Interest Instruments - Fuel Gauge Indicates Empty When Not File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-03A Date: June, 1998 Subject: Fuel Gauge Indicates Empty with 7-8 Gallons (30 Liters) Left in Tank (Replace Fuel Level Sensor Float Arm Assembly) Models: 1995-97 Chevrolet and GMC C/K 4 Door Models Built Prior to VIN Breakpoints: Models VIN Breakpoints Chevrolet VJ355982 GMC VJ724930 This bulletin is being revised to change the labor operation number. Please discard Corporate Bulletin Number 76-83-03 (Section 8 - Chassis/Body Electrical). Condition Some owners may comment that the fuel gauge indicates empty after only going 200 to 250 miles, and they are only able to put approximately 23 gallons or less of fuel in the 30 gallon tank. Cause The Fuel Level Indication System was designed with excessive empty reserve. The Fuel Level Sender will be labeled with Broadcast code "TCB", (see Figure 1). Vehicles built after December 14, 1996, have the revised Float Arm Assembly. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Customer Interest for Fuel Gauge Sender: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not > Page 12269 Following the procedure described in Section 8A of the Service Manual, remove the Sender Assembly and replace the original Float and Arm with P/N 25312833 (see Figure 2). Reinstall the Sender Assembly and Tank. Parts Information P/N Description Qty 25312833 Float Kit, Fuel Level Sensor 1 The part is currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time L1225 Sender Use published Assembly, Fuel Labor Operation (Tank Unit) - Time Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Customer Interest for Fuel Gauge Sender: > 76-83-05 > Sep > 97 > Instruments - Excessive Fuel Gauge Fluctuation Fuel Gauge Sender: Customer Interest Instruments - Excessive Fuel Gauge Fluctuation File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-05 Date: September, 1997 Subject: Excessive Fuel Gauge Fluctuation (Install Fuel Level Damper Kit) Models: 1995-97 Chevrolet and GMC C/K 4 Door Utility Models Condition Some owners may comment about excessive fuel gauge needle fluctuation when making turns or braking with less than a half tank of fuel. Correction Install fuel level damper module kit P/N 12167652 following the procedure described on the instruction sheets included with the kit. Parts Information P/N Description Qty 12167652 Module Kit, Fuel Level Damper 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time N4844 Module, Anti-slosh - Install 0.8 hr Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Fuel Gauge Sender > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Gauge Sender: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not Fuel Gauge Sender: All Technical Service Bulletins Instruments - Fuel Gauge Indicates Empty When Not File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-03A Date: June, 1998 Subject: Fuel Gauge Indicates Empty with 7-8 Gallons (30 Liters) Left in Tank (Replace Fuel Level Sensor Float Arm Assembly) Models: 1995-97 Chevrolet and GMC C/K 4 Door Models Built Prior to VIN Breakpoints: Models VIN Breakpoints Chevrolet VJ355982 GMC VJ724930 This bulletin is being revised to change the labor operation number. Please discard Corporate Bulletin Number 76-83-03 (Section 8 - Chassis/Body Electrical). Condition Some owners may comment that the fuel gauge indicates empty after only going 200 to 250 miles, and they are only able to put approximately 23 gallons or less of fuel in the 30 gallon tank. Cause The Fuel Level Indication System was designed with excessive empty reserve. The Fuel Level Sender will be labeled with Broadcast code "TCB", (see Figure 1). Vehicles built after December 14, 1996, have the revised Float Arm Assembly. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Fuel Gauge Sender > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Gauge Sender: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not > Page 12279 Following the procedure described in Section 8A of the Service Manual, remove the Sender Assembly and replace the original Float and Arm with P/N 25312833 (see Figure 2). Reinstall the Sender Assembly and Tank. Parts Information P/N Description Qty 25312833 Float Kit, Fuel Level Sensor 1 The part is currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time L1225 Sender Use published Assembly, Fuel Labor Operation (Tank Unit) - Time Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Fuel Gauge Sender > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Gauge Sender: > 76-83-05 > Sep > 97 > Instruments - Excessive Fuel Gauge Fluctuation Fuel Gauge Sender: All Technical Service Bulletins Instruments - Excessive Fuel Gauge Fluctuation File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-05 Date: September, 1997 Subject: Excessive Fuel Gauge Fluctuation (Install Fuel Level Damper Kit) Models: 1995-97 Chevrolet and GMC C/K 4 Door Utility Models Condition Some owners may comment about excessive fuel gauge needle fluctuation when making turns or braking with less than a half tank of fuel. Correction Install fuel level damper module kit P/N 12167652 following the procedure described on the instruction sheets included with the kit. Parts Information P/N Description Qty 12167652 Module Kit, Fuel Level Damper 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time N4844 Module, Anti-slosh - Install 0.8 hr Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Page 12284 Fuel Gauge Sender: Locations In rear Fuel Tank Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Page 12285 Fuel Gage Sender (Auxiliary Fuel Tank) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Instrument Cluster / Carrier <--> [Instrument Cluster / Carrier] > Air Bag(s) Arming and Disarming > System Information > Service and Repair > Air Bag Disarming and Arming Air Bag(s) Arming and Disarming: Service and Repair Air Bag Disarming and Arming Disabling the SIR System Fig. 1 Air Bag Two-way Connector DRIVER SIDE Many service procedures require the air bag system to be disabled to prevent accidental deployment. The air bag system can maintain sufficient voltage to cause deployment for up to 2 minutes after the ignition switch is turned off, the battery ground cable is disconnected or the DERM fuse is removed. If the inflator module is disconnected from the deployment loop by the following procedure, service can begin immediately without waiting for the 2 minute time period to elapse. 1. Turn steering wheel so that vehicle wheels are pointed straight ahead. 2. Turn ignition switch to Lock position and remove key. 3. Remove air bag fuse from fuse block. 4. Remove steering column filler panel. 5. Remove Connector Position Assurance (CPA) and disconnect yellow two-way connector at base of steering column, Fig. 1. PASSENGER SIDE 1. Remove air bag fuse from fuse block. Enabling the SIR System Driver Side 1. Turn ignition switch to LOCK and remove key. 2. Connect yellow two-way connector and install connector position assurance (CPA). 3. Install steering column filler panel. 4. Insert air bag fuse into fuse block. 5. Turn ignition switch to RUN and verify that the air bag warning lamp flashes seven times then turns off. Passenger Side 1. Turn ignition switch to LOCK and remove key. 2. Insert air bag fuse into fuse block. 3. Turn ignition switch to RUN and verify that the air bag warning lamp flashes seven times then turns off. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Instrument Cluster / Carrier <--> [Instrument Cluster / Carrier] > Air Bag(s) Arming and Disarming > System Information > Service and Repair > Air Bag Disarming and Arming > Page 12291 Air Bag(s) Arming and Disarming: Service and Repair General Service Precautions CAUTION: When performing service on or around SIR components or SIR wiring, follow the procedures listed below to temporarily disable the SIR system. Failure to follow procedures could result in possible air bag deployment, personal injury or otherwise unneeded SIR system repairs. The DERM can maintain sufficient voltage to cause a deployment for up to 2 minutes after the ignition switch is turned "OFF," the battery is disconnected, or the fuse powering the DERM is removed. Many of the service procedures require removal of the "AIR BAG" fuse, and disconnection of the inflator module from the deployment loop to avoid an accidental deployment. If the inflator module is disconnected from the deployment loop as noted in the "Disabling the SIR System" procedure that follows, service can begin immediately without waiting for the 2 minute time period to expire. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Key Reminder Switch > Component Information > Locations Key Reminder Switch: Locations In Steering Column Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition Malfunction Indicator Lamp: Customer Interest PROM - MIL ON, Poor Driveability Condition File In Section: 6E - Engine Fuel & Emission Bulletin No.: 76-65-04 Date: March, 1997 Subject: Malfunction Indicator Light (MIL) On, Poor Driveability Conditions (Perform Flash Calibration) Models: 1996-97 Chevrolet and GMC Light Duty Trucks 1996-97 Chevrolet Tiltmaster and GMC Forward W4 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L Engines (VINs X, W, M, R RPOs LF6, L35, L3O, L31) Condition An owner of the above mentioned vehicles may report that the Malfunction Indicator Light (MIL) is on and/or the vehicle has one or more of the following driveability conditions. 1. 5.7L (L31) only: Surge or chuggle at speeds of 42 to 65 MPH while at steady speed or under light to moderate acceleration with the TCC applied. 2. MIL on with DTC P0172 or P0175 stored but no reported driveability symptoms. 3. MIL on with TDC P1406 stored and rough engine or poor driveability symptoms. 4. When operating at altitudes above 5,000 feet, an audible spark knock noise is heard. 5. Hesitation and/or misfire during light cruise conditions due to ignition cross-fire with no DTC stored. This will only occur on V-6 engines with cam retard offset in excess of 26° and V-8's with cam retard offset in excess of 15°. 6. The MIL may be on and a DTC stored for an engine misfire but no misfire occurred. 7. Engine exhibits an idle speed surge or roll. 1996 Models Only 8. MIL on with DTC P0102 stored but no reported driveability symptoms. 9. 5.0L (L30) & 5.7L (L31) only: Difficult starting in extreme cold (below 0° F) conditions. 10. 5.7L (L31) only: Poorer than expected fuel economy when heavily loaded. 1997 Models Only 11. MIL on with DTC P0121 stored but no reported driveability symptoms. 12. C/K & S/T Models with either V-6 engine and manual transmission: An engine flare between shifts may be noted when the engine is cold. 13. Either V-6 engine and manual transmission: An engine flare between shifts may be noted when the engine is cold. 14. C/K, S/T and M/L Models equipped with L35 V-6 engine, an improvement to the vapor canister purge diagnostics is incorporated into the new calibrations so that the Tech II can turn on canister purge at idle speed. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 12303 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 12304 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 12305 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 12306 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 12307 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Customer Interest for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 12308 Follow the Strategy Based Diagnostic Steps for the customer's reported symptoms. If diagnosis does not reveal a cause, refer to the tables below for the applicable calibration change. Perform programming per the latest Techline information for programming procedures. Important The calibrations listed are FLASH calibrations and are not available from GMSPO. They are available on 1997 Techline CD Disc 5 and later. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J-6355 Use Published Labor Operation Time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition Malfunction Indicator Lamp: All Technical Service Bulletins PROM - MIL ON, Poor Driveability Condition File In Section: 6E - Engine Fuel & Emission Bulletin No.: 76-65-04 Date: March, 1997 Subject: Malfunction Indicator Light (MIL) On, Poor Driveability Conditions (Perform Flash Calibration) Models: 1996-97 Chevrolet and GMC Light Duty Trucks 1996-97 Chevrolet Tiltmaster and GMC Forward W4 Models 1996-97 Oldsmobile Bravada with 4.3L, 5.0L, 5.7L Engines (VINs X, W, M, R RPOs LF6, L35, L3O, L31) Condition An owner of the above mentioned vehicles may report that the Malfunction Indicator Light (MIL) is on and/or the vehicle has one or more of the following driveability conditions. 1. 5.7L (L31) only: Surge or chuggle at speeds of 42 to 65 MPH while at steady speed or under light to moderate acceleration with the TCC applied. 2. MIL on with DTC P0172 or P0175 stored but no reported driveability symptoms. 3. MIL on with TDC P1406 stored and rough engine or poor driveability symptoms. 4. When operating at altitudes above 5,000 feet, an audible spark knock noise is heard. 5. Hesitation and/or misfire during light cruise conditions due to ignition cross-fire with no DTC stored. This will only occur on V-6 engines with cam retard offset in excess of 26° and V-8's with cam retard offset in excess of 15°. 6. The MIL may be on and a DTC stored for an engine misfire but no misfire occurred. 7. Engine exhibits an idle speed surge or roll. 1996 Models Only 8. MIL on with DTC P0102 stored but no reported driveability symptoms. 9. 5.0L (L30) & 5.7L (L31) only: Difficult starting in extreme cold (below 0° F) conditions. 10. 5.7L (L31) only: Poorer than expected fuel economy when heavily loaded. 1997 Models Only 11. MIL on with DTC P0121 stored but no reported driveability symptoms. 12. C/K & S/T Models with either V-6 engine and manual transmission: An engine flare between shifts may be noted when the engine is cold. 13. Either V-6 engine and manual transmission: An engine flare between shifts may be noted when the engine is cold. 14. C/K, S/T and M/L Models equipped with L35 V-6 engine, an improvement to the vapor canister purge diagnostics is incorporated into the new calibrations so that the Tech II can turn on canister purge at idle speed. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 12314 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 12315 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 12316 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 12317 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 12318 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Malfunction Indicator Lamp: > 766504 > Mar > 97 > PROM - MIL ON, Poor Driveability Condition > Page 12319 Follow the Strategy Based Diagnostic Steps for the customer's reported symptoms. If diagnosis does not reveal a cause, refer to the tables below for the applicable calibration change. Perform programming per the latest Techline information for programming procedures. Important The calibrations listed are FLASH calibrations and are not available from GMSPO. They are available on 1997 Techline CD Disc 5 and later. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J-6355 Use Published Labor Operation Time Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Malfunction Indicator Lamp > Component Information > Technical Service Bulletins > Page 12320 Malfunction Indicator Lamp: Service and Repair The CHECK ENGINE LAMP will be illuminated when the ignition switch is placed in the "ON" position. When the engine is started, the lamp should turn "OFF". If the lamp remains "ON" for 10 seconds or constantly after the engine is started, the self diagnosis system has detected a problem and has stored a code in the system Control Module. After diagnosis and repair, the ECM memory can be cleared of codes by removing the Control Module fuse or disconnecting the battery ground cable for approximately 30 seconds, with ignition switch in the "OFF" position. NOTE If battery ground cable is disconnected to clear codes, components such as clocks, electronically tuned radios etc., will have to be reset. - It is a good idea to record preset radio stations before disconnecting the negative battery cable. This will allow the stations to be reset as to not inconvenience the customer. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Odometer > Component Information > Technical Service Bulletins > Odometer/Speedometer - ACDelco Service Center Locations Odometer: Technical Service Bulletins Odometer/Speedometer - ACDelco Service Center Locations File In Section: 8 - Chassis/Body Electrical Bulletin No.: 66-83-04A Date: September, 1996 INFORMATION Subject: AC Delco Service Center Locations for Odometer/Speedometer Service Models: 1997 and Prior Passenger Cars and Trucks (excluding Cadillac) This bulletin is being revised to provide the necessary contact information only. Please discard Corporate Bulletin Number 66-83-04 (Section 8 - Chassis/Body Electrical) General Motors provides service for sophisticated electronic products through the authorized AC Delco Service Center Program. This program is designed to provide GM vehicle owners with the highest quality and most technically up-to-date product available. Repair products from unauthorized service outlets are not acceptable as warranty replacements. Currently, there are 25 authorized AC Delco Service Centers who exchange and remanufacture odometer/speedometers (list included). Only these Centers should be contacted for service. Important: W series and 1997 T series Medium Duty truck odometer/speedometers must be ordered directly from GMSPO. The following steps should be taken when utilizing the AC Delco Service Centers: Dealers should contact their local AC Delco Service Center (list included). Any listed facility may be used. The following information must be provided: Part number VIN, Mileage, Vehicle Year, Make and Model Dealer Name and Address Delivery Date of Vehicle Name of the person requesting exchange or service Phone number Repair Order Number P.O. number (if non - warranty) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Odometer > Component Information > Technical Service Bulletins > Odometer/Speedometer - ACDelco Service Center Locations > Page 12325 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Odometer > Component Information > Technical Service Bulletins > Odometer/Speedometer - ACDelco Service Center Locations > Page 12326 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Odometer > Component Information > Technical Service Bulletins > Odometer/Speedometer - ACDelco Service Center Locations > Page 12327 AC Delco Service Centers Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Oil Pressure Gauge > Component Information > Testing and Inspection > Gauge Readings Are Inaccurate Oil Pressure Gauge: Testing and Inspection Gauge Readings Are Inaccurate 1. Remove lead from sensor, then connect tester J 33431-A or equivalent to sensor lead and ground. 2. If gauge responds accurately to tester, replace sensor. 3. If gauge does not respond accurately to tester, replace cluster. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Oil Pressure Gauge > Component Information > Testing and Inspection > Gauge Readings Are Inaccurate > Page 12332 Oil Pressure Gauge: Testing and Inspection Gauge Reads High 1. Disconnect lead from sensor, then turn ignition switch to the ON position and ground lead. 2. If gauge reads low, replace sensor. 3. If gauge reads high, locate and repair open circuit between sensor and gauge. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Oil Pressure Gauge > Component Information > Testing and Inspection > Gauge Readings Are Inaccurate > Page 12333 Oil Pressure Gauge: Testing and Inspection Gauge Reads Low 1. Check oil level, add if necessary. 2. Turn ignition switch to the On position. 3. Remove oil pressure sensor lead at sensor, gauge should read high. 4. If gauge stays low, remove sensor lead at gauge. Gauge should read high. If gauge reads high, locate and repair short to ground between gauge and sensor. 5. If gauge still reads low, replace cluster. 6. With lead removed at sensor, connect an ohmmeter to sensor. With engine stopped resistance should be one ohm, and approximately 44 ohms with engine running. 7. If sensor reads significantly lower than 44 ohms with engine running, replace sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Oil Pressure Sender > Component Information > Locations Oil Pressure Sender: Locations LH side of Engine, rear Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Oil Pressure Warning Lamp/Indicator > Component Information > Description and Operation Oil Pressure Warning Lamp/Indicator: Description and Operation Many trucks use a warning light on the instrument panel in place of the conventional dash indicating gauge to warn the driver when the oil pressure is dangerously low. The warning light is wired in series with the ignition switch and the engine unit--which is an oil pressure switch. The oil pressure switch contains a diaphragm and a set of contacts. When the ignition switch is turned on, the warning light circuit is energized and the circuit is completed through the closed contacts in the pressure switch. When the engine is started, build-up of oil pressure compresses the diaphragm, opening the contacts, thereby breaking the circuit causing the light to go out. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Relays and Modules - Instrument Panel > Audible Warning Device Control Module > Component Information > Locations Convenience Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Sensors and Switches - Instrument Panel > Dimmer Switch > Component Information > Technical Service Bulletins > IP Dimmer Control - Proper Setting Dimmer Switch: Technical Service Bulletins IP Dimmer Control - Proper Setting File In Section: 08 - Body and Accessories Bulletin No.: 99-08-42-009 Date: November, 1999 INFORMATION Subject: Proper Setting of I/P Dimmer Control to View PRNDL Display with Automatic Headlamp Control Models: 2000 and Prior All Passenger Cars and Trucks With Automatic Headlamp Control and Electronic PRNDL Display Under certain conditions, if the instrument panel dimmer control is turned relatively low, the PRNDL will not be visible until the automatic headlamp control turns the headlamps off and the daytime running lamps (DRL) are turned back on. Such a condition may be if the vehicle is first started in an environment where the headlamp control turns on the headlamps and then the vehicle is driven out into a brighter environment (for example, when a vehicle is backed out of a dark garage into the bright sunlight). This condition is normal and any repair attempt will not be successful. Demonstrate this condition to the customer using the service lane and then turn the instrument panel dimmer control to a higher setting. This will enable the driver to see the PRNDL display Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Sensors and Switches - Instrument Panel > Door Switch > Component Information > Locations > Cargo Door Jamb Switch Door Switch: Locations Cargo Door Jamb Switch On RH rear Cargo Door Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Sensors and Switches - Instrument Panel > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 12353 Door Switch: Locations Door Jamb Switch, Cargo Upper RH Body Opening incorporated in Cargo Door Contractor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Sensors and Switches - Instrument Panel > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 12354 Door Switch: Locations Door Jamb Switch, LH Front At LH end of I/P Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Sensors and Switches - Instrument Panel > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 12355 Door Switch: Locations Door Jamb Switch, LH Rear Center of LH "B" Pillar Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Sensors and Switches - Instrument Panel > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 12356 Door Switch: Locations Cargo Door Jamb Switch On RH rear Cargo Door Door Jamb Switch, Cargo Upper RH Body Opening incorporated in Cargo Door Contractor Door Jamb Switch, LH Front At LH end of I/P Door Jamb Switch, LH Rear Center of LH "B" Pillar Rear Door Jamb Switch Wiring Door Jamb Switch, RH Front At RH end of I/P Door Jamb Switch, RH Rear Center of RH "B" Pillar Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Sensors and Switches - Instrument Panel > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Customer Interest for Fuel Gauge Sender: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not Fuel Gauge Sender: Customer Interest Instruments - Fuel Gauge Indicates Empty When Not File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-03A Date: June, 1998 Subject: Fuel Gauge Indicates Empty with 7-8 Gallons (30 Liters) Left in Tank (Replace Fuel Level Sensor Float Arm Assembly) Models: 1995-97 Chevrolet and GMC C/K 4 Door Models Built Prior to VIN Breakpoints: Models VIN Breakpoints Chevrolet VJ355982 GMC VJ724930 This bulletin is being revised to change the labor operation number. Please discard Corporate Bulletin Number 76-83-03 (Section 8 - Chassis/Body Electrical). Condition Some owners may comment that the fuel gauge indicates empty after only going 200 to 250 miles, and they are only able to put approximately 23 gallons or less of fuel in the 30 gallon tank. Cause The Fuel Level Indication System was designed with excessive empty reserve. The Fuel Level Sender will be labeled with Broadcast code "TCB", (see Figure 1). Vehicles built after December 14, 1996, have the revised Float Arm Assembly. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Sensors and Switches - Instrument Panel > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Customer Interest for Fuel Gauge Sender: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not > Page 12365 Following the procedure described in Section 8A of the Service Manual, remove the Sender Assembly and replace the original Float and Arm with P/N 25312833 (see Figure 2). Reinstall the Sender Assembly and Tank. Parts Information P/N Description Qty 25312833 Float Kit, Fuel Level Sensor 1 The part is currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time L1225 Sender Use published Assembly, Fuel Labor Operation (Tank Unit) - Time Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Sensors and Switches - Instrument Panel > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Customer Interest for Fuel Gauge Sender: > 76-83-05 > Sep > 97 > Instruments - Excessive Fuel Gauge Fluctuation Fuel Gauge Sender: Customer Interest Instruments - Excessive Fuel Gauge Fluctuation File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-05 Date: September, 1997 Subject: Excessive Fuel Gauge Fluctuation (Install Fuel Level Damper Kit) Models: 1995-97 Chevrolet and GMC C/K 4 Door Utility Models Condition Some owners may comment about excessive fuel gauge needle fluctuation when making turns or braking with less than a half tank of fuel. Correction Install fuel level damper module kit P/N 12167652 following the procedure described on the instruction sheets included with the kit. Parts Information P/N Description Qty 12167652 Module Kit, Fuel Level Damper 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time N4844 Module, Anti-slosh - Install 0.8 hr Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Sensors and Switches - Instrument Panel > Fuel Gauge Sender > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Gauge Sender: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not Fuel Gauge Sender: All Technical Service Bulletins Instruments - Fuel Gauge Indicates Empty When Not File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-03A Date: June, 1998 Subject: Fuel Gauge Indicates Empty with 7-8 Gallons (30 Liters) Left in Tank (Replace Fuel Level Sensor Float Arm Assembly) Models: 1995-97 Chevrolet and GMC C/K 4 Door Models Built Prior to VIN Breakpoints: Models VIN Breakpoints Chevrolet VJ355982 GMC VJ724930 This bulletin is being revised to change the labor operation number. Please discard Corporate Bulletin Number 76-83-03 (Section 8 - Chassis/Body Electrical). Condition Some owners may comment that the fuel gauge indicates empty after only going 200 to 250 miles, and they are only able to put approximately 23 gallons or less of fuel in the 30 gallon tank. Cause The Fuel Level Indication System was designed with excessive empty reserve. The Fuel Level Sender will be labeled with Broadcast code "TCB", (see Figure 1). Vehicles built after December 14, 1996, have the revised Float Arm Assembly. Correction Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Sensors and Switches - Instrument Panel > Fuel Gauge Sender > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Gauge Sender: > 76-83-03A > Jun > 98 > Instruments - Fuel Gauge Indicates Empty When Not > Page 12375 Following the procedure described in Section 8A of the Service Manual, remove the Sender Assembly and replace the original Float and Arm with P/N 25312833 (see Figure 2). Reinstall the Sender Assembly and Tank. Parts Information P/N Description Qty 25312833 Float Kit, Fuel Level Sensor 1 The part is currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time L1225 Sender Use published Assembly, Fuel Labor Operation (Tank Unit) - Time Replace Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Sensors and Switches - Instrument Panel > Fuel Gauge Sender > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Fuel Gauge Sender: > 76-83-05 > Sep > 97 > Instruments - Excessive Fuel Gauge Fluctuation Fuel Gauge Sender: All Technical Service Bulletins Instruments - Excessive Fuel Gauge Fluctuation File In Section: 8 - Chassis/Body Electrical Bulletin No.: 76-83-05 Date: September, 1997 Subject: Excessive Fuel Gauge Fluctuation (Install Fuel Level Damper Kit) Models: 1995-97 Chevrolet and GMC C/K 4 Door Utility Models Condition Some owners may comment about excessive fuel gauge needle fluctuation when making turns or braking with less than a half tank of fuel. Correction Install fuel level damper module kit P/N 12167652 following the procedure described on the instruction sheets included with the kit. Parts Information P/N Description Qty 12167652 Module Kit, Fuel Level Damper 1 Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Op Description Labor Time N4844 Module, Anti-slosh - Install 0.8 hr Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Sensors and Switches - Instrument Panel > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Page 12380 Fuel Gauge Sender: Locations In rear Fuel Tank Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Sensors and Switches - Instrument Panel > Fuel Gauge Sender > Component Information > Technical Service Bulletins > Page 12381 Fuel Gage Sender (Auxiliary Fuel Tank) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Sensors and Switches - Instrument Panel > Key Reminder Switch > Component Information > Locations Key Reminder Switch: Locations In Steering Column Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Speedometer Head > Component Information > Technical Service Bulletins > Odometer/Speedometer - ACDelco Service Center Locations Speedometer Head: Technical Service Bulletins Odometer/Speedometer - ACDelco Service Center Locations File In Section: 8 - Chassis/Body Electrical Bulletin No.: 66-83-04A Date: September, 1996 INFORMATION Subject: AC Delco Service Center Locations for Odometer/Speedometer Service Models: 1997 and Prior Passenger Cars and Trucks (excluding Cadillac) This bulletin is being revised to provide the necessary contact information only. Please discard Corporate Bulletin Number 66-83-04 (Section 8 - Chassis/Body Electrical) General Motors provides service for sophisticated electronic products through the authorized AC Delco Service Center Program. This program is designed to provide GM vehicle owners with the highest quality and most technically up-to-date product available. Repair products from unauthorized service outlets are not acceptable as warranty replacements. Currently, there are 25 authorized AC Delco Service Centers who exchange and remanufacture odometer/speedometers (list included). Only these Centers should be contacted for service. Important: W series and 1997 T series Medium Duty truck odometer/speedometers must be ordered directly from GMSPO. The following steps should be taken when utilizing the AC Delco Service Centers: Dealers should contact their local AC Delco Service Center (list included). Any listed facility may be used. The following information must be provided: Part number VIN, Mileage, Vehicle Year, Make and Model Dealer Name and Address Delivery Date of Vehicle Name of the person requesting exchange or service Phone number Repair Order Number P.O. number (if non - warranty) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Speedometer Head > Component Information > Technical Service Bulletins > Odometer/Speedometer - ACDelco Service Center Locations > Page 12389 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Speedometer Head > Component Information > Technical Service Bulletins > Odometer/Speedometer - ACDelco Service Center Locations > Page 12390 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Speedometer Head > Component Information > Technical Service Bulletins > Odometer/Speedometer - ACDelco Service Center Locations > Page 12391 AC Delco Service Centers Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Temperature Gauge > Component Information > Technical Service Bulletins > Customer Interest for Temperature Gauge: > 676201 > Apr > 96 > Engine Extreme Temperature Gauge Fluctuation Temperature Gauge: Customer Interest Engine - Extreme Temperature Gauge Fluctuation File In Section: 6 - Engine Bulletin No.: 67-62-01 Date: April, 1996 Subject: Extreme Engine Temperature Gauge Fluctuation (Install a New Thermostat) Models: 1996 Chevrolet and GMC C/K, G Models with 4.3L, 5.0L, 5.7L Engines (VINs M, R, X, W RPOs L30, L31, LF6, L35) Condition Some owners may experience extreme engine temperature gauge fluctuation. Cause Thermostat was not optimally positioned to sense true engine coolant temperature. Correction Install a new thermostat which increases coolant flow past the thermostat temperature sensing element. Parts Information Refer to the following part number when replacing the thermostat: Part Number Description 12557859 Thermostat Parts are expected to be available on April 8, 1996 from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J3500 Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Temperature Gauge > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Temperature Gauge: > 676201 > Apr > 96 > Engine - Extreme Temperature Gauge Fluctuation Temperature Gauge: All Technical Service Bulletins Engine - Extreme Temperature Gauge Fluctuation File In Section: 6 - Engine Bulletin No.: 67-62-01 Date: April, 1996 Subject: Extreme Engine Temperature Gauge Fluctuation (Install a New Thermostat) Models: 1996 Chevrolet and GMC C/K, G Models with 4.3L, 5.0L, 5.7L Engines (VINs M, R, X, W RPOs L30, L31, LF6, L35) Condition Some owners may experience extreme engine temperature gauge fluctuation. Cause Thermostat was not optimally positioned to sense true engine coolant temperature. Correction Install a new thermostat which increases coolant flow past the thermostat temperature sensing element. Parts Information Refer to the following part number when replacing the thermostat: Part Number Description 12557859 Thermostat Parts are expected to be available on April 8, 1996 from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Labor Time J3500 Use published labor operation time. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Temperature Gauge > Component Information > Testing and Inspection > Gauge Does Not Move From Cold When Engine Is Hot Temperature Gauge: Testing and Inspection Gauge Does Not Move From Cold When Engine Is Hot This condition is generally caused by a blown fuse, open circuit or faulty sensor. 1. Check fuse, replace if necessary. 2. Turn ignition switch to On position, then remove lead at sensor unit. 3. Connect test lamp from sensor lead to ground, lamp should glow. Short sensor lead to ground, gauge should indicate "Hot." 4. If gauge indicated HOT, check lead on sensor. If satisfactory, replace sensor. If gauge indicates COLD, replace cluster. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Temperature Gauge > Component Information > Testing and Inspection > Gauge Does Not Move From Cold When Engine Is Hot > Page 12407 Temperature Gauge: Testing and Inspection Gauge Indicates Hot When Engine Is Cold This condition is generally caused by a shorted or grounded circuit. 1. Remove sensor lead at sensor unit. Gauge should move to COLD position, if not check unit for a external short. If no external short is found, replace sensor. 2. If gauge stays HOT, check for a short circuit in gauge to sensor wiring. If circuit is satisfactory, replace cluster. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Temperature Gauge > Component Information > Testing and Inspection > Gauge Does Not Move From Cold When Engine Is Hot > Page 12408 Temperature Gauge: Testing and Inspection Gauge Reads High 1. Remove lead at sensor, measure resistance using an ohmmeter. 2. At 104 degrees F resistance should be approximately 1200-1350 ohms, and at 125 degrees F resistance should be approximately 53-55 ohms. 3. If resistance is not within specifications, replace sensor. 4. Disconnect lead at sensor and gauge, check for a high resistance using an ohmmeter. Repair wiring if necessary. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Temperature Gauge > Component Information > Testing and Inspection > Gauge Does Not Move From Cold When Engine Is Hot > Page 12409 Temperature Gauge: Testing and Inspection Gauge Reads Low 1. Ensure terminals are clean and connections are tight. 2. Remove lead at sensor, measure resistance using an ohmmeter. 3. At 104 degrees F resistance should be approximately 1200-1350 ohms, and at 125 degrees F resistance should be approximately 53-55 ohms. 4. If resistance is not within specifications, replace sensor. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Temperature Sensor (Gauge) > Component Information > Locations Temperature Sensor (Gauge): Locations Engine Side, LH LH cylinder head, near number one spark plug. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Temperature Warning Lamp/Indicator, Engine Cooling > Component Information > Description and Operation Temperature Warning Lamp/Indicator: Description and Operation A bi-metal temperature switch located in the cylinder head controls the operation of a temperature indicator light. If the engine cooling system is not functioning properly and/or coolant temperature exceeds a predetermined value, the warning light will illuminate. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Temperature Warning Lamp/Indicator, Engine Cooling > Component Information > Description and Operation > Page 12416 Temperature Warning Lamp/Indicator: Testing and Inspection If the light is not lit when the engine is being cranked, check for a burned out bulb, an open in the light circuit, or a defective ignition switch. If the light is lit when the engine is running, check the wiring between light and switch for a ground, defective temperature switch, or overheated cooling system. As a test circuit to check whether the bulb is functioning properly, connect a wire from the ground terminal of the ignition switch to the temperature indicator light circuit. When the ignition is in the START (engine cranking) position, the ground terminal is grounded inside the switch and the bulb will be lit. When the engine is started and the ignition switch is in the ON position, the test circuit is opened and the bulb is then controlled by the temperature switch. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Transmission Shift Position Indicator Lamp > Component Information > Technical Service Bulletins > Instruments - Reduced PRNDL Display Visibility Transmission Shift Position Indicator Lamp: Technical Service Bulletins Instruments - Reduced PRNDL Display Visibility Bulletin No.: 02-08-42-004A Date: March 30, 2007 INFORMATION Subject: PRNDL Display Reduced Visibility For Approximately One Minute Models: 2007 and Prior Passenger Cars and Trucks (Including Saturn) 2007 and Prior HUMMER H2, H3 2005-2007 Saab 9-7X with Automatic Headlamp Control and Vacuum Fluorescent PRNDL Indicator Instrument Panel Cluster Supercede: This bulletin is being revised to include additional models and model years. Please discard Corporate Bulletin Number 02-08-42-0004 (Section 08 - Body and Accessories). After backing the vehicle out of a garage or dark environment into a daylight environment, the PRNDL display has reduced visibility for approximately one minute. While the vehicle is parked in a dark environment, the sensor for the automatic headlamp/driving lamps senses that it is dark. When the key is turned to the run/start position, the automatic headlamp module will turn all driving lamps, the instrument panel cluster and PRNDL display ON in the night-time mode. The night-time mode intensity of the instrument panel lamps and PRNDL display is controlled by the automatic headlamp module and can be dimmed further by the customer using the dimming control of the headlamp switch. When the customer then moves the vehicle from the dark environment into the bright sunlight, it will take approximately one minute before the headlamp control module recognizes this as true daylight and not just a bright overhead street lamp shining on the sensor. The headlamp control module will then turn the headlamps off and restore the instrument panel and PRNDL display to full brilliance. Without the time delay, the automatic headlamp control module would switch to the night mode (turn on all driving lamps, instrument panel lamps and PRNDL display would dim) each time the vehicle was driven under an overpass or other darkened environment. This is a normal condition and no repair should be attempted. Ensure the instrument panel backlighting control is in the full bright position. This will help alleviate the condition. You may demonstrate to the customer what happens by placing a repair order over the automatic headlamp control light sensor, which will cause the automatic headlamp control module to switch to the night mode in approximately one minute. All driving lamps will come ON, the instrument panel backlight will be dim, and the PRNDL display will also dim to the night setting in conjunction with the position of the headlamp switch dimming control. Demonstrate to the customer the variance in the instrument panel backlighting and PRNDL display while adjusting the headlamp switch dimming control to both ends of its allowable range. Advise the customer to keep the headlight switch dimming control in the highest position to allow viewing of the PRNDL display in a bright environment. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Vacuum Gauge/Economy Meter > Component Information > Description and Operation Vacuum Gauge/Economy Meter: Description and Operation This system actually monitors the engine vacuum just like the vacuum gauge, but registers only low vacuum readings. The light on the instrument panel warns the vehicle operator when engine manifold vacuum drops below the economical limit. Switch operation is similar to that of the oil pressure indicating light, except the switch opens when vacuum pressure, rather than oil pressure, is applied. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Vacuum Gauge/Economy Meter > Component Information > Description and Operation > Page 12424 Vacuum Gauge/Economy Meter: Testing and Inspection The fuel economy warning light should go on when the ignition is turned on. If it does not light, disconnect the wire from the fuel economy vacuum switch connector and ground the wire to the frame or cylinder block. If the warning light still does not go on, check for burned out indicating bulb or an open in the harness between the vacuum switch and instrument panel. If the warning light goes on, circuit is functioning and the vacuum switch should be checked for proper ground. Remove and clean the mounting bracket screws and the mounting surfaces. If the warning light remains lit when it normally should be out, check vacuum hose to vacuum switch for damage or plugged condition. If system still does not operate correctly, perform the following steps: 1. Disconnect electrical connector and vacuum tube from switch. 2. Connect a self-powered test light to the switch electrical connector and to the vacuum gauge mounting bracket. 3. With vacuum applied, test light should be off. 4. With no vacuum to the vacuum switch, test light should be on. 5. Replace switch if test light did not function as specified. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Instrument Panel, Gauges and Warning Indicators > Volt Meter Gauge > Component Information > Testing and Inspection Volt Meter Gauge: Testing and Inspection To check voltmeter, turn ignition switch and headlights on with engine off. Pointer should move to 12.5 volts. If no needle movement is observed, check connections from battery to circuit breaker. If connections are tight and clean, check wire continuity. If wire continuity is satisfactory, replace the voltmeter. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Backup Lamp > Backup Lamp Switch > Component Information > Locations Backup Lamp Switch: Locations 5-Speed Manual Transmission (MW3) 5-Speed Manual Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Lamp > Brake Lamp Relay > Component Information > Locations Brake Lamp Relay: Locations Underhood Fuse-Relay Center In Underhood Fuse-Relay Center. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Locations Brake Light Switch: Locations This article has been updated with Bulletin No.: 76-81-06. TCC/STOPLAMP SWITCH The TCC/Stoplamp Switch at top of Brake Pedal. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions Brake Light Switch: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12442 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12443 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12444 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12445 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12446 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12447 Brake Light Switch: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12448 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12449 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12450 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12451 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12452 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12453 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12454 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12455 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12456 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12457 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12458 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12459 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12460 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12461 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12462 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12463 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12464 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12465 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12466 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12467 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12468 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12469 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12470 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12471 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12472 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12473 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12474 Brake Light Switch: Electrical Diagrams Antilock Brakes Four Wheel Antilock Brakes (4WAL) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12475 Fig. 25 Four Wheel Anti-Lock Brake Wiring Circuit. Four wheel anti-lock brake wiring circuit. Additional Wiring Diagrams For additional Lighting and Horns wiring diagrams, See: Diagrams/Electrical Diagrams Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12476 Brake Switch And Solenoids Cruise Control Wiring Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12477 Fig. 9 Cruise Control System Wiring Circuit (Part 1 Of 2). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12478 Fig. 9 Cruise Control System Wiring Circuit (Part 2 Of 2). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12479 Turn And Hazard Lamps/Park And Marker Lamps (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12480 Antilock Brakes Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12481 Turn And Hazard Lamps/Park And Marker Lamps (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12482 Turn And Hazard Lamps/Park And Marker Lamps (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12483 Cruise Control (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Page 12484 Brake Light Switch: Adjustments Stop Lamp Switch Remove or Disconnect 1. Negative battery cable. 2. Disable SIR. 3. Retainer from brake pedal pin. Use snap ring pliers. 4. Switch by unsnapping from pushrod. 5. Electrical connector from switch. Install or Connect 1. Electrical connector into switch. 2. Switch by snapping it onto pushrod. 3. Retainer onto brake pedal pin. Use 11mm (7/16 inch) socket to push new clip on pin. 4. Negative battery cable. 5. Enable SIR. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Page 12485 Brake Light Switch: Service and Repair Stop Lamp Switch Remove or Disconnect 1. Negative battery cable. 2. Disable SIR. 3. Retainer from brake pedal pin. Use snap ring pliers. 4. Switch by unsnapping from pushrod. 5. Electrical connector from switch. Install or Connect 1. Electrical connector into switch. 2. Switch by snapping it onto pushrod. 3. Retainer onto brake pedal pin. Use 11mm (7/16 inch) socket to push new clip on pin. 4. Negative battery cable. 5. Enable SIR. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Cargo Lamp > Cargo Lamp Switch > Component Information > Locations Cargo Lamp Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Cargo Lamp > Cargo Lamp Switch > Component Information > Locations > Page 12490 Cargo Lamp Switch: Diagrams C411: Cross Body HARN To Cargo Lamp HARN C212: PWR Seat To Cross Body HARN, Body HARN To Cross Body HARN, Cargo Lamp SW Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions Center Mounted Brake Lamp: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12495 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12496 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12497 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12498 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12499 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12500 Center Mounted Brake Lamp: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12501 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12502 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12503 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12504 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12505 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12506 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12507 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12508 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12509 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12510 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12511 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12512 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12513 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12514 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12515 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12516 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12517 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12518 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12519 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12520 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12521 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12522 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12523 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12524 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12525 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Center Mounted Brake Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12526 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Clearance Lamp > Component Information > Locations Rear Clearance Lamps (With Dual Rear Wheels) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Courtesy Lamp > Glove Box Lamp > Component Information > Locations Glove Box Lamp: Locations In I/P Compartment Box Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Daytime Running Lamp > Daytime Running Lamp Control Unit > Component Information > Locations Daytime Running Lamp Control Unit: Locations This article has been updated with Bulletin No.: 76-81-06. DAYTIME RUNNING LAMPS (DRL) MODULE The Daytime Running Lamps (DRL) Module is located under LH side of Instrument Panel (I/P), taped on I/P harness. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Daytime Running Lamp > Daytime Running Lamp Control Unit > Component Information > Locations > Page 12538 DRL Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Daytime Running Lamp > Daytime Running Lamp Diode Assembly > Component Information > Locations Daytime Running Lamp Diode Assembly: Locations This article has been updated with Bulletin No.: 76-81-06. DAYTIME RUNNING LAMPS (DRL) DIODE Auxiliary Battery Wiring 1. DRL Diode 1 is located in Underhood Fuse Relay Center. The Underhood Fuse Relay Center is located in the LR of Engine Compartment on Fender. 2. DRL Diode D202 is located in the Instrument Panel (I/P) harness, approx. 11 cm from Crossbody harness Breakout towards Park Brake Switch. NOTE: The OEM service manual does not provide a location image for D202. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Daytime Running Lamp > Daytime Running Lamp Diode Assembly > Component Information > Locations > Page 12542 Daytime Running Lamp Module Instrument Panel Wiring, LH Side 3. DRL Diode D203 is located in the Instrument Panel (I/P) harness, RH side of Steering Column Support, mounted to I/P Support. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Daytime Running Lamp > Daytime Running Lamp Relay > Component Information > Locations Convenience Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Daytime Running Lamp > Daytime Running Lamp Relay > Component Information > Locations > Page 12546 Daytime Running Lamp Relay: Diagrams Convenience Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Daytime Running Lamp > Daytime Running Lamp Relay > Component Information > Locations > Page 12547 Convenience Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Dimmer Switch > Component Information > Technical Service Bulletins > IP Dimmer Control - Proper Setting Dimmer Switch: Technical Service Bulletins IP Dimmer Control - Proper Setting File In Section: 08 - Body and Accessories Bulletin No.: 99-08-42-009 Date: November, 1999 INFORMATION Subject: Proper Setting of I/P Dimmer Control to View PRNDL Display with Automatic Headlamp Control Models: 2000 and Prior All Passenger Cars and Trucks With Automatic Headlamp Control and Electronic PRNDL Display Under certain conditions, if the instrument panel dimmer control is turned relatively low, the PRNDL will not be visible until the automatic headlamp control turns the headlamps off and the daytime running lamps (DRL) are turned back on. Such a condition may be if the vehicle is first started in an environment where the headlamp control turns on the headlamps and then the vehicle is driven out into a brighter environment (for example, when a vehicle is backed out of a dark garage into the bright sunlight). This condition is normal and any repair attempt will not be successful. Demonstrate this condition to the customer using the service lane and then turn the instrument panel dimmer control to a higher setting. This will enable the driver to see the PRNDL display Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Dome Lamp > Dome Lamp Switch > Component Information > Locations Dome Lamp Switch: Locations On center of I/P Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Door Switch > Component Information > Locations > Cargo Door Jamb Switch Door Switch: Locations Cargo Door Jamb Switch On RH rear Cargo Door Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 12560 Door Switch: Locations Door Jamb Switch, Cargo Upper RH Body Opening incorporated in Cargo Door Contractor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 12561 Door Switch: Locations Door Jamb Switch, LH Front At LH end of I/P Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 12562 Door Switch: Locations Door Jamb Switch, LH Rear Center of LH "B" Pillar Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 12563 Door Switch: Locations Cargo Door Jamb Switch On RH rear Cargo Door Door Jamb Switch, Cargo Upper RH Body Opening incorporated in Cargo Door Contractor Door Jamb Switch, LH Front At LH end of I/P Door Jamb Switch, LH Rear Center of LH "B" Pillar Rear Door Jamb Switch Wiring Door Jamb Switch, RH Front At RH end of I/P Door Jamb Switch, RH Rear Center of RH "B" Pillar Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Fog/Driving Lamp > Fog/Driving Lamp Relay > Component Information > Locations Convenience Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Fog/Driving Lamp > Fog/Driving Lamp Switch > Component Information > Locations Cargo Lamp Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Fog/Driving Lamp > Fog/Driving Lamp Switch > Component Information > Locations > Page 12571 Fog Lamp Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Hazard Warning Lamps > Hazard Warning Flasher > Component Information > Locations Hazard Warning Flasher: Locations Convenience Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Hazard Warning Lamps > Hazard Warning Flasher > Component Information > Locations > Page 12576 Convenience Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Headlamp > Headlamp Dimmer Switch > Component Information > Locations > Component Locations Headlamp Dimmer Switch: Component Locations Part of the multifunction switch. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Headlamp > Headlamp Dimmer Switch > Component Information > Locations > Component Locations > Page 12582 Instrument Panel Wiring, LH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Headlamp > Headlamp Dimmer Switch > Component Information > Locations > Page 12583 Headlamp Dimmer Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Headlamp > Headlamp Lens > Component Information > Technical Service Bulletins > Lighting - Headlamp Polycarbonate Lens Damage Prevention Headlamp Lens: Technical Service Bulletins Lighting - Headlamp Polycarbonate Lens Damage Prevention INFORMATION Bulletin No.: 02-08-42-001D Date: June 21, 2010 Subject: Headlamp Lens Overheating When Covered and Chemical Damage to Exterior Polycarbonate Headlamp Lenses Models: 2011 and Prior GM Passenger Cars and Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add model years and to revise the warning statements. Please discard Corporate Bulletin Number 02-08-42-001C (Section 08 - Body and Accessories). The bulletin is being issued to make dealers and customers aware of chemical damage that may be caused to exterior polycarbonate headlamp lenses. Most late model vehicles have these types of headlamp lenses. This material is used because of its temperature and high impact resistance. A variety of chemicals can cause crazing or cracking of the headlamp lens. Headlamp lenses are very sensitive. Care should be exercised to avoid contact with all exterior headlamp lenses when treating a vehicle with any type of chemical, such as those recommended for rail dust removal. Rubbing compound, grease tar and oil removers, tire cleaners, cleaner waxes and even car wash soaps in too high a concentration may also attribute to this condition. This could result in the need to replace the entire headlamp housing. Warning Use only lukewarm or cold water, a soft cloth and a car washing soap to clean exterior lamps and lenses. Also, crazing or deformations of the lens may occur if a shop mat or fender cover is draped over the fender and covers a portion or all of the headlamp assembly while the DRL or headlamps are on. This action restricts the amount of heat dissipated by the headlamps. Warning Care should be taken to not cover headlamps with shop mats or fender covers if the vehicle is being serviced with the headlamps or DRL illuminated. Covering an illuminated lamp can cause excessive heat build up and crazing/deformation of the lens may occur. The degradation of the lens can be unnoticeable at first and eventually become hairline cracks in the lens. In extreme cases, it could cause the lens to deform. This damage can also be caused by aftermarket shields that are often tinted in color. Once a heat buildup is generated by the headlamp, a degradation of the headlamp lens begins. This degradation of the lens can be unnoticeable at first and eventually manifest as spider cracks. In more extreme cases, it will begin to melt the lens of the headlamp. Notice Headlamps damaged by chemicals, improper cleaning, or overheating due to being covered are not covered under the new vehicle warranty. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Horn > Horn Relay > Component Information > Locations Underhood Fuse-Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Horn > Horn Switch > Component Information > Locations Horn Switch: Locations Top of Steering Column under Steering Wheel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Horn > Horn Switch > Component Information > Service and Repair > Horn Contact Replacement (Plunger Switch) Horn Switch: Service and Repair Horn Contact Replacement (Plunger Switch) REMOVAL Remove or disconnect the following: 1. Negative battery cable. 2. Disable the SIR system. See: Body and Frame/Interior Moulding / Trim/Dash Board / Instrument Panel/Air Bag(s) Arming and Disarming/Service and Repair 3. Inflator module. See: Restraint Systems/Air Bag Systems/Air Bag/Service and Repair 4. Horn contact from steering column. See: INSTALLATION CAUTION: Always use the correct fastener in the proper location. When you replace a fastener, use ONLY the exact part number for that application. The manufacturer will call out those fasteners that require a replacement after removal. The manufacturer will also call out the fasteners that require thread lockers or thread sealant. UNLESS OTHERWISE SPECIFIED, do not use supplemental coatings (paints, greases, or other corrosion Inhibitors) on threaded fasteners or fastener joint interfaces. Generally, such coatings adversely affect the fastener torque and joint clamping force, and may damage the fastener. When you install fasteners, use the correct tightening sequence and specifications. Following these instructions can help you avoid damage to parts and systems. Install or connect the following: 1. Horn contact into steering column. See: 2. Inflator module to the steering wheel. See: Restraint Systems/Air Bag Systems/Air Bag/Service and Repair 3. Negative battery cable. 4. Enable the SIR system. See: Body and Frame/Interior Moulding / Trim/Dash Board / Instrument Panel/Air Bag(s) Arming and Disarming/Service and Repair Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Horn > Horn Switch > Component Information > Service and Repair > Horn Contact Replacement (Plunger Switch) > Page 12597 Horn Switch: Service and Repair Horn Pad Assembly Replacement REMOVAL Remove or disconnect the following: 1. Negative battery cable. 2. Pull four corners of horn pad from steering wheel. 3. Ground wire. 4. Horn wire assembly. INSTALLATION Install or connect the following: 1. Horn wire assembly. 2. Ground wire. 3. Push horn pad assembly on steering wheel. 4. Negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Interior Lighting Module > Component Information > Locations Interior Lighting Module: Locations View: Under Center Of Instrument Panel Interior Lamp Control Module, Remote Control Door Lock Receiver Manufacturer supplied 2 different possible locations. Look for 5 wire connector with wire colors: gray, white, orange, pink & black. #PIT3819: Location of Interior Lamp Control Module - keywords control dim dome electrical entry ground illumination inoperative keyless lens light remort resistor RKE short - (Dec 23, 2005) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Interior Lighting Module > Component Information > Locations > Page 12601 Subject: Location of Interior Lamp Control Module. Models: 1995-2000 Chevrolet C/K Trucks, Suburban and Tahoe 1995-2000 GMC Yukon and C/K Trucks Classic Body Style Only The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this P1. Condition/Concern When diagnosing a dome lamp concern on one of the vehicles listed above, you may be unable to locate the Interior Lamp Control Module that is called out in the Service Manual. Recommendation/lnstructions: Only vehicles without Remote Keyless Entry (RPO AUO) will be equipped with a Interior Lamp Control Module. If the vehicle is equipped with (RKE) Remote Keyless Entry, the illumination module is a internal part of RKE Module. Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Interior Lighting Module > Component Information > Locations > Page 12602 Interior Lamp Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Map Light > Component Information > Locations > Overhead Console Lamps Map Light: Locations Overhead Console Lamps In Roof Console Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Map Light > Component Information > Locations > Overhead Console Lamps > Page 12607 Four-Wheel Indicator Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Marker Lamp > Component Information > Locations > Endgate Marker Lamps Endgate Marker Lamps Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Marker Lamp > Component Information > Locations > Endgate Marker Lamps > Page 12612 Forward Lamps Harness, RH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Technical Service Bulletins > Lighting - Exterior Lamp Condensation and Replacement Parking Lamp: Technical Service Bulletins Lighting - Exterior Lamp Condensation and Replacement INFORMATION Bulletin No.: 01-08-42-001H Date: January 05, 2011 Subject: Exterior Lamp Condensation and Replacement Guidelines Models: 2011 and Prior GM Passenger Cars and Trucks (including Saturn) Supercede: This bulletin is being revised to add the 2011 model year. Please discard Corporate Bulletin Number 01-08-42-001G (Section 08 - Body and Accessories). The following information is being provided to better define the causes of condensation in exterior lamps and includes guidelines for determining the difference between a lamp with a normal atmospheric condition (condensation) and a lamp with a water leak. Some exterior lamps, such as cornering, turn signal, backup, headlamps or tail lamps may exhibit very small droplets of water, a fine mist or white fog (condensation) on the inside of the lamp lens. This may be more noticeable on lamps with "multi-lens" designs and may be normal during certain weather conditions. Condensation occurs when the air inside the lamp assembly, through atmospheric changes, reaches the "dew point". When this takes place, the moisture in the air within the lamp assembly condenses, creating a fine mist or white fog on the inside surface of the lamp lens. Most exterior lamps on General Motors vehicles use a vented design and feature a replaceable bulb assembly. They are designed to remove any accumulated moisture vapor by expelling it through a vent system. The vent system operates at all times, however, it is most effective when the lamps are ON or when the vehicle is in motion. Depending on the size, shape and location of the lamp on the vehicle, and the atmospheric conditions occurring, the amount of time required to clear the lamp may vary from 2 to 6 hours. Completely sealed headlamp assemblies (sealed beams) are still used on a limited number of models being manufactured today. These lamps require the replacement of the complete lamp assembly if a bulb filament burns out. Condensation 2006 TrailBlazer Shown A Fine Mist or White Fog on the Inside Surface of the Lamp Lens Occurring After a Period of High Humidity - May be located primarily in the lens corners (near the vents) and SHOULD NOT cover more than half the lens surface. - The condition should clear of moisture when the vehicle is parked in a dry environment, or when the vehicle is driven with the lights ON. - A comparison of the equivalent lamp on the opposing side of the vehicle indicates a SIMILAR performance. If the above conditions are noted, the customer should be advised that replacement of a lamp assembly may not correct this condition. Water Leak New Style Pickup Shown Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Technical Service Bulletins > Lighting - Exterior Lamp Condensation and Replacement > Page 12617 Numerous & Various Size Drops of Water Collecting on the Inside Surface of the Lamp Lens After the Vehicle Has Been Exposed to Rain or a Car Washing Environment - A condition that covers more than half the surface of the lamp lens. - An accumulation of water in the bottom of the lamp assembly. - A condition that WON'T clear when the vehicle is parked in a dry environment, or when the vehicle is driven with the lights ON. - A comparison of the equivalent lamp on the opposing side of the vehicle indicates a different performance. Any of the above conditions would indicate the need to service the lens or lamp assembly. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Locations > LF Park and Turn Signal Lamp Harness Forward Lamps Harness, LH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Locations > LF Park and Turn Signal Lamp Harness > Page 12620 Parking Lamp: Locations Park Lamp Switch HEADLAMP AND PANEL DIMMER SWITCH Instrument Panel Wiring, LH Side The Park Lamp Switch is combined with the Headlamp and Panel Dimmer Switch. The Headlamp and Panel Dimmer Switch is located in the lower LH side of Instrument Panel (I/P). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Locations > LF Park and Turn Signal Lamp Harness > Page 12621 Forward Lamps Harness, RH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions Parking Lamp: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12624 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12625 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12626 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12627 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12628 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12629 Parking Lamp: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12630 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12631 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12632 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12633 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12634 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12635 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12636 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12637 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12638 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12639 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12640 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12641 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12642 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12643 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12644 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12645 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12646 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12647 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12648 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12649 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12650 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12651 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12652 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12653 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12654 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Parking Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12655 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Relays and Modules - Lighting and Horns > Brake Lamp Relay > Component Information > Locations Brake Lamp Relay: Locations Underhood Fuse-Relay Center In Underhood Fuse-Relay Center. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Relays and Modules - Lighting and Horns > Daytime Running Lamp Control Unit > Component Information > Locations Daytime Running Lamp Control Unit: Locations This article has been updated with Bulletin No.: 76-81-06. DAYTIME RUNNING LAMPS (DRL) MODULE The Daytime Running Lamps (DRL) Module is located under LH side of Instrument Panel (I/P), taped on I/P harness. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Relays and Modules - Lighting and Horns > Daytime Running Lamp Control Unit > Component Information > Locations > Page 12663 DRL Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Relays and Modules - Lighting and Horns > Daytime Running Lamp Relay > Component Information > Locations Convenience Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Relays and Modules - Lighting and Horns > Daytime Running Lamp Relay > Component Information > Locations > Page 12667 Daytime Running Lamp Relay: Diagrams Convenience Center (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Relays and Modules - Lighting and Horns > Daytime Running Lamp Relay > Component Information > Locations > Page 12668 Convenience Center (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Relays and Modules - Lighting and Horns > Fog/Driving Lamp Relay > Component Information > Locations Convenience Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Relays and Modules - Lighting and Horns > Horn Relay > Component Information > Locations Underhood Fuse-Relay Center Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Relays and Modules - Lighting and Horns > Interior Lighting Module > Component Information > Locations Interior Lighting Module: Locations View: Under Center Of Instrument Panel Interior Lamp Control Module, Remote Control Door Lock Receiver Manufacturer supplied 2 different possible locations. Look for 5 wire connector with wire colors: gray, white, orange, pink & black. #PIT3819: Location of Interior Lamp Control Module - keywords control dim dome electrical entry ground illumination inoperative keyless lens light remort resistor RKE short - (Dec 23, 2005) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Relays and Modules - Lighting and Horns > Interior Lighting Module > Component Information > Locations > Page 12678 Subject: Location of Interior Lamp Control Module. Models: 1995-2000 Chevrolet C/K Trucks, Suburban and Tahoe 1995-2000 GMC Yukon and C/K Trucks Classic Body Style Only The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this P1. Condition/Concern When diagnosing a dome lamp concern on one of the vehicles listed above, you may be unable to locate the Interior Lamp Control Module that is called out in the Service Manual. Recommendation/lnstructions: Only vehicles without Remote Keyless Entry (RPO AUO) will be equipped with a Interior Lamp Control Module. If the vehicle is equipped with (RKE) Remote Keyless Entry, the illumination module is a internal part of RKE Module. Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Relays and Modules - Lighting and Horns > Interior Lighting Module > Component Information > Locations > Page 12679 Interior Lamp Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Backup Lamp Switch > Component Information > Locations Backup Lamp Switch: Locations 5-Speed Manual Transmission (MW3) 5-Speed Manual Transmission Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Locations Brake Light Switch: Locations This article has been updated with Bulletin No.: 76-81-06. TCC/STOPLAMP SWITCH The TCC/Stoplamp Switch at top of Brake Pedal. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions Brake Light Switch: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12689 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12690 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12691 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12692 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12693 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12694 Brake Light Switch: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12695 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12696 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12697 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12698 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12699 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12700 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12701 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12702 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12703 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12704 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12705 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12706 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12707 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12708 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12709 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12710 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12711 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12712 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12713 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12714 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12715 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12716 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12717 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12718 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12719 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12720 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12721 Brake Light Switch: Electrical Diagrams Antilock Brakes Four Wheel Antilock Brakes (4WAL) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12722 Fig. 25 Four Wheel Anti-Lock Brake Wiring Circuit. Four wheel anti-lock brake wiring circuit. Additional Wiring Diagrams For additional Lighting and Horns wiring diagrams, See: Diagrams/Electrical Diagrams Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12723 Brake Switch And Solenoids Cruise Control Wiring Circuit Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12724 Fig. 9 Cruise Control System Wiring Circuit (Part 1 Of 2). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12725 Fig. 9 Cruise Control System Wiring Circuit (Part 2 Of 2). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12726 Turn And Hazard Lamps/Park And Marker Lamps (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12727 Antilock Brakes Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12728 Turn And Hazard Lamps/Park And Marker Lamps (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12729 Turn And Hazard Lamps/Park And Marker Lamps (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Diagram Information and Instructions > Page 12730 Cruise Control (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Page 12731 Brake Light Switch: Adjustments Stop Lamp Switch Remove or Disconnect 1. Negative battery cable. 2. Disable SIR. 3. Retainer from brake pedal pin. Use snap ring pliers. 4. Switch by unsnapping from pushrod. 5. Electrical connector from switch. Install or Connect 1. Electrical connector into switch. 2. Switch by snapping it onto pushrod. 3. Retainer onto brake pedal pin. Use 11mm (7/16 inch) socket to push new clip on pin. 4. Negative battery cable. 5. Enable SIR. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Brake Light Switch > Component Information > Diagrams > Page 12732 Brake Light Switch: Service and Repair Stop Lamp Switch Remove or Disconnect 1. Negative battery cable. 2. Disable SIR. 3. Retainer from brake pedal pin. Use snap ring pliers. 4. Switch by unsnapping from pushrod. 5. Electrical connector from switch. Install or Connect 1. Electrical connector into switch. 2. Switch by snapping it onto pushrod. 3. Retainer onto brake pedal pin. Use 11mm (7/16 inch) socket to push new clip on pin. 4. Negative battery cable. 5. Enable SIR. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Cargo Lamp Switch > Component Information > Locations Cargo Lamp Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Cargo Lamp Switch > Component Information > Locations > Page 12736 Cargo Lamp Switch: Diagrams C411: Cross Body HARN To Cargo Lamp HARN C212: PWR Seat To Cross Body HARN, Body HARN To Cross Body HARN, Cargo Lamp SW Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Dome Lamp Switch > Component Information > Locations Dome Lamp Switch: Locations On center of I/P Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Door Switch > Component Information > Locations > Cargo Door Jamb Switch Door Switch: Locations Cargo Door Jamb Switch On RH rear Cargo Door Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 12744 Door Switch: Locations Door Jamb Switch, Cargo Upper RH Body Opening incorporated in Cargo Door Contractor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 12745 Door Switch: Locations Door Jamb Switch, LH Front At LH end of I/P Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 12746 Door Switch: Locations Door Jamb Switch, LH Rear Center of LH "B" Pillar Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Door Switch > Component Information > Locations > Cargo Door Jamb Switch > Page 12747 Door Switch: Locations Cargo Door Jamb Switch On RH rear Cargo Door Door Jamb Switch, Cargo Upper RH Body Opening incorporated in Cargo Door Contractor Door Jamb Switch, LH Front At LH end of I/P Door Jamb Switch, LH Rear Center of LH "B" Pillar Rear Door Jamb Switch Wiring Door Jamb Switch, RH Front At RH end of I/P Door Jamb Switch, RH Rear Center of RH "B" Pillar Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Fog/Driving Lamp Switch > Component Information > Locations Cargo Lamp Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Fog/Driving Lamp Switch > Component Information > Locations > Page 12751 Fog Lamp Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Headlamp Dimmer Switch > Component Information > Locations > Component Locations Headlamp Dimmer Switch: Component Locations Part of the multifunction switch. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Headlamp Dimmer Switch > Component Information > Locations > Component Locations > Page 12756 Instrument Panel Wiring, LH Side Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Headlamp Dimmer Switch > Component Information > Locations > Page 12757 Headlamp Dimmer Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Horn Switch > Component Information > Locations Horn Switch: Locations Top of Steering Column under Steering Wheel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Horn Switch > Component Information > Service and Repair > Horn Contact Replacement (Plunger Switch) Horn Switch: Service and Repair Horn Contact Replacement (Plunger Switch) REMOVAL Remove or disconnect the following: 1. Negative battery cable. 2. Disable the SIR system. See: Body and Frame/Interior Moulding / Trim/Dash Board / Instrument Panel/Air Bag(s) Arming and Disarming/Service and Repair 3. Inflator module. See: Restraint Systems/Air Bag Systems/Air Bag/Service and Repair 4. Horn contact from steering column. See: INSTALLATION CAUTION: Always use the correct fastener in the proper location. When you replace a fastener, use ONLY the exact part number for that application. The manufacturer will call out those fasteners that require a replacement after removal. The manufacturer will also call out the fasteners that require thread lockers or thread sealant. UNLESS OTHERWISE SPECIFIED, do not use supplemental coatings (paints, greases, or other corrosion Inhibitors) on threaded fasteners or fastener joint interfaces. Generally, such coatings adversely affect the fastener torque and joint clamping force, and may damage the fastener. When you install fasteners, use the correct tightening sequence and specifications. Following these instructions can help you avoid damage to parts and systems. Install or connect the following: 1. Horn contact into steering column. See: 2. Inflator module to the steering wheel. See: Restraint Systems/Air Bag Systems/Air Bag/Service and Repair 3. Negative battery cable. 4. Enable the SIR system. See: Body and Frame/Interior Moulding / Trim/Dash Board / Instrument Panel/Air Bag(s) Arming and Disarming/Service and Repair Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Horn Switch > Component Information > Service and Repair > Horn Contact Replacement (Plunger Switch) > Page 12763 Horn Switch: Service and Repair Horn Pad Assembly Replacement REMOVAL Remove or disconnect the following: 1. Negative battery cable. 2. Pull four corners of horn pad from steering wheel. 3. Ground wire. 4. Horn wire assembly. INSTALLATION Install or connect the following: 1. Horn wire assembly. 2. Ground wire. 3. Push horn pad assembly on steering wheel. 4. Negative battery cable. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Turn Signal Switch > Component Information > Diagrams > C266 Harness Connector C266: I/P Harness To Steering Column Harness Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Turn Signal Switch > Component Information > Diagrams > C266 Harness Connector > Page 12768 Turn Signal Switch: Diagrams C266 Pinout Description C266: I/P Harness To Steering Column Harness (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Sensors and Switches - Lighting and Horns > Turn Signal Switch > Component Information > Diagrams > C266 Harness Connector > Page 12769 C266: I/P Harness To Steering Column Harness (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Technical Service Bulletins > Lighting - Exterior Lamp Condensation and Replacement Tail Lamp: Technical Service Bulletins Lighting - Exterior Lamp Condensation and Replacement INFORMATION Bulletin No.: 01-08-42-001H Date: January 05, 2011 Subject: Exterior Lamp Condensation and Replacement Guidelines Models: 2011 and Prior GM Passenger Cars and Trucks (including Saturn) Supercede: This bulletin is being revised to add the 2011 model year. Please discard Corporate Bulletin Number 01-08-42-001G (Section 08 - Body and Accessories). The following information is being provided to better define the causes of condensation in exterior lamps and includes guidelines for determining the difference between a lamp with a normal atmospheric condition (condensation) and a lamp with a water leak. Some exterior lamps, such as cornering, turn signal, backup, headlamps or tail lamps may exhibit very small droplets of water, a fine mist or white fog (condensation) on the inside of the lamp lens. This may be more noticeable on lamps with "multi-lens" designs and may be normal during certain weather conditions. Condensation occurs when the air inside the lamp assembly, through atmospheric changes, reaches the "dew point". When this takes place, the moisture in the air within the lamp assembly condenses, creating a fine mist or white fog on the inside surface of the lamp lens. Most exterior lamps on General Motors vehicles use a vented design and feature a replaceable bulb assembly. They are designed to remove any accumulated moisture vapor by expelling it through a vent system. The vent system operates at all times, however, it is most effective when the lamps are ON or when the vehicle is in motion. Depending on the size, shape and location of the lamp on the vehicle, and the atmospheric conditions occurring, the amount of time required to clear the lamp may vary from 2 to 6 hours. Completely sealed headlamp assemblies (sealed beams) are still used on a limited number of models being manufactured today. These lamps require the replacement of the complete lamp assembly if a bulb filament burns out. Condensation 2006 TrailBlazer Shown A Fine Mist or White Fog on the Inside Surface of the Lamp Lens Occurring After a Period of High Humidity - May be located primarily in the lens corners (near the vents) and SHOULD NOT cover more than half the lens surface. - The condition should clear of moisture when the vehicle is parked in a dry environment, or when the vehicle is driven with the lights ON. - A comparison of the equivalent lamp on the opposing side of the vehicle indicates a SIMILAR performance. If the above conditions are noted, the customer should be advised that replacement of a lamp assembly may not correct this condition. Water Leak New Style Pickup Shown Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Technical Service Bulletins > Lighting - Exterior Lamp Condensation and Replacement > Page 12774 Numerous & Various Size Drops of Water Collecting on the Inside Surface of the Lamp Lens After the Vehicle Has Been Exposed to Rain or a Car Washing Environment - A condition that covers more than half the surface of the lamp lens. - An accumulation of water in the bottom of the lamp assembly. - A condition that WON'T clear when the vehicle is parked in a dry environment, or when the vehicle is driven with the lights ON. - A comparison of the equivalent lamp on the opposing side of the vehicle indicates a different performance. Any of the above conditions would indicate the need to service the lens or lamp assembly. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Locations > Tail, Stop, Turn Signal and Backup Lamp, LH Tail Lamp: Locations Tail, Stop, Turn Signal and Backup Lamp, LH LH rear comer of vehicle Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Locations > Tail, Stop, Turn Signal and Backup Lamp, LH > Page 12777 Tail Lamp: Locations Tail, Stop, Turn Signal and Backup Lamp, RH LH rear comer of vehicle Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Locations > Tail, Stop, Turn Signal and Backup Lamp, LH > Page 12778 Tail Lamp: Locations Taillamp Rear Lamps Wiring Rear Lamps Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions Tail Lamp: Diagram Information and Instructions Abbreviation A/C Air Conditioning CCM Central Control Module CKT Circuit CONN Connector EBCM Electronic Brake Control Module EBTCM Electronic Brake and Traction Control Module ECM Engine Control Module HARN Harness I/P Instrument Panel LH Left Hand PCM Powertrain Control Module RH Right Hand TERM Terminal Cell References CELL REFERENCES General Motors vehicles often use "CELL" references in their electrical wiring diagrams. These references are used in the Original Equipment Manual to refer to a section in the manual and not a specific diagram(s). GM Sample Diagram W/ Cell Reference For instance, in the diagram illustrated "Cell 20" is not a reference to another diagram but a reference to "Section 20" in the OE manual. In the example, "Section 20" is the engine control section of the manual. To navigate through these "Cell" references start at the vehicle level and go to: Diagrams / Electrical Diagrams - for a complete list of the diagrams available for the vehicle. Choose the system you are working on and view those diagrams. Note: If unsure of the system - try utilizing the search feature. Type a component in the search feature that belongs to the system and when the results are displayed note the path displayed. This will show the system the component belongs in. Electrostatic Discharge (ESD Sensitive Devices) All Electrostatic Discharge (ESD) sensitive components are Solid State and the following information applies to them. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12781 ESD Symbol Typical Schematic The ESD symbol is used on schematics to indicate which components are ESD sensitive. When handling any electronic part, the service technician should follow the guidelines below to reduce any possible electrostatic charge build-up on the service technician's body and inadvertent discharge to the electronic part. If it is not known whether or not a component is ESD sensitive, assume it is susceptible. Handling Procedures 1. Always touch a known good ground before handling the part. This should be repeated while handling the pan and more frequently after sliding across a seat, sitting down from a standing position or walking a distance. 2. Avoid touching electrical terminals of the part, unless so instructed by a written diagnostic procedure. 3. When using a voltmeter, be sure to connect the ground lead first. 4. Do not remove a part from its protective package until it is time to install the part. 5. Before removing the part from its package, ground the package to a known good ground on the vehicle. Measuring Procedures The circuits shown within the boxes are greatly simplified. Do not troubleshoot by measuring resistance at any terminal of these devices unless so instructed by a written diagnostic procedure. Due to the simplification of the schematics, resistance measurements could be misleading, or could lead to electrostatic discharge. On Board Diagnostics II (OBDII) Symbol On Board Diagnostics II (OBDII) Symbol The OBDII symbol is used on circuit diagrams to alert the technician that the circuit is essential for proper OBDII emission control circuit operation. Any circuit which, if it fails, causes the SERVICE ENGINE SOON indicator to turn on, is identified as an OBDII circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12782 Schematic Symbols Fig.1-Symbols (Part 1 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12783 Fig.2-Symbols (Part 2 Of 3) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12784 Fig.3-Symbols (Part 3 Of 3) Vacuum Motors operate like electrical solenoids, mechanically pushing or pulling a shaft between two fixed positions. When vacuum is applied, the shaft is pulled in. When no vacuum is applied, the shaft is pushed all the way out by a spring. Double Diaphragm Motors can be operated by vacuum in two directions. When there is no vacuum, the motor is in the center "at rest" position. Some Vacuum Motors such as the Servo Motor in the Cruise Control can position the actuating arm at any position between fully extended and fully retracted. The servo is operated by a control valve that applies varying amounts of vacuum to the motor. The higher the vacuum level, the greater the retraction of the motor arm. Servo Motors work like the two position motors; the only difference is in the way the vacuum is applied. Servo Motors are generally larger and provide a calibrated control. Supplemental Inflatable Restraint (SIR) System SIR Symbol The Supplemental Inflatable Restraint (SIR) symbol is used on schematics to alert the technician to the following important caution. CAUTION: This vehicle is equipped with SIR. Refer to CAUTIONS in SIR under Air Bags and Seat Belts before performing service on or around SIR components or wiring. Failure to follow CAUTIONS could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12785 Wire Color Code Identification Black: BLK Blue: BLU Brown: BRN Grey: GR Or GRY Green: GRN Natural: NAT Orange: ORN Pink: PNK Purple: PPL Red: RED Tan: TAN White: WHT Yellow: YEL Dark: DK (example: DK GRN same as Dark Green) Light: LT (example: LT BLU same as Light Blue) Wire Size Conversion Table Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12786 Tail Lamp: Diagnostic Aids Additional Information NOTE: Turn OFF power to the test circuit before attempting in-circuit resistance measurements to prevent false readings or damage to the meter. Do not use the meter to measure resistance through a solid state module. Continuity tests that work well for detecting intermittent shorts to ground can be performed by setting the meter to "ohms" then pressing the "PEAK MIN MAX" button. An audible tone will be heard whenever the meter detects continuity for at least 1 millisecond. The J 39200 Instruction Manual is a good source of information and should be read thoroughly upon receipt of the meter as well as kept on hand for reference during new procedures. Basic Knowledge Required Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures. You should understand the basic theory of electricity and know the meaning of voltage, current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire. You should be able to read and understand a wiring diagram. The following four-step troubleshooting procedure is recommended: Step 1: Check the Problem Perform a System Check to determine a symptom. Don't waste time fixing part of the problem! Do not begin disassembly or testing until you have narrowed down the possible causes. Step 2: Read the Electrical Schematic Study the schematic. Read the Circuit Operation text if you do not understand how the circuit should work. Check circuits that share wiring with the problem circuit. (Shared circuits are shown on Power Distribution, Ground Distribution, Fuse Block Details and Light Switch Details.) Try to operate the shared circuits. If the shared circuits work, then the shared wiring is OK. The cause must be within the wiring used only by the problem circuit. If several circuits fail at the same time, chances are the power (fuse) or ground circuit is faulty. Step 3: Find the fault and repair ^ Narrow down the possible causes. ^ Use the Troubleshooting Hints. ^ Make the necessary measurements or checks as given in the System Diagnosis. ^ Before replacing a component, check power, signal and ground wires at the component harness connector. If the checks and connections are OK, the most probable cause is component failure. Step 4: Test the Repair Repeat the System Check to verify that the fault has been corrected and that no other faults were induced during the repair. EXAMPLE: A customer brings in a vehicle and says that the HI beams do not work. Step 1: Perform a System Check on the Headlight Circuit You may discover that both LO beams operate. In HI, you may notice that the HI Beam Indicator comes ON, but neither HI beam operates. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12787 Typical Headlights Schematic Step 2: Read the Headlights Electrical Schematic This is the step that will save time and labor. Remember, it is essential to understand how a circuit should work, before trying to figure out why it doesn't. After you understand how the circuit should operate, read the schematic again, this time keeping in mind what you have learned by operating the circuit. Since both LO beams work, you know that the Headlight Switch, the YEL wire, the LO contacts of the Headlight Dimmer Switch, terminal "1E" of C100, the TAN wires and grounds G1O5 and G109 are all good. Furthermore, since you saw that the HI Beam Indicator came ON when the Headlight Dimmer Switch was moved to HI you know that the HI contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good. At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in HI. However, it is extremely unlikely that the HI beam filaments have burned out in both headlamps, or that both headlamps connections are bad. The cause must be a bad connection at C100, or a break in the LT GRN wire between C100 and the RH Headlamp. You have quickly narrowed the possible causes down to one specific area, and have done absolutely no work on the vehicle itself. Step 3: Find the fault and repair it Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT GRN wire, locate the exact trouble point and make the repair. Step 4: Check the repair by performing a System Check on the Headlights Circuit This, of course, means making sure that both HI beams, both LO beams and the HI Beam Indicator are all working. Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither the HI beams nor the HI Beam Indicator were working. Looking at the schematic, you might conclude that it is unlikely that both HI beam filaments and the HI Beam Indicator have all burned out at once. The cause is probably the Headlight Dimmer Switch or its connector. Checking Terminal Contacts Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12788 DESCRIPTION When diagnosing an electrical system that utilizes Metri-Pack 150/280/480/630 series terminals (refer to Terminal Repair Kit, J 38125-A, J 38125-4 for terminal identification), it is important to check terminal contact between a connector and component, or between in-line connectors, before replacing a suspect component. Frequently, a diagnostic chart leads to a step that reads: Check for poor connection. Mating terminals must be inspected to assure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or deformation. Contamination is caused by the connector halves being improperly connected, a missing or damaged connector seal, or damage to the connector itself, exposing the terminals to moisture and dirt. Contamination, usually in underhood or underbody connectors, leads to terminal corrosion, causing an open circuit or intermittently open circuit. Deformation Of A Typical Metri-Pack 150/280/480/630 Series Female Terminal Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12789 Deformation is caused by probing the mating side of a connector terminal without the proper adapter, improperly joining the connector halves or repeatedly separating and joining the connector halves. Deformation, usually to the female terminal contact tang, can result in poor terminal contact, causing an open or intermittently open circuit. PROCEDURE Follow the procedure below to check terminal contact. 1. Separate the connector halves. Refer to Terminal Repair Kit, J 38125-A, J 38125-4. 2. Inspect the connector halves for contamination. Contamination will result in a white or green build-up within the connector body or between terminals, causing HI terminal resistance, intermittent contact or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals and connector body. 3. Using an equivalent male terminal from the Terminal Repair Kit, J 38125-A, check the retention force of the female terminal in question by inserting and removing the male terminal to the female terminal in the connector body. Good terminal contact will require a certain amount of force to separate the terminals. 4. Using an equivalent female terminal from the Terminal Repair Kit, J 38125-A, compare the retention force of this terminal to the female terminal in question by joining and separating the male terminal to the good female terminal, and then joining and separating the male terminal to the female terminal in question. If the retention force is significantly different between the two female terminals, replace the female terminal in question (refer to Terminal Repair Kit, J 38125-A). If a visual (physical) check does not reveal the cause of the problem, the vehicle may be able to be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. Detecting Electrical Intermittents PROCEDURE Use the following procedure to detect intermittent terminal contact or a broken wire with an intermittent connection inside the insulation. The J 39200 Digital Multimeter has the ability to monitor current, resistance, or voltage while recording the minimum (MIN) and maximum (MAX) values measured. The meter can also be set to display the average (AVG) value measured. When diagnosing circuits that have voltage applied, use the voltage setting to monitor a connector (or length of a circuit) which is suspected of having an intermittent connection but is currently operating normally. 1. Connect the J 39200 Digital Multimeter to both sides of a suspect connector (still connected) or from one end of a suspect circuit to the other. This will continuously monitor the terminal contacts or length of wire being checked. Refer Meter Connections for examples of the various methods for connecting the meter to the circuit. See: General Troubleshooting Procedures/Meter Connections 2. Set the meter for voltage. Since the "MIN MAX" mode does not use auto ranging, manually select the voltage range necessary before proceeding. 3. Press the "MIN MAX" button. The meter should read "100 ms RECORD" (100 millisecond record) and emit a 1/4 second beep. The meter is now ready to record and will generate an audible tone for any change in voltage. At this point, you may wish to press the "PEAK MIN MAX" button, which will record any voltage variations that occur for at least 1 millisecond. 4. Try to simulate the condition that is potentially causing an intermittent connection, either by wiggling connections or wiring, test driving or performing other operations. If an open or resistance is created, a voltage will be present and the meter will emit a tone for as long as the open or resistance exists. Any change in voltage will cause the meter to emit a tone for no less than 1/4 second. (Listening for a tone while manipulating wiring is very helpful for narrowing down an intermittent connection.) Use the MIN and MAX values when the meter is out of sight or sound range, in noisy areas or for test driving when it may not be possible to monitor the meter. To check the MIN and MAX recorded voltages press "MIN MAX" once for MAX and twice for MIN. A variation between MIN and MAX recorded voltages (unless nearly 0 volts) suggests an intermittent open or that resistance exists and should be repaired as necessary. IMPORTANT: The "100 ms RECORD" (100 millisecond record) mode is NOT the amount of time allowed to perform a specific procedure. It is the amount of time used to record each snapshot of information used for calculating "AVG" when in the "MIN MAX" mode. Intermittents and Poor Connections Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are: ^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out). ^ Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. ^ Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. ^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to Checking Terminal Contact for the specific procedure. ^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the adapter will ensure that no damage to the terminal will occur, as well as giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts ^ Poor terminal-to-wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12790 ^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. ^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but if only 1 or 2 strands of a multi-strand type wire are intact, resistance could be far too HI. To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring and terminal repair outlined under the Repair Procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures Meter Connections The previous diagnostic procedure was written to detect intermittents using the meter set to voltage. Whether using the current, voltage or resistance setting to detect intermittents, it is necessary to connect the meter to the circuit. Following are examples of the various methods of connecting the meter to the circuit to be checked: ^ Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while performing other operations or test driving. (Do not backprobe "Weather Pack(R)" type connectors.) ^ Disconnect the harness at both ends of the suspect circuit where it connects either to a component or to other harnesses. ^ Use Connector Test Adapter Kit J 35616-A to connect the meter to the circuit. ^ If the system being diagnosed has a specified Pinout or breakout box, it may be used to simplify connecting the meter to the circuit or for checking multiple circuits quickly. Aftermarket Accessories Do not tie aftermarket accessories into SIR circuits. All such circuits are indicated are indicated on circuit diagrams with the SIR symbol. SIR Symbol Do not tie aftermarket accessories into OBDII circuits. all such circuits are indicated on circuit diagrams with the OBDII symbol. On Board Diagnostics II (OBDII) Symbol Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problem. Some possible causes of vehicle problems related to aftermarket accessories include: 1. Power feeds connected to points other than the Battery. 2. Antenna location. 3. Transceiver wiring located too close to vehicle electronic modules or wiring. 4. Poor shielding or poor connectors on antenna feed line. Probing (Frontprobe & Backprobe) After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12791 Frontprobe When frontprobing of connectors is required, always use a mating terminal adapter from Connector Test Adapter Kit (J 35616-A). The use of proper adapters will ensure that proper terminal contact integrity is maintained. (refer to Procedures in Checking Terminal Contact). Backprobe Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe. After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Testing For Voltage Voltage Check 1. Connect one lead of a test light to a known good ground. When using a Digital Voltmeter (DVM), be sure the voltmeter's negative lead is connected to ground. 2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal). 3. If the test light illuminates, there is voltage present. When using a DVM, note the voltage reading. Testing For Continuity Continuity Check Through A Switch 1. Remove the fuse to the circuit involved. 2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test. 3. Connect the other lead to the other end of the circuit. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12792 4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity. Testing For Voltage Drop Voltage Drop Test This test checks for voltage being lost along a wire, or through a connection or switch. 1. Connect the positive lead of a Digital Voltmeter (DVM) to the end of the wire (or to one side of the connection or switch) which is closer to the Battery. 2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch). 3. Operate the circuit. 4. The DVM will show the difference in voltage between the two points. Testing For Short to Ground Testing For Short With Self Powered Test Light Or Ohmmeter WITH A TEST LIGHT OR DIGITAL VOLTMETER (DVM) 1. Remove the blown fuse and disconnect the load. 2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered). 3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12793 test light or DVM. 4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point. Testing For Short With Test Light Or DVM WITH A SELF-POWERED TEST LIGHT OR OHMMETER. 1. Remove the blown fuse and disconnect the Battery and load. 2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side. 3. Connect the other lead to a known good ground. 4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter. 5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point. FUSES POWERING SEVERAL LOADS 1. Find the schematic under "Fuse Block Details," for the fuse that has blown. 2. Open the first connector or switch leading from the fuse to each load. 3. Replace the fuse. ^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described. ^ If fuse does not blow, refer to next step. 4. Close each connector or switch until the fuse blows in order to find which circuit has the short. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals. Test Light/Digital Voltmeter Use a test light to check for voltage. A Test Light (J 34l42-B) is made up of a 12 volt light bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. When the bulb goes ON, there is voltage at the point being tested. A Digital Voltmeter (DVM) can be used instead of a test light. While a test light shows whether or not voltage is present, a DVM indicates how much voltage is present. An increasing number of circuits include solid state control modules. One example is the Engine Control Module (ECM). Voltages in these circuits should be tested only with a 10-megohm or higher impedance DVM or multimeter (J 39200). Unless directed to within the diagnostics, NEVER use a test light on circuits that contain solid state components, since damage to these components may result. When testing for voltage or continuity at the connection, it is not necessary to separate the two halves of the connector. Unless testing a Weather Pack(R) connector, always probe the connector from the back. Always check both sides of the connector. An accumulation of dirt and corrosion between contact surfaces is sometimes a cause of electrical problems. Refer to Procedures in checking terminal contact. See: General Troubleshooting Procedures/Checking Terminal Contacts Connector Test Adapters Connector Test Adapter Kit (J 35616-A) is available for making tests and measurements at separated connectors. This kit contains an assortment of probes which mate with many of the types of terminals you will see. Avoid using paper clips and other substitutes since they can damage terminals and cause incorrect measurements. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12794 Self-Powered Test Light A self-powered test light (J 21008-A) can be used to check for continuity. This tool is made up of a light bulb, Battery and two leads. If the leads are touched together, the bulb will go ON. A self-powered test light is used only on an unpowered circuit. First remove the fuse which feeds the circuit you're working on. Select two specific points along the circuit through which there should be continuity. Connect one lead of the self-powered test light to each point. If there is continuity, the test light circuit will be completed and the bulb will go ON. NEVER use a self-powered test light on circuits that contain solid state components, since damage to these components may result. Ohmmeter An ohmmeter can be used instead of a self-powered test light. The ohmmeter shows how much resistance there is between two points along a circuit. LO resistance means good continuity. Circuits which include any solid state control modules, such as the Engine Control Module (ECM), should be tested only with a 10-megohm or higher impedance digital multimeter (J 39200). When measuring resistance with a Digital Voltmeter (DVM), the vehicle Battery should be disconnected. This will prevent incorrect readings. DVMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading. Diodes and solid state components in a circuit can cause an ohmmeter to give a false reading. To find out if a component is affecting a measurement, take a reading once, reverse the leads and take a second reading. If the readings differ, the solid state component is affecting the measurement. Fused Jumper Wire A fused jumper (J 36169) is available with small clamp connectors providing adaptation to most connectors without damage. This fused jumper wire is supplied with a 20 amp fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested. NOTE: A fused jumper may not protect solid state components from being damaged. Short Finder Short Finders (J 8681-A) are available to locate hidden shorts to ground. The short finder creates a pulsing magnetic field in the shorted circuit and shows you the location of the short through body trim or sheet metal. Fuse Tester A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12795 Special Tools Circuit Breakers A circuit breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. There are two basic types of circuit breakers used in GM vehicles: cycling and non-cycling. Cycling Circuit Breaker The cycling breaker will open due to heat generated when excessive current passes through it for a period of time. Once the circuit breaker cools, it will close again after a few seconds. If the cause of the HI current is still present it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12796 Non-Cycling Circuit Breaker There are two types of non-cycling circuit breakers. One type is mechanical and is nearly the same as a cycling breaker. The difference is a small heater wire within the non-cycling circuit breaker. This wire provides enough heat to keep the bimetallic element open until the current source is removed. The other type is solid state, called out as Electronic Circuit Breaker (ECB). This device has a Positive Temperature Coefficient. It increases its resistance greatly when excessive current passes through it. The excessive current heats the ECB. As it heats, its resistance increases, therefore having a Positive Temperature Coefficient. Eventually the resistance gets so HI that the circuit is effectively open. The ECB will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the circuit breaker will re-close within a second or two. Fuses Fuse Devices The most common method of automotive wiring circuit protection is the fuse. A fuse is a device that, by the melting of its element, opens an electrical circuit when the current exceeds a given level for a sufficient time. The action is non-reversible and the fuse must be replaced each time a circuit is overloaded or after a malfunction is repaired. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12797 Fuse Rating And Color Fuses are color coded. The standardized color identification and ratings are shown. For service replacement, non-color coded fuses of the same respective current rating can be used. Examine a suspect fuse for a break in the element. If the element is broken or melted, replace the fuse with one of equal current rating. There are additional specific circuits with in-line fuses. These fuses are located within the individual wiring harness and will appear to be an open circuit if blown. Autofuse The Autofuse, normally referred to simply as "Fuse," is the most common circuit protection device in today's vehicle. The Autofuse is most often used to protect the wiring assembly between the Fuse Block and the system components. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12798 Maxifuse The Maxifuse was designed to replace the fusible link and Pacific Fuse elements. The Maxifuse is designed to protect cables, normally between the battery and fuse block, from both direct short circuits and resistive short circuits. Compared to a fusible link or a Pacific Fuse element, the Maxifuse performs much more like an Autofuse, although the average opening time is slightly longer. This is because the Maxifuse was designed to be a slower blowing fuse, with less chance of nuisance blows. Minifuse The Minifuse is a smaller version of the Autofuse and has a similar performance. As with the Autofuse, the Minifuse is usually used to protect the wiring assembly between a fuse block and system components. Since the Minifuse is a smaller device, it allows for more system specific fusing to be accomplished within the same amount of space as Autofuses. Pacific Fuse Element/Maxifuse The Pacific Fuse Element and Maxifuse were developed to be a replacement for the fusible link. Like a fusible link, the fuses are designed to protect wiring from a direct short to ground. These elements are easier to service and inspect than a fusible link and will eventually replace fusible links in all future vehicle applications. Fusible Links Good And Damaged Fusible Links In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit. Not all fusible link open Circuits can be detected by observation. Always inspect that there is battery voltage past the fusible link to verify continuity. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12799 Wire Size Conversion Table Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes, each fusible link is four wire gage sizes smaller than the wire it is designed to protect. For example: to protect a 10 gage wire use a 14 gage link or for metric, to protect a 5 mm Sq. wire use a 2 mm Sq. link, refer to Wire Size Conversion Table. Links are marked on the insulation with wire-gage size because the heavy insulation makes the link appear to be a heavier gage than it actually is. The same wire size fusible link must be used when replacing a blown fusible link. Fusible links are available with three types of insulation: Hypalon(R), Silicone/GXL (SIL/GXL) and Expanded Duty. All future vehicles that use fusible links will utilize the Expanded Duty type of fusible link. When servicing fusible links, all fusible links can be replaced with the Expanded Duty type. SIL/GXI fusible links can be used to replace either SIL/GXI or Hypalon(R) fusible links. Hypalon(R) fusible links can only be used to replace Hypalon(R) fusible links. Determining characteristics of the types of fusible links are: Hypalon(R) (limited use): only available in 0.35 mm Sq. or smaller and its insulation is one color all the way through. - SIL/GXL (widely used): available in all sizes and has a white inner core under the outer color of insulation. - Expanded Duty: available in all sizes, has an insulation that is one color all the way through and has three dots following the writing on the insulation. Service fusible links are available in many lengths. Choose the shortest length that is suitable. If the fusible link is to be cut from a spool, it should be cut 150-225 mm (approx. 6-9 in.) long. NEVER make a fusible link longer than 225 mm (approx. 9 in.). CAUTION: Fusible links cut longer than 225 mm (approx. 9 in.) will not provide sufficient overload protection. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12800 Single Wire Feed Fusible Link To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip wire and use staking-type pliers to crimp the splice securely in two places. For more details on splicing procedures, refer to "Typical Electrical Repair Procedures." Use crimp and seal splices whenever possible. See: Wire Repair Procedures/Typical Electrical Repair Procedures Double Wire Feed Fusible Link To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each harness wire. General Information The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a current requirement that is higher than normal. This overload could be caused by a short circuit or system malfunction. The short circuit could be the result of a pinched or cut wire or an internal device short circuit, such as an electronic module failure. The circuit protection device is only applied to protect the wiring assembly, and not the electrical load at the end of the assembly. For example, if an electronic component short circuits, the circuit protection device will assure a minimal amount of damage to the wiring assembly. However, it will not necessarily prevent damage to the component. There are three basic types of circuit protection devices: Circuit Breaker, Fuse and Fusible Link. Complete Harness In many cases repairs can be made by ordering pigtail assemblies (prewired connectors) rather than the entire wiring harness. Only order complete harness when there is major damage to the wiring harness. Always repair minor damage. Complete harness and pigtail part numbers can be found in the GMSPO Carline Parts Catalog. Gmspo Carline Parts Catalog The GMSPO Carline parts Catalog, Group 2.535 contains connector repair kits with terminals and leads. Gmspo Standard Parts Catalog Check the GMSPO Standard Parts Catalog, Group 8.965. Fuses, circuit breakers, connectors, terminals, conduit, pigtail kits, and seals are listed in that group. Ordering Service Parts 1. If you can't find the repair parts you need in the J 38125-A Terminal Repair Kit, GMSPO Standard Parts Catalog, or the GMSPO Carline Parts Catalog refer to the "Harness Connector Faces" to find a listing of the OE part number(s). 2. Call PARTECH (1-800-433-6961) and give the PARTECH advisor the OE part number(s). The PARTECH advisor can determine if there is a GMSPO part number(s) for the OE part number(s). 3. If PARTECH cannot find a GMSPO part number, call the Service Parts Assistance Center (SPAC) with the OE part number(s). The SPAC advisor will assist you in placing a priority order using the "No Part Number" process with the Packard Electric Division. The SPAC advisor may have you place the order with the Packard Electric Division (1-800-PACKARD). Parts are typically shipped within 24 hours direct to your Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12801 dealership. Diode Replacement Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode, use the following procedure: Step 1: Open the Harness If the diode is taped to the harness, remove all of the tape. Step 2: Remove inoperative Diode Paying attention to current flow direction, remove inoperative diode from the harness with a suitable soldering tool. If the diode is located next to a connector terminal, remove the terminal(s) from the connector to prevent damage from the soldering tool. Step 3: Strip the Insulation Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode. Diode Identification Step 4: Install New Diode Check current flow direction of the new diode, being sure to install the diode with correct bias. Refer the image for replacement diode symbols and current flow explanations. Attach the new diode to the wire(s) using 60/40 rosin core solder. Use a beat sink (aluminum alligator clip) attached across the diode wire ends to protect the diode from excess heat. Follow the manufacturer's instructions for the soldering equipment you are using. Step 5: Install Terminal(s) Install terminal(s) into the connector body if previously removed in Step 2. Step 6: Tape Diode to Harness Tape the diode to the harness or connector using electrical tape. To prevent shorts to ground and water intrusion, completely cover all exposed wire and diode attachment points. Acceptable Diode Replacements In the event 1 amp, 50 PIV (Peak Inverse Rating) diodes are unavailable, a universal diode with a 1 amp, 400 PIV rating can be used for the following applications: ^ A/C Compressor Clutch ^ ABS/4WAL (the ABS Diode on the Delco Moraine is hidden inside of an electrical connector under the carpet at the RH panel) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12802 ^ Wiper ^ Charging System (hidden in wire harness) ^ Parking Brake (vehicle with ABS) ^ Relays ^ Solenoids ^ Diesel Glow Plug Circuit General Information OPEN CIRCUIT An open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. SHORT CIRCUIT A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open. Heated Oxygen Sensor (O2S) Repair If the Heated Oxygen Sensor pigtail wiring, connector or terminal is damaged, the entire Oxygen Sensor Assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have provided to it a clean air reference. This clean air reference is obtained by way of the Oxygen Sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degraded Oxygen Sensor performance. The following guidelines should be used when servicing the Heated Oxygen Sensor: ^ Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance. Also the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems. ^ Neither the sensor or vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire. ^ Do not remove or defeat the Oxygen Sensor ground wire (where applicable). Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance. ^ To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector. The Engine Harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit J 38125-A. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed. Obdii Circuit Repairs Repairs for On-Board Diagnostics II (OBDII) emission control circuits follow the procedures stated in TYPICAL ELECTRICAL REPAIR PROCEDURES. When servicing OBDII circuits, the following guidelines are also essential: ^ Do not move or alter grounds from their manufactured locations. ^ Do not tie aftermarket accessories into OBDII circuits. ^ Only repair OBDII circuits in accordance with the manufactured configuration. ^ Always replace a relay in the OBDII circuit the same replacement part. Damaged relays should be discarded, not repaired. ^ Refer to Fuseblock Details to identify OBDII circuit fusing. See: Power and Ground Distribution ^ Make sure the CPA (connector position assurance) locks and TPA (terminal position assurance locks are reinstalled on connectors that use them. ^ After repair of connectors or connector terminals, make sure to achieve proper terminal retention. Refer to Repairing Connectors. for procedures. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Repairing Connectors ^ Before repairing OBDII heated oxygen sensors and related wiring, always review the special repair guidelines provided in Heated Oxygen Sensor Repair. See: Wire Repair Procedures/Typical Electrical Repair Procedures/Heated Oxygen Sensor (O2S) Repair ^ When installing an electrical ground fastener, be sure to apply the specified torque. Ground torque specifications are listed in Ground Distribution. See: Power and Ground Distribution ^ After repair of connectors, make sure to reinstall connector seals, where used. Inspect seals for wear and damage. Replace worn or damaged seals. General Information ^ The following general repair procedures can be used to repair most types of connectors. The repair procedures are divided into three general groups: Push-to-Seat, Pull-to-Seat and Weather Pack(R). ^ Use the proper Pick(s) or Tool(s) that apply to the terminal. ^ The Terminal Repair Kit (J 38125-A) contains further information. Push-to-Seat and Pull-to-Seat Connectors Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12803 Typical Push-to-seat Connector And Terminal Typical Pull-to-seat Connector And Terminal Follow the steps below to repair Push-to-Seat or Pull-to-Seat connectors. The steps are illustrated with typical connectors. Your connector may differ, but the repair steps are similar. Some connectors do not require all the steps shown. Skip those that don't apply. Step 1: Remove any Connector Position Assurance (CPA) Locks . CPAs are designed to retain connectors when mated. Step 2: Remove any Terminal Position Assurance (TPA) Locks. TPAs are designed to keep the terminal from backing out of the connector. NOTE: The TPA must be removed prior to terminal removal and must be replaced when the terminal is repaired and reseated. Step 3: Open any secondary locks. A secondary lock aids in terminal retention and is usually molded to the connector. Step 4: Separate the connector halves and back out seals. Step 5: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 6: Locate the terminal lock tang in the connector canal. Step 7: Insert the proper size pick (refer to Terminal Repair kit J 38125-A) straight into the connector canal at the mating end of the connector. Step 8: Depress the locking tang to unseat the terminal. ^ Push-to-Seat - Gently pull on the lead to remove the terminal through the back of the connector. ^ Pull-to-Seat - Gently push on the lead to remove the terminal through the front of the connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12804 NOTE: NEVER use force to remove a terminal from a connector. Step 9: Inspect terminal and connector for damage. Repair as necessary (refer to Terminal Repairs). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 10: Reform lock tang and reseat terminal in connector body. Apply grease if connector was originally equipped with grease. Step 11: Install any CPAs or TPAs, close any secondary locks and join connector halves. Weather Pack(R) Connectors Typical Weather Pack(R) Connector And Terminal Follow the steps below to repair Weather Pack(R) connectors. Step 1: Separate the connector halves. Step 2: Open secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector. Step 3: Grasp the lead and push the terminal to the forward most position. Hold the lead at this position. Step 4: Insert the Weather Pack(R) terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder. Step 5: Gently pull on the lead to remove the terminal through the back of the connector. NOTE: NEVER use force to remove a terminal from a connector. Step 6: Inspect the terminal and connector for damage. Repair as necessary (refer to Terminal Repair). See: Wire Repair Procedures/Typical Electrical Repair Procedures/Terminal Repairs Step 7: Re-form the lock tang and reseat terminal in connector body. Step 8: Close secondary locks and join connector halves. Repairing Short Circuits Caused By Damaged Wire ^ Locate the damaged wire. ^ Find and correct the cause of the wire insulation damage. ^ For minor damage, tape over the wire. If damage is more extensive, replace the faulty segment of the wire (refer to the Splicing Instructions for copper or shielded cable for the correct splicing procedure). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12805 See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Splice Clips See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Copper Wire Using Crimp and Seal Splice Sleeves See: Wire Repair Procedures/Typical Electrical Repair Procedures/Splicing Twisted/Shielded Cable Splicing Copper Wire Using Crimp and Seal Splice Sleeves Crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial to form a one-to-one splice. They are to be used where there are special requirements such as moisture sealing. Crimp and seal splice sleeves are included in the J 38125-A Terminal Repair Kit. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). The crimp and seal splice sleeves may be used on all types of insulation except Tefzel and coaxial and may only be used to form a one-to-one splice. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. This will help prevent moisture from bridging adjacent splices and causing damage. Wire Size Conversion Table Step 3: Strip the Insulation If it is necessary to add a length of wire to the existing harness, be certain to use the same size as the original wire. To find the correct wire size either find the wire on the schematic and convert the metric size to the equivalent AWG size or use an AWG wire gage. If unsure about the wire size, begin with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Strip approximately 7.5 mm (5/16 in.) of insulation from each wire to be spliced. Be careful to avoid nicking or cutting any of the wires. Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section. Crimp And Seal Splice Sleeve Chart Step 4: Select and Position the Splice Sleeve Select the proper splice sleeve according to wire size. The splice sleeves and tool tests are color coded (refer to Chart). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12806 Hand Crimp Tool Using the J 38125-8 splice crimp tool, position the splice sleeve in the proper color nest of the hand crimp tool. Place the splice sleeve in the nest so that the crimp falls midway between the end of the barrel and the stop. Seal Splice Sequence The sleeve has a stop in the middle of the barrel to prevent the wire from going further. Close the hand crimper handles slightly to hold the splice sleeve firmly in the proper nest. Step 5: Insert Wires into Splice Sleeve and Crimp Insert the wire into the splice sleeve until it hits the barrel stop and close the handles of the J 38125-8 crimper tightly until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve. Repeat steps 4 and 5 for opposite end of the splice. Step 6: Shrink the Insulation Around the Splice Using the Ultratorch J 38125-5 (follow instructions that accompany Ultratorch), apply heat where the barrel is crimped. Gradually move the heat barrel to the open end of the tubing, shrinking the tubing completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinking is achieved. Splicing Copper Wire Using Splice Clips Splice clips are included in the J 38125-A Terminal Repair Kit. The splice clip is a general purpose wire repair device. It may not be acceptable for applications having special requirements such as moisture sealing. Step 1: Open the Harness If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a black plastic conduit, simply pull out the desired wire. Step 2: Cut the Wire Begin by cutting as little wire off the harness as possible. You may need the extra length of the wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1.5 in.) away from other splices, harness branches or connectors. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12807 Wire Size Conversion Table Step 3: Strip the Insulation When replacing a wire, use a wire of the same size as the original wire or larger. The schematics list wire size in metric units. The table shows the commercial AWG wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size either find the wire on the schematic page and convert the metric size to the AWG size, or use an AWG wire gage. If you aren't sure of the wire size, start with the largest opening in the wire stripper and work down until a clean strip of the insulation is removed. Be careful to avoid nicking or cutting any of the wires. Entering The Splice Clip Step 4: Crimp the Wires Select the proper clip to secure the splice. To determine the proper clip size for the wire being spliced, follow the directions included in the J 38125-A Terminal Repair Kit. Select the correct anvil on the crimper. (On most crimpers your choice is limited to either a small or large anvil.) Overlap the stripped wire ends and hold them between your thumb and forefinger as shown. Then, center the splice clip under the stripped wires and hold it in place. ^ Open the crimping tool to its full width and rest one handle on a firm flat surface. ^ Center the back of the splice clip on the proper anvil and close the crimping tool to the point where the former touches the wings of the clip. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12808 Crimping The Splice Clip ^ Make sure that the clip and wires are still in the correct position. Then, apply steady pressure until the crimping tool closes. ^ Before crimping the ends of the clip, be sure that: The wires extend beyond the clip in each direction. - No strands of wire are cut loose. - No insulation is caught under the clip. Completing The Crimp Crimp the splice again, once on each end. Do not let the crimping tool extend beyond the edge of the clip or you may damage or nick the wires. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12809 Applying The Solder Step 5: Solder Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instruction for the solder equipment you are using. Proper First Taping Step 6: Tape the Splice Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness. Proper Second Taping Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12810 If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape. Splicing Twisted/Shielded Cable Twisted/shielded Cable Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, two-conductor cable of this construction is used between the Engine Control Module (ECM) and the distributor. Step 1: Remove Outer Jacket Remove the outer jacket and discard it. Be careful to avoid cutting into the drain wire or the mylar tape. Step 2: Unwrap the Tape Unwrap the aluminium/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made. The Untwisted Conductors Step 3: Prepare the Splice Untwist the conductors. Then, prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts. Step 4: Re-assemble the Cable After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape. The Re-assembled Cable Next, splice the drain wire following the splicing instructions for copper wire. Then, wrap the drain wire around the conductors and mylar tape. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12811 Proper Taping Step 5: Tape the Cable Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the repair. Terminal Repairs Terminal Repair The following repair procedures can be used to repair Push-to-Seat, Pull-to-Seat or Weather Pack(R) terminals. Some terminals do not require all steps shown. Skip those that don't apply. The Terminal Repair Kit (J 38125-A) contains further information. Step 1: Cut off terminal between core and insulation crimp (minimize wire loss) and remove seal for Weather Pack(R) terminals. Step 2: Apply correct seal per gauge size of wire and slide back along wire to enable insulation removal (Weather Pack(R) terminals only). Step 3: Remove insulation. Step 4: Align seal with end of cable insulation (Weather Pack(R) terminals only). Step 5: Position strip (and seal for Weather Pack(R)) in terminal. Step 6: Hand crimp core wings. Step 7: Hand crimp insulation wings (non-Weather Pack(R)). Hand crimp insulation wings around seal and cable (Weather Pack(R)). Step 8: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12812 Solder all hand crimped terminals. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Tail Lamp > Component Information > Diagrams > Diagram Information and Instructions > Page 12813 C409: Engine HARN To Taillamp EXT HARN Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Turn Signals > Turn Signal Lamp > Component Information > Technical Service Bulletins > Lighting - Exterior Lamp Condensation and Replacement Turn Signal Lamp: Technical Service Bulletins Lighting - Exterior Lamp Condensation and Replacement INFORMATION Bulletin No.: 01-08-42-001H Date: January 05, 2011 Subject: Exterior Lamp Condensation and Replacement Guidelines Models: 2011 and Prior GM Passenger Cars and Trucks (including Saturn) Supercede: This bulletin is being revised to add the 2011 model year. Please discard Corporate Bulletin Number 01-08-42-001G (Section 08 - Body and Accessories). The following information is being provided to better define the causes of condensation in exterior lamps and includes guidelines for determining the difference between a lamp with a normal atmospheric condition (condensation) and a lamp with a water leak. Some exterior lamps, such as cornering, turn signal, backup, headlamps or tail lamps may exhibit very small droplets of water, a fine mist or white fog (condensation) on the inside of the lamp lens. This may be more noticeable on lamps with "multi-lens" designs and may be normal during certain weather conditions. Condensation occurs when the air inside the lamp assembly, through atmospheric changes, reaches the "dew point". When this takes place, the moisture in the air within the lamp assembly condenses, creating a fine mist or white fog on the inside surface of the lamp lens. Most exterior lamps on General Motors vehicles use a vented design and feature a replaceable bulb assembly. They are designed to remove any accumulated moisture vapor by expelling it through a vent system. The vent system operates at all times, however, it is most effective when the lamps are ON or when the vehicle is in motion. Depending on the size, shape and location of the lamp on the vehicle, and the atmospheric conditions occurring, the amount of time required to clear the lamp may vary from 2 to 6 hours. Completely sealed headlamp assemblies (sealed beams) are still used on a limited number of models being manufactured today. These lamps require the replacement of the complete lamp assembly if a bulb filament burns out. Condensation 2006 TrailBlazer Shown A Fine Mist or White Fog on the Inside Surface of the Lamp Lens Occurring After a Period of High Humidity - May be located primarily in the lens corners (near the vents) and SHOULD NOT cover more than half the lens surface. - The condition should clear of moisture when the vehicle is parked in a dry environment, or when the vehicle is driven with the lights ON. - A comparison of the equivalent lamp on the opposing side of the vehicle indicates a SIMILAR performance. If the above conditions are noted, the customer should be advised that replacement of a lamp assembly may not correct this condition. Water Leak New Style Pickup Shown Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Turn Signals > Turn Signal Lamp > Component Information > Technical Service Bulletins > Lighting - Exterior Lamp Condensation and Replacement > Page 12819 Numerous & Various Size Drops of Water Collecting on the Inside Surface of the Lamp Lens After the Vehicle Has Been Exposed to Rain or a Car Washing Environment - A condition that covers more than half the surface of the lamp lens. - An accumulation of water in the bottom of the lamp assembly. - A condition that WON'T clear when the vehicle is parked in a dry environment, or when the vehicle is driven with the lights ON. - A comparison of the equivalent lamp on the opposing side of the vehicle indicates a different performance. Any of the above conditions would indicate the need to service the lens or lamp assembly. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Turn Signals > Turn Signal Switch > Component Information > Diagrams > C266 Harness Connector C266: I/P Harness To Steering Column Harness Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Turn Signals > Turn Signal Switch > Component Information > Diagrams > C266 Harness Connector > Page 12824 Turn Signal Switch: Diagrams C266 Pinout Description C266: I/P Harness To Steering Column Harness (Part 1 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Turn Signals > Turn Signal Switch > Component Information > Diagrams > C266 Harness Connector > Page 12825 C266: I/P Harness To Steering Column Harness (Part 2 Of 2) Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Lighting and Horns > Underhood Lamp > Component Information > Locations Underhood Lamp Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Heated Glass Element > Heated Glass Element Switch > Component Information > Locations Heated Glass Element Switch: Locations LH side of I/P Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Rear Defogger > Component Information > Technical Service Bulletins > A/C - Broken Rear Window Defogger Grid Detection Rear Defogger: Technical Service Bulletins A/C - Broken Rear Window Defogger Grid Detection Bulletin No.: 04-08-48-001B Date: June 28, 2005 INFORMATION Subject: Rear Window Defogger - Broken Heating Grid Detection Method Models: 2006 and Prior Passenger Cars and Light Duty Trucks (Including Saturn) 2003-2006 HUMMER H2 2006 HUMMER H3 Supercede: This bulletin is being revised to add the 2006 model year and additional models. Please discard Corporate Bulletin Number 04-08-48-001A (Section 08 - Body and Accessories). The addition of vertical grid lines to the heated back window defogger circuits has made it difficult to detect broken defogger grid lines. In the past, it was a simple matter to use a voltmeter to check the continuity of each grid line in order to locate a non-functional line. Some new design back windows have two vertical grid lines that connect all of the horizontal grid lines together, thereby providing alternate routes for the electrical current to follow. This makes the old test method ineffective. If the vehicle does not have the vertical lines, the old (line-by-line) test methods can be used. Materials Required ^ Permatex(R) Quick Grid, GM P/N 12346001, or equivalent ^ A small ball of fine steel wool Type 00, or ^ Optional - A strip of liquid crystal heat sensitive paper, 51 mm x 305 mm (2 in x 12 in) or similar size (Contact Edmund Scientific at 800-728-6999 for part number CR30723-70 or go to www.scientificsonline.com), or ^ Optional-A portable infrared thermometer, GE-46819, available from Kent-Moore (1-800-345-2233), or equivalent. Correction There are three distinct zones across the back window that must be checked. They are: ^ the driver's side outboard of the two vertical lines ^ the passenger side outboard of the two vertical lines ^ the central zone that falls between the two vertical lines To detect a broken grid line in any of the above three zones and to isolate the exact location of the break, perform the following steps: Caution: ^ Approved safety glasses and gloves should be worn when performing this procedure to reduce the chance of personal injury. ^ Cover the rear shelf area to prevent damage to the interior trim material. 1. Start the engine and turn on the back window defogger. 2. Take the ball of fine steel wool and twist one end to a point. Move the point slowly across each grid line. Be sure to start at the far side of the zone and move it to the opposite side of the zone. When you bridge the grid line break with the steel wool, you will see a small spark. Repeat the test over the same area to be sure you have accurately located the break. Mark the exact location of the grid line break. Repeat this portion of the test for each grid line. If you do not see a spark at any point, it is possible that there are two breaks in the same line and zone. Close visual inspection using a magnifying glass may be the only way to locate breaks in this case. 3. The following are provided as an alternative way to detect a non-functional grid line. If available, use in addition to the steel wool. 3.1. Method using liquid crystal heat sensitive paper: Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Rear Defogger > Component Information > Technical Service Bulletins > A/C - Broken Rear Window Defogger Grid Detection > Page 12838 Important: The first part of the test must be completed quickly before the entire surface of the back window becomes warm. 3.1.1. From outside the vehicle, place the heat sensitive paper (dull surface in contact with the glass) against the top driver side grid line. Start the engine and turn on the back window defogger. A distinct color change will take place at each conductive grid line. Repeat for the bottom grid lines until they have all been checked in the driver side zone. 3.1.2. Repeat the process for the passenger side and center area zones. 3.1.3. If no color change is noted for a grid line, place a crayon or china marker check mark beside it. Mark each grid line in the zone where it is non-conductive and, therefore, not heating up. More than one broken grid line may be found. 3.2. Method using portable infrared thermometer: 3.2.1. Start the engine and turn on the rear back window defogger. 3.2.2. From inside the vehicle, start at the top driver side grid line and slowly run the portable infrared thermometer vertically down the rear window contacting each grid line. You should be able to see a district variation in temperature readings. 3.2.3. Mark each grid line in the zone where it is non-conductive and, therefore, not heating up. More than one broken grid line may be found. 3.2.4. Repeat the process for the passenger side and center area zones. 4. Use Permatex(R) Quick Grid, GM P/N 12346001, or equivalent, to repair each broken grid line. Follow the manufacturer's instructions. 5. Wait 24 hours before turning the defogger on, or the repair can be fast cured using a heat gun, 260°C - 371°C (500°F - 700°F). Hold the heat gun within 25 - 51 mm (1-2 in) from the repair point for 2 to 3 minutes. 6. Recheck the grid line with the heat sensitive paper or portable infrared thermometer to ensure that the line is now functional and that the repair was successful. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Sensors and Switches - Windows and Glass > Heated Glass Element Switch > Component Information > Locations Heated Glass Element Switch: Locations LH side of I/P Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Sensors and Switches - Windows and Glass > Power Window Lockout Switch > Component Information > Locations Front Door Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Sensors and Switches - Windows and Glass > Power Window Switch > Component Information > Locations > Power Window Switch, RH Front Power Window Switch: Locations Power Window Switch, RH Front Power Window Switches Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Sensors and Switches - Windows and Glass > Power Window Switch > Component Information > Locations > Power Window Switch, RH Front > Page 12850 Rear Door Wiring On Door Trim Panel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Sensors and Switches - Windows and Glass > Power Window Switch > Component Information > Locations > Power Window Switch, RH Front > Page 12851 Power Window Switch: Locations Power Windows and Door Lock Switch, Passenger Side On LH Door Trim Panel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Sensors and Switches - Windows and Glass > Power Window Switch > Component Information > Locations > Power Window Switch, RH Front > Page 12852 Power Window Switch: Locations RH/LH Power Window Switches Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Sensors and Switches - Windows and Glass > Power Window Switch > Component Information > Locations > Power Window Switch, RH Front > Page 12853 Rear Door Wiring On Door Trim Panel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Sensors and Switches - Windows and Glass > Power Window Switch > Component Information > Diagrams > LH Door Master Power Window Switch LH Door Master Power Window Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Sensors and Switches - Windows and Glass > Power Window Switch > Component Information > Diagrams > LH Door Master Power Window Switch > Page 12856 Power Window Switch: Diagrams Power Window and Door Lock Switch Power Window And Door Lock Switch, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Sensors and Switches - Windows and Glass > Power Window Switch > Component Information > Diagrams > LH Door Master Power Window Switch > Page 12857 Power Window And Door Lock Switch, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Power Window Lockout Switch > Component Information > Locations Front Door Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Power Window Motor > Component Information > Locations Power Window Motor: Locations Front Door Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Power Window Motor > Component Information > Locations > Page 12865 Rear Door Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Power Window Motor > Component Information > Locations > Page 12866 Power Window Motor: Diagrams Power Window And Door Lock Switch, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Power Window Motor > Component Information > Locations > Page 12867 Power Window And Door Lock Switch, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Power Window Motor > Component Information > Service and Repair > Rear Window Glass Power Window Motor: Service and Repair Rear Window Glass Rear Door Window Sash Channel Rear Door Window Weatherstrip CAUTION: To prevent personal injury, gloves should be worn when removing broken glass. Lower window Remove or Disconnect 1. Trim panel. Refer to Trim Panel. See: Body and Frame/Doors, Hood and Trunk/Doors 2. Water deflector. Refer to Inner Panel Water Deflector. 3. Window sash bolts. 4. Glass weatherstrip. Pull weatherstrip out of window frame and front run channel. 5. Lift window out of the top of door. Install or Connect 1. Slide window into glass channels through the top of door. 2. Glass weatherstrip. 3. Window sash bolts. Tighten: Window sash bolts to 1.9 Nm (17 lbs. in.). 4. Water deflector. Refer to Inner Panel Water Deflector. 5. Trim panel. Refer to Trim Panel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Power Window Motor > Component Information > Service and Repair > Rear Window Glass > Page 12870 Power Window Motor: Service and Repair Window Regulator Motor - Front Front Door Window Regulator Assembly Note: The power window motor can not be serviced. It is replaced as a unit with the regulator. Tool Required: J 34940 Rivet Gun Remove or Disconnect 1. Trim panel. Refer to Trim Panel. See: Body and Frame/Doors, Hood and Trunk/Doors 2. Water deflector. Refer to Inner Panel Water. 3. Inner mounting panel assembly. Refer to Inner Mounting Panel. 4. Rivets securing the regulator to the door inner panel. Drill out (2) front and (2) rear rivets. 5. Regulator from inner panel. Install or Connect 1. Regulator to inner panel. 2. Rivets securing the regulator to the door inner panel using J34940. 3. Inner mounting panel assembly. Refer to Inner Mounting Panel. 4. Water deflector. Refer to Inner Panel Water Deflector. 5. Trim panel. Refer to Trim Panel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Power Window Motor > Component Information > Service and Repair > Rear Window Glass > Page 12871 Power Window Motor: Service and Repair Window Regulator Motor - Rear Rear Door Window Regulator Assembly Note:The power window motor can not be serviced. It is replaced as a unit with the regulator. Remove or Disconnect Tool Required: J 34940 Rivet Gun. 1. Trim panel. Refer to Trim Panel. See: Body and Frame/Doors, Hood and Trunk/Doors 2. Water deflector. Refer to Inner Panel Water Deflector. 3. Window glass. Refer to Rear Window. 4. Window sash. 5. Glass weatherstrip. 6. Regulator assembly from door. A. Drill rivets securing the regulator to door inner panel. B. Guide regulator assembly though rear lower hole. Install or Connect 1. Regulator assembly to door. A. Guide regulator assembly though rear lower hole. B. install rivets securing the regulator to the door inner panel using J 34940. 2. Glass weatherstrip. 3. Window sash. 4. Window glass. Refer to Rear Window. 5. Water deflector. Refer to Inner Panel Water Deflector. 6. Trim panel. Refer to Trim Panel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Power Window Switch > Component Information > Locations > Power Window Switch, RH Front Power Window Switch: Locations Power Window Switch, RH Front Power Window Switches Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Power Window Switch > Component Information > Locations > Power Window Switch, RH Front > Page 12876 Rear Door Wiring On Door Trim Panel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Power Window Switch > Component Information > Locations > Power Window Switch, RH Front > Page 12877 Power Window Switch: Locations Power Windows and Door Lock Switch, Passenger Side On LH Door Trim Panel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Power Window Switch > Component Information > Locations > Power Window Switch, RH Front > Page 12878 Power Window Switch: Locations RH/LH Power Window Switches Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Power Window Switch > Component Information > Locations > Power Window Switch, RH Front > Page 12879 Rear Door Wiring On Door Trim Panel Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Power Window Switch > Component Information > Diagrams > LH Door Master Power Window Switch LH Door Master Power Window Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Power Window Switch > Component Information > Diagrams > LH Door Master Power Window Switch > Page 12882 Power Window Switch: Diagrams Power Window and Door Lock Switch Power Window And Door Lock Switch, LH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Power Window Switch > Component Information > Diagrams > LH Door Master Power Window Switch > Page 12883 Power Window And Door Lock Switch, RH Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Window Glass > Back Window Glass > Component Information > Technical Service Bulletins > Body - Vehicle Glass Distortion Information Back Window Glass: Technical Service Bulletins Body - Vehicle Glass Distortion Information INFORMATION Bulletin No.: 00-08-48-005D Date: September 10, 2010 Subject: Distortion in Outer Surface of Vehicle Glass Models: 2011 and Prior GM Passenger Cars and Trucks 2009 and Prior HUMMER H2 2010 and Prior HUMMER H3 2005-2009 Saab 9-7X 2010 and Prior Saturn Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 00-08-48-005C (Section 08 - Body and Accessories). Distortion in the outer surface of the windshield glass, door glass or backlite glass may appear after the vehicle has: - Accumulated some mileage. - Been frequently washed in automatic car washes, particularly "touchless" car washes. This distortion may look like a subtle orange peel pattern, or may look like a drip or sag etched into the surface of the glass. Some car wash solutions contain a buffered solution of hydrofluoric acid which is used to clean the glass. This should not cause a problem if used in the correct concentration. However, if not used correctly, hydrofluoric acid will attack the glass, and over time, will cause visual distortion in the outer surface of the glass which cannot be removed by scraping or polishing. If this condition is suspected, look at the area of the windshield under the wipers or below the belt seal on the side glass. The area of the glass below the wipers or belt seal will not be affected and what looks like a drip or sag may be apparent at the edge of the wiper or belt seal. You may also see a line on the glass where the wiper blade or the belt seal contacts the glass. Important The repair will require replacing the affected glass and is not a result of a defect in material or workmanship. Therefore, is not covered by New Vehicle Warranty. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Window Glass > Front Corner Window Glass > Component Information > Technical Service Bulletins > Body - Vehicle Glass Distortion Information Front Corner Window Glass: Technical Service Bulletins Body - Vehicle Glass Distortion Information INFORMATION Bulletin No.: 00-08-48-005D Date: September 10, 2010 Subject: Distortion in Outer Surface of Vehicle Glass Models: 2011 and Prior GM Passenger Cars and Trucks 2009 and Prior HUMMER H2 2010 and Prior HUMMER H3 2005-2009 Saab 9-7X 2010 and Prior Saturn Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 00-08-48-005C (Section 08 - Body and Accessories). Distortion in the outer surface of the windshield glass, door glass or backlite glass may appear after the vehicle has: - Accumulated some mileage. - Been frequently washed in automatic car washes, particularly "touchless" car washes. This distortion may look like a subtle orange peel pattern, or may look like a drip or sag etched into the surface of the glass. Some car wash solutions contain a buffered solution of hydrofluoric acid which is used to clean the glass. This should not cause a problem if used in the correct concentration. However, if not used correctly, hydrofluoric acid will attack the glass, and over time, will cause visual distortion in the outer surface of the glass which cannot be removed by scraping or polishing. If this condition is suspected, look at the area of the windshield under the wipers or below the belt seal on the side glass. The area of the glass below the wipers or belt seal will not be affected and what looks like a drip or sag may be apparent at the edge of the wiper or belt seal. You may also see a line on the glass where the wiper blade or the belt seal contacts the glass. Important The repair will require replacing the affected glass and is not a result of a defect in material or workmanship. Therefore, is not covered by New Vehicle Warranty. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Window Glass > Front Door Window Glass > System Information > Technical Service Bulletins > Body - Vehicle Glass Distortion Information Front Door Window Glass: Technical Service Bulletins Body - Vehicle Glass Distortion Information INFORMATION Bulletin No.: 00-08-48-005D Date: September 10, 2010 Subject: Distortion in Outer Surface of Vehicle Glass Models: 2011 and Prior GM Passenger Cars and Trucks 2009 and Prior HUMMER H2 2010 and Prior HUMMER H3 2005-2009 Saab 9-7X 2010 and Prior Saturn Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 00-08-48-005C (Section 08 - Body and Accessories). Distortion in the outer surface of the windshield glass, door glass or backlite glass may appear after the vehicle has: - Accumulated some mileage. - Been frequently washed in automatic car washes, particularly "touchless" car washes. This distortion may look like a subtle orange peel pattern, or may look like a drip or sag etched into the surface of the glass. Some car wash solutions contain a buffered solution of hydrofluoric acid which is used to clean the glass. This should not cause a problem if used in the correct concentration. However, if not used correctly, hydrofluoric acid will attack the glass, and over time, will cause visual distortion in the outer surface of the glass which cannot be removed by scraping or polishing. If this condition is suspected, look at the area of the windshield under the wipers or below the belt seal on the side glass. The area of the glass below the wipers or belt seal will not be affected and what looks like a drip or sag may be apparent at the edge of the wiper or belt seal. You may also see a line on the glass where the wiper blade or the belt seal contacts the glass. Important The repair will require replacing the affected glass and is not a result of a defect in material or workmanship. Therefore, is not covered by New Vehicle Warranty. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Window Glass > Front Door Window Glass > System Information > Technical Service Bulletins > Body - Vehicle Glass Distortion Information > Page 12897 Front Door Window Glass: Technical Service Bulletins Body - Side Window Chipping Information INFORMATION Bulletin No.: 06-08-64-001B Date: October 20, 2009 Subject: Information on Side Door Window Glass Chipping Caused by Hanging Vehicle Key Lock Box Models: 2010 and Prior Passenger Cars and Trucks (Including Saturn) 2010 and Prior HUMMER H2, H3 2009 and Prior Saab 9-7X Supercede: This bulletin is being revised to add vehicles and model years and to include all types of door window glass. Please discard Corporate Bulletin Number 06-08-64-001A (Section 08 - Body & Accessories). - In several warranty parts review cases, side door window glass was observed with a chip or chips on the top side of the window glass. Dealer contacts confirmed that they use a vehicle key lock box on the front side door window glass. - A random selection of side door glass returns will be conducted to confirm adherence. If a side door glass is discovered with a chip or chips in the location previously described, the side door glass will be returned to the dealership for debit. Example of Side Door Glass - DO NOT place a vehicle key lock box on a side door window glass. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Window Glass > Front Door Window Glass > System Information > Technical Service Bulletins > Body - Vehicle Glass Distortion Information > Page 12898 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Window Glass > Quarter Window Glass > Component Information > Technical Service Bulletins > Body - Vehicle Glass Distortion Information Quarter Window Glass: Technical Service Bulletins Body - Vehicle Glass Distortion Information INFORMATION Bulletin No.: 00-08-48-005D Date: September 10, 2010 Subject: Distortion in Outer Surface of Vehicle Glass Models: 2011 and Prior GM Passenger Cars and Trucks 2009 and Prior HUMMER H2 2010 and Prior HUMMER H3 2005-2009 Saab 9-7X 2010 and Prior Saturn Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 00-08-48-005C (Section 08 - Body and Accessories). Distortion in the outer surface of the windshield glass, door glass or backlite glass may appear after the vehicle has: - Accumulated some mileage. - Been frequently washed in automatic car washes, particularly "touchless" car washes. This distortion may look like a subtle orange peel pattern, or may look like a drip or sag etched into the surface of the glass. Some car wash solutions contain a buffered solution of hydrofluoric acid which is used to clean the glass. This should not cause a problem if used in the correct concentration. However, if not used correctly, hydrofluoric acid will attack the glass, and over time, will cause visual distortion in the outer surface of the glass which cannot be removed by scraping or polishing. If this condition is suspected, look at the area of the windshield under the wipers or below the belt seal on the side glass. The area of the glass below the wipers or belt seal will not be affected and what looks like a drip or sag may be apparent at the edge of the wiper or belt seal. You may also see a line on the glass where the wiper blade or the belt seal contacts the glass. Important The repair will require replacing the affected glass and is not a result of a defect in material or workmanship. Therefore, is not covered by New Vehicle Warranty. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Window Regulator > Component Information > Service and Repair > Front Window Regulator and Motor Assembly Window Regulator: Service and Repair Front Window Regulator and Motor Assembly Front Door Window Regulator Assembly Note: The power window motor can not be serviced. It is replaced as a unit with the regulator. Tool Required: J 34940 Rivet Gun Remove or Disconnect 1. Trim panel. Refer to Trim Panel. See: Body and Frame/Doors, Hood and Trunk/Doors 2. Water deflector. Refer to Inner Panel Water. 3. Inner mounting panel assembly. Refer to Inner Mounting Panel. 4. Rivets securing the regulator to the door inner panel. Drill out (2) front and (2) rear rivets. 5. Regulator from inner panel. Install or Connect 1. Regulator to inner panel. 2. Rivets securing the regulator to the door inner panel using J34940. 3. Inner mounting panel assembly. Refer to Inner Mounting Panel. 4. Water deflector. Refer to Inner Panel Water Deflector. 5. Trim panel. Refer to Trim Panel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Window Regulator > Component Information > Service and Repair > Front Window Regulator and Motor Assembly > Page 12907 Window Regulator: Service and Repair Rear Window Regulator and Motor Assembly Remove and Install Rear Door Window Regulator Assembly Note:The power window motor can not be serviced. It is replaced as a unit with the regulator. Remove or Disconnect Tool Required: J 34940 Rivet Gun. 1. Trim panel. Refer to Trim Panel. See: Body and Frame/Doors, Hood and Trunk/Doors 2. Water deflector. Refer to Inner Panel Water Deflector. 3. Window glass. Refer to Rear Window. 4. Window sash. 5. Glass weatherstrip. 6. Regulator assembly from door. A. Drill rivets securing the regulator to door inner panel. B. Guide regulator assembly though rear lower hole. Install or Connect 1. Regulator assembly to door. A. Guide regulator assembly though rear lower hole. B. install rivets securing the regulator to the door inner panel using J 34940. 2. Glass weatherstrip. 3. Window sash. 4. Window glass. Refer to Rear Window. 5. Water deflector. Refer to Inner Panel Water Deflector. 6. Trim panel. Refer to Trim Panel. Rear Window Glass Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windows > Window Regulator > Component Information > Service and Repair > Front Window Regulator and Motor Assembly > Page 12908 Rear Door Window Sash Channel Rear Door Window Weatherstrip CAUTION: To prevent personal injury, gloves should be worn when removing broken glass. Lower window Remove or Disconnect 1. Trim panel. Refer to Trim Panel. See: Body and Frame/Doors, Hood and Trunk/Doors 2. Water deflector. Refer to Inner Panel Water Deflector. 3. Window sash bolts. 4. Glass weatherstrip. Pull weatherstrip out of window frame and front run channel. 5. Lift window out of the top of door. Install or Connect 1. Slide window into glass channels through the top of door. 2. Glass weatherstrip. 3. Window sash bolts. Tighten: Window sash bolts to 1.9 Nm (17 lbs. in.). 4. Water deflector. Refer to Inner Panel Water Deflector. 5. Trim panel. Refer to Trim Panel. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > Customer Interest: > 09-08-48-006 > Sep > 09 > Body - Stain/Film On Windshield Glass Perimeter Windshield: Customer Interest Body - Stain/Film On Windshield Glass Perimeter TECHNICAL Bulletin No.: 09-08-48-006 Date: September 18, 2009 Subject: Clear Stain or Film on Inside Perimeter of Windshield Glass (Clean/Polish Glass) Models: 2010 and Prior Passenger Cars and Trucks (Including Saturn and Saab) 2010 and Prior HUMMER H2, H3 Condition Some customers may comment on a clear stain or film on the inside of the windshield glass. This condition appears along the outer edges of the glass along the top, bottom or A-pillar areas. Normal glass cleaning procedures will not remove the stain. Cause The assembly plant uses a clear sealer/primer on the outer edge of the windshield glass to improve adhesion to the urethane adhesive that bonds the windshield glass to the vehicle body. Excess sealer/primer may drip or flow onto the windshield and cause a stain. Once the sealer/primer dries, it may appear to have etched the glass. Correction Note A "white" type of toothpaste is recommended for this repair. Gel-type toothpaste may provide less satisfactory results. Use a small amount of toothpaste on a soft, cotton cloth to polish the stained area. It may be necessary to wrap the cloth around a paint stir stick or a similar tool to reach the lower corners of the windshield glass. After polishing the glass, clean the inside of the windshield glass with a clean, damp, cotton cloth and verify all of the stain is removed. Do not use any cleaners or solvents - use only clean warm water. Warranty Information (excluding Saab U.S. Models) For vehicles repaired under warranty, use: Warranty Information (Saab U.S. Models) For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > Customer Interest: > 09-08-48-006 > Sep > 09 > Body - Stain/Film On Windshield Glass Perimeter > Page 12917 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > Customer Interest: > 09-08-48-002A > Mar > 09 > Body - Marks/Stains on Windshield When Wet Windshield: Customer Interest Body - Marks/Stains on Windshield When Wet TECHNICAL Bulletin No.: 09-08-48-002A Date: March 19, 2009 Subject: Marks/Stains on Windshield When Wet (Clean Windshield) Models: 2010 and Prior Passenger Cars and Trucks (Including Saturn and Saab) 2010 and Prior HUMMER H2, H3 Supercede: This bulletin is being revised to update the models and model years. Please discard Corporate Bulletin Number 09-08-48-002 (Section 08 - Body and Accessories). Condition Some owners may comment that marks/stains appear on the windshield when the windshield is wet. Cause This condition may be caused by contact between the windshield and the vacuum hoses or other tools used in the assembly process. This contact may leave a residue that creates a water repellent surface on the glass which, in wet conditions, appear as marks/stains on the surface. Correction Important DO NOT REPLACE THE WINDSHIELD FOR THIS CONDITION. To clean the windshield, use Eastwood Glass Polishing Compound*. Follow the manufacturer's directions for product use. Use only hand tools. DO NOT USE POWER TOOLS. Parts Information Eastwood Glass Polishing Compound 1-800-343-9353 (for overseas inquiries: +1-610-705-2200) http://www.eastwoodco.com/ *We believe this source and their products to be reliable. There may be additional manufacturers of such products. General Motors does not endorse, indicate any preference for or assume any responsibility for the products from this firm or for any such items which may be available from other sources. Warranty Information For vehicles repaired under warranty, use the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > Customer Interest: > 86-11-04 > Mar > 98 > Windshield, Driver Side - Insufficient Defrosting Windshield: Customer Interest Windshield, Driver Side - Insufficient Defrosting File In Section: 1 - HVAC Bulletin No.: 86-11-04 Date: March, 1998 Subject: Insufficient Driver Side Windshield Clearing in Defrost Mode (Replace Air Distribution Duct Assembly) Models: 1995-96 Chevrolet and GMC C/K Models Condition Some owners may comment that windshield clearing on the driver's side while in the defrost mode is not up to their expectations. Cause Airflow from the defroster grille outlet effectively clears the windshield and meets all manufacturer's and federal standards. However, to better meet customer expectations, design changes have been made to enhance airflow and clearing. Correction Replace the air distribution duct assembly using the part number listed. Use the Service Procedure in Section 1A of the Service Manual. Parts Information P/N Description Qty 15002895 Duct Asm. - Air 1 Distribution Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time D1506 Duct, Air Use Published Distribution Outlet - Labor Operation R&R; or Replace Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Windshield: > 06-08-43-003C > Feb > 11 > Glass/Body - Windshield Wiper Performance Windshield: All Technical Service Bulletins Glass/Body - Windshield Wiper Performance INFORMATION Bulletin No.: 06-08-43-003C Date: February 21, 2011 Subject: Windshield Wiper Performance, Cleaning Instructions and Maintenance Models: 2012 and Prior GM Passenger Cars and Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2010 and Prior Isuzu Medium Duty Trucks 2005-2009 Saab 9-7X Supercede: This bulletin is being revised to add the 2011 and 2012 model year. Please discard Corporate Bulletin Number 06-08-43-003B (Section 08 - Body and Accessories). Wiper Concerns Most concerns about windshield wiper performance are the result of dirty wiper blades, damaged wiper blades, or worn out blades that are continuing to be used beyond their useful life. Depending on environmental conditions, wiper blades can have dramatic differences in lifespan. Here are some tips and guidelines to maximize wiper performance to avoid damage to the blades, and to avoid unnecessary replacements. Many wiper blades are being replaced under warranty with reviews showing there is nothing wrong with the returned blades other than a build-up of dirt. Additionally, advise the customer to review the information in their Owner Manual. Inspection and Cleaning Scheduled Maintenance - Inspect your wipers rubber blades every 4-6 months or 12,000 km (7,500 mi) for wear, cracking or contamination. - Clean the windshield and the rubber wiper blades (using the procedure below) if the blades are not clearing the glass satisfactorily. If this does not correct the problem, then replace the rubber elements. Cleaning Procedure Important Avoid getting windshield washer fluid on your hands. Wear rubber gloves or avoid direct contact with washer fluid. Important Do not use gasoline, kerosene, or petroleum based products to clean wiper blades. - Clean the rubber blades using a lint free cloth or paper towel soaked with windshield washer fluid or a mild detergent. You should see significant amounts of dirt being removed on the cloth. - Be sure to wash the windshield thoroughly when you clean the blades. Bugs, road grime, sap and a buildup of car wash/wax treatments may additionally cause wiper streaking. Tip For a larger scale buildup on the windshield, use a non-abrasive cleaner such as Bon-Ami* (www.faultless.com) cleanser with a wet sponge, being sure to use plenty of water to avoid scratching the glass. Flush the surface and body panels completely. Tip For day-to-day exterior glass cleaning and to maintain a streak free appearance, suggest Vehicle Care Glass Cleaner, P/N 88862560 (in Canada, 992727). This product is an easy to use foaming cleaner that quickly removes dirt and grime from glass surfaces. Tip Interior glass should be cleaned with plain, clean water to eliminate any film or haze on the window and help prevent fogging, a major customer dissatisfier. Refer to Corporate Bulletin Number 03-00-89-006D for more information. The New Vehicle Pre-Delivery Inspection form also recommends using plain water to clean interior glass. *"We believe this material to be reliable. There may be additional manufacturers of such material. General Motors does not endorse, indicate any preference for or assume any responsibility for the products or equipment from these firms or any such items which may be available from other sources. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Windshield: > 06-08-43-003C > Feb > 11 > Glass/Body - Windshield Wiper Performance > Page 12931 Avoiding Wiper Damage The following are major contributors to wiper damage. Some of these you can control and others are environmental concerns. - Extremely dusty areas (such as driving on dirt roads) may cause the wipers rubber edge to wear quickly and unevenly. - Sand and salt used on roads for increasing winter traction and ice control will cause the wiper blades to wear quicker. Areas with significant snowfall require more frequent blade replacements. - Heat and time may cause the rubber blades to take a "permanent set" resulting in the rubber not flexing and turning over uniformly. This condition may result in streaking and/or unwiped areas. - Rubber blades are easily cut or torn when using ice scrapers. Likewise pulling blades up off a frozen windshield can tear the rubber. Exercise caution when clearing ice and snow. - Using your wipers to "wear through" frost and ice, instead of allowing the defrosters to melt the ice, can dull, nick or tear the rubber blades. - Banging wipers on the glass to remove ice and snow may cause the blade to bend, dislodging the rubber and causing potential scratching of the windshield. - Ice can form in the pin joints of the wipers, which can cause streaking and unwiped areas. To remove ice from pin joints, compress the blade and rubber edge with your hand to loosen the frozen joints. Consider using Winter Blades that have a rubber cover to avoid this condition. Note GM does not recommend the use of any spray on/wipe on windshield treatments or washer fluid additives. The variation in friction that results on the glass from the use of these products causes wipers to chatter and have premature wear. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Windshield: > 00-08-48-005D > Sep > 10 > Body - Vehicle Glass Distortion Information Windshield: All Technical Service Bulletins Body - Vehicle Glass Distortion Information INFORMATION Bulletin No.: 00-08-48-005D Date: September 10, 2010 Subject: Distortion in Outer Surface of Vehicle Glass Models: 2011 and Prior GM Passenger Cars and Trucks 2009 and Prior HUMMER H2 2010 and Prior HUMMER H3 2005-2009 Saab 9-7X 2010 and Prior Saturn Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 00-08-48-005C (Section 08 - Body and Accessories). Distortion in the outer surface of the windshield glass, door glass or backlite glass may appear after the vehicle has: - Accumulated some mileage. - Been frequently washed in automatic car washes, particularly "touchless" car washes. This distortion may look like a subtle orange peel pattern, or may look like a drip or sag etched into the surface of the glass. Some car wash solutions contain a buffered solution of hydrofluoric acid which is used to clean the glass. This should not cause a problem if used in the correct concentration. However, if not used correctly, hydrofluoric acid will attack the glass, and over time, will cause visual distortion in the outer surface of the glass which cannot be removed by scraping or polishing. If this condition is suspected, look at the area of the windshield under the wipers or below the belt seal on the side glass. The area of the glass below the wipers or belt seal will not be affected and what looks like a drip or sag may be apparent at the edge of the wiper or belt seal. You may also see a line on the glass where the wiper blade or the belt seal contacts the glass. Important The repair will require replacing the affected glass and is not a result of a defect in material or workmanship. Therefore, is not covered by New Vehicle Warranty. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Windshield: > 09-08-48-006 > Sep > 09 > Body - Stain/Film On Windshield Glass Perimeter Windshield: All Technical Service Bulletins Body - Stain/Film On Windshield Glass Perimeter TECHNICAL Bulletin No.: 09-08-48-006 Date: September 18, 2009 Subject: Clear Stain or Film on Inside Perimeter of Windshield Glass (Clean/Polish Glass) Models: 2010 and Prior Passenger Cars and Trucks (Including Saturn and Saab) 2010 and Prior HUMMER H2, H3 Condition Some customers may comment on a clear stain or film on the inside of the windshield glass. This condition appears along the outer edges of the glass along the top, bottom or A-pillar areas. Normal glass cleaning procedures will not remove the stain. Cause The assembly plant uses a clear sealer/primer on the outer edge of the windshield glass to improve adhesion to the urethane adhesive that bonds the windshield glass to the vehicle body. Excess sealer/primer may drip or flow onto the windshield and cause a stain. Once the sealer/primer dries, it may appear to have etched the glass. Correction Note A "white" type of toothpaste is recommended for this repair. Gel-type toothpaste may provide less satisfactory results. Use a small amount of toothpaste on a soft, cotton cloth to polish the stained area. It may be necessary to wrap the cloth around a paint stir stick or a similar tool to reach the lower corners of the windshield glass. After polishing the glass, clean the inside of the windshield glass with a clean, damp, cotton cloth and verify all of the stain is removed. Do not use any cleaners or solvents - use only clean warm water. Warranty Information (excluding Saab U.S. Models) For vehicles repaired under warranty, use: Warranty Information (Saab U.S. Models) For vehicles repaired under warranty, use the table. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Windshield: > 09-08-48-006 > Sep > 09 > Body - Stain/Film On Windshield Glass Perimeter > Page 12940 Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Windshield: > 09-08-48-002A > Mar > 09 > Body - Marks/Stains on Windshield When Wet Windshield: All Technical Service Bulletins Body - Marks/Stains on Windshield When Wet TECHNICAL Bulletin No.: 09-08-48-002A Date: March 19, 2009 Subject: Marks/Stains on Windshield When Wet (Clean Windshield) Models: 2010 and Prior Passenger Cars and Trucks (Including Saturn and Saab) 2010 and Prior HUMMER H2, H3 Supercede: This bulletin is being revised to update the models and model years. Please discard Corporate Bulletin Number 09-08-48-002 (Section 08 - Body and Accessories). Condition Some owners may comment that marks/stains appear on the windshield when the windshield is wet. Cause This condition may be caused by contact between the windshield and the vacuum hoses or other tools used in the assembly process. This contact may leave a residue that creates a water repellent surface on the glass which, in wet conditions, appear as marks/stains on the surface. Correction Important DO NOT REPLACE THE WINDSHIELD FOR THIS CONDITION. To clean the windshield, use Eastwood Glass Polishing Compound*. Follow the manufacturer's directions for product use. Use only hand tools. DO NOT USE POWER TOOLS. Parts Information Eastwood Glass Polishing Compound 1-800-343-9353 (for overseas inquiries: +1-610-705-2200) http://www.eastwoodco.com/ *We believe this source and their products to be reliable. There may be additional manufacturers of such products. General Motors does not endorse, indicate any preference for or assume any responsibility for the products from this firm or for any such items which may be available from other sources. Warranty Information For vehicles repaired under warranty, use the table above. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Windshield: > 83-15-16 > Oct > 98 > New Windshield/Glass Urethane Adhesive Caulking Kit Windshield: All Technical Service Bulletins New Windshield/Glass Urethane Adhesive Caulking Kit File In Section: 10 - Body Bulletin No.: 83-15-16 Date: October, 1998 INFORMATION Subject: New Windshield and Stationary Glass Urethane Adhesive Caulking Kit Models: 1990-99 All Passenger Cars and Trucks As a result of a change from standard viscosity urethane to high-viscosity urethane, a new Urethane Adhesive Caulking Kit, P/N 12346392, is now available from GMSPO. This kit contains the "High Viscosity" Urethane Adhesive for thicker and more consistent bead size applications. When applied properly, this new high viscosity urethane in many instances will eliminate the need for depth setting blocks or the damming material to control squeeze out. The following is the contents of the new kit: Like the standard viscosity urethane contained in kit (P/N 12346284) that it replaces, it is a one-part, moisture cure product with curing times that vary as a result of changes in either temperature or humidity. THE REQUIRED TIME FOR THIS NEW ONE-PART MATERIAL to ensure a safe installation of stationary glass before returning the vehicle to the customer, IS A MINIMUM OF SIX (6) HOURS AT 70°F (21°C) AND 30% RELATIVE HUMIDITY. Alternate equivalent materials for this kit may be available from a local glass repair shop under the following product numbers: Other manufacturers of Urethane Adhesive that have documented their ability to meet or exceed General Motors specification # 3651M (Performance Requirements for Stationary Glass Bonding Adhesive System Service) are also considered to be equivalent to GM Kit (P/N 12346392). In previously published Corporate Bulletin Number 73-10-54, increasing customer demands for faster service have resulted in quicker two-part urethane adhesives to be made available. Essex Beta Seal U216* (two-part urethane adhesive) also meets the General Motors 3651M Specification and can be Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Windshield: > 83-15-16 > Oct > 98 > New Windshield/Glass Urethane Adhesive Caulking Kit > Page 12949 used when the customer demands quicker repair of the vehicle than the above described one-part product can provide. This two-part, chemical cure product requires ONE (1) TO ONE-AND-ONE-HALF (1-1/2) HOURS FOR CURING BEFORE RETURNING THE VEHICLE TO THE CUSTOMER. This two-part product also requires primers on the glass and pinchweld surfaces. The primers and applicator daubers are not included with this two-part product and therefore, must be purchased separately. In addition, this two-part product requires a special applicator (gun) for proper mixing and dispensing of the adhesive. Important: The U216 product is NOT available from GMSPO and must be obtained locally. * We believe this source and their products to be reliable. There may be additional manufacturers of such products. General Motors does not endorse, indicate any preference for or assume any responsibility for the products from this firm or for any such products which may be available from other sources. When using either of the above described products, make sure to follow the manufacturer's directions for application and drying times. For information regarding the removal and installation of stationary glass, consult the appropriate Service Manual. Parts information P/N Description 12346392 Urethane Adhesive Caulking Kit Parts are expected to be available from GMSPO, 10/12/98. Important: The previously recommended adhesive kit (P/N 12346284) will no longer be available from GMSPO once inventory is exhausted. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Windshield: > 86-11-04 > Mar > 98 > Windshield, Driver Side - Insufficient Defrosting Windshield: All Technical Service Bulletins Windshield, Driver Side - Insufficient Defrosting File In Section: 1 - HVAC Bulletin No.: 86-11-04 Date: March, 1998 Subject: Insufficient Driver Side Windshield Clearing in Defrost Mode (Replace Air Distribution Duct Assembly) Models: 1995-96 Chevrolet and GMC C/K Models Condition Some owners may comment that windshield clearing on the driver's side while in the defrost mode is not up to their expectations. Cause Airflow from the defroster grille outlet effectively clears the windshield and meets all manufacturer's and federal standards. However, to better meet customer expectations, design changes have been made to enhance airflow and clearing. Correction Replace the air distribution duct assembly using the part number listed. Use the Service Procedure in Section 1A of the Service Manual. Parts Information P/N Description Qty 15002895 Duct Asm. - Air 1 Distribution Parts are currently available from GMSPO. Warranty Information For vehicles repaired under warranty, use: Labor Operation Description Labor Time D1506 Duct, Air Use Published Distribution Outlet - Labor Operation R&R; or Replace Time Important: Labor operation is coded to base vehicle coverage in the warranty system. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Windshield: > 72-05-04 > Aug > 97 > Warranty - Guidelines for Claiming Windshield Replace Windshield: All Technical Service Bulletins Warranty - Guidelines for Claiming Windshield Replace File In Section: Warranty Administration Bulletin No.: 72-05-04 Date: August, 1997 WARRANTY ADMINISTRATION Subject: Guidelines for Claiming C0034 - Windshield Replacement Models: 1989-98 Passenger Cars and Light Duty Trucks The purpose of this bulletin is to provide retail and wholesale service personnel with guidelines for using the above subject labor operations. In an effort to understand the windshield replacements, the following two phase approval process is being implemented. We feel this approach will allow GM to be responsive to repair decisions on vehicles over 10,000 miles (16,000KMS), while providing you, our dealers, the empowerment to address customer needs on those cases requiring repairs early in the vehicle's life, under 10,000 miles (16,000KMS). Effective with repair orders dated on or after September 1, 1997, dealers are to be guided by the following: ^ Windshield replacement on vehicles under 10,000 miles (16,0OOKMS) can only be made after Service Management inspection, review and approval. This approval must be noted on the repair order clearly identifying the defect and reason for replacement. This comment must be submitted in the comment field of the claim for engineering review. ^ Windshield replacement on vehicles over 10,000 miles (16,000KMS) can only be made after Service Management inspection, review and approval from the divisional service representative. Vehicles may be required to be held for wholesale inspection. This approval must be noted on the repair order clearly identifying the defect and reason for replacement. This comment must be submitted in the comment field of the claim for engineering review. The claim will require wholesale authorization for payment. Additional Requirements ^ Windshields replaced must be held for the normal parts retention period and the defect should be clearly identified on the glass by means of tape and/or a grease pencil. ^ Sublet windshield replacements, like other sublet repairs are to be claimed for actual dealership cost less any discounts and or allowances offered. Sublet repairs cannot exceed the normal allowance provided to the dealership had the repair been completed in-house. See your GM Policy and Procedure Manual for the complete guidelines. Windshields damaged by normal wear, road hazards, vandalism, or other physical damage are not eligible for warranty coverage. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Windshield: > 73-10-54 > May > 97 > Windshield - Two-Part Urethane Adhesive For Installation Windshield: All Technical Service Bulletins Windshield - Two-Part Urethane Adhesive For Installation File In Section: 10 - Body Bulletin No.: 73-10-54 Date: May, 1997 INFORMATION Subject: Two-Part Urethane Adhesive For Windshield Installations Models: 1997 And Prior Passenger Cars and Trucks (Using Urethane Adhesive To Retain Windshields) General Motors passenger cars and trucks use urethane adhesive as a means to retain the windshield in the body opening. The urethane adhesive is used to bond the windshield in the opening, increasing vehicle structure. The current recommended urethane adhesive, GM P/N 12346284, is a one-part moisture cure product that requires a minimum curing period of 6 hours at room temperature before returning the vehicle to the customer. Increasing customer demands for faster service in recent years have resulted in quicker cure two-part urethane adhesives. Essex Beta Seal U216* (two-part urethane adhesive) meets the General Motors 3651M Specification (Performance Requirements for Stationary Glass Bonding Adhesive System Service) and can be used when the customer demands quicker repair of the vehicle than the current one-part materials can provide. Either of these products can be used when glass replacement is performed. The differences between these products are as follows: The CURRENT URETHANE ADHESIVE KIT, GM P/N 12346284, IS A ONE-PART ADHESIVE. It includes the necessary glass and pinchweld primers and is specified in Service Manuals for General Motors' vehicles. Since this is a "moisture cure" product, the curing time for this one-part material will vary with changes to either temperature or humidity. The REQUIRED TIME FOR THIS ONE-PART MATERIAL to ensure a safe installation of stationary glass before returning the vehicle to the customer IS A MINIMUM OF SIX (6) HOURS AT 70°F (21°C) AND 30% RELATIVE HUMIDITY. ESSEX BETA SEAL U216 IS A TWO-PART ADHESIVE MATERIAL THAT PROVIDES FOR A ONE (1) TO ONE AND ONE HALF (11/2) HOUR CURE BEFORE RETURNING THE VEHICLE TO THE CUSTOMER. This product also requires primers on the glass and pinchweld surfaces. This product requires a special applicator for the mixing and dispensing of the adhesive. When using this (or any) product, make sure to follow the manufacturer's directions for application and drying times. Parts Information Parts are currently available from GMSPO. * We believe this source and their product to be reliable. There may be additional manufacturers of such products. General Motors does not endorse, indicate any preference for or assume any responsibility for the products from this firm or for any such products which may be available from other sources. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > All Other Service Bulletins for Windshield: > 06-08-43-003C > Feb > 11 > Glass/Body - Windshield Wiper Performance Windshield: All Technical Service Bulletins Glass/Body - Windshield Wiper Performance INFORMATION Bulletin No.: 06-08-43-003C Date: February 21, 2011 Subject: Windshield Wiper Performance, Cleaning Instructions and Maintenance Models: 2012 and Prior GM Passenger Cars and Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2010 and Prior Isuzu Medium Duty Trucks 2005-2009 Saab 9-7X Supercede: This bulletin is being revised to add the 2011 and 2012 model year. Please discard Corporate Bulletin Number 06-08-43-003B (Section 08 - Body and Accessories). Wiper Concerns Most concerns about windshield wiper performance are the result of dirty wiper blades, damaged wiper blades, or worn out blades that are continuing to be used beyond their useful life. Depending on environmental conditions, wiper blades can have dramatic differences in lifespan. Here are some tips and guidelines to maximize wiper performance to avoid damage to the blades, and to avoid unnecessary replacements. Many wiper blades are being replaced under warranty with reviews showing there is nothing wrong with the returned blades other than a build-up of dirt. Additionally, advise the customer to review the information in their Owner Manual. Inspection and Cleaning Scheduled Maintenance - Inspect your wipers rubber blades every 4-6 months or 12,000 km (7,500 mi) for wear, cracking or contamination. - Clean the windshield and the rubber wiper blades (using the procedure below) if the blades are not clearing the glass satisfactorily. If this does not correct the problem, then replace the rubber elements. Cleaning Procedure Important Avoid getting windshield washer fluid on your hands. Wear rubber gloves or avoid direct contact with washer fluid. Important Do not use gasoline, kerosene, or petroleum based products to clean wiper blades. - Clean the rubber blades using a lint free cloth or paper towel soaked with windshield washer fluid or a mild detergent. You should see significant amounts of dirt being removed on the cloth. - Be sure to wash the windshield thoroughly when you clean the blades. Bugs, road grime, sap and a buildup of car wash/wax treatments may additionally cause wiper streaking. Tip For a larger scale buildup on the windshield, use a non-abrasive cleaner such as Bon-Ami* (www.faultless.com) cleanser with a wet sponge, being sure to use plenty of water to avoid scratching the glass. Flush the surface and body panels completely. Tip For day-to-day exterior glass cleaning and to maintain a streak free appearance, suggest Vehicle Care Glass Cleaner, P/N 88862560 (in Canada, 992727). This product is an easy to use foaming cleaner that quickly removes dirt and grime from glass surfaces. Tip Interior glass should be cleaned with plain, clean water to eliminate any film or haze on the window and help prevent fogging, a major customer dissatisfier. Refer to Corporate Bulletin Number 03-00-89-006D for more information. The New Vehicle Pre-Delivery Inspection form also recommends using plain water to clean interior glass. *"We believe this material to be reliable. There may be additional manufacturers of such material. General Motors does not endorse, indicate any preference for or assume any responsibility for the products or equipment from these firms or any such items which may be available from other sources. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > All Other Service Bulletins for Windshield: > 06-08-43-003C > Feb > 11 > Glass/Body - Windshield Wiper Performance > Page 12967 Avoiding Wiper Damage The following are major contributors to wiper damage. Some of these you can control and others are environmental concerns. - Extremely dusty areas (such as driving on dirt roads) may cause the wipers rubber edge to wear quickly and unevenly. - Sand and salt used on roads for increasing winter traction and ice control will cause the wiper blades to wear quicker. Areas with significant snowfall require more frequent blade replacements. - Heat and time may cause the rubber blades to take a "permanent set" resulting in the rubber not flexing and turning over uniformly. This condition may result in streaking and/or unwiped areas. - Rubber blades are easily cut or torn when using ice scrapers. Likewise pulling blades up off a frozen windshield can tear the rubber. Exercise caution when clearing ice and snow. - Using your wipers to "wear through" frost and ice, instead of allowing the defrosters to melt the ice, can dull, nick or tear the rubber blades. - Banging wipers on the glass to remove ice and snow may cause the blade to bend, dislodging the rubber and causing potential scratching of the windshield. - Ice can form in the pin joints of the wipers, which can cause streaking and unwiped areas. To remove ice from pin joints, compress the blade and rubber edge with your hand to loosen the frozen joints. Consider using Winter Blades that have a rubber cover to avoid this condition. Note GM does not recommend the use of any spray on/wipe on windshield treatments or washer fluid additives. The variation in friction that results on the glass from the use of these products causes wipers to chatter and have premature wear. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > All Other Service Bulletins for Windshield: > 00-08-48-005D > Sep > 10 > Body - Vehicle Glass Distortion Information Windshield: All Technical Service Bulletins Body - Vehicle Glass Distortion Information INFORMATION Bulletin No.: 00-08-48-005D Date: September 10, 2010 Subject: Distortion in Outer Surface of Vehicle Glass Models: 2011 and Prior GM Passenger Cars and Trucks 2009 and Prior HUMMER H2 2010 and Prior HUMMER H3 2005-2009 Saab 9-7X 2010 and Prior Saturn Supercede: This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 00-08-48-005C (Section 08 - Body and Accessories). Distortion in the outer surface of the windshield glass, door glass or backlite glass may appear after the vehicle has: - Accumulated some mileage. - Been frequently washed in automatic car washes, particularly "touchless" car washes. This distortion may look like a subtle orange peel pattern, or may look like a drip or sag etched into the surface of the glass. Some car wash solutions contain a buffered solution of hydrofluoric acid which is used to clean the glass. This should not cause a problem if used in the correct concentration. However, if not used correctly, hydrofluoric acid will attack the glass, and over time, will cause visual distortion in the outer surface of the glass which cannot be removed by scraping or polishing. If this condition is suspected, look at the area of the windshield under the wipers or below the belt seal on the side glass. The area of the glass below the wipers or belt seal will not be affected and what looks like a drip or sag may be apparent at the edge of the wiper or belt seal. You may also see a line on the glass where the wiper blade or the belt seal contacts the glass. Important The repair will require replacing the affected glass and is not a result of a defect in material or workmanship. Therefore, is not covered by New Vehicle Warranty. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > All Other Service Bulletins for Windshield: > 83-15-16 > Oct > 98 > New Windshield/Glass Urethane Adhesive Caulking Kit Windshield: All Technical Service Bulletins New Windshield/Glass Urethane Adhesive Caulking Kit File In Section: 10 - Body Bulletin No.: 83-15-16 Date: October, 1998 INFORMATION Subject: New Windshield and Stationary Glass Urethane Adhesive Caulking Kit Models: 1990-99 All Passenger Cars and Trucks As a result of a change from standard viscosity urethane to high-viscosity urethane, a new Urethane Adhesive Caulking Kit, P/N 12346392, is now available from GMSPO. This kit contains the "High Viscosity" Urethane Adhesive for thicker and more consistent bead size applications. When applied properly, this new high viscosity urethane in many instances will eliminate the need for depth setting blocks or the damming material to control squeeze out. The following is the contents of the new kit: Like the standard viscosity urethane contained in kit (P/N 12346284) that it replaces, it is a one-part, moisture cure product with curing times that vary as a result of changes in either temperature or humidity. THE REQUIRED TIME FOR THIS NEW ONE-PART MATERIAL to ensure a safe installation of stationary glass before returning the vehicle to the customer, IS A MINIMUM OF SIX (6) HOURS AT 70°F (21°C) AND 30% RELATIVE HUMIDITY. Alternate equivalent materials for this kit may be available from a local glass repair shop under the following product numbers: Other manufacturers of Urethane Adhesive that have documented their ability to meet or exceed General Motors specification # 3651M (Performance Requirements for Stationary Glass Bonding Adhesive System Service) are also considered to be equivalent to GM Kit (P/N 12346392). In previously published Corporate Bulletin Number 73-10-54, increasing customer demands for faster service have resulted in quicker two-part urethane adhesives to be made available. Essex Beta Seal U216* (two-part urethane adhesive) also meets the General Motors 3651M Specification and can be Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > All Other Service Bulletins for Windshield: > 83-15-16 > Oct > 98 > New Windshield/Glass Urethane Adhesive Caulking Kit > Page 12976 used when the customer demands quicker repair of the vehicle than the above described one-part product can provide. This two-part, chemical cure product requires ONE (1) TO ONE-AND-ONE-HALF (1-1/2) HOURS FOR CURING BEFORE RETURNING THE VEHICLE TO THE CUSTOMER. This two-part product also requires primers on the glass and pinchweld surfaces. The primers and applicator daubers are not included with this two-part product and therefore, must be purchased separately. In addition, this two-part product requires a special applicator (gun) for proper mixing and dispensing of the adhesive. Important: The U216 product is NOT available from GMSPO and must be obtained locally. * We believe this source and their products to be reliable. There may be additional manufacturers of such products. General Motors does not endorse, indicate any preference for or assume any responsibility for the products from this firm or for any such products which may be available from other sources. When using either of the above described products, make sure to follow the manufacturer's directions for application and drying times. For information regarding the removal and installation of stationary glass, consult the appropriate Service Manual. Parts information P/N Description 12346392 Urethane Adhesive Caulking Kit Parts are expected to be available from GMSPO, 10/12/98. Important: The previously recommended adhesive kit (P/N 12346284) will no longer be available from GMSPO once inventory is exhausted. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > All Other Service Bulletins for Windshield: > 72-05-04 > Aug > 97 > Warranty - Guidelines for Claiming Windshield Replace Windshield: All Technical Service Bulletins Warranty - Guidelines for Claiming Windshield Replace File In Section: Warranty Administration Bulletin No.: 72-05-04 Date: August, 1997 WARRANTY ADMINISTRATION Subject: Guidelines for Claiming C0034 - Windshield Replacement Models: 1989-98 Passenger Cars and Light Duty Trucks The purpose of this bulletin is to provide retail and wholesale service personnel with guidelines for using the above subject labor operations. In an effort to understand the windshield replacements, the following two phase approval process is being implemented. We feel this approach will allow GM to be responsive to repair decisions on vehicles over 10,000 miles (16,000KMS), while providing you, our dealers, the empowerment to address customer needs on those cases requiring repairs early in the vehicle's life, under 10,000 miles (16,000KMS). Effective with repair orders dated on or after September 1, 1997, dealers are to be guided by the following: ^ Windshield replacement on vehicles under 10,000 miles (16,0OOKMS) can only be made after Service Management inspection, review and approval. This approval must be noted on the repair order clearly identifying the defect and reason for replacement. This comment must be submitted in the comment field of the claim for engineering review. ^ Windshield replacement on vehicles over 10,000 miles (16,000KMS) can only be made after Service Management inspection, review and approval from the divisional service representative. Vehicles may be required to be held for wholesale inspection. This approval must be noted on the repair order clearly identifying the defect and reason for replacement. This comment must be submitted in the comment field of the claim for engineering review. The claim will require wholesale authorization for payment. Additional Requirements ^ Windshields replaced must be held for the normal parts retention period and the defect should be clearly identified on the glass by means of tape and/or a grease pencil. ^ Sublet windshield replacements, like other sublet repairs are to be claimed for actual dealership cost less any discounts and or allowances offered. Sublet repairs cannot exceed the normal allowance provided to the dealership had the repair been completed in-house. See your GM Policy and Procedure Manual for the complete guidelines. Windshields damaged by normal wear, road hazards, vandalism, or other physical damage are not eligible for warranty coverage. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Windows and Glass > Windshield > Component Information > Technical Service Bulletins > All Other Service Bulletins for Windshield: > 73-10-54 > May > 97 > Windshield - Two-Part Urethane Adhesive For Installation Windshield: All Technical Service Bulletins Windshield - Two-Part Urethane Adhesive For Installation File In Section: 10 - Body Bulletin No.: 73-10-54 Date: May, 1997 INFORMATION Subject: Two-Part Urethane Adhesive For Windshield Installations Models: 1997 And Prior Passenger Cars and Trucks (Using Urethane Adhesive To Retain Windshields) General Motors passenger cars and trucks use urethane adhesive as a means to retain the windshield in the body opening. The urethane adhesive is used to bond the windshield in the opening, increasing vehicle structure. The current recommended urethane adhesive, GM P/N 12346284, is a one-part moisture cure product that requires a minimum curing period of 6 hours at room temperature before returning the vehicle to the customer. Increasing customer demands for faster service in recent years have resulted in quicker cure two-part urethane adhesives. Essex Beta Seal U216* (two-part urethane adhesive) meets the General Motors 3651M Specification (Performance Requirements for Stationary Glass Bonding Adhesive System Service) and can be used when the customer demands quicker repair of the vehicle than the current one-part materials can provide. Either of these products can be used when glass replacement is performed. The differences between these products are as follows: The CURRENT URETHANE ADHESIVE KIT, GM P/N 12346284, IS A ONE-PART ADHESIVE. It includes the necessary glass and pinchweld primers and is specified in Service Manuals for General Motors' vehicles. Since this is a "moisture cure" product, the curing time for this one-part material will vary with changes to either temperature or humidity. The REQUIRED TIME FOR THIS ONE-PART MATERIAL to ensure a safe installation of stationary glass before returning the vehicle to the customer IS A MINIMUM OF SIX (6) HOURS AT 70°F (21°C) AND 30% RELATIVE HUMIDITY. ESSEX BETA SEAL U216 IS A TWO-PART ADHESIVE MATERIAL THAT PROVIDES FOR A ONE (1) TO ONE AND ONE HALF (11/2) HOUR CURE BEFORE RETURNING THE VEHICLE TO THE CUSTOMER. This product also requires primers on the glass and pinchweld surfaces. This product requires a special applicator for the mixing and dispensing of the adhesive. When using this (or any) product, make sure to follow the manufacturer's directions for application and drying times. Parts Information Parts are currently available from GMSPO. * We believe this source and their product to be reliable. There may be additional manufacturers of such products. General Motors does not endorse, indicate any preference for or assume any responsibility for the products from this firm or for any such products which may be available from other sources. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Relays and Modules - Wiper and Washer Systems > Wiper Control Module > Component Information > Technical Service Bulletins > Recalls for Wiper Control Module: > NHTSA98V150001 > Jul > 98 > Recall 98V150001: Windshield Wiper Defect Wiper Control Module: Recalls Recall 98V150001: Windshield Wiper Defect Light duty pickup trucks and sport utility vehicles, 2 and 4-wheel drive. Solder joints near the wiring harness connector can crack causing the windshield wipers to work intermittently. This condition can result in inoperative wipers, reducing a driver's visibility, and increasing the risk of a vehicle crash. Dealers will replace the wiper motor circuit board and cover. Owner notification began December 15, 1998. Owners who take their vehicles to an authorized dealer on an agreed upon service date and do not receive the free remedy within a reasonable time should contact Chevrolet at 1-800-222-1020 or GMC at 1-800-462-8782. Also contact the National Highway Traffic Safety Administration's Auto Safety Hotline at 1-888-DASH-2-DOT (1-888-327-4236). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Relays and Modules - Wiper and Washer Systems > Wiper Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Control Module: > NHTSA98V150001 > Jul > 98 > Recall 98V150001: Windshield Wiper Defect Wiper Control Module: All Technical Service Bulletins Recall 98V150001: Windshield Wiper Defect Light duty pickup trucks and sport utility vehicles, 2 and 4-wheel drive. Solder joints near the wiring harness connector can crack causing the windshield wipers to work intermittently. This condition can result in inoperative wipers, reducing a driver's visibility, and increasing the risk of a vehicle crash. Dealers will replace the wiper motor circuit board and cover. Owner notification began December 15, 1998. Owners who take their vehicles to an authorized dealer on an agreed upon service date and do not receive the free remedy within a reasonable time should contact Chevrolet at 1-800-222-1020 or GMC at 1-800-462-8782. Also contact the National Highway Traffic Safety Administration's Auto Safety Hotline at 1-888-DASH-2-DOT (1-888-327-4236). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Sensors and Switches - Wiper and Washer Systems > Windshield Washer Switch > Component Information > Locations Windshield Washer Switch: Locations At Steering Column, part of Turn Signal Lever Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Sensors and Switches - Wiper and Washer Systems > Windshield Washer Switch > Component Information > Locations > Page 13004 Windshield Washer Switch: Diagrams C230: I/P HARN To HVAC HARN, Rear Window Wiper Washer SW Rear Window Wiper/Washer Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Sensors and Switches - Wiper and Washer Systems > Wiper Switch > Component Information > Locations > Rear Window Wiper & Washer Switch Cargo Lamp Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Sensors and Switches - Wiper and Washer Systems > Wiper Switch > Component Information > Locations > Rear Window Wiper & Washer Switch > Page 13009 Wiper Switch: Locations Windshield Wiper/Washer Switch At Steering Column, part of Turn Signal Lever Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Sensors and Switches - Wiper and Washer Systems > Wiper Switch > Component Information > Locations > Page 13010 Wiper Switch: Diagrams C230: I/P HARN To HVAC HARN, Rear Window Wiper Washer SW Rear Window Wiper/Washer Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Windshield Washer Pump > Component Information > Locations Auxiliary Battery Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Windshield Washer Switch > Component Information > Locations Windshield Washer Switch: Locations At Steering Column, part of Turn Signal Lever Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Windshield Washer Switch > Component Information > Locations > Page 13017 Windshield Washer Switch: Diagrams C230: I/P HARN To HVAC HARN, Rear Window Wiper Washer SW Rear Window Wiper/Washer Switch Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Blade > Component Information > Technical Service Bulletins > Glass/Body - Windshield Wiper Performance Wiper Blade: Technical Service Bulletins Glass/Body - Windshield Wiper Performance INFORMATION Bulletin No.: 06-08-43-003C Date: February 21, 2011 Subject: Windshield Wiper Performance, Cleaning Instructions and Maintenance Models: 2012 and Prior GM Passenger Cars and Trucks (including Saturn) 2010 and Prior HUMMER H2, H3 2010 and Prior Isuzu Medium Duty Trucks 2005-2009 Saab 9-7X Supercede: This bulletin is being revised to add the 2011 and 2012 model year. Please discard Corporate Bulletin Number 06-08-43-003B (Section 08 - Body and Accessories). Wiper Concerns Most concerns about windshield wiper performance are the result of dirty wiper blades, damaged wiper blades, or worn out blades that are continuing to be used beyond their useful life. Depending on environmental conditions, wiper blades can have dramatic differences in lifespan. Here are some tips and guidelines to maximize wiper performance to avoid damage to the blades, and to avoid unnecessary replacements. Many wiper blades are being replaced under warranty with reviews showing there is nothing wrong with the returned blades other than a build-up of dirt. Additionally, advise the customer to review the information in their Owner Manual. Inspection and Cleaning Scheduled Maintenance - Inspect your wipers rubber blades every 4-6 months or 12,000 km (7,500 mi) for wear, cracking or contamination. - Clean the windshield and the rubber wiper blades (using the procedure below) if the blades are not clearing the glass satisfactorily. If this does not correct the problem, then replace the rubber elements. Cleaning Procedure Important Avoid getting windshield washer fluid on your hands. Wear rubber gloves or avoid direct contact with washer fluid. Important Do not use gasoline, kerosene, or petroleum based products to clean wiper blades. - Clean the rubber blades using a lint free cloth or paper towel soaked with windshield washer fluid or a mild detergent. You should see significant amounts of dirt being removed on the cloth. - Be sure to wash the windshield thoroughly when you clean the blades. Bugs, road grime, sap and a buildup of car wash/wax treatments may additionally cause wiper streaking. Tip For a larger scale buildup on the windshield, use a non-abrasive cleaner such as Bon-Ami* (www.faultless.com) cleanser with a wet sponge, being sure to use plenty of water to avoid scratching the glass. Flush the surface and body panels completely. Tip For day-to-day exterior glass cleaning and to maintain a streak free appearance, suggest Vehicle Care Glass Cleaner, P/N 88862560 (in Canada, 992727). This product is an easy to use foaming cleaner that quickly removes dirt and grime from glass surfaces. Tip Interior glass should be cleaned with plain, clean water to eliminate any film or haze on the window and help prevent fogging, a major customer dissatisfier. Refer to Corporate Bulletin Number 03-00-89-006D for more information. The New Vehicle Pre-Delivery Inspection form also recommends using plain water to clean interior glass. *"We believe this material to be reliable. There may be additional manufacturers of such material. General Motors does not endorse, indicate any preference for or assume any responsibility for the products or equipment from these firms or any such items which may be available from other sources. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Blade > Component Information > Technical Service Bulletins > Glass/Body - Windshield Wiper Performance > Page 13022 Avoiding Wiper Damage The following are major contributors to wiper damage. Some of these you can control and others are environmental concerns. - Extremely dusty areas (such as driving on dirt roads) may cause the wipers rubber edge to wear quickly and unevenly. - Sand and salt used on roads for increasing winter traction and ice control will cause the wiper blades to wear quicker. Areas with significant snowfall require more frequent blade replacements. - Heat and time may cause the rubber blades to take a "permanent set" resulting in the rubber not flexing and turning over uniformly. This condition may result in streaking and/or unwiped areas. - Rubber blades are easily cut or torn when using ice scrapers. Likewise pulling blades up off a frozen windshield can tear the rubber. Exercise caution when clearing ice and snow. - Using your wipers to "wear through" frost and ice, instead of allowing the defrosters to melt the ice, can dull, nick or tear the rubber blades. - Banging wipers on the glass to remove ice and snow may cause the blade to bend, dislodging the rubber and causing potential scratching of the windshield. - Ice can form in the pin joints of the wipers, which can cause streaking and unwiped areas. To remove ice from pin joints, compress the blade and rubber edge with your hand to loosen the frozen joints. Consider using Winter Blades that have a rubber cover to avoid this condition. Note GM does not recommend the use of any spray on/wipe on windshield treatments or washer fluid additives. The variation in friction that results on the glass from the use of these products causes wipers to chatter and have premature wear. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Control Module > Component Information > Technical Service Bulletins > Recalls for Wiper Control Module: > NHTSA98V150001 > Jul > 98 > Recall 98V150001: Windshield Wiper Defect Wiper Control Module: Recalls Recall 98V150001: Windshield Wiper Defect Light duty pickup trucks and sport utility vehicles, 2 and 4-wheel drive. Solder joints near the wiring harness connector can crack causing the windshield wipers to work intermittently. This condition can result in inoperative wipers, reducing a driver's visibility, and increasing the risk of a vehicle crash. Dealers will replace the wiper motor circuit board and cover. Owner notification began December 15, 1998. Owners who take their vehicles to an authorized dealer on an agreed upon service date and do not receive the free remedy within a reasonable time should contact Chevrolet at 1-800-222-1020 or GMC at 1-800-462-8782. Also contact the National Highway Traffic Safety Administration's Auto Safety Hotline at 1-888-DASH-2-DOT (1-888-327-4236). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Control Module > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Control Module: > NHTSA98V150001 > Jul > 98 > Recall 98V150001: Windshield Wiper Defect Wiper Control Module: All Technical Service Bulletins Recall 98V150001: Windshield Wiper Defect Light duty pickup trucks and sport utility vehicles, 2 and 4-wheel drive. Solder joints near the wiring harness connector can crack causing the windshield wipers to work intermittently. This condition can result in inoperative wipers, reducing a driver's visibility, and increasing the risk of a vehicle crash. Dealers will replace the wiper motor circuit board and cover. Owner notification began December 15, 1998. Owners who take their vehicles to an authorized dealer on an agreed upon service date and do not receive the free remedy within a reasonable time should contact Chevrolet at 1-800-222-1020 or GMC at 1-800-462-8782. Also contact the National Highway Traffic Safety Administration's Auto Safety Hotline at 1-888-DASH-2-DOT (1-888-327-4236). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 03023 > May > 03 > Recall - Windshield Wiper Motor failure Technical Service Bulletin # 03023 Date: 030501 Recall - Windshield Wiper Motor failure File In Section: Product Recalls Bulletin No.: 03023 Date: May, 2003 PRODUCT SAFETY RECALL SUBJECT: 03023 - WINDSHIELD WIPER MOTOR FAILURE MODELS: 1994 CHEVROLET CK PICKUP, TAHOE 4WD, SUBURBAN 2WD 1995 CHEVROLET CK PICKUP, CK CREW CAB 4WD, TAHOE 4WD, SUBURBAN, ASTRO VAN 1996 CHEVROLET BLAZER, S10, CK PICKUP, CK CREW CAB, TAHOE, SUBURBAN, ASTRO VAN, 1997 CHEVROLET S10 2WD, CK CREW CAB, SUBURBAN 4WD, ASTRO VAN 1994 GMC SIERRA PICKUP, YUKON 4WD, SUBURBAN 2WD 1995 GMC SIERRA PICKUP, SIERRA CREW CAB 4WD, YUKON 4WD, SUBURBAN, SAFARI VAN 1996 GMC SONOMA, JIMMY, SIERRA PICKUP, SIERRA CREW CAB, YUKON, SUBURBAN, SAFARI VAN 1997 GMC SONOMA 2WD, SIERRA CREW CAB, SUBURBAN 4WD, SAFARI VAN 1996 OLDSMOBILE BRAVADA This recall bulletin, minus your assigned VIN listing, is being sent to you at this time in order to take care of those customers who bring their vehicle in for a malfunctioning windshield wiper motor prior to their notification of this recall. GM plans to begin notifying owners of this recall in late June 2003. That is when parts are expected to be available in sufficient quantities to support this recall. A VIN listing will be sent to dealers at that time. In the meantime, should an owner bring in one of the vehicles listed above because the windshield wiper system exhibits the conditions described in the "Condition" paragraph contained in this bulletin, check the VIN in GMVIS to determine vehicle eligibility. If the vehicle is eligible, perform service correction and submit the claim as instructed in this bulletin. CONDITION General Motors has decided that a defect, which relates to motor vehicle safety, exists in certain 1994 Chevrolet CK Pickup, Tahoe, Suburban; 1995 Chevrolet CK Pickup, CK Crew Cab, Tahoe, Suburban, Astro Van; 1996 Chevrolet Blazer, S10 Pickup, CK Pickup, CK Crew Cab. Tahoe, Suburban, Astro Van; 1997 Chevrolet S10 Pickup, CK Crew Cab, Suburban 4WD, Astro Van; 1994 GMC Sierra Pickup, Yukon, Suburban; 1995 GMC Sierra Pickup, Sierra Crew Cab, Yukon, Suburban. Safari Van; 1996 GMC Sonoma, Jimmy, Sierra Pickup, Sierra Crew Cab, Yukon, Suburban, Safari Van; 1997 GMC Sonoma, Sierra Crew Cab, Suburban 4WD, Safari Van; 1996 Oldsmobile Bravada vehicles. These vehicles may have a condition in which the windshield wiper motor may fail. These failures are the result of cracked solder joints on the controller circuit board near the wiring harness connector. Depending on which solder joints crack or the severity of the crack, the windshield wipers could work intermittently or not at all. If this were to occur in a severe weather situation, driver visibility could be reduced, which could result in a vehicle crash without prior warning. CORRECTION Dealers are to replace the wiper motor circuit board and cover. VEHICLES INVOLVED Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 03023 > May > 03 > Recall - Windshield Wiper Motor failure > Page 13044 Involved are certain 1994 Chevrolet CK Pickup, Tahoe 4WD, Suburban 2WD; 1995 Chevrolet CK Pickup, CK Crew Cab 4WD, Tahoe 4WD, Suburban, Astro Van; 1996 Chevrolet Blazer, S10, CK Pickup, CK Crew Cab, Tahoe, Suburban, Astro Van; 1997 Chevrolet S10, 2WD, CK Crew Cab, Suburban 4WD, Astro Van; 1994 GMC Sierra Pickup, Yukon 4WD, Suburban 2WD; 1995 GMC Sierra Pickup, Sierra Crew Cab 4WD, Yukon 4WD, Suburban, Safari Van; 1996 GMC Sonoma, Jimmy, Sierra Pickup, Sierra Crew Cab, Yukon, Suburban, Safari Van; 1997 GMC Sonoma 2WD, Sierra Crew Cab, Suburban 4WD, Safari Van; 1996 Oldsmobile Bravada vehicles built within the VIN breakpoints shown. IMPORTANT: Dealers should confirm vehicle eligibility through GMVIS (GM Vehicle Inquiry System) before beginning recall repairs. [Not all vehicles within the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 03023 > May > 03 > Recall - Windshield Wiper Motor failure > Page 13045 above breakpoints may be involved.] Involved vehicles have been identified by Vehicle Identification Number. Computer listings containing the complete Vehicle Identification Number, customer name and address data have been prepared, and are being furnished to involved dealers with the recall bulletin. The customer name and address data will enable dealers to follow up with customers involved in this recall. Any dealer not receiving a computer listing with the recall bulletin has no involved vehicles currently assigned. These dealer listings may contain customer names and addresses obtained from Motor Vehicle Registration Records. The use of such motor vehicle registration data for any other purpose is a violation of law in several states/provinces/countries. Accordingly, you are urged to limit the use of this listing to the follow-up necessary to complete this recall. PARTS INFORMATION Parts required to complete this recall are to be obtained from General Motors Service Parts Operations (GMSPO). Please refer to your "involved vehicles listing" before ordering parts. Normal orders should be placed on a DRO = Daily Replenishment Order. In an emergency situation, parts should be ordered on a CSO = Customer Special Order. RECALL IDENTIFICATION LABEL Place a Recall Identification Label on each vehicle corrected in accordance with the instructions outlined in this Product Recall Bulletin Each label provides a space to include the recall number and the five (5) digit dealer code of the dealer performing the recall service. This information may be inserted with a typewriter or a ballpoint pen. Put the Recall Identification Label on a clean and dry surface of the radiator core support in an area that will be visible to people servicing the vehicle. When installing the Recall Identification Label, be sure to pull the tab to allow adhesion of the clear protective covering. Additional Recall Identification Labels can be obtained from Dealer Support Materials by either ordering on the web from DWD Store. CUSTOMER REIMBURSEMENT All customer requests for reimbursement for previous repairs for the recall condition will be handled by the Customer Assistance Center, not by dealers. A General Motors Product Recall Customer Reimbursement Procedure Form is included with the original customer letter. IMPORTANT: Refer to the GM Service Policies and Procedures Manual, section 61.12, for specific procedures regarding customer reimbursement and the form. CLAIM INFORMATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 03023 > May > 03 > Recall - Windshield Wiper Motor failure > Page 13046 Submit a Product Recall Claim with the information shown. Refer to the General Motors WINS Claims Processing Manual for details on Product Recall Claim Submission. CUSTOMER NOTIFICATION Customers will be notified of this recall on their vehicles by General Motors (see copy of customer letter shown in this bulletin). DEALER RECALL RESPONSIBILITY The US National Traffic and Motor Vehicle Safety Act provides that each vehicle that is subject to a recall of this type must be adequately repaired within a reasonable time after the customer has tendered it for repair. A failure to repair within sixty days after tender of a vehicle is prima facie evidence of failure to repair within a reasonable time. If the condition is not adequately repaired within a reasonable time, the customer may be entitled to an identical or reasonably equivalent vehicle at no charge or to a refund of the purchase price less a reasonable allowance for depreciation. To avoid having to provide these burdensome remedies, every effort must be made to promptly schedule an appointment with each customer and to repair their vehicle as soon as possible. In the recall notification letters, customers are told how to contact the US National Highway Traffic Safety Administration if the recall is not completed within a reasonable time. All unsold new vehicles in dealers' possession and subject to this recall must be held and inspected/repaired per the service procedure of this recall bulletin before customers take possession of these vehicles. Dealers are to service all vehicles subject to this recall at no charge to customers, regardless of mileage, age of vehicle, or ownership, from this time forward. Customers who have recently purchased vehicles sold from your vehicle inventory, and for which there is no customer information indicated on the dealer listing, are to be contacted by the dealer. Arrangements are to be made to make the required correction according to the instructions contained in this bulletin. This could be done by mailing to such customers, a copy of the customer letter shown in this bulletin. Recall follow-up cards should not be used for this purpose, since the customer may not as yet have received the notification letter. In summary, whenever a vehicle subject to this recall enters your vehicle inventory, or is in your dealership for service in the future, you must take the steps necessary to be sure the recall correction has been made before selling or releasing the vehicle. Disclaimer Service Procedure 1. Turn the ignition key to the OFF position. 2. Remove the Connector Position Assurance (CPA) and disconnect the wiper motor electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 03023 > May > 03 > Recall - Windshield Wiper Motor failure > Page 13047 3. Remove the three screws that secure the cover to the wiper motor and remove the cover. 4. Inspect for sealant on the inside of the cover and then discard the cover and screws. Important If sealant was found on the old cover, it will be necessary to remove any old sealant from the motor housing in step 6. 5. Carefully remove the module (circuit board) from the wiper motor by lifting up on the end of the module electrical connector. 6. If necessary, remove any old sealant from the wiper motor housing (see step 4). Notice When handling the new module in the next step, be careful not to damage or bend the electrical contacts on the bottom side of the module. 7. Install the module into the wiper motor housing, making sure that the module is fully seated. When fully seated, the edges of the module circuit board will be flush (even) with the motor housing along all sides. 8. Carefully apply a bead of silicone sealant, P/N 12345739 (or GE-162 sealant or equivalent) in the groove of the NEW cover (Figure 2). Remove any excess sealant that is outside of the groove. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 03023 > May > 03 > Recall - Windshield Wiper Motor failure > Page 13048 Important Only apply enough sealant to fill the groove in the cover. 9. Install the new cover on the wiper motor housing and install the three new screws. Tighten Tighten the screws to 2.6 Nm (23 lb in). 10. Reconnect the wiper motor electrical connector to the wiper motor assembly and install the CPA. 11. Turn the ignition key to the ON position and check the wiper system for proper operation (delay/low/high/etc.). 12. Install the GM Recall Identification Label. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 03023 > May > 03 > Recall - Windshield Wiper Motor failure > Page 13049 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > NHTSA03V159000 > Apr > 03 > Recall 03V159000: Wiper Motor Circuit Board Defect Wiper Motor: Recalls Recall 03V159000: Wiper Motor Circuit Board Defect DEFECT: On certain minivans, pickup trucks, and sport utility vehicles with certain model-engine combinations, the windshield wiper motor may fail due to cracked solder joints on the controller circuit board. The windshield wipers could work intermittently or not at all. If this were to occur during bad weather, driver visibility would be reduced, which could result in a crash. REMEDY: Dealers will replace the wiper motor circuit board and cover. The manufacturer has reported that owner notification is expected to begin during late June 2003. Owners may contact Chevrolet at 1-800-222-1020, GMC at 1-800-462-8782, or Oldsmobile at 1-800-442-6537. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 02054 > Feb > 03 > Campaign - Winshield Wiper Motor Failure Technical Service Bulletin # 02054 Date: 030201 Campaign - Winshield Wiper Motor Failure File In Section: 08-Body & Access. Bulletin No.: 02054 Date: February, 2003 SPECIAL POLICY SUBJECT: 02054 - SPECIAL POLICY ADJUSTMENT - WINDSHIELD WIPER MOTOR FAILURES MODELS: 1997 CHEVROLET BLAZER, S10 1995-1997 CHEVROLET ASTRO, C/K CREW CAB 1994-1997 C/K PICKUP, TAHOE, SUBURBAN 1997 GMC JIMMY, SONOMA 1995-1997 GMC SAFARI, SIERRA CREW CAB 1994-1997 GMC SIERRA PICKUP, YUKON, SUBURBAN 1997 OLDSMOBILE BRAVADA (EXCLUDING VEHICLES INVOLVED IN RECALL 98043) CONDITION Some customers of 1997 Chevrolet Blazer, S10 Pickup; 1995-1997 Chevrolet Astro, C/K Crew Cab; 1994-1997 C/K Pickup, Tahoe, Suburban; 1997 GMC Jimmy, Sonoma; 1995-1997 GMC Safari, Sierra Crew Cab; 1994-1997 GMC Sierra Pickup, Yukon, Suburban; and 1997 Oldsmobile Bravada vehicles not involved in recall 98043 may experience a windshield wiper failure due to cracked solder joints on the controller circuit board. SPECIAL POLICY ADJUSTMENT This special policy covers the condition described above for a period of 7 years or 70,000 miles (112,000 km), whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership, or for those vehicles currently outside of this coverage, until February 29, 2004. The repairs will be made at no charge to the customer. For vehicles covered by Vehicle Service Contracts, all eligible claims with repair orders on or after February 21, 2003 are covered by this special policy and must be submitted using the labor operation codes provided with this bulletin. Claims with repair orders prior to February 21, 2003 must be submitted to the Service Contract provider. VEHICLES INVOLVED Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 02054 > Feb > 03 > Campaign - Winshield Wiper Motor Failure > Page 13058 Involved are certain 1997 Chevrolet Blazer, 510 Pickup; 1995-1997 Chevrolet Astro, C/K Crew Cab; 1994-1997 C/K Pickup, Tahoe, Suburban; 1997 GMC Jimmy, Sonoma; 1995-1997 GMC Safari, Sierra Crew Cab; 1994-1997 GMC Sierra Pickup, Yukon, Suburban; and 1997 Oldsmobile Bravada vehicles not covered by recall 98043 and built within the VIN breakpoints shown. PARTS INFORMATION Parts required to complete this special policy are to be obtained from General Motors Service Parts Operations (GMPSO). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 02054 > Feb > 03 > Campaign - Winshield Wiper Motor Failure > Page 13059 CUSTOMER NOTIFICATION Customers will be notified of this special policy on their vehicles by General Motors (see copy of typical customer letter included with this bulletin - actual divisional letter may vary slightly). SERVICE PROCEDURE 1. Turn the ignition key to the OFF position. 2. Remove the Connector Position Assurance (CPA) and disconnect the wiper motor electrical connector. 3. Remove the three screws that secure the cover to the wiper motor and remove the cover. 4. Inspect for sealant on the inside of the cover and then discard the cover and screws. Important If sealant was found on the old cover, it will be necessary to remove any old sealant from the motor housing in step 6. 5. Carefully remove the module (circuit board) from the wiper motor by lifting up on the end of the module electrical connector. 6. If necessary, remove any old sealant from the wiper motor housing (see step 4). Notice When handling the new module in the next step, be careful not to damage or bend the electrical contacts on the bottom side of the module. 7. Install the module into the wiper motor housing, making sure that the module is fully seated. When fully seated, the edges of the module circuit board will be flush (even) with the motor housing along all sides. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 02054 > Feb > 03 > Campaign - Winshield Wiper Motor Failure > Page 13060 8. Carefully apply a bead of silicone sealant, P/N 12345739 (or GE-162 sealant or equivalent) in the groove of the NEW cover (Figure 2). Remove any excess sealant that is outside of the groove. Important Only apply enough sealant to fill the groove in the cover. 9. Install the new cover on the wiper motor housing and install the three new screws. Tighten the screws to 2.6 Nm (23 lb in). 10. Reconnect the wiper motor electrical connector to the wiper motor assembly and install the CPA. 11. Turn the ignition key to the ON position and check the wiper system for proper operation (delay/low/high/etc.). CLAIM INFORMATION For vehicles repaired under the terms of this special policy, submit a claim with the information indicated. CUSTOMER REIMBURSEMENT Customer requests for reimbursement of previously paid repairs to correct a failed wiper motor are to be submitted prior to or by February 29, 2004 (this time limitation may be longer depending upon the law in your state/province/country). Repairs must have occurred before March 14, 2003. When a customer requests reimbursement, they must provide the following: - Proof of ownership at time of repair. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 02054 > Feb > 03 > Campaign - Winshield Wiper Motor Failure > Page 13061 - Original paid receipt confirming the amount of unreimbursed repair expense(s) (including Service Contract deductibles), a description of the repair, and the person or entity performing the repair. Customers from the States of California, Connecticut, Virginia, and Wisconsin must submit requests for reimbursement directly to the applicable Division per instructions in the owner letter. If the work was done by someone other than a GM dealership, the amount of reimbursement will be limited to the amount that the repair would have cost GM to have it completed by a GM dealership. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 02054 > Feb > 03 > Campaign - Winshield Wiper Motor Failure > Page 13062 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 02054 > Feb > 03 > Campaign - Winshield Wiper Motor Failure > Page 13063 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 98043 > Sep > 98 > Recall - Windshield Wiper Motor Failures Technical Service Bulletin # 98043 Date: 980901 Recall - Windshield Wiper Motor Failures File In Section: Product Campaigns Bulletin No.: 98043 Date: September, 1998 PRODUCT RECALL CAMPAIGN PRODUCT SAFETY CAMPAIGN SUBJECT: 96043 - WINDSHIELD WIPER MOTOR FAILURES MODELS: 1994-96 CHEVROLET AND GMC C/K 1995-96 CHEVROLET, GMC, OLDSMOBILE S/T This campaign bulletin, minus your assigned VIN listing, is being forwarded to you at this time in order to take care of those customers who bring their vehicle in for a malfunctioning windshield wiper motor prior to their notification of this campaign. GM probably will not begin notifying owners of this campaign until November, 1998. That is when parts are expected to be available in sufficient quantities to support this campaign. A VIN listing will be sent to dealers at that time. In the meantime, should an owner bring in a 1994-96 C/K or a 1995-96 S/T vehicle because the windshield wiper system exhibits the conditions described in the "Defect Involved" section of this bulletin, check the VIN against VISS to determine whether the vehicle is included in the campaign bulletin. ^ If it is included in the campaign population, repair the vehicle per this campaign bulletin, and charge the repair to the campaign using the campaign labor operation number, ^ If it is not included. but is still under warranty, repair the vehicle and submit a regular warranty claim. ^ If the vehicle is out of warranty and not included in the campaign population, treat as a customer-pay repair. Vehicles included in the campaign that are repaired before November, 1998, will be removed from the campaign prior to owner notification letters being mailed. The Highway Safety Act, as amended, provides that each vehicle which is subject to a recall campaign of this type must be adequately repaired within a reasonable time after the customer has tendered it for repair. A failure to repair within sixty (60) days after tender of a vehicle is prima facie evidence of failure to repair within a reasonable time If the condition is not adequately repaired within a reasonable time, the customer may be entitled to an identical or reasonably equivalent vehicle at no charge or to a refund of the purchase price less a reasonable allowance for depreciation. To avoid having to provide these burdensome remedies, every effort must be made to promptly schedule an appointment with each customer and to repair their vehicle as soon as possible. As you will see in reading the attached copy of the divisional letter that is being sent to customers, the customers are being instructed to contact the appropriate Customer Assistance Center if their dealer does not remedy the condition within five (5) days of the mutually agreed upon service date. If the condition is not remedied within a reasonable time, they are instructed on how to contact the National Highway Traffic Safety Administration. Defect Involved General Motors has decided that a defect which relates to motor vehicle safety exists in certain 1994-96 Chevrolet and GMC C/K model vehicles, and 1995-96 Chevrolet, GMC, and Oldsmobile S/T model vehicles. These vehicles may exhibit a condition in which the windshield wiper motors may fail after a year or more of vehicle operation. These failures are the result of cracked solder joints on the controller circuit board near the wiring harness connector. Depending on which solder joints crack or the severity of the crack, the windshield wipers could work intermittently or not at all. If this were to occur in a severe weather situation, driver visibility could be reduced, which could result in a vehicle crash without prior warning. To prevent the possibility of this condition occurring, dealers are to replace the wiper motor circuit board and cover. Vehicles Involved Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 98043 > Sep > 98 > Recall - Windshield Wiper Motor Failures > Page 13068 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 98043 > Sep > 98 > Recall - Windshield Wiper Motor Failures > Page 13069 Involved are certain 1994-96 Chevrolet and GMC C/K model vehicles, and 1995-96 Chevrolet, GMC, and Oldsmobile S/T model vehicles built within the VIN breakpoints as shown. Important: Dealers should confirm vehicle eligibility through VISS (Vehicle Information Service System) or ServiceNet (GMC only) prior to beginning campaign repairs. [Not all vehicles within the above breakpoints may be involved.] Computer listings containing the complete Vehicle Identification Number, customer name and address data will be supplied in November, 1998 when owner notification begins. Parts Information Parts required to complete this campaign are to be obtained from General Motors Service Parts Operations (GMSPO). Please refer to your "involved vehicles listing" prior to ordering requirements. Normal orders should be placed on a DRO = Daily Replenishment Order. An emergency requirement should be ordered on a CSO = Customer Special Order. Part Number Description Quantity/Vehicle 12463017 Windshield Washer Pulse Control Module 1 (consists of circuit board, cover, and screws) 12345739 Goodwrench RTV Silicone Sealant 1 (tube will service 50 vehicles Customer Notification Customers will be notified, in phases, of this campaign on their vehicles by General Motors beginning November, 1996. Dealer Campaign Responsibility All unsold new vehicles in dealers possession and subject to this campaign must be held and inspected/repaired per the service procedure of this campaign bulletin before customers take possession of these vehicles. Dealers are to service all vehicles subject to this campaign at no charge to customers, regardless of mileage age of vehicle, or ownership from this time forward. In summary, whenever a vehicle subject to this campaign enters your vehicle inventory, or is in your dealership for service in the future, please take the steps necessary to be sure the campaign correction has been made before selling or releasing the vehicle. Service Procedure 1. Turn the ignition key to the OFF position. 2. Remove the Connector Position Assurance (CPA) and disconnect the wiper motor electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 98043 > Sep > 98 > Recall - Windshield Wiper Motor Failures > Page 13070 3. Remove the three (3) screws that secure the cover to the wiper motor and remove the cover (Figure 1). 4. Inspect for sealant on the inside of the cover and then discard the cover and screws IMPORTANT: If sealant was found on the old cover, it will be necessary to remove any old sealant from the motor housing in step 6. 5. Carefully remove the module (circuit board) from the wiper motor by lifting up on the end of the module electrical connector. 6. If necessary, remove any old sealant from the wiper motor housing (see step 4). NOTICE: When handling the new module in the next step, be careful not to damage or bend the electrical contacts on the bottom side of the module. 7. Install the module into the wiper motor housing, making sure that the module is fully seated. When fully seated, the edges of the module circuit board will be flush (even) with the motor housing along all sides. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 98043 > Sep > 98 > Recall - Windshield Wiper Motor Failures > Page 13071 8. Carefully apply a bead of silicone sealant P/N 12345739 (or GE-162 sealant or equivalent) in the groove of the NEW cover (Figure 2). Remove any excess sealant that is outside of the groove. IMPORTANT: Only apply enough sealant to fill the groove in the cover. 9. Install the new cover on the wiper motor housing and install the three (3) new screws. Tighten the screws to 2.6 Nm (23 lbs. in.). 10. Reconnect the wiper motor electrical connector to the wiper motor assembly and install the CPA. 11. Turn the ignition key to the "ON" position and check wiper system for proper operation (delay/low/high (etc.). 12. Install the GM Campaign Identification label. Campaign Identification Label Each vehicle corrected in accordance with the instructions outlined in this Product Campaign Bulletin will require a "Campaign Identification Label". Each label provides a space to include the campaign number and the five (5) digit dealer code of the dealer performing the campaign service, This information may be inserted with a typewriter or a ball point pen. Each "Campaign Identification Label" is to be located on the radiator core support in an area which will be visible when the vehicle is brought in by the customer for periodic servicing. When installing the Campaign Identification Label, be sure to pull the tab to allow adhesion of the clear protective covering. Additional Campaign Identification Labels can be obtained from VISPAC Incorporated by calling 1-800-269-5100 (Monday-Friday, 8:00 a.m. to 430 p.m. EST). Ask for item number S-1015 when ordering. Apply the "Campaign Identification Label" only on a clean, dry surface. Claim Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > Recalls for Wiper Motor: > 98043 > Sep > 98 > Recall - Windshield Wiper Motor Failures > Page 13072 Submit a Product Campaign Claim with the information indicated. Reimbursement When a customer requests reimbursement, they must provide the following: - Proof of ownership at time of repair. - Original paid receipt confirming the amount of unreimbursed repair expense(s), a description of the repair, and the person or entity performing the repair. Claims for customer reimbursement on previously paid repairs are to be submitted as required by WINS. IMPORTANT:: Refer to the appropriate divisional service policies and procedures manual, section 1.6.2, for specific procedures regarding customer reimbursement verification. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 03023 > May > 03 > Recall - Windshield Wiper Motor failure Technical Service Bulletin # 03023 Date: 030501 Recall - Windshield Wiper Motor failure File In Section: Product Recalls Bulletin No.: 03023 Date: May, 2003 PRODUCT SAFETY RECALL SUBJECT: 03023 - WINDSHIELD WIPER MOTOR FAILURE MODELS: 1994 CHEVROLET CK PICKUP, TAHOE 4WD, SUBURBAN 2WD 1995 CHEVROLET CK PICKUP, CK CREW CAB 4WD, TAHOE 4WD, SUBURBAN, ASTRO VAN 1996 CHEVROLET BLAZER, S10, CK PICKUP, CK CREW CAB, TAHOE, SUBURBAN, ASTRO VAN, 1997 CHEVROLET S10 2WD, CK CREW CAB, SUBURBAN 4WD, ASTRO VAN 1994 GMC SIERRA PICKUP, YUKON 4WD, SUBURBAN 2WD 1995 GMC SIERRA PICKUP, SIERRA CREW CAB 4WD, YUKON 4WD, SUBURBAN, SAFARI VAN 1996 GMC SONOMA, JIMMY, SIERRA PICKUP, SIERRA CREW CAB, YUKON, SUBURBAN, SAFARI VAN 1997 GMC SONOMA 2WD, SIERRA CREW CAB, SUBURBAN 4WD, SAFARI VAN 1996 OLDSMOBILE BRAVADA This recall bulletin, minus your assigned VIN listing, is being sent to you at this time in order to take care of those customers who bring their vehicle in for a malfunctioning windshield wiper motor prior to their notification of this recall. GM plans to begin notifying owners of this recall in late June 2003. That is when parts are expected to be available in sufficient quantities to support this recall. A VIN listing will be sent to dealers at that time. In the meantime, should an owner bring in one of the vehicles listed above because the windshield wiper system exhibits the conditions described in the "Condition" paragraph contained in this bulletin, check the VIN in GMVIS to determine vehicle eligibility. If the vehicle is eligible, perform service correction and submit the claim as instructed in this bulletin. CONDITION General Motors has decided that a defect, which relates to motor vehicle safety, exists in certain 1994 Chevrolet CK Pickup, Tahoe, Suburban; 1995 Chevrolet CK Pickup, CK Crew Cab, Tahoe, Suburban, Astro Van; 1996 Chevrolet Blazer, S10 Pickup, CK Pickup, CK Crew Cab. Tahoe, Suburban, Astro Van; 1997 Chevrolet S10 Pickup, CK Crew Cab, Suburban 4WD, Astro Van; 1994 GMC Sierra Pickup, Yukon, Suburban; 1995 GMC Sierra Pickup, Sierra Crew Cab, Yukon, Suburban. Safari Van; 1996 GMC Sonoma, Jimmy, Sierra Pickup, Sierra Crew Cab, Yukon, Suburban, Safari Van; 1997 GMC Sonoma, Sierra Crew Cab, Suburban 4WD, Safari Van; 1996 Oldsmobile Bravada vehicles. These vehicles may have a condition in which the windshield wiper motor may fail. These failures are the result of cracked solder joints on the controller circuit board near the wiring harness connector. Depending on which solder joints crack or the severity of the crack, the windshield wipers could work intermittently or not at all. If this were to occur in a severe weather situation, driver visibility could be reduced, which could result in a vehicle crash without prior warning. CORRECTION Dealers are to replace the wiper motor circuit board and cover. VEHICLES INVOLVED Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 03023 > May > 03 > Recall - Windshield Wiper Motor failure > Page 13078 Involved are certain 1994 Chevrolet CK Pickup, Tahoe 4WD, Suburban 2WD; 1995 Chevrolet CK Pickup, CK Crew Cab 4WD, Tahoe 4WD, Suburban, Astro Van; 1996 Chevrolet Blazer, S10, CK Pickup, CK Crew Cab, Tahoe, Suburban, Astro Van; 1997 Chevrolet S10, 2WD, CK Crew Cab, Suburban 4WD, Astro Van; 1994 GMC Sierra Pickup, Yukon 4WD, Suburban 2WD; 1995 GMC Sierra Pickup, Sierra Crew Cab 4WD, Yukon 4WD, Suburban, Safari Van; 1996 GMC Sonoma, Jimmy, Sierra Pickup, Sierra Crew Cab, Yukon, Suburban, Safari Van; 1997 GMC Sonoma 2WD, Sierra Crew Cab, Suburban 4WD, Safari Van; 1996 Oldsmobile Bravada vehicles built within the VIN breakpoints shown. IMPORTANT: Dealers should confirm vehicle eligibility through GMVIS (GM Vehicle Inquiry System) before beginning recall repairs. [Not all vehicles within the Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 03023 > May > 03 > Recall - Windshield Wiper Motor failure > Page 13079 above breakpoints may be involved.] Involved vehicles have been identified by Vehicle Identification Number. Computer listings containing the complete Vehicle Identification Number, customer name and address data have been prepared, and are being furnished to involved dealers with the recall bulletin. The customer name and address data will enable dealers to follow up with customers involved in this recall. Any dealer not receiving a computer listing with the recall bulletin has no involved vehicles currently assigned. These dealer listings may contain customer names and addresses obtained from Motor Vehicle Registration Records. The use of such motor vehicle registration data for any other purpose is a violation of law in several states/provinces/countries. Accordingly, you are urged to limit the use of this listing to the follow-up necessary to complete this recall. PARTS INFORMATION Parts required to complete this recall are to be obtained from General Motors Service Parts Operations (GMSPO). Please refer to your "involved vehicles listing" before ordering parts. Normal orders should be placed on a DRO = Daily Replenishment Order. In an emergency situation, parts should be ordered on a CSO = Customer Special Order. RECALL IDENTIFICATION LABEL Place a Recall Identification Label on each vehicle corrected in accordance with the instructions outlined in this Product Recall Bulletin Each label provides a space to include the recall number and the five (5) digit dealer code of the dealer performing the recall service. This information may be inserted with a typewriter or a ballpoint pen. Put the Recall Identification Label on a clean and dry surface of the radiator core support in an area that will be visible to people servicing the vehicle. When installing the Recall Identification Label, be sure to pull the tab to allow adhesion of the clear protective covering. Additional Recall Identification Labels can be obtained from Dealer Support Materials by either ordering on the web from DWD Store. CUSTOMER REIMBURSEMENT All customer requests for reimbursement for previous repairs for the recall condition will be handled by the Customer Assistance Center, not by dealers. A General Motors Product Recall Customer Reimbursement Procedure Form is included with the original customer letter. IMPORTANT: Refer to the GM Service Policies and Procedures Manual, section 61.12, for specific procedures regarding customer reimbursement and the form. CLAIM INFORMATION Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 03023 > May > 03 > Recall - Windshield Wiper Motor failure > Page 13080 Submit a Product Recall Claim with the information shown. Refer to the General Motors WINS Claims Processing Manual for details on Product Recall Claim Submission. CUSTOMER NOTIFICATION Customers will be notified of this recall on their vehicles by General Motors (see copy of customer letter shown in this bulletin). DEALER RECALL RESPONSIBILITY The US National Traffic and Motor Vehicle Safety Act provides that each vehicle that is subject to a recall of this type must be adequately repaired within a reasonable time after the customer has tendered it for repair. A failure to repair within sixty days after tender of a vehicle is prima facie evidence of failure to repair within a reasonable time. If the condition is not adequately repaired within a reasonable time, the customer may be entitled to an identical or reasonably equivalent vehicle at no charge or to a refund of the purchase price less a reasonable allowance for depreciation. To avoid having to provide these burdensome remedies, every effort must be made to promptly schedule an appointment with each customer and to repair their vehicle as soon as possible. In the recall notification letters, customers are told how to contact the US National Highway Traffic Safety Administration if the recall is not completed within a reasonable time. All unsold new vehicles in dealers' possession and subject to this recall must be held and inspected/repaired per the service procedure of this recall bulletin before customers take possession of these vehicles. Dealers are to service all vehicles subject to this recall at no charge to customers, regardless of mileage, age of vehicle, or ownership, from this time forward. Customers who have recently purchased vehicles sold from your vehicle inventory, and for which there is no customer information indicated on the dealer listing, are to be contacted by the dealer. Arrangements are to be made to make the required correction according to the instructions contained in this bulletin. This could be done by mailing to such customers, a copy of the customer letter shown in this bulletin. Recall follow-up cards should not be used for this purpose, since the customer may not as yet have received the notification letter. In summary, whenever a vehicle subject to this recall enters your vehicle inventory, or is in your dealership for service in the future, you must take the steps necessary to be sure the recall correction has been made before selling or releasing the vehicle. Disclaimer Service Procedure 1. Turn the ignition key to the OFF position. 2. Remove the Connector Position Assurance (CPA) and disconnect the wiper motor electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 03023 > May > 03 > Recall - Windshield Wiper Motor failure > Page 13081 3. Remove the three screws that secure the cover to the wiper motor and remove the cover. 4. Inspect for sealant on the inside of the cover and then discard the cover and screws. Important If sealant was found on the old cover, it will be necessary to remove any old sealant from the motor housing in step 6. 5. Carefully remove the module (circuit board) from the wiper motor by lifting up on the end of the module electrical connector. 6. If necessary, remove any old sealant from the wiper motor housing (see step 4). Notice When handling the new module in the next step, be careful not to damage or bend the electrical contacts on the bottom side of the module. 7. Install the module into the wiper motor housing, making sure that the module is fully seated. When fully seated, the edges of the module circuit board will be flush (even) with the motor housing along all sides. 8. Carefully apply a bead of silicone sealant, P/N 12345739 (or GE-162 sealant or equivalent) in the groove of the NEW cover (Figure 2). Remove any excess sealant that is outside of the groove. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 03023 > May > 03 > Recall - Windshield Wiper Motor failure > Page 13082 Important Only apply enough sealant to fill the groove in the cover. 9. Install the new cover on the wiper motor housing and install the three new screws. Tighten Tighten the screws to 2.6 Nm (23 lb in). 10. Reconnect the wiper motor electrical connector to the wiper motor assembly and install the CPA. 11. Turn the ignition key to the ON position and check the wiper system for proper operation (delay/low/high/etc.). 12. Install the GM Recall Identification Label. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 03023 > May > 03 > Recall - Windshield Wiper Motor failure > Page 13083 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > NHTSA03V159000 > Apr > 03 > Recall 03V159000: Wiper Motor Circuit Board Defect Wiper Motor: All Technical Service Bulletins Recall 03V159000: Wiper Motor Circuit Board Defect DEFECT: On certain minivans, pickup trucks, and sport utility vehicles with certain model-engine combinations, the windshield wiper motor may fail due to cracked solder joints on the controller circuit board. The windshield wipers could work intermittently or not at all. If this were to occur during bad weather, driver visibility would be reduced, which could result in a crash. REMEDY: Dealers will replace the wiper motor circuit board and cover. The manufacturer has reported that owner notification is expected to begin during late June 2003. Owners may contact Chevrolet at 1-800-222-1020, GMC at 1-800-462-8782, or Oldsmobile at 1-800-442-6537. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 02054 > Feb > 03 > Campaign - Winshield Wiper Motor Failure Technical Service Bulletin # 02054 Date: 030201 Campaign - Winshield Wiper Motor Failure File In Section: 08-Body & Access. Bulletin No.: 02054 Date: February, 2003 SPECIAL POLICY SUBJECT: 02054 - SPECIAL POLICY ADJUSTMENT - WINDSHIELD WIPER MOTOR FAILURES MODELS: 1997 CHEVROLET BLAZER, S10 1995-1997 CHEVROLET ASTRO, C/K CREW CAB 1994-1997 C/K PICKUP, TAHOE, SUBURBAN 1997 GMC JIMMY, SONOMA 1995-1997 GMC SAFARI, SIERRA CREW CAB 1994-1997 GMC SIERRA PICKUP, YUKON, SUBURBAN 1997 OLDSMOBILE BRAVADA (EXCLUDING VEHICLES INVOLVED IN RECALL 98043) CONDITION Some customers of 1997 Chevrolet Blazer, S10 Pickup; 1995-1997 Chevrolet Astro, C/K Crew Cab; 1994-1997 C/K Pickup, Tahoe, Suburban; 1997 GMC Jimmy, Sonoma; 1995-1997 GMC Safari, Sierra Crew Cab; 1994-1997 GMC Sierra Pickup, Yukon, Suburban; and 1997 Oldsmobile Bravada vehicles not involved in recall 98043 may experience a windshield wiper failure due to cracked solder joints on the controller circuit board. SPECIAL POLICY ADJUSTMENT This special policy covers the condition described above for a period of 7 years or 70,000 miles (112,000 km), whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership, or for those vehicles currently outside of this coverage, until February 29, 2004. The repairs will be made at no charge to the customer. For vehicles covered by Vehicle Service Contracts, all eligible claims with repair orders on or after February 21, 2003 are covered by this special policy and must be submitted using the labor operation codes provided with this bulletin. Claims with repair orders prior to February 21, 2003 must be submitted to the Service Contract provider. VEHICLES INVOLVED Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 02054 > Feb > 03 > Campaign - Winshield Wiper Motor Failure > Page 13092 Involved are certain 1997 Chevrolet Blazer, 510 Pickup; 1995-1997 Chevrolet Astro, C/K Crew Cab; 1994-1997 C/K Pickup, Tahoe, Suburban; 1997 GMC Jimmy, Sonoma; 1995-1997 GMC Safari, Sierra Crew Cab; 1994-1997 GMC Sierra Pickup, Yukon, Suburban; and 1997 Oldsmobile Bravada vehicles not covered by recall 98043 and built within the VIN breakpoints shown. PARTS INFORMATION Parts required to complete this special policy are to be obtained from General Motors Service Parts Operations (GMPSO). Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 02054 > Feb > 03 > Campaign - Winshield Wiper Motor Failure > Page 13093 CUSTOMER NOTIFICATION Customers will be notified of this special policy on their vehicles by General Motors (see copy of typical customer letter included with this bulletin - actual divisional letter may vary slightly). SERVICE PROCEDURE 1. Turn the ignition key to the OFF position. 2. Remove the Connector Position Assurance (CPA) and disconnect the wiper motor electrical connector. 3. Remove the three screws that secure the cover to the wiper motor and remove the cover. 4. Inspect for sealant on the inside of the cover and then discard the cover and screws. Important If sealant was found on the old cover, it will be necessary to remove any old sealant from the motor housing in step 6. 5. Carefully remove the module (circuit board) from the wiper motor by lifting up on the end of the module electrical connector. 6. If necessary, remove any old sealant from the wiper motor housing (see step 4). Notice When handling the new module in the next step, be careful not to damage or bend the electrical contacts on the bottom side of the module. 7. Install the module into the wiper motor housing, making sure that the module is fully seated. When fully seated, the edges of the module circuit board will be flush (even) with the motor housing along all sides. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 02054 > Feb > 03 > Campaign - Winshield Wiper Motor Failure > Page 13094 8. Carefully apply a bead of silicone sealant, P/N 12345739 (or GE-162 sealant or equivalent) in the groove of the NEW cover (Figure 2). Remove any excess sealant that is outside of the groove. Important Only apply enough sealant to fill the groove in the cover. 9. Install the new cover on the wiper motor housing and install the three new screws. Tighten the screws to 2.6 Nm (23 lb in). 10. Reconnect the wiper motor electrical connector to the wiper motor assembly and install the CPA. 11. Turn the ignition key to the ON position and check the wiper system for proper operation (delay/low/high/etc.). CLAIM INFORMATION For vehicles repaired under the terms of this special policy, submit a claim with the information indicated. CUSTOMER REIMBURSEMENT Customer requests for reimbursement of previously paid repairs to correct a failed wiper motor are to be submitted prior to or by February 29, 2004 (this time limitation may be longer depending upon the law in your state/province/country). Repairs must have occurred before March 14, 2003. When a customer requests reimbursement, they must provide the following: - Proof of ownership at time of repair. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 02054 > Feb > 03 > Campaign - Winshield Wiper Motor Failure > Page 13095 - Original paid receipt confirming the amount of unreimbursed repair expense(s) (including Service Contract deductibles), a description of the repair, and the person or entity performing the repair. Customers from the States of California, Connecticut, Virginia, and Wisconsin must submit requests for reimbursement directly to the applicable Division per instructions in the owner letter. If the work was done by someone other than a GM dealership, the amount of reimbursement will be limited to the amount that the repair would have cost GM to have it completed by a GM dealership. Disclaimer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 02054 > Feb > 03 > Campaign - Winshield Wiper Motor Failure > Page 13096 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 02054 > Feb > 03 > Campaign - Winshield Wiper Motor Failure > Page 13097 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 98043 > Sep > 98 > Recall - Windshield Wiper Motor Failures Technical Service Bulletin # 98043 Date: 980901 Recall - Windshield Wiper Motor Failures File In Section: Product Campaigns Bulletin No.: 98043 Date: September, 1998 PRODUCT RECALL CAMPAIGN PRODUCT SAFETY CAMPAIGN SUBJECT: 96043 - WINDSHIELD WIPER MOTOR FAILURES MODELS: 1994-96 CHEVROLET AND GMC C/K 1995-96 CHEVROLET, GMC, OLDSMOBILE S/T This campaign bulletin, minus your assigned VIN listing, is being forwarded to you at this time in order to take care of those customers who bring their vehicle in for a malfunctioning windshield wiper motor prior to their notification of this campaign. GM probably will not begin notifying owners of this campaign until November, 1998. That is when parts are expected to be available in sufficient quantities to support this campaign. A VIN listing will be sent to dealers at that time. In the meantime, should an owner bring in a 1994-96 C/K or a 1995-96 S/T vehicle because the windshield wiper system exhibits the conditions described in the "Defect Involved" section of this bulletin, check the VIN against VISS to determine whether the vehicle is included in the campaign bulletin. ^ If it is included in the campaign population, repair the vehicle per this campaign bulletin, and charge the repair to the campaign using the campaign labor operation number, ^ If it is not included. but is still under warranty, repair the vehicle and submit a regular warranty claim. ^ If the vehicle is out of warranty and not included in the campaign population, treat as a customer-pay repair. Vehicles included in the campaign that are repaired before November, 1998, will be removed from the campaign prior to owner notification letters being mailed. The Highway Safety Act, as amended, provides that each vehicle which is subject to a recall campaign of this type must be adequately repaired within a reasonable time after the customer has tendered it for repair. A failure to repair within sixty (60) days after tender of a vehicle is prima facie evidence of failure to repair within a reasonable time If the condition is not adequately repaired within a reasonable time, the customer may be entitled to an identical or reasonably equivalent vehicle at no charge or to a refund of the purchase price less a reasonable allowance for depreciation. To avoid having to provide these burdensome remedies, every effort must be made to promptly schedule an appointment with each customer and to repair their vehicle as soon as possible. As you will see in reading the attached copy of the divisional letter that is being sent to customers, the customers are being instructed to contact the appropriate Customer Assistance Center if their dealer does not remedy the condition within five (5) days of the mutually agreed upon service date. If the condition is not remedied within a reasonable time, they are instructed on how to contact the National Highway Traffic Safety Administration. Defect Involved General Motors has decided that a defect which relates to motor vehicle safety exists in certain 1994-96 Chevrolet and GMC C/K model vehicles, and 1995-96 Chevrolet, GMC, and Oldsmobile S/T model vehicles. These vehicles may exhibit a condition in which the windshield wiper motors may fail after a year or more of vehicle operation. These failures are the result of cracked solder joints on the controller circuit board near the wiring harness connector. Depending on which solder joints crack or the severity of the crack, the windshield wipers could work intermittently or not at all. If this were to occur in a severe weather situation, driver visibility could be reduced, which could result in a vehicle crash without prior warning. To prevent the possibility of this condition occurring, dealers are to replace the wiper motor circuit board and cover. Vehicles Involved Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 98043 > Sep > 98 > Recall - Windshield Wiper Motor Failures > Page 13102 Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 98043 > Sep > 98 > Recall - Windshield Wiper Motor Failures > Page 13103 Involved are certain 1994-96 Chevrolet and GMC C/K model vehicles, and 1995-96 Chevrolet, GMC, and Oldsmobile S/T model vehicles built within the VIN breakpoints as shown. Important: Dealers should confirm vehicle eligibility through VISS (Vehicle Information Service System) or ServiceNet (GMC only) prior to beginning campaign repairs. [Not all vehicles within the above breakpoints may be involved.] Computer listings containing the complete Vehicle Identification Number, customer name and address data will be supplied in November, 1998 when owner notification begins. Parts Information Parts required to complete this campaign are to be obtained from General Motors Service Parts Operations (GMSPO). Please refer to your "involved vehicles listing" prior to ordering requirements. Normal orders should be placed on a DRO = Daily Replenishment Order. An emergency requirement should be ordered on a CSO = Customer Special Order. Part Number Description Quantity/Vehicle 12463017 Windshield Washer Pulse Control Module 1 (consists of circuit board, cover, and screws) 12345739 Goodwrench RTV Silicone Sealant 1 (tube will service 50 vehicles Customer Notification Customers will be notified, in phases, of this campaign on their vehicles by General Motors beginning November, 1996. Dealer Campaign Responsibility All unsold new vehicles in dealers possession and subject to this campaign must be held and inspected/repaired per the service procedure of this campaign bulletin before customers take possession of these vehicles. Dealers are to service all vehicles subject to this campaign at no charge to customers, regardless of mileage age of vehicle, or ownership from this time forward. In summary, whenever a vehicle subject to this campaign enters your vehicle inventory, or is in your dealership for service in the future, please take the steps necessary to be sure the campaign correction has been made before selling or releasing the vehicle. Service Procedure 1. Turn the ignition key to the OFF position. 2. Remove the Connector Position Assurance (CPA) and disconnect the wiper motor electrical connector. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 98043 > Sep > 98 > Recall - Windshield Wiper Motor Failures > Page 13104 3. Remove the three (3) screws that secure the cover to the wiper motor and remove the cover (Figure 1). 4. Inspect for sealant on the inside of the cover and then discard the cover and screws IMPORTANT: If sealant was found on the old cover, it will be necessary to remove any old sealant from the motor housing in step 6. 5. Carefully remove the module (circuit board) from the wiper motor by lifting up on the end of the module electrical connector. 6. If necessary, remove any old sealant from the wiper motor housing (see step 4). NOTICE: When handling the new module in the next step, be careful not to damage or bend the electrical contacts on the bottom side of the module. 7. Install the module into the wiper motor housing, making sure that the module is fully seated. When fully seated, the edges of the module circuit board will be flush (even) with the motor housing along all sides. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 98043 > Sep > 98 > Recall - Windshield Wiper Motor Failures > Page 13105 8. Carefully apply a bead of silicone sealant P/N 12345739 (or GE-162 sealant or equivalent) in the groove of the NEW cover (Figure 2). Remove any excess sealant that is outside of the groove. IMPORTANT: Only apply enough sealant to fill the groove in the cover. 9. Install the new cover on the wiper motor housing and install the three (3) new screws. Tighten the screws to 2.6 Nm (23 lbs. in.). 10. Reconnect the wiper motor electrical connector to the wiper motor assembly and install the CPA. 11. Turn the ignition key to the "ON" position and check wiper system for proper operation (delay/low/high (etc.). 12. Install the GM Campaign Identification label. Campaign Identification Label Each vehicle corrected in accordance with the instructions outlined in this Product Campaign Bulletin will require a "Campaign Identification Label". Each label provides a space to include the campaign number and the five (5) digit dealer code of the dealer performing the campaign service, This information may be inserted with a typewriter or a ball point pen. Each "Campaign Identification Label" is to be located on the radiator core support in an area which will be visible when the vehicle is brought in by the customer for periodic servicing. When installing the Campaign Identification Label, be sure to pull the tab to allow adhesion of the clear protective covering. Additional Campaign Identification Labels can be obtained from VISPAC Incorporated by calling 1-800-269-5100 (Monday-Friday, 8:00 a.m. to 430 p.m. EST). Ask for item number S-1015 when ordering. Apply the "Campaign Identification Label" only on a clean, dry surface. Claim Information Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Technical Service Bulletins > All Technical Service Bulletins for Wiper Motor: > 98043 > Sep > 98 > Recall - Windshield Wiper Motor Failures > Page 13106 Submit a Product Campaign Claim with the information indicated. Reimbursement When a customer requests reimbursement, they must provide the following: - Proof of ownership at time of repair. - Original paid receipt confirming the amount of unreimbursed repair expense(s), a description of the repair, and the person or entity performing the repair. Claims for customer reimbursement on previously paid repairs are to be submitted as required by WINS. IMPORTANT:: Refer to the appropriate divisional service policies and procedures manual, section 1.6.2, for specific procedures regarding customer reimbursement verification. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Locations > Wiper Motor, Front Cruise Control Module Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Locations > Wiper Motor, Front > Page 13109 Rear Wiper/Washer Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Locations > Page 13110 Windshield Wiper Motor Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Motor > Component Information > Locations > Page 13111 Wiper Motor: Service and Repair 1. Disconnect battery ground cable. 2. Remove wiper arm assemblies. 3. Remove cowl vent grille. 4. Disconnect wiring harness connector from wiper motor. 5. Remove drive link sockets from the motor crank arm. Do not remove crank arm. Loosen nuts and slide brackets off crank arm. 6. Remove wiper bolts and motor from vehicle. 7. Reverse procedure to install. Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Switch > Component Information > Locations > Rear Window Wiper & Washer Switch Cargo Lamp Switch Wiring Chevrolet C Tahoe 2wd Workshop Manual (V8-5.7L VIN R (1996)) Chevrolet Workshop Manuals > Wiper and Washer Systems > Wiper Switch > Component Information > Locations > Rear Window Wiper & Washer Switch > Page 13116 Wiper Switch: Locations Windshield Wiper/Washer Switch At Steering Column, part of Turn Signal Lever